Packet data unit session handling

Abstract

There is provided a method for handling a packet data unit (PDU) session in a network. The network comprises an access network (AN) and a core network (CN). The method is performed by a first node of the AN. The first node is configured to provide AN control plane (CP) functionality. The method comprises initiating (202) transmission of a first request for establishment of a PDU session towards a second node of the CN. The second node is configured to provide CN CP functionality and the first request comprises site information indicative of a site associated with a first user plane (UP) function of the AN. The method also comprises receiving (204), from the second node, a first response message comprising identifier information and co-location information. The identifier information is indicative of at least one third UP function selected to support the PDU session, and the at least one third UP function is selected based on the site information. The co-location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

Description

[0001] PACKET DATA UNIT SESSION HANDLING

[0002] Technical Field

[0003] The present disclosure relates to methods for handling a packet data unit (PDU) session in a network, and nodes configured to operate in accordance with those methods.

[0004] Background

[0005] Standardisation work is ongoing in next generation radio access network (NG-RAN) and fifth generation (5G) core (5GC). Some of this work relates to new radio (NR) access networks and new packet core networks (see, for example, third generation partnership project (3GPP) technical specification (TS) 23.501 and 3GPP TS 23.502).

[0006] Figure 1 shows a non-roaming 5G system architecture in reference point representation (see, for example, 3GPP TS 23.501 V18.1.0). Interaction between any two network functions (NFs) of Figure 1 is represented by a point-to-point reference point / interface.

[0007] The 5G network architecture shown in Figure 1 comprises a user equipment (UE) connected to either a radio access network (RAN) or an access network (AN) directly as well as an access and mobility management function (AMF) indirectly, for example, via the RAN or AN. Typically, the R(AN) comprises base stations, e.g. such as evolved Node Bs (eNBs) or 5G base stations (e.g. gNodeBs (gNBs)) or similar. The 5G core NFs shown in Figure 1 include a network slice-specific and standalone non-public network (SNPN) authentication and authorization function (NSSAAF), a network slice selection function (NSSF), an authentication server function (AUSF), a unified data management (UDM), a network slice admission control function (NSACF), an access and mobility management function (AMF), a session management function (SMF), a policy control function (PCF), an application function (AF), and a user plane function (UPF).

[0008] Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardisation. The N1 reference point is defined to carry signaling between UE and AMF. The reference points for connecting between AN and AMF and between AN and UPF are defined as N2 and N3, respectively. There is a reference point, N11 , between AMF and SMF, which implies that SMF is at least partly controlled by AMF. N4 is used by SMF and UPF so that the UPF can be set using the control signal generated by the SMF, and the UPF can report its state to the SMF. N9 is the reference point for the connection between different UPFs (e.g. that are chained in different ways), and N14 is the reference point connecting between different AMFs, respectively. N15 and N7 are defined since PCF applies policy to AMF and SMF, respectively. N12 is required for the AMF to perform authentication of the UE. N8 and N10 are defined because the subscription data of UE is required for AMF and SMF, respectively. N80 and N81 are reference points for connection between the NSACF and the AMF and SMF, respectively. N58 and N59 are reference points for connection between the NSSAAF and the AMF and UDM, respectively.

[0009] The 5G core network aims at separating user plane and control plane. The user plane carries user traffic while the control plane carries signaling in the network. In Figure 1 , the UPF is in the user plane and all other NFs, i.e., AMF, SMF, PCF, AF, AUSF, and UDM, are in the control plane. Separating the user and control planes guarantees each plane’s resources can be scaled independently. It also allows UPFs to be deployed separately from control plane functions in a distributed fashion.

[0010] Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the control plane, a set of interactions between two NFs is defined as a service so that its reuse is possible. This service enables support for modularity. The user plane supports interactions such as forwarding operations between different UPFs.

[0011] Figure 2 shows a 5G system architecture (see, for example, 3GPP TS 23.501 V18.1.0). The 5G system architecture shown in Figure 2 uses service-based interfaces between the NFs in the control plane, instead of the point-to-point reference points / interfaces used in the 5G network architecture of Figure 1. However, the NFs described above with reference to Figure 1 correspond to the NFs shown in Figure 2. The 5G system architecture of Figure 2 also includes an edge application server discovery function (EASDF). The service(s) that an NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 2, the service based interfaces are indicated by the letter “N” followed by the name of the NF, e.g. Namf for the service based interface of the AMF and Nsmf for the service based interface of the SMF etc.

[0012] Some properties of the NFs shown in Figures 1 and 2 may be described in the following manner. The AMF provides UE-based authentication, authorization, mobility management, etc. The SMF is responsible for session management and allocates internet protocol (IP) addresses to UEs. It also selects and controls the UPF for data transfer. If a UE has multiple sessions, different SMFs may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF provides information on the packet flow to the PCF responsible for policy control in order to support quality of service (QoS). Based on the information, PCF determines policies about mobility and session management to make AMF and SMF operate properly. The ALISF supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while UDM stores subscription data of UE. The data network (DN), not part of the 5G core network, provides Internet access or operator services and similar.

[0013] Figure 3 shows an internal architecture of a gNB. The gNB of Figure 3 can be a base station (BS) supporting NR radio access technology (RAT) in the (R)AN of Figures 1 and 2 (see, for example, 3GPP TS 38.401). The architecture illustrated in Figure 3 assumes that both higher layer split (HLS), and control plane and user plane split (CP-UP split), have been adopted within the gNB. The NG-RAN may also contain long term evolution (LTE) next generation eNodeBs (NG-eNBs) and the HLS may later be supported for NG- eNBs.

[0014] HLS means that the gNB is divided into a central unit (CU) and a distributed unit (DU). A CP-UP split further divides the CU into a CU control plane (CU-CP) and a CU user plane (CU-UP). This configuration is currently being standardised in 3GPP (see, for example, 3GPP technical report (TR) 38.806). CU-CP hosts a radio resource control (RRC) protocol and a packet data convergence protocol (PDCP) used for CP functionality. The CU-UP also hosts a service data adaptation protocol (SDAP) protocol and a PDCP used for UP functionality. CU-CP controls CU-UP via an E1 interface, as illustrated in Figure 3. Although not illustrated in Figure 3, the CU-CP is the function that terminates the N2 interface from the AMF in 5GC, and the CU-UP is the function terminating the N3 interface from the UPF in 5GC (e.g. in relation to Figures 1 and 2). Logically, a UE has one CU-UP per PDU session. Other terms used for N2 and N3 interfaces in 3GPP are next generation control (NG-C) plane interface (e.g. between a NG-RAN and a 5GC network) and next generation user (NG-U) plane interface (e.g. between a NG-RAN and a 5GC network), respectively. Figures 4 and 5 show examples of a baseline architecture illustrating an interface between an NG-RAN and a 5GC network. In more detail, Figure 4 illustrates an architecture comprising a single UPF, while Figure 5 illustrates an architecture comprising multiple UPFs.

[0015] Figures 4 and 5 can be described as a combined view of Figures 1 , 2 and 3, with the exception that Figures 4 and 5 illustrate only main functions (e.g. in the 5GC) for the process of UPF selection (e.g. AMF, SMF and UPF(s)). As illustrated in Figures 4 and 5, the interface between the AMF and SMF is an N11 interface. The N11 interface is used as an example only in Figure 4 and 5. The N11 interface can also be realised using service-based interfaces exhibited by AMF and SMF, e.g. Namf and Nsmf respectively.

[0016] Figure 5 shows the case with multiple UPFs connected via an N9 interface. The UPF closer to the NG-RAN may be deployed in a remote location providing local breakout functionality to a local service network with remotely deployed applications, e.g., in an edge / distributed cloud. The local breakout functionality may also be used for other purposes, such as access to external networks via a remotely deployed peering point. The other UPF (i.e. with the N6 interface) may be deployed in a central location.

[0017] There are currently different ways that UPF selection can be performed in 5GC and NG- RAN (also known as 5GC UPF and NG-RAN CU-U selection, respectively). However, in general, the SMF is in charge of performing UPF selection. For example, for protocol data unit (PDU) session establishment, the SMF usually provides information about the selected UPF to a CU-UP that performs CU-UP selection and configures the selected CU-UP with information received from the SMF about the selected UPF. The CU-UP then provides information about the selected CU-UP to the SMF that configures the UPF to finalize the N3 interface establishment for the PDU session.

[0018] However, there are certain challenges associated with existing techniques for handling UPF selection.

[0019] Summary

[0020] As mentioned above, there are certain challenges associated with existing techniques for handling UPF selection. In particular, some existing techniques assume that a single domain (e.g. RAN or CN) controls user plane (UP) functionality for each domain involved in the UPF selection process (e.g. the RAN domain controls the CN UP functionality, or vice-versa). However, such an assumption is contrary to the principle of domain separation in 3GPP, and in the network vendor community. Furthermore, some existing techniques assume that certain CP elements, such as the CU-CP and the SMF, are provided by the same vendor. However, in typical network deployments, RAN and CN domains are often provided by different vendors. As an example, a given public land mobile network (PLMN) may deploy different RAN areas by different vendors, and a single CN by a specific vendor. Thus, the communicating RAN and CN CP nodes may or may not be from different vendors. This limits the applicability of such existing techniques to only a few deployment scenarios.

[0021] It is an object of the disclosure to obviate or eliminate at least some of the above- mentioned disadvantages associated with existing techniques.

[0022] Therefore, according to an aspect of the disclosure, there is provided a first method for handling a packet data unit (PDU) session in a network. The network comprises an access network (AN) and a core network (CN). The method is performed by a first node of the AN. The first node is configured to provide AN control plane (CP) functionality. The first method comprises initiating transmission of a first request for establishment of a PDU session towards a second node of the CN. The second node is configured to provide CN CP functionality and the first request comprises site information indicative of a site associated with a first user plane (UP) function of the AN. The first method also comprises receiving, from the second node, a first response message comprising identifier information and co-location information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information. The co-location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

[0023] According to another aspect of the disclosure, there is provided a second method for handling a PDU session in a network. The network comprises an AN and a CN. The second method is performed by a second node of the CN. The second node is configured to provide CN CP functionality. The second method comprises receiving from a first node of the AN, a first request for establishment of a PDU session. The first request comprises site information indicative of a site associated with a first UP function of the AN. The first node is configured to provide AN CP functionality. The second method also comprises initiating transmission of a first response message towards the first node. The first response message comprises identifier information and location information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information. The location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

[0024] According to another aspect of the disclosure, there is provided a third method for handling a PDU session in a network. The network comprises an AN and a CN. The third method is performed by at least one control node of the network. The at least one control node is configured to provide UP control functionality. The third method comprises determining that a second UP function of the AN and at least one third UP function are to be co-located in the network. The at least one third UP function is selected to support a PDU session. The third method also comprises configuring the second UP function and the at least one third UP function to support the PDU session in a co-location configuration.

[0025] According to another aspect of the disclosure, there is also provided a first node comprising processing circuitry configured to operate in accordance with the first method. In some embodiments, the first node may comprise at least one memory for storing instructions which, when executed by the processing circuitry, cause the first node to operate in accordance with the first method.

[0026] According to another aspect of the disclosure, there is also provided a second node comprising processing circuitry configured to operate in accordance with the second method. In some embodiments, the second node may comprise at least one memory for storing instructions which, when executed by the processing circuitry, cause the second node to operate in accordance with the second method.

