EP4133792A1

EP4133792A1 - Network nodes for improved client device mobility analytics in communication systems

Info

Publication number: EP4133792A1
Application number: EP20730008.8A
Authority: EP
Inventors: Andrey Krendzel; Ali HAMIDIAN; Siva VAKEESAR; Seil Jeon
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2023-02-15
Also published as: CN115699884A; WO2021239241A1

Abstract

The invention relates to a first and second network nodes for improved client device mobility analytics in a communication system. The first network node receives information about a set of geographical coordinates about a client device. Based on such information in the form of geographical coordinates the first network node can better accurately determine a target application server, AS, for the client device and transmits the information about the target AS to a second network node. Thereby, improved prediction of the client device mobility can be provided to the second network node. This means that the target AS can be prepared based on in-advance determination with better accuracy by the second network node to serve the client device before the client device connects to a new cell or gNB covered by the target AS, implying seamless service continuity and reduced latency in the communication system. Furthermore, the invention also relates to corresponding methods and a computer program.

Description

NETWORK NODES FOR IMPROVED CLIENT DEVICE MOBILITY ANALYTICS IN COMMUNICATION SYSTEMS

Technical Field

The invention relates to first and second network nodes for improved client device mobility analytics in communication systems. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

Multi-access Edge Computing (MEC) is acknowledged as one of the key enablers to meet the challenging Key Performance Indicators (KPIs) of applications, in particular being constrained with low latency. Since a User Equipment (UE) is highly mobile, supporting seamless MEC service continuity is of paramount importance. UE mobility might lead to the change of User Plane Function (UPF) with the change of gNodeB (gNB). In case the serving UPF is changed, the serving MEC host might be changed by a new MEC host closer to a UPF associated with a target gNB the UE connects to by a handoff event. In order to reliably meet the required KPIs of the client application in the MEC service continuity especially with the change of UPF, rapid setup of a target MEC application (i.e., application instantiation and data migration) based on determination of a target MEC host with accuracy is essentially required.

Following the current 3GPP service continuity procedure with changes of Radio Access Network (RAN), Uplink Classifier (ULCL), and UPF, as the concluded solution provided in 3GPP, the setup of the target MEC application is made after the target UPF is established by the Session Management Function (SMF). Therefore, meeting the performance requirement, in particular latency requirements, might be challenging. Time taken for MEC application instantiation and data migration in the MEC application mobility might be from tens to hundreds of seconds or more, depending on distance between source MEC host and target MEC host, and implementation of MEC service continuity solution. Therefore, in-advance setup of a target MEC application based on prediction concerning which cell or tracking area (TA) the UE might move into could be quite beneficial for seamless MEC service continuity. However, effectiveness of such in-advance preparation of a target MEC application on the selected MEC host is associated with prediction accuracy.

5G system architecture provides specifications to address the various continuity requirements of different applications and/or services for a UE, with different Session and Service Continuity (SSC) modes. With SSC mode 3, the network ensures that the UE suffers no loss of connectivity. A connection through a new PDU Session Anchor point is established before the previous connection is terminated to provide better service continuity. SSC mode 3 can be more appropriate to better serve the performance requirements for Cellular Vehicle-to- Everything (C-V2X) use cases among other SSC modes (i.e. SSC mode 1 and SSC mode 2) in following reasons: 1) the mobility of vehicular UE leads to UPF change frequently; 2) C-V2X service is sensitive to latency; 3) C-V2X needs the support of service/application relocation without breaking upper layer session and service continuity.

Summary

An objective of examples of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

Another objective of examples of the invention is to provide a solution with improved mobility prediction compared to conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous examples of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a first network node for a communication system, the first network node being configured to receive a first control message, wherein the first control message indicates a set of geographical coordinates for a client device; determine a target application server, AS, for the client device based on the first control message; and transmit a second control message to a second network node, wherein the second control message indicates the target AS.

A client application in the client device may be served by the target AS, e.g. as a MEC application. Generally, multiple MEC applications run on a MEC host. Therefore, to determine a target AS may mean to determine a target MEC host that hosts the MEC application.

The set of geographical coordinates may be considered as one or more three-dimensional reference formats to represent the spatial locations or points of the client device on Earth. For example, GPS or GLONASS or any other positioning system can be used.

An advantage of the first network node according to the first aspect is that improved prediction of the client device mobility is provided. Thereby, a target AS can be prepared by the second network node to serve the client device implying seamless service continuity and reduced latency in the communication system.

In an implementation form of a first network node according to the first aspect, the first control message further indicates a set of timestamps and a set of velocity information for the client device.

An advantage with this implementation form is that based on the timestamps, velocity information, and geographical coordinates of the client device the first network node can calculate the potential direction of the client device and predict future location(s) of the client device in terms of geographical coordinates. Thereby, the first network node can use the prediction information to make decision on a target AS.

In an implementation form of a first network node according to the first aspect, the first network node is configured to receive a third control message from a third network node, wherein third control message indicates a set of mobility restrictions for the client device; determine the target AS for the client device based on the first control message and the third control message.

