Voice call processing method

Abstract

A 6G network node executes a voice call processing method The 6G network node determines whether a 6G radio access network (RAN) node supports an internet protocol multimedia subsystem (IMS) voice call. When the 6G RAN node supports an IMS voice call, the 6G network node performs an IMS voice call service to serve the call over 6G network. When the determining is negtive, the 6G RAN node determines whether a fifth generation (5G) network node supports Voice over New Radio (VoNR). When the 5G network node supports VoNR, the 6G network node performs VoNR to serve the call over 5G network. When the 5G network node does not support VoNR, the 6G network node initiates a handover or redirection of a user equipment (UE) for the IMS voice call from the 6G RAN node to a fourth generation (4G) network node for Voice over LTE (VoLTE) service.

Description

Atty. Dkt. No. 10085-01-0180-PCTVOICE CALL PROCESSING METHODCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 716,666, entitled “METHOD AND APPARATUS OF SUPPORTING IMS VOICE FALLBACK FROM 6G TO 4G,” filed on November 5, 2024, which is hereby incorporated in its entirety by this reference.BACKGROUND OF DISCLOSURE1. Field of Disclosure

[0002] The present disclosure relates to the field of communication systems, and more particularly, to a voice call processing method and a network node.2. Description of Related Art

[0003] Fifth-generation (5G) wireless systems support voice services primarily through Voice over New Radio (VoNR), where voice traffic is delivered natively on the 5G Core (5GC) network. VoNR operates exclusively in the 5G Standalone (SA) architecture, which mandates that the 5GC is deployed independently, without reliance on a legacy Long-Term Evolution (LTE) infrastructure. By managing both voice and data, the 5GC enables a seamless, all-5G experience. VoNR typically leverages the Enhanced Voice Services (EVS) codec, which offers superior audio quality and high- definition voice compared to the AMR-WB codec used in VoLTE.

[0004] Voice service has historically been a fundamental requirement for cellular networks across all generations, necessitating support from initial six generation (6G) network deployment. In fifthgeneration (5G) networks, voice services are implemented through two distinct methodologies: Voice over New Radio (VoNR) and Evolved Packet System (EPS) fallback.Technical Problem

[0005] During 6G development, a significant challenge arises when the 5G standalone network (including the 5GC or 5G RAN) does not support native VoNR.SUMMARY

[0006] An object of the present disclosure is to propose a voice call processing method and a network node.

[0007] In a first aspect, an embodiment of the invention provides a voice call processing method for execution by a six generation core network node, comprising: determining whether a 6G radio access network (RAN) node supports an internet protocol multimedia subsystem (IMS) voice call; determining whether a fifth generation (5G) network node supports Voice over New Radio (VoNR) when determining that the 6G RAN node does not support the IMS voice call; and initiating a handover or redirection of a user equipment (UE) for the IMS voice call from the 6G RAN node to a fourth generation (4G) network node for Voice over LTE (VoLTE) service when the 5G network node does not support VoNR.

[0008] In a second aspect, an embodiment of the invention provides a network node comprising a processor configured to call and run a computer program stored in a memory, to cause a device in which the processor is installed to execute the disclosed method.

[0009] The disclosed method may be programmed as computer executable instructions stored in non-transitory computer readable medium. The non-transitory computer readable medium, when loaded to a computer, directs a processor of the computer to execute the disclosed method.

[0010] The non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a FlashAtty. Dkt. No. 10085-01-0180-PCT memory.

[0011] The disclosed method may be programmed as a computer program product, that causes a computer to execute the disclosed method.

[0012] The disclosed method may be programmed as a computer program, that causes a computer to execute the disclosed method.Advantageous Effects

[0013] The disclosed voice call processing method achieves significant reduction in call setup latency by enabling direct 6G-to-4G handover when neither the 6G RAN nor the 5G network supports native voice services.

[0014] By implementing a capability determination mechanism where the 6G Core network proactively queries the VoNR support status of the 5G network before initiating any handover procedures, the invention eliminates the unnecessary dual-step handover process (6G to 5G to 4G) that would otherwise occur in conventional approaches.

[0015] This optimization substantially decreases call establishment time, particularly critical for emergency calls and time-sensitive communications. Furthermore, the method reduces network signaling overhead by avoiding futile PDU session establishment attempts and unnecessary inter- generational handovers, thereby conserving network resources and improving overall system efficiency. The transparent fallback mechanism ensures seamless voice service continuity for users across multiple cellular generations (6G, 5G, and 4G), maintaining high-quality voice communications through proven VoLTE technology when advanced voice services are unavailable.

[0016] Additionally, the event-driven and periodic capability reporting mechanisms enable dynamic network adaptation to changing voice service capabilities, allowing the system to automatically select the optimal voice service path based on real-time network conditions, ultimately enhancing user experience while minimizing service interruption during the transition period between cellular technology generations.BRIEF DESCRIPTION OF DRAWINGS

[0017] To clearly illustrate the embodiments of the present disclosure or related technical solutions, the accompanying drawings are briefly described below. These drawings represent embodiments of the present disclosure. A person of ordinary skill in the art may derive additional figures or variations based on these drawings without departing from the scope of the present disclosure.

[0018] FIG. 1 illustrates a schematic diagram showing a voice call processing method of an embodiment of the disclosure.

[0019] FIG. 2 illustrates a schematic diagram showing a 6G to 4G fallback procedure for mobile originated (MO) voice call.

[0020] FIG. 3 illustrates a schematic diagram showing a 5G network.

[0021] FIG. 4 illustrates a schematic diagram showing a 6G to 4G fallback procedure for mobile terminated (MT) voice call.

[0022] FIG. 5 illustrates a schematic view showing a user equipment (UE).

[0023] FIG. 6 illustrates a schematic view showing a base station.

