METHOD AND USER EQUIPMENT FOR SELECTING A CORE NETWORK

Abstract

Provided herein is a system, components, and methods for a user equipment therein operating on a first base node of a cellular network, the first base node communicatively coupled to two core networks of said cellular network, the user equipment operating in an open data exchange session by means of a data exchange context terminating in selected one of the two core networks, the user equipment further maintaining a first device identity received from said selected core network. Other embodiments are disclosed.

Claims

1. A method for a user equipment (UE) operating on a first base node (eNB1) of a cellular network (CN), the first base node communicatively coupled to two core networks of said cellular network, the user equipment (UE) operating in an open data exchange session by means of a data exchange context terminating in selected one of the two core networks, the user equipment further maintaining a first device identity received from said selected core network, the method comprising the step for the user equipment of: identifying at least one second base node (eNB2) of said cellular network (CN), checking if said at least one second base node (eNB2) has access to the selected core network, if not, sending a connection reestablishment message to the second base node (eNB2), having access to a core network different from the selected core network, hereinafter the second core network, receiving through the second base node a second device identity of the second core network, sending an acknowledge message to the second base node (eNB2), resuming said data exchange session with said second base node (eNB2) over the second core network using said second device identity.

2. The method according to claim 1, wherein the user equipment (UE) further maintains a context identity provided by the selected core network, wherein the connection reestablishment message comprising a core network context fetch instruction providing said context identity and said first device identity.

3. A method according to claim 1, the step of identifying at least one second base node (eNB2) is conducted in response to detecting a radio link failure in communication with the first base node (eNB1).

4. The method according to claim 1, wherein the user equipment (UE) maintains at least one first encryption key received from the first base node (eNB1), whereby the step of receiving the second device identity is conducted using said at least one first encryption key, further comprising the step of receiving criteria for generating at least one second encryption key from the second base node (eNB2), whereby the step of resuming the data exchange session is conducted using said at least one second encryption key.

5. User equipment (UE) for operating on a first base node (eNB1) of a cellular network (CN), the first base node being communicatively coupled to two core networks of said cellular network (CN), the user equipment (UE) being configured to operate in a data exchange session by means of a data exchange context terminating in selected one of the two core networks, and to maintain a first device identity received from said selected core network, wherein the user equipment UE) is configured to: identify at least one second base node (eNB2) of said cellular network (CN), check if said at least one second base node (eNB2) has access to the selected core network, if not, send a connection reestablishment message to the second base node, having access to a core network different from the selected core network, hereinafter the second core network, receive through the second base node (eNB2) a second device identity of the second core network, send an acknowledge message to the second base node (eNB2), resume said data exchange session with said second base node (eNB2) over the second core network using said second device identity.

6. The user equipment (UE) according to claim 5, further configured to maintain a core node identity provided by the selected core network, wherein the connection reestablishment message comprising a core network context fetch instruction providing said core node identity and said first device identity.

7. The user equipment (UE) according to claim 5, further configured to maintain at least one first encryption key received from the first base node (eNB1), whereby for receiving the second device identity the user equipment (UE) is configured to use said at least one first encryption key, further to receive criteria for generating at least one second encryption key from the second base node (eNB2), whereby for resuming the data exchange session the user equipment is configured to use said at least one second encryption key.

8. A system comprising: a First core network element (FCNE) of a first core network being part of a cellular network comprising at least two core networks, said first core network element being communicatively coupled to at least one second core network element (SCNE) of a second core network being part of the cellular network, a Second core network element (SCNE) of a second core network being part of a cellular network comprising at least two core networks, the second core network element (SCNE) being communicatively coupled to at least one first core network element (FCNE) of a first core network being part of the cellular network, said second core network element (SCNE) further being communicatively coupled to at least one base node (eNB2); and a Base node (eNB2) of a cellular network (CN) communicatively coupled to at least one second core network element (SCNE) of a second core network of said cellular network (CN), and configured to serve a plurality of user equipments (UE), wherein the first core network element (FCNE) is configured to: receive a core context fetch message comprising a device identity and a context identity from one of the second core network elements (SCNE), fetch a first data exchange context based on said context identity, said first data exchange context comprising a set of parameter concerning the first data exchange context, provide to said second core network element (SCNE) a context message comprising at least parts of said set of parameter concerning said first data exchange context.