An advantage with this implementation form is that a first network node can filter out cells matching the mobility restriction list before making a decision for a potential target AS associated to any of non-restricted cells. Thereby, the first network node does need to take restricted cells as candidate input to be considered when determining the target AS. This reduces complexity and time taken to determine a potential target AS that can serve the client device.

In an implementation form of a first network node according to the first aspect, the third network node is an access and mobility function, AMF.

An advantage with this implementation form is that an AMF maintains such client device specific mobility restriction list in terms of barred cells for a client device in question and transmits a third control message with this information to the first network node. Thereby, upon receiving a third control message from AMF the first network node can filter out restricted cells from candidate cells where a client device in question can freely move while being connected to the network. In an implementation form of a first network node according to the first aspect, the second control message further indicates an identity of the target AS and a time instance when the client device is expected to move into the target AS.

An advantage with this implementation form is that the second network node receives the second control message and can identify the target AS and by what time the target AS should be prepared to serve the client device in terms of MEC support. Thereby, the second network node can inform the target AS about this event.

In an implementation form of a first network node according to the first aspect, the first network node is a network data analytics function, NWDAF, and the second network node is an application function, AF, and the first network node is configured to receive the first control message from the AF or a location management function, LMF; and transmit the second control message to the AF.

An advantage with this implementation form is that the NWDAF may receive information about location of the client device from LMF or AF in the form of geographical coordinates and use this information in addition to already available cell identity (ID) and tracking area identity (TAI) information to produce better accurate mobility prediction of the client device and to properly identify the target AS. Thereby, the target AS information identified based on more fine-grained mobility prediction approach is transmitted in the second control message to the AF.

In an implementation form of a first network node according to the first aspect, the first network node is configured to at least one of receive the first control message directly from the AF or via a network exposure function, NEF; and transmit the second control message directly to the AF or via the NEF.

An advantage with this implementation form is that the first network node may receive the first control message and may transmit the second control message in cases if the AF is a trusted AF, i.e. operated by a network operator, or an untrusted AF, i.e. operated by a third-party, e.g. a service provider.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a second network node for a communication system, the second network node being configured to obtain a set of geographical coordinates for a client device; transmit a first control message to a first network node, wherein the first control message indicates the set of geographical coordinates for the client device; receive a second control message from the first network node in response to the transmission of the first control message, wherein the second control message indicates a target AS for the client device.

An advantage of the second network node according to the first aspect is that improved prediction of the client device mobility is provided. Thereby, the target AS can be prepared by the second network node to serve the client device implying seamless service continuity and reduced latency in the communication system.

In an implementation form of a second network node according to the second aspect, the second network node is configured to obtain a set of timestamps and a set of velocity information for the client device; and wherein the first control message further indicates the set of timestamps and the set of velocity information for the client device.

An advantage with this implementation form is that the second network node may obtain the timestamps, velocity information, and geographical coordinates of the client device and include the information to the first control message to be sent to the first network node. Thereby, the first network node may calculate the potential direction of the client device and predict future location(s) of the client device in terms of geographical coordinates.

In an implementation form of a second network node according to the second aspect, the second control message further indicates an identity of the target AS and a time instance when the client device is expected to move into the target AS.

An advantage with this implementation form is that the second network node receives the second control message and may obtain from the second control message the target AS and by what time the target AS should be prepared to serve the client device in terms of MEC support. Thereby, the second network node can inform the target AS about this event. In an implementation form of a second network node according to the second aspect, the first network node is a NWDAF and the second network node is an AF.

An advantage with this implementation form is that the NWDAF may receive information about location of client device from AF in the first control message in the form of geographical coordinates and use this information in addition to already available cell ID and TAI information to produce better accurate mobility prediction of the client device and to identify properly the target AS. Thereby, the target AS information identified based on more fine-grained mobility prediction approach is transmitted in the second control message to the AF.

In an implementation form of a second network node according to the second aspect, the second network node is configured to at least one of transmit the first control message directly to the NWDAF or via a NEF; and receive the second control message directly from the NWDAF or via the NEF.

An advantage with this implementation form is that the second network node may transmit the first control message and may receive the second control message directly to/from the NWDAF if the AF is trusted, or via a NEF if the AF is untrusted.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a first network node, the method comprises receiving a first control message, wherein the first control message indicates a set of geographical coordinates for a client device; determining a target application server, AS, for the client device based on the first control message; and transmitting a second control message to a second network node, wherein the second control message indicates the target AS.

The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the first network node according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the first network node.

The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the first network node according to the first aspect. According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a second network node, the method comprises obtaining a set of geographical coordinates for a client device; transmitting a first control message to a first network node, wherein the first control message indicates the set of geographical coordinates for the client device; receiving a second control message from the first network node in response to the transmission of the first control message, wherein the second control message indicates a target AS for the client device.

The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the second network node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the second network node.

The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the second network node according to the second aspect.

The invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to examples of the invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the examples of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different examples of the invention, in which:

- Fig. 1 shows a first network node according to an example of the invention;

- Fig. 2 shows a method for a first network node according to an example of the invention;

- Fig. 3 shows a second network node according to an example of the invention; - Fig. 4 shows a method for a second network node according to an example of the invention;

- Fig. 5 shows a signal diagram illustrating the interaction between a first network node and a second network node according to an example of the invention;

- Fig. 6 shows a further signal diagram illustrating the interaction between a first network node and a second network node and additionally a third network node according to an example of the invention;

- Fig. 7 illustrates movement of a client device in a communication system according to an example of the invention; and

- Fig. 8 shows a yet further signal diagram illustrating the interaction between a first network node, a second network node and an intermediate network node according to an example of the invention.

Detailed Description

Fig. 1 shows a first network node 100 according to an example of the invention. In the example shown in Fig. 1, the first network node 100 comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The first network node 100 is configured for communications in the communication system, e.g. via the transceiver 104 and a wired communication interface 110. That the first network node 100 is configured to perform certain actions can in this disclosure be understood to mean that the first network node 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.

According to examples of the invention the first network node 100 is configured to receive a first control message 510, see e.g. Fig. 5. The first control message 510 indicates a set of geographical coordinates for a client device 600 (a client device 600 is seen in Fig. 7). The first network node 100 is further configured to determine a target application server (AS) for the client device 600 based on the first control message 510. The first network node 100 is further configured to transmit a second control message 520 to a second network node 300. The second control message 520 indicates the target AS.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a first network node 100, such as the one shown in Fig. 1. The method 200 comprises receiving 202 a first control message 510. The first control message 510 indicates a set of geographical coordinates for a client device 600. The method 200 further comprises determining 204 a target AS for the client device 600 based on the first control message 510. The method 200 further comprises transmitting 206 a second control message 520 to a second network node 300. The second control message 520 indicates the target AS.

Fig. 3 shows a second network node 300 according to an example of the invention. In the example shown in Fig. 3, the second network node 300 comprises a processor 302, a transceiver 304 and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The second network node 300 is configured for communications in the communication system, e.g. via the transceiver 304 and a wired communication interface 310. That the second network node 300 is configured to perform certain actions can in this disclosure be understood to mean that the second network node 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.

According to examples of the invention the second network node 300 is configured to obtain a set of geographical coordinates for a client device 600. The second network node 300 is further configured transmit a first control message 510 to a first network node 100, see Fig. 5. The first control message 510 indicates the set of geographical coordinates for the client device 600. The second network node 300 is further configured receive a second control message 520 from the first network node 100 in response to the transmission of the first control message 510. The second control message 520 indicates a target AS for the client device 600.

Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a second network node 300, such as the one shown in Fig. 3. The method 400 comprises obtaining 402 a set of geographical coordinates for a client device 600. The method 400 further comprises transmitting 404 a first control message 510 to a first network node 100. The first control message 510 indicates the set of geographical coordinates for the client device 600. The method 400 further comprises receiving 406 a second control message 520 from the first network node 100 in response to the transmission of the first control message 510. The second control message 520 indicates a target AS for the client device 600.

Furthermore, for providing deeper understanding of examples of the invention different exemplary implementation cases will be described in the following disclosure with reference to Figs. 5 to 8. The described implementation cases are set in a 3GPP NR context and therefore the terminology, system design and protocols herein used. Hence, a client device can e.g. be understood as a UE and the terms will be used interchangeably. However, examples of the invention are not limited thereto. Fig. 5 shows a signal diagram illustrating the interaction between the first network node 100 and the second network node 300 in a communication system 500 according to an example of the invention. The communication system 500 may be any suitable communication system such as 3GPP LTE and NR.

In step I in Fig. 5, the second network node 300 obtains a set of geographical coordinates for a client device 600.

The second network node 300 can obtain the set of geographical coordinates for the client device 600 in many different ways. The second network node 300 may obtain geographical coordinates for the client device 600 by using external tools, e.g. GPS or GLONASS or any other positioning system. Thereby, if the accuracy of the geographical coordinates is appropriate the first network node 100 when receiving them may use them for prediction purposes without involvement of a Location Management Function (LMF) where geographical coordinates are obtained by means of the network which is more complex procedure. For example, in NR a LMF may interact with a UE in order to exchange location information applicable to UE assisted and UE based position methods or interacts with the RAN to obtain such location information. An AF may interact with the UE application to collect the geographical coordinates. Therefore, in examples of the invention, the first control message 510 can be received from a LMF or an AF depending in where and how the geographical coordinates for the UE is collected.

The second network node 300 further generates a first control message 510 indicating the obtained set of geographical coordinates for the client device 600.

In examples of the invention, the second network node 300 may also obtain a set of timestamps and a set of velocity information for the client device 600 for better accuracy of client device mobility prediction. Therefore, in these cases the first control message 510 further indicates the set of timestamps and the set of velocity information for the client device 600.

In 3GPP NR such input data about timestamps and velocity can be one or multiple and may be collected by a LMF or an AF, which exposes the location service to the authorized control plane NF to provide the UE location. Location indication of a UE in geographical coordinates may e.g. be expressed as a shape defined in 3GPP TS 23.032 or in a local coordinate system. The UE velocity may also be expresses based on 3GPP TS 23.032. The existing input data collected from the AF may include UE trajectory information. However, the UE’s position information may not be given in geographical coordinates which leads to the lack of prediction accuracy. As a non-limiting example, the input data given in italics in Table 1 in addition to existing input data may be collected from the AF. The proposed input data from the AF is UE geographical coordinates that can be one or multiple in addition to existing input data collected from the AF related to UE mobility, based on input data (e.g., UE ID, application ID, UE trajectory) provided for UE mobility analytics in 3GPP TS 23.288. Further, timestamp and UE velocity input data can be added as shown in Table 1.

Table 1: Proposed data added to existing service data to be collected from AF.

In step II in Fig. 5, the second network node 300 transmits the first control message 510 directly to the first network node 100 through a suitable communication interface, e.g., Nnwdaf which is an interface defined for 5GC NFs, to request subscription to network analytics delivery for a particular context, to cancel subscription to network analytics delivery and to request a specific report of network analytics for a particular context.

In step III in Fig. 5, the first network node 100 receives the first control message 510 and extracts the information content of the first control message 510, such as any of the set of geographical coordinates, and possibly the set of timestamps and the set of velocity information if such latter information analytics is comprised in the first control message 510.

In step IV in Fig. 5, the first network node 100 determines a target AS and its associated target cell to serve the client device 600 based on the information content of the first control message 510. In the following disclosure details of how the target AS may be determined will be given.

In examples of the invention, the first network node 100 also determines an identity of the target AS and a predicted time instance when the client device 600 is expected to move into the target cell where the target AS will be provided. For example, it may be assumed that the first network node 100 has mapping information between a target cell and AS location, which could be provided by a 3^rd party application provider, to provide the target AS based on a determined target cell. Such information sharing can e.g. be based on service agreement between the network operator and the service provider. Therefore, in examples the second control message 520 also indicates the identity of the target AS and the time instance when the client device 600 is expected to move into the target cell where the target AS will be provided.

In step V in Fig. 5, the first network node 100 transmits the second control message 520 to the second network node 300.

In step VI in Fig. 5, the second network node 300 receives the second control message 520 and extracts the information content of the second control message 520 so as to obtain information about the target AS determined by the first network node 300.

In step VII in Fig. 5, the second network node 300 will prepare the target AS to be ready to serve the client device 600.

For example, in NR on the receipt of the second control message 520, the target AS will be prepared to serve the client device 600 in terms of instantiation of a MEC application and migration of data associated to the client device 600 from the current serving MEC. Such preparation may e.g. be coordinated by the second network node 300 or other MEC orchestration control system. More in detail, ETSI MEC Industry Specification Group (ISG) also introduces MEC application mobility, which is a unique feature of the MEC system to be able to relocate a UE context and/or application instance from one MEC host to another MEC host to continue offering an optimized service experience for the UE. The MEC application mobility may consist of three main stages, i.e. : 1. Application service retention: the UE’s position change is detected by the 5G Core (5GC) and a forwarding tunnel is established. The uplink (UL) messages of the UE are forwarded between Source UPF (S-UPF) and Target UPF (T-UPF). The UE’s uplink message will be forwarded to a source MEC (S-MEC);

2. Application instantiation/data migration: the MEO chooses target MEC (T-MEC) for the UE and triggers MEC application instantiation, and applies data migration from S-MEC to T-MEC; and

3. Application service redirection: when the application instantiation and data migration are finished, the MEO generates routing rules for a new MEC application initiated on T-MEC. The 5GC updates corresponding UPF routing rules. UE’s uplink message will be forwarded to target MEC application via T-UPF.

Service continuity procedures based on SSC mode 3 with changes of RAN, ULCL, and UPF, are specified in 3GPP TR 23.725. For application mobility where application servers are deployed in a distributed manner, e.g., distributed MEC hosts, the AF, i.e., MEC Orchestrator or MEC Platform Manager might need to prepare a new application (e.g., new MEC application) on a new application server by the changes of connected RAN and UPF. However, after the SMF establishes target UPF, the AF is notified. Considering the application mobility procedure might be time-consuming from tens to hundreds of seconds, depending on distance between source application server and target application server, and implementation of distributed application service platform, the current service continuity solution might be challenging to meet the low latency requirement for seamless service continuity. With the proposed solution, a MEC Orchestrator (MEO) or a MEC Platform Manager (MEPM) as an AF may initiate a target MEC application instantiation and data migration in advance for seamless MEC service continuity.