[0024] FIG. 7 illustrates a schematic view showing a network node.

[0025] FIG. 8 illustrates a schematic view showing a chip or executing the disclosed method in a UE.

[0026] FIG. 9 illustrates a schematic view showing a chip or executing the disclosed method in a base station.

[0027] FIG. 10 illustrates a schematic view showing a chip or executing the disclosed method in a network node.

[0028] FIG. 11 illustrates a schematic view showing a system for wireless communication according to an embodiment of the present disclosure.Atty. Dkt. No. 10085-01-0180-PCTDETAILED DESCRIPTION OF EMBODIMENTS

[0029] Embodiments of the disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the disclosure.

[0030] A significant challenge arises when the 5G Standalone (SA) network (including the 5GC or 5G RAN) lacks native VoNR support. In this scenario, EPS fallback is utilized to provide voice service for 5G users. This mechanism functions as a temporary measure where a voice call initiated in 5G reverts to the LTE network for completion. EPS fallback is crucial during early 5G SA deployments, as it ensures uninterrupted voice quality by leveraging the established and reliable LTE infrastructure.

[0031] The EPS fallback process is managed entirely by the network and is transparent to the User Equipment (UE). Upon initiation of a voice call, the network checks the VoNR support capability of the 5GC or 5G radio access network (RAN). If VoNR is not supported, the network initiates a handover procedure to move the UE to LTE. Once the UE is attached to the LTE network, the call is managed as a standard VoLTE call, utilizing LTE resources to maintain voice quality. This mechanism is vital, particularly in early 5G Standalone (SA) deployments, as it leverages the widely established and reliable LTE network to ensure uninterrupted voice service.

[0032] Since LTE networks are widely established and reliable for voice services, EPS Fallback ensures uninterrupted voice quality by leveraging LTE resources when the 5G network is not ready to handle voice calls natively. This mechanism is managed entirely by the network and is transparent to the User Equipment (UE). Specifically, when a voice call is initiated on a 5G device in a Standalone (SA) network, the network first checks the VoNR support capability of the 5GC or 5G RAN. If VoNR is not supported, the network initiates a handover procedure to switch the UE to LTE. Once in LTE, the call, along with any concurrent data call, is managed as a standard VoLTE call, utilizing LTE resources to maintain quality.

[0033] Previous proposals, such as the two referenced prior arts concerning UE-triggered voice service selection in 6G and voice service fallback from 6G to 5G, have addressed voice call support between 5G and 6G. However, these solutions fail to account for the sustained importance of the 4G network. Given the enduring reliability and widespread deployment of 4G, it is highly likely to remain in service even when 6G becomes available in most regions. Therefore, a critical need exists to efficiently integrate the 4G network with 6G to provide seamless voice services to users.

[0034] In current network designs, if the 6G system attempts to transfer the UE to the 5G network for voice service, it first communicates with the 5G network to check for VoNR support. If the 5G network is determined not to support VoNR, the conventional approach would require the UE to first perform a handover to 5G, and subsequently execute an EPS fallback handover from 5G to 4G to complete the voice call. This multi-step process significantly increases the call setup delay.

[0035] While VoNR provides superior audio quality (often using the EVS codec) and a pure 5G experience, its reliance on a fully deployed 5G Standalone (SA) architecture often necessitates EPS fallback to the reliable 4G network when native 5G voice support is unavailable. As wireless technology transitions toward 6G, the challenge shifts: future voice services must not only maintain high quality but also seamlessly integrate the capabilities of both 5G and 4G for continuity, requiring robust and efficient IMS voice fallback mechanisms to manage complex inter-generational voice traffic.

[0036] An embodiment of the disclosure is to enable the 6G Core (6GC) to determine the VoNR capability of the 5G network before initiating any handover procedure. This allows the 6G system to directly initiate a handover from 6G to 4G if 5G VoNR is unsupported, thus bypassing the unnecessary 6G-to-5G transition and 5G-to-4G transition.

[0037] The disclosed method comprises1. The 5G Core network obtains a VoNR capability report from the 5G RAN. This report can be event-driven (e.g., when 5G RAN capability changes) or periodic.Atty. Dkt. No. 10085-01-0180-PCT2. The 6G Core network is configured to check this reported VoNR capability of the 5G network.

[0038] Network Entities in 6G, 5G, and 4G Core Networks:

[0039] The fallback may involve network nodes in 6G, 5G, and 4G RAN and core networks. Network nodes in 6G, 5G, and 4G core networks are briefly explained in the following..

[0040] 4G Core Network Architecture (Evolved Packet Core - EPC):

[0041] The fourth-generation core network, known as the Evolved Packet Core (EPC), comprises several key network entities that facilitate packet-switched services and voice communications. The Mobility Management Entity (MME) serves as the primary control plane entity, responsible for user authentication, mobility management, bearer management, and tracking area update procedures. The Serving Gateway (S-GW) functions as the local mobility anchor for inter-eNodeB handovers and routes user data packets between the radio access network and the packet data network. The Packet Data Network Gateway (P-GW) provides connectivity to external packet data networks, assigns IP addresses to user equipment, and enforces quality of service policies. The Home Subscriber Server (HSS) maintains the central database containing user subscription information, authentication credentials, and service profiles. For voice services, the IP Multimedia Subsystem (IMS) framework, including the Proxy Call Session Control Function (P-CSCF), Interrogating-CSCF (I-CSCF), and Serving-CSCF (S-CSCF), enables Voice over LTE (VoLTE) capabilities through Session Initiation Protocol (SIP) signaling. The Policy and Charging Rules Function (PCRF) determines policy rules and performs flow-based charging functions, while the evolved NodeB (eNB) serves as the base station providing radio interface connectivity to user equipment.