9. The system of claim 8, wherein the First core network element (FCNE), further configured to receive a message from said second core network element (SCNE) indicating acknowledgment of creating a second data exchange context replacing said first data exchange context, in response to conduct at least one of closing and deleting said first data exchange context.

10. The system of claim 8, wherein the second core network element (SCNE) is configured to: receive from said base node (eNB2) a core context request message comprising a first device identity identifying a user equipment (UE) which operates with said base node (eNB2), and at least one context identity, send a core context fetch message to said first core network element (FCNE), determine that said first device identity and said identity is used in a data exchange session of the first core network element (FCNE), receive from said first core network element a context message comprising context parameter of an first data exchange context of said user equipment, generate a new device identity for said user equipment (UE), create a second data exchange context using said received context parameter, and provide to the base node (eNB2) a set of context parameter relating to said second data exchange context and said second device identity.

11. The system of claim 10, wherein for the second core network element (SCNE), said context request message further comprises a core node identity identifying a first core network element (FCNE), wherein said sending of the core context fetch message is addressed to said first core network element (FCNE) by means of said core node identity.

12. The system of claim 11 wherein the second core network element (SCNE), further configured to create criteria for generating at least one second encryption key, wherein the second core network element (SCNE) is configured in conjunction with said providing to the base node (eNB2) of the set of context parameter to provide said criteria to the base node.

13. The system of claim 12 wherein for the second core network element (SCNE), the core context request message further comprises at least one first encryption key, wherein the message for providing the set of context parameter is encrypted by means of said at least one first encryption key.

14. The system of claim 13 wherein the second core network element (SCNE), further configured to receive an acknowledgement message from the base node (eNB2) comprising the second device identity, in response indicate said acknowledgment to the first core network element (FCNE) for conducting at least one of closing and deleting the context.

15. A method for operating a second core network element (SCNE) of a second core network of a cellular network (CN) comprising at least two core networks, said second core network element (SCNE) being communicatively coupled to at least one first core network element (FCNE) of the cellular network, said second core network element (SCNE) further being communicatively coupled to at least one base node (eNB2), the method comprising the steps for the second core network element (SCNE) of: receiving from said base node (eNB2) a core context request message comprising a first device identity identifying a user equipment (UE) which operates with said base node (eNB2), determining that said first device identity is operated in a data exchange session by means of a first data exchange context of the first core network element (FCNE), if this is the case, send a core context fetch message to said first core network element (FCNE), receiving from said first core network element (FCNE) a context message comprising context parameter of an first data exchange context of said user equipment (UE), generating a new device identity for said user equipment (UE), creating a second data exchange context using said received context parameter, and providing to the base node (eNB2) a set of context parameter relating to said second data exchange context and said second device identity.

16. The method for according to claim 15, further comprising the step for the second core network element (SCNE) of creating criteria for generating at least one second encryption key, wherein in conjunction with the step of providing to the base node (eNB2) the set of context parameter providing said criteria to the base node (eNB2).

17. The system of claim 8 wherein the Base node (eNB2) is configured to: receive a connection reestablishment message from one of the served user equipment (UE), wherein the connection reestablishment message comprising an indication of a core network element (FCNE) belonging to a different core network, than the base node (eNB2) is connected to, a device identity and at least one context identity of said user equipment, sending a core context request message to the second core network element (SCNE) comprising the device identity and the at least one context identity, receiving in response a set of context parameter relating to a second data exchange context and a new device identity, forwarding new device identity to said served user equipment (UE).

18. The system of claim 17, wherein the base node (eNB2) is, configured to provide in response to reception of an acknowledgment message from said service user equipment (UE) an acknowledgment message comprising said new device identity to the second core network element (SCNE).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0158] The following description and the annexed drawings set forth in detail certain illustrative aspects and are indicative of a few of the various ways in which the principles of the embodiments may be employed. Characteristics and advantages of the present invention will appear when reading the following description and annexed drawings of advantageous embodiments given as illustrative but not restrictive examples.

