WO2020104023A1

WO2020104023A1 - Packet data unit (pdu) session continuity in ultra-reliable low-latency communications (urllc) scenarios

Info

Publication number: WO2020104023A1
Application number: PCT/EP2018/081967
Authority: WO
Inventors: Ling Yu; David NAVRÁTIL; Vinh Van Phan; Jani Matti Johannes Moilanen
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2018-11-20
Filing date: 2018-11-20
Publication date: 2020-05-28
Anticipated expiration: 2021-05-20

Abstract

There are provided measures for packet data unit (PDU) session continuity in ultra- reliable low-latency communications (URLLC) scenarios. Such measures (of an apparatus including a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) exemplarily comprise storingfirst information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting,on transmission of a request for relocation of said first packet data unit session to said second terminalor for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

Description

Title

Packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios

Field

The present invention relates to packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios. More specifically, the present invention exemplarily relates to measures (including methods, apparatuses and computer program products) for realizing packet data unit (PDU) session continuity in ultra-reliable low- latency communications (URLLC) scenarios.

Background

The present specification generally relates to ultra-reliable low-latency communications. An important issue in relation to ultra-reliable low-latency communications is provisioning of redundancy for improving system reliability and availability. Two approaches in relation to user plane redundancy are worked out.

Namely, on the one hand, redundant user plane paths may be provided based on dual connectivity.

Figure 7 is a schematic diagram of an example of a system environment in particular illustrating a high-level architecture according to such approach.

Figure 8 is a schematic diagram of an example of a system environment in particular illustrating this approach mapped to 5GS architecture.

Further, on the other hand, at least two user equipments (UE) may be deployed on a device, and these may be operated UEs more or less like independent UEs. Figure 9 is a schematic diagram of an example of a system environment in particular illustrating a high-level architecture according to such approach.

Figure 10 is a schematic diagram of an example of a system environment in particular illustrating this approach mapped to 5GS architecture.

According to the approach illustrated in Figures 9 and 10, hardware redundancy (multiple UEs) is implemented on the device side (e.g. host device) to improve system reliability against UE hardware failures.

This approach with two UEs per host provides full redundancy of user plane and possibly also control plane paths through 3^rd Generation Partnership Project (3GPP) domain, which offers high reliability against failures in the entities along the paths.

Similar hardware redundancy approaches are already used commercially in fixed access domain for use cases where ultra-high reliability is required (e.g. electricity grid protection).

The failure of any UE (wireless or wired) may happen e.g. due to overheating caused by e.g. continuous data transfer, hardware component failure, or a physical damage. In case of mobile UEs, some additional failure causes, such a running out of battery, are of concerned.

A problem underlying the present invention arises in a scenario when a UE-side host comprises two terminals (i.e. UEs), as illustrated in Figures 9 and 10 and one terminal (i.e. UE) fails.

In such case, it is desired to efficiently recover from the UE failure and continue providing redundant data paths with remaining UE(s). A fail-back to the dual connectivity approach is an alternative assuming the remaining UEs have dual connectivity capability.

When a UE failure occurs in such scenario, under this assumption, it is thus possible to fall back to a single UE per host operation (Figures 7, 8) with redundant radio access network (RAN) and core network (CN). In such case, the remaining UE may establish a new PDU session with dual connectivity.

In other words, when one UE in the same device has hardware failure, the system may fail-back to the dual connectivity operation. That is the other UE(s), which is(are) still functioning, will request a PDU session establishment for setting up the redundant user plane path. Assuming that the UE has the dual connectivity capability, the second PDU session may be established for the UE according to the dual connectivity procedure.

However, setup of the PDU session as well as dual connectivity in the RAN afterwards may take some time. This may not be critical for initial setup when no redundant data paths are available. However, when the redundant data paths have already been established, unavailability or interruption of one redundant path may impact the overall reliability performance especially if the working user plane path is not as reliable as required during the new PDU session establishment.

Hence, the problem arises that speeding up the new PDU session establishment from the remaining UE(s) is necessary.

Hence, there is a need to provide for packet data unit (PDU) session continuity or an application session continuity via a new PDU session that is established using parameters of previously established PDU session in ultra-reliable low-latency communications (URLLC) scenarios.

Summary

Various exemplary embodiments of the present invention aim at addressing at least part of the above issues and/or problems and drawbacks.

Various aspects of exemplary embodiments of the present invention are set out in the appended claims.

According to an exemplary aspect of the present invention, there is provided a method of a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the method comprising storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

According to an exemplary aspect of the present invention, there is provided a method of an apparatus including a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the method comprising storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

According to an exemplary aspect of the present invention, there is provided a method of a network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the method comprising receiving a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, validating permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal, deciding on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and initiating a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal.

According to an exemplary aspect of the present invention, there is provided an apparatus implementing a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

According to an exemplary aspect of the present invention, there is provided an apparatus implementing a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

According to an exemplary aspect of the present invention, there is provided a network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the network system comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform receiving a request for relocation of said first packet data unit session to said second terminal orfor establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, validating permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal, deciding on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and initiating a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal. According to an exemplary aspect of the present invention, there is provided an apparatus implementing a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising storing circuitry configured to hold first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting circuitry configured to detect a predetermined failure of said first terminal, deciding circuitry configured to decide, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting circuitry configured to transmit said request based on said first information.

According to an exemplary aspect of the present invention, there is provided an apparatus implementing a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising storing circuitry configured to hold first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting circuitry configured to detect a predetermined failure of said first terminal, deciding circuitry configured to decide, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting circuitry configured to transmit said request based on said first information.