[0042] 5G Core Network Architecture (5GC):

[0043] The fifth-generation core network (5GC) introduces a service-based architecture with network functions that communicate through standardized interfaces. The Access and Mobility Management Function (AMF) handles connection and mobility management tasks, including registration, connection management, reachability management, and mobility management for user equipment. The Session Management Function (SMF) manages protocol data unit (PDU) sessions, including session establishment, modification, and release, while also handling IP address allocation and traffic steering policies. The User Plane Function (UPF) serves as the anchor point for intra- and inter-Radio Access Technology (RAT) mobility, routes and forwards user data packets, performs packet inspection, and enforces quality of service policies at the user plane level. The Unified Data Management (UDM) function stores subscriber data and profiles, generating authentication credentials and managing subscription information analogous to the HSS in 4G networks. The Authentication Server Function (AUSF) performs authentication procedures for 3 GPP and non-3GPP access networks. The Network Slice Selection Function (NSSF) facilitates network slicing by selecting appropriate network slice instances for user equipment based on subscription and local policies. The Policy Control Function (PCF) provides unified policy framework governing network behavior, including quality of service policies, spending limits, and access control. The Network Exposure Function (NEF) securely exposes network capabilities and events to third-party applications and services. The Network Repository Function (NRF) maintains a repository of available network function instances and their supported services, enabling dynamic service discovery. The Application Function (AF) interacts with the 5G core network to provide application services, particularly for IMS-based voice services where it interfaces with the PCF for policy control. For Voice over New Radio (VoNR) support, the IMS infrastructure integrates with the 5GC through the PCF and UPF to enable native voice services over 5G networks.

[0044] 6G Core Network Architecture:

[0045] The sixth-generation core network architecture, while still under development and standardization, may build upon the service-based architecture of 5G while introducing enhanced capabilities for ultra-reliable low-latency communications, artificial intelligence integration, and advanced network orchestration. The 6G Core (6GC) is expected to retain evolved versions ofAtty. Dkt. No. 10085-01-0180-PCT essential network functions from 5G, including enhanced mobility management functions, session management capabilities, and user plane functions optimized for terahertz communications and holographic services. New network functions specific to 6G are anticipated to include Al-driven network intelligence functions for predictive resource allocation and autonomous network optimization, distributed computing functions that integrate edge and cloud computing resources seamlessly, and enhanced security functions supporting quantum-resistant cryptography. The 6GC architecture is expected to feature native support for network sensing capabilities, enabling the network infrastructure to function as a distributed sensor system. Integration functions for satellite and terrestrial networks are anticipated to provide truly ubiquitous connectivity. The 6G Radio Access Network (6G RAN) will interface with the 6GC through next-generation protocols supporting extreme data rates and ultra-low latency requirements. For voice services, the 6GC must maintain backward compatibility with existing IMS infrastructure while potentially introducing new voice service paradigms such as holographic communications. Interworking functions between 6GC and legacy core networks (5GC and EPC) will be essential for ensuring service continuity during the transition period, particularly for critical services such as voice communications. The 6GC architecture must incorporate intelligent decision-making capabilities to determine optimal service delivery paths, whether through native 6G capabilities, 5G VoNR, or 4G VoLTE, based on network conditions, device capabilities, and service requirements.

[0046] IMS Voice Services Across Cellular Generations:

[0047] IP Multimedia Subsystem (IMS) is the foundational architecture for delivering voice and multimedia services in modem cellular networks, ensuring that voice traffic is treated as IMS voice traffic carried over an all-internet protocol (IP) data bearer. In 4G (LTE) networks, this architecture enables Voice over LTE (VoLTE), which routes voice calls over the robust LTE data plane via the Evolved Packet Core (EPC). Building on this, 5G New Radio (NR) introduced Voice over New Radio (VoNR), delivering voice natively on the 5G Core (5GC). Similarly, IMS voice service that may be developed in 6G to support IMS voice traffic for IMS voice call, delivering voice natively on the 6G core network. The IMS voice service introduced to 6G may reuse VoNR or evolve to voice over 6G, which may be referred to as Vo6G in the description.

[0048] An example of the UE in the description may include UE 10 as shown in FIG. 5. An example of a RAN (e.g., one or more base stations) in the description may include one or more base stations 20 as shown in FIG. 6. An example of a core network in the description may include one or more network nodes executed by one or more network devices 30 as shown in FIG. 7.

[0049] In the FIG. 1, a 6G network node (e.g., 6G Core 30c shown in FIG. 2 and FIG. 4) executes an embodiment of a voice call processing method. The disclosed voice call processing method achieves significant reduction in call setup latency by enabling direct 6G-to-4G handover when neither the 6G RAN nor the 5G network supports native voice services (e.g., IMS voice call).

[0050] Step S001 : The 6G network node determines whether a 6G radio access network (RAN) node (e.g., 6G RAN 20c shown in FIG. 2 and FIG. 4) supports an internet protocol multimedia subsystem (IMS) voice call.

[0051] Step S002: When the 6G RAN node supports an IMS voice call, the 6G network node performs an IMS voice call service to serve the call over 6G network. The IMS voice call service over 6G network may comprise signaling between 6G network nodes (e.g., UE 10, 6G Core 30c, 6G RAN 20c shown in FIG. 2 and FIG. 4) for initiating, maintaining, and terminating the call and routing of voice data traffic for the call.

[0052] Step S003 : When determining that the 6G RAN node does not support the IMS voice call, the 6G RAN node determines whether a fifth generation (5G) network node (e.g., 5G network 30b shown in FIG. 2 and FIG. 4) supports Voice over New Radio (VoNR).

[0053] Step S004: When the 5G network node supports VoNR, the 6G network node performs VoNR to serve the call over the 5G network (e.g., 5G network 30b shown in FIG. 2 and FIG. 4).

