COMMUNICATION NETWORK

TECHNICAL FIELD

In general, the present invention relates to communication networks. More specifically, the present invention relates to systems and methods for providing network functions in a communication network comprising an access network and a core network. BACKGROUND

In current mobile networks, i.e. 4G LTE systems, the Core Network (CN) has a static architecture. Network Control Plane (CP) and User Plane (UP) functions are provided by the fixed network elements of the CN, such as a Mobility Management Entity (MME), a Serving Gateway (SGW), a PDN Gateway (PGW) and the like. These network elements serve all the network traffic that passes through the Evolved Packet Core (EPC) regardless of the type of services associated with the network traffic. Therefore, it is not possible to enable service- tailored network function provisioning based on such a system architecture. The CP protocol stack between a User Equipment (UE), a MME and SGW is defined in 3GPP TS 23.401 V13.2.0, "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access". The NAS (non- access stratum) protocol supports mobility management functionality and user plane bearer activation, modification and deactivation. It is also responsible for ciphering and integrity protection of NAS signaling.

The LTE architecture consists of a fixed yet configurable protocol stack, where interactions between peer entities are based on specific sets of control and user plane procedures. Some of the protocols are quite complex and usually include more than one function since they have been designed to cater for general purpose end devices. However, current 4G mobile telecommunication systems have the following major limitations.

The current 4G mobile telecommunication system has a static reference architecture model. The physical network entities (i.e. MME, SGW and PGW) have a fixed placement and are normally at a central location (e.g. regional or central office of operators). Such Core Network (CN) design does not have a lot of flexibility and dynamicity, which makes it not capable to tackle use cases with high diversity requirements (e.g. very low latency, massive number of devices, etc.).

Use cases for future 5G communication networks comprise extreme use cases with different traffic models, which may cause problems for current communication networks, such as an inefficient CN Control Plane (CP) signalling to support User Plane (UP) traffic (e.g. for a massive loT use case), an inefficient CN CP support for mobility related events, e.g. the CN CP entity is notified about all handover events and device state changes from active to idle and vice versa.

Moreover, the network entities defined in the EPC of 4G communication networks that provide CP functionalities are not designed to tackle Multiple Radio Access technology (RAT). For instance, 4G mobile telecommunication systems CP functionalities, such as the paging and handover procedures, are access-specific functions. To achieve this goal, the system relies on an interworking mechanism, which is not a native way to support devices with different access requirements (e.g. non-3GPP). This leads to lack of flexibility and sub- optimal utilization of resources in the access and core networks.

In light of the above, there is a need for improved devices and methods for providing network functions in a communication network comprising an access network and a core network.

SUMMARY

It is an object of the invention to provide a new system and method for providing network functions in a communication network comprising an access network and a core network. The foregoing and other objects are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. Generally, the invention relates to a system and methods to enable dynamicity of modularized Control Plane (CP) network functions for next generation mobile core networks in terms of CP function design, placement and operation. Moreover, the present invention allows the usage of different type of access technology that uses the same core network and allows reducing signalling between the access network and core network.

More specifically, according to a first aspect the invention relates to a system for providing a network function (NF) in a communication network, the communication network comprising a core network and an access network for providing access to the core network. The system comprises: an access network entity being associated with the access network, wherein the access network entity is configured to provide a first set of network functions (NF _a ) including one or more network functions configured to process messages in a control plane of the access network; and a core network entity being associated with the core network, wherein the core network entity is configured to provide a second set of network functions (NF _C ) including one or more network functions configured to process messages in a control plane of the core network; wherein the network function (NF) in the communication network is provided by the collaboration or cooperation between the first set of network functions (NF _a ) and the second set of network functions (NF _C ) and wherein the network function (NF) is configured to provide control plane network services.

As used herein, the processing of messages in the control plane of the access network and the core network means the processing of service signalling, e.g., non-access stratum (NAS) signalling, in the control plane, which generally includes the triggering of certain control plane actions, such as mobility handling, trigger authentication, and the like. In other words, the first set of network functions (NF _a ) and the second set of network functions (NF _C ) must at least partially "understand" and process the message. Forwarding a message is not considered as processing of the message.

Thus, an improved system for providing network functions in a communication network comprising an access network and a core network is provided.

In a first possible implementation form of the system according to the first aspect as such, the access network entity is a wireless access point configured to provide a user device access to the communication network.

In a second possible implementation form of the system according to the first aspect as such, the system comprises a control plane anchor point, wherein the first set of network functions (NF _a ) is implemented as the control plane anchor point. Multiple wireless access points may connect to the same control plane anchor point.

As used herein, a "control plane anchor point", or control plane agent, is an entity for anchoring the control plane signalling between the access network and the core network, i.e. it is physically located between the access network and the core network, the control plane signaling traffic between access network and core network need to go through control plane anchor point. Hence, wireless access points do not have direct interface with NFc. One control plane anchor point may connect to multiple wireless access points, and it has interface towards NFc.

In a third possible implementation form of the system according to the first aspect as such, the access network comprises a wireless access point for providing a user device access to the communication network, wherein the first set of network functions (NF _a ) comprises an interface for communicating with the wireless access point and wherein the second set of network functions (NF _C ) comprises an interface for communicating with the wireless access point. Multiple wireless access points may connect to the same NF _a and multiple wireless access points may connect to the same NF _C .

In a fourth possible implementation form of the system according to the first aspect as such or any one of the first to third implementation form thereof, the second set of network functions (NF _C ) and the first set of network functions (NF _a ) are configured to exchange context information by means of a context relocation procedure, wherein the context information comprises information for processing control plane messages.

In a fifth possible implementation form of the system according to the fourth implementation form of the first aspect, the context relocation procedure comprises an exchange of a context relocation message between the second set of network functions (NF _C ) and the first set of network functions (NF _a ) and wherein the context relocation message is configured to comprise the context information as well as a control plane message associated therewith.

