Network node, communication system, and communication method

Abstract

The present invention is a network node provided with a control unit that compares the service conditions of a second server with the service conditions of a third server after a server providing services to a terminal has been changed from a first server to the second server, and a transmission unit that transmits information of the third server to the terminal if the service conditions of the third server are superior to the service conditions of the second server.

Description

Network node, communication system, and communication method

[0001] The present invention relates to a network node, a communication system, and a communication method.

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) has introduced a wireless communication system called 5G or NR (New Radio) (hereinafter, the wireless communication system will be referred to as "5G" or "NR") in order to achieve a larger system capacity, a higher data transmission speed, and a lower latency in wireless sections. 5G introduces various wireless technologies to meet the requirement of achieving a throughput of 10 Gbps or more while reducing latency in wireless sections to 1 ms or less. Furthermore, 6G, a future communication system, is also being studied.

[0003] Edge computing, which provides operator and third-party services at locations close to the access point of a UE (terminal), reduces end-to-end latency and reduces the load on the transport network, enabling efficient services, is also being considered. For example, for applications requiring low latency, a system has been proposed in which edge computing functional units are configured in terminals and servers, and communication is enabled using a server located close to the terminal (e.g., Non-Patent Document 1).

[0004] To support service continuity, a procedure has been introduced to transfer application client information from a source server (specifically, an EAS, which will be described later) to a target server when a terminal moves, etc. This procedure is called ACR (Application Context Relocation).

[0005] 3GPP TS 23.558 V18.5.0 (2023-12)

[0006] If the terminal is using a service that requires service continuity, an already instantiated server (a server that has already been started) is selected as the target server and ACR is performed.

[0007] On the other hand, among the one or more uninstantiated servers, there may be a server with better service conditions than the instantiated server. However, in the conventional technology, even if there is a server with better service conditions than the service conditions of the already instantiated server, it is not possible to select that server as the target server and execute ACR. In other words, in the conventional technology, there is a possibility that an appropriate server will not be selected as the target server in ACR.

[0008] The present invention has been made in view of the above points, and has an object to provide a technique for selecting an appropriate server as a target server in an ACR.

[0009] According to the disclosed technology, a network node is provided that includes: a control unit that, after a server that provides a service to a terminal is changed from a first server to a second server, compares the service conditions of the second server with the service conditions of a third server; and a transmission unit that, when the service conditions of the third server are better than the service conditions of the second server, transmits information of the third server to the terminal.

[0010] According to the disclosed technology, a technology is provided for selecting an appropriate server as a target server in an ACR.

[0011] 8.5.3.3-1。 EAS Service KPIs (Table 8.2.5-1)。 EAS Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)。 EAS Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)。 EAS Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)。 AC Service KPIs (Table 8.2.5-1)。 AC Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)。 AC Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)。 AC Discovery Response (Table 8.5.3.3-1)。 AC Service KPIs (Table 8.2.5-1)

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0013] In the operation of the wireless communication system according to the embodiment of the present invention, existing technologies are used as appropriate. However, the existing technologies include, but are not limited to, the existing LTE or the existing NR.

[0014] Furthermore, in the embodiments of the present invention, "configuring" radio parameters and the like may mean that predetermined values ​​are pre-configured, or that radio parameters notified from the network node or the terminal 20 are set. Hereinafter, first, an example of the configuration of a core network that is also used in communication in edge computing will be described, and then the configuration and operation related to edge computing will be described.

[0015] Fig. 1 is a diagram illustrating an example of a communication system corresponding to a core network. As shown in Fig. 1, this communication system is composed of a UE (terminal 20) and multiple network nodes. Hereinafter, it is assumed that one network node corresponds to each function, but multiple functions may be realized by one network node, or multiple network nodes may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0016] The RAN (Radio Access Network) is a network node having a radio access function, which may include a base station 10, and is connected to a UE, an AMF (Access and Mobility Management Function), and a UPF (User plane function). The AMF is a network node having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), registration management, connection management, reachability management, and mobility management. The UPF is a network node having functions such as a PDU (Protocol Data Unit) session point to the outside that interconnects with the DN (Data Network), packet routing and forwarding, and user plane QoS (Quality of Service) handling. The UPF and the DN constitute a network slice.