[0054] Step S005: When the 5G network node does not support VoNR, the 6G network node initiates a handover or redirection of a user equipment (UE) (e.g., UE 10 shown in FIG. 2 and FIG. 4) for the IMS voice call from the 6G RAN node to a fourth generation (4G) network node (e.g.,Atty. Dkt. No. 10085-01-0180-PCTEPC 30a and / or 4G RAN 20a shown in FIG. 2 and FIG. 4) for Voice over LTE (VoLTE) service.

[0055] In one or more embodiments of the disclosure, the 6G network node receives, from the 5G network node, an indication whether the 5G network node supports VoNR.

[0056] In one or more embodiments of the disclosure, the 6G network node and / or a 5G core network node (e.g., 5G core 3 lb shown in FIG. 3) determines whether the 5G network node (e.g., 5G network 30b shown in FIG. 2 and FIG. 4) supports VoNR based on a capability report received from a 5GRAN node (e.g., 5GRAN 20b shown in FIG. 3). For example, the capability report may be an event-driven report triggered when a VoNR support status changes in the 5G RAN node. Alternatively, the capability report is reported based on periodic reporting.

[0057] In one or more embodiments of the disclosure, the 6G core network node receives, from the 6G RAN node, a capability report indicating that the 6G RAN node does not support the IMS voice call. The whether the 6G RAN node supports the IMS voice call is determined based on the capability report from the 6G RAN node. The determining whether the 6G RAN node supports the IMS voice call comprises: determining voice support capability of the 6G RAN node based on a capability report received from the 6G RAN node.

[0058] For example, the capability report may be an event-driven report triggered when a support status of the IMS voice call changes in the 6G RAN node. Alternatively, the capability report is reported based on periodic reporting.

[0059] In one or more embodiments of the disclosure, initiating the handover or redirection comprises: performing a 6G-4G inter-RAT (Radio Access Technology) mobility procedure from the 6G RAN node to the 4G network node.

[0060] In one or more embodiments of the disclosure, the voice call is a mobile originated (MO) call, and the method further comprises: receiving a request from the UE to establish an IMS PDU session for IMS voice traffic of the voice call; and rejecting the request before determining whether the 5G network node supports VoNR.

[0061] In one or more embodiments of the disclosure, the voice call is a mobile terminated (MT) call, and the method further comprises: receiving an MT call indication from an IMS server (e.g., IMS server 40 shown in FIG. 2 and FIG. 4); and determining whether the 5G network node supports VoNR before sending a paging message to the UE for establishing an IMS PDU session.

[0062] In one or more embodiments of the disclosure, the 6G core network node establishes an IMS PDU session for IMS signaling between the UE and an IMS server (e.g., IMS server 40 shown in FIG. 2 and FIG. 4) prior to determining whether the 6G RAN supports the IMS voice call. After the handover or the redirection, the 4G network node (e.g., EPC 30a and / or 4G RAN 20a shown in FIG. 2 and FIG. 4) establishes an Evolved Packet System (EPS) bearer in the 4G network (e.g., EPC 30a and 4G RAN 20a shown in FIG. 2 and FIG. 4) for the IMS voice call. After the handover or the redirection, a tracking area update (TAU) procedure is performed for the UE in the 4G network.

[0063] Embodiments of the disclosure are illustrated in the following with respect to mobile originated (MO) voice call and mobile terminated (MT) voice call respectively.

[0064] Mobile originated (MO) voice call:

[0065] With reference to FIG. 2, for mobile originated (MO) voice call, a 6G to 4G fallback procedure in an embodiment of the disclosure is detailed in the following.

[0066] The fallback procedure comprises the following steps:

[0067] In step 1, the 6G RAN 20c registers its voice support capability with the 6G Core 30c. In some embodiments of the disclosure, 6G RAN 20c autonomously reports its voice support capability to the 6G Core 30c, for example, by sending a capability report that conveys the voice support capability. The capability report can be an event-driven report triggered when a supportAtty. Dkt. No. 10085-01-0180-PCT status of the IMS voice call changes in the 6G RAN node. Alternatively, the capability report is reported based on periodic reporting. In embodiments where the 6G RAN 20c does not initially report its voice support capability (e.g., Vo6G, enhanced or evolved version nof VoNR, or reuse of Voice over New Radio (VoNR) capability in 6G network), the 6G Core 30c may query this information during subsequent steps of the procedure. The 6G RAN 20c sends its voice support capability to the 6G Core 30c in response to the query. The voice supports capability indicates whether the 6G RAN 20c supports IMS voice call and IMS voice traffic.

[0068] In step 2, the UE 10 initiates and performs a registration procedure with the 6G Core 30c through the 6G RAN 20c.

[0069] In step 3, the 6G Core 30c completes the registration process for the UE 10, establishing the UE's presence in the 6G network.

[0070] In step 4, an IMS Protocol Data Unit (PDU) session dedicated to IMS voice signaling is established to facilitate the transfer of IMS signaling messages between the UE 10 and the network infrastructure. While the 6G RAN 20c may lack support for IMS voice traffic, this IMS signaling PDU session remains essential for conveying initial IMS signaling between the UE 10 and an IMS server 40.

[0071] In step 5, a mobile originated voice call is initiated by the UE 10.

[0072] In step 6, the UE 10 exchanges IMS signaling with the IMS server 40 through the 6G Core 30c in an attempt to establish a protocol data unit (PDU) session for IMS voice traffic transmission.

[0073] In step 7, the 6G Core 30c determines whether the 6G RAN 20c supports IMS voice traffic or not. The 6G Core 30c, when determining that the 6G RAN 20c does not support IMS voice traffic, consequently rejects the PDU session establishment request. In embodiments where the 6G RAN 20c has not previously reported its voice support capability in step 1, the 6G Core 30c queries the voice support capability from the 6G RAN 20c at this stage. The 6G RAN 20c sends its voice support capability to the 6G Core 30c in response to the query.