According to an exemplary aspect of the present invention, there is provided a network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the network system comprising receiving circuitry configured to receive a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, validating circuitry configured to validate permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal, deciding circuitry configured to decide on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and initiating circuitry configured to initiate a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal.

According to an exemplary aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present invention), is configured to cause the computer to carry out the method according to any one of the aforementioned method-related exemplary aspects of the present invention.

Such computer program product may comprise (or be embodied) a (tangible) computer- readable (storage) medium or the like on which the computer-executable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof.

Any one of the above aspects enables an efficient reuse of the existing PDU session resources and configurations of the failed UE as much as possible to speed up the failure recovery of redundant data paths by the remaining UE(s) of the same device to thereby solve at least part of the problems and drawbacks identified in relation to the prior art. By way of exemplary embodiments of the present invention, there is provided packet data unit (PDU) session continuity through PDU session relocation from one UE to other UE or through a PDU session establishment using at least in part the configuration of previously established PDU session in ultra-reliable low-latency communications (URLLC) scenarios. More specifically, by way of exemplary embodiments of the present invention, there are provided measures and mechanisms for realizing packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios.

Thus, improvement is achieved by methods, apparatuses and computer program products enabling/realizing packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios.

Brief description of the drawings

In the following, the present invention will be described in greater detail by way of non limiting examples with reference to the accompanying drawings, in which

Figure 1 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 2 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 3 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 4 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 5 is a schematic diagram of a procedure according to exemplary embodiments of the present invention, Figure 6 is a schematic diagram of a procedure according to exemplary embodiments of the present invention,

Figure 7 is a schematic diagram of an example of a system environment in particular illustrating a high-level architecture according to an approach generally providing redundancy of user/control plane paths,

Figure 8 is a schematic diagram illustrating the example of Figure 7 mapped to 5GS architecture,

Figure 9 is a schematic diagram of another example of a system environment in particular illustrating a high-level architecture according to an approach generally providing redundancy of user/control plane paths,

Figure 10 is a schematic diagram illustrating the example of Figure 9 mapped to 5GS architecture,

Figure 1 1 is a schematic diagram of an example of a system environment illustrating a general concept according to exemplary embodiments of the present invention,

Figure 12 shows a schematic diagram of signaling sequences according to exemplary embodiments of the present invention,

Figure 13 shows a schematic diagram of signaling sequences according to exemplary embodiments of the present invention,

Figure 14 is a block diagram alternatively illustrating apparatuses according to exemplary embodiments of the present invention, and

Figure 15 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention.

Detailed description of drawings and embodiments of the present invention The present invention is described herein with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied.

It is to be noted that the following description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments. Namely, the present invention and its embodiments are mainly described in relation to 3GPP specifications being used as non-limiting examples for certain exemplary network configurations and deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the invention in any way. Rather, any other communication or communication related system deployment, etc. may also be utilized as long as compliant with the features described herein.

Hereinafter, various embodiments and implementations of the present invention and its aspects or embodiments are described using several variants and/or alternatives. It is generally noted that, according to certain needs and constraints, all of the described variants and/or alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various variants and/or alternatives).

According to exemplary embodiments of the present invention, in general terms, there are provided measures and mechanisms for (enabling/realizing) packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios.

The above-outlined approach in relation to the dual connectivity capable UE is not efficient because it ignores that there are existing resources allocated for an ongoing PDU session of the failed UE and there may be downlink data arriving to the network.

Thus, considering that the resources for the PDU session of failed UE are already allocated in the network, exemplary embodiments of the present invention aim to reuse the existing PDU session resources and/or configurations of failed UE as much as possible to speed up the failure recovery of redundant data paths by the remaining UEs of the same host/device and to provide application session continuity.

In other words, according to exemplary embodiments of the present invention, the new PDU session establishment from the remaining UE(s) is speeded up by reuse of the existing resources and/or configurations of the old PDU session of the failed UE. It is thus possible in such situations to recover resources allocated to the failed UE, which provides several benefits.

Thus, according to exemplary embodiments of the present invention, a PDU session relocation procedure is disclosed to achieve the reuse of existing PDU session resources. The PDU session relocation procedure allows for relocating an existing PDU session of a failed UE to another UE of the same host.

In a similar way as the PDU session relocation procedure, a PDU session establishment procedure may reuse existing PDU session configuration at least in part to achieve application session continuity.

Figure 1 1 schematically illustrates such PDU session relocation from a first UE to a second UE. The procedure for such PDU session relocation requires in-device coordination for sharing UE context information between the UEs.

The PDU session relocation aims at providing PDU session continuity between UEs of the same host, which also means that higher layer (e.g. application) sessions could be continued. For example, it is assumed that IP or Ethernet addresses could be maintained. The PDU session relocation procedure is to be triggered by the UE as soon as a failure of the other UE in the host is detected and it relies on an in-device coordination between the UEs. Consequently, the procedure is triggered before the failure can be detected by the network, e.g. upon a radio link failure, resulting in faster recovery of redundant path through RAN and core network.

Figure 1 is a block diagram illustrating an apparatus (terminal) 10 according to exemplary embodiments of the present invention. The apparatus 10 (implementing a second terminal (second UE) operable in parallel with a first terminal (first UE) of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) may be a user equipment (UE) 10 comprising storing circuitry 1 1 , detecting circuitry 12, deciding circuitry 13, and transmitting circuitry 14. The storing circuitry 1 1 holds first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal. The detecting circuitry 12 detects a predetermined failure of said first terminal. The deciding circuitry 13 decides, based on said detecting (of the detecting circuitry 12), on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session. The transmitting circuitry 14 transmits said request based on said first information. Figure 5 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 1 may perform the method of Figure 5 but is not limited to this method. The method of Figure 5 may be performed by the apparatus of Figure 1 but is not limited to being performed by this apparatus.

As shown in Figure 5, a procedure (of a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) according to exemplary embodiments of the present invention comprises an operation of storing (S51 ) first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, an operation of detecting (S52) a predetermined failure of said first terminal, an operation of deciding (S53), based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and an operation of transmitting (S54) said request based on said first information.

With respect to the detecting, it is noted that this includes not only efforts by the second terminal of monitoring and/or measuring for the predetermined failure of said first terminal. Instead, the detecting is also to be understood to include the receiving or retrieving of information in relation to the predetermined failure of said first terminal. Hence, the detecting also includes that the predetermined failure of said first terminal is indicated to the second terminal, in particular to the detecting circuitry of the second terminal.

With respect to the transmitting of said request (and the respective deciding), as mentioned, this may relate to transmitting (and correspondingly deciding on) a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, wherein said third packet data unit session provides session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session (in other words, this may alternatively relate to transmitting (and correspondingly deciding on) a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session with the purpose of session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session).

Figure 2 is a block diagram illustrating an apparatus 10 according to exemplary embodiments of the present invention. In particular, Figure 2 illustrates a variation of the apparatus 10 shown in Figure 1 . The apparatus 10 according to Figure 2 may thus further comprise receiving circuitry 21 , configuring circuitry 22, setting-up circuitry 23, maintaining circuitry 24, adopting circuitry 25, and/or sending circuitry 26.

In an embodiment at least some of the functionalities of the apparatus shown in Figure 1 (or 2) may be shared between two (or more) physically separate devices forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes. According to exemplary embodiments of the present invention, said request is indicative of said first packet data unit session.

According to further exemplary embodiments of the present invention, said request includes at least one information item of said first information.

According to a variation of the procedure shown in Figure 5, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to exemplary embodiments of the present invention may comprise an operation of receiving a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal, and an operation of configuring, if said relocation of said first packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said first packet data unit session for a first user plane path and said second packet data unit session for an already established second user plane path, or of configuring, if said establishment of said third packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said third packet data unit session for said first user plane path and said second packet data unit session for said already established second user plane path.

According to a variation of the procedure shown in Figure 5, exemplary details of the configuring operation are given, which are inherently independent from each other as such. Such exemplary configuring operation according to exemplary embodiments of the present invention may comprise an operation of setting up, if said relocation of said first packet data unit session is acknowledged, a first user plane path on said first packet data unit session, or of setting up, if said establishment of said third packet data unit session is acknowledged, said first user plane path on said third packet data unit session, and an operation of maintaining an established second user plane path on said second packet data unit session.

According to a variation of the procedure shown in Figure 5, exemplary details of the configuring operation are given, which are inherently independent from each other as such. Such exemplary configuring operation according to exemplary embodiments of the present invention may comprise an operation of adopting resources allocated to said first packet data unit session before transmitting said relocation request for said first user plane path.

According to a variation of the procedure shown in Figure 5, exemplary details of the transmitting operation (S54) are given, which are inherently independent from each other as such. Such exemplary transmitting operation (S54) according to exemplary embodiments of the present invention may comprise an operation of sending, by said second terminal, a non access stratum message as said request to a radio access network node serving said second terminal, and/or an operation of sending, by said second terminal, utilizing a radio access network context of said first terminal, a terminal context update indication as said request to a radio access network node serving said first terminal.

According to a variation of the procedure shown in Figure 5, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to exemplary embodiments of the present invention may comprise an operation of receiving first capability information on a packet data unit session relocation capability of a first core network terminating said first packet data unit session and/or second capability information on a packet data unit session relocation capability of a second core network terminating said second packet data unit session.

According to further exemplary embodiments of the present invention, said first information comprises at least one of a permanent or temporary identity of said first terminal, redundancy related information, a global packet data unit session identity of said first packet data unit session, credential related information for validation of permission of said second terminal, an identifier of a network entity terminating and/or serving said first packet data unit session allocated to said first terminal, and packet data unit session configuration related information.

Figure 15 is a block diagram illustrating an apparatus (host) 150 according to exemplary embodiments of the present invention. The apparatus 150 comprises a first terminal (first UE) 151 and the second terminal (second UE) 10 operable in parallel with a first packet data unit session allocated to said first terminal 151 and a second packet data unit session allocated to said second terminal 10, wherein said second terminal 10 is configurable for dual connectivity allowing simultaneous operation of two user plane paths. The apparatus (host) 150 further includes a host controller 152 configured to control the host 150, functionalities of the first terminal 151 and the second terminal 10, as well as cooperation and coordination between the first terminal 151 and the second terminal 10.

The second terminal may be embodied as described in the exemplary embodiments of the present invention above.

Thus, the apparatus according to Figure 15 (preferably the second terminal 10 of the apparatus according to Figure 15) may perform the method of Figure 5 but is not limited to this method. The method of Figure 5 may be performed by the apparatus of Figure 15 (preferably by the second terminal 10 of the apparatus according to Figure 15) but, as mentioned above, is not limited to being performed by this apparatus.

The apparatus according to Figure 15 (preferably the second terminal 10 of the apparatus according to Figure 15) may thus, according to exemplary embodiments of the present invention comprise an operation of storing (S51 ) first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, an operation of detecting (S52) a predetermined failure of said first terminal, an operation of deciding (S53), based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and an operation of transmitting (S54) said request based on said first information.