[0159] FIG. 1 represents a user equipment of the type to which the present invention is applied to as an embodiment in conjunction with a base node according to the prior art;

[0160] FIG. 2 represents in an exemplifying embodiment a user equipment operating non-stationary with two base nodes;

[0161] FIG. 3 shows a sequence diagram of a preferred embodiment of the inventive method.

[0162] FIG. 1 schematically shows a user equipment UE according to the prior art. The user equipment UE is camping on a base node eNB1 supporting the NB-IoT category. The base node eNB according to this embodiment might therefore be a 4G or a 5G base node, as NB-IoT is for both technology standards defined, at least backwards compatible.

[0163] The base node eNB1 is connected to core network elements of at least two core networks, in this case the first core network element FCNE, which supports 5G (New Radio) and the second core network element SCNE, supporting 4G (LTE). The core networks of the respective technology standards are called for 4G Evolved Packet Core (EPC) and for 5G NextGen-Core (NGC).

[0164] Each core network provides different capabilities. E.g. the 5G core network NGC might have the capability of supporting certain slices, e.g. for ultra-reliable communication or dedicated for machine-type communication.

[0165] For a user equipment UE leaving the coverage area of the base node eNB1, it has to care for mobility when operating in an open data exchange session. For this situation the prior art offers no solution.

[0166] For doing so the inventive method is illustrated by an exemplifying embodiment in FIG. 2.

[0167] The user equipment UE as shown in FIG. 2 is operating non-stationary, that means it is moving. It is situated in cell C1 of the first base node eNB1. In the shown example after camping on the first base node eNB1 it is setting up a connection at time t.sub.1 with the selection of one of the core networks. The connection is in this case set up by means of the first core network element FCNE, which is indicated by a solid line as opposed to the dashed line to the second core network element SCNE of the EPC.

[0168] Then at time t2 the user equipment UE moved away from the base node eNB1, that means out of cell C1 into cell C2 of the second base node eNB2

[0169] It turned out that the signals from base node eNB1 are received that bad, that radio link failures (RLF) appear. This indicates to a user equipment UE operating in NB-IoT, that it cannot continue operating with said currently serving base node.

[0170] Hence the user equipment UE selects a better suitable base node, in this case the second base node eNB2.

[0171] However the base node eNB2 does not have access to both core networks, only to the EPC, represented by the second core network element SCNE. In this situation the situation appears, that the base node eNB2 has no means to retrieve the data exchange context that was setup for creating the data exchange session at time t.sub.1.

[0172] To solve that issue the message flow of FIG. 3 according to an exemplifying embodiment of the invention is preferably executed.

[0173] This process flow starts with a user equipment UE which is situated in the cell area C1 of a first base node eNB1. This base node has access to a first core network element FCNE and a second core network element SCNE of a first and a second core network, in particular a 5G NextGenCore (NGC) and a 4G Evolved Packet Core (EPC).

[0174] The first base node eNB1 broadcasts with message M1 information relating to resources for both core networks. In response for camping on the base node eNB1 and setting up a data exchange session, the user equipment UE selects the 5G NextGenCore by picking the respective resources with message M2.

[0175] The first base node eNB1 takes this request, forwards it to the first core network element FCNE of the 5G NGC with a request for a context ID. This includes setting up a context with message M3.

[0176] In response the first core network element provides when successful with message M4 to the first base node the data exchange context parameter, in particular the device identity. More information are preferably provided, in particular the core network identity and/or the context identity identifying the established first data exchange context. The received data, are at least parts thereof, are forwarded with message M5 to the user equipment.

[0177] Hence now the data exchange session over the first data exchange context is setup up and running, as indicated by message M6, which is a data exchange message that is supposed to terminate at the FCNE. This may comprise sending measurement data from a metering device.