It is further noted from Fig. 5 that the first network node 100 interacts with a single second network node 300 both for reception of the first control message 510 and transmission of the second control message 520. However, in some cases the first network node 100 receives a first control message 510 from one second network node and transmits the second control message 520 to another second network node. Therefore, in examples of the invention, the first network node 100 e.g. acting as a Network Data Analytics Function (NWDAF) may receive the first control message 510 from an AF or a LMF as previously explained, and transmit the second control message 520 to the second network node 300 acting as an AF. Certainly, other examples and combinations are possible within the scope of the invention. Fig. 6 shows a further signal diagram according to an example of the invention in which a third network node 700 is interacting with the first network node 100. Steps I - VII in Fig. 6 fully corresponds to steps I - VII in Fig. 5. In addition to the mentioned steps I - VII an additional step VIII is performed in Fig. 6.

In examples of the invention, the third network node 700 is an AMF which transmits a third control message 530 to the first network node 100 which based on the third control message 530 can filter out restricted cells from candidate cells of potential movement of the client device 600. The third control message 530 therefore indicates a set of mobility restrictions for the client device 600 in step VIII in Fig. 8. Upon reception of the third control message 530, the first network node 100 may also use the information content of the third control message 530 for determining the target AS and its associated target cell for the client device 600.

A Mobility Restrictions List (MRL) in NR is generally held by the Unified Data Management (UDM) but is retrieved to the AMF for actual enforcement on UE and RAN to follow mobility restriction rules. In a non-limiting example new proposed input data (i.e., UE geographical coordinates and mobility restriction list) to be collected from the LMF and the AMF are given in italics in Table 2 below in addition to the existing input data (i.e., UE ID, UE locations, Type Allocation Code (TAC), Frequent Mobility Registration Update) collected from AMF, provided for UE mobility analytics in TS 23.288. Hence, a MRL is added in addition to the previous mentioned UE coordinates and possibly timestamp and UE velocity information. As shown in Table 2 the MRL may indicate roaming and/or access restrictions list that prevents subsequent mobility action of a target UE for which the NR-RAN provides information about the target of the mobility action towards the UE, e.g., due to RAT restriction, Forbidden Area, Service Area Restriction, Non-Allowed Area, etc.

Table 2: Proposed data added to UE mobility input data collected from 5GC.

3GPP has introduced a Network Function (NF) called NWDAF as previously mentioned, which collects and processes data from other NFs and provides output analytics information to requested NFs or AFs. The UE mobility analytics is one of the Network Data Analytics that can be provided by NWDAF, specified in 3GPP. The UE mobility analytics might be used for the AF to initiate MEC application instantiation and data migration before the UE moves into a target RAN covered by other MEC service area. The UE mobility analytics is based on input data, i.e. , TAs or cells that the UE entered from AMF, so the output information for UE mobility prediction would be potential TA or cells that the UE might move into on the requested analytics target period.

For UE mobility analytics, the NWDAF provides prediction output to the AF about which cell or TAs the UE might move into based on collected input data from 5GC and service data from AF related to UE mobility. The collected input data for the UE location is tracking areas or cells that the UE has entered from AMF and geographical area that the UE has entered from AF. Such granularity of collected input data for the UE location could be challenging to accurately predict which cell the UE might move into at what time instance, since there is no collected data about UE’s movement behavior happened within a cell. This affects the AF’s decision on the selection of a target AS and time to instantiate a target application for seamless application service continuity in the communication system 500. By adding geographical coordinates to UE mobility analytics according to examples of the invention UE mobility prediction can be improved.

Fig. 7 illustrates the movement of a UE 600 in a communication system 500. Suppose that there are four different cells, i.e. CelH, Cell2, Cell3, Cell4, belonging to different base stations gNB1, gNB2, gNB3, gNB4 with their associated RANs, i.e. RAN1 , RAN2, RAN3, RAN4. Further, each RAN is served by a nearby MEC, i.e. MEC1 , MEC2, MEC3, MEC4. The UE 600 roams in CelH along the dashed trajectory as shown in Fig. 7. When the UE 600 moves along the trajectory, an AMF has no idea how long the UE 600 would stay in CelH and what happens about UE mobility behavior within CelH, e.g., delayed moving due to traffic congestion, stopped on demand to eat or do shopping, the right road exit missed to turn and returns back, etc. That is, because the AMF is only capable of tracking a UE on cell level but not in geographical coordinate level.

Therefore, the first network node 100 acting as a NWDAF might predict that the UE 600 would move into cell Cell2 or cell Cell3 or stay in CelH , based on cell-level input data collected from the AMF. As a result, MEC2 and/or MEC3 might be prepared for a target MEC application. In case the UE 600 moves out of CelH (e.g., due to a plan change) and instead moves into Cell4, as shown in Fig. 7, MEC4 has not been prepared to serve the client application which means that MEC service continuity might be interrupted.

As aforementioned, the first network node 100 may determine the target AS in a number of different ways. In a non-limiting example and with reference to the scenario shown in Fig. 7 one exemplary method of determining the target AS is as follows:

• All possible candidate cells, e.g. all neighboring cells, are identified from the current location of the UE 600. Hence, cells, i.e. Cell2, Cell3, Cell4 are candidate cells in Fig. 7.