The method as performed by the apparatus of Figure 15 (preferably by the second terminal 10 of the apparatus according to Figure 15) may be modified in line with the exemplary embodiments of the present invention explained above in relation to the method shown in Figure 5 in relation to the second terminal 10.

With respect to the detecting, it is noted that this includes not only efforts by the second terminal 10 of monitoring and/or measuring for the predetermined failure of said first terminal 151. Instead, the detecting is also to be understood to include the receiving or retrieving of information in relation to the predetermined failure of said first terminal 151. Hence, the detecting also includes that the predetermined failure of said first terminal 151 is indicated (e.g. by the host controller 152) to the second terminal 10, in particular to the detecting circuitry of the second terminal 10.

Figure 3 is a block diagram illustrating a network system 30 according to exemplary embodiments of the present invention. The network system 30 (including a first core network unit operable to serve a first terminal (first UE) allocated to a first packet data unit session and a second core network unit operable to serve a second terminal (second UE) allocated to a second packet data unit session) comprises receiving circuitry 31 , validating circuitry 32, deciding circuitry 33, and initiating circuitry 34. The receiving circuitry 31 receives a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session (in other words, the receiving circuitry 31 receives a request for relocation of said first packet data unit session to said second terminal orfor establishment of a third packet data unit session with the purpose of session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session). The validating circuitry 32 validates permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal. The deciding circuitry 33 decides on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating (of said validating circuitry 32). The initiating circuitry 34 initiates a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal. Figure 6 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 3 may perform the method of Figure 6 but is not limited to this method. The method of Figure 6 may be performed by the apparatus of Figure 3 but is not limited to being performed by this apparatus.

As shown in Figure 6, a procedure (of a network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session) according to exemplary embodiments of the present invention comprises an operation of receiving (S61 ) a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, an operation of validating (S62) permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal, an operation of deciding (S63) on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and an operation of initiating (S64) a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal.

Figure 4 is a block diagram illustrating a network system 30 according to exemplary embodiments of the present invention. In particular, Figure 4 illustrates a variation of the network system 30 shown in Figure 3. The network system 30 according to Figure 4 may thus further comprise obtaining circuitry 41 , forwarding circuitry 42, updating circuitry 43, and/or transmitting circuitry 44.

In an embodiment at least some of the functionalities of the network system shown in Figure 3 (or 4) may be shared between two (or more) physically separate devices forming one operational entity. Therefore, the network system may be seen to depict the operational entity comprising one or more physically separate devices (or units) for executing at least some of the described processes. Such shared architecture, may comprise e.g. one or more gNB(s) (5G NodeB), one or more AMF(s) (Access and Mobility Management Function), one or more SMF(s) (Session Management Function), one or more UPF(s) (User Plane Function), and/or one or more CN(s) (Core Network).

According to exemplary embodiments of the present invention, said request is indicative of said first packet data unit session.

According to further exemplary embodiments of the present invention, said request includes at least one information item of first information.

According to still further exemplary embodiments of the present invention, said first information comprises at least one of a permanent or temporary identity of said first terminal, redundancy related information, a global packet data unit session identity of said first packet data unit session, credential related information for validation of permission of said second terminal, an identifier of a network entity terminating and/or serving said first packet data unit session allocated to said first terminal, and packet data unit session configuration related information.

According to a variation of the procedure shown in Figure 6, exemplary details of the receiving operation (S61 ) are given, which are inherently independent from each other as such. Such exemplary receiving operation (S61 ) according to exemplary embodiments of the present invention may comprise an operation of obtaining, from said second terminal, a non access stratum message as said request via said second radio access network node and said second core network unit serving said second terminal, and/or obtaining, from said second terminal, utilizing a radio access network context of said first terminal, a terminal context update indication as said request via said first radio access network node and said first core network unit serving said first terminal and forwarding said request towards said second core network unit serving said second terminal.

According to a variation of the procedure shown in Figure 6, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to exemplary embodiments of the present invention may comprise an operation of updating a packet data unit session context of said first packet data unit session to allocate said first packet data unit session to said second terminal.

According to a variation of the procedure shown in Figure 6, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to exemplary embodiments of the present invention may comprise an operation of transmitting, by said first core network unit, first capability information on a packet data unit session relocation capability of a first core network terminating said first packet data unit session and/or, by said second core network unit, second capability information on a packet data unit session relocation capability of a second core network terminating said second packet data unit session.

In more specific terms, in general, according to exemplary embodiments of the present invention, a PDU session allocated to a first UE (first terminal) is allowed to be relocated (handed over) to a second UE (second terminal) based on a request from the second UE and thus recovers from the failure of the first UE and re-establishes the redundancy in the system.

In detail, based on the network capability and, when the UEs comprise parts of a mobile device, in-device coordination capability, the second UE may determine to request the PDU session recovery using PDU session relocation procedures according to exemplary embodiments of the present invention.

The in-device coordination requires UE contexts related to PDU sessions of the host device (Host A in Figures 9, 1 1 ) in both CN and RAN be recorded and shared among the UEs in the same device.

In case of a hardware (HW) failure of the first UE, the second UE may request to relocate the existing PDU session of the first UE by indicating the relevant PDU session to the network (NW). The relocation request may be sent as the dedicated PDU session relocation request message, or as the enhanced PDU session establishment request but with one or more of the following: the indication of PDU session relocation, a reference to existing PDU session, or at least a part of configuration parameters and attributes of existing PDU session.