[0178] At step M7 the UE leaves the coverage area of the first base node eNB1 in that way, that the signals of the first base node are that bad, that the user equipment evaluates if at least one second base node eNB2 is according to the suitability criteria better suited for communication. This is in particular happening through a plurality of radio link failures. If this is the case, the user equipment decides to reselect to the second base node eNB2.

[0179] Now the user equipment has the need to continue the running data exchange session. By now the user equipment UE does not necessarily know if the second base node eNB2 has access to a first core network element FCNE, which could easily retrieve the data exchange context and simply continue operating the data exchange session with it.

[0180] Alternatively the user equipment retrieves e.g. through a broadcast or any other kind of data exchange, in particular during the re-selection phase, the information from the second base node eNB2, that it is only able to access a second core network element SCNE being part of the LTE core network.

[0181] In any case the user equipment sends a connection re-establish message M8 to the second base node. This message in particular comprises the retrieved device identity and in this exemplifying embodiment at least one related context identity. Preferably it also comprises an identifier of the first core network element, here called core node identity, which it in particular retrieved through message M5 above.

[0182] The second base node eNB2 sends this request with message M9 to the accessible second core network element SCNE. There it is preferably figured out, in particular by means of the core node identity, that the user equipment was by now served by a core node element of another core network.

[0183] Consequently it uses the core node identity to send a core context fetch message M10 to another first core node element of the core network, that is handling the identified data exchange context, in order to retrieve the data exchange context parameter. This does not necessarily mean that the first core network element FCNE, which is identified by the core node identity, is directly accessed. It is rather possible that any of the first core network elements of the 5G core network receives a message, wherein the first core network element which was handling the data exchange context is identified through the core node identity. The addressed first core network element FCNE will than handle within its core network all necessary steps to retrieve the data exchange context information.

[0184] These are provided to the second core network element SCNE with message M11. The second core network element SCNE creates a new data exchange context with these received information and creates a new second device identity. These information and the second device identity and the context identity of the new second data exchange context are provided with message M12 to the second base node eNB2 and with message M13 to the user equipment. These messages are in particular encrypted with a first encryption key that was negotiated between the user equipment and the first core network element. Preferably this message also comprises criteria for generating a new set of encryption keys for the coming communication. This is necessary as the originally used keys from the first core network element FCNE cannot be reused by the second core network element.

[0185] It is likely that this key generation requires some more messaging between the user equipment and the second core network element, until both have securely retrieved the encryption key.

[0186] The user equipment then sends with message M14 an acknowledgment message to base node eNB2, which then forwards this message with message M15 to the second core network element SCNE. This acknowledgment in particular comprises the new second device identity.

[0187] When the second core network element SCNE receives this acknowledgment it is sure that the second data exchange context was well established. Hence it can instruct with message M16 to close and/or delete the first data exchange context at the first core network element FCNE. Again it may be another component of the 5G core network which actually does the work, but the addressed first core network element confirms with message M17 the deletion etc.

[0188] This information is not important for the user equipment as it may assume with the acknowledgment that it can now resume the data exchange session. This is done with message M18 to the base node eNB2, respectively message M19 to the second core network element. This message is in particular encrypted with the created encryption key from message M13.

[0189] Also the acknowledgement message M14 may be encrypted with this key. As this has no big data which need to be secured, this is not mandatory.

[0190] Now the user equipment can continue with the data exchange session on basis of the new created second data exchange context via the second core network element SCNE.

[0191] In case that the data exchange session comprises service parameters that are not supported by the second network, e.g. 5G services like ultra-low latency operation, then there are two options.

[0192] First the related parameters will be replaced by appropriate default values. Preferably it is indicated in a message to the user equipment, that this replacement has happened. So the user equipment may decide not to continue the data exchange session under that conditions, or to accept this replacement.

[0193] Second the data exchange context is indicated as not being able to be resumed as such, i.e. the context request message sent by the device is rejected and hence a new session is set up (abnormal condition abort).

[0194] With the shown message flow it is achieved, that in a manner with low impact for the user equipment the established data exchange session can be continued although it changed to a base node which has no access to the originally used core network.

[0195] In the above detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the scope of the invention. The above detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled.