Method and apparatus for service discovery while a mobile device is in motion

Abstract

According to one embodiment, a method is provided for execution by a first communication node in a target network. The method includes maintaining a local cache that identifies services known to be available to communication devices in the target network. The method also includes receiving at least one service identifier from a second communication node during a handover procedure for the communication device from the initial network to the target. According to one embodiment of the present disclosure, for each service identifier, the method includes signaling the service repository in the target network to discover the service only if the service corresponding to the service identifier is not identified in the local cache. In this way, repeated service discovery can be reduced.

Description

Technical Field

[0001] Related Applications This patent application claims the priority of PCT provisional patent application No. PCT / CN2023 / 076345 filed on February 16, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to a wireless communication system, and more particularly to service discovery by a communication node during movement of a mobile device.

Background Art

[0003] First, referring to FIG. 1, a sequence diagram of a method for registering a UE (User Equipment) to a network by a known procedure is shown. When the UE first connects to 5G NR (New Radio), the UE executes a registration procedure in NR. The registration procedure is self-explanatory by referring to steps 1 to 25 shown, and further details regarding steps 1 to 25 can be found in 3GPP TS23.502 entitled "Procedures for the 5G System (5GS); Stage2" version 18.1.0 uploaded on December 21, 2022 (hereinafter, "3GPP TS23.502").

[0004] Several related procedures utilize one or more SUPIs (Subscription Permanent Identifiers) for NRF (Network Repository Function) discovery of services. Each SUPI belongs to a single UDM (Unified Data Management) group ID, AUSF (Authentication Server Function) group ID, UDR (Unified Data Repository) group ID, and / or PCF (Policy Control Function) group ID. However, multiple different SUPIs can belong to the same group ID. The NF (Network Function) group ID applies to all NF services.

[0005] The Access and Mobility Management Function (AMF) can use UE SUPI to perform NRF discovery for the Unified Endpoint Configuration Management (UDM) service. The AMF can select one UDM from the UDM list returned by the NRF, and from the selected UDM's udminfo (see Table 1 below), it can obtain the corresponding UDM group ID to which the UE SUPI belongs. Using the previously received UDM group ID, the AMF finds UDM_SDM from its local cache, and NRF discovery for UDM_SDM is skipped. Next, the AMF uses UE SUPI to perform NRF discovery for the Access Mobility Policy (PCF) service. The AMF can select one PCF from the PCF list returned by the NRF, and from the selected UDM's pcfinfo (see Table 2 below), it can obtain the corresponding PCF group ID.

[0006] When a UE executes a PDU (Packet Data Unit) session establishment procedure in an NR, the AMF can send an Nsmf_PDUSession_CreateSMContext request with the UDM group ID and PCF group ID to the SMF (Session Management Function). Alternatively, the AMF can send an Nsmf_PDUSession_CreateSMContext request with the UDM group ID and PCF group ID to the I-SMF (Intermediate Session Management Function), which then sends an Nsmf_PDUSession_Create request with the UDM group ID and PCF group ID to the SMF. Nevertheless, the SMF can use the received UDM group ID to perform NRF discovery for the UDM UECM service and use the received PCF group ID to perform NRF discovery for the PCF AM policy service.

[0007] Unfortunately, iterative NRF discovery for UDM UECM services and NRF discovery for PCF AM policy services can be time-consuming because such discoveries involve signaling to NRFs. More generally, iterative service discovery within a communications system can be time-consuming because such discoveries typically involve signaling to service repositories. Tables 1 and 2, referenced above, are shown below. Table 1: Definition of Type UdmInfo TIFF2026510218000002.tif250170TIFF2026510218000003.tif32170Table 2: Definition of Type PcfInfo TIFF2026510218000004.tif250170TIFF2026510218000005.tif47170 [Overview of the project]

[0008] According to one embodiment, a method for execution by a first communication node in a target network is provided. The method includes maintaining a local cache that identifies services known to be available to communication devices in the target network. The method also includes receiving at least one service identifier from a second communication node during a handover procedure for the communication device from the initial network to the target.

[0009] Service identifiers can be used for service discovery. However, repeated service discovery typically involves signaling to remote repositories, which can be time-consuming. According to one embodiment of the present disclosure, the method includes, for each service identifier, signaling to the service repository on the target network if the service corresponding to the service identifier is not identified in the local cache, and skipping signaling to the service repository if the service is identified in the local cache.

[0010] In this way, the need for repeated service discovery can be reduced. For example, in some situations, signaling with the service repository is skipped for a subset of service identifiers. In other situations, signaling with the service repository is skipped for all service identifiers. It should be noted that this benefit can be enjoyed by a huge number of UEs (e.g., millions) performing migration procedures (e.g., migration from 4G to 5G), resulting in a better experience for UE migration.

[0011] In some implementations, at least one service identifier includes a UDM (Unified Data Management) group ID and / or a PCF (Policy Control Function) group ID. Therefore, it is possible to skip the discovery of the UDM UECM (Unified Endpoint Configuration Management) service and / or the PCF AM (Access Mobility) policy service. Such discovery skips can help expedite processing for handover procedures when the local cache allows such skips.

[0012] In another embodiment, a non-temporary computer-readable medium is provided which, when executed by the processor of the first communication node, records statements and instructions that configure the processor to implement the method summarized above.

[0013] In another embodiment, a first communication node of a target network is provided. The first communication node has a network interface configured to communicate with other communication nodes, a computer-readable medium configured to maintain a local cache that identifies services known to be available to communication devices in the target network, and a service discovery circuit coupled to the network interface and the computer-readable medium.

[0014] According to one embodiment of the present disclosure, during the handover procedure of a communication device from the initial network to the target, the service discovery circuit receives at least one service identifier from a second communication node via the network interface, and is configured to signal to the service repository of the target network if the service is not identified in the local cache, in order to discover the service corresponding to the service identifier via the network interface, and to skip signaling to the service repository if the service is identified in the local cache.

[0015] Other aspects and features of the present disclosure will become apparent to those skilled in the art by considering the following descriptions of various embodiments of the present disclosure.

[0016] The embodiments will be described below with reference to the attached drawings. [Brief explanation of the drawing]

[0017] [Figure 1] This is a sequence diagram of the method for registering a UE to the network using a known procedure. [Figure 2] This is a block diagram of a communication system having a pair of communication nodes to facilitate service discovery within the communication system. [Figure 3] Figure 2 is a flowchart illustrating a service discovery method using the communication system, which reduces the need for repeated service discovery. [Figure 4] This is a flowchart of an alternative method of service discovery by a communication system that reduces the repetition of service discovery according to the first embodiment. [Figure 5] This is a flowchart of an alternative method of service discovery by a communication system that reduces the repetition of service discovery, according to the second embodiment. [Figure 6A] This is a sequence diagram of the method for handover from EPS to 5GS using the N26 interface. [Figure 6B]It is a sequence diagram of a method for creating a PDU session. [Figure 7] It is a schematic diagram of an exemplary cellular communication system in which some embodiments of the present disclosure can be implemented. [Figure 8A] It is a block diagram of a wireless communication system represented as a 5G network architecture in which some embodiments of the present disclosure can be implemented. [Figure 8B] It is a block diagram of a wireless communication system represented as a 5G network architecture in which some embodiments of the present disclosure can be implemented. [Figure 9] It is a block diagram of a wireless access node according to some embodiments of the present disclosure. [Figure 10] It is a block diagram showing a virtualized embodiment of a wireless access node according to some embodiments of the present disclosure. [Figure 11] It is a block diagram of a wireless access node according to some embodiments of the present disclosure. [Figure 12] It is a block diagram of a wireless communication device. [Figure 13] It is a block diagram of a wireless communication device. [Figure 14] It is a schematic diagram of an exemplary communication system according to some embodiments of the present disclosure.

Embodiments for Carrying Out the Invention

[0018] First, exemplary implementations of one or more embodiments of the present disclosure are provided below, but it should be understood that the disclosed system and / or method can be implemented using any number of technologies. The present disclosure should in no way be limited to the exemplary implementations, drawings, and techniques shown below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims, together with the full scope of their equivalents.

[0019] Introduction Referring first to Figure 2, a block diagram of a communication system 100 having communication nodes 124 and 134 of the target network 102 is shown to facilitate service discovery within the target network 102. Communication nodes 124 and 134 include at least a first communication node 124 and a second communication node 134. The communication system 100 also has a service repository 144 and a communication device 110 engaged in handover from the initial network 101 to the target network 102. Typically, the communication system 100 has numerous communication devices, but these are not shown for simplicity. The communication system 100 also typically has other components, but these are also not shown for simplification.

[0020] The first communication node 124 is configured to handle access and mobility management for communication devices such as communication device 110. In some implementations, the first communication node 124 is a component of the core network, for example, the AMF (Access and Mobility Management Function) of a 5G core network. However, other implementations are also possible and within the scope of this disclosure. The first communication node 124 has a network interface 125 configured to communicate with other nodes of the communication system 100, a computer-readable medium 129, and a component discovery circuit 126 coupled to the network interface 125 and the computer-readable medium 129. In some implementations, the component discovery circuit 126 includes a processor 127 that runs software that may originate from memory 128. However, other implementations are also possible and within the scope of this disclosure. The first communication node 124 may have additional components, which are not shown for the sake of brevity.

[0021] The second communication node 134 is configured to handle communication sessions for communication devices such as communication device 110. In some implementations, the second communication node 134 is a component of the core network, for example, the SMF (Session Management Function) of a 5G core network. However, other implementations are also possible and within the scope of this disclosure. The second communication node 134 has a network interface 135 configured to communicate with other nodes of the communication system 100, and also has an identifier transmission circuit 136 coupled to the network interface 125. In some implementations, the identifier transmission circuit 136 includes a processor 137 that executes software that may originate from memory 138. However, other implementations are also possible and within the scope of this disclosure. The second communication node 134 may have additional components, which are not shown for the sake of simplicity.

[0022] The component discovery circuit 126 of the first communication node 124 and the identifier transmission circuit 136 of the second communication node 134 operate to implement a service discovery method by the communication system 100 that reduces the repetition of service discovery. Such operation will be described with reference to Figure 3. The method in Figure 3 will be described below with reference to the communication system 100 shown in Figure 2, but it should be understood that the method in Figure 3 is applicable to other communication systems as well. In general, the method in Figure 3 is applicable to any appropriately configured communication system.

[0023] In step 3-1, the first communication node 124 maintains a local cache that identifies services known to be available to the communication device 110 in the target network 102. The local cache can be stored, for example, in a computer-readable medium 129.

[0024] As described above, the communication device 110 is engaged in a handover from the initial network 101 to the target network 102. During such a handover, in step 3-2, the second communication node 134 transmits at least one service identifier, and in step 3-3, the first communication node 124 receives the service identifier. The service identifier can be used for service discovery. In the illustrated example, the service identifier includes a first service identifier and a second service identifier.

[0025] As noted above, repeated service discovery typically involves signaling to service repository 144 and can therefore take some time. As described below, repeated service discovery can be mitigated by using a local cache.

[0026] If, in step 3-4, the local cache does not identify the first service corresponding to the first service identifier ID, then in step 3-5, the first communication node 124 signals the service repository 144 to discover the first service. However, if, in step 3-4, the local cache does identify the first service, then in step 3-6, the first communication node 124 skips discovering the first service (i.e., does not engage in signaling with the service repository 144).

[0027] With respect to the second service identifier ID, if in step 3-7 the local cache does not identify the second service corresponding to the second service identifier, in step 3-8 the first communication node 124 signals the service repository 144 to discover the first service. However, if in step 3-7 the local cache does identify the second service, in step 3-9 the first communication node 124 skips discovering the second service (i.e., does not participate in signaling with the service repository 144).

[0028] Therefore, the need for repeated service discovery can be reduced. For example, in some situations, signaling with the service repository is skipped for a subset of service identifiers. In other situations, signaling with the service repository is skipped for all service identifiers. It should be noted that this benefit can be enjoyed by a huge number of UEs (e.g., millions) performing migration procedures (e.g., from 4G mobility to 5G), resulting in a better experience for UE migration.

[0029] There are many possibilities for service identifiers. In some implementations, the service identifier includes a UDM (Unified Data Management) group ID and / or a PCF (Policy Control Function) group ID. In such implementations, the service corresponding to the UDM group ID may be the UDM UECM (Unified Endpoint Configuration Management) service or the UDM SDM (Subscriber Data Management) service, and the service corresponding to the PCF group ID may be the PCF AM (Access Movement) policy service. Therefore, it is possible to skip the discovery of the UDM UECM service and / or the PCF AM policy service. Skipping such discovery can help expedite processing for the handover procedure when the local cache allows such skipping.

[0030] According to the conventional approach, when a UE moves to an NR (New Radio 5G) network, the AMF (Access and Mobility Management Function) still uses SUPI to perform NRF (Network Repository Function) discovery for UDM UECM services and PCF AM policy services. The current 3GPP standard lacks the functionality to allow the AMF to reuse existing UDM / PCF group IDs for this PDU session, which may be obtained from the SMF (the SMF obtains the NF group ID during the 4G PDN connection establishment procedure). Therefore, embodiments of the present disclosure represent a substantial improvement over the conventional approach.

[0031] In some implementations, the first communication node includes an AMF, the target network includes an NR network, the initial network includes an LTE (Long-Term Evolution) network, and the service repository includes an NRF. Other implementations are also possible.

[0032] In some implementations, the second communication node includes an SMF (Session Management Function). This example is described below with reference to Figure 4 (i.e., the first embodiment). In other implementations, the second communication node includes an MME (Mobile Management Entity). In such implementations, the MME may obtain a service identifier from the SMF. This example is described below with reference to Figure 5 (i.e., the second embodiment). Other implementations are also possible.

[0033] According to another embodiment of the present disclosure, a non-temporary computer-readable medium is provided, which, when executed by the processor 127 of the first communication node 124, contains statements and instructions that implement the methods described herein. The non-temporary computer-readable medium may be the memory 128 of the first communication node 124 as shown in Figure 1, or any other non-temporary computer-readable medium.

[0034] According to another embodiment of the present disclosure, a non-temporary computer-readable medium is provided, which, when executed by the processor 137 of the second communication node 134, contains statements and instructions that implement the methods described herein. The non-temporary computer-readable medium may be the memory 138 of the second communication node 134 as shown in Figure 1, or any other non-temporary computer-readable medium.

[0035] Examples of non-temporary computer-readable media include memory, SSDs (solid-state drives), hard disk drives, CDs (compact discs), DVDs (digital video discs), BDs (Blu-ray discs), and memory sticks.

[0036] The illustrated examples described herein focus on software implementations. However, other implementations are possible and within the scope of this disclosure. Note that other implementations may include additional or alternative hardware components, such as any appropriately configured FPGA (Field-Programmable Gate Array), ASIC (Application-Specific Integrated Circuit), and / or microcontroller. Thus, the session update circuit 126 of the first communication node 124 and the session update circuit 136 of the second communication node 134 may instead be implemented in any preferred combination of hardware, software, and / or firmware.

[0037] Further illustrative details are provided in the following sections. These sections are highly specific, and other implementations are possible; they are provided solely for illustrative purposes, as they fall within the scope of this disclosure.

[0038] First Embodiment According to the first embodiment, if there is an LTE handover to the NR, the AMF receives the UDM / PCF group ID from the SMF during the Nsmf_PDUSession_CreateSMContext procedure. During the LTE handover to the NR, the SMF may send the UDM / PCF group ID to the AMF in the Nsmf_PDUSession_CreateSMContext response. After the LTE handover procedure is completed, the AMF executes the registration procedure.

[0039] The AMF can use the received UDM group ID to perform NRF discovery for UECM services, but this NRF discovery procedure for UDM UECM services can be skipped if a local cache exists. Furthermore, the AMF can use the received PCF group ID to perform NRF discovery for PCF AM policy services, but this NRF discovery procedure can also be skipped if a local cache exists.

[0040] Therefore, depending on the local cache, it is possible to skip two NRF discovery products (i.e., NRF discovery for UDM UECM services and NRF discovery for PCF AM policy services) to facilitate processing for LTE handover to NR.

[0041] Further details of the first embodiment will be described below with reference to Figure 4, which is a flowchart of another service discovery method using the communication system according to the first embodiment.

[0042] In step 4-1, after the UE establishes a PDN connection on 4G, the UE initiates an LTE handover to NR by sending a handover instruction to E-UTRAN (Advanced UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network).

[0043] In step 4-2, E-UTRAN sends a handover request to the MME.

[0044] In step 4-3, the MME sends a forward relocation request to the AMF.

[0045] In step 4-4, the AMF sends an Nsmf_PDUSession_CreateSMContext request (RAT type: NR) to the SMF.

[0046] In steps 4-5, the SMF executes a PFCP session change procedure with the UPF.

[0047] In steps 4-6, the SMF sends the Nsmf_PDUSession_CreateSMContext response (SmContextCreatedData\UDM group ID, PCF group ID) to the AMF. The UDM group ID and PCF group ID are new attributes. Table 3 below provides illustrative details of SmContextCreatedData. Table 3: Definition of Type SmContextCreatedData TIFF2026510218000006.tif88170

[0048] In step 4-7, the AMF sends a handover request to the NG-RAN.

[0049] In step 4-8, NG-RAN sends a handover request Ack to AMF.

[0050] In step 4-9, the UE continues the LTE handover procedure to NR.

[0051] In step 4-10, after the UE has completed the LTE handover to NR, the UE sends a registration request to the AMF.

[0052] In step 4-11, the AMF can use the received UDM group ID to perform NRF discovery for the UDM UECM service. However, the NRF discovery procedure for the UDM UECM may be skipped if a local cache exists.

[0053] In step 4-12, the AMF executes the Nudm_UECM_Registration request / response with the UDM.

[0054] In step 4-13, AMF executes the Nudm_SDM_GET procedure with UDM to retrieve AccessAndMobilitySubscriptionData.

[0055] In step 4-14, AMF executes the Nudm_SDM_GET procedure for smf-select-data with UDM.

[0056] In step 4-15, AMF executes the Nudm_SDM_Subscribe procedure with UDM.

[0057] In step 4-16, the AMF can use the received PCF group ID to perform NRF discovery for the PCF AM policy service. However, this NRF discovery procedure may be skipped if a local cache exists.

[0058] In step 4-17, AMF executes the Npcf_AMPolicyControl_Create procedure with PCF.

[0059] In step 4-18, the MME performs resource cleanup within the EPC.

[0060] Note that the first embodiment may not be applicable if the UE performs an LTE idle move to NR or a Wi-Fi move to NR, as the AMF registration procedure takes place before the interaction between the AMF and SMF.

[0061] Second Embodiment According to the second embodiment, the AMF receives the UDM / PCF group ID from the MME during LTE migration to 5G. During the LTE session establishment procedure, if interworking with NR is supported, the SMF sends the UDM / PCF group ID to the MME. When the UE performs a handover / idle migration from 4G to 5G, the MME can forward the UDM / PCF group ID to the AMF.

[0062] The AMF can use the received UDM group ID to perform NRF discovery for UECM services, but this NRF discovery procedure for UDM UECM services can be skipped if a local cache exists. Furthermore, the AMF can use the received PCF group ID to perform NRF discovery for PCF AM policy services, but this NRF discovery procedure can also be skipped if a local cache exists.

[0063] Therefore, it is possible to skip two NRF discovery products (i.e., NRF discovery for UDM UECM services and NRF discovery for PCF AM policy services) to expedite processing for the PDU session LTE handover to NR procedure or the LTE idle move to NR procedure.

[0064] Further details of the second embodiment will be described below with reference to Figure 5, which is a flowchart of another service discovery method using the communication system according to the second embodiment.

[0065] In step 5-1, the UE establishes a PDN connection over 4G. The MME sends a session creation request to the SMF.