Upon receiving either a PDU session establishment request for a PDU session relocation message or a PDU session relocation request message, the NW authenticates the second UE and relocates the existing PDU session of the first UE to the second UE based on indicated PDU session information.

Figure 12 shows a schematic diagram of signaling sequences according to exemplary embodiments of the present invention.

In particular, Figure 12 illustrates a scenario of deploying two UEs (UE1 and UE2) in the same host device to offer redundant user plane paths. When UE1 has a HW failure, the PDU session of UE1 is transferred/relocated to the UE2. However, exemplary embodiments of the present invention are not limited to a host having (only) two UEs but can also be applied for the case of having more than two UEs.

Figure 13 shows a more detailed schematic diagram of signaling sequences according to exemplary embodiments of the present invention,

The PDU session relocation procedure according to exemplary embodiments is used to relocate PDU session from the one UE (UE1 ) to the another UE (UE2). The procedure requires in-device coordination for sharing UE context information between the UEs. Although the coordination is shown as a single step in Figure 12 and also Figure 13 (step 3 of Figure 13), the context sharing is a continuous process.

According to exemplary embodiments of the present invention, the network indicates the support for this procedure to UE (steps 4 and 5 of Figure 13), which can be done during PDU session establishment or the network (SMF) could send an indication when the procedure is enabled if such control is desirable. According to exemplary embodiments of the present invention, the network also provides credentials that are later used for authentication and authorization during PDU session relocation procedure. That is, to facilitate the failure recovery decision making by UE2, the NW indicates the capability of supporting fast PDU session resumption by transferring/relocating the PDU session from one UE to another. The indication may be delivered to the UE during PDU session establishment procedure in PDU SESSION ESTABLISMENT ACCEPT message. Based on such capability indication as well as the device capability on supporting the in-device coordination on UE contexts or not, UE2 may determine to recover the failure of UE1 by requesting to relocate the existing PDU session of UE1. Further triggers or criteria for selecting fast recovery procedure according to the present invention may include Quality of Service (QoS) requirements of the services the PDU sessions are serving, which UE2 may have full knowledge of.

In order to enable UE2 to request the fast resumption of the existing PDU session of UE1 , the in-device coordination on the UE contexts storing and sharing for each PDU session is supported according to exemplary embodiments of the present invention.

Then, based on the received capability indication and in-device coordination of UE contexts, host or UE2 - depending on implementation - may determine to request PDU Session relocation and thus recover the existing PDU Session of UE1 using the stored information of UE1.

As part of the in-device coordination, the stored information may include the following:

1. A temporary or permanent UE identity (allocated in CN and/or RAN) or other information which can be used by the network to identify the other UE (e.g. SUPI, 5G-GUTI, C-RNTI, TMSI) and PDU session (e.g. PDU Session ID, IP address, IPv6 prefix, Ethernet address, etc.) ("permanent or temporary identity of said first terminal"). The combination of UE identity and PDU session identity is a unique global PDU session identifier (the global PDU session identity may e.g. be a combination of SUPI, S-NSSAI and PDU session IDs) ("a global packet data unit session identity of said first packet data unit session").

2. Redundancy related information such as RSN (reliability sequence number), redundancy version, NRG (network reliability group)/RG number etc. ("redundancy related information"). The redundancy version used by the first UE and the second UE2 may be different. However, if the redundancy versions/RSNs used by the first and the second UE are the same, then the redundancy version of the PDU session belonging to the first UE may change during the relocation of the PDU session.

3. Credential related information such as the authentication credential, ciphering keys etc. ("credential related information for validation of permission of said second terminal"). For security reasons, for example to prevent any UE to request the PDU session relocation (handover), the first UE may need to share a secret with the second UE. The second UE provides the secret to the network that then can validate whether the second UE has been authorized by the first UE to request the PDU session relocation.

4. An identifier of RAN entity such as gNB ID, in general, an identifier of CN and RAN entity such as SMF, UPF, gNB etc., if such information is stored in the UE side as the UE context ("an identifier of a network entity terminating and/or serving said first packet data unit session allocated to said first terminal").

5. Other PDU session configuration related information such as the QoS flows, the radio bearer configuration, etc. ("packet data unit session configuration related information").

As can be seen in Figures 12 and 13, in case of a HW failure of UE1 (step 6 of Figure 13) and that UE2 decides to request the PDU session relocation from the NW (step 7 of Figure 13), according to exemplary embodiments of the present invention, the UE2 may send a non-access stratum (NAS) message (e.g. PDU session relocation) to the NW.

Namely, UE2 initiates the PDU session relocation procedure by transmission of a NAS message, which could be an enhanced PDU session establishment request, or a new PDU session relocation request introduced in line with the exemplary embodiments of the present invention (step 8 of Figure 13).

The content of the NAS message includes some of the stored UE context of UE1 such as the UE and PDU session identity of the existing PDU session of UE1 (the global PDU session identity of the existing PDU session of UE1 ), IP address, IPv6 prefix, Ethernet address, the redundancy related information, network slice information (S-NSSAI), etc. According to further exemplary embodiments of the present invention, the NAS message may be transmitted via radio connection between UE2 and its serving RAN node (e.g. gNB2 in Figure 9). UE2 could indicate to gNB2 in the same message that carries the NAS message or other RRC message that SM (session management) procedure for PDU session relocation/recovery is ongoing and provide gNB1 identity, PDU session identity and UE1 identity within the message.