In a sixth possible implementation form of the system according to the fifth implementation form of the first aspect, the access network entity is a wireless access point configured to provide a user device access to the communication network, wherein the first set of network functions (NF _a ) is configured, in response to receiving a control plane message from the wireless access point, to send a context relocation message including the control plane message to the second set of network functions (NF _C ) for processing of the control plane message by the second set of network functions (NF _C ), in case the control plane message cannot be processed by the first set of network functions (NF _a ).

In a seventh possible implementation form of the system according to the fifth

implementation form of the first aspect, the system comprises a control plane anchor point, wherein the first set of network functions (NF _a ) is implemented on the control plane anchor point and wherein the first set of network functions (NF _a ) is configured, in response to receiving a control plane message from a wireless access point, to send a context relocation message including the control plane message to the second set of network functions (NF _C ) for processing of the control plane message by the second set of network functions (NF _C ), in case the control plane message cannot be processed by the first set of network functions (NF _a ).

In an eighth possible implementation form of the system according to the fifth implementation form of the first aspect, the access network comprises a wireless access point for providing a user device access to the communication network, wherein the first set of network functions (NF _a ) comprises an interface for communicating with the wireless access point, wherein the first set of network functions (NF _a ) is configured, in response to receiving a control plane message from the wireless access point, to send a context relocation message including the control plane message to the second set of network functions (NF _C ) for processing of the control plane message by the second set of network functions (NF _C ), in case the control plane message cannot be processed by the first set of network functions (NF _a ).

In a ninth possible implementation form of the system according to the fifth implementation form of the first aspect, the access network comprises a wireless access point for providing a user device access to the communication network, wherein the second set of network functions (NF _C ) comprises an interface for communicating with the wireless access point, wherein the second set of network functions (NF _C ) is configured, in response to receiving a control plane message from the wireless access point, to process the control plane message and send a context relocation message including the control plane message and the context information associated with the control plane message to the first set of network functions (NF _a ) for processing of future control messages by the first set of network functions (NF _a ).

In a tenth possible implementation form of the system according to the first aspect as such or any one of the first to ninth implementation form thereof, the network function (NF) in the communication network is provided by the collaboration or cooperation between the first set of network functions (NF _a ) and the second set of network functions (NF _C ) in a cooperative operation mode or an autonomous operation mode, wherein in the cooperative operation mode the first set of network functions (NF _a ) and the second set of network functions (NF _C ) comprise different functions and wherein in the autonomous operation mode the first set of network functions (NF _a ) and the second set of network functions (NF _C ) at least partially comprise the same functions.

In an eleventh possible implementation form of the system according to the first aspect as such or any one of the first to tenth implementation form thereof, the network function (NF) comprises at least one of the following functions: connection management functions, such as performing radio connection management, forwarding path management, DNS address resolution, or address allocation to user devices; mobility management functions, such as checking user reachability, tracking area management, paging and handover management, or relaying; forwarding management functions, such as performing packet routing

configuration for a user plane of the communication network; authentication and

authorization functions, such as performing authentication and authorization of a user device; or security functions, such as performing access network security management. According to a second aspect the invention relates to an access network entity for an access network of a communication network, the access network providing access to a core network of the communication network, wherein the access network entity is configured to provide a first set of network functions (NF _a ) including one or more network functions configured to process messages in a control plane of the access network, wherein the first set of network functions is configured to provide a network function (NF) in the communication network for providing control plane network services by cooperating with a second set of network functions (NF _C ), wherein the second set of network functions (NF _C ) is provided by a core network entity being associated with the core network and wherein the second set of network functions (NF _C ) comprises one or more network functions configured to process messages in a control plane of the core network.

According to a third aspect the invention relates to a core network entity for a core network of a communication network, the communication network further comprising an access network for providing access to the core network, wherein the core network entity is configured to provide a second set of network functions (NF _C ) including one or more network functions configured to process messages in a control plane of the core network, wherein the second set of network functions is configured to provide a network function (NF) in the

communication network for providing control plane network services by cooperating with a first set of network functions (NF _a ), wherein the first set of network functions (NF _a ) is provided by an access network entity being associated with the access network and wherein the first set of network functions (NF _a ) comprises one or more network functions configured to process messages in a control plane of the access network.

According to a fourth aspect the invention relates to a method for providing a network function (NF) in a communication network, the communication network comprising a core network and an access network for providing access to the core network. The method comprises: providing a first set of network functions (NF _a ) in the access network, wherein the first set of network functions (NF _a ) includes one or more network functions configured to process messages in a control plane of the access network; providing a second set of network functions (NF _C ) in the core network, wherein the second set of network functions (NFc) includes one or more network functions configured to process messages in a control plane of the core network; and providing the network function (NF) in the communication network by the collaboration between the first set of network functions (NF _a ) and the second set of network functions (NF _C ), wherein the network function is configured to provide control plane network services. The method according to the fourth aspect of the invention can be performed by the system according to the first aspect of the invention. Further features and implementation forms of the method according to the fourth aspect of the invention result directly from the functionality of the system according to the first aspect of the invention and its different implementation forms.

According to a fifth aspect, the invention relates to a computer program comprising program code for performing the method of the fourth aspect when executed on a computer.

The invention can be implemented in software and/or in hardware.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, wherein:

Fig. 1 shows a schematic diagram illustrating the architecture of a communication network with an access network and a core network;

Fig. 2 shows a schematic diagram illustrating a configuration procedure between a first set of network functions and a second set of network functions according to an embodiment of the invention;

Figs. 3a and 3b show schematic diagrams illustrating the collaboration between a first set of network functions and a second set of network functions according to embodiments of the invention; Figs. 4a and 4b show an implementation of a first set of network functions and a second set of network functions according to an embodiment of the invention, wherein the first set of network functions is integrated with an access point (AP), and a context relocation procedure according to an embodiment of the invention;

Figs. 5a and 5b show an implementation of a first set of network functions and a second set of network functions according to an embodiment of the invention, wherein the first set of network functions is a CP anchor point, and a context relocation procedure according to an embodiment of the invention;

Figs. 6a, 6b and 6c show an implementation of a first set of network functions and a second set of network functions according to an embodiment of the invention, wherein the first set of network functions and the second set of network functions have direct interfaces with an access point (AP), and context relocation procedures according to embodiments of the invention;

Figs. 7a, 7b and 7c show different implementations of a network attach procedure based on a first set of network functions and a second set of network functions according to embodiments of the invention;

Figs. 8a, 8b and 8c show different implementations of a device triggered service request procedure based on a first set of network functions and a second set of network functions according to embodiments of the invention; Figs. 9a and 9b show different implementations of a mobility related policy configuration procedure based on a first set of network functions and a second set of network functions according to embodiments of the invention;

Figs. 10a and 10b show different implementations of a location tracking policy configuration procedure based on a first set of network functions and a second set of network functions according to embodiments of the invention;

Figs. 1 1 a, 1 1 b and 1 1 c show different implementations of a location update procedure based on a first set of network functions and a second set of network functions according to embodiments of the invention; and Fig. 12 shows a schematic diagram of a method of providing a network function according to an embodiment.

In the figures, identical reference signs will be used for identical or functionally equivalent features.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and in which are shown, by way of illustration, specific aspects in which the present invention may be placed. It will be appreciated that the invention may be placed in other aspects and that structural or logical changes may be made without departing from the scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, as the scope of the invention is defined by the appended claims.

For instance, it will be appreciated that a disclosure in connection with a described method will generally also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures.

Moreover, in the following detailed description as well as in the claims, embodiments with functional blocks or processing units are described, which are connected with each other or exchange signals. It will be appreciated that the invention also covers embodiments which include additional functional blocks or processing units that are arranged between the functional blocks or processing units of the embodiments described below.

Finally, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

Embodiments of the invention can be implemented in a communication network 100, which has a general architecture as shown in figure 1 . The communication network 100 comprises a core network 104 and an access network 103. The access network 103 is configured to provide an exemplary user equipment 105 (herein also referred to as user device) access to the core network 104 of the communication network 100. The core network 104, the access network 103 and the user equipment 105 can communicate via a control plane (herein also referred to as C-Plane or CP) 101 and a user or data plane 102 (herein also referred to as U- Pane or UP), i.e. in the communication network 100 there is a separation between the control plane 101 and the user plane 102. The control plane 101 consists of protocols to control and support the user plane 102 functions. In conventional mobile communication networks, a CP network entity, such as the MME, is physically located in the CN and is configured to process CP signaling from the AN.

As will be described in more detail below, a first set of network functions (also referred to as NFa herein) 106-1 , 106-2 is implemented to operate in the control plane 101 of the access network 103 and a second set of network functions (also referred to as NFc herein) 107-1 , 107-2 and 107-3 is implemented to operate in the control plane 101 of the core network 104.

An embodiment of the invention relates to a system for providing a composite network function NF in the communication network 100. The system comprises an access network entity being associated with the access network 103, wherein the access network entity is configured to provide the first set of network functions NFa including one or more network functions 106-1 , 106-2 configured to process messages in the control plane 101 of the access network 103. Moreover, the system comprises a core network entity being associated with the core network 104, wherein the core network entity is configured to provide the second set of network functions NFc including one or more network functions 107-1 , 107-2, 107-3 configured to process messages in the control plane 101 of the core network 104. The first set of network functions NFa and the second set of network functions NFc are

configured to cooperate in such a way that the composite network function NF in the communication network 100 is provided by the cooperation between the first set of network functions NFa and the second set of network functions NFc, wherein the composite network function NF is configured to provide network services in the control plane 101 of the communication network 100.

As used herein, the processing of messages in the control plane of the access network and the core network is not a simple forwarding of messages, but rather the processing of non- access stratum (NAS) signaling in the control plane, which generally includes the triggering of certain control plane actions, such as mobility handling, trigger authentication, and the like.

The network architecture for supporting embodiments of the invention may be either realized according to Network Function Virtualization (NFV) and Software Defined Networks (SDN) paradigms or may rely on dedicated hardware appliances or entities. The CP and the UP for mobile telecommunication networks may be built upon virtual and/or physical infrastructures, including wireless Access Points (APs), Data Centers, Edge Data Centers or Points of Presence, interconnected by a transport network realized either by legacy connectivity methods or by virtual links, virtual switches and virtual routers controlled by SDN controllers.

The CP of a mobile network is generally composed of a set of control applications, i.e.

access network functions (NFa) and core network functions (NF), for Access and Non- Access Stratum (NAS) control, respectively. As shown in Figure 1 , the network functions of the first set of network functions NFa and the network functions of the second set of network functions NFcs can be interconnected via logical interconnections. The network functions of the first set of network functions NFa can be either implemented as SDN control applications, for instance, by means of an interaction with an SDN controller via dedicated APIs, or they can be implemented as software running on virtual machines in Data Centers (DC), edge Data Centers or Points of Presence (PoP) environment or other entities, which provide computing and/or storage resources. The first set of network functions NFa can perform access related functionalities including connection management actions, and possibly access network selection related actions. The basic components of the first set of network functions NFa can be defined analyzing the key functionalities of legacy mobile networks. Referring to 4G systems, they could be associated to Mobility, Security and Session Management functions and related protocols, e.g. as specified in 3GPP TS 36.300 R13, "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2". Also, a number of transmission functions can be performed at the physical layer.

