阅读说明：本技术 用于系统间切换的技术 (Techniques for inter-system handover ) 是由 A.森通扎 P.施利瓦-贝特林 P.黑德曼 于 2017-11-29 设计创作，主要内容包括：描述一种用于选择性地发起从包括第一核心网络CN(512)和第一无线电接入网RAN(516)的源系统(510)到包括第二CN(532)和第二RAN(536)的目标系统(530)的切换的技术。关于本技术的方法方面,确定用于切换的控制平面接口(520)在第一CN(512)与第二CN(532)之间是否可用。根据控制平面接口(520)的可用性,选择性地发起切换。(A technique for selectively initiating a handover from a source system (510) comprising a first core network, CN, (512) and a first radio access network, RAN, (516) to a target system (530) comprising a second CN (532) and a second RAN (536) is described. With respect to a method aspect of the present technique, it is determined whether a control plane interface (520) for handover is available between a first CN (512) and a second CN (532). The handover is selectively initiated based on the availability of the control plane interface (520).)

1. A method (300; 400) of selectively initiating a handover from a source system (510) comprising a first core network, CN, (512) and a first radio access network, RAN, (516) to a target system (530) comprising a second CN (532) and a second RAN (536), the method comprising or triggering:

determining (302; 404) whether a control plane interface (520) for the handover is available between the first CN (512) and the second CN (532); and

selectively initiating (306; 406) the handover in accordance with the availability of the control plane interface (520).

2. The method of claim 1, wherein the control plane interface (520) is to or is required to connect a node (514) of the first CN (512) with a node (534) of the second CN (532) for the handover.

3. The method of claim 1 or 2, wherein the control plane interface (520) is to or is required to connect a first mobility entity (514) of the first CN (512) with a second mobility entity (534) of the second CN (532).

4. The method of claim 3, wherein at least one of the first mobility entity (514) and the second mobility entity (534) comprises at least one of a mobility management entity, MME, and an access mobility function, AMF.

5. The method according to any of claims 1 to 4, wherein at least one of the source system (510) and the target system (530) comprises at least one of an Evolved Packet System (EPS) and a Next Generation System (NGS) or a fifth Generation System (5 GS).

6. The method of any of claims 1 to 5, wherein initiating the handover comprises or is required to comprise: sending a handover message indicating a handover request from the first CN (512) to the second CN (532) over the control plane interface (520).

7. The method of claim 6, wherein the first RAN (516) is in a connected mode with a radio (540), and the handover message indicates a context of the radio (540).

8. The method of any of claims 1 to 7, performed by the first CN (512) or a node (514) of the first CN (512).

9. The method of any of claims 1 to 8, performed by the first RAN (516) or a node (518) of the first RAN (516).

10. The method of any of claims 1 to 9, wherein determining (302) the availability of the control plane interface (520) comprises: sending (304) an availability message (610) to the first RAN (516) indicating the availability.

11. The method according to any of claims 1 to 10, wherein determining (404) the availability of the control plane interface (520) comprises receiving (402) an availability message (610) indicating the availability from the first CN (512).

12. The method of claim 10 or 11, wherein the availability message (610) comprises: a switching restriction list indicating the availability.

13. The method according to any of claims 10 to 12, wherein the availability message (610) is sent to at least one base station (518) of the first RAN (516), and/or wherein the availability message (610) is received from at least one mobility entity (514) of the first CN (512).

14. The method according to any of claims 10 to 13, wherein the availability message (610) is sent and/or received when configuring a RAN interface between the first CN (512) and the first RAN (516) or a base station of the first RAN (516).

15. The method of any of claims 10 to 14, wherein the availability message (610) configures at least one of the first RAN (516) or one or more base stations of the first RAN (516) to selectively send a handover required message indicating the target system (530) or the second RAN (536) according to the availability of the control plane interface (520).

16. The method of any of claims 10 to 15, wherein the availability is determined for a plurality of the target systems (530), and wherein the availability message (610) indicates the availability for the plurality of the target systems (530).

17. The method of any of claims 1 to 16, wherein the first RAN (516) is configured for radio access according to a first radio access technology, RAT, (519) and the second RAN (536) is configured for radio access according to a second RAT (539).

18. The method of claim 17, wherein the second RAT (539) is different from the first RAT (519).

19. The method of claim 17 or 18, wherein the availability is determined for one or more target systems (530) configured for radio access in accordance with the second RAT (539).

20. The method of claim 19 and any of embodiments 10 to 16, wherein the availability message (610) indicates the availability of the second RAT (539).

21. The method of any of claims 17 to 20, wherein at least one of the first RAT (519) and the second RAT (539) comprises at least one of a 3GPP long term evolution and a 3GPP 5G new air interface.

22. The method of any of claims 1 to 21, wherein the data plane of the first CN (512) and the data plane of the second CN (532) comprise or are connected to the same gateway.

23. A computer program product comprising program code portions for performing the steps of any one of claims 1 to 22 when the computer program product is executed on one or more computing devices.

24. The computer program product of claim 23, stored on a computer-readable recording medium (906).

25. An apparatus (100; 200) for selectively initiating a handover from a source system (510) comprising a first core network, CN, (512) and a first radio access network, RAN, (516) to a target system (530) comprising a second CN (532) and a second RAN (536), the apparatus being configured to trigger or perform the steps of:

determining whether a control plane interface (520) for the handover is available between the first CN (512) and the second CN (532); and

selectively initiate the handover in accordance with the availability of the control plane interface (520).