[0074] In step 8, prior to initiating a transfer ofthe UE 10 to the 5G network 30b for voice service, the 6G Core 30c determines a VoNR capability of the 5G network 30b. The VoNR capability is a voice support capability of the 5G network 30b and indicates whether the 5G network 30b supports IMS voice call and IMS voice traffic (i.e., VoNR). With reference to FIG. 3, the 5G network 30b may comprise a 5GC 31b and a 5G RAN 20b. In one implementation, the 5G network 30b determines VoNR capability through capability reporting from its 5G RAN to its 5G core network. Such capability reporting may be configured as event-driven (triggered when VoNR support status changes) or periodic (occurring at predetermined intervals). In some embodiments of the disclosure, the 5G network 30b (e.g., 5G core 31b and / or 5G RAN 20b shown in FIG. 3) autonomously reports its voice support capability to the 6G Core 30c, for example, by sending a capability report that conveys the voice support capability. The capability report can be an event- driven report triggered when a support status of the IMS voice call changes in the 5G network 30b. Alternatively, the capability report is reported based on periodic reporting. Alternatively, the the 6G Core 30c queries the 5G network 30b regarding its VoNR capability status. The 5G network 30b sends its voice support capability to the 6G Core 30c in response to the query.

[0075] In step 9, the 5G network 30b, having determined that its 5G RAN does not support VoNR, reports to the 6G Core 30c that VoNR is not supported on the 5G network 30b.

[0076] In step 10, based on the determination that neither the 6G RAN 20c nor the 5G network 30b supports the required voice services, the 6G Core 30c transmits a handover request to the 6G RAN 20c to initiate a direct handover from 6G to 4G, thereby bypassing an intermediate 5G transition.

[0077] In step 11, the 6G Core 30c, the 6G RAN 20c, the EPC 30a, and the 4G RAN 20a coordinate to execute the handover procedure transferring the UE 10 from 6G to 4G. This step encompasses various mobility options including direct handover or redirection mechanisms. The specific implementation details of the 6G-4G inter-RAT (Radio Access Technology) mobility procedures may utilize conventional techniques known in the art.Atty. Dkt. No. 10085-01-0180-PCT

[0078] In step 12, following successful transfer to the 4G network, the UE 10 performs a Tracking Area Update (TAU) procedure with the EPC 30a through the 4G RAN 20a.

[0079] In step 13, the UE 10 establishes an EPS bearer through the 4G RAN 20a for IMS voice call support and initiates the voice call using VoLTE (Voice over LTE) technology.

[0080] Mobile terminated (MT) voice call:

[0081] With reference to FIG. 4, for mobile terminated (MT) voice call, a 6G to 4G fallback procedure in an embodiment of the disclosure is detailed in the following.

[0082] The MT voice call fallback procedure substantially parallels the MO voice call procedure described above, with a key distinction occurring after step 5. In the MT call scenario, when the 6G Core 30c receives notification of an incoming voice call for the UE 10, it recognizes that the 6GRAN 20c does not support voice calls. Consequently, rather than transmitting a paging message to the UE 10 requesting establishment of an IMS PDU session (which would be unsuccessful), the 6G Core 30c proceeds directly to query the 5G network 30b regarding its VoNR support capability. This optimization reduces call setup latency by eliminating unnecessary signaling attempts with the UE 10 when the outcome is predetermined based on the 6G RAN's capabilities.

[0083] Following the VoNR capability inquiry, the MT call procedure continues with steps analogous to steps 9-13 of the MO call procedure, ultimately resulting in the UE 10 being transferred to the 4G network where the incoming voice call is completed using VoLTE technology through the 4G RAN 20a and EPC 30a.

[0084] The fallback procedure comprises the following steps:

[0085] In step 1, the 6G RAN 20c registers its voice support capability with the 6G Core 30c. In some embodiments of the disclosure, 6G RAN 20c autonomously reports its voice support capability to the 6G Core 30c, for example, by sending a capability report that conveys the voice support capability. The capability report can be an event-driven report triggered when a support status of the IMS voice call changes in the 6G RAN node. Alternatively, the capability report is reported based on periodic reporting. In embodiments where the 6G RAN 20c does not initially voice support capability (e.g., Vo6G or reuse of Voice over New Radio (VoNR) capability in 6G network), the 6G Core 30c may query this information during subsequent steps of the procedure. The 6G RAN 20c sends its voice support capability to the 6G Core 30c in response to the query. The voice supports capability indicates whether the 6GRAN 20c supports IMS voice call and IMS voice traffic.

[0086] In step 2, the UE 10 initiates and performs a registration procedure with the 6G Core 30c through the 6G RAN 20c.

[0087] In step 3, the 6G Core 30c completes the registration process for the UE 10, establishing the UE's presence in the 6G network.

[0088] In step 4, an IMS Protocol Data Unit (PDU) session dedicated to IMS voice signaling is established to facilitate the transfer of IMS signaling messages between the UE 10 and the network infrastructure. While the 6G RAN 20c may lack support for IMS voice traffic, this IMS signaling PDU session remains essential for conveying initial IMS signaling between the UE 10 and an IMS server 40.

[0089] In step 5, the 6G Core 30c receives notification of an incoming voice call for the UE 10.

[0090] In step 6, the 6G Core 30c determines whether the 6GRAN 20c supports IMS voice traffic or not. When determining that the 6G RAN 20c does not support IMS voice traffic: rather than transmitting a paging message to the UE 10 requesting establishment of an IMS PDU session (which would be unsuccessful), the 6G Core 30c proceeds directly to determine a VoNR capability of the 5G network 20c in step 7.In embodiments where the 6G RAN 20c has not previously reported its voice support capability in step 1, the 6G Core 30c queries the voice support capability from the 6G RAN 20c at this stage. The 6G RAN 20c sends its voice support capability to the 6G Core 30c in response to the query.

[0091] In step 7, prior to initiating a transfer of the UE 10 to the 5G network 30b for voice service, the 6G Core 30c determines a VoNR capability of the 5G network 30b. The VoNR capability is a voice support capability of the 5G network 30b and indicates whether the 5G network 30b supportsAtty. Dkt. No. 10085-01-0180-PCTIMS voice call and IMS voice traffic (i.e., VoNR). With reference to FIG. 3, the 5G network 30b may comprise a 5GC 31b and a 5G RAN 20b. In one implementation, the 5G network 30b determines VoNR capability through capability reporting from its 5G RAN to its 5G core network. Such capability reporting may be configured as event-driven (triggered when VoNR support status changes) or periodic (occurring at predetermined intervals). In some embodiments of the disclosure, the 5G network 30b (e.g., 5G core 31b and / or 5G RAN 20b shown in FIG. 3) autonomously reports its voice support capability to the 6G Core 30c, for example, by sending a capability report that conveys the voice support capability. The capability report can be an event- driven report triggered when a support status of the IMS voice call changes in the 5G network 30b. Alternatively, the capability report is reported based on periodic reporting. Alternatively, the the 6G Core 30c queries the 5G network 30b regarding its VoNR capability status. The 5G network 30b sends its voice support capability to the 6G Core 30c in response to the query.

[0092] In step 8, the 5G network 30b, having determined that its 5G RAN does not support VoNR, reports to the 6G Core 30c that VoNR is not supported on the 5G network 30b.

[0093] In step 9, based on the determination that neither the 6G RAN 20c nor the 5G network 30b supports the required voice services, the 6G Core 30c transmits a handover request to the 6G RAN 20c to initiate a direct handover from 6G to 4G, thereby bypassing an intermediate 5G transition.

[0094] In step 10, the 6G Core 30c, the 6G RAN 20c, the EPC 30a, and the 4G RAN 20a coordinate to execute the handover procedure transferring the UE 10 from 6G to 4G. This step encompasses various mobility options including direct handover or redirection mechanisms. The specific implementation details of the 6G-4G inter-RAT (Radio Access Technology) mobility procedures may utilize conventional techniques known in the art.

[0095] In step 11 , following successful transfer to the 4G network, the UE 10 performs a Tracking Area Update (TAU) procedure with the EPC 30a through the 4G RAN 20a.

[0096] In step 12, the UE 10 establishes an EPS bearer through the 4G RAN 20a for IMS voice call support and initiates the voice call using VoLTE (Voice over LTE) technology.

[0097] With reference to FIG. 5, the UE 10 may include a processor Ila, a memory 12a, and a transceiver 13a. The processor Ila is configured to call and run a computer program stored in the memory 12a, to cause UE 10 in which the processor Ila is installed to execute the disclosed method, steps, and / or functions of a UE. The UE 10 is an example of the UE in the description. The transceiver 13a may include baseband circuitry and radio frequency (RF) circuitry.

[0098] With reference to FIG. 6, the base station 20 is a network device and may include a processor 21a, a memory 22a, and a transceiver 23a. The processor 21a is configured to call and run a computer program stored in the memory 22a, to cause base station 20 in which the processor 21a is installed to execute the method, steps, and / or functions of a RAN, such as a base station, including 4G RAN 20a, 5G RAN 20b, and / or 6G RAN 20c. The eNB, ng-eNB, and gNB are examples of the base station in the description. The base station can have a functional split configuration such that a first portion of the base station (referred to as onboard eNB, ng-eNB, and gNB) is installed in an NTN device, such as a satellite, and a second portion of the base station (referred to as on-ground eNB, ng-eNB, and gNB) is installed in a terrestrial network (TN) device. The transceiver 23 a, may include baseband circuitry and radio frequency (RF) circuitry.

[0099] With reference to FIG. 7, the network device 30 may be a core network device and may include a processor 3 la, a memory 32a, and a transceiver 33a. The processor 3 la is configured to call and run a computer program stored in the memory 32a, to cause network node 30 in which the processor 31a is installed to execute the method, steps, and / or functions of a network device. The EPC 30a, 5G Core 31b, 6G Core 30c, IMS server 40, and other network devices are examples of the network device in the description. The network device can have a functional split configuration such that a first portion of the network device (referred to as onboard core network device, such as MME-onboard) is installed in an NTN device, such as a satellite, and a second portion of the network device (referred to as on-ground core network device, such as MME-ground) is installed in a terrestrial network (TN) device. The transceiver 33a, may include baseband circuitry and radioAtty. Dkt. No. 10085-01-0180-PCT frequency (RF) circuitry.

[0100] With reference to FIG. 8, the embodiment of the disclosure also provides a chip 70 that may correspond to a UE in the embodiments of the disclosure. The chip 70 may implement a corresponding process realized by the UE in various methods of the embodiments of the disclosure. The chip 70 includes a processor 71, and the processor 71 may call and run a computer program from memory to implement the methods in the embodiments of the present application.

[0101] Optionally, the chip 70 may also include a memory 72. In particular, the processor 71 may call and run the computer program from the memory 72 to implement the methods in the embodiments of the present application.

[0102] Moreover, the memory 72 may be a separate device from the processor 71 or may be integrated into the processor 71.

[0103] Optionally, the chip 70 may include an input interface 73. Note that the processor 71 may control the input interface 73 to communicate with other devices or chips, specifically, to obtain messages or data sent by other devices or chips.