[0017] The AMF is connected to the UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0018] The SMF is a network node that has functions such as session management, UE IP (Internet Protocol) address allocation and management, DHCP (Dynamic Host Configuration Protocol) function, ARP (Address Resolution Protocol) proxy, and roaming function. The NEF is a network node that has the function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node that has functions such as selecting a network slice to which a UE connects, determining the allowed NSSAI (Network Slice Selection Assistance Information), determining the NSSAI to be configured, and determining the AMF set to which the UE connects. The PCF is a network node that has the function of controlling network policies. The AF is a network node that has the function of controlling application servers. The NRF is a network node that has the function of discovering NF instances that provide services. The UDM is a network node that manages subscriber data and authentication data. The UDM is connected to a UDR (User Data Repository) that stores the data.

[0019] 2 is a diagram for explaining an example of a communication system in a roaming environment. As shown in Fig. 2, the network is made up of a UE, which is a terminal 20, and a plurality of network nodes.

[0020] The SEPP is a non-transparent proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). The vSEPP shown in Figure 2 is a SEPP in a visited network, and the hSEPP is a SEPP in a home network.

[0021] As shown in Figure 2, a UE is in a roaming environment connected to a RAN and an AMF in a Visited PLMN (VPLMN). The VPLMN and a Home PLMN (HPLMN) are connected via a vSEPP and an hSEPP. The UE can communicate with a UDM in the HPLMN via the AMF in the VPLMN, for example.

[0022] (Edge Computing) An overview of edge computing related to the technology according to the present embodiment will be described. As described above, edge computing is being considered, which enables efficient services by providing operator and third-party services at locations close to the access point of a UE, thereby reducing end-to-end delays and reducing the load on a transport network.

[0023] For example, for applications that require low latency, an operation is being considered in which a functional unit for edge computing is configured in the terminal and server, and communication is enabled using a server located close to the terminal (for example, Non-Patent Document 1).

[0024] FIG. 3 is a diagram illustrating an example of edge computing. FIG. 3 is also a configuration diagram of a communication system according to this embodiment. As shown in FIG. 3, application communication is performed between an edge application server 40 (EAS) that provides an application service (which may also be called a service) to a terminal 20 and an application client 22 (AC) in the terminal 20 (which may also be called a UE 20). An edge enabler server 30 (EES) and an edge enabler client 21 (EEC) in the terminal 20 perform operations for connecting to an edge data network (EDN). The EAS may also be called a "server."

[0025] 3, the UE 20 is connected to an edge data network and an edge configuration server (ECS) 50 via a core network. The ECS 50 is a server that provides support functions necessary for the EEC 21 to connect to the EES 30. Specifically, the ECS 50 provides EDN configuration information to the UE 20.

[0026] The EAS 40, the EES 30, and the ECS 50 are all examples of network nodes. The EAS 40, the EES 30, and the ECS 50 may be implemented as a physical device (computer), a container, a POD, or other methods. In this embodiment, starting up the EAS 40 is referred to as "instantiation." For example, instantiation of the EAS 40 may be starting up a container corresponding to the EAS 40.

[0027] The reference point EDGE-n in the architecture enabling edge applications shown in FIG. 3 is as follows (see Non-Patent Document 1):

[0028] EDGE-1: Enables interoperability between the EES 30 and the EEC 21. Registers and deregisters the EEC 21 to the EES 30. Also searches and acquires configuration information for the EAS 40. Also discovers available EASs 40 in the EDN. Executes service continuity procedures, such as initiating ACR (Application Context Relocation).

[0029] EDGE-2: Enables interoperability between the EES 30 and APIs to retrieve core network functions and network capability information. Supports access via the Service Capability Exposure Function (SCEF) and NEF APIs, or direct access to core network functions from the EES 30 located within the Mobile Network Operator (MNO) trust domain.

[0030] EDGE-3: Enables interoperability between the EES 30 and the EAS 40. Supports registration of the EAS 40 with availability information, such as time constraints and location constraints. Also, deregisters the EAS 40 from the EES 30. Also, discovers the target EAS 40 to support Application Context Transfer (ACT). Also, provides access to network capability information, such as location information. Also, requests the establishment of a data session between the AC 22 and the EAS 40, to which a specific QoS applies, and obtains QoS information. Also, supports service continuity procedures, such as ACR status.

[0031] EDGE-4: Enables interoperability between the ECS 50 and the EEC 21. Provides edge configuration information to the EEC 21.