• The set of geographical coordinates for the UE 600 are investigated and potential direction(s) is computed or drawn by taking into consideration the moving direction of the UE 600 based on the set of geographical coordinates and the set of velocity information and the set of time stamps. • Cells matching in the MRL are filtered out so that the number of candidate cells is reduced. For example, if Cell2 is on the restriction list only cells Cell3 and Cell4 are among the remaining candidate cells.

• In Fig. 7 the first network node 100 may predict the dashed trajectory, providing output information that the UE 600 will move into Cell4 at what time instance.

• The target AS is finally determined from or based on the remaining candidate cells.

Fig. 8 shows a yet further signaling diagram according to an example of the invention when the first network node 100 act as a NWDAF and the second network node 300 act as an AF. In such scenarios, there are generally two main cases how the signaling between the NWDAF and the AF may be performed.

In cases the AF is a so-called trusted AF no intermediate network node is needed in the communication between the first network node 100 and the second network node 300, e.g. as in the example illustrated in Fig. 5. The trusted AF can also be denoted as an internal AF which is operated by a network operator. In examples of the invention, the second control message 520 may also indicate a target cell identity (ID) if the AF is a trusted AF. Existing output information with cell ID and TAI can be sent to the AF. In this case, it may be assumed that an internal AF has mapping information or is able to access the mapping information between the cell coverage of the network operator and service coverage of deployed MEC hosts, e.g. based on information sharing agreements and methods between the network operator and the service provider.

However, in other cases the AF is considered as a so-called untrusted AF which implies that an intermediate network node is needed in the communication between the first network node 100 and the second network node 300. The untrusted AF may e.g. be an external AF such as a third-party AF not operated by the network operator itself. This latter case is illustrated in Fig. 8 where a NEF 900 is acting as the intermediate network node between the NWDAF and the AF.

Generally, in case the AF is not internal but a third-party external AF and therefore considered as untrusted, network operator-internal information like cell ID and TAI might be restricted to be exposed to third-party AF. In a proposed example, it is basically assumed that the network, e.g. the NWDAF, knows the mapping information between the cell coverage of the network operator and service coverage of a deployed application servers, e.g. MEC hosts, of the service provider. Such information sharing can be based on service agreement between the network operator and the service provider. For the external AF, network operator-internal cell ID information might be substituted e.g. by area level information or taken out based on the local policy for outbound information exposure. Regardless of an option selected by the network operator, to provide information about predicted target AS to the external AF, the new output information given in italics in Table 3 below may be proposed in addition to the existing output information (i.e., UE group ID or UE ID, Time slot entry including duration and UE location) for UE mobility prediction according to current solutions in 3GPP TS 23.288. That is, identifier of the target AS and expected time when the UE may move into the target AS.

Table 3: Proposed information to be added to existing output information.

For the UE location information in Table 3, it may be substituted by geographical area information (in italics) which can be area/region block distinguished based on local map policy. It might be taken out based on the local policy of the network operator for outbound information exposure. The target AS information may include target AS identifier and timestamp when the UE might move into the target AS. The target AS identifier may be based on a translation of the predicted cell ID where the UE might move into. It is further noted that requesting to receive target AS information included in the output information may not be limited to an external AF and may therefore also be requested by an internal AF.

With reference to Fig. 8 two different main procedures given in NR for implementing examples of the invention will be described, i.e. a procedure for analytics subscribe/unsubscribe by a AF via a NEF, and a procedure for analytics request by a AF via a NEF.

Procedure for analytics subscribe/unsubscribe

With reference to Fig. 8 an example of invention related to analytics subscribe/unsubscribe procedure is firstly described. In order to have output information including target AS information to be associated with a potential cell where the UE might move into the UE mobility analytics service, an AF needs to specify such demand in the NWDAF analytics subscription message specified in 3GPP TS 23.288.

Tables 4 and 5 below show inputs and output information with example values in order to show how the proposed UE mobility analytics can be provided to the AF. For the request of target AS Identifier, Analytics Reporting Content field may be added as an optional input information. All the inputs and outputs information may be based on the subscription message format specified in 3GPP TS 23.288 for Nnwdaf_AnalyticsSubscription_Subscribe and in TS 23.502 for Nnef_AnalyticsExposure_Subscribe.

In step I in Fig. 8, the NEF 900 controls analytics mapping based on inbound restrictions and outbound restrictions on an AF ID with allowed Analytics ID. So, through the analytics mapping, UE location information expressed in operator-specific internal information, i.e. TAs or cells, can be converted into publicly-recognized information, such as geographical area or taken out.

In step II in Fig. 8, the AF 300 transmits a Nef_AnalyticsExposure_Subscribe message 512 to the NEF 900. The Nef_AnalyticsExposure_Subscribe message 512 comprises the information content in the first control message 510 and may have the format as given in Table 4. The information element, i.e. Analytics Reporting Content = “AS” given in italics may be added in Nnef_AnalyticsExposure_Subscribe request message with the existing information.