[0027] According to another aspect of the disclosure, there is also provided a control node comprising processing circuitry configured to operate in accordance with the third method. In some embodiments, the control node may comprise at least one memory for storing instructions which, when executed by the processing circuitry, cause the control node to operate in accordance with the third method. According to another aspect of the disclosure, there is provided a method performed by a system. The method comprises any two or more of the first, second and third methods.

[0028] According to another aspect of the disclosure, there is provided a system comprising any two or more of a first node as described earlier, a second node as described earlier, and a control node as described earlier.

[0029] According to another aspect of the disclosure, there is provided a computer program comprising instructions which, when executed by processing circuitry, cause the processing circuitry to perform any one or more of the first, second and third methods.

[0030] According to another aspect of the disclosure, there is provided a computer program product, embodied on a non-transitory machine-readable medium, comprising instructions which are executable by processing circuitry to cause the processing circuitry to perform any one or more of the first, second and third methods.

[0031] Thus, in the manner described above, improved techniques for handling a packet data unit (PDU) session in a network are provided. Advantageously, the techniques enable the co-location of an AN (e.g. radio access network (RAN)) user plane (UP) function and a core network (CN) UP function. In this way, the techniques disclosed herein make it possible to reduce UP latency, increase performance (e.g. in the network), and simplify functionality on the UP. The techniques are especially advantageous in scenarios which involve, for example, enhanced mobile broadband (eMBB), massive machine type communication (MTC) and critical MTC. Furthermore, the techniques disclosed herein can be applied on top of the existing 3GPP architecture, and thus require minor updates to the current architecture. Moreover, the improved techniques provide for the possibility of an AN and a CN being provided by different vendors (e.g. RAN CP functions and CN CP functions being from different vendors).

[0032] Brief description of the drawings

[0033] For a better understanding of the techniques, and to show how they may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

[0034] Figure 1 schematically shows a non-roaming network architecture using reference point representation; Figure 2 schematically shows a 5G network architecture using service-based interfaces between network functions (NFs);

[0035] Figure 3 is a block diagram illustrating an internal architecture of a gNB;

[0036] Figures 4 and 5 show examples of a baseline architecture illustrating an interface between an NG-RAN and a 5GC network.

[0037] Figure 6 is a signalling diagram illustrating an example exchange of signals according to an existing technique for user plane function (UPF) selection;

[0038] Figure 7 illustrates an example system for performing UPF selection according to an existing technique;

[0039] Figure 8 is a signalling diagram illustrating an example exchange of signals according to an existing technique for UPF selection;

[0040] Figure 9 illustrates an example system for performing UPF selection according to an existing technique;

[0041] Figure 10 is a signalling diagram illustrating an example exchange of signals according to an existing technique for UPF selection;

[0042] Figure 11 is a block diagram illustrating a first node according to an embodiment;

[0043] Figure 12 is a block diagram illustrating a method performed by the first node according to an embodiment;

[0044] Figure 13 is a block diagram illustrating a second node according to an embodiment;

[0045] Figure 14 is a block diagram illustrating a method performed by the second node according to an embodiment;

[0046] Figure 15 is a block diagram illustrating a control node according to an embodiment; Figure 16 is a block diagram illustrating a method performed by the control node according to an embodiment; and

[0047] Figure 17 is a signalling diagram illustrating a method performed by a system according to an embodiment;

[0048] Figures 18 and 19 are schematic illustrations of a system according to some embodiments; and

[0049] Figure 17 is a signalling diagram illustrating a method performed by a system according to an embodiment.

[0050] Detailed Description

[0051] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0052] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject-matter disclosed herein, the disclosed subject-matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject-matter to those skilled in the art.

[0053] As described earlier, there are described herein improve techniques for handling a PDU session in a network. The network comprises an access network (AN) and core network (CN). The network referred to herein can be any type of network. For example, the network referred to herein may be a communications or telecommunications network. In some embodiments, the network referred to herein can be a mobile network, such as a fifth generation (5G) mobile network or any other generation mobile network (e.g. 6G). In some embodiments, the CN referred to herein can be a 5G core (5GC) network, and / or the AN referred to herein can be a radio access network (RAN). In some embodiments, the network referred to herein can be a virtual network or an at least partially virtual network. Although some examples have been provided for the type of network referred to herein, it will be understood that the network referred to herein can be any other type of network which comprises an AN and a CN.

[0054] Some of the nodes and / or entities referred to herein are described in terms used in the current 5G architecture. However, it will be understood that this is merely an example description of aid nodes and / or entities, and that the techniques described herein are applicable to any current and future (e.g. mobile) network architecture (e.g. a 6G architecture).

[0055] In order to aid the understanding of techniques described herein, and the associated technical advantages, an example of some existing techniques will first be described.

[0056] Figure 6 is a signalling diagram illustrating an existing technique for user plane function (UPF) selection in a network. The network illustrated in Figure 6 comprises a user equipment (UE) 102 (“NG-LIE”), a distributed unit (DU) 104, a control unit of a control plane (CU-CP) 106, a control unit of a user plane (CU-UP) 108, an access and mobility management function (AMF) 110, a UPF 112, and a session management function (SMF) 114. In the example illustrated in Figure 6, the network comprises a next generation (NG) RAN (NG-RAN) and a 5GC network. The UE 102, the DU 104, the CU- CP 106 and the CU-UP 108 are comprised in the RAN. The AMF 110, the UPF 112 and the SMF 114 are comprised in the 5GC network.

[0057] As illustrated in Figure 6, the UE 102 requests PDU session establishment (“PDU Session Establishment Request”) to the AMF 110. As also illustrated in Figure 6, the UPF 112 is first selected by the SMF 114 (“UPF Selection”) in the 5GC network. As illustrated in Figure 6, the SMF 114 then provides information about the selected UPF 112 (“UPF Transport Address and TEID”) to the CU-CP 106. The CU-CP 106 then performs CU-UP selection (“CU-UP Selection”) and configures the selected CU-UP 108 with the information received from SMF 114 about the selected UPF 112. The CLI-CP 106 then provides information about the selected CU-LIP 108 (“CU-LIP Transport Address and TEID”) to the SMF 114. The SMF 114 configures the UPF 112 with the received information to finalize an N3 interface establishment for the PDU session. Thus, Figure 6 illustrates a method for selecting a single UPF function by an SMF 114.

[0058] However, in the method performed by the system illustrated in Figure 6, the UPF 112 and the CU-UP 108 are selected independently of each other. Moreover, the UPF 112 and the CU-UP 108 are configured using separate interfaces (i.e. the UPF 112 is configured by the SMF 114 using an N4 interface, and the CU-UP 108 is configured by the CU-CP 106 using an E1 interface).

[0059] Figure 7 illustrates an example system for performing UPF selection according to an existing technique. As illustrated in Figure 7, the system is in the form of a network comprising a NG-RAN and a 5GC network.

[0060] The methodology performed by the system of Figure 7 involves the combination of a user plane function for both the 5GC network UPF and the NG-RAN CU-UP. The combined user plane function results in the removal of a user plane tunnel between the UPF in the 5GC network and the CU-UP in the NG-RAN, as the N3 interface becomes an internal interface in the combined user plane function.

[0061] As illustrated in Figure 7, the combined user plane function is referred to as a Combined RAN and CN User Plane Function (CRC-UPF). The CRC-UPF is either selected and controlled by 5GC or NG-RAN (e.g. by the SMF or by the CU-CP of Figure 7, respectively). Information or indication(s) about the selected CRC-UPF is provided to the other domain (e.g. when selected by the SMF then the information or indication(s) is provided to the CU-CP, and vice versa). There are two main types of implementation associated with the system illustrated in Figure 7: a) CRC-UPF controlled by NG-RAN (i.e. the implementation of a “tunnelled N4 interface”), and b) CRC-UPF controlled by 5GC network (i.e. “tunnelled E1 interface”).

[0062] Thus, the exemplary technique illustrated by the system of Figure 7 provides for a configuration of the CRC-UPF to be controlled by different domains. Specifically, when the CRC-UPF is controlled by the SMF, then the CU-CP is enabled to configure the CU- UP of the CRC-UPF via a “tunnelled E1 interface”. Alternatively, when the CRC-UPF is controlled by the CLI-CP, then the SMF is enabled to configure the UPF part of the CRC- II PF via a “tunnelled N4 interface”. Figure 7 illustrates the overall architecture for a single UPF case in the “tunnelled N4 interface” embodiment mentioned above. Specifically, in the system illustrated in Figure 7, there is a single UPF as the UPF part of the CRC-UPF. In this case, the CRC-UPF supports an N6 interface to Data Network(s).

[0063] Figure 8 shows an exemplary signaling diagram for PDU session establishment as performed by the system illustrated in Figure 7.

[0064] Figure 9 illustrates an example system for performing UPF selection according to an existing technique. As illustrated in Figure 9, the system is in the form of a network comprising a NG-RAN and a 5GC network.

[0065] The method performed by the system illustrated in Figure 9 attempts to avoid the main drawback of the method performed by the system illustrated in Figure 7. That is, that a single domain (i.e. RAN or CN) controls the UP functionality belonging to the other domain, which is against the domain separation principle in 3GPP and in the vendor community.

[0066] In the method performed by the system of Figure 9, the CRC-UPF is either selected and controlled by the 5GC network or the NG-RAN (e.g., by the SMF or the CU-CP, respectively). As such, information about the selected combined UPF is provided to the other domain (e.g., when the CRC-UPF is selected by the CU-UP, then information is provided to the SMF, and vice versa). The information provided consists of an interface address and a user plane context information. For example, when the CRC-UPF is selected by the CU-CP, then the interface address information is for the N4 interface termination in the CRC-UPF selected by the CU-CP, and the user plane context information indicates the user plane context in the UPF part of the CRC-UPF is to be configured via the N4 interface. When the information is received, it is used to select and configure the other part of the CRC-UPF (e.g. when information is received by the SMF, the SMF uses the received N4 interface address and user plane context information to configure the UPF part of the CRC-UPF). The combined user plane function also results in the removal of the user plane tunnel between 5GC and NG-RAN, as the N3 interface becomes an internal interface in the combined user plane function. Therefore, Figure 9 shows an overall architecture for selection of a single UPF (i.e. there is a single UPF associated with the UPF part of the CRC-UPF). In this case, the CRC- UPF supports N6 interface to Data Network(s).

[0067] Figure 10 is a signalling diagram illustrating an example exchange of signals according to the existing technique performed by the system illustrated in Figure 9.

[0068] However, the existing technique as described with reference to Figures 7 and 8 presents challenges in that the technique assumes that a single domain (e.g. RAN or CN) controls UP functionality belonging to the other domain of the relevant system. Such an assumption conflicts with the domain separation principle in 3GPP and the vendor community.

[0069] Furthermore, the existing technique as described with reference to Figures 9 and 10 still assumes that two CP elements (e.g. a CU-CP and SMF, respectively) are provided by the same vendor. However, in typical network deployments, the RAN and CN domains are associated with (e.g. provided by) different vendors. In general, a given public land mobile network (PLMN) may deploy different RAN areas by different vendors, and a single CN by a certain (e.g. different) vendor. Thus, the communicating RAN CP nodes and CN CP nodes may or may not be from different vendors. This limits the applicability of this existing technique to only a few deployment scenarios.

[0070] The improved techniques described herein address the challenges associated with existing techniques, such as those illustrated in Figures 7 to 10. In particular, the improved techniques discussed herein enable the selection of co-located AN UP functions and CN UP functions in a (e.g. telecommunications) network for establishing a PDU session.

[0071] Figure 11 illustrates a first node 10 of a network in accordance with an embodiment. The first node 10 is for handling a packet data unit (PDU) session in a network. In some embodiments, the first node 10 referred to herein can refer to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with the second node referred to herein, the at least one control node referred to herein, and / or with other nodes or equipment to enable and / or to perform the functionality described herein. In some embodiments, the first node 10 referred to herein can, for example, be a physical node (e.g. a physical machine or server) or a virtual node (e.g. a virtual machine, VM). The first node 10 is configured to provide access network (AN) control plane (CP) functionality. The first node 10 may be, and / or comprise, a control unit control plane (CLI-CP) node and / or a RAN UP node.

[0072] As illustrated in Figure 11 , the first node 10 comprises processing circuitry (or logic) 12. The processing circuitry 12 controls the operation of the first node 10 and can implement the method described herein in respect of the first node 10. The processing circuitry 12 can be configured or programmed to control the first node 10 in the manner described herein. The processing circuitry 12 can comprise one or more hardware components, such as one or more processors, one or more processing units, one or more multi-core processors and / or one or more modules. In particular implementations, each of the one or more hardware components can be configured to perform, or is for performing, individual or multiple steps of the method described herein in respect of the first node 10. In some embodiments, the processing circuitry 12 can be configured to run software to perform the method described herein in respect of the first node 10. The software may be containerised according to some embodiments. Thus, in some embodiments, the processing circuitry 12 may be configured to run a container to perform the method described herein in respect of the first node 10.

[0073] Briefly, the processing circuitry 12 of the first node 10 is configured to initiate transmission of a first request for establishment of a packet data unit (PDU) session towards a second node of a core network (CN). The second network node is configured to provide CN control plane (CP) functionality and the first request comprises site information indicative of a site associated with a first user plane (UP) function of an access network (AN). The processing circuitry 12 of the first node 10 is also configured to receive, from the second node, a first response message comprising identifier information and co-location information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information. The co-location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

[0074] As illustrated in Figure 11 , in some embodiments, the first node 10 may optionally comprise a memory 14. The memory 14 of the first node 10 can comprise a volatile memory or a non-volatile memory. In some embodiments, the memory 14 of the first node 10 may comprise a non-transitory media. Examples of the memory 14 of the first node 10 include, but are not limited to, a random access memory (RAM), a read only memory (ROM), a mass storage media such as a hard disk, a removable storage media such as a compact disk (CD) or a digital versatile disk (DVD), and / or any other memory.

[0075] The processing circuitry 12 of the first node 10 can be communicatively coupled (e.g. connected) to the memory 14 of the first node 10. In some embodiments, the memory 14 of the first node 10 may be for storing program code or instructions which, when executed by the processing circuitry 12 of the first node 10, cause the first node 10 to operate in the manner described herein in respect of the first node 10. For example, in some embodiments, the memory 14 of the first node 10 may be configured to store program code or instructions that can be executed by the processing circuitry 12 of the first node 10 to cause the first node 10 to operate in accordance with the method described herein in respect of the first node 10. Alternatively or in addition, the memory 14 of the first node 10 can be configured to store any information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. The processing circuitry 12 of the first node 10 may be configured to control the memory 14 of the first node 10 to store any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein.

[0076] In some embodiments, as illustrated in Figure 11 , the first node 10 may optionally comprise a communications interface 16. The communications interface 16 of the first node 10 can be communicatively coupled (e.g. connected) to the processing circuitry 12 of the first node 10 and / or the memory 14 of the first node 10. The communications interface 16 of the first node 10 may be operable to allow the processing circuitry 12 of the first node 10 to communicate with the memory 14 of the first node 10 and / or vice versa. Similarly, the communications interface 16 of the first node 10 may be operable to allow the processing circuitry 12 of the first node 10 to communicate with any one or more nodes (e.g. the second node referred to herein, and / or the at least one control node referred to herein) referred to herein and / or any other node. The communications interface 16 of the first node 10 can be configured to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. In some embodiments, the processing circuitry 12 of the first node 10 may be configured to control the communications interface 16 of the first node 10 to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. Although the first node 10 is illustrated in Figure 11 as comprising a single memory 14, it will be appreciated that the first node 10 may comprise at least one memory (i.e. a single memory or a plurality of memories) 14 that operate in the manner described herein. Similarly, although the first node 10 is illustrated in Figure 11 as comprising a single communications interface 16, it will be appreciated that the first node 10 may comprise at least one communications interface (i.e. a single communications interface or a plurality of communications interfaces) 16 that operate in the manner described herein. It will also be appreciated that Figure 11 only shows the components required to illustrate an embodiment of the first node 10 and, in practical implementations, the first node 10 may comprise additional or alternative components to those shown.

[0077] Figure 12 illustrates a method performed by the first node 10 of a network in accordance with an embodiment. The method is for handling a PDU session in a network. The network comprises an AN and a CN. The first node 10 described earlier with reference to Figure 11 can be configured to operate in accordance with the method of Figure 12. The method can be performed by or under the control of the processing circuitry 12 of the first node 10 according to some embodiments.

[0078] With reference to Figure 12, as illustrated at block 202, transmission of a first request for establishment of a PDU session is initiated towards a second node of the CN. More specifically, the first node 10 (e.g. the processing circuitry 12 of the first node 10) initiates transmission of the first request. Herein, the term “initiate” can mean, for example, cause or establish. Thus, the first node 10 (e.g. the processing circuitry 12 of the first node 10) can be configured to itself transmit the first request (e.g. via the communications interface 16 of the first node 10) or can be configured to cause another entity to transmit the first request. The second node is configured to provide CN CP functionality. The first request comprises site information indicative of a site associated with a first UP function of the AN.

[0079] As described herein, the first node 10 is configured to provide AN CP functionality. Therefore, in some examples, the first node 10 may comprise, and / or may be configured to operates as, a CU-CP node and / or a RAN UP node. The second node is configured to provide CN CP functionality. For example, the second node may be a SMF node of the CN. The first UP function of the AN may be a distributed unit (DU) (e.g. of a gNB). For example, the first UP function may be a distributed unit as described with reference to Figure 3 above. As illustrated at block 204 of Figure 12, a first response message is received from the second node. The first response message comprises identifier information and colocation information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information, and the co-location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred. The at least one third UP function may comprise at least one UPF. The second UP function of the AN may comprise a control unit control plane (CU-CP) node.

[0080] Although not illustrated in Figure 12, in some examples, the method may comprise determining, prior to initiating transmission of the first request, the site associated with the first UP function. More specifically, the first node 10 (e.g. the processing circuitry 12 of the first node 10) may determine the site associated with the first UP function. Determining the site associated with the first UP function may comprise selecting the site associated with the first UP function. Alternatively, or in addition, determining the site associated with the first UP function may comprise identifying the site associated with the first UP function. For example, before sending the first request, the first node 10 (e.g. CU-CP node) may identify the site (e.g. the location in the network) associated with the first UP function (e.g. DU). In some examples, before sending the first request, the first node (e.g. RAN UP node) may (pre)select the site (e.g. the location in the network) associated with the first UP function.

[0081] In some examples, the first node 10 may comprise the first UP function. For example, in scenarios in which the first node 10 is a RAN UP node, then the first node 10 may comprise the first UP function (e.g. DU).

[0082] Although not illustrated in Figure 12, in some examples, the method may comprise selecting, based on the identifier information and the co-location information, a first entity of the AN to be configured to support the PDU session. More specifically, the first node 10 (e.g. the processing circuitry 12 of the first node 10) may select the first entity. The first entity of the AN may comprise the second UP function referred to herein. For example, the first entity may be the second UP function (e.g. a control unit user plane (CU-UP) node of the AN). In some examples, the first entity may be the first node 10. For example, in examples in which the first node 10 is a RAN UP node, the first entity may be the first node 10. In some examples in which the first node 10 is a RAN UP node, the first entity may be a different RAN UP node (e.g. to the first node 10). As such, in some examples in which the first node 10 is a RAN UP node, selecting the first entity may comprise selecting the first node 10 (e.g. if it comprises the second UP function), or selecting an other RAN UP node (e.g. if the other RAN UP node comprises the second UP function), to be configured to support the PDU session.

[0083] In some examples, selecting the first entity may depend on the co-location information. For example, if the co-location information is indicative that co-location of the at least one third UP function (e.g. UPF) and the second UP function (e.g. CU-UP) is not preferred, selecting the first entity of the AN may comprise selecting the first entity based on one or more policies configured for the AN. The one or more policies configured for the AN may comprise one or more RAN-internal policies. For example, the one or more policies configured for the AN may comprise a policy to (e.g. always) co-locate the second UP function (e.g. CU-UP) with the first UP function (e.g. DU). As such, the selection of the first entity (e.g. which can comprise the second UP function) may be selected such that the first entity is situated at the same site as the first UP function (e.g. DU)

[0084] In some examples, if the co-location information is indicative that co-location of the at least one third UP function and the second UP function is preferred, selecting the first entity of the AN may comprise selecting a first entity of the AN that is associated with the site associated with the at least one third UP function. Therefore, if co-location of the at least one third UP function and the second UP function is preferred, the first node 10 may (e.g. attempt to) select the same site for the first entity (e.g. the second UP function) as the site associated with the at least one third UP function (e.g. UPF).

[0085] In some examples, the first entity of the AN can be selected to establish a UP tunnel between the first entity (e.g. second UP function) and the at least one third UP function. For example, the first entity may be selected to be (e.g. later) configured to establish the UP tunnel.

[0086] In some examples, initiating transmission of the first request may comprise initiating transmission of the first request towards the second node via a first CN function. Although not illustrated in Figure 12, in some examples, receiving the first response message may comprise receiving the first response message from the second node via the first CN function (e.g. AMF). The first CN function can be configured to operate as an access and mobility management function (AMF). For example, the first CN function may be an AMF of the CN, and / or the first CN function may be an AMF comprised in a (e.g. AMF) node of the CN.

[0087] Figure 13 illustrates a second node 20 of a network in accordance with an embodiment. The second node 20 is for handling a PDU session in a network. In some embodiments, the second node 20 referred to herein can refer to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with the first node 10 referred to herein, the at least one control node referred to herein, and / or with other nodes or equipment to enable and / or to perform the functionality described herein. In some embodiments, the second node 20 referred to herein can, for example, be a physical node (e.g. a physical machine or server) or a virtual node (e.g. a virtual machine, VM). The second node 20 may be a SMF node, and / or be configured to operate as an SMF.

[0088] As illustrated in Figure 13, the second node 20 comprises processing circuitry (or logic) 22. The processing circuitry 22 controls the operation of the second node 20 and can implement the method described herein in respect of the second node 20. The processing circuitry 22 can be configured or programmed to control the second node 20 in the manner described herein. The processing circuitry 22 can comprise one or more hardware components, such as one or more processors, one or more processing units, one or more multi-core processors and / or one or more modules. In particular implementations, each of the one or more hardware components can be configured to perform, or is for performing, individual or multiple steps of the method described herein in respect of the second node 20. In some embodiments, the processing circuitry 22 can be configured to run software to perform the method described herein in respect of the second node 20. The software may be containerised according to some embodiments. Thus, in some embodiments, the processing circuitry 22 may be configured to run a container to perform the method described herein in respect of the second node 20.