[0032] EDGE-5: Allows interoperability between the AC 22 and the EEC 21.

[0033] EDGE-6: Enables interoperability between the ECS 50 and the EES 30. Registers EES information to the ECS 50. Also, deregisters EES information from the ECS 50. Also, retrieves target EES information from the ECS 50.

[0034] EDGE-7: Enables interoperability between EAS 40 and APIs to retrieve core network functions and network capability information. Access via SCEF and NEF APIs or direct access to core network functions from EAS 40 located within the MNO trust domain is supported.

[0035] EDGE-8: Enables interoperability between the ECS 50 and APIs to retrieve core network functions and network capability information. Access via SCEF and NEF APIs or direct access to core network functions from the ECS 50 located within the MNO trust domain is supported.

[0036] EDGE-9 enables interoperability between EESs 30. Two EESs 30 connected by EDGE-9 may be included in different EDNs or the same EDN. To support ACR, it discovers target EAS information. It also supports EEC context relocation procedures. It also transparently transfers application context in ACR managed by the EEL (Edge Enabler layer).

[0037] (About ACR) Non-Patent Document 1 defines a procedure called ACR (Application Context Relocation) as a procedure for supporting service continuity. In ACR, when the terminal 20 moves, for example, information about an application client is transferred from a source EAS to which the terminal 20 is connected before the move to a target EAS to which the terminal 20 is connected after the move.

[0038] When performing an ACR, in addition to using an instantiated EAS as the target EAS, it is also possible to select an instantiable (non-instantiated) EAS and perform the ACR after instantiation.

[0039] On the other hand, instantiation may increase the time required for ACR, so the terminal 20 should connect to an already instantiated EAS while using a service that requires continuity.

[0040] Therefore, a technology has been proposed that sets up a new parameter to determine the need for service continuity at the service provisioning or EAS detection stage, and based on that service continuity, determines whether to instantiate and connect to an EAS or to connect to an EAS that has already been instantiated.

[0041] The technology according to this embodiment will be described below. First, the problem will be described, and then the technology for solving the problem will be described.

[0042] Although the example described below is an example in which the present invention is applied to edge computing, the present invention can also be applied to fields other than edge computing. For example, the present invention can also be applied to network nodes not limited to EES or EAS.

[0043] (Problems) In the above-described conventional technology, since it takes time to instantiate a new EAS, an already instantiated EAS is selected for a terminal 20 using a service that requires service continuity, and ACR is executed. The EAS discovery procedure in this example will be described with reference to FIG. 4.

[0044] In S1, the EEC 21 transmits an EAS discovery request to the EES 30. This EAS discovery request is assumed to be a request for a service that requires service continuity.

[0045] In S2, the EES 30 performs an authorization check to select an already instantiated EAS, and in S3, the EES 30 returns a response (EAS discovery response) to the EEC 21 that includes information about the EAS.

[0046] As described above, in the conventional technology, when service continuity is required, an EAS that has already been instantiated is selected as the target EAS. However, among one or more EASs that have not yet been instantiated and can be instantiated, there may be an EAS that better satisfies the service discovery conditions, service KPIs (Key Performance Indicators), etc. In other words, in the conventional technology, there is a possibility that a more appropriate EAS that takes into account the connection environment after ACR is not selected as the target EAS.

[0047] (Outline of the embodiment) In order to solve the above problem, in this embodiment, it is possible to select a target EAS to be the ACR destination, including instantiable EASs as candidates, on the premise that the impact of instantiation on the EAS_ACR service is reduced.

[0048] Specifically, after EAS_ACR is executed for the instantiated EAS, or in parallel with the execution of EAS_ACR, if EES 30 detects an instantiable EAS in the EAS discovery procedure that is expected to satisfy the service discovery conditions and service KPIs, it instantiates the EAS.

[0049] The EES 30 checks the service conditions (e.g., KPI, service authorization level, AC locations that the EAS can support, etc.) of the newly instantiated EAS and the EAS connected to the terminal 20 by the EAS_ACR. If it is determined that the service conditions of the newly instantiated EAS are better, the ACR to the newly instantiated EAS is executed, and the terminal 20 connects to the newly instantiated EAS.

[0050] (Processing Procedure) An example of the processing procedure in this embodiment will be described with reference to Fig. 5. Note that the basic processing content in S101 to S104 is an existing technology and is disclosed in, for example, Non-Patent Document 1, so only an outline of S101 to S104 is described.

[0051] For example, when the EEC 21 determines that an ACR (application context transfer) is necessary due to the movement of the EEC 21 (terminal 20), the EEC 21 starts the EAS discovery procedure.

[0052] <S101: EAS discovery request> In S101, the EEC 21 transmits an EAS discovery request to the EES 30.

[0053] The EAS discovery request includes an identifier of the requester (EEC 21). The EAS discovery request may also include an EAS discovery filter, information on service continuity support of the EEC 21, and location information of the terminal 20. Figure 6 shows examples of information elements included in the EAS discovery request. Figure 7 shows examples of information elements in the EAS discovery filter included in the EAS discovery request.

[0054] In this embodiment, it is assumed that the EAS discovery request in S101 is a request for a service that requires service continuity (i.e., EAS), but the present invention is not limited to this assumption.

[0055] <S102: Authorization Check> When the EES 30 receives the EAS discovery request from the EEC 21, it performs an authorization check.

[0056] During the authorization check, the EES 30 may, for example, find one or more EASs that match an EAS discovery filter, which may include only instantiated EASs, only instantiable non-instantiated EASs, or both instantiated and instantiable non-instantiated EASs.

[0057] The EES 30 can detect instantiated EASs based on, for example, registration information received from the instantiated EASs, and the EES 30 can detect instantiable, non-instantiated EASs based on, for example, configuration information received from the ECS 50.

[0058] In addition, in S102, the EES 30 can check whether the EAS(s) satisfy the Expected AC service KPIs or the Minimum required AC Service KPIs by collecting edge load analysis information from an ADAES (Application Data Analytics Enabler Server) or by collecting performance data from an OAM.

[0059] 8 shows an example of AC Service KPIs (information indicating service characteristics required by an AC). Information such as AC Service KPIs, Expected AC service KPIs, and Minimum required AC Service KPIs may be included in an EAS discovery request or in registration information transmitted from the EEC 21 to the EES 30 when the EEC 21 is registered.

[0060] Regarding an EAS that is not instantiated, the EES 30 can acquire fixed information such as the location information of the EAS, but cannot obtain detailed information indicating the service performance related to the operation of the EAS. Therefore, the EES 30 selects, for example, an EAS that is located close to the location of the terminal 20 as an EAS that is not instantiated. An example of detailed information indicating the service performance of an EAS (EAS Service KPIs) is shown in FIG. 9.

[0061] <S103: EAS discovery response> In S103, the EES 30 returns an EAS discovery response to the EEC 21. An example of information elements included in the EAS discovery response is shown in FIG. 10. Upon receiving the EAS discovery response, the EEC 21 selects, for example, one instantiated EAS (called a target EAS) from among the multiple EASs included in the EAS discovery response. The EAS that was connected to the terminal 20 before the terminal 20 moved is called a source EAS.

[0062] <S104: ACR> In S104, information (application context) of the AC 22 existing in the source EAS is transferred to the target EAS. Thereafter, the terminal 20 (AC 22) connects to the target EAS and receives services from the target EAS.

[0063] <S105> As mentioned above, there may be an EAS that is more suitable for the current terminal 20 (ACC 22) than the instantiated EAS selected (for service continuity) in S102 to S103.

[0064] Therefore, in this embodiment, the EES 30 instantiates one or more selected non-instantiated EASs during the period from S102 to the present time. The instantiated EASs are referred to as target candidate EASs. The EAS to which the terminal 20 is connected is referred to as the old target EAS.

[0065] The "non-instantiated EAS" to be instantiated is, for example, an instantiable EAS that is expected to satisfy the service discovery conditions (e.g., EAS discovery filters received from the EEC 21) and the service KPIs required by the AC 22. For example, the EES 30 may select an instantiable EAS that is within a predetermined distance from the terminal 20 as the "instantiable EAS that is expected to satisfy the service discovery conditions and the service KPIs of the AC 22."

[0066] The EES 30 compares the service conditions (e.g., KPIs, service authorization levels, AC locations that the EAS can support, etc.) of each of the one or more instantiated target candidate EASs with those of the previous target EAS, and selects a target candidate EAS that has better service conditions than the service conditions of the previous target EAS. Here, the EES 30 may select one target candidate EAS or multiple target candidate EASs.