Table 4: Contents for Analytics Exposure Subscription message sent by AF to NEF.

In step III in Fig. 8, the NEF 900 receives the previously described Nef_AnalyticsExposure_Subscribe message 512 from the AF 300.

In step IV in Fig. 8, the NEF 900 transmits a Nnwdaf_AnalyticsSubscription_Subscribe message 514 to a NWDAF 100. The Nnwdaf_AnalyticsSubscription_Subscribe message 514 comprises the information content of the first control message 510.

In order to subscribe to UE mobility analytics service including target AS Identifier associated with a potential cell where the UE might move into in the notified contents, the Nnwdaf_Analytics Subscription_Subscribe message 514 includes Analytics Report Content field. The NEF 900 is required to manage the added input information between Nnef_AnalyticsExposure_Subscribe message and Nnwdaf_AnalyticsSubscription_Subscribe message. The information element, i.e. Analytics Reporting Content = ''AS”given in italics may be added in Nnef_AnalyticsSubscription_Subscribe message with the existing information.

Table 5: Contents for Analytics Subscription message sent by NEF to NWDAF.

In step V in Fig. 8, the NWDAF 100 receives the previously described

Nnwdaf_AnalyticsSubscription_Subscribe message 514 from the NEF 900. Thereafter, the NWDAF 100 determines a target AS based on the received Nnwdaf_AnalyticsSubscription_Subscribe message 514 from the NEF 900.

In step VI in Fig. 8, the NWDAF 100 responds with a Nnwdaf_AnalyticsSubscription_Notify message 522 to the NEF 900. The Nnwdaf_AnalyticsSubscription_Notify message 522 hence comprises the information content of the second control message 520.

In step VII in Fig. 8, the NEF 900 receives the Nnwdaf_AnalyticsSubscription_Notify message 522 from the NWDAF 100. In step VIII in Fig. 8, the NEF 900 transmits a Nnef_AnalyticsExposure_Notify message 524 to the AF 300. The Nnef_AnalyticsExposure_Notify message 524 comprises the information content of the second control message 520 embedded in the Nnwdaf_AnalyticsSubscription_Notify message 522 from the NWDAF 100.

In step IX in Fig. 8, the AF 300 receives the Nnef_AnalyticsExposure_Notify message 524 from the NEF 900. The Nnef_AnalyticsExposure_Notify message 524 comprises the information content of the second control message 520 and hence information about the target AS. Therefore, the AF 300 can initiate the preparation of the target AS to serve the UE 600 which has been described previously.

For subscription of the analytics service, it follows the generic procedure to unsubscribe analytics services provided in 3GPP TS 23.288 and TS 23.502; Nef_AnalyticsExposure_Unsubscribe is sent to the NEF 900 from the AF 300 with Subscription Correlation ID added as required input in the unsubscribe message. Then, Nnwdaf_AnalyticsSubscription_Unsubscribe is sent to the NWDAF 100 from the NEF 900 with Subscription Correlation ID added as required input in the unsubscribe message. The NWDAF 100 cancels the subscription for the analytics I D. More details can be found in 3GPP TS 23.288 and TS 23.502.

Procedure for analytics request With reference to Fig. 8 the example of invention related to analytics request procedure is now described. Fig. 8 shows how the AF can request to receive the proposed output information for the enhanced UE mobility analytics, with Analytics Information request, specified in 3GPP TS 23.288.

In step I in Fig. 8, the NEF 900 controls analytics mapping as previously explained.

In step II in Fig. 8, the AF 300 transmits a Nef_AnalyticsExposure_Fetch message 512 to the NEF. The Nef_AnalyticsExposure_Fetch message 512 comprises the information content of the first control message 510. Table 6 below shows additional information elements that may be added, i.e. Requested Target Contents = “AS" and Analytics Target ID = “Target AS Identifier" in the Nnef_AnalyticsExposure_Fetch message.

Table 6: Contents for Analytics Exposure Fetch message sent by AF to NEF.

In step III in Fig. 8, the NEF 900 receives the Nef_AnalyticsExposure_Fetch message 512 from the AF 300.

In step IV in Fig. 8, the NEF 900 transmits a Nnwdaf_Analyticslnfo_Request message 514 to the NWDAF 100. The Nnwdaf_Analyticslnfo_Request message 514 comprises the information content of the first control message 510.

In order to request target AS Identifier associated with a potential cell where the UE might move into in the notified contents, the Nnwdaf_Analyticslnfo_Request message 514 includes Analytics Report Content field. The NEF 900 is required to manage the added input between Nnef_Analytics Exposure_Fetch message and Nnwdaf_Analyticslnfo_Request message. Therefore, additional information elements, i.e. Analytics Reporting Content = “AS" and Analytics Target ID = “Target AS Identifier”, may be added in the existing Nnwdaf_Analyticslnfo_Request message 514.

Table 7: Contents for Analytics Information Request message sent by NEF to

NWDAF.