Based on provided RAN level information (e.g. gNB1 ID, UE1 C-RNTI), the dual connectivity of UE2 over the RAN can be quickly (pre-)established in parallel with the CN procedures either by using the allocated resources and RAN configuration of UE1 or by quickly releasing UE1’s resources and re-allocating them to UE2.

Alternatively, UE2 may use the available UE1’s RAN level context (e.g. C-RNTI, timing advance info, RB configurations, scheduling request configuration, UL grant etc.) to send necessary RAN level control message (an indication (e.g. either as physical layer signaling or in the form of MAC control PDU/Control Element or even as RRC signaling)) to gNB1 to update the UE context for (pre-)establishing the dual connectivity while CN procedures on PDU session relation is ongoing.

In either option, if only the RAN UE context is relocated/transferred from UE1 to UE2 and no need to update the RAN level configuration exists, the RRC signaling of dual connectivity configuration (e.g. the configuration of RBs in the secondary gNB) may be skipped.

Upon receiving the NAS message of requesting the PDU session relocation, the NW may authenticate UE2 based on the information provided by UE2 in the NAS messages and/or the pre-defined UE1 and UE2 subscription information (step 10 of Figure 13). If the PDU session relocation request can be accepted, the NW may update the PDU session context in CN and RAN to associate the existing PDU session to UE2 instead of UE1 (steps 12 to 16 of Figure 13). In this way, the same SMF, UPF, gNB and established N3 tunnel used by UE1 can be reused for UE2 to provide the redundant user plane paths with dual connectivity (steps 17 to 23 of Figure 13). According to exemplary embodiments of the present invention, the SMF is impacted in that support of new PDU session relocation procedure is necessary and in the ability for signaling of the support PDU session relocation to UE.

According to exemplary embodiments of the present invention, the RAN is impacted in that support of new indication to RAN about ongoing PDU session relocation procedure including an identity of serving RAN node of UE and UE’s identity may be advantageous.

According to exemplary embodiments of the present invention, the AMF (of the failed UE) is impacted e.g. by retrieval of information related to the failed UE’s context at NG interface by the new PDU session relocation procedure.

The above-described procedures and functions may be implemented by respective functional elements, processors, or the like, as described below.

In the foregoing exemplary description of network entities, only the units that are relevant for understanding the principles of the invention have been described using functional blocks. The network entities may comprise further units that are necessary for its respective operation. However, a description of these units is omitted in this specification. The arrangement of the functional blocks of the devices is not construed to limit the invention, and the functions may be performed by one block or further split into sub blocks.

When in the foregoing description it is stated that the apparatus, i.e. network entity/system (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that a (i.e. at least one) processor or corresponding circuitry, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured circuitry or means for performing the respective function (i.e. the expression “unit configured to" is construed to be equivalent to an expression such as“means for”). In Figure 14, an alternative illustration of apparatuses/systems according to exemplary embodiments of the present invention is depicted. As indicated in Figure 14, according to exemplary embodiments of the present invention, the apparatus (host) 10’ (corresponding to the host 10) comprises a processor 141 , a memory 142 and an interface 143, which are connected by a bus 144 or the like. Further, according to exemplary embodiments of the present invention, the network system 30’ (corresponding to the network system 30) comprises processor(s) 151 , 155, memory (memories) 152, 156 and interface(s) 153, 157, which are connected by bus(ses) 154, 158 or the like, and the apparatus and the network system may be connected via links 145, 146, respectively.

The processor 141/151/155 and/or the interface 143/153/157 may also include a modem or the like to facilitate communication over a (hardwire or wireless) link, respectively. The interface 143/153/157 may include a suitable transceiver coupled to one or more antennas or communication means for (hardwire or wireless) communications with the linked or connected device(s), respectively. The interface 143/153/157 is generally configured to communicate with at least one other apparatus, i.e. the interface thereof.

The memory 142/152/156 may store respective programs assumed to include program instructions or computer program code that, when executed by the respective processor, enables the respective electronic device or apparatus to operate in accordance with the exemplary embodiments of the present invention.

In general terms, the respective devices/apparatuses (and/or parts thereof) may represent means for performing respective operations and/or exhibiting respective functionalities, and/or the respective devices (and/or parts thereof) may have functions for performing respective operations and/or exhibiting respective functionalities.

When in the subsequent description it is stated that the processor (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that at least one processor, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured means for performing the respective function (i.e. the expression“processor configured to [cause the apparatus to] perform xxx-ing” is construed to be equivalent to an expression such as“means for xxx-ing”).

According to exemplary embodiments of the present invention, an apparatus representing the second terminal 10 (operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) comprises at least one processor 141 , at least one memory 142 including computer program code, and at least one interface 143 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 141 , with the at least one memory 142 and the computer program code) is configured to perform storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal (thus the apparatus comprising corresponding means for storing), to perform detecting a predetermined failure of said first terminal (thus the apparatus comprising corresponding means for detecting), to perform deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session (thus the apparatus comprising corresponding means for deciding), and to perform transmitting said request based on said first information (thus the apparatus comprising corresponding means for transmitting).

The apparatus representing the second terminal 10 (operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) may be embodied by an apparatus representing the host device 150 including the first terminal and the second terminal 10. The apparatus representing the host device 150 may thus comprise at least one processor 141 , at least one memory 142 including computer program code, and at least one interface 143 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 141 , with the at least one memory 142 and the computer program code) is configured to perform storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal (thus the apparatus comprising corresponding means for storing), to perform detecting a predetermined failure of said first terminal (thus the apparatus comprising corresponding means for detecting), to perform deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session (thus the apparatus comprising corresponding means for deciding), and to perform transmitting said request based on said first information (thus the apparatus comprising corresponding means for transmitting).