[0066] In step 5-2, since the SMF has already set up the UDM and PCF connections and obtained the UDM / PCF group IDs, the SMF sends a session creation response to the MME along with the new attribute UDM group ID and PCF group ID. An example of the session creation response is provided in Table 4 below. Table 4: Information elements in session creation response TIFF2026510218000007.tif53170

[0067] In step 5-3, the UE sends a handover instruction to the E-UTRAN.

[0068] In step 5-4, E-UTRAN sends a handover request to the MME.

[0069] In step 5-5, the MME sends a forward relocation request to the AMF along with the new attribute UDM group ID and PCF group ID. An illustrative detail of the forward relocation request is provided in Table 5 below. Table 5: MME / SGSN / AMF UE EPS PDN Connection in Forward Relocation Requests TIFF2026510218000008.tif84170

[0070] In steps 5-6, the AMF sends an Nsmf_PDUSession_CreateSMContext request (RAT type: NR) to the SMF.

[0071] In step 5-7, the SMF executes a PFCP session change procedure with the UPF.

[0072] In steps 5-8, the SMF sends an Nsmf_PDUSession_CreateSMContext response to the AMF. Exemplary details of the context response are provided in Table 6 below. Table 6: MME / SGSN / AMF UE EPS PDN connections in context responses TIFF2026510218000009.tif84170

[0073] In step 5-9, the AMF sends a handover request to the NG-RAN.

[0074] In step 5-10, NG-RAN sends a handover request Ack to AMF.

[0075] In step 5-11, the UE continues the LTE handover procedure to NR.

[0076] In step 5-12, after the UE has completed the LTE handover to NR, the UE sends a registration request to the AMF.

[0077] In step 5-13, the AMF uses the received UDM group ID to perform NRF discovery for the UECM service, however, the NRF discovery procedure for the UDM UECM service may be skipped if a local cache exists.

[0078] In step 5-14, the AMF executes the Nudm_UECM_Registration request / response with the UDM.

[0079] In step 5-15, AMF executes the Nudm_SDM_GET procedure with UDM to retrieve AccessAndMobilitySubscriptionData.

[0080] In step 5-16, AMF executes the Nudm_SDM_GET procedure for smf-select-data with UDM.

[0081] In step 5-17, AMF executes the Nudm_SDM_Subscribe procedure with UDM.

[0082] In step 5-18, the AMF uses the received PCF group ID to perform NRF discovery for the PCF AM policy service, but this NRF discovery procedure can be skipped if a local cache exists.

[0083] In step 5-19, AMF executes the Npcf_AMPolicyControl_Create procedure with PCF.

[0084] Step 5-20 involves resource cleanup within the EPC by the MME.

[0085] Please note that the second embodiment may not be applicable to Wi-Fi access, as the 3GPP standard does not define an interface between epdg and AMF.

[0086] Further details Further details will be provided. It should be understood that these details are highly specific for illustrative purposes only. The further details provide non-limiting examples of how some aspects disclosed herein may be implemented within the framework of a particular standard (e.g., 3GPP TS29.502, version 18.1.0, “5G System; Session Management Services; Stage 3,” uploaded on December 16, 2022, hereinafter “3GPP TS29.502”). The changes are intended solely to illustrate how some aspects disclosed herein may be implemented in a particular standard. However, the aspects disclosed herein may also be implemented in other appropriate forms in both a particular standard and other specifications or standards.

[0087] For all other UE SUPIs belonging to the UDM / PCF group ID, the SMF does not need to perform an external NRF discovery procedure toward the NRF for each individual UE SUPI; instead, the SMF uses the UDM / PCF group ID (instead of each individual UE SUPI) to find the appropriate UDM / PCF from the local NRF cache. For all UE SUPIs belonging to the UDM / PCF group ID, this saves two NRF discovery generation processes in the SMF (NRF discovery for the UDM UECM and NRF discovery for the PCF), speeding up the PDU session establishment procedure.

[0088] When one UE first connects to the 4G EPC using either 3GPP or non-3GPP access, there is no NF group ID input from the MME / ePDG. Therefore, a combined PWG-C / SMF configured to use N10 to store PDU session information in the UDM can perform NRF discovery for the UDM and PCF using SUPI. The SMF can then select a UDM / PCF from the returned UDM / PCF list of the NRF discovery, and obtain the corresponding UDM / PCF group ID from the udminfo / pcfinfo of the selected UDM / PCF.

[0089] When the UE first connects to 4G, the SMF can obtain the UDM group ID and PCF group ID. When the UE performs a migration from 4G to 5G, the AMF can obtain the UDM group ID and PCF group ID obtained during the 4G establishment procedure from the SMF or MME and use the UDM group ID and PCF group ID to skip NRF discovery if a local cache exists. This improvement can speed up the procedure from 4G mobility to 5G by skipping two NRF discovery generation (NRF discovery for UDM UECM and NRF discovery for PCF AM policy).

[0090] The NF group ID can be used to facilitate NF selection for SUPIs related to the same NF group if the NF consumer has already memorized NF profiles for NFs with the same NF group ID through previous NF selection signaling. PCF Group ID: This refers to one or more PCF instances that manage a particular set of SUPIs. A PCF group consists of one or more PCF sets. UDM Group ID: This refers to one or more UDM instances that manage a specific set of SUPIs. A UDM group consists of one or more sets of UDMs.

[0091] As specified in 3GPP TS23.501, Based on the results of the UDM discovery procedure with the NRF, the AMF can infer the UDM group ID to which the UE's SUPI belongs. The AMF provides the UDM group ID to which the SUPI belongs to other UDM NF consumers, as described in TS23.502.

[0092] Therefore, other UDM NF consumers can use the associated UDM group ID to facilitate UDM selection for this SUPI, and can skip network signaling to the NRF for service discovery, considering that NF profiles of candidate UDMs with the same UDM group ID are likely to be available in the cache.

[0093] However, if the UE initially connects to the network via 4G access, only the combined PGW-C / SMF may have UDM group ID information after performing UDM selection. In such a scenario, it is beneficial to return the UDM group ID from the SMF to the AMF during the 4G to 5G handover procedure, which takes place before the signaling dialogue between the SMF and AMF and the signaling procedure between the AMF and UDM. As a result, using the UDM group ID, the AMF may skip signaling toward the NRF and instead select a UDM from its local cache.

[0094] Similarly, SMF may provide AMF with a PCF group ID (for session management policy control) to facilitate AMF's selection of AM / UE policy PCFs.

[0095] It is proposed to include two new attributes, "udmGroupId" and "pcfGroupId", in the data types SmContextCreatedData and PduSessionCreatedData. Otherwise, there may be extra signaling from the target AMF to the NRF to select the UDM / PCF.