26. The apparatus of claim 25, further configured to trigger or perform the steps of any one of claims 2 to 22.

27. An apparatus (100; 200) for selectively initiating a handover from a source system (510) comprising a first core network, CN, (512) and a first radio access network, RAN, (516) to a target system (530) comprising a second CN (532) and a second RAN (536), the apparatus (100; 200) comprising at least one processor (904) and a memory (906), the memory comprising instructions executable by the at least one processor (904), whereby the apparatus (100; 200) is operable to:

determining whether a control plane interface (520) of the handover is available between the first CN (512) and the second CN (532); and

selectively initiate the handover in accordance with the availability of the control plane interface (520).

28. The apparatus of claim 27, further operable to perform the steps of any of claims 2 to 22.

29. An apparatus (100; 200) for selectively initiating a handover from a source system (510) comprising a first core network, CN, (512) and a first radio access network, RAN, (516) to a target system (530) comprising a second CN (532) and a second RAN (536), the apparatus comprising:

a determining module (102; 204) for determining whether a control plane interface (520) for the handover is available between the first CN (512) and the second CN (532); and

a selective initiation module (106; 206) for selectively initiating the handover in dependence of the availability of the control plane interface (520).

30. The apparatus of claim 29, further comprising means for performing the steps of any of claims 2 to 22.

Technical Field

The present disclosure relates to a technique for selectively initiating a handover (handover) from a source system to a target system. More particularly, and not by way of limitation, methods and apparatus are provided for selectively initiating a core network handover.

Background

Mobile telecommunications systems, such as the third generation partnership project (3 GPP) Long Term Evolution (LTE), provide radio access to radio devices, such as user equipment or UEs, through base stations, such as evolved node bs (enbs). Mobility within a Radio Access Network (RAN), such as an evolved UMTS terrestrial radio access network (E-UTRAN), comprising a plurality of base stations can be handled by the RAN, for example by means of Radio Resource Control (RRC) signaling.

Inter-system handover is achieved for mobility between RANs of different telecommunication systems. For example, the document US 2007/0021120 a1 describes a handover between an LTE system and a UMTS system.

While the packet switched user plane of modern mobile telecommunications systems, such as 3GPP LTE, LTE-Advanced (LTE-a), LTE licensed assisted access (LTE-LAA) and 5G systems, can be easily coupled to a common gateway, there is no mechanism to prevent the source RAN of one system from attempting an inter-RAT handover to the target RAN of another system, even if no inter-system handover is implemented for both systems.

This will cause a failed handover attempt and an increased risk, namely: the radio leaves coverage (coverage) until the radio has reselected another base station or cell of the third system. Such degradation or disruption in network support impacts end user quality of experience (QoE).

Disclosure of Invention

Therefore, there is a need for a handover technique that is compatible with an interworking system. Alternatively or additionally, there is a need for inter-system handover techniques that reduce or prevent failed handover attempts.

In one aspect, a method of selectively initiating a handover is provided. The selectively initiated handover is from a source system comprising a first core network CN and a first radio access network RAN to a target system comprising a second CN and a second RAN. The method includes the step of determining whether a control plane interface for handover is available between the first CN and the second CN. The method also includes the step of selectively initiating a handover based on the availability of the control plane interface.

"determining" whether a control plane interface is "available" may include "determining" whether a control plane interface is "available". For example, the determining step may be implemented by determining whether a control plane interface for handover is unavailable between the first CN and the second CN.

"selective" in the initiation of the handover may not include initiating or performing the handover if the control plane interface is unavailable.

"handover" may relate to mobility in a Radio Resource Control (RRC) connected mode. The radio may be in RRC mode with the first RAN. The radio may be any device configured for radio communication with a first RAN and/or for measuring a second RAN.

The first CN and the second CN may be different. For example, at least the mobility entity of the first CN may be different from the mobility entity of the second CN.

Any features related to a CN or RAN (e.g., control plane interfaces between CNs, or messages from or to a first CN or a first RAN) may be implemented by features related to at least one node of the CN or RAN. Any steps performed or triggered by the CN or RAN may be implemented by steps performed or triggered by at least one node of the CN or RAN.

The method may be performed in a distributed manner by one or more nodes of the first CN, by one or more nodes of the first RAN, or by at least one node of the first CN and at least one node of the first RAN. The mobility entity (e.g., of the first CN) and/or the base station (e.g., of the first RAN) may perform the method. An example of the method may be performed by each base station of the first RAN.

The radio may be any device configured to access the first and second RANs. The radio may be a user equipment (UE, e.g., a 3GPP UE), a mobile or portable station (STA, e.g., a Wi-Fi STA), a device for Machine Type Communication (MTC), or a combination thereof. Examples of UEs and mobile stations include mobile phones and tablet computers. Examples of portable stations include laptop computers and televisions. Examples of MTC devices include robots, sensors and/or actuators, for example in manufacturing, automotive communication and home automation. MTC devices may be implemented in household appliances and consumer electronics devices. Examples of combinations include autonomous vehicles, door communication systems (door intercommunication systems), and automated teller machines.

Alternatively or additionally, any of the nodes of the first and second RANs may be embodied as a radio access node. Examples of radio access nodes may include base stations (e.g. 3G base stations or node bs, 4G base stations or enodebs or 5G base stations or gnodebs), access points (e.g. Wi-Fi access points) and network controllers (e.g. according to bluetooth, ZigBee or Z-Wave).

For example, the first RAN and/or the second RAN may provide radio access in accordance with global system for mobile communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), or new air interface (NR). The techniques may be implemented at a physical layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and/or a Radio Resource Control (RRC) layer of a protocol stack for radio access.

In another aspect, a computer program product is provided. The computer program product comprises program code portions for performing any of the steps of the method aspects disclosed herein when the computer program product is executed by one or more computing devices. The computer program product may be stored on a computer-readable recording medium. The computer program product may also be provided for downloading via a data network, for example in a source or target system, and/or via the internet. Alternatively or additionally, the method may be encoded in a Field Programmable Gate Array (FPGA) and/or an Application Specific Integrated Circuit (ASIC), or the functionality may be provided for downloading by means of a hardware description language.

In another aspect, an apparatus for selectively initiating a handover is provided. The selectively initiated handover is from a source system comprising a first core network CN and a first radio access network RAN to a target system comprising a second CN and a second RAN. The apparatus is configured to perform method aspects. Alternatively or additionally, the apparatus may include a determining unit configured to determine whether a control plane interface for handover is available between the first CN and the second CN. The apparatus may also include a selective initiation unit configured to selectively initiate a handover based on availability of the control plane interface.

In relation to a further apparatus aspect, an apparatus for selectively initiating a handover is provided. The selectively initiated handover is from a source system comprising a first core network CN and a first radio access network RAN to a target system comprising a second CN and a second RAN. The apparatus includes at least one processor and a memory. The memory comprises instructions executable by the at least one processor whereby the apparatus is operable to determine whether a control plane interface for handover is available between the first CN and the second CN. Execution of the instructions further causes the apparatus to be operable to selectively initiate a handover in accordance with availability of the control plane interface.

With respect to further aspects, an apparatus for selectively initiating a handover is provided. The selectively initiated handover is from a source system comprising a first core network CN and a first radio access network RAN to a target system comprising a second CN and a second RAN. The apparatus may include one or more modules for performing method aspects. Alternatively or additionally, the apparatus includes a determining unit for determining whether a control plane interface for handover is available between the first CN and the second CN. The apparatus also includes a selective initiation module for selectively initiating a handover based on availability of the control plane interface.

The apparatus may also include any feature disclosed herein in the context of a method aspect. In particular, any one of the units and modules or dedicated units or modules may be configured to perform or trigger one or more of the steps of the method aspect.

Drawings

Further details of embodiments of the present technology are described with reference to the accompanying drawings, in which:

FIG. 1 illustrates a schematic block diagram of an embodiment of an apparatus for selectively initiating an intersystem handover that may be implemented in a source core network;

fig. 2 illustrates a schematic block diagram of an embodiment of an apparatus for selectively initiating an inter-system handover that may be implemented in a source access network;

FIG. 3 illustrates a flow diagram of an embodiment of a method for selectively initiating an intersystem handover that may be implemented in a source core network;

fig. 4 illustrates a flow diagram of an embodiment of a method for selectively initiating an inter-system handover that may be implemented in a source access network;

FIG. 5 shows a schematic block diagram of an exemplary system environment for the technology;

fig. 6 shows a schematic signalling diagram resulting from a first implementation of the apparatus of fig. 1 and 2;

figure 7 shows a table of the structure of an availability message that may be used for the signalling of the first implementation of figure 6;

FIG. 8 shows a table of the structure of an availability message for a second implementation;

fig. 9 shows a schematic block diagram of an embodiment of an arrangement in a network node combinable with the embodiments and implementations of fig. 1 to 8; and

fig. 10 shows a schematic block diagram of an embodiment of an arrangement in a plurality of network nodes combinable with the embodiments and implementations of fig. 1 to 9.

Detailed Description

For purposes of explanation and not limitation, specific details are set forth in the following description, such as a particular network environment, in order to provide a thorough understanding of the techniques disclosed herein. It will be apparent to one skilled in the art that the present technology may be practiced in other embodiments that depart from these specific details. Furthermore, although the following embodiments are described primarily with respect to a 5G new air interface (NR) implementation, it will be readily apparent that the techniques described herein may also be implemented in any other radio network including 3GPP LTE or its successors (e.g., LTE-a or LTE-LAA), Wireless Local Area Networks (WLANs) according to the standard family IEEE 802.11, and/or ZigBee based on IEEE 802.15.4.

Furthermore, those skilled in the art will appreciate that the functions, steps, units and modules illustrated herein may be implemented using software functioning in conjunction with a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer including, for example, an Advanced RISC Machine (ARM). It will also be appreciated that while the following embodiments are primarily described in the context of methods and apparatus, the present invention may also be embodied in a computer program product as well as a system comprising at least one computer processor and a memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

Figure 1 schematically illustrates a block diagram of an embodiment of an apparatus for selectively initiating a handover from a source system comprising a first Core Network (CN) and a first Radio Access Network (RAN) to a target system comprising a second CN and a second RAN, the apparatus being generally referred to by reference numeral 100.

The apparatus 100 is configured to determine whether a control plane interface for handover is available between the first CN and the second CN. The apparatus 100 is further configured to selectively initiate a handover based on the availability of the control plane interface.

Handover between a source system and a target system may also be referred to as CN handover, for example, because handover requires signaling between CNs of the respective systems over a control plane interface. Alternatively or additionally, a handoff between a source system and a target system may also be referred to as an inter-system handoff, e.g., because the source system and the target system are not identical.

The control plane interface may or may be required to connect a node of the first CN with a node of the second CN for handover. "required" may include a step that is or will be performed or triggered, or a feature that exists or will exist, for example, only if a handover is or was initiated in the step of selectively initiating a handover, for example, if a control plane interface is or was available.

At least one of the source system and the target system may include at least one of a 3GPP system and a non-3 GPP system. The 3GPP system may include at least one of a General Packet Radio Service (GPRS), a Universal Mobile Telecommunications System (UMTS), an Evolved Packet System (EPS), a Next Generation System (NGS), and a fifth generation system (5 GS).

The control plane interface may or may be required to connect a first mobility entity of the first CN with a second mobility entity of the second CN. At least one of the first mobility entity and the second mobility entity may comprise at least one of a Serving GPRS Support Node (SGSN), a Mobility Management Entity (MME) and an Access Mobility Function (AMF). The control plane interface may comprise, for example, the S3 interface for first and second systems including GPRS and EPS systems.

Initiating the handover may include, or may be required to include, sending a handover message from the first CN to the second CN over the control plane interface indicating the handover request. To initiate a handover, a handover message may be sent from a first mobility entity to a second mobility entity via a control plane interface. A first RAN, e.g., a serving base station of the first RAN, may be in a connected mode with a radio. The handover message may indicate a context of the radio.

The method may be performed by the first CN or a node of the first CN (e.g., the first mobility entity). The method may be performed by one or more nodes or entities of the first CN. Performing the method may be accomplished by performing or triggering (e.g., controlling) the corresponding steps.

Alternatively or in combination, the method may be performed by the first RAN or a node of the first RAN (e.g., a base station serving a radio). The method may be performed by one or more nodes or base stations of the first RAN. Performing the method may be accomplished by performing or triggering (e.g., controlling) the corresponding steps.

Determining availability of the control plane interface may include sending an availability message to the first RAN indicating availability. The availability message may be sent by the first CN or a node of the first CN (e.g., the first mobility entity).

Alternatively or in combination, determining the availability of the control plane interface may comprise receiving an availability message from the first CN indicating the availability. The availability message may be received by the first RAN or one or more of the nodes (e.g., serving base stations) of the first RAN.

"indicating availability" may include, for example, explicitly indicating positive availability (i.e., indicating that the corresponding control plane interface is available), (for example, explicitly indicating negative availability (i.e., indicating that the corresponding control plane interface is not available), or both positive and negative availability.

The availability message may include a Handover Restriction List (HRL). The HRL may indicate availability. The HRL may be an Information Element (IE) according to, for example, clause 9.2.3 of 3GPP TS 36.423 (e.g., release 13.6.0). Alternatively or additionally, the HRL may include a field indicating one or more target systems or one or more second RATs for which no control plane interface is available.

The availability message may be a handover request message (e.g., sent to the first RAN or node thereof when the first RAN or node thereof is the target of another handover).

The availability message may be sent to at least one node (e.g., a base station) of the first RAN. The determining or selectively initiating may include broadcasting one or more availability messages to a plurality of nodes of the first RAN. Alternatively or in combination, the availability message may be received from at least one node (e.g., mobility entity) of the first CN. The determining step may include collecting or combining availability messages from a plurality of nodes of the first CN.

The availability message may be sent and/or received when a RAN interface between the first CN and the first RAN (e.g., a base station of the first RAN) is configured. The RAN interface may be within the source system. The RAN interface may be an S1 interface (e.g. within EPS) or an N2 interface (e.g. within NGS or 5 GS).

The availability message may configure the first RAN or at least one of the one or more nodes (e.g., base stations) of the first RAN to selectively send the handover required message according to the determined availability of the control plane interface. The handover required message may be sent to the first CN, e.g. the first mobility entity. The handover required message may indicate the target system and/or the second RAN.

The base station may be an evolved node B (eNodeB or eNB) or a next generation node B (gbodeb or gNB). The base station may be a serving base station of the radio.

Availability may be determined for multiple target systems. The availability message may indicate availability for a plurality of target systems, e.g., as a group or individually for each of the target systems.

The availability message may indicate a plurality of target systems (e.g., each of the target systems) by means of a Public Land Mobile Network (PLMN) identifier, such as a Mobile Country Code (MCC) and/or a Mobile Network Code (MNC). Alternatively, the availability message may indicate availability in terms of a source system and target system pair (pair).

The first RAN may be configured for radio access in accordance with a first Radio Access Technology (RAT). The second RAN may be configured for radio access in accordance with a second RAT. The second RAT may be different from the first RAT. Alternatively or additionally, the handover may involve an inter-system handover (i.e., the source and target systems may be different), where the RATs may be the same. For example, the second RAT may be identical or compatible with the first RAT.

Availability may be determined for one or more target systems configured for radio access in accordance with a second RAT. The availability message may indicate availability of the second RAT. The availability message may indicate availability in accordance with a second RAT (e.g., a type of the second RAT). The availability message may be undifferentiated (e.g., without distinction) between one or more target systems.

At least one of the first RAT and the second RAT may include at least one of GSM, UMTS, 3GPP long term evolution, and 3GPP 5G new air interface. Handover may also be referred to as S1 handover in the context of 3GPP EPS.

The data plane of the first CN and the data plane of the second CN may include or may be connected to the same gateway. The gateway may be a packet data network gateway (PGW).

For example, if there is no interface between CN nodes of different source and target systems or different RATs, embodiments of the present technology may control the first RAN to avoid attempting inter-system and/or inter-Radio Access Technology (RAT) handovers via the first CN. Failed handover attempts of the radio served by the first RAN and loss of coverage of the radio before it has reselected another RAT or cell can be avoided.

The same ones of the further embodiments may provide seamless network support, for example, by initiating a handover to another target system having an available control plane interface and/or by increasing the channel quality of the radio in the first RAN, for example, by increasing the signal power and/or beamforming gain of the radio.

The present techniques can be implemented (embody) to improve end user quality of experience (QoE).

Fig. 1 shows a block diagram of an embodiment of an apparatus 100 for selectively initiating a handover from a source system to a target system. The source system includes a first CN and a first RAN. The target system includes a second CN and a second RAN. The first CN and the second CN are different. The first RAN and the second RAN may provide radio access in accordance with the same RAT or different RATs. The apparatus 100 may be implemented at or by the first CN.

The apparatus 100 includes a determination module 102, the determination module 102 determining or triggering a determination of whether a control plane interface for handover is available between the first CN and the second CN. The apparatus 100 also includes a selective initiation module 106 that selectively initiates or triggers selective initiation of a handover based on the availability of a control plane interface. If the control plane interface is not available, a handover of a radio currently served by the first RAN to the second RAN is not initiated or performed.

The apparatus 100 may perform or trigger any measures (measures) for preventing radio link failure between the first RAN and the served radio if a control plane interface for handover to the target system is not available. Alternatively, an alternative handover to another target system with an available control plane interface and/or measures to improve the channel quality of the radio channel between the first RAN and the served radio may be initiated or performed instead of the handover to the second RAN, for example.

The apparatus 100 (e.g., module 106) may block the request for handover from the first RAN from being handled by the first CN. Alternatively or additionally, the apparatus 100 may control the first RAN by means of an availability message to selectively initiate such a handover depending on the availability of the corresponding control plane interface for signaling about the handover. The first RAN may be informed by the first CN as to whether the first CN supports a control plane interface with a second CN of a target system that allows for inter-system (e.g., inter-RAT) handover.

Optionally, the apparatus 100 includes a configuration sending module 104. The availability message may be sent by configuration sending module 104.

For example, the apparatus 100 may configure the first RAN, or at least one node thereof, to not initiate a handover if the corresponding control plane interface is not available. The availability message may be sent only when the control plane interface is not available. The availability message may configure the first RAN or at least one node of the first RAN to avoid initiating the handover when the control plane interface is not available.

In one variation compatible with any embodiment and implementation, the determination module 102 includes the configuration transmission module 104 as a sub-module. The availability message may be sent in response to a determination of availability of the control plane interface. In another variation compatible with any embodiment and implementation, the selective initiation module 106 includes the configuration sending module 104 as a sub-module. That is, selective initiation module 106 may trigger selective initiation of a handover by sending an availability message based on the availability generated by determination module 102.

Alternatively, the selective initiation module 106 may block initiation of the handover if the node of the RAN still requests the handover to the target system in the absence of the control plane interface. For example, a node of the RAN may still request a handover because the node is not compatible with the availability message, i.e. cannot process the availability message, or if the node has not or has not received the availability message.

The apparatus 100 may be connected to a source system and/or a portion of a source system. The apparatus 100 may be embodied by or at a node of a first CN of a source system. The apparatus 100 may be connected to a first CN to control operation of the first CN when initiating a handover.

Each of the first and second RANs may include one or more base stations. The base station may comprise a non-3 GPP base station (e.g. a ZigBee network controller or Wi-Fi access point) or a 3GPP radio access node (e.g. a 3G node B, 4G eNodeB or 5G gbodeb).

The radio may include any radio configured for a radio connection mode with at least one of the first RAN and the second RAN. The radio may comprise a mobile or portable station (e.g., a STA per Wi-Fi), a user equipment (e.g., a UE per 3 GPP), or a device for machine type communication (e.g., MTC per 3GPP or Wi-Fi).

Fig. 2 illustrates a block diagram of an embodiment of an apparatus 200 for selectively initiating a handover from a source system to a target system. The source system includes a first CN and a first RAN. The target system includes a second CN and a second RAN. The first CN and the second CN are different. The first RAN and the second RAN may provide radio access in accordance with the same RAT or different RATs. The apparatus 200 may be implemented in or by a first RAN.

The apparatus 200 may be connected to a source system and/or a portion of a source system. Apparatus 200 may be embodied by or at a base station of a first RAN. The first RAN may include a plurality of base stations. At least one or each of the base stations may comprise an instance of the apparatus 200.

The apparatus 200 includes a determination module 204, the determination module 204 determining or triggering a determination of whether a control plane interface for handover is available between the first CN and the second CN. The apparatus 200 also includes a selective initiation module 206 that selectively initiates or triggers selective initiation of a handover based on availability of a control plane interface. The selectivity may comprise: if the control plane interface is not available, a handover of a radio currently served by the first RAN to the second RAN is not initiated or performed.

If a control plane interface for handover to a target system is not available, apparatus 200 may perform or trigger any measures for preventing radio link failure between the first RAN and the served radio. Alternatively, an alternative handover to another target system with an available control plane interface and/or measures to improve the channel quality of the radio channel between the first RAN and the served radio may be initiated or performed instead of the handover to the second RAN.