According to exemplary embodiments of the present invention, a network system 30 (including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session) comprises at least one processor 151/155, at least one memory 152/156 including computer program code, and at least one interface 153/157 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 151/155, with the at least one memory 152/156 and the computer program code) is configured to perform receiving a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session (thus the apparatus comprising corresponding means for receiving), to perform validating permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal (thus the apparatus comprising corresponding means for validating), to perform deciding on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating (thus the apparatus comprising corresponding means for deciding), and to perform initiating a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal (thus the apparatus comprising corresponding means for initiating).

For further details regarding the operability/functionality of the individual apparatuses, reference is made to the above description in connection with any one of Figures 1 to 13, respectively.

For the purpose of the present invention as described herein above, it should be noted that

- method steps likely to be implemented as software code portions and being run using a processor at a network server or network entity (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module(s) thereof, (e.g., devices carrying out the functions of the apparatuses according to the embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;

- devices, units or means (e.g. the above-defined network entity or network register, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved; - an apparatus like the user equipment and the network entity /network register may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof. The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are applicable.

In view of the above, there are provided measures for packet data unit (PDU) session continuity in ultra-reliable low-latency communications (URLLC) scenarios. Such measures (of an apparatus implementing a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths) exemplarily comprise storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal, detecting a predetermined failure of said first terminal, deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting said request based on said first information.

Even though the invention is described above with reference to the examples according to the accompanying drawings, it is to be understood that the invention is not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

List of acronyms and abbreviations

3GPP 3rd Generation Partnership Project

AMF Access and Mobility Management Function

CN core network

gNB 5G NodeB

GUTI Globally Unique Temporary Identifier HW hardware

NAS Non-Access Stratum

NW network

PDU packet data unit

QoS Quality of Service

RAN radio access network

SMF Session Management Function

SUPI Subscriber Permanent Identifier

TMSI Temporary Mobile Subscriber Identity UE user equipment

UPF User Plane Function

URLLC ultra-reliable low-latency communications

Claims

1 . A method of a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the method comprising

storing first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal,

detecting a predetermined failure of said first terminal,

deciding, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and

transmitting said request based on said first information.

2. The method according to claim 1 , wherein

said request is indicative of said first packet data unit session, and/or said request includes at least one information item of said first information.

3. The method according to claim 1 or 2, further comprising

receiving a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal, and

configuring, if said relocation of said first packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said first packet data unit session for a first user plane path and said second packet data unit session for an already established second user plane path, or

configuring, if said establishment of said third packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said third packet data unit session for said first user plane path and said second packet data unit session for said already established second user plane path.

4. The method according to claim 3, wherein

in relation to said configuring, the method further comprises

setting up, if said relocation of said first packet data unit session is acknowledged, a first user plane path on said first packet data unit session, or

setting up, if said establishment of said third packet data unit session is acknowledged, said first user plane path on said third packet data unit session, and maintaining an established second user plane path on said second packet data unit session.

5. The method according to claim 3 or 4, wherein

in relation to said configuring, the method further comprises

adopting resources allocated to said first packet data unit session before transmitting said relocation request for said first user plane path.

6. The method according to any of claims 1 to 5, wherein

in relation to said transmitting, the method further comprises

sending, by said second terminal, a non access stratum message as said request to a radio access network node serving said second terminal, and/or

sending, by said second terminal, utilizing a radio access network context of said first terminal, a terminal context update indication as said request to a radio access network node serving said first terminal.

7. The method according to any of claims 1 to 6, further comprising

receiving first capability information on a packet data unit session relocation capability of a first core network terminating said first packet data unit session and/or second capability information on a packet data unit session relocation capability of a second core network terminating said second packet data unit session.

8. The method according to any of claims 1 to 7, wherein

said first information comprises at least one of

a permanent or temporary identity of said first terminal, redundancy related information,

a global packet data unit session identity of said first packet data unit session, credential related information for validation of permission of said second terminal, an identifier of a network entity terminating and/or serving said first packet data unit session allocated to said first terminal, and

packet data unit session configuration related information.

9. A method of an apparatus including a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the method comprising

detecting a predetermined failure of said first terminal,

transmitting said request based on said first information.

10. The method according to claim 9, wherein

1 1 . The method according to claim 9 or 10, further comprising

12. The method according to claim 1 1 , wherein

in relation to said configuring, the method further comprises

13. The method according to claim 1 1 or 12, wherein

in relation to said configuring, the method further comprises

14. The method according to any of claims 9 to 13, wherein

in relation to said transmitting, the method further comprises

15. The method according to any of claims 9 to 14, further comprising

16. The method according to any of claims 9 to 15, wherein

said first information comprises at least one of

a permanent or temporary identity of said first terminal,

redundancy related information,

packet data unit session configuration related information.

17. A method of a network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the method comprising

receiving a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session,

validating permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal,

deciding on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and

initiating a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal.

18. The method according to claim 17, wherein

said request is indicative of said first packet data unit session, and/or said request includes at least one information item of first information.

19. The method according to claim 18, wherein

said first information comprises at least one of

a permanent or temporary identity of said first terminal,

redundancy related information,

packet data unit session configuration related information.

20. The method according to any of claims 17 to 19, wherein

in relation to said receiving, the method further comprises

obtaining, from said second terminal, a non-access stratum message as said request at a radio access network node of said second core network unit serving said second terminal, and/or

obtaining, from said second terminal, utilizing a radio access network context of said first terminal, a terminal context update indication as said request at a radio access network node of said first core network unit serving said first terminal and forwarding said request towards said second core network unit serving said second terminal.