[0096] Preparing for handover from EPS to 5GS using the N26 interface. An NF service consumer (e.g., AMF) requests SMF to hand over the UE EPS PDN connection to 5GS using the N26 interface, as shown in Figure 6A.

[0097] In step 6A-1, the NF service consumer shall send a POST request with the following additional information, as specified in section 5.2.2.2.1 of 3GPP TS29.502: - UE EPS PDN connection containing EPS bearer contexts representing individual SM context resources to be created. - The hoState attribute set in PREPARING (see section 5.2.2.3.4.1 of 3GPP TS29.502), - Instructions on whether direct DL data transfer or indirect DL data transfer is applied, and - A targetId that identifies the target RAN node ID and TAI based on the target ID IE received in the forward relocation request message from the source MME. Note 1: The target ID IE can be set to a target NG-RAN node ID including the global RAN node ID and a selected TAI of 3 octets, or to a target eNB ID including the global eNB ID and a selected TAI of 2 octets. In the latter case, the NF service consumer, i.e., AMF, must determine the values ​​of the target NG-RAN node ID and the 3-octet TAI based on the local settings provided to SMF.

[0098] In step 6A-2a, upon receiving such a request, if the corresponding PDU session is found based on the EPS bearer context (after calling the create service operation toward H-SMF for the home-routed PDU session) and it is possible to proceed with handing over the PDN connection to 5GS, the SMF shall return a 201 create response containing the following information: - The hoState attribute set to PREPARING, as specified in step 2 of Figure 5.2.2.3.4.2-1 of 3GPP TS29.502, and N2 SM information to request the target 5G-AN to allocate resources to the PDU session (if the SMF indicated in step 1 that direct data transfer is applicable, the SMF shall include an indication in the N2 SM information that a direct transfer path is available), - PDU session ID corresponding to the default EPS bearer ID for EPS PDN connection, - S-NSSAI assigned to the PDU session (in the case of home-routed roaming, the S-NSSAI of the home PLMN will be returned), - allocatedEbiList(includes EBIs allocated to PDU sessions), - udmGroupId, which includes identification information for the UDM group serving the UE, to facilitate UDM selection in the target AMF, and - A pcfGroupId containing PCF group identification information for session management policies for PDU sessions, to facilitate PCF selection in the target AMF. The "Location" header should be present in the POST response and should contain the URI of the created SM context resource. An NF service consumer (e.g., AMF) shall store the association between PDU session IDs and SMF IDs, and shall store the assigned EBI associated with the PDU session ID. Note 2: The behavior specified in this step also applies if the POST request conflicts with an existing SM context, i.e., if the POST request includes the same SUPI, or a PEI for an urgently registered UE without UICC or authenticated SUPI, and the default EPS bearer ID received in the UE EPS PDN connection is the same as that in the existing SM context.

[0099] Step 6A-2b is the same as step 2b in Figure 5.2.2.7.1-1 of 3GPP TS29.502, with the following additions. Steps 3 and 4 in Figure 5.2.2.3.8.2-1 of 3GPP TS29.502 are skipped in this case. If SMF determines that seamless session continuity from EPS to 5GS is not supported for a PDU session, SMF shall set the “Cause” attribute in the ProblemDetails structure to “NO_EPS_5GS_CONTINUITY”. Upon receiving a 4xx / 5xx response from the SMF, the NF service consumer (e.g., AMF) shall assume that the hoState of the SM context is NONE.

[0100] Preparing for handover from EPS to 5GS The requirements set forth in Section 5.2.2.7.1 of 3GPP TS29.502 shall apply with the following modifications:

[0101] Step 6B-1 in Figure 6B is the same as Step 1 in Figure 5.2.2.7.1-1 of 3GPP TS29.502, with the following modifications. A POST request shall include the following: - List of EPS bearer IDs received from MME, - PGW S8-C F-TEID received from MME, and - The hoPreparationIndication IE is set to "true" to indicate that handover preparation is in progress and PGW-C / SMF has not yet switched the DL user plane for the PDU session.

[0102] Step 6B-2a is the same as Step 2 in Figure 5.2.2.7.1-1 of 3GPP TS29.502, with the following modifications: If the SMF can locate the corresponding PDU session based on the EPS Bearer ID and PGW S8-C F-TEID received in the request and proceed with the procedure, the SMF shall return a 201 Created response containing the following information: - PDU session ID compatible with EPS PDN connection, - Other PDU session parameters such as PDU session type, session AMBR, and QoS flow information. - udmGroupId containing identification information for the UDM group serving the UE to facilitate UDM selection in the target AMF (V / I-SMF shall transfer this IE to the target AMF in SmContextCreatedData), and - A pcfGroupId containing the identification information of the PCF group for the session management policy for the PDU session, to facilitate PCF selection in the target AMF. The V / I-SMF shall forward this IE to the target AMF in SmContextCreatedData. SMF shall not switch the DL user plane for a PDU session if the hoPreparationIndication IE is set to "true" in the request. (Note): The behavior specified in this step also applies when a POST request conflicts with an existing PDU session context, i.e., when the POST request includes the same SUPI, or a PEI for an emergency registration UE without UICC or authenticated SUPI, and the received EPS bearer ID is the same as the existing PDU session context.

[0103] Step 6B-2b is the same as step 2b in Figure 5.2.2.7.1-1 of 3GPP TS29.502, with the following additions: If H-SMF determines that seamless session continuity from EPS to 5GS is not supported for a PDU session, H-SMF shall set the “Cause” attribute in the ProblemDetails structure to “NO_EPS_5GS_CONTINUITY”. Type: SmContextCreatedData Table 7: Definition of Type SmContextCreatedData TIFF2026510218000010.tif238170TIFF2026510218000011.tif243170TIFF2026510218000012.tif243170TIFF2026510218000013.tif88170Type: PduSessionCreatedData Table 8: Definition of Type PduSessionCreatedData TIFF2026510218000014.tif236170TIFF2026510218000015.tif240170TIFF202 6510218000016.tif246170TIFF2026510218000017.tif245170TIFF20265102180 00018.tif240170TIFF2026510218000019.tif240170TIFF2026510218000020.t if240170TIFF2026510218000021.tif245170TIFF2026510218000022.tif123170

[0104] Exemplary communication system Figure 7 shows an example of a cellular communication system 500 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communication system 500 is a 5GS (5G system) including an NG-RAN (next-generation RAN) and a 5GC (5G core). In this example, the RAN includes base stations 102-1 and 502-2, which include NR base stations (gNBs) in the 5GS, and optionally a next-generation eNB (ng-eNB) (e.g., an LTE RAN node connected to the 5GC) that controls the corresponding (macro) cells 504-1 and 504-2. Base stations 502-1 and 502-2 are generally referred to collectively as base stations 502 and individually as base stations 502 in this specification. Similarly, (macro) cells 504-1 and 504-2 are generally referred to collectively as (macro) cells 504 and individually as (macro) cells 504 in this specification. The RAN may also include several low-power nodes 506-1 to 506-4 that control the corresponding small cells 508-1 to 508-4. The low-power nodes 506-1 to 506-4 may be small base stations (such as pico base stations or femto base stations) or RRHs (remote radio heads), etc. In particular, although not shown, one or more of the small cells 508-1 to 508-4 may alternatively be provided by base station 502. In this specification, the low-power nodes 506-1 to 508-4 are collectively referred to as low-power nodes 506 and individually as low-power nodes 506. Similarly, the small cells 508-1 to 508-4 are generally referred to collectively as small cells 508 and individually as small cells 508. The cellular communication system 500 also includes a core network 510, which in a 5G system (5GS) is called 5GC. Base station 502 (and possibly low-power node 506) is connected to core network 510.