The determination module 204 determines whether a control plane interface for this handover is available at the first CN, e.g., in response to an indication of the handover. The indication of handover may be a measurement report from the served radio indicating handover. For example, the measurement report may indicate that a cell belonging to the second RAN and being a neighboring or overlapping cell with respect to a serving cell of the first RAN is better compensated (offset), e.g., in terms of received signal power, than the serving cell of the first RAN.

In one variation compatible with any embodiment and implementation, the determining module 204 determines the availability based on a configuration stored at the first RAN, e.g., at the apparatus 200. The configuration may be stored (e.g., set or overwritten) in accordance with an availability message indicating availability of a control plane interface at the first CN. In another variation compatible with any embodiment and implementation, the determining module 204 determines the availability by requesting an availability message from the first CN.

An availability message may be received from the first CN. Optionally, the apparatus 200 includes a configuration receiving module 202. The availability message may be received by the configuration receiving module 202. Although the embodiment of the apparatus 200 in fig. 2 shows the configuration receiving module 202 as a separate module 202, the module 202 may also be implemented as a sub-module, such as the determining module 204.

For example, the availability message may configure the first RAN (or at least one node thereof, including or connected to an instance of the apparatus 200) not to initiate a handover if the corresponding control plane interface is not available. The availability message may be received only when the control plane interface is not available.

Figure 3 illustrates a flow diagram of an embodiment 300 of a method of selectively initiating a handover from a source system including a first CN and a first RAN to a target system including a second CN and a second RAN. The method 300 includes or triggers: a step 302 of determining whether a control plane interface for handover is unavailable between the first CN and the second CN; and a step 306 of selectively initiating a handover according to the result of the determining step 302.

The determining step 302 may trigger or selectively initiate step 306 may include a step 304 of sending an availability message to the first RAN indicating the result of the determining step 302.

The apparatus 100 may perform the method 300. The method 300 may be performed by the apparatus 100, for example, at or using a first mobility entity of a first CN. For example, modules 102, 104, and 106 may perform steps 302, 304, and 306, respectively.

Figure 4 illustrates a flow diagram of a method embodiment 400 of selectively initiating a handover from a source system including a first CN and a first RAN to a target system including a second CN and a second RAN. The method 400 includes or triggers: a step 404 of determining whether a control plane interface for handover is unavailable between the first CN and the second CN; and a step 406 of selectively initiating a handover according to the result of the determining step 404.

The determining step 404 may be based on or may include the step 402 of receiving an availability message indicating unavailability.

The apparatus 200 may perform the method 400. The method 400 may be performed by the apparatus 200, for example, at or using a base station of a first RAN. For example, modules 202, 204, and 206 may perform steps 402, 404, and 406, respectively.

Any of the modules of the apparatus 100 and the apparatus 200 may be implemented by means of units configured to provide the corresponding functionality.

The present technology is outlined for an example of inter-RAT handover and an example of source and target system interworking between EPS/LTE and 5 GS. However, the present techniques may be implemented for any inter-RAT handover or any inter-system handover between interworking systems, for example, where the unavailability of (e.g., not supported for) a control plane interface for exchanging information regarding the handover between RATs or systems is applicable.

The present technology can be realized based on the following steps. As a result of steps 302 or 404, the first CN of the source system (e.g. the AMF or MME as the first mobility entity) knows that it is not configured with an interface, e.g. an interface between 4G and 5G, supporting the control plane with the second CN of the target system (e.g. the AMF or MME as the second mobility entity) other than the source system.

In a first option compatible with any embodiment or implementation, upon configuration of a RAN interface (i.e., S1 interface or N2 interface (sometimes also referred to as NG-C)) between a first CN (e.g., an MME or AMF as a first mobility entity) and the first RAN (e.g., an eNB or a gNB as a node of the RAN), the first CN notifies the first RAN in an availability message as to whether the first CN supports a control plane interface to another system as a target system. The target system may be explicitly indicated in the availability message, and/or the availability may be indicated without identifying the target system. For example, availability may be expressed as which type of RAT or RATs are supported and/or are candidates for handover.

In a second option compatible with any embodiment or implementation, the Handover Restriction List (HRL) as the availability message is extended such that the first CN (e.g., MME or AMF as the first mobility entity) indicates to the first RAN (e.g., eNB or gNB as a base station of the first RAN) in the HRL: connected mode mobility is not supported for one or more specific RATs connected to the second CN. For example, the AMF indicates in the HRL sent to the gNB: connection mode mobility for an E-UTRAN as a second RAN connected to an Evolved Packet Core (EPC) as a second CN is not supported.

In a third option compatible with any embodiment or implementation, in step 402, the first RAN is configured from an operations, administration, and management (OAM) system and/or in accordance with an OAM protocol related to the handover restrictions of the changed mobility involving the CN. In particular, the OAM system may configure the first RAN with instructions as to whether to allow or restrict a handover from a first RAT (e.g., LTE) connected with a first CN (e.g., EPC) to a second RAT (e.g., NR) connected with a second CN (e.g., next generation core or NGC).