According to embodiments of the invention the network functions of the first set of network functions NFa can be, for instance, connection management functions, such as performing radio connection management, forwarding path management, DNS address resolution, or address allocation to user devices; mobility management functions, such as checking user reachability, tracking area management, paging and handover management, or relaying; forwarding management functions, such as performing packet routing configuration for a user plane of the communication network; authentication and authorization functions, such as performing authentication and authorization of a user device; or security functions, such as performing access network security management.

As already described above, the control plane 101 of the communication network 100 shown in figure 1 may be provided with one or more composite network functions (NFs). According to an embodiment of the invention, a composite network function (NF) is a logical network entity, which comprises two logical sub-entities, namely the first set of network functions NFa and the second set of network functions NFc. In an embodiment, the definition of NFc and NFa depends on the placement of the sub-entities as such, as will be described in more detail further below. NFc denotes the part of the NF located in the CN 104 and NFa denotes the part of the NF located in the AN 103. In an embodiment, the logical relationship between NF, NFc and NFa can be defined as follows:

NF := NFc + NFa, (if NFa ≠ Φ) which indicates that, NFc is a compulsory component and NFa is an optional component. If there is NFa defined and deployed in AN, NFc and NFa together behave as one NF.

According to an embodiment, the first set of network functions NFa and the second set of network functions NFc can be configured to cooperate in a cooperative operation mode or an autonomous operation mode, wherein in the cooperative operation mode the first set of network functions NFa and the second set of network functions NFc comprise different functions and wherein in the autonomous operation mode the first set of network functions NFa and the second set of network functions NFc at least partially comprise the same functions. If the relationship between the NFa and the NFc is cooperative (cooperative operation mode), meaning that the NFa provides the service that handles the request for network service from the user device 105 only within the scope of access network 104, the NFc provides the service that handles the cases that cannot be handled by the NFa. In such a case, the functions provided by the NFa and the NFc do not overlapped.

For different access networks, the first set of network functions NFa may have different implementations in order to tackle different access network types. For instance, a first set of network functions NFa designed for mobility purpose may have different protocols for an access network enabled by LTE and an access network enabled by WiFi. To enable a mobile communication network with multiple access technologies, the relationship between the composite network function NF, the second set of network functions NFc and the first set of network functions NFa can be further extended according to embodiments of the invention in the following way for a communication network with n type of access technologies: If the first set of network functions NFa is a clone of the second set of network functions NFc, the relationship between NFa and NFc is autonomous, i.e. they cooperate in the autonomous operation mode, meaning the first set of network functions NFa provides the same functions as the second set of network functions NFc at a different location.

In an embodiment, the first set of network functions NFa is implemented in the AN 103 so that one NFc can connect to multiple NFas, but one NFa connects to only one NFc.

The first set of network functions NFa and the second set of network functions NFc can interconnect with each other in different ways, e.g. based on IP or non-IP connections. In an embodiment, the second set of network functions NFc is configured to identify different first sets of network functions NFas, for instance on the basis of respective identifiers of the different first sets of network functions, and the CP traffic can be routed between NFa and NFc.

In an embodiment, the NFa, the NFc and the NF are all programmable network entities, which can be dynamically configured by a management system of the communication network 100. In an embodiment, the NFc and the NFa can be instantiated once a logical network is established. They can also be instantiated during the operation of the network 100, for instance, in case a NFa terminates, a new NFa can be instantiated to take over the role of the terminated NFa. In an embodiment, the NFc is configured to obtain information about the NFa, e.g. the address of and an identifier to locate and communicate with the NFa, e.g. during the instantiation phase, using a network function discovery method or provided by the management system of the communication network 100.

The operational mode between the NFc and the NFa, i.e. the "cooperative operation mode" or the "autonomous operation mode" can be defined during the instantiation phase according to a logical network template, which is used to specify the included CP NFs and the interconnection relationship between these NFs. Different embodiments of NFs can select different operational modes. For instance, NFs for mobility management may use the cooperative operation mode, whereas NFs for authentication may use the autonomous cooperation mode.

According to embodiments of the invention, there are two phases defined to enable the cooperation between the NFa and the NFc, namely a configuration phase and an operation phase. The configuration phase is used for NFa management and maintenance purpose. During the configuration phase, the NFc can configure the NFa via a "NFc-NFa configuration procedure" as shown in Figure 2. The configuration phase can be triggered by different events. For instance, after the NFa and the NFc are instantiated, the NFc configures the NFa to install the data required for operational use. In an embodiment, the NFc updates the NFa with the data required for operational use during the operation phase, which will be described in more detail further below.

In step 1 of figure 2, the NFc sends a NFa configuration message to the NFa. This message can include a set of configuration data, which will be taken by the NFa into operational use, for instance, NFa operational related policies and rules. Such policies and rules can be used to define a NFa operation related configuration (e.g. enable or disable certain features of the NFa, setting parameters, etc.). In step 2 of figure 2, the NFa responds to the NFc with a NFa configuration ACK message to acknowledge that the NFa has updated its configuration successfully or not.

The operation phase refers to the time period, when the NFa and the NFc are used to process CP messages. In an embodiment, the network function NF can be dynamically provisioned by the system as such, i.e. the first set of network functions NFa and the second set of network functions NFc cooperate, i.e. work together to process certain CP messages in order to optimize CP performance. To this end, embodiments of the invention are based on a context relocation procedure, as shown in figures 3a and 3b. Here "context" or "context information" refers to the information required by a network function to process (certain) CP messages. For instance, such context could be device related or service related, e.g. device subscription information, security key, session information, location information, etc. The context relocation procedure can be used to transfer the context information which is necessary to process certain CP messages from the NFc to the NFa or vice versa. The procedure is shown in figures 3a and 3b, which can be triggered either by the NFc or by the NFa.