[0089] Briefly, the processing circuitry 22 of the second node 20 is configured to receive, from a first node 10 of an AN, a first request for establishment of a PDU session. The first request comprises site information indicative of a site associated with a first UP function of the AN. The first node 10 is configured to provide AN CP functionality, as described herein. The processing circuitry 22 of the second node 20 is also configured to initiate transmission of a first response message towards the first node 10. The first response message comprises identifier information and location information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information, and the location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

[0090] As illustrated in Figure 13, in some embodiments, the second node 20 may optionally comprise a memory 24. The memory 24 of the second node 20 can comprise a volatile memory or a non-volatile memory. In some embodiments, the memory 24 of the second node 20 may comprise a non-transitory media. Examples of the memory 24 of the second node 20 include, but are not limited to, a random access memory (RAM), a read only memory (ROM), a mass storage media such as a hard disk, a removable storage media such as a compact disk (CD) or a digital versatile disk (DVD), and / or any other memory.

[0091] The processing circuitry 22 of the second node 20 can be communicatively coupled (e.g. connected) to the memory 24 of the second node 20. In some embodiments, the memory 24 of the second node 20 may be for storing program code or instructions which, when executed by the processing circuitry 22 of the second node 20, cause the second node 20 to operate in the manner described herein in respect of the second node 20. For example, in some embodiments, the memory 24 of the second node 20 may be configured to store program code or instructions that can be executed by the processing circuitry 22 of the second node 20 to cause the second node 20 to operate in accordance with the method described herein in respect of the second node 20. Alternatively or in addition, the memory 24 of the second node 20 can be configured to store any information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. The processing circuitry 22 of the second node 20 may be configured to control the memory 24 of the second node 20 to store any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein.

[0092] In some embodiments, as illustrated in Figure 13, the second node 20 may optionally comprise a communications interface 26. The communications interface 26 of the second node 20 can be communicatively coupled (e.g. connected) to the processing circuitry 22 of the second node 20 and / or the memory 24 of the second node 20. The communications interface 26 of the second node 20 may be operable to allow the processing circuitry 22 of the second node 20 to communicate with the memory 24 of the second node 20 and / or vice versa. Similarly, the communications interface 26 of the second node 20 may be operable to allow the processing circuitry 22 of the second node 20 to communicate with any one or more nodes (e.g. the first node 10 referred to herein, and / or the at least one control node referred to herein) referred to herein and / or any other node. The communications interface 26 of the second node 20 can be configured to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. In some embodiments, the processing circuitry 22 of the second node 20 may be configured to control the communications interface 26 of the second node 20 to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein.

[0093] Although the second node 20 is illustrated in Figure 13 as comprising a single memory 24, it will be appreciated that the second node 20 may comprise at least one memory (i.e. a single memory or a plurality of memories) 24 that operate in the manner described herein. Similarly, although the second node 20 is illustrated in Figure 13 as comprising a single communications interface 26, it will be appreciated that the second node 20 may comprise at least one communications interface (i.e. a single communications interface or a plurality of communications interfaces) 26 that operate in the manner described herein. It will also be appreciated that Figure 13 only shows the components required to illustrate an embodiment of the second node 20 and, in practical implementations, the second node 20 may comprise additional or alternative components to those shown.

[0094] Figure 14 illustrates a method performed by the second node 20 of a network in accordance with an embodiment. The method is for handling a PDU session in a network. The network comprises an AN and a CN. The second node 20 described earlier with reference to Figure 13 can be configured to operate in accordance with the method of Figure 14. The method can be performed by or under the control of the processing circuitry 22 of the second node 20 according to some embodiments.

[0095] With reference to Figure 14, as illustrated at block 302, a first request for establishment of a PDU session is received from a first node 10 of the AN. More specifically, the second node 20 (e.g. the processing circuitry 22 of the second node 20) receives the first request (e.g. via the communications interface 26 of the second node 20). The first request comprises site information indicative of a site associated with a first UP function of the AN. The first node 10 is configured to provide AN CP functionality as described herein.

[0096] As illustrated at block 304 of Figure 14, transmission of a first response message is initiated towards the first node 10. More specifically, the second node 20 (e.g. the processing circuitry 22 of the second node 20) initiates transmission of the first response message (e.g. via the communications interface 26 of the second node 20). The first response message comprises identifier information and location information. The identifier information is indicative of at least one third UP function selected to support the PDU session. The at least one third UP function is selected based on the site information, and the location information is indicative of whether co-location of the at least one third UP function and a second UP function of the AN is preferred.

[0097] Although not illustrated in Figure 14, in some examples, the method may comprise determining whether co-location of the at least one third UP function and the second UP function is preferred. In some of these examples, determining whether co-location of the at least one third UP function and the second UP function is preferred can be based on the site information, and / or one or more requirements associated with the PDU session. For example, determining whether co-location is preferred may be based on a measure of latency between the entity making the first request (e.g. a wireless device, such as a UE) and the second UP function.

[0098] Although not illustrated in Figure 14, in some examples, the method may comprise selecting, based on the site information, the at least one third UP function. In some examples, selecting the at least one third UP function may be based on information associated with the PDU session (e.g. PDU session specific conditions and / or requirements). For example, the selection of the at least one third UP function may be based on a requested data network name (DNN). In some examples, selection of the at least one third UP function may be further based on one or more policy control function (PCF) policies, and / or user data management (UDM) information. For example, the one or more PCF policies may be pre-configured (e.g. at the second node 20) and / or received from a (e.g. PCF) node of the network. The UDM information can comprise subscription information. For example, the second node 20 may query a UDM entity to look-up third UP functions which match a selection criteria. Alternatively, or in addition, the second node 20 may perform a look-up of suitable third UP functions (e.g. UPFs) using (e.g. locally stored) topology information, via a domain name system (DNS) look-up, and / or via some other look-up database. For example, if the site information is indicative of a first IP address of the first UP function, the second node 20 (e.g. SMF) may be able to select the at least one third UP function based on a latency from an IP address range that the first IP address belongs to. In some examples, as indicated above, the at least one third UP function can be selected from a plurality of third UP functions (e.g. UPFs). In some examples, the first node 10 may comprise the first UP function, as described herein. Selecting the at least one third UP function based on the site information, as defined herein, can allow the second node 20 to select one or more third UP functions that are located at the same site as the first UP function.

[0099] Although not illustrated in Figure 14, in some examples, receiving the first request may comprise receiving the first request from the first node via a first CN function (e.g. an AMF). Although also not illustrated in Figure 14, in some examples, initiating transmission of the first response message may comprises initiating transmission of the first response message towards the first node via the first CN function. The first CN function can be configured to operate as an access and mobility management function (AMF). For example, the first CN function may be an AMF of the CN, and / or the first CN function may be an AMF comprised in a (e.g. AMF) node of the CN.

[0100] In some examples, the first request referred to herein may be requested by a wireless device (e.g. a UE) of the AN. In some examples, the site information referred to herein can be indicative of the site at which the first UP function is located in the AN. For example, the site information can comprise one or more of an internet protocol (IP) address of the first UP function, a cell identifier (ID) of the first UP function, a registration area ID of the first UP function, an AN paging area ID of the first UP function, and a geographic location of the first UP function. The registration area ID may, for example, comprise a RAN-area code. The geographic location of the first UP function may be represented by a string encoding geo-location (e.g. corresponding to a geographic location, such as San Francisco)

[0101] In some examples, the co-location information referred to herein can comprise a flag indicative of whether co-location of the at least one third UP function and the second UP function is preferred. The flag may be referred to as a “co-location preferred” flag herein. In some examples, if the co-location information is indicative that co-location of the at least one third UP function and the second UP function is not preferred, the flag may be said to be “not set”. Alternatively, if the co-location information is indicative that co- location of the at least one third UP function and the second UP function is preferred, the flag may be said to be “set”.

[0102] In some examples, the identifier information may comprise a transport address of the at least one third UP function (e.g. UPF). As described herein, in some examples, the AN can be a RAN. As also described herein, in some examples, the second node may be configured to operate as an SMF.

[0103] Thus, in the manner described herein, it is possible to handle a PDU session in a network in an advantageous way that enables the conditional co-location of at least one third UP function (e.g. a UPF) and a second UP function of the AN.

[0104] The techniques described herein enable a UP-centric approach for selecting and configuring co-located AN and CN nodes. In a particular example, the techniques provide for the selection and configuration of co-located (R)AN UP (e.g. DU and / or CU- UP) nodes and CP-UP (e.g. UPF) nodes that allows AN and CN deployment (e.g. including CU-CP and SMF) from different vendors. In particular, the AN is able to indicate site information indicative of a site associated with a first UP function (e.g. a lower-RAN UP DU) during PDU Session establishment. Furthermore, the CN can then decide on applying co-location of a second UP function of the AN (e.g. a higher-RAN UP and / or CU-UP) with at least one third UP function (e.g. UPF). The CN is ablet to select an appropriate third UP function (e.g. UPF) and inform the AN about the preference for (e.g. UP) co-location. Based on the received preference indicator, the AN may attempt to select a first entity (e.g. higher-RAN UP and / or CU-UP) that is co-located with the third UP function (e.g. UPF).

[0105] As such, the improved techniques described herein advantageously provide for cooperation between the AN and the CN to select the same site for AN and CN controllers, respectively.

[0106] Figure 15 illustrates a control node 30 of a network in accordance with an embodiment. The control node 30 is for handling a PDU session in a network. In some embodiments, the control node 30 referred to herein can refer to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with the first node 10 referred to herein, the second node 20 referred to herein, and / or with other nodes or equipment to enable and / or to perform the functionality described herein. In some embodiments, the control node 30 referred to herein can, for example, be a physical node (e.g. a physical machine or server) or a virtual node (e.g. a virtual machine, VM). The control node 30 is configured to provide UP control functionality.

[0107] As illustrated in Figure 15, the control node 30 comprises processing circuitry (or logic) 32. The processing circuitry 32 controls the operation of the control node 30 and can implement the method described herein in respect of the control node 30. The processing circuitry 32 can be configured or programmed to control the control node 30 in the manner described herein. The processing circuitry 32 can comprise one or more hardware components, such as one or more processors, one or more processing units, one or more multi-core processors and / or one or more modules. In particular implementations, each of the one or more hardware components can be configured to perform, or is for performing, individual or multiple steps of the method described herein in respect of the control node 30. In some embodiments, the processing circuitry 32 can be configured to run software to perform the method described herein in respect of the control node 30. The software may be containerised according to some embodiments. Thus, in some embodiments, the processing circuitry 32 may be configured to run a container to perform the method described herein in respect of the control node 30.

[0108] Briefly, the processing circuitry 32 of the control node 30 is configured to determine that a second UP function of the AN and at least one third UP function are to be co-located in the network. The at least one third UP function is selected to support a PDU session. The processing circuitry 32 of the control node 30 is also configured to configure the second UP function and the at least one third UP function to support the PDU session in a co-location configuration.

[0109] As illustrated in Figure 15, in some embodiments, the control node 30 may optionally comprise a memory 34. The memory 34 of the control node 30 can comprise a volatile memory or a non-volatile memory. In some embodiments, the memory 34 of the control node 30 may comprise a non-transitory media. Examples of the memory 34 of the control node 30 include, but are not limited to, a random access memory (RAM), a read only memory (ROM), a mass storage media such as a hard disk, a removable storage media such as a compact disk (CD) or a digital versatile disk (DVD), and / or any other memory.

[0110] The processing circuitry 32 of the control node 30 can be communicatively coupled (e.g. connected) to the memory 34 of the control node 30. In some embodiments, the memory 34 of the control node 30 may be for storing program code or instructions which, when executed by the processing circuitry 32 of the control node 30, cause the control node 30 to operate in the manner described herein in respect of the control node 30. For example, in some embodiments, the memory 34 of the control node 30 may be configured to store program code or instructions that can be executed by the processing circuitry 32 of the control node 30 to cause the control node 30 to operate in accordance with the method described herein in respect of the control node 30. Alternatively or in addition, the memory 34 of the control node 30 can be configured to store any information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. The processing circuitry 32 of the control node 30 may be configured to control the memory 34 of the control node 30 to store any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein.