[0104] Optionally, the chip 70 may further include an output interface 74. Note that the processor 71 may control the output interface 74 to communicate with other devices or chips, specifically, to output messages or data to other devices or chips.

[0105] With reference to FIG. 9, the embodiment of the disclosure also provides another chip 80 that may correspond to a RAN in the description, and the chip 80 may implement the corresponding processes implemented by the base station in the various methods of the embodiments of the disclosure. The chip 80 includes a processor 81, and the processor 81 may call and run a computer program from the memory 82 to implement the methods in the embodiments of the present application.

[0106] Optionally, the chip 80 may further include a memory 82. In particular, the processor 81 may call and run the computer program from the memory 82 to implement the methods in the embodiments of the present application.

[0107] Wherein the memory 82 may be a separate device from the processor 81 or may be integrated into the processor 81.

[0108] Optionally, the chip 80 may also include an input interface 83. In particular, the processor 81 may control the input interface 83 to communicate with other devices or chips, specifically, to obtain messages or data sent by other devices or chips.

[0109] Optionally, the chip may further include an output interface 84. In particular, the processor 81 may control the output interface 84 to communicate with other devices or chips, specifically, to output messages or data to other devices or chips.

[0110] With reference to FIG. 10, the embodiment of the disclosure also provides another chip90 that may correspond to a network device (e.g., EPC 30a, 5G Core 3 lb, 6G Core 30c, IMS server 40, RAN) in the description, and the chip 90 may implement the corresponding processes implemented by the base station in the various methods of the embodiments of the disclosure. The chip 90 includes a processor 91, and the processor 91 may call and run a computer program from the memory 92 to implement the methods in the embodiments of the present application.

[0111] Optionally, the chip 90 may further include a memory 92. In particular, the processor 91 may call and run the computer program from the memory 92 to implement the methods in the embodiments of the present application.

[0112] Wherein the memory 92 may be a separate device from the processor 91 or may be integrated into the processor 91.

[0113] Optionally, the chip 90 may also include an input interface 93. In particular, the processor91 may control the input interface 93 to communicate with other devices or chips, specifically, to obtain messages or data sent by other devices or chips.

[0114] Optionally, the chip may further include an output interface 94. In particular, the processor 91 may control the output interface 94 to communicate with other devices or chips, specifically, to output messages or data to other devices or chips.

[0115] The embodiment of the present disclosure is a combination of techniques / processes thatAtty. Dkt. No. 10085-01-0180-PCT may be adopted in 3 GPP specification to create an end product.

[0116] FIG. 11 is a block diagram of an example system 700 for wireless communication according to an embodiment of the present disclosure. Embodiments described herein may be implemented into the system using any suitably configured hardware and / or software. FIG. 11 illustrates the system 700 including a radio frequency (RF) circuitry 710, a baseband circuitry 720, a processing unit 730, a memory / storage 740, a display 750, a camera 760, a sensor 770, and an input / output (VO) interface 780, coupled with each other as illustrated.

[0117] The processing unit 730 may include circuitry, such as, but not limited to, one or more single-core or multi-core processors. The processors may include any combinations of general- purpose processors and dedicated processors, such as graphics processors and application processors. The processors may be coupled with the memory / storage and configured to execute instructions stored in the memory / storage to enable various applications and / or operating systems running on the system.

[0118] The baseband circuitry 720 may include circuitry, such as, but not limited to, one or more single-core or multi-core processors. The processors may include a baseband processor. The baseband circuitry may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, etc. In some embodiments, the baseband circuitry may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry may support communication with 5GNR, LTE, an evolved universal terrestrial radio access network (EUTRAN) and / or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry. In various embodiments, the baseband circuitry 720 may include circuitry to operate with signals that are not strictly considered as being in a baseband frequency. For example, in some embodiments, baseband circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.

[0119] The RF circuitry 710 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry may include switches, filters, amplifiers, etc. to facilitate communication with the wireless network. In various embodiments, the RF circuitry 710 may include circuitry to operate with signals that are not strictly considered as being in a radio frequency. For example, in some embodiments, RF circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.

[0120] In various embodiments, the transmitter circuitry, control circuitry, or receiver circuitry discussed above with respect to the UE, eNB, or gNB may be embodied in whole or in part in one or more of the RF circuitries, the baseband circuitry, and / or the processing unit. As used herein, “circuitry” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and / or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and / or other suitable hardware components that provide the described functionality. In some embodiments, the electronic device circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, some or all of the constituent components of the baseband circuitry, the processing unit, and / or the memory / storage may be implemented together on a system on a chip (SOC).

[0121] The memory / storage 740 may be used to load and store data and / or instructions, for example, for the system. The memory / storage for one embodiment may include any combination of suitable volatile memory, such as dynamic random access memory (DRAM)), and / or nonvolatile memory, such as flash memory. In various embodiments, the VO interface 780 may include one or more user interfaces designed to enable user interaction with the system and / or peripheralAtty. Dkt. No. 10085-01-0180-PCT component interfaces designed to enable peripheral component interaction with the system. User interfaces may include, but are not limited to a physical keyboard or keypad, a touchpad, a speaker, a microphone, etc. Peripheral component interfaces may include, but are not limited to, a nonvolatile memory port, auniversal serial bus (USB) port, an audio jack, and a power supply interface.

[0122] In various embodiments, the sensor 770 may include one or more sensing devices to determine environmental conditions and / or location information related to the system. In some embodiments, the sensors may include, but are not limited to, a gyro sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may also be part of, or interact with, the baseband circuitry and / or RF circuitry to communicate with components of a positioning network, e.g., a global positioning system (GPS) satellite. In various embodiments, the display 750 may include a display, such as a liquid crystal display and a touch screen display. In various embodiments, the system 700 may be a mobile computing device such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an Ultrabook, a smartphone, etc. In various embodiments, the system may have more or less components, and / or different architectures. Where appropriate, the methods described herein may be implemented as a computer program. The computer program may be stored on a storage medium, such as a non-transitory storage medium.