The side that triggers the context relocation (CR) procedure is denoted as the "source entity", and the side receiving the CR message is denoted as the "target entity". In an embodiment, the context relocation procedure is triggered after the source entity receives a CP message (e.g. either from the other NFs or from an access point directly). After the source entity has processed the CP message, based on the processing results, the source entity may make the decision to relocate all relevant context information and/or the CP message to the target entity.

In an embodiment, the context relocation procedure contains two major messages, namely the Context Relocation (CR) message and the Context Relocation Response (CRR) message. The CR message can have two components: context information and the CP message that needs to be processed, which is denoted as [context X, CP message Y]. According to embodiments of the invention the following scenarios can occur (wherein "NULL" means empty and "-NULL" means non empty):

• If CR message = [NULL, -NULL], it means that the source does not contain any information to process the control plane message Y. Therefore, the message Y is transferred to the target for further processing. · If CR message = [-NULL, -NULL], it means that the context information X from the source is not sufficient to process the message Y. Therefore, the source relocates the context X to allow the target to process the message Y.

• If CR message = [-NULL, NULL], it means that the source simply relocates the context X to the target.

The CRR message has two components, namely context information and the CP message after processing by the target. According to embodiments of the invention the following scenarios can occur (wherein the components of the CRR message are denoted as [context W, message U]):

• If CRR message = [NULL, NULL], it means that the target simply acknowledges the source that it has received the CR message. · If CRR message = [-NULL, NULL], it means that the context information X in the CR message has been updated to W and is relocated back to the source.

• If CRR message = [-NULL, -NULL], it means that the context information X in the CR message has been updated to W and is relocated back to the source together with a message U. The message U is generated by the target after processing the message Y. The source sends out the message U afterwards. • If CRR message = [NULL, -NULL], it means there is no context information relocated back to the source. The message U is generated by the target after processing the message Y. Therefore, the source simply sends out the message U and sets the context to NULL (or removes the context).

To optimize the CP operation, in an embodiment the NFc is configured to let a NFa serve certain type of devices (e.g. devices with no or low mobility, etc.). To this end, the NFc can send the device context to the NFa via a Context Relocation (CR) message as indicated by Figure 3a, and the NFa responds to the NFc with a Context Relocation Response (CRR) message to acknowledge the receipt of the device context. The NFa may reject the context relocation request from the NFc and indicate in the CRR message, for instance, that it is overloaded.

After the NFa receives a CP signaling message for processing, it may still trigger the context relocation from the NFa to the NFc for the following reasons. Firstly, due to possible functional limitations of the NFa (e.g. the NFa does not contain the complete set of network functions as the NFc), the NFa can rely on the NFc to complete the CP signaling message processing; Secondly, due to having insufficient context information available, the NFa may not be capable to process certain CP messages (e.g. because the NFa is implemented in the AN 103, it may not contain a complete information set that is required to perform certain network functions). Therefore, the NFa can relocate the context information back to the NFc together with the CP message that it cannot process using the Context Relocation (CR) message as indicated in Figure 3b. After processing of the CP message, the NFc can reevaluates the source NFa (e.g. check if the current NFa is still appropriate to use, for instance, the device 105 may move from the access network 103 to another AN) and the following scenarios may occur:

The source NFa is still suitable. In this case, the NFc relocates all the related context information back to the NFa.

The source NFa is not suitable and the NFc decides to handle the user device that has triggered the CP signaling message itself.

The source NFa is not suitable and the NFc decides to use a new NFa. In this case, the NFc can relocate all the related context to the new NFa via the procedure as indicated in figure 3a. In an embodiment, the access network entity providing the first set of network functions NFa can be a wireless access point (AP) configured to provide the user device 105 access to the communication network 100. In other words, an AP (e.g. an eNB in a 4G LTE system) may comprise one or more of the network functions 106-1 and 106-2 of the first set of network functions NFa, i.e. the NFa can be implemented as part of the AP 401 shown in Figure 4a. As in this embodiment the NFa is integrated with the AP 401 , the AP 401 is generally configured to process the related CP message itself. It forwards the CP message to the NFc, only if it cannot process this message itself. Hence this embodiment supports the

cooperative operation mode.

Figure 4b shows an embodiment of the context relocation procedure for the embodiment shown in figure 4a, where the NFa is implemented as part of the AP 401 . The context relocation procedure shown in figure 4b comprises the following steps: 1 . The AP 401 comprising the first set of network functions NFa receives a CP

message from a user device 105.

2. The AP 401 processes the CP message. If the AP 401 can process the CP

message, it may go to step 7 and send a CP response to the user device 105.

3. Otherwise, the AP 401 sends a context relocation message to the NFc.

4. The NFc processes the CP message (if any).

5. The NFc sends the CR response to the AP 401 .

6. The AP 401 updates the context (if any) received from the NFc.

7. The AP 401 sends a CP response to the user device 105. As outlined, above steps 3 to 6 are optional, which can be triggered, for instance, in the two following scenarios. Firstly, if the AP 401 can process the CP message, steps 3 to 6 may be triggered to update the corresponding context at the NFc side. Secondly, if the AP 401 cannot process the CP message, it can use the context relocation procedure to forward the current context on the AP 401 (if there is any) together with the CP message to the NFc, and the NFc can process the CP message and send the processing results (updated context together with the CP response message) back to the AP 401 .