[0111] In some embodiments, as illustrated in Figure 15, the control node 30 may optionally comprise a communications interface 36. The communications interface 36 of the control node 30 can be communicatively coupled (e.g. connected) to the processing circuitry 32 of the control node 30 and / or the memory 34 of the control node 30. The communications interface 36 of the control node 30 may be operable to allow the processing circuitry 32 of the control node 30 to communicate with the memory 34 of the control node 30 and / or vice versa. Similarly, the communications interface 36 of the control node 30 may be operable to allow the processing circuitry 32 of the control node 30 to communicate with any one or more nodes (e.g. the first node 10 referred to herein, and / or the second node 20 referred to herein) referred to herein and / or any other node. The communications interface 36 of the control node 30 can be configured to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein. In some embodiments, the processing circuitry 32 of the control node 30 may be configured to control the communications interface 36 of the control node 30 to transmit and / or receive any of the information, data, messages, requests, responses, indications, notifications, signals, or similar, that are described herein.

[0112] Although the control node 30 is illustrated in Figure 15 as comprising a single memory 34, it will be appreciated that the control node 30 may comprise at least one memory (i.e. a single memory or a plurality of memories) 34 that operate in the manner described herein. Similarly, although the control node 30 is illustrated in Figure 15 as comprising a single communications interface 36, it will be appreciated that the control node 30 may comprise at least one communications interface (i.e. a single communications interface or a plurality of communications interfaces) 36 that operate in the manner described herein. It will also be appreciated that Figure 15 only shows the components required to illustrate an embodiment of the control node 30 and, in practical implementations, the control node 30 may comprise additional or alternative components to those shown.

[0113] Figure 16 illustrates a method performed by at least one control node 30 of a network in accordance with an embodiment. The method is for handling a PDU session in a network. The network comprises an AN and a CN. The control node 30 described earlier with reference to Figure 15 can be configured to operate in accordance with the method of Figure 16. The method can be performed by or under the control of the processing circuitry 32 of the control node 30 according to some embodiments. The method is performed by at least one control node 30 (e.g. one or more control nodes). For example, the at least one control node 30 can comprise a first control node and a second control node. The at least one control node 30 may be configured to control the UP (e.g. functions and / or nodes) of the AN, and / or the UP (e.g. functions and / or nodes) of the CN. In some examples, the first control node may be configured to control the UP (e.g. functions and / or nodes) of the AN. Alternatively, or in addition, the second control node may be configured to control the UP (e.g. functions and / or nodes) of the CN.

[0114] With reference to Figure 16, as illustrated at block 402, it is determined that a second UP function of the AN and at least one third UP function are to be co-located in the network. More specifically, the at least one control node 30 (e.g. the processing circuitry 32 of the at least one control node 30) can perform the determination. The at least one third UP function is selected to support a PDU session. The second UP function and the at least one third UP function can be as described earlier (e.g. with reference to Figures 11 to 15). Determining that the second UP function and the at least one third UP function are to be co-located may comprise, for example, detecting co-location of the second UP function and the at least one third UP function at the same site (e.g. of the network).

[0115] As illustrated at block 404 of Figure 16, the second UP function and the at least one third UP function are configured to support the PDU session in a co-location configuration. More specifically, the at least one control node 30 (e.g. the processing circuitry 32 of the at least one control node 30) performs the configuration. Therefore, the at least one control node 30 may configure the second UP function and the at least one third UP function for co-location. In some examples, the configuration may comprise configuring one or more AN UP nodes, and / or one or more CN UP nodes, for co-location.

[0116] Herein, the second UP function may be referred to as a higher-AN UP function (e.g. node), and / or a higher-RAN UP function (e.g. node) (e.g. in scenarios in which the AN referred to herein is a RAN). The first UP function may be referred to herein as a lower- AN UP function (e.g. node), and / or a lower-RAN UP function (e.g. node) (e.g. in scenarios in which the AN referred to herein as a RAN). Herein, the at least one third UP function may be referred to as a CN UP function (e.g. node).

[0117] In some examples, the configuration of the second UP function and the at least one third UP function may depend on the location of the at least one third UP function. For example, the configuration may comprise (e.g. only) configuring co-location of the second UP function (e.g. higher-RAN UP function) with the at least one third UP function (e.g. CN UP function). Alternatively, or in addition, the configuration may comprise configuring co-location of the second UP function (e.g. higher-RAN UP function), the at least one third UP function (e.g. CN UP function), and the first UP function (e.g. lower- RAN UP function).

[0118] Although not illustrated in Figure 16, in some examples, configuring the second UP function and the at least one third UP function to support the PDU session in the colocation configuration may comprise configuring a single binary to execute the second UP function and the at least one third UP function, configuring the second UP function and the at least one third UP function to operate using a shared memory, and / or configuring the second UP function and the at least one third UP function to forward information associated with the PDU session to the other of the at least one third UP function and the second UP function. Configuring a single binary to execute the second UP function and the at least one third UP function may comprise configuring the same binary for execution of the AN (e.g. RAN) UP and the CN UP. Configuring the second UP function and the at least one third UP function to operate using a shared memory may comprise configuring the AN (e.g. RAN) UP and the CN UP to use a shared memory. For example, configuring the AN UP and the CN UP to use a shared method may comprise configuring the AN UP and the CN UP to perform storage (e.g. of data) using the same process. Configuring the second UP function and the at least one third UP function to forward information associated with the PDU session to the other of the at least one third UP function and the second UP function may comprise configuring the second UP function to forward the information associated with the PDU session to the at least one third UP function, and vice-versa. The information associated with the PDU session may comprises one or more data packets associated with the PDU session, and / or a tunnel identifier (TEID) associated with the PDU session. The forwarding of the information may be performed using a generic forwarding method, for example, via a user datagram protocol (UDP), and / or Ethernet.

[0119] In some examples, configuring the second UP function and the at least one third UP function to support the PDU session in the co-location configuration may comprise providing co-location information to the second UP function and / or the at least one third UP function. As described herein, the co-location information can be indicative that the second UP function and the at least one third UP function are to be co-located in the network. As also described herein, the co-location information can comprise a flag indicative of whether co-location of the at least one third UP function and the second UP function is preferred. In these examples, the second UP function and the at least one third UP function may determine what configuration to use for co-location (e.g. any of the configurations mentioned above). As mentioned herein, the at least one control node 30 can comprise a first control node, as described herein, and a second control node, as described herein. In such scenarios, the first control node may provide the co-location information to the second UP function, and / or the second control node may provide the co-location information to the at least one third UP function.

[0120] In some examples, determining that the second UP function of the AN and the least one third UP function are to be co-located in the network may comprise obtaining a second request from a first node 10 of the AN and a second node 20 of the CN. The first node

[0121] 10 and the second node 20 can be as described herein (e.g. with reference to Figures

[0122] 11 to 14) For example, the first node 10 can be configured to provide AN CP functionality, and / or the second node 20 can be configured to provide CN CP functionality. The second request can comprise a request to configure the second UP function and the at least one third UP function to support the PDU session. Therefore, in some examples, determining (e.g. detecting) that the second UP function and the at least one third U P function at to be co-located can comprise the at least one control node 30 (e.g. a single control node 30) being contacted from both the first node 10 and the second node 20 to configure (e.g. setup) the co-location. In some examples, the second request can comprise an identifier of the PDU session. As mentioned herein, in some examples, the at least one control node 30 may comprise a first control node configured to provide UP control functionality for the second UP function, and a second control node configured to provide UP control functionality for the at least one third UP function. In some of these examples, determining that the second UP function and the least one third UP function are to be co-located in the network can be based on an IP address of the first control node, and / or an IP address of the second control node. Therefore, in some examples, determining (e.g. detecting) that the second UP function and the at least one third UP function at to be co-located can comprise the first control node obtaining (e.g. receiving) the IP address of the second control node, and vice-versa.

[0123] Thus, in the manner described herein, is it possible to handle a PDU session in a network such that AN (e.g. RAN) UP functionality and CN UP functionality can be co-located in a network. In this way, the PDU session can be handled in a manner that reduces UP latency, increases performance, and simplifies the functionality on the UP.

[0124] There is also provided a system (e.g. network) comprising any two or more of the first node 10 described herein, the second node 20 described herein, and the at least one control node 30 described herein. A method performed by the system comprises any two or more of the method described herein in respect of the first node 10, the method described herein in respect of the second node 20, and the method described herein in respect at least one control node 30.

[0125] Figure 17 is a signalling diagram illustrating an exchange of signals in a system (e.g. a network) according to an embodiment. The system illustrated in Figure 17 comprises a first node 10 and a second node 20, as described herein. In the system of Figure 17, the first node 10 is a CU-CP node. The system illustrated in Figure 17 also comprises a wireless device 502 (“NG UE”), a first UP function 504 (“DU”), a second UP function 506 (“CU-UP”), a first CN function 508 (“AMF”), and at least one third UP function 510 (“UPF”). The system illustrated in Figure 17 comprises an AN and a CN. Although not explicitly illustrated in Figure 17, the AN may comprise the wireless device 502, the first UP function 504, the first node 10, and the second UP function 506. Although also not illustrated in Figure 17, the CN may comprise the first CN function 508, the second node 20, and the at least one third UP function 510. the system architecture illustrated in Figure 17 can be referred to as a 5G architecture. As illustrated in Figure 17, the wireless device 502 may be a (e.g. next generation (NG)) UE, the first UP function 504 may be a distributed unit (e.g. of a gNB), the second UP function 506 may be a CU-UP node, the first CN function 508 may be an AMF (e.g. node), and / orthe at least one third UP function may be a U PF node. Although the system illustrated in Figure 17 comprises only a single UPF node, it will be understood that the at least one third UP function 510 may comprise any number of UPF nodes (e.g. one or more).

[0126] As illustrated by arrow 512 of Figure 17, the wireless device 502 may initiate transmission of a first request, as described herein, towards the second node 20 via the first node 10. Thus, the first node 10 can receive the first request from the wireless device. As illustrated by block 514 of Figure 17, the first node 10 may determine a function (e.g. AMF) of the CN to forward the first request to. In the example illustrated in Figure 17, the first node 10 may determine (e.g. select) the first CN function 508 for forwarding of the first request. As illustrated by block 516 of Figure 17, the first node 10 may determine (e.g. identity) the site associated with the first UP function 504 (e.g. “DU site identification”). For example, before sending the first request (e.g. “PDU Session Establishment request”) to the first CN function 508 (e.g. AMF), the first node 10 (e.g. CU-CP node) may identify the site for the first UP function 504 (e.g. DU).

[0127] As illustrated by arrow 518 of Figure 17, the first node 10 initiates transmission of the first request towards the second node 20. As also illustrated by arrow 518 of Figure 17, the first node 10 may initiate transmission of the first request via the first CN function 508. Thus, the first CN function 508 can receive the first request from the first node 10. The first node 10 may initiate transmission of a first message (e.g. “N2 INITIAL UE MESSAGE(... , NAS SM PDU: “PDU Session Est. Request”)”) which may comprise the first request. The first request comprises site information indicative of the site associated with the first UP function 504. Thus, the site information can be conveyed to the second node 20 through the first CN function. The site information can be as described herein.