In a fourth option compatible with any embodiment or implementation, the availability message is sent when a context of the radio (e.g., UE) is established, e.g., upon creation of a UE context in a RAN node (e.g., base station) of the first RAN. The first CN includes in the signaling to the RAN information about whether the UE should undergo an inter-CN mobility procedure (e.g., inter-CN handover preparation) or whether such mobility should optionally be prevented for other procedures. This availability information may form part of the UE context. Further, the availability information may be communicated to a RAN node serving the UE. For example, if the UE performs handover, the information is passed to the target RAN node.

Based on the information received from the first CN in the availability message, the first RAN will not trigger a handover via the first CN (e.g., an S1 handover from 4G to 5G or an N2 handover from 5G to 4G).

Alternatively, the source RAN may release the UE from the serving first RAN using an RRC procedure instead of initiating the handover when the control plane interface to the target system (e.g., providing another RAT) is not supported. Before such release occurs, the first RAN may configure the UE with information needed to reselect to another RAT or a cell in another RAT, thereby minimizing the service disruption time and impact on end user QoE.

Before releasing and redirecting the UE to a different RAT served by a different CN, the serving first RAT may check whether other RATs are in coverage, e.g., based on measurement reports of the UE. If no other RAT is available to redirect the UE, the serving first RAT may decide to: releasing the UE for an extended time during which the UE should not return to serving the first RAT; and/or handover the UE to any other available cell for which the changed RAT of the first CN is not required. Alternatively or additionally, the first RAN may extend its own coverage area in order not to trigger Radio Link Failure (RLF) of the UE.

FIG. 5 illustrates a schematic block diagram of an exemplary system environment in which any embodiments can be implemented. The source system 510 includes a first CN 512 having a first mobility entity 514. The source system 510 also includes a first RAN 516, where at least one base station 518 is configured to provide radio access to a radio 540 according to a first RAT 519. The target system 530 includes a second CN 532 having a second mobility entity 534. The target system 530 also includes a second RAN 516, where at least one base station 538 is configured to provide radio access to the radio 540 according to a second RAT 539.

First CN 512 and second CN 532 may be defined to include only mobility entities 514 and 534, respectively. Alternatively, each of CNs 512 and 532 may also include a gateway 520 for user plane traffic and databases, such as a Home Subscriber Server (HSS) containing user-related and subscriber-related information. The HSS may also provide support functions in mobility management performed by mobility entities 514 and 534. At least a portion of the nodes (e.g., nodes other than the first and second mobility entities 514, 534) may be shared by the first and second CNs 512, 532.

The present technique can be applied to any interworking between systems that connect the data plane of the system to the same packet-switched network (e.g., through shared gateway 520). The source and target systems 510, 530 may comprise, for example, any group of a GSM system supporting GPRS, a UMTS system optionally supporting HSPA, an LTE system, and a 5G system (e.g., 5GS or NGS per 3 GPP). In a 5G system, interworking between EPS and 5GS may be supported without making available an interface 520 between EPC and 5G core (5 GC), e.g., without a control plane interface 520 between MME and AMF, which is indicated by the dashed line in fig. 5.

If interface 520 is not available, systems 510 and 530 may be referred to as the non-roaming architecture of the interworking system, e.g., for interworking between 5GS and EPC/E-UTRAN without requiring an interface between MME514 and AMF 534.

One implementation of the first option uses the S1 setup procedure of the S1 interface (indicated in fig. 5) as an availability message to inform the first RAN 516 about the support (i.e., positive or negative availability) of the control plane interface 520. Availability may be expressed, for example, as what type of RAT is supported and/or as a candidate for handover to a target system. The availability message may be sent by the MME514 to the eNB518 according to document 3GPP TS36.413 (e.g. Version 14.1.0). This example is considered for the sake of brevity only. This implementation of the methods 300 and 400 is applicable to a source system where the RAN-CN interface is configured in a similar manner as the S1 setup procedure. Examples of other systems for which the first option is easily implemented include NGS as the source system (i.e., NR RAN as the first RAN) with a RAN-CN interface established in accordance with 3GPP procedures (e.g., NG establishment procedures).

Fig. 6 schematically shows a signaling diagram 600 of the S1 setup procedure. The purpose of the S1 setup procedure is to exchange application level data required for proper interoperation of eNB518 and MME514 over the S1 interface, as per clause 8.7.3.1 of document 3GPP TS36.413 (e.g., release 14.1.0). The S1 setup procedure is a first S1 application protocol (S1 AP) procedure triggered after a Transport Network Layer (TNL) association has become operational. The S1 setup procedure uses non-UE associated signaling.

The S1 setup procedure erases any existing application-level configuration data in the two nodes 514 and 518 and replaces the configuration data with the received data. The S1 setup procedure also re-initializes the E-UTRAN S1AP UE-related contexts (if any) and erases all relevant signaling connections in the two nodes 514 and 518 as would a reset procedure. Optionally, the S1 setup procedure clears MME overload status information at eNB 518.

If the eNB518 initiating the S1 setup procedure supports Closed Subscriber Group (CSG) cells (by sending an S1 setup request), the S1 setup procedure reports one or more CSG IDs of the supported CSGs. In a variation of any implementation or embodiment, the negative availability of the control plane interface for handover may be indicated by means of the CSG ID.

The signalling 600 shown in figure 6 corresponds to the successful operation of the S1 establishment procedure, for example according to clause 8.7.3.2 of document 3GPP TS36.413 (e.g. release 14.1.0). The eNB518 initiates the S1 SETUP procedure by sending an S1 SETUP REQUEST (S1 SETUP REQUEST) message to the MME514 containing the appropriate data. The MME514 responds with an S1 SETUP RESPONSE (S1 SETUP RESPONSE) message containing appropriate data, which may include an availability message 610.