In a further embodiment, shown in figures 5a and 5b, the first set of network functions NFa can implemented as a logic entity which is located in-between the AN 103 and the CN 104, as illustrated in Figure 5a. In such an embodiment, the first set of network functions NFa plays the role of a CP anchor point, which means that the NFc is transparent for the user device 105 and the AN 103. Because in this embodiment the AP 401 does not have a direct interface with the NFc, this embodiment supports the cooperative operation mode. In an embodiment, where the first set of network functions NFa is implemented as a CP anchor point, the NFa preferably is topologically/geographically close to the AN 103. Figure 5b shows an embodiment of the context relocation procedure for the embodiment shown in figure 5a, where the NFa is implemented as a CP anchor point. As the only difference between the context relocation procedure shown in figure 5b and the context relocation procedure shown in figure 4b is that the access point 401 forwards the CP message to the NFa, which in this embodiment is not embedded in the AP 401 , reference is made to the above description of the different steps shown in figure 4b.

In a further embodiment shown in figures 6a-c, the NFa is implemented as an entity, which is located between the AN 103 and the CN 104. In such an embodiment, the NFa can be topological^ close to the AN 103. Different to the embodiment shown in figures 5a and 5b, the AP 401 in figure 6a also has an interface towards the NFc directly. Such an embodiment can enable autonomous operation modes, which means that the AP 401 can use either the NFa or the NFc to process CP messages.

Figures 6b and 6c show two embodiments of the context relocation procedure for the embodiment shown in figure 6a, where the NFa is implemented as entity located between the AN 103 and the CN 104. In the context relocation procedure shown in figure 6b the NFc is the major CP message processing entity, whereas in the context relocation procedure shown in figure 6C the NFa is the major CP message processing entity.

In the embodiment shown in figure 6b, the AP 401 forwards the CP message to the NFc for processing and, in response thereto, the NFc may send a CP message response to the AP 401 directly in step 4a. If NFc may evaluate a NFa, if it is more suitable to process CP messages from certain device 105, it may relocate the context via a CR message in step 4b to the NFa. Subsequently, the NFa takes over the role of the NFc and sends a CP message response to the AP 401 in step 6.

In the embodiment shown in figure 6c, the AP 401 forwards the CP message to the NFa for processing and, in response thereto, the NFa may send a CP message response to the AP 401 directly in step 4a. If the NFa cannot process this CP message, it may relocate the context via a CR message in step 4b and the NFc takes over the role of the NFa and sends a CP message response to the AP 401 in step 7. Embodiments of the invention provide connection management (CM) functions, such as radio connection management, forwarding path management, DNS address resolution, address allocation to the device 105. Two major procedures involving CM are the attach procedure and service request procedure, which will be described in the context of the present invention in the following.

Figures 7a-c illustrate attach procedures implemented by different embodiments of the present invention based on the different operation modes described above. The attach procedure embodiment shown in figure 7a, where the first set of network functions NFa comprises a connection management function CMa, which is integrated in the access point 401 , and the second set of network functions NFc comprises a connection management function CMc, comprises the following steps. Step 1 : At power on, the device 105 establishes network access connectivity according to the supported access technologies and the available access networks.

Step 2: After the network access connectivity establishment has been completed, the device 105 sends an Attach Request message to the AP 401 (in a further embodiment the Attach Request can also be piggybacked in step 1 ).

Step 3: Because the CMa is integrated with the AP 401 , the AP 401 processes the received Attach Request message in this step. Step 4: If the CMa cannot process this message, because it does not contain any context about the device 105, it triggers the context relocation procedure by sending the Context Relocation message with NULL context together with the Attach Request message to the CMc. Step 5: The CMc performs authentication and authorisation related actions based on a profile of the device 105. The CMc may contain a database that stores the profile of the device 105 or the CMc may obtain the device profile from an external database (e.g. from an HSS in the LTE EPC context). The CMc may also allocate a device ID after authentication and authorization.

Step 6: Based on the device profile, the CMc may decide to relocate device context from the CMc to the CMa. In an exemplary scenario the device can be a stationary sensor without location changes. In such an exemplary case, the CMc can send a Context Relocation Response message with attach acknowledgement and related context back to the AP 401 .

Step 7: If a UP forwarding path is required after the attachment (which could be optional), a forwarding path on the UP can be established at this stage. The AP 401 can issue a

Forwarding Path Establishment procedure together with the corresponding CP function that setups UP path.

Step 8: The AP 401 completes the Attach procedure sending the Attach Ack message to the device 105 via a RRC procedure.

The attach procedure embodiment shown in figure 7b, where the first set of network functions NFa comprises a connection management function CMa, which is implemented as a CP anchor point, and the second set of network functions NFc comprises a connection management function CMc, is rather similar to the embodiment shown in figure 7a. The only difference is that the CMa is implemented separately from the AP 401 . Therefore, the AP 401 forwards the Attach Request message to the CMa (as indicated by step 3). If the CMa can perform the authentication and authorization related procedure, it sends back a Attach ACK to the AP 401 directly. If the CMa cannot perform the authentication and authorization related procedure (e.g. it does not contain sufficient information about the device 105), it triggers the context relocation procedure by sending the Context Relocation message with NULL context together with the Attach Request message to the CMc (in step 5), which, in turn, triggers the authentication and authorisation procedure at the CMc (in step 6). In an embodiment, the CMc may contain a database that records the device profile, or the CMc may obtain the device profile from an external database (e.g. a HSS in the LTE EPC context). The CMc may also allocate a device ID after authentication and authorization. Based on the device profile, the CMc may decide to relocate device context from the CMc to the CMa (in step 7). After receiving the Attach ACK and the relocated context from the CMc, the CMa sends the Attach ACK back to the AP 401 (in step 8).

The user device 105 may power off after attaching to a network. If the device 105 is turned on again and performs an attach procedure, for the previous two embodiments, the CMa may already contain sufficient context to execute the attach procedure. For such cases, the CMc does not need to be involved in the procedure any more.