[0128] As illustrated by block 520 of Figure 17, the first CN function 508 may select the second node 20 to which to forward the first request (e.g. and first message). As illustrated by arrow 522 of Figure 17, the first CN function may transmit the first request towards the second node 20. Thus, the second node 20 receives the first request from the first node 10 (e.g. via the first CN function 508). The first request may be comprised in a second message (e.g. “N11 Request (... , NAS SM PDU: “PDU Session Est. Request”)”) transmitted by the first CN function 508.

[0129] As illustrated by block 524 of Figure 17, the second node 20 may select, based on the site information comprised in the first request, the at least one third UP function 510. Thus, the selection of the at least one third UP function 510 can consider the site information associated with the first UP function 504. The selection of the at least one third UP function can be as described herein (e.g. with reference to Figure 14).

[0130] As illustrated by arrow 526 of Figure 17, the second node 20 may initiate transmission of an establishment request (e.g. “N4 session establishment request”) towards the at least one third UP function 510. Thus, the at least one third UP function 510 can receive the establishment request from the second node 20. As illustrated by arrow 528 of Figure 17, the at least one third UP function 510 can initiate transmission of an establishment request response (e.g. “N4 session establishment response”) towards the second node 20. Thus, the second node 20 may receive the establishment request response from the at least one third UP function 510. The establishment request response may comprise a UPF transport address, and / or a TEID.

[0131] Although not explicitly illustrated in Figure 17, the second node 20 may determine whether co-location of the at least one third UP function 510 (e.g. UPF) and the second UP function 506 (e.g. CU-UP) is preferred. Determining whether co-location of the at least one third UP function 510 and the second UP function 506 is preferred can be based on the site information, and / or one or more requirements associated with the PDU session. As illustrated by arrow 530 of Figure 17, the second node initiates transmission of a first response message (e.g. “N11 Response (UPF IP, TEID and “co-location required” flag)”), as defined herein, towards the first node 10. The first response message comprises identifier information and location information. The identifier information is indicative of the least one third UP function 510 selected to support the PDU session, and the location information is indicative of whether co-location of the at least one third UP function 510 and the second UP function 506 is preferred. As also illustrated by arrow 530 of Figure 17, the first response message can be transmitted towards the first node 10 via the first CN function 508.

[0132] As illustrated by arrow 532 of Figure 17, the first CN function 508 transmits the first response message (e.g. “N2 INITIAL CONTEXT SETUP REQUEST”) towards the first node 10. Thus, the first node 10 receives the first response message from the second node 20 (e.g. via the first CN function 508). The site information comprised in the first response message may comprise a transport address identifier (e.g. TEID) of the at least one third UP function 510. The site information comprised in the first response message may comprise an IP address of the at least one third UP function 510. In some examples, the co-location information may comprise a flag indicative of whether co-location of the at least one third UP function and the second UP function is preferred. Thus, in some examples, the second node 20 can convey, through the first CN function, a “co-location preferred” flag to the first node 10.

[0133] As illustrated by block 534 of Figure 17, the first node 10 may select, based on the identifier information and the co-location information, a first entity of the AN to be configured to support the PDU session. The first entity of the AN can comprise the second UP function 506. Thus, the first node 10 can select the first entity (e.g. the second UP function 506) based on the received identifier information (e.g. UPF transport address) as well as the co-location information (e.g. “co-location preferred” flag). The selection can be based on policies configured for the first node 10.

[0134] For example, if the co-location information is indicative that co-location of the at least one third UP function and the second UP function is not preferred (e.g. “co-location preferred” flag is not set), then the first node 10 may select a site for the first entity based on one or more (e.g. (R)AN) policies. For example, a default (e.g. (R)AN) policy could be to co-locate the second UP function 506 with the first UP function 504.

[0135] In another example, if the co-location information is indicative that co-location of the at least one third UP function and the second UP function is preferred (e.g. “co-location preferred” flag is set), then the first node 10 may select a first entity of the AN that is associated with the site associated with the at least one third UP function 510. In some of these examples, the first entity may be the second UP function 506. As such, the first node 10 can attempt to select the same site for the second UP function 506 as the site of the selected at least one third UP function 510. The first node 10 may use the identifier information (e.g. UPF transport address) as received from the second node 20, and / or an internal configuration (e.g. related to an IP to site mapping), to perform the selection of the first entity. Depending on the UPF location, multiple scenarios are possible. For example, if a central (e.g. UPF( site was selected by the second node 20 for the at least one third UP function 510, then the second UP function 506 (e.g. the first entity) and the at least one third UP function 510 can be co-located on the central site. This may occur, for example, in cases in which a data network name (DNN) may only be connected to the central site, and / or a stable UE IP address is needed.

[0136] In another example, if the site selected for the at least one third UP function (e.g. by the second node 20) is the same as the site of the first UP function 504, then each of the first UP function, the second UP function and the at least one third UP function may be co-located (e.g. on the same site).

[0137] As illustrated by arrow 536 of Figure 17, the first node 10 may initiate transmission of an establishment request (e.g. “CU-UP establishment Request”) towards the first entity (e.g. the second UP function 506). The establishment request can be a request to establish a PDU session (e.g. as comprised in the first request). The establishment request may comprise a transport address of the at least one third UP function 510, and / or an identifier (e.g. TEID) of the at least one third UP function 510. As illustrated by arrow 538 of Figure 17, the first entity (e.g. the second UP function 506) can transmit an establishment request response to the first node 10. Thus, the first node 10 can receive the establishment request response from the first entity (e.g. the second UP function 506).

[0138] As illustrated by arrow 540 of Figure 17, the first node 10 can initiate transmission of a PDU session establishment request (e.g. “N2 INITIAL CONTEXT SETUP RESPONSE”) towards the second node 20. As also illustrated by arrow 540 of Figure 17, the PDU session establishment request can be transmitted towards the second node 20 via the first CN function 508. The PDU session establishment request can comprise a request to establish the PDU session between the at least one third UP function 510 and the first entity (e.g. second UP function 506). As illustrated by arrow 542 of Figure 17, the first CN function 508 may transmit the PDU session establishment request (e.g. “N11 Request”) towards the second node 20. Thus, the second node 20 can receive the PDU session establishment request from the first node 10 (e.g. via the first CN function 508). As illustrated by arrow 544 of Figure 17, the second node 20 may transmit the PDU session establishment request towards the at least one third UP function 510. Thus, the at least one third UP function 510 can receive the PDU session establishment request from the second node 20. The PDU session establishment request can comprise an identifier (e.g. a transport address and / or a TEID) of the first entity (e.g. the second UP function 506).

[0139] As illustrated by block 546 of Figure 17, a user plane tunnel may be established between the at least one third UP function 510 and the first entity (e.g. the second UP function 506) to support the PDU session.

[0140] Figure 18 is a schematic illustration of a system according to an embodiment. The system illustrated in Figure 18 comprises a first node 10 (e.g. “CU-CP”), a second node 20 (e.g. “SMF”), and at least one control node 30 (e.g. “Controller”). In the example illustrated in Figure 18, the at least one control node 30 comprises only a single control node. As illustrated in Figure 18, the system may also comprise multiple second UP functions 608, 612 (e.g. “CU-UP”), and at least one third UP function 610, 614 (e.g. “UPF”). As illustrated by block 602 of Figure 18, in some examples, the second UP functions 608, 612 and the at least one third UP function 610, 614 may be associated with the same vendor (e.g. “Single-vendor”). The system illustrated in Figure 18 can comprise a first blade 604 (“Blade #1”) and a second blade 606 (“Blade #2”). As illustrated in Figure 18, a primary second UP function 608 and a primary third UP function 610 can be run on the (e.g. same) first blade 604. Running a second UP function and a third UP function on the same blade can decrease computational footprint in the network by reducing the amount of (de)packetisation and / or an amount of input / output (I / O) operations.

[0141] As illustrated by arrow 618 of Figure 18, the first node 10 may communicate with the primary second UP function 608 (e.g. over an E1 interface) via the at least one control node 30. As illustrated by arrow 620 of Figure 18, the second node 20 may communicate with the primary third UP function 610 (e.g. over an N4 interface) via the at least one control node 30.

[0142] As illustrated by arrow 616 of Figure 18, the primary second UP function 608 may obtain (e.g. receive) uplink UP traffic (e.g. data and / or information). The uplink UP traffic may be received from the wireless device referred to herein. As illustrated by arrow 622 of Figure 18, the primary second UP function 608 may forward the uplink UP traffic to the primary third UP function 610. The selection procedure on the UP can vary depending on whether the at least one control node 30 comprises the same control node for configuring the primary second UP function 608 (e.g. CU-UP) and the primary third UP function 610 (e.g. UPF). In the example illustrated in Figure 18, it can be assumed that the same at least one control node 30 has been selected by both the first node 10 and the second node 20. This scenario may be achieved, for example, by selecting the same site for (e.g. co-locating) the primary second UP function 610 and the primary third UP function 610 (e.g. as described herein with reference to Figure 12). In some examples, the same at least one control node 30 may be selected if a configuration (e.g. of selection logic) in the first node 10 and the second node 20 points to the same (e.g. CU-UP and UPF) at least one control node 30 (e.g. for a given site).

[0143] If the same at least one control node 30 is selected, then the at least one control node 30 may determine that the primary second UP function 608 and the primary third UP function 610 are to be co-located based on a second request. The second request can comprise a request to configure the primary second UP function 608 and the primary third UP function 610 to support the PDU session, as defined herein. For example, if a single control node receives a second request from both the first node 10 and the second node 20, and the second request comprises an identifier of the PDU session (e.g. a PDU Session ID), then the control node may have enough information to correlate the separate second requests (e.g. for a given PDU Session). As such, the control node can provide optimisation for co-location configuration of the primary second UP function 608 and the primary third UP function 610.

[0144] It will be understood that, although Figure 18 shows co-location of a second UP function 608, 612 and at least one third UP function 610, 614, it will be understood that a first UP function, as referred to herein, may also be co-located with a second UP function 608, 612 (e.g. and at least one third UP function 610, 614) according to some examples. For example, a first UP function, as referred to herein, may be co-located with the primary second UP function 608 and the primary third UP function 610. Such a scenario may occur if the site of the at least one third UP function is selected to be the same as the site of the first UP function.

[0145] Figure 19 is a schematic illustration of a system according to an embodiment. The system illustrated in Figure 19 comprises a first node 10 (e.g. “CU-CP”), a second node 20 (e.g. “SMF”), and at least one control node 30. In the example illustrated in Figure 19, the at least one control node 30 comprises a first control node 30a and a second control node 30b. The first control node 30a can be configured to provide UP control functionality for one or more second UP functions 714, 718. The second control node 30b can be configured to provide UP control functionality for at least one third UP function 716, 720. As illustrated by block 702 of Figure 19, in some examples, the one or more second UP functions 714, 718 and the at least one third UP function 716, 720 may be associated with the same vendor. The system illustrated in Figure 18 can comprise a first blade 706 (“Blade #1”) and a second blade 708 (“Blade #2”). As illustrated in Figure 19, a primary second UP function 714 and a primary third UP function 716 can be run on the (e.g. same) first blade 706. As also illustrated in Figure 19, a secondary second UP function 718 and a secondary third UP function 720 can be run on the (e.g. same) second blade 708.

[0146] As illustrated in Figure 19, the system can comprise a network layer 704 (“DC networking layer w . L3 / L4 LB”), a first data layer 710 (“Data layer for RAN workers”) , and a second data layer 712 (“Data layer for CN workers”). The first data layer 710 can be configured to enable communication with nodes and / or functions of the AN. The second data layer 712 can be configured to enable communication with nodes and / or functions of the CN.