In step V in Fig. 8, the NWDAF 100 receives the Nnwdaf_Analyticslnfo_Request message 514 from the NEF 900. Thereupon the NWDAF 100 determines a target AS.

In step VI in Fig. 8, the NWDAF 100 responds with a Nnwdaf_Analyticslnfo_Request response message 522 to the NEF 900, and the Nnwdaf_Analyticslnfo_Request response message 522 comprises the information content of the second control message 520. In step VII in Fig. 8, the NEF 900 receives the Nnwdaf_Analyticslnfo_Request response message 522 from the NWDAF 100.

In step VIII in Fig. 8, the NEF 900 transmits a Nnef_AnalyticsExposure_Fetch message 524 to the AF 300. The Nnef_AnalyticsExposure_Fetch message 524 comprises information content of the second control message 520, hence information about the target AS determined by the NWDAF 100.

In step IX in Fig. 8, the AF 300 receives the Nnef_AnalyticsExposure_Fetch message 524 from the NEF 900. Therefore, the AF 300 can prepare the target AS to serve the UE 600.

Furthermore, any method according to examples of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized that examples of the first network node 100 and the second network node 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.

Especially, the processor(s) of the first network node 100 and the second network node 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

The client device 600 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer- comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver ora server. The UE can be a Station (STA), which is any device that contains an IEEE 802.11 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WMAX and its evolution, and in fifth generation wireless technologies, such as New Radio.

Finally, it should be understood that the invention is not limited to the examples described above, but also relates to and incorporates all examples within the scope of the appended independent claims.

Claims

1. A first network node (100) for a communication system (500), the first network node (100) being configured to receive a first control message (510), wherein the first control message (510) indicates a set of geographical coordinates for a client device (600); determine a target application server, AS, for the client device (600) based on the first control message (510); and transmit a second control message (520) to a second network node (300), wherein the second control message (520) indicates the target AS.

2. The first network node (100) according to claim 1, wherein the first control message (510) further indicates a set of timestamps and a set of velocity information for the client device (600).

3. The first network node (100) according to claim 1 or 2, configured to receive a third control message (530) from a third network node (700), wherein third control message (530) indicates a set of mobility restrictions for the client device (600); determine the target AS for the client device (600) based on the first control message (510) and the third control message (530).

4. The first network node (100) according to claim 3, wherein the third network node (700) is an access and mobility function, AMF.

5. The first network node (100) according to any one of the proceeding claims, wherein the second control message (520) further indicates an identity of the target AS and a time instance when the client device (600) is expected to move into the target AS.

6. The first network node (100) according to any one of the proceeding claims, wherein the first network node (100) is a network data analytics function, NWDAF, and the second network node (300) is an application function, AF, and configured to receive the first control message (510) from the AF or a location management function, LMF; and transmit the second control message (520) to the AF.

7. The first network node (100) according to claim 6, configured to at least one of receive the first control message (510) directly from the AF or via a network exposure function, NEF; and transmit the second control message (520) directly to the AF or via the NEF.

8. A second network node (300) for a communication system (500), the second network node (300) being configured to obtain a set of geographical coordinates for a client device (600); transmit a first control message (510) to a first network node (100), wherein the first control message (510) indicates the set of geographical coordinates for the client device (600); receive a second control message (520) from the first network node (100) in response to the transmission of the first control message (510), wherein the second control message (520) indicates a target AS for the client device (600).

9. The second network node (300) according to claim 8, configured to obtain a set of timestamps and a set of velocity information for the client device (600); and wherein the first control message (510) further indicates the set of timestamps and the set of velocity information for the client device (600).

10. The second network node (300) according to any one of claims 8 or 9, wherein the second control message (520) further indicates an identity of the target AS and a time instance when the client device (600) is expected to move into the target AS.

11. The second network node (300) according to any one of claims 7 to 10, wherein the first network node (100) is a NWDAF and the second network node (300) is an AF.

12. The second network node (300) according to claim 11 , configured to at least one of transmit the first control message (510) directly to the NWDAF or via a NEF; and receive the second control message (520) directly from the NWDAF or via the NEF.

13. A method (200) for a first network node (100), the method (200) comprising: receiving (202) a first control message (510), wherein the first control message (510) indicates a set of geographical coordinates for a client device (600); determining (204) a target application server, AS, for the client device (600) based on the first control message (510); and transmitting (206) a second control message (520) to a second network node (300), wherein the second control message (520) indicates the target AS.

14. A method (400) for a second network node (300), the method (400) comprising: obtaining (402) a set of geographical coordinates for a client device (600); transmitting (404) a first control message (510) to a first network node (100), wherein the first control message (510) indicates the set of geographical coordinates for the client device (600); receiving (406) a second control message (520) from the first network node (100) in response to the transmission of the first control message (510), wherein the second control message (520) indicates a target AS for the client device (600).

15. A computer program with a program code for performing a method according to claim 13 or 14 when the computer program runs on a computer.