Figure 7c shows the attach procedure for an embodiment of the invention, where the first set of network functions NFa comprises a connection management function CMa and the second set of network functions NFc comprises a connection management function CMc and wherein both the first set of network functions NFa and the second set of network functions NFc have an interface with the access point 401 . In the attach procedure embodiment shown in figure 7c the AP 401 forwards the Attach Request message directly to the CMc. After the CMc completes the authentication and authorization procedure, it evaluates if the CMa can be used. If no suitable CMa can be used, CMc sends back an attach ACK directly to the AP 401 (in step 5. a). If a suitable CMa can be used, the CMc triggers a context relocation procedure to relocate the related context and Attach ACK message to the CMa (in step 5.b and 6) and the CMa sends the Attach ACK message back to the AP 401 (in step 7). The CMa may embed its own ID/address in the Attach ACK. Therefore, the AP 401 can use the CMa instead of the CMc to handle the events related to the user device 105. For this embodiment, an extension on the AP 401 can be provided, because the AP 401 should store device related information in order to use the CMc and the CMa at the same time. For instance, a user device with ID1 can be forwarded to the CMa for further processing, whereas a user device with ID2 can be forwarded to the CMc for further processing.

Figures 8a-c illustrate device triggered service request procedures implemented by different embodiments of the present invention based on the different operation modes described above. After the attach procedure shown in figures 7a-c, the CMa may already have sufficient context information to process a service request message from the device 105. Therefore, in the embodiments shown in figures 8a-c the CMc is not involved in the respective device triggered service request procedures. However, in all three embodiments, if the CMa does not have sufficient context to process a service request message, the CMa can trigger a context relocation procedure and the CMc processes the service request message.

In an embodiment, the first set of network functions NFa comprises a mobility management function MMa and the second set of network functions comprises a mobility management function MMc, wherein the mobility management function MMa and the mobility management function MMc cooperate to provide a composite mobility management function or entity MM. The Mobility Management function or entity MM can be configured to perform user reachability, tracking area management, paging and handover management, etc. In an embodiment, the cooperation between MMa and MMc can be used to enable the

enforcement of different mobility management policies. Embodiments of the procedures and the information flow related to a device in an active mobility state are discussed in the following. After the attach procedure, the CM (composed by the CMa and the CMc) authenticates the device and initial context can be created in different network entities in order to provide network services towards devices. Based on the device's subscription information, a mobility policy can be determined by the MMc. Such a mobility policy can be defined for devices based on the CP connection handling, for instance as in the following examples:

1 . Always connected after registration: For certain types of devices or use cases (e.g. critical communication), resources can be allocated for a device from the AN 103 to the CN 104 after its registration. Such allocated resources will not be released if the device registers with the system all the time.

2. Support the release and restore the AN and CN connection: For certain types of devices or use cases (e.g. enhanced Mobile Broad Band), resource can be allocated for a device from the AN 103 to the CN 104 after its registration, if the device 105 is in the active state. If the device 105 is in the idle state, the resources allocated between the AN 103 and the CN 104 can be released.

3. Do not support the release and restore the AN and CN connection: For certain types of devices or use cases (e.g. devices like sensors only send small amount of data), there is no need to setup a connection between the AN 103 and the CN 104.

According to embodiments of the invention, the mobility policy can also be defined based on user reachability levels, as in the following exemplary embodiments:

1 . No User Reachability (UR) support: when the user device 105 is in the idle state, it is not tracked by the network 105, i.e. it is not reachable by the network, e.g. no paging service is provided.

2. Limited UR support: UR is only supported in a fixed tracking area (which is

defined by the operator). Therefore, no area update is supported.

3. UR support: When the device 105 is in the idle state, it is tracked by the network at tracking area level, therefore it is always reachable by the network.

4. Extra UR support: When the device 105 is in the idle state, it is tracked by the network at cell level, therefore it is always reachable by the network. Such mobility related policies can be configured from MMc to MMa as illustrated in figures 9a and 9b.

Based on different mobility policies, the MMc can select the MMa and corresponding device context can be relocated from the MMc to the MMa, accordingly. Embodiments of the invention can be implemented in the following two major scenarios.

In a first scenario, wherein the mobility is handled in the AN only, the MMc relocates the device context (i.e. generated after an attach procedure) to the AP 401 , when it configures the MMa, and all the device related mobility events are handled by the MMa. If the MMa cannot handle certain events, such as a device handover from one AP to another AP that is not covered by the MMa, the MMa can reject to handle such events.

In a second scenario, where the mobility is handled by the AN and the CN together, the MMa and MMc entities operate in a cooperative mode, where the MMc relocates parts of the context for handling mobility (i.e. generated after an attach procedure) to the MMa, and for the device related mobility events the MMa is configured to handle it locally or on the basis of a minor interaction with the MMc. For the device mobility events the MMa has no context for handling. Thus, the MMa forwards the related CP signaling to the MMc (together with context) to handle such events. After the MMc processes the event, it sends back the response together with updated device context to the MMa. Such an event may result in a situation, where the MMc selects another MMa to handle the mobility related events for this device. In such a case, the MMc after processing the event can send the response together with updated device context back to the new MMa.

To ensure that the device 105 is reachable by the communication network, a location tracking (LT) function can be implemented by embodiments of the invention and used to track the device 105 when it is in idle state. Thus, in an embodiment, the first set of network functions NFa comprises a location tracking function LTa and the second set of network functions comprises a location tracking function LTc, wherein the location tracking function LTa and the location tracking function LTc cooperate to provide a composite location tracking function LT. Such an embodiment can also be applied for the CP function Location Tracking LT in order to support user reachability. Device location information is used by the communication network 100 to reach the device 105 for both CP signaling or UP data delivery. By using embodiments of the invention, certain access specific device location tracking functionality can be kept in the AN 103 or at least close thereto. In an embodiment, the LTa can collect a device's location information and report it to the LTc on behalf of the device. Since the location update in the CN 104 is independent from the individual RAT used in the AN 103 (e.g.,3GPP or non-3GPP, E-UTRAN or NextGen RAN), the CN 104 can have a unified composite LT function for different RATs, which facilitates the location management across different RATs.