[0123] The embodiment of the present disclosure is a combination of techniques / processes that may be adopted in 3 GPP specification to create an end product.

[0124] A person having ordinary skill in the art understands that each of the units, algorithm, and steps described and disclosed in the embodiments of the present disclosure are realized using electronic hardware or combinations of software for computers and electronic hardware. Whether the functions run in hardware or software depends on the condition of the application and design requirement for a technical plan. A person who has ordinary skill in the art may use different ways to realize the function for each specific application while such realizations should not go beyond the scope of the present disclosure. It is understood by a person having ordinary skill in the art that he / she may refer to the working processes of the system, device, and unit in the above-mentioned embodiment since the working processes of the above-mentioned system, device, and unit are basically the same. For easy description and simplicity, these working processes will not be detailed.

[0125] It is to be understood that the systems, devices, and methods disclosed in the embodiments of the present disclosure may be implemented in alternative configurations. The embodiments described are illustrative and not restrictive. The division of functional units is based on logical functions, and alternative divisions may be employed in practice. Multiple units or components may be combined or integrated into another system, or certain features may be omitted or not implemented. Additionally, the described couplings, whether direct, indirect, or communicative, may be achieved through various interfaces, devices, or units using electrical, mechanical, or other forms of connection.

[0126] The functional units described herein may or may not be physically separate. Displayed units may or may not constitute physical entities and may be located in a single location or distributed across multiple network entities. Some or all of the units may be selected based on the objectives of specific embodiments. Furthermore, each functional unit in the embodiments may be integrated into a single processing unit, exist as physically distinct units, or be integrated with other units into a single processing unit.

[0127] If the software function unit is realized and used and sold as a product, it may be stored in a readable storage medium in a computer. Based on this understanding, the technical plan proposed by the present disclosure may be essentially or partially realized in the form of a software product. Or, one part of the technical plan beneficial to conventional technology may be realized as the form of a software product. The software product in the computer is stored in a storage medium, including a plurality of commands for a computational device (such as a personal computer, a server, or a network device) to run all or some of the steps disclosed by the embodiments of the present disclosure. The storage medium includes a USB disk, a mobile hardAtty. Dkt. No. 10085-01-0180-PCT disk, a read-only memory (ROM), a random-access memory (RAM), a floppy disk, or other kinds of media capable of storing program codes.

[0128] While the present disclosure has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.

Claims

Atty. Dkt. No. 10085-01-0180-PCTWhat is claimed is:

1. A voice call processing method for execution by a six generation core network node, comprising: determining whether a 6G radio access network (RAN) node supports an internet protocol multimedia subsystem (IMS) voice call; determining whether a fifth generation (5G) network node supports Voice over New Radio (VoNR) when determining that the 6G RAN node does not support the IMS voice call; and initiating a handover or redirection of a user equipment (UE) for the IMS voice call from the 6G RAN node to a fourth generation (4G) network node for Voice over LTE (VoLTE) service when the 5G network node does not support VoNR.

2. The voice call processing method of claim 1, further comprising: receiving, from the 5G network node, an indication whether the 5G network node supports VoNR.

3. The voice call processing method of claim 1, wherein whether the 5G network node supports VoNR is determined based on a capability report received from a 5G RAN node.

4. The voice call processing method of claim 3, wherein the capability report is an event-driven report triggered when a VoNR support status changes in the 5G RAN node.

5. The voice call processing method of claim 3, wherein the capability report is reported based on periodic reporting.

6. The voice call processing method of claim 1, wherein the determining whether the 6G RAN node supports the IMS voice call comprises: determining voice support capability of the 6G RAN node based on a capability report received from the 6G RAN node.

7. The voice call processing method of claim 6, wherein the capability report is an event-driven report triggered when a support status of the IMS voice call changes in the 6G RAN node.

8. The voice call processing method of claim 6, wherein the capability report is reported based on periodic reporting.

9. The voice call processing method of claim 1, wherein initiating the handover or redirection comprises: performing a 6G-4G inter-RAT (Radio Access Technology) mobility procedure from the 6G RAN node to the 4G network node.

10. The voice call processing method of claim 1, wherein the voice call is a mobile originated (MO) call, and the method further comprises: receiving a request from the UE to establish an IMS PDU session for IMS voice traffic of the voice call; and rejecting the request before determining whether the 5G network node supports VoNR.

11. The voice call processing method of claim 1, wherein the voice call is a mobile terminated (MT) call, and the method further comprises: receiving an MT call indication from an IMS server; and determining whether the 5G network node supports VoNR before sending a paging message to the UE for establishing an IMS PDU session.

12. The voice call processing method of claim 1, further comprising: establishing an IMS PDU session for IMS signaling between the UE and an IMS server prior to determining whether the 6G RAN supports the IMS voice call.

13. The voice call processing method of claim 1, further comprising: after the handover or the redirection, establishing an Evolved Packet System (EPS) bearer in the 4G network node for the IMS voice call.

14. The voice call processing method of claim 1, wherein, after the handover or the redirection, a tracking area update (TAU) procedure is performed for the UE in the 4G network.

15. A network node comprising: a processor configured to call and run a computer program stored in a memory, to cause a deviceAtty. Dkt. No. 10085-01-0180-PCT in which the processor is installed to execute the method of any of claims 1 to 14.

16. A chip, comprising: a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any of claims 1 to 14.

17. A non-transitory computer-readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any of claims 1 to 14.

18. A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any of claims 1 to 14.

19. A computer program, wherein the computer program causes a computer to execute the method of any of claims 1 to 14.

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