The exchanged data is stored in the respective node 518 and is used for the duration of the TNL association. When the S1 setup procedure is complete, the S1 interface is operational and capable of exchanging other S1 messages.

Fig. 7 shows an example structure of an availability message 610, e.g. according to clause 9.1.8.5 of document 3GPP TS36.413 (e.g. release 14.1.0) defining the S1 SETUP RESPONSE message. If the eNB518 initiating the S1 SETUP procedure supports one or more CSG cells, the S1 SETUP REQUEST message contains the CSG ID of the supported CSG. The column "present" indicates whether the corresponding element is mandatory (M) or optional (O) in each S1 SETUP RESPONSE message.

If the S1 SETUP REQUEST message contains an information element of the name of the eNB518 (eNB name), the MME514 can use this IE as the human-readable name of the eNB 518. If the S1 SETUP RESPONSE message contains an IE for the name of the MME514 (MME name), eNB518 may use this IE as the human-readable name for the MME 514. If the MME relay support indicator IE is contained in the S1 SETUP RESPONSE message, eNB518 considers this IE when selecting the appropriate MME514 for the relay node.

For example, the S1 SETUP REQUEST message may include the availability message 610 by including an additional IE 612 as indicated in the last line of fig. 7. IE 612 may be referred to as an inter-CN relocation support indicator to 5G. If IE 612 is contained in S1 SETUP RESPONSE message 610, eNB518 considers this IE in selecting the appropriate procedure when UE 540 needs to move into the 5G system as target system 530. For example, the eNB518 may determine to avoid triggering a handover procedure involving the CN (i.e., via the first CN 512).

The availability message 610 may be sent by the MME514 per step 304 and received by the eNB518 per step 402 to convey the TNL associated information.

Alternatively or additionally, a UE association procedure may be used to implement the availability message 610, such as initial UE context establishment, handover signaling, and the like.

The implementation of the second option uses HRL as the availability message 610, e.g. according to clause 9.2.1.22 of 3GPP TS36.413 (e.g. release 14.1.0). As shown in fig. 8, for an inter-system handover from 4G to 5G, the MME514 may send an HRL 610 including an indicator 612 of (e.g., negative) availability to the eNB 518.

The HRL 610 may follow an IE that defines roaming or access restrictions for subsequent mobility actions, such as handover and Coverage and Capacity Optimization (CCO), or Secondary Cell Group (SCG) selection during dual connectivity operation, for which the eNB518 provides information about the objectives of the mobility action for the UE 540. If the eNB518 receives the handover restriction list IE, the eNB518 overwrites the previously received restriction information.

A similar or equivalent HRL 610 may be sent by the AMF as the first mobility entity to the gNB as the base station of the first RAN for an inter-system handover from 5G to 4G. The HRL 610 may contain information 612 that "E-UTRAN connected to EPC" is not supported for connected mode mobility (i.e., handover).

An alternative or additional implementation of the availability message 610 extends the meaning of the forbidden inter-RAT IE in the HTL.

Fig. 9 shows a schematic block diagram of an embodiment of the apparatus 100 and 200 at nodes 514 and 518, respectively. The apparatuses 100 and 200 include one or more processors 904 for performing the methods 300 and 400, respectively, and memory 906 coupled to the one or more processors 904. For example, memory 906 may be encoded with instructions that implement at least one of modules 102-106 and at least one of modules 202-206, respectively.

The one or more processors 904 may be a combination of one or more microprocessors, controllers, microcontrollers, central processing units, digital signal processors, application specific integrated circuits, field programmable gate arrays, or any other suitable computing device, resource, or combination of hardware, microcode, and/or encoded logic operable to provide network node functionality alone or in combination with other components of the device 100 or 200, such as the memory 906. For example, the one or more processors 904 may execute instructions stored in memory 906. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "a device is operable to perform an action" may denote that the device is configured to perform or trigger the action.

As schematically shown in fig. 9, the apparatuses 100 and 200 may be embodied by nodes 514 and 518, respectively. For example, as schematically shown in fig. 10, the nodes 514 and 518 include a RAN interface 902, the RAN interface 902 being coupled to the devices 100 and 200, respectively, for communication with each other.

In a variant, the functionality of the apparatus 100 and/or the apparatus 200 is (e.g. partly or completely) provided (virtualized) by one or more other nodes of the radio network. That is, one or more other nodes perform method 300 and/or method 400. The functionality of the apparatus 100 and/or 200 is provided to the network nodes 514 and/or 518 by one or more other nodes via the interface 902 or a dedicated wired or wireless interface.

Embodiments of the present technology as have become apparent from the above description may improve inter-system handovers. The present techniques may be applied to inter-RAT mobility. The present technology may control handover through the CN.

The present techniques may prevent handover from being initiated without a control plane interface between respective core networks for exchanging corresponding signaling. The selectivity as to whether to initiate a handover may relate to whether a control plane interface is available, respectively. The selectivity in initiating handover may only apply to CN handover.

The present techniques enable the RAN to know the likelihood of triggering a successful inter-RAT handover via the CN, as well as avoid failed handover attempts and prevent the impact on end-user performance due to increased time due to the UE losing connectivity with the network.

Many of the advantages of the invention will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the elements and devices without departing from the scope of the invention and/or without sacrificing all of its advantages.