[0105] Base station 502 and low-power node 506 provide services to wireless communication devices 512-1 through 512-5 in corresponding cells 504 and 508. Wireless communication devices 512-1 through 512-5 are generally referred to collectively as wireless communication device 512 and individually as wireless communication device 512 in this specification. In the following description, wireless communication device 512 is often a UE, but this disclosure is not limited thereto.

[0106] Referring to Figure 8A, a block diagram of a wireless communication system is shown, represented as a 5G network architecture consisting of core NFs (Network Functions), where interaction between any two NFs is represented by point-to-point reference points / interfaces. Figure 8A can be seen as one specific implementation form of system 500 in Figure 7.

[0107] From the access side, the 5G network architecture shown in Figure 8A includes multiple UE613s connected to either the RAN607 or (access network) and the AMF600. Typically, the R(AN)607 includes base stations such as eNBs or gNBs. From the core network side, the 5GC NF shown in Figure 8A includes the NSSF602, AUSF604, UDM606, AMF600, SMF608, PCF610, and the AF (Application Function)612.

[0108] Reference point representations for 5G network architectures are used in normative standardization to develop detailed call flows. Reference point N1 is defined to carry signaling between UE613 and AMF600. Reference points for connecting AN607 and AMF600, and AN607 and UPF614 are defined as N2 and N3, respectively. Reference point N11 exists between AMF600 and SMF608, meaning that SMF608 is at least partially controlled by AMF600. N4 is used by SMF608 and UPF614 so that UPF614 can be configured using control signals generated by SMF608 and can report its state to SMF608. N9 is a reference point for connections between different UPF614s, and N14 is a reference point for connecting different AMF600s. N15 and N7 are defined so that PCF610 applies policies to AMF600 and SMF608, respectively. N12 is used by the AMF600 to authenticate the UE613. N8 and N10 are defined because the UE613's subscriber data is used for the AMF600 and SMF608.

[0109] The 5GC network aims to separate the UP and CP. The UP carries user traffic, while the CP carries signaling within the network. In Figure 8A, UPF614 is located within the UP, while all other NFs, namely AMF600, SMF608, PCF610, AF612, NSSF602, AUSF604, and UDM606, are located within the CP. Separating the UP and CP ensures that each plane resource scales independently. It also allows for the deployment of the UPF in a distributed manner, separate from the CP functionality. In this architecture, the UPF can be deployed very close to the UE to reduce the round-trip time (RTT) between the UE and the data network for some low-latency applications.

[0110] The core 5G network architecture consists of modularized functions. For example, the AMF600 and SMF608 are independent functions within the CP. The isolated AMF600 and SMF608 allow for independent evolution and scaling. Other CP functions, such as the PCF610 and AUSF604, can be isolated as shown in Figure 8A. This modularized functional design enables the 5GC network to flexibly support a variety of services.

[0111] Each NF interacts directly with other NFs. Intermediate functions are used to route messages from one NF to another. In CP, a set of interactions between two NFs is defined as a service, making it reusable. This service enables support for modularity. UP supports interactions such as forwarding operations between different UPFs.

[0112] Referring now to Figure 8B, a block diagram of a 5G network architecture is shown that uses service-based interfaces between NFs within a CP instead of the point-to-point reference point / interface used in the 5G network architecture of Figure 8A. However, the NFs described above with reference to Figure 8B correspond to the NFs shown in Figure 8A. Services that an NF provides to other authorized NFs may be exposed to authorized NFs through service-based interfaces. In Figure 8B, service-based interfaces are indicated by the name of the NF followed by the letter "N", e.g., Namf for the service-based interface of AMF600 and Nsmf for the service-based interface of SMF608. NEF603 and NRF601 in Figure 8B are not shown in Figure 8A as described above. However, it should be made clear that all NFs shown in Figure 8A, although not explicitly shown in Figure 8A, can interact with NEF603 and NRF601 in Figure 8B as needed.

[0113] Some of the properties of the NF shown in Figures 8A and 8B can be described in the following way: The AMF600 provides UE-based authentication, authorization, and mobility management. Because the AMF6600 is independent of the access technology, the UE613 using multiplexing technology is also essentially connected to a single AMF600. The SMF608 is responsible for session management and assigns IP (Internet Protocol) addresses to the UE. It also selects and controls the UPF614 for data transfer. If the UE613 has multiple sessions, a different SMF608 may be assigned to each session to manage them individually and, in some cases, provide different functions for each session. The AF612 provides information about packet flow to the PCF610, which is responsible for policy control, in order to support QoS. Based on this information, the PCF610 determines policies regarding mobility and session management in order for the AMF600 and SMF608 to function properly. AUSF604 supports authentication functionality for UEs or similar devices and therefore stores data for UE authentication, while UDM606 stores subscriber data for UE613. DNs (Data Networks) that are not part of the 5GC network provide internet access or operator services, etc.

[0114] NF can be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an appropriate platform, such as a cloud infrastructure.

[0115] Figure 9 is a schematic block diagram of a radio access node 700 according to some embodiments of the present disclosure. Optional functions are represented by dashed boxes. The radio access node 700 may be, for example, a base station 102 or 106, or a network node implementing all or some of the functions of a base station 102 or gNB as described herein. As shown in the figure, the radio access node 700 includes a control system 702 which includes one or more processors 704 (e.g., a CPU (Central Processing Unit), an ASIC (Application-Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), etc.), a memory 706, and a network interface 708. One or more processors 704 are also referred to herein as processing circuits. Furthermore, the radio access node 700 may include one or more radio units 710, each including one or more transmitters 712 and one or more receivers 714 coupled to one or more antennas 716. The radio units 710 may be referred to as radio interface circuits, or parts thereof. In some embodiments, the wireless unit 710 is located outside the control system 702 and is connected to the control system 702, for example, via a wired connection (e.g., an optical cable). However, in some other embodiments, the wireless unit 710 and optionally the antenna 716 are integrated with the control system 702. One or more processors 704 operate to provide one or more functions of the wireless access node 700 described herein. In some embodiments, these functions are performed by software stored, for example, in memory 706 and executed by one or more processors 704.