[0067] A target candidate EAS having better service conditions than the service conditions of the old target EAS is, for example, a target candidate EAS having greater computational resources than the computational resources of the old target EAS.

[0068] More specifically, the EES 30 may select one or more target candidate EASs in the following procedure.

[0069] First, the EES 30 checks whether each of the one or more instantiated target candidate EASs satisfies the service discovery conditions, for example, based on the EAS profile information.

[0070] Next, EES30 compares the service performance (e.g., EAS service KPIs) of each of one or more target candidate EASs that meet the service discovery conditions with that of the previous target EAS, and selects one or more target candidate EASs that have better service performance than the previous target EAS.

[0071] Here, it is assumed that there are one or more target candidate EASs that have better service performance / service conditions than the old target EAS.

[0072] <S106> In S106, the EES 30 notifies the EEC 21 of information about one or more target candidate EASs selected in S105. The information items notified here may be the same as the information items notified in the EAS discovery response. The information about the target candidate EASs includes, for example, the identifier of the target candidate EAS, the address of the target candidate EAS, etc.

[0073] When the EEC 21 receives notification of multiple target candidate EASs, it selects one target candidate EAS (referred to as a new target EAS) from the multiple target candidate EASs. When the EEC 21 receives notification of one target candidate EAS, the selected target candidate EAS becomes the new target EAS.

[0074] Thereafter, for example, based on a trigger by the EEC 21, ACR from the old target EAS to the new target EAS is executed, and the terminal 20 (AC 22) connects to the new target EAS.

[0075] (Variation of Operation) In S106, the EEC 21 that has received the information on the target candidate EAS may reject the ACR to the target candidate EAS (new target EAS).

[0076] Furthermore, before instantiating one or more target candidate EASs, the EES 30 may select one target candidate EAS from among the one or more target candidate EASs, then instantiate the target candidate EAS, and notify the EEC 21 of information about the instantiated target candidate EAS as information about the new target EAS.

[0077] (Summary and Effects of the Embodiment) According to the technology of the present embodiment, a technology is provided for selecting an appropriate server as a target server (EAS) in an ACR. Specifically, the following is provided.

[0078] Since instantiation may increase the time required for ACR, in the conventional technology, an EAS that has already been instantiated is selected while a service requiring continuity is being used. However, in this case, there is a problem that a more appropriate EAS may not be selected, taking into account the connection environment after ACR.

[0079] In order to solve the above problem, in this embodiment, if there is an EAS that can be instantiated and is expected to satisfy the service discovery conditions in parallel with ACR to an EAS that has already been instantiated, the EAS is instantiated (i.e., the EAS is launched), and after confirming that the EAS will improve service performance (e.g., service KPIs), ACR to the EAS is executed.

[0080] (Device Configuration) Next, a description will be given of an example of the functional configuration of the EES 30 that performs the processes and operations described above, and the terminal 20. Hereinafter, the EES 30 will be referred to as a network node 30.

[0081] <Network Node 30> Fig. 11 is a diagram showing an example of the functional configuration of the network node 30. As shown in Fig. 11, the network node 30 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 11 is merely an example. The names of the functional divisions and functional units may be any names as long as they can perform the operations related to the embodiment of the present invention.

[0082] The transmitter 110 has a function of generating a signal to be transmitted to the terminal 20 or a network node and transmitting the signal via a wired or wireless connection. The receiver 120 has a function of receiving various signals transmitted from the terminal 20 or a network node and acquiring, for example, information of a higher layer from the received signal. A communication unit including the transmitter 110 and the receiver 120 may be configured.

[0083] The setting unit 130 stores pre-set setting information and various setting information to be transmitted to the terminal 20 or the network node in a storage device, and reads the information from the storage device as needed. The control unit 140 controls the network node 30. The function unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and the function unit related to signal reception in the control unit 140 may be included in the receiving unit 120. The transmitting unit 110 and the receiving unit 120 may be called a transmitter and a receiver, respectively.

[0084] <Terminal 20> Fig. 12 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 12, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 12 is merely an example. The names of the functional divisions and functional units may be any as long as they can perform the operations related to the embodiment of the present invention.

[0085] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 220 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving NR-PSS, NR-SSS, NR-PBCH, DL / UL control signals, reference signals, and the like transmitted from a network node. A communication unit including the transmitter 210 and the receiver 220 may be configured.

[0086] The setting unit 230 stores various pieces of setting information received from the network node by the receiving unit 220 in a storage device and reads them from the storage device as needed. The setting unit 230 also stores setting information that is set in advance. The content of the setting information is, for example, information related to edge computing.

[0087] The control unit 240 controls the terminal 20. The functional unit in the control unit 240 related to signal transmission may be included in the transmitting unit 210, and the functional unit in the control unit 240 related to signal reception may be included in the receiving unit 220. The transmitting unit 210 and the receiving unit 220 may be called a transmitter and a receiver, respectively.

[0088] (Hardware Configuration) The block diagrams (FIGS. 11 and 12) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0089] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0090] For example, the network node 30 and the terminal 20 according to an embodiment of the present disclosure may function as a computer that performs processing of the communication method of the present disclosure. Fig. 13 is a diagram illustrating an example of the hardware configuration of the network node 30 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 and the terminal 20 described above may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0091] In the following description, the term "device" can be read as a circuit, a device, a unit, etc. The hardware configuration of the network node 30 and the terminal 20 may be configured to include one or more of the devices shown in the figure, or may be configured to exclude some of the devices.

[0092] Each function in the network node 30 and the terminal 20 is realized by loading specified software (programs) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication via the communication device 1004, and controls at least one of reading and writing data in the memory device 1002 and the auxiliary memory device 1003.

[0093] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

[0094] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the network node 30 shown in FIG. 11 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 12 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0095] The storage device 1002 is a computer-readable recording medium and may be configured, for example, by at least one of a read-only memory (ROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to an embodiment of the present disclosure.

[0096] The secondary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0097] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, a transmission / reception antenna, an amplifier unit, a transmission / reception unit, a transmission path interface, etc. may be realized by the communication device 1004. The transmission / reception unit may be implemented as a transmission unit and a reception unit that are physically or logically separated.

[0098] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0099] Furthermore, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0100] Furthermore, the network node 30 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0101] 14 shows an example configuration of a vehicle 2001. As shown in FIG. 14 , the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example. For example, a network node 30 or a terminal 20 may be included in the communication module 2013.

[0102] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0103] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0104] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0105] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013 or the like to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001. The information service unit 2012 may include input devices (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, a touch panel, etc.) that accept input from the outside, and may also include output devices (e.g., a display, a speaker, an LED lamp, a touch panel, etc.) that output information to the outside.

[0106] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0107] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0108] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a terminal, a network node, or the like.

[0109] The communication module 2013 may transmit, via wireless communication, to an external device at least one of signals from the various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc. may be referred to as input units that accept input.

[0110] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021 to 2029, etc. provided in the vehicle 2001.

[0111] Furthermore, when the communication module 2013 includes a network node 30 (or a terminal 20), the communication module 2013 can perform the operations of the network node 30 (or a terminal 20) described above.

[0112] This specification discloses at least the configurations described in the appendices below.

[0113] <Additional Notes> (Additional Item 1) A network node comprising: a control unit that, after a server providing a service to a terminal is changed from a first server to a second server, compares service conditions of the second server with service conditions of a third server; and a transmission unit that, if the service conditions of the third server are better than the service conditions of the second server, transmits information of the third server to the terminal. (Additional Item 2) The network node according to Additional Item 1, wherein the control unit selects an uninstantiated server as the third server, instantiates the server, and then performs the comparison. (Additional Item 3) The network node according to Additional Item 1 or 2, wherein, after the information of the third server is transmitted to the terminal, the server providing a service to the terminal is changed from the second server to the third server. (Supplementary Item 4) A communication system comprising: a network node comprising: a control unit that, after a server that provides a service to a terminal is changed from a first server to a second server, compares service conditions of the second server with service conditions of a third server, and a transmitting unit that, if the service conditions of the third server are better than the service conditions of the second server, transmits information of the third server to the terminal, and a terminal that comprises a receiving unit that receives the information of the third server from the network node. (Supplementary Item 5) A communication method executed by a network node, comprising: a step of comparing service conditions of the second server with service conditions of the third server after a server that provides a service to a terminal is changed from a first server to a second server, and a step of transmitting information of the third server to the terminal if the service conditions of the third server are better than the service conditions of the second server.