In an embodiment, different LT policies can be configured from the LTc to the LTa. For instance, the LTa may be located in a 3GPP type AN 103 and, therefore, the LTa may support the location tracking mechanism defined by 3GPP. The LTa may be located in a non-3GPP type AN 103 and, therefore, the LTa may use an access dependent LT

mechanism, e.g. tracking changes of a WiFi access point and the like. Different LT policies can be configured from the LTc to the LTa using the embodiments shown in figures 10a-b.

In an embodiment, the LTa is configured to perform one of the following functions:

The LTa can be configured to perform access specific device location tracking in its coverage area according to the policy configured by the LTc, e.g.

tracking device signals to Remote Radio Unit (RRUs) in Cloud-RAN case, check the activeness/visibility of a MAC address and age of the attachment in Wifi case, track the device connectivity to small cells in dual connectivity case, etc.

The LTa can be configured to report the location changes of a device to the

LTc.

In an embodiment, the LTc is configured to perform one of the following functions:

The LTc can perform device location tracking at the granularity of the AN 103 level, which may involve different AN types or AN clusters in different areas.

The LTc can maintain LTa identifications, and an AN level tracking policy (e.g., Tracking area in RRC-idle, frequency of location report from the AN to the CN, etc.).

The LTc can maintain device identifications, and device level tracking policy, e.g. within the same AN (the tracking policy for sensors and for smart phones may be different). In an embodiment, the LTc can configure the AN level tracking policy as well as the device level tracking policy at the LTa.

Figure 1 1 a shows an embodiment of a location tracking procedure for the case, where the LTa is integrated in the access point 401 . In this embodiment, location tracking can be triggered by the device 105, e.g. by sending a CP message to the CN 104 to update its location (also known as tracking area update procedure). In an embodiment, location tracking can also be done without the triggering from the device 105, for instance, the network 100 can trace the radio signal strength of the device 105 and its direction (e.g. using advanced physical layer features from the access point 401 , for instance antenna array and beamforming related technology). The location tracking embodiment shown in figure 1 1 a comprises the following steps:

Step 1 : The AP 401 performs location tracking in the AN 103.

Step 2: Upon a change of the location of the device 105 as well as the location tracking policies configured by the LTc, the AP 401 relocates the device location related context (e.g. device local ID, AP ID, AN parameters, etc.) to the LTc. Step 3: The LTc acknowledges to the AP 401 the receipt of the location related context.

Step 4: Due to the location changes, forwarding path modification may be required for certain scenarios.

Figure 1 1 b, which shows a location tracking embodiment for the case, where the LTa is implemented as a CP anchor point, comprises the following steps:

Step 1 : The LTa performs location tracking in the AN 103.

Step 2: Responsive to a change of the location of the device 105 or a change of the location tracking policies configured by the LTc, the LTa relocates the device location related context (e.g. device local ID, AP ID, AN parameters, etc.) to the LTc.

Step 3: The LTc acknowledges to the LTa the receipt of the location related context. Step 4: Due to the location changes, forwarding path modification may be required for certain scenarios. Figure 1 1 c shows a location tracking embodiment for the case, where the LTa is implemented between the access network 103 and the core network 104 and both the LTa and the LTc have an interface with the access point 401 . Different to the embodiments shown in figures 1 1 a and 1 1 b, this embodiment can only support the scenario, where the location tracking is triggered by the device 105, e.g. sending the CP message to the CN 104 to update its location, e.g. on the basis of the tracking area update procedure defined in 3GPP TS 23.401 V13.2.0, "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access". The location tracking embodiment shown in figure 1 1 c comprises the following steps:

Step 1 : The device 105 detects location changes and sends updates to the corresponding AP 401 .

Step 2: The AP 401 forwards the location update CP message to the LTc.

Step 3: Due to the device profile (e.g. a sensor without mobility or low mobility, etc.), the LTc may relocate the device location context to the LTa and the LTa manages the device location afterwards. Step 4: The LTa acknowledges to the LTc the receipt of the location related context.

Step 5: Due to the location changes, forwarding path modification may be required for certain scenarios.

Figure 12 shows a schematic diagram of a method 1200 for providing a network function NF in the communication network 100. The method 1200 comprises the following steps: a first step 1201 of providing a first set of network functions NF _a in the access network 103, wherein the first set of network functions NF _a includes one or more network functions 106-1 , 106-2 configured to process messages in a control plane 101 of the access network 103; a second step 1203 of providing a second set of network functions NF _C in the core network 104, wherein the second set of network functions NF _C includes one or more network functions 107-1 , 107-2, 107-3 configured to process messages in a control plane 101 of the core network 104; and a third step 1205 of providing the network function in the communication network by the cooperation between the first set of network functions NF _a and the second set of network functions NF _C , wherein the network function NF is configured to provide control plane network services in the communication network 100. Embodiments of the invention provide for the following advantages, in particular. By providing a network function as a cooperation of access network functions and core network functions embodiments of the invention can improve the CN NF service provisioning efficiency and flexibility. Moreover, embodiments of the invention allow providing access- specific CN NF or NF sub-functions. Because the CN NF can be located in the access network, the NFa can be used instead of the NFc for specific scenarios (e.g. local network function provision for devices with low/no mobility). Therefore, embodiments of the invention can significantly reduce the CP signaling load between the AN and the CN. While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations or embodiments, such feature or aspect may be combined with one or more other features or aspects of the other implementations or embodiments as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms "coupled" and "connected", along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent

implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.