[0147] As illustrated by arrows 724, 728 and 732 of Figure 19, the first control node 30a can be configured to provide communication between the first node 10 and the primary second UP function 714. As also illustrated by arrow 724 of Figure 19, the first node 10 may communicate with the first control node 30a over an E1 interface. As illustrated by arrows 726, 730 and 734 of Figure 19, the second control node 30b can be configured to provide communication between the second node 20 and the primary third UP function 716. As also illustrated by arrow 726 of Figure 19, the second node 20 may communicate with the second control node 30b over an N4 interface.

[0148] As illustrated in Figure 19, in some examples, although a second UP function and a third UP function may be co-located (e.g. co-sited), different control nodes (e.g. Controllers) may be chosen (e.g. by the first node 10 and the second node 20, respectively) to configure the second UP function and the third UP function, respectively.

[0149] In such examples (e.g. in which the at least one control node comprises a first control node 30a and a second control node 30b), co-location may still be achieved. For example, the first control node 30a may determine (e.g. infer) that the second control node 30b is co-located (co-sited) based on an IP address of a received general packet radio service (GPRS) Tunnelling Protocol (GTP). In such a case, the IP address may be site-specific. In some examples, the first control node 30a and the second control node 30b may configure a co-located second UP function and third UP function in a data access layer (e.g. of the network). The configuration can comprise configuring colocation information, as defined herein, in the data access layer (e.g. to enable the second UP function and / or the third UP function to obtain (e.g. read) the co-location information from the data access layer).

[0150] In some examples, as illustrated by arrow 722 of Figure 19, the primary second UP function 714 may receive a first (e.g. UL) packet associated with (e.g. belonging to) the PDU session. In response to receiving the first packet, the primary second UP function 714 may obtain (e.g. read) the co-location information (e.g. state) from the data access layer 710. The primary second UP function may determine (e.g. decide), based on the co-location information (e.g. flag), on what configuration (e.g. optimisation) for colocation to choose. In some examples, if the same (e.g. common) binary can execute both the primary second UP function 714 and the primary third UP function 716, then the primary second UP function 714 may obtain the co-location information (e.g. configuration) from the data access layer and execute the configuration on behalf of the primary second UP function 714 and / or the primary third UP function 716.

[0151] In some examples, if the primary third UP function 716 is executed on a different binary to the primary second UP function 714, then the primary second UP function 714 may transmit (e.g. pass) the first packet to a co-located binary associated with the primary third UP function 716. The transmission may be performed in a pre-configured way (e.g. using a shared memory method). In some of these examples, a TEID may also be transmitted to the co-located binary. In this way, the primary third UP function 716 can identify the PDU Session.

[0152] In some examples, as illustrated by arrow 736 of Figure 19, if the primary third UP function 716 corresponds to a different service (e.g. from a different vendor) than the primary second UP function 714, then the primary second UP function 714 may forward the first packet (e.g. and all following packets) as usual (e.g. encapsulated in a GTP tunnel). It will be understood that, although Figure 19 shows co-location of a second UP function 714, 718 and at least one third UP function 716, 720, it will be understood that a first UP function, as referred to herein, may also be co-located with a second UP function 714, 718 (e.g. and at least one third UP function 716, 720) according to some examples. For example, a first UP function, as referred to herein, may be co-located with the primary second UP function 714 and the primary third UP function 716. Such a scenario may occur if the site of the at least one third UP function is selected to be the same as the site of the first UP function.

[0153] Figure 20 is a signalling diagram illustrating an exchange of signals in a system (e.g. a network) according to an embodiment. The system illustrated in Figure 20 comprises a wireless device 802, a first node 10, a first CN function 804, a second node 20, and at least one third UP function 806. The wireless device 802, the first CN function 804, the second node 20, and the least one third U P function 806 of Figure 20 can be as described with reference to the wireless device 502, the first CN function 804, the second node 20, and the least one third UP function 86 of Figure 17, respectively.

[0154] The system illustrated in Figure 17 has similarities to the system illustrated in Figure 20, with some exceptions. For example, in the system illustrated in Figure 20, the first UP function and the second UP function are comprised in the first node 10. That is, in the example illustrated in Figure 20, the system architecture of Figure 20 can be referred to as a collapsed (e.g. RAN) architecture. As such, the DU, CU-UP and CU-CP functionality can be combined into a single (e.g. standardised) network function (i.e. the first node 10). The first node 10 of Figure 20 can be referred to herein as a RAN node and / or RAN UP node.

[0155] The steps illustrated by arrow 808 and block 810 of Figure 20 can be as described with reference to arrow 512 and block 514 of Figure 17, respectively.

[0156] As illustrated by block 812 of Figure 20, the first node 10 may determine, prior to initiating transmission of a first request, a site associated with a first UP function. The determining may comprise selecting the site associated with the first UP function. As mentioned above, in the example illustrated in Figure 20, the first node 10 can comprise the first UP function. As such, in some examples, selecting the site associated with the first UP function can comprise (pre)selecting the site for the first node 10 (e.g. RAN UP node). The steps illustrated by arrow 814, block 816, arrow 818, block 820, arrow 822, arrow 824, arrow 826 and arrow 828 of Figure 20 can be as described with reference to arrow 518, block 520, arrow 522, block 524, arrow 526, arrow 528, arrow 530, arrow 532 of Figure 17, respectively. As mentioned above, in the example illustrated in Figure 20, the first node 10 can comprise the first UP function. As such, in some examples, the site information (as comprised in the first request described herein) can comprise information indicative of the site at which the first node 10 is located in the AN.

[0157] As illustrated by block 830 of Figure 20, the first node 10 may select, based on the identifier information, as described herein, and the co-location information, as described herein, a first entity of the AN to be configured to supported the PDU session. The first entity can comprise the second UP function, as described herein. In some examples, selecting the first entity may comprise (re)selecting a RAN-UP node. For example, the first node 10 may (re)select a different RAN-UP node to be configured to support the PDU session. In other examples, the first node 10 may select the first node 10 as the first entity (e.g. RAN UP node). Selecting the first entity can be based on one or more policies configured for the AN, as described herein.

[0158] The selection of the first entity can depend on the co-location information (i.e. as comprised in the first response message received by the first node 10) . For example, if the co-location information is indicative that co-location of the at least one third UP function 806 and the second UP function is not preferred, the first node 10 may select a site for the first entity (e.g. RAN-UP node) based on one or more policies configured for the AN (e.g. one or more internal RAN policies), as described herein.

[0159] In examples in which the co-location information is indicative that co-location of the at least one third UP function 806 and the second UP function is preferred, the first node 10 may (e.g. attempt to) select the same site for the first entity (e.g. RAN-UP node) as the site of the at least one third UP function 806. The selection of the first entity can be based on the identifier information of the first response message defined herein, and / or a configuration of the first node 10 (e.g. related to an IP range site mapping). In some examples, the first node 10 may not need to perform a (re)selection if the site associated with the first UP function (e.g. as determined with reference to block 810 of Figure 20) is the same as that of the site of the at least one third UP function 806. The selection of the first entity can depend on the site associated with the at least one third UP function 806. For example, if a central site is selected for the site of the at least one third UP function 806 (e.g. by the second node 20), then the first entity may be selected such that the first entity and the at least one third UP function are co-located on the same (e.g. central) site (e.g. if allowed by AN policies). This may occur, for example, in cases in which a data network name (DNN) may only be connected to the central site, and / or a stable UE IP address is needed. If the site of the at least one third UP function 806 is selected to be the same as the first node 10, then no re-selection is needed to result in the second UP function and the at least one third UP function 806 being colocated.

[0160] As illustrated by block 832 of Figure 20, the first node 10 may provide the identifier information, as defined herein, to the first entity. As illustrated by block 834 of Figure 20, the first node 10 may receive, from the first entity, information indicative of the identity of the first entity (e.g. a transport address, and / or a TEID of the first entity).

[0161] Arrows 836, 838 and 840 of Figure 20 can be as described with reference to arrows 540, 542 and 544 of Figure 17, respectively.

[0162] As illustrated by block 842 of Figure 20, a user plane tunnel may be established between the at least one third UP function 806 and the first entity (e.g. first node 10 and / or RAN UP node) to support the PDU session. As illustrated in the example of Figure 20, the first entity may be the first node 10, and thus the user plane tunnel can be established between the first node 10 and the at least one third UP function 806.

[0163] There is also provided a computer program comprising instructions which, when executed by processing circuitry (such as the processing circuitry 12 of the first node 10 described herein, the processing circuitry 22 of the second node 20 described herein, and / or the processing circuitry 32 of the control node 30 described herein), cause the processing circuitry to perform at least part of the method described herein. There is provided a computer program product, embodied on a non-transitory machine-readable medium, comprising instructions which are executable by processing circuitry (such as the processing circuitry 12 of the first node 10 described herein, the processing circuitry 22 of the second node 20 described herein, and / or the processing circuitry 32 of the control node 30 described herein) to cause the processing circuitry to perform at least part of the method described herein. There is provided a computer program product comprising a carrier containing instructions for causing processing circuitry (such as the processing circuitry 12 of the first node 10 described herein, the processing circuitry 22 of the second node 20 described herein, and / or the processing circuitry 32 of the control node 30 described herein) to perform at least part of the method described herein. In some embodiments, the carrier can be any one of an electronic signal, an optical signal, an electromagnetic signal, an electrical signal, a radio signal, a microwave signal, or a computer-readable storage medium.

[0164] In some embodiments, the first node functionality described herein, the second node functionality described herein, and / or the at least one control node functionality described herein can be performed by hardware. Thus, in some embodiments, the first node 10, the second node 20, and / or the at least one control node 30 described herein can be a hardware entity. However, it will also be understood that optionally at least part or all of the first node functionality, the second node functionality, and / or the at least one control node functionality described herein can be virtualised. For example, the functions performed by the first node 10, the second node 20, and / or the at least one control node 30 described herein can be implemented in software running on generic hardware that is configured to orchestrate the first node functionality, the second node functionality, and / or the at least one control node functionality described herein. Thus, in some embodiments, the first node 10, the second node 20, and / or the at least one control node 30 described herein can be a virtual node. In some embodiments, at least part or all of the first node functionality, the second node functionality, and / or the at least one control node functionality described herein may be performed in a network enabled cloud. Thus, the method described herein can be realised as a cloud implementation according to some embodiments. The first node functionality, the second node functionality, and / or the at least one control node functionality described herein may all be at the same location or at least some of the first node functionality, the second node functionality, and / or the at least one control node functionality may be distributed, e.g. the first node functionality, the second node functionality, and / or the at least one control node functionality may be performed by one or more different nodes.

[0165] Therefore, as described herein, there are provided improved techniques for handling PDU sessions in a network. The techniques enable a co-located second UP function of an (e.g. RAN UP function) and at least one third UP function of a CN (e.g. CN UP function). By enabling the co-location of the second UP function and the at least one third UP function, it is possible to reduce user plane latency, increase performance in the network, and simplify user plane functionality. Such benefits are especially advantageous, for example, in use cases involving eMBB, Massive MTC and / or Critical MTC. Beneficially, the techniques described herein can be applied on the top of the existing (e.g. 3GPP) network architecture. In other words, the implementation of the techniques described herein require only minor implementation updates to the network current architecture. For example, implementation of the techniques described herein may only require the addition of certain attributes.