[0114] All of Supplementary Items 1 to 5 provide techniques for selecting an appropriate server as a target server in ACR. According to Supplementary Item 2, the comparison is performed after instantiating the third server, so detailed information such as KPIs can be used for the comparison. According to Supplementary Item 3, ACR can be performed to switch to the third server.

[0115] (Supplementary Notes on the Embodiments) Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, and substitutions. While specific numerical examples have been used to facilitate understanding of the invention, unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention; matters described in two or more items may be used in combination as needed, and matters described in one item may apply to matters described in another item (unless inconsistent). Boundaries between functional units or processing units in functional block diagrams do not necessarily correspond to boundaries between physical components. The operations of multiple functional units may be performed by a single physical component, or the operations of a single functional unit may be performed by multiple physical components. The order of processing procedures described in the embodiments may be reversed as long as there is no contradiction. For convenience of processing description, the network nodes 30 / 40 and the terminal 20 have been described using functional block diagrams. However, such devices may be realized by hardware, software, or a combination thereof. The software operated by the processor of the network node 30 in accordance with an embodiment of the present invention and the software operated by the processor of the terminal 20 in accordance with an embodiment of the present invention may each be stored in any suitable storage medium, such as random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, registers, hard disk (HDD), removable disk, CD-ROM, database, server, or the like.

[0116] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0117] Each aspect / embodiment described in the present disclosure may be implemented using any of the following standards: LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or a decimal number)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 ( The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of LTE and / or LTE-A with 5G).

[0118] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be rearranged unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

[0119] In this specification, a specific operation described as being performed by the base station 10 may be performed by its upper node in some cases. In a network consisting of one or more network nodes having the base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and another network node other than the base station 10 (such as, but not limited to, an MME or an S-GW). Although the above example illustrates a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (such as an MME and an S-GW).

[0120] The information, signals, etc. described in the present disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0121] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be transmitted to another device.

[0122] In the present disclosure, the determination may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a comparison of numerical values ​​(e.g., comparison with a predetermined value).

[0123] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0124] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0125] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0126] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0127] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0128] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0129] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0130] In the present disclosure, terms such as "base station (BS)," "radio base station," "base station device," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0131] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage.

[0132] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0133] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0134] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0135] Either the network node 30 or the terminal 20 may be referred to as a transmitting device, a receiving device, a communication device, or the like. Note that either the network node 30 or the terminal 20 may be a device mounted on a mobile object, the mobile object itself, or the like. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. Furthermore, the mobile object may be a mobile object that moves autonomously based on an operation command, a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0136] Furthermore, a base station in the present disclosure may be read as a user terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0137] Similarly, the user terminal in the present disclosure may be read as a base station, in which case the base station may be configured to have the functions of the user terminal described above.

[0138] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0139] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0140] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0141] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0142] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0143] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0144] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0145] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0146] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0147] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0148] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0149] 10 Base station 20 Terminal 21 EEC 22 AC 30 EES 40 EAS 50 ECS 110 Transmitter 120 Receiver 130 Setting unit 140 Controller 210 Transmitter 220 Receiver 230 Setting unit 240 Controller 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device

Claims

1. A network node comprising: a control unit that compares service conditions of a second server with service conditions of a third server after a server providing a service to a terminal is changed from a first server to the second server; and a transmission unit that transmits information on the third server to the terminal when the service conditions of the third server are superior to the service conditions of the second server.

2. The network node according to claim 1, wherein the control unit selects a non-instantiated server as the third server, instantiates the server, and then performs the comparison.

3. The network node according to claim 1, wherein after the information on the third server is transmitted to the terminal, the server providing the service to the terminal is changed from the second server to the third server.

4. A communication system comprising: a network node comprising: a control unit that compares service conditions of a second server with service conditions of a third server after a server providing a service to a terminal is changed from a first server to the second server; and a transmission unit that transmits information on the third server to the terminal when the service conditions of the third server are superior to the service conditions of the second server; and a terminal comprising a reception unit that receives the information on the third server from the network node.

5. A communication method executed by a network node, the method comprising: comparing service conditions of a second server with service conditions of a third server after a server providing a service to a terminal is changed from a first server to the second server; and transmitting information on the third server to the terminal when the service conditions of the third server are superior to the service conditions of the second server.

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