[0116] Figure 10 is a schematic block diagram showing a virtualized embodiment of a wireless access node 700 according to several embodiments of the present disclosure. This description is similarly applicable to other types of network nodes. Furthermore, other types of network nodes may have similar virtualization architectures. In this case as well, optional features are represented by dashed boxes.

[0117] As used herein, a “virtualized” radio access node is an implementation of a radio access node 700 in which at least a portion of the functionality of the radio access node 700 is implemented as a virtual component (for example, via a virtual machine running on a physical processing node in the network). As illustrated, in this example, the radio access node 700 may include a control system 702 and / or one or more radio units 710, as described above. The control system 702 may be connected to the radio units 710, for example, via optical cables. The radio access node 700 includes one or more processing nodes 800 that are coupled to or included as part of a network 802. If present, the control system 702 or the radio units 710 are connected to the processing nodes 800 via the network 802. Each processing node 800 includes one or more processors 804 (e.g., a CPU, ASIC, FPGA, or similar, or a combination thereof), memory 806, and a network interface 808.

[0118] In this example, the functions 810 of the wireless access node 700 described herein are implemented in one or more processing nodes 800, or distributed across one or more processing nodes 800 and a control system 802 and / or wireless units 810 in any desired manner. In some particular embodiments, some or all of the functions 810 of the wireless access node 700 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment hosted by the processing node 800. As will be understood by those skilled in the art, additional signaling or communication between the processing node 800 and the control system 802 is used to perform at least some of the desired functions 810. In particular, in some embodiments, the control system 802 may not be included, in which case the wireless units 810 communicate directly with the processing node 800 via a suitable network interface.

[0119] In some embodiments, a computer program is provided that, when executed by at least one processor, causes at least one processor to perform functions of a wireless access node 700 or a node (e.g., a processing node 800) that implements one or more of the functions 810 of the wireless access node 700 in a virtual environment according to any of the embodiments described herein. In some embodiments, a carrier is provided which includes the aforementioned computer program product. The carrier is one of the following: an electronic signal, an optical signal, a wireless signal, or a computer-readable storage medium (e.g., a non-temporary computer-readable medium such as memory).

[0120] Figure 11 is a schematic block diagram of a wireless access node 700 according to some other embodiments of the present disclosure. The wireless access node 700 comprises one or more modules 800, each of which is implemented in software. The modules 800 provide the functionality of the wireless access node 700 as described herein. This description is equally applicable to the processing node 700 of Figure 10, where the modules 800 may be implemented in one of the processing nodes 700, or distributed across multiple processing nodes 700, and / or distributed across the processing nodes 700 and the control system 702.

[0121] Figure 12 is a schematic block diagram of a wireless communication device 900 according to some embodiments of the present disclosure. As shown, the wireless communication device 900 includes one or more processors 902 (e.g., a CPU, ASIC, FPGA, etc.), a memory 904, and one or more transceivers 906, each including one or more transmitters 908 and one or more receivers 910, each coupled to one or more antennas 912. The transceiver 906 includes a radio front-end circuit connected to the antenna 912, configured to coordinate signals communicated between the antenna 912 and the processor 902, as will be understood by those skilled in the art. The processor 902 is also referred to herein as a processing circuit. The transceiver 906 is also referred to herein as a radio circuit. In some embodiments, the functions of the wireless communication device 900 described above may be fully or partially implemented in software, for example, stored in the memory 904 and executed by the processor 902. It should be noted that the wireless communication device 900 may include additional components not shown in Figure 12, such as one or more user interface components (e.g., input / output interfaces including a display, buttons, touchscreen, microphone, speaker, etc., and / or any other components that enable the input of information to and / or the output of information from the wireless communication device 900), and a power supply (e.g., a battery and associated power circuitry).

[0122] In some embodiments, a computer program is provided which, when executed by at least one processor, causes at least one processor to perform the functions of a wireless communication device 900 according to any of the embodiments described herein. In some embodiments, a carrier is provided which includes the aforementioned computer program product. The carrier is one of the following: an electronic signal, an optical signal, a radio signal, or a computer-readable storage medium (e.g., a non-temporary computer-readable medium such as memory).

[0123] Figure 13 is a schematic block diagram of a wireless communication device 900 according to some other embodiments of the present disclosure. The wireless communication device 900 comprises one or more modules 1000, each of which is implemented in software. The modules 1000 provide the functions of the wireless communication device 900 as described herein.

[0124] Each station 1106A, 1106B, and 1106C can connect to the core network 1104 via a wired or wireless connection 1110. A first UE 1112 located within coverage area 1108C is configured to wirelessly connect to the corresponding base station 1106C or to be paged by the corresponding base station 110C. A second UE 1114 located within coverage area 1108A can wirelessly connect to the corresponding base station 1106A. Although multiple UEs 1112, 1114 are shown in this example, the disclosed embodiments are equally applicable to situations where only one UE is located within a coverage area, or where only one UE is connected to the corresponding base station 1106.

[0125] The telecommunications network 1100 is itself connected to a host computer 1116, which may be embodied in the hardware and / or software of a standalone server, a cloud implementation server, a distributed server, or as a processing resource within a server farm. The host computer 1116 may be owned or under the control of a service provider, or may be operated by or on behalf of a service provider. The connections 1118 and 1120 between the telecommunications network 1100 and the host computer 1116 may extend directly from the core network 1104 to the host computer 1116, or may proceed via an optional intermediate network 1122. The intermediate network 1122 may be one of the public network, a private network, or a hosted network, or a combination of two or more of these, and the intermediate network 1122 may be a backbone network or the internet, if any, and in particular may include two or more subnets (not shown).

[0126] The communication system in Figure 14, as a whole, enables a connection between connected UEs 1112, 1114 and the host computer 1116. The connection may be described as an OTT (over-the-top) connection 1124. The host computer 1116 and the connected UEs 1112, 1114 are configured to communicate data and / or signaling over the OTT connection 1124, using the access network 1102, the core network 1104, an optional intermediate network 1122, and possibly further infrastructure (not shown) as intermediaries. The OTT connection 1124 may be transparent in the sense that participating communication devices through which the OTT connection 1124 passes are unaware of the routing of uplink and downlink communications. For example, base station 1106 may not be, and may not need to be, notified of the past routing of incoming downlink communications that have data originating from host computer 1116 being forwarded (e.g., handed over) to connected UE 1112. Similarly, base station 1106 does not need to be aware of the future routing of outgoing uplink communications originating from UE 1112 to host computer 1116.