21 . The method according to any of claims 17 to 20, further comprising

updating a packet data unit session context of said first packet data unit session to allocate said first packet data unit session to said second terminal.

22. The method according to any of claims 17 to 21 , further comprising

transmitting, by said first core network unit, first capability information on a packet data unit session relocation capability of a first core network terminating said first packet data unit session and/or, by said second core network unit, second capability information on a packet data unit session relocation capability of a second core network terminating said second packet data unit session.

23. An apparatus implementing a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising

at least one processor,

at least one memory including computer program code, and

at least one interface configured for communication with at least another apparatus,

the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform:

detecting a predetermined failure of said first terminal,

transmitting said request based on said first information.

24. The apparatus according to claim 23, wherein

25. The apparatus according to claim 23 or 24, wherein

the at least one processor, with the at least one memory and the computer program code, being further configured to cause the apparatus to perform:

configuring, if said relocation of said first packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said first packet data unit session for a first user plane path and said second packet data unit session for an already established second user plane path, or configuring, if said establishment of said third packet data unit session is acknowledged, said second terminal for dual connectivity utilizing said third packet data unit session for said first user plane path and said second packet data unit session for said already established second user plane path.

26. The apparatus according to claim 25, wherein

in relation to said configuring, the at least one processor, with the at least one memory and the computer program code, being further configured to cause the apparatus to perform:

27. The apparatus according to claim 25 or 26, wherein

28. The apparatus according to any of claims 23 to 27, wherein

in relation to said transmitting, the at least one processor, with the at least one memory and the computer program code, being further configured to cause the apparatus to perform:

29. The apparatus according to any of claims 23 to 28, wherein the at least one processor, with the at least one memory and the computer program code, being further configured to cause the apparatus to perform:

30. The apparatus according to any of claims 23 to 29, wherein

said first information comprises at least one of

a permanent or temporary identity of said first terminal,

redundancy related information,

packet data unit session configuration related information.

31 . An apparatus implementing a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising

at least one processor,

at least one memory including computer program code, and

detecting a predetermined failure of said first terminal,

transmitting said request based on said first information.

32. The apparatus according to claim 31 , wherein

33. The apparatus according to claim 31 or 32, wherein

34. The apparatus according to claim 33, wherein

35. The apparatus according to claim 33 or 34, wherein

36. The apparatus according to any of claims 31 to 35, wherein

37. The apparatus according to any of claims 31 to 36, wherein

38. The apparatus according to any of claims 31 to 37, wherein

said first information comprises at least one of

a permanent or temporary identity of said first terminal,

redundancy related information,

a global packet data unit session identity of said first packet data unit session, credential related information for validation of permission of said second terminal, an identifier of a network entity terminating and/or serving said first packet data unit session allocated to said first terminal, and packet data unit session configuration related information.

39. A network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the network system comprising

at least one processor,

at least one memory including computer program code, and

40. The network system according to claim 39, wherein

41 . The network system according to claim 40, wherein

said first information comprises at least one of

packet data unit session configuration related information.

42. The network system according to any of claims 39 to 41 , wherein

in relation to said receiving, the at least one processor, with the at least one memory and the computer program code, being further configured to cause the apparatus to perform:

obtaining, from said second terminal, a non access stratum message as said request at a radio access network node of said second core network unit serving said second terminal, and/or

43. The network system according to any of claims 39 to 42, wherein

44. The network system according to any of claims 39 to 43, wherein

45. An apparatus implementing a second terminal operable in parallel with a first terminal of a host device with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising

storing circuitry configured to hold first information on said first packet data unit session allocated to said first terminal and second information on said second packet data unit session allocated to said second terminal,

detecting circuitry configured to detect a predetermined failure of said first terminal,

deciding circuitry configured to decide, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and

transmitting circuitry configured to transmit said request based on said first information.

46. An apparatus implementing a first terminal and a second terminal operable in parallel with a first packet data unit session allocated to said first terminal and a second packet data unit session allocated to said second terminal, said second terminal being configurable for dual connectivity allowing simultaneous operation of two user plane paths, the apparatus comprising

deciding circuitry configured to decide, based on said detecting, on transmission of a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session, and transmitting circuitry configured to transmit said request based on said first information.

47. A network system including a first core network unit operable to serve a first terminal allocated to a first packet data unit session and a second core network unit operable to serve a second terminal allocated to a second packet data unit session, the network system comprising

receiving circuitry configured to receive a request for relocation of said first packet data unit session to said second terminal or for establishment of a third packet data unit session to said second terminal, said third packet data unit session providing session continuity of said first packet data unit session or a higher layer session supported by said first packet data unit session,

validating circuitry configured to validate permission of said second terminal for said relocation of said first packet data unit session to said second terminal or said establishment of said third packet data unit session to said second terminal,

deciding circuitry configured to decide on said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal based on a result of said validating, and

initiating circuitry configured to initiate a relocation or establishment acknowledgement response acknowledging said relocation of said first packet data unit session or said establishment of said third packet data unit session to said second terminal.

48. A computer program product comprising computer-executable computer program code which, when the program is run on a computer, is configured to cause the computer to carry out the method according to any one of claims 1 to 8, 9 to 16, or 17 to 22.

49. The computer program product according to claim 48, wherein the computer program product comprises a computer-readable medium on which the computer-executable computer program code is stored, and/or wherein the program is directly loadable into an internal memory of the computer or a processor thereof.