[0166] Furthermore, the techniques described herein provide for the handling of PDU sessions even if an AN and CN are from different (e.g. network) vendors (e.g. and / or AN and / or CN function from different vendors. The level of optimisation provided by the techniques discussed herein can depend on whether the AN UP and CN UP functionality belongs to the same vendor, and / or whether it can use a specific code base.

[0167] It should be noted that the above-mentioned embodiments illustrate rather than limit the idea, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

CLAIMS1. A method for handling a packet data unit, PDU, session in a network, wherein the network comprises an access network, AN, and a core network, CN, the method being performed by a first node (10) of the AN, wherein the first node (10) is configured to provide AN control plane, CP, functionality, the method comprising: initiating (202, 518, 814) transmission of a first request for establishment of a PDU session towards a second node (20) of the CN, wherein the second node (20) is configured to provide CN CP functionality, and wherein the first request comprises site information indicative of a site associated with a first user plane, UP, function (504) of the AN; and receiving (204, 532, 828), from the second node (20), a first response message comprising identifier information and co-location information, wherein the identifier information is indicative of at least one third UP function (510, 806) selected to support the PDU session, wherein the at least one third UP function (510, 806) is selected based on the site information, and wherein the co-location information is indicative of whether co-location of the at least one third UP function (510, 806) and a second UP function (508) of the AN is preferred.

2. The method as claimed in claim 1, the method comprising: determining (516, 812), prior to initiating transmission of the first request, the site associated with the first UP function (504).

3. The method as claimed in claim 2, wherein determining (516, 812) the site associated with the first UP function (504) comprises: selecting the site associated with the first UP function (504); and / or identifying the site associated with the first UP function (504).

4. The method as claimed in any of the preceding claims, wherein the first node (10) comprises the first UP function (504).

5. The method as claimed in any of the preceding claims, the method comprising: selecting (534, 830), based on the identifier information and the co-location information, a first entity of the AN to be configured to support the PDU session, wherein the first entity of the AN comprises the second UP function (508).

6. The method as claimed in claim 5, wherein if the co-location information is indicative that co-location of the at least one third UP function (510, 806) and the second UP function (508) is not preferred, selecting (534, 830) the first entity of the AN comprises: selecting a first entity of the AN based on one or more policies configured for the AN.

7. The method as claimed in claim 5 or 6, wherein if the co-location information is indicative that co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred, selecting (534, 830) the first entity of the AN comprises: selecting a first entity of the AN that is associated with the site associated with the at least one third UP function (510, 806).

8. The method as claimed in any of claims 5 to 7, wherein the first entity of the AN is selected to establish a UP tunnel between the first entity and the at least one third UP function (510, 806).

9. The method as claimed in any of the preceding claims, wherein initiating (202, 518, 814) transmission of the first request comprises: initiating transmission of the first request towards the second node (20) via a first CN function (508, 804).

10. The method as claimed in claim 9, wherein receiving (204, 532, 828) the first response message comprises: receiving the first response message from the second node (20) via the first CN function (508, 804).

11. The method as claimed in claim 9 or 10, wherein the first CN function (508, 804) is configured to operate as an access and mobility management function, AMF.

12. The method as claimed in any of the preceding claims, wherein the first request is requested by a wireless device (502, 802) of the AN.

13. The method as claimed in any of the preceding claims, wherein the site information is indicative of the site at which the first UP function (504) is located in the AN.

14. The method as claimed in any of the preceding claims, wherein the site information comprises one or more of: an internet protocol, IP, address of the first UP function (504); a cell identifier, ID, of the first UP function (504); a registration area ID of the first UP function (504); an AN paging area ID of the first UP function (504); and a geographic location of the first UP function (504).

15. The method as claimed in any of the preceding claims, wherein the co-location information comprises a flag indicative of whether co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred.

16. The method as claimed in any of the preceding claims, wherein the identifier information comprises a transport address of the at least one third UP function (510, 806).

17. The method as claimed in any of the preceding claims, wherein the AN is a radio AN, RAN.

18. The method as claimed in any of the preceding claims, wherein the second node (20) is configured to operate as a session management function, SMF.

19. A method for handling a packet data unit, PDU, session in a network, wherein the network comprises an access network, AN, and a core network, CN, the method being performed by a second node (20) of the CN, wherein the second node (20) is configured to provide CN control plane, CP, functionality, the method comprising: receiving (302, 522, 818), from a first node (10) of the AN, a first request for establishment of a PDU session, wherein the first request comprises site information indicative of a site associated with a first user plane, UP, function (504) of the AN, and wherein the first node (10) is configured to provide AN CP functionality; and initiating (304, 530, 826) transmission of a first response message towards the first node (10), wherein the first response message comprises identifier information and location information, wherein the identifier information is indicative of at least one third UP function (510, 806) selected to support the PDU session, wherein the at least one third UP function (510, 806) is selected based on the site information, and wherein thelocation information is indicative of whether co-location of the at least one third UP function (510, 806) and a second UP function (508) of the AN is preferred.

20. The method as claimed in claim 19, the method comprising: determining whether co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred.

21. The method as claimed in claim 20, wherein determining whether co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred is based on: the site information; and / or one or more requirements associated with the PDU session.

22. The method as claimed in any of claims 19 to 21 , the method comprising: selecting (524 820), based on the site information, the at least one third UP function (510, 806).

23. The method as claimed in claim 22, wherein selection of the at least one third UP function (510, 806) is further based on: one or more policy control function, PCF, policies; and / or user data management, UDM, information.

24. The method as claimed in claim 22 or 23, wherein the at least one third UP function (510, 806) is selected from a plurality of third UP functions.

25. The method as claimed in any of claims 19 to 24, wherein the first node (10) comprises the first UP function (504).

26. The method as claimed in any of claims 19 to 25, wherein receiving the first request comprises: receiving (302, 522, 818) the first request from the first node (10) via a first CN function (508, 804).

27. The method as claimed in claim 26, wherein initiating (304, 530, 826) transmission of the first response message comprises:initiating transmission of the first response message towards the first node (10) via the first CN function (508, 804).

28. The method as claimed in claim 26 or 27, wherein the first CN function (508, 804) is configured to operate as an access and mobility management function, AMF.

29. The method as claimed in any of claims 19 to 28, wherein the first request is requested by a wireless device (502, 802) of the AN.

30. The method as claimed in any of claims 19 to 29, wherein the site information is indicative of the site at which the first UP function (504) is located in the AN.

31. The method as claimed in any of claims 19 to 30, wherein the site information comprises one or more of: an internet protocol, IP, address of the first UP function (504); a cell identifier, ID, of the first UP function (504); a registration area ID of the first UP function (504); an AN paging area ID of the first UP function (504); and a geographic location of the first UP function (504).

32. The method as claimed in any of claims 19 to 31 , wherein the co-location information comprises a flag indicative of whether co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred.

33. The method as claimed in any of claims 19 to 32, wherein the identifier information comprises a transport address of the at least one third UP function (510, 806).

34. The method as claimed in any of claims 19 to 33, wherein the AN is a radio AN, RAN.

35. The method as claimed in any of claims 19 to 34, wherein the second node (20) is configured to operate as a session management function, SMF.

36. A method for handling a packet data unit, PDU, session in a network, wherein the network comprises an access network, AN, and a core network, CN, the method being performed by at least one control node (30) of the network, wherein the at least onecontrol node (30) is configured to provide user plane, UP, control functionality, the method comprising: determining (402) that a second UP function (508) of the AN and at least one third UP function (510, 806) are to be co-located in the network, wherein the at least one third UP function (510, 806) is selected to support a PDU session; and configuring (404) the second UP function (508) and the at least one third UP function (510, 806) to support the PDU session in a co-location configuration.

37. The method as claimed in claim 36, wherein configuring (404) the second UP function (508) and the at least one third UP function (510, 806) to support the PDU session in the co-location configuration comprises: configuring a single binary to execute the second UP function (508) and the at least one third UP function (510, 806); configuring the second UP function (508) and the at least one third UP function (510, 806) to operate using a shared memory; and / or configuring the second UP function (508) and the at least one third UP function (510, 806) to forward information associated with the PDU session to the other of the at least one third UP function (510, 806) and the second UP function (508).

38. The method as claimed in claim 37, wherein the information associated with the PDU session comprises: one or more data packets associated with the PDU session; and / or a tunnel identifier, TEID, associated with the PDU session.

39. The method as claimed in any of claims 36 to 38, wherein determining (402) that the second UP function (508) of the AN and the least one third UP function (510, 806) are to be co-located in the network comprises: obtaining a second request from a first node (10) of the AN and a second node (20) of the CN, wherein the first node (10) is configured to provide AN control plane, CP, functionality, wherein the second node (20) of the CN is configured to provide CN CP functionality, and wherein the second request comprises a request to configure the second UP function (508) and the at least one third UP function (510, 806) to support the PDU session.

40. The method as claimed in claim 39, wherein the second request comprises an identifier of the PDU session.41 . The method as claimed in any of claims 36 to 40, wherein the at least one control node (30) comprises: a first control node (30a) configured to provide UP control functionality for the second UP function (508); and a second control node (30b) configured to provide UP control functionality for the at least one third UP function (510, 806).

42. The method as claimed in claim 41 , wherein determining (402) that the second UP function (508) and the least one third UP function (510, 806) are to be co-located in the network is based on: an IP address of the first control node (30a); and / or an IP address of the second control node (30b).

43. The method as claimed in any of claims 36 to 42, wherein configuring (404) the second UP function (508) and the at least one third UP function (510, 806) to support the PDU session in the co-location configuration comprises: providing co-location information to the second UP function (508) and / or the at least one third UP function (510, 806), wherein the co-location information is indicative that the second UP function (508) and the at least one third UP function (510, 806) are to be co-located in the network.

44. The method as claimed in claim 43, wherein the co-location information comprises a flag indicative of whether co-location of the at least one third UP function (510, 806) and the second UP function (508) is preferred.

45. A method performed by a system, the method comprising: the method as claimed in any of claims 1 to 18; the method as claimed in any of claims 19 to 35; and / or the method as claimed in any of claims 36 to 44.

46. A first node (10) comprising: processing circuitry (12) configured to operate in accordance with any of claims 1 to 18.

47. A first node (10) as claimed in claim 46, wherein: the first node (10) comprises:at least one memory (14) for storing instructions which, when executed by the processing circuitry (12), cause the first node (10) to operate in accordance with any of claims 1 to 18.

48. A second node (20) comprising: processing circuitry (22) configured to operate in accordance with any of claims 19 to 35.

49. A second node (20) as claimed in claim 48, wherein: the second node (20) comprises: at least one memory (24) for storing instructions which, when executed by the processing circuitry (22), cause the second node (20) to operate in accordance with any of claims 19 to 35.

50. A control node (30) comprising: processing circuitry (32) configured to operate in accordance with any of claims 36 to 44.

51. A control node (30) as claimed in claim 5, wherein: the control node (30) comprises: at least one memory (34) for storing instructions which, when executed by the processing circuitry (32), cause the control node (30) to operate in accordance with any of claims 36 to 44.

52. A system comprising: at least one first node (10) as claimed in claim 46 or 47; at least one second node (20) as claimed in claim 48 or 49; and at least one control node (30) as claimed in claim 50 or 51.

53. A computer program comprising instructions which, when executed by processing circuitry, cause the processing circuitry to perform the method according to any of claims 1 to 18, any of claims 19 to 35, and / or any of claims 36 to 44.

54. A computer program product, embodied on a non-transitory machine-readable medium, comprising instructions which are executable by processing circuitry to causethe processing circuitry to perform the method according to any of claims 1 to 18, any of claims 19 to 35, and / or any of claims 36 to 44.

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