[0127] Any suitable step, method, feature, function, or benefit disclosed herein may be performed via one or more functional units or modules of one or more virtual devices. Each virtual device may comprise several of these functional units. These functional units may be implemented via processing circuits, which may include one or more microprocessors or microcontrollers, and other digital hardware, which may include DSPs (digital signal processors), dedicated digital logic, etc. The processing circuits may be configured to execute program code stored in memory, which may include one or more types of memory, such as ROM (read-only memory), RAM (random access memory), cache memory, flash memory devices, and optical storage devices. The program code stored in memory may include program instructions for executing one or more telecommunications and / or data communication protocols, and instructions for executing one or more of the techniques described herein. In some implementations, the processing circuits may be used to cause each functional unit to perform the corresponding function according to one or more embodiments of this disclosure.

[0128] The process shown in the figure may illustrate a specific sequence of operations performed by one embodiment of this disclosure, but it should be understood that such an order is illustrative (for example, alternative embodiments may perform operations in a different order, combine some operations, or overlap some operations).

[0129] In light of the above teachings, numerous modifications and variations of this disclosure are possible. Therefore, it should be understood that, within the scope of the appended claims, this disclosure may be implemented in ways other than those specifically described herein.

Claims

1. A method for execution by the first communication node of the target network, Maintaining a local cache to identify services known to be available to communication devices within the target network, During the handover procedure for the communication device from the initial network to the target, at least one service identifier is received from the second communication node, For each service identifier, if the service corresponding to the service identifier is not identified in the local cache, signaling is performed to the service repository of the target network; if the service is identified in the local cache, the signaling to the service repository is skipped. Methods that include...

2. The method according to claim 1, wherein the signaling to the service repository is skipped for a subset of the service identifiers.

3. The method according to claim 1, wherein the signaling to the service repository is skipped for all of the service identifiers.

4. The method according to any one of claims 1 to 3, wherein the at least one service identifier includes a UDM (Unified Data Management) group ID and / or a PCF (Policy Control Function) group ID.

5. The method according to claim 4, wherein the at least one service identifier includes the UDM group ID, and the service corresponding to the UDM group ID is a UDM UECM (Unified Endpoint Configuration Management) service or a UDM SDM (Subscriber Data Management) service, and skipping the signaling to the service repository includes skipping the discovery of the UDM UECM service or the UDM SDM service.

6. The method according to claim 4, wherein the at least one service identifier includes the PCF group ID, the service corresponding to the PCF group ID is a PCF AM (Access and Movement) policy service, and skipping the signaling to the service repository includes skipping the discovery of the PCF AM service.

7. The at least one service identifier includes the UDM group ID, and the service corresponding to the UDM group ID is a UDM UECM (Unified Endpoint Configuration Management) service or a UDM SDM (Subscriber Data Management) service, and skipping the signaling to the service repository includes skipping the discovery of the UDM UECM service or the UDM SDM service. The method according to claim 4, wherein the at least one service identifier includes the PCF group ID, the service corresponding to the PCF group ID is a PCF AM (Access and Movement) policy service, and skipping the signaling to the service repository includes skipping the discovery of the PCF AM service.

8. The method according to any one of claims 1 to 7, wherein the first communication node includes an AMF (Access and Mobility Management Function), the target network includes an NR (New 5G Radio) network, the initial network includes an LTE (Long-Term Evolution) network, and the service repository includes an NRF (Network Repository Function).

9. The method according to claim 8, wherein the second communication node includes an SMF (Session Management Function).

10. The method according to claim 8 or 9, wherein the second communication node includes an MME (Mobile Management Entity).

11. A non-temporary computer-readable medium on which statements and instructions are recorded, wherein, when the statements and instructions are executed by the processor of a first communication node, the first communication node is... Maintaining a local cache to identify services known to be available to communication devices within the target network, During the handover procedure for the communication device from the initial network to the target, at least one service identifier is received from the second communication node, For each service identifier, if the service corresponding to the service identifier is not identified in the local cache, signaling is performed to the service repository of the target network; if the service is identified in the local cache, the signaling to the service repository is skipped. A non-temporary computer-readable medium configured to perform this action.

12. The non-temporary computer-readable medium according to claim 11, wherein the statements and instructions, when executed by the processor of the first communication node, configure the first communication node to carry out the method according to any one of claims 2 to 10.

13. The first communication node of the target network, A network interface configured to communicate with other communication nodes, A computer-readable medium configured to maintain a local cache that identifies services known to be available to communication devices within the target network, A service discovery circuit coupled to the network interface and the computer-readable medium, wherein the service discovery circuit is During the handover procedure for the communication device from the initial network to the target, at least one service identifier is received from a second communication node via the network interface, For each service identifier, if the service corresponding to the service identifier is not identified in the local cache, signaling is performed to the service repository of the target network via the network interface; if the service is identified in the local cache, the signaling to the service repository is skipped. A service discovery circuit is configured to perform the following: A first communication node equipped with [a certain feature].

14. The first communication node according to claim 13, wherein the service discovery circuit is configured to skip the signaling to the service repository for a subset of the service identifiers.

15. The first communication node according to claim 13, wherein the service discovery circuit is configured to skip the signaling to the service repository for all of the service identifiers.

16. The first communication node according to any one of claims 13 to 15, wherein the at least one service identifier includes a UDM (Unified Data Management) group ID and / or a PCF (Policy Control Function) group ID.

17. The first communication node according to claim 16, wherein the at least one service identifier includes the UDM group ID, and the service corresponding to the UDM group ID is a UDM UECM (Unified Endpoint Configuration Management) service or a UDM SDM (Subscriber Data Management) service, and the first communication node skips the signaling to the service repository by skipping the discovery of the UDM UECM service or the UDM SDM service.

18. The first communication node according to claim 16, wherein the at least one service identifier includes the PCF group ID, the service corresponding to the PCF group ID is a PCF AM (Access and Movement) policy service, and the first communication node skips the signaling to the service repository by skipping the discovery of the PCF AM service.

19. The at least one service identifier includes the UDM group ID, and the service corresponding to the UDM group ID is either a UDM UECM (Unified Endpoint Configuration Management) service or a UDM SDM (Subscriber Data Management) service, and the first communication node skips the signaling to the service repository by skipping the discovery of the UDM UECM service or the UDM SDM service. The first communication node according to claim 16, wherein the at least one service identifier includes the PCF group ID, the service corresponding to the PCF group ID is a PCF AM (Access and Movement) policy service, and the first communication node skips the signaling to the service repository by skipping the discovery of the PCF AM service.

20. The first communication node according to any one of claims 13 to 19, wherein the first communication node includes an AMF (Access and Mobility Management Function), the target network includes an NR (New 5G Radio) network, the initial network includes an LTE (Long-Term Evolution) network, and the service repository includes an NRF (Network Repository Function).

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