Description:RESERVATION OF RIGHTS
[001] A portion of the disclosure of this patent document contains material which is subject to intellectual property rights such as, but are not limited to, copyright, design, trademark, integrated circuit (IC) layout design, and/or trade dress protection, belonging to Jio Platforms Limited (JPL) or its affiliates (herein after referred as owner). The owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all rights whatsoever. All rights to such intellectual property are fully reserved by the owner.

TECHNICAL FIELD
[002] The present disclosure relates to a field of 5G standalone (SA) cellular technology, and specifically to a system and a method for performing proactive signalling between a 5th Generation System (5GS) and an Evolved Packet System (EPS) to save connection time in an EPS fallback call.

BACKGROUND
[003] The following description of related art is intended to provide background information pertaining to the field of the disclosure. This section may include certain aspects of the art that may be related to various features of the present disclosure. However, it should be appreciated that this section be used only to enhance the understanding of the reader with respect to the present disclosure, and not as admissions of prior art.
[004] In an initial phase of a stand-alone 5th Generation System (5GS) deployment scenario, Voice over New Radio (VoNR) may not have a full-fledged ecosystem with devices relying on a 4th Generation (4G) Voice over Long Term Evolution (VoLTE) for voice services by considering User Equipment (UE) capabilities, inter-core network interface (N26) deployment, and VoNR support in a Next Generation-Radio Access Network (NG-RAN). Therefore, the 5GS has to be tightly coupled to an existing 4G VoLTE deployment to provide a seamless voice service across a whole network with good characteristics.
[005] The 5GS may choose to handover or redirect the UE to the LTE. Handover-based EPS fallback may have different sets of challenges, for example, the UE moved to the LTE cell may face poor signal quality due to which a probability of a successful call connection becomes low. Redirection-based EPS fallback may address the signal quality issue as the UE scans and selects best LTE cell upon receiving a redirection command from the NG-RAN, thus, ensuring that the fallback happens on the LTE cell that is best in terms of signal level and quality and sustains a voice call connection. However, redirection-based EPS fallback may have a separate set of challenges.
[006] The 5GS may provide a release with a redirection command instructing the UE to reselect to the LTE cell where a new radio connection may be started for the VoLTE call. In this scenario, a Radio Resource Control (RRC) connection may be first released with the 5G RAN before a new RRC connection is established with the LTE RAN. After the RRC connection is setup with the LTE cell, the UE may perform a tracking area update (TAU) request after which context is transferred from an Access and Mobility Management Function (AMF) to a Mobility Management Entity (MME) over a N26 interface. The MME may add Quality of Service (QoS) flows for data and Internet Protocol (IP) Multimedia Subsystem (IMS), and add the QOS flow for the voice call as a separate signalling. This request-response-based signaling may consume extra time.
[007] There is, therefore, a need in the art to provide an improved system and a method for performing proactive signalling between core networks to overcome the deficiencies in the prior art(s).

OBJECTS OF THE PRESENT DISCLOSURE
[008] It is an object of the present disclosure to provide a system and a method to perform proactive signalling between a 5th Generation System (5GS) and an Evolved Packet System (EPS).
[009] It is an object of the present disclosure to enhance 5G New Radio (NR) voice call EPS fallback.
[0010] It is an object of the present disclosure to save connection time in an EPS fallback call.
[0011] It is an object of the present disclosure to obtain User Equipment (UE) context and establish a Quality of Service (QOS) bearer while a UE is still in a process of moving to a 4th Generation (4G) system (for example, EPS).

SUMMARY
[0012] This section is provided to introduce certain objects and aspects of the present disclosure in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter.
[0013] In an aspect, the present disclosure relates to a system for performing proactive signalling between core networks including a 5th Generation System (5GS) and an Evolved Packet System (EPS). The system includes one or more processors, and a memory operatively coupled to the one or more processors. The memory includes processor-executable instructions, which on execution, cause the one or more processors to establish a Packet Data Unit (PDU) session between at least one User Equipment (UE) and a first core network, and transmit a PDU session modification request for establishing a Quality of Service (QoS) flow for a voice call to a first radio network entity associated with the first core network. The one or more processors are to enable the first radio network entity associated with the first core network to trigger a fallback for the voice call, based on a plurality of parameters, and receive a PDU session modification response from the first radio network entity associated with the first core network, where the PDU session modification response includes a flag indicating that the fallback for the voice call pertains to an Access Network (AN) release via inter-system redirection to a second radio network entity associated with a second core network. The one or more processors are to proactively receive context based on the flag and forward the context to a Mobility Management Entity (MME) of the second core network.
[0014] In an embodiment, the one or more processors may enable the MME of the second core network to receive a Tracking Area Update (TAU) request including a bearer identifier status from the at least one UE. The MME may transmit a TAU accept response with the bearer identifier status and piggyback a dedicated bearer activation request to the second radio network entity associated with the second core network for establishing the voice call. The one or more processors may enable the second radio network entity associated with the second core network to send a Radio Resource Control (RRC) reconfiguration message with the TAU accept response and the dedicated bearer activation request to the at least one UE in response to receiving the TAU accept response. The MME may receive a dedicated bearer activation accept message from the at least one UE after activation of the dedicated bearer by the at least one UE.
[0015] In an embodiment, the first core network may be a 5th Generation (5G) core network and the first radio network entity associated with the first core network may be a Next-Generation Node B (gNB or gNodeB), and the second core network may be a 4th Generation (4G) core network and the second radio network entity associated with the second core network may be an Evolved Node B (eNB).
[0016] In an embodiment, the plurality of parameters may include at least one of UE capabilities, an indication from the system, network configurations, and radio conditions.
[0017] In an embodiment, the one or more processors may proactively receive the context by being configured to transmit a Network Slice Management Function (Nsmf)_PDU session context request including mapped bearer contexts to a Packet Data Network Gateway Control plane (PGW-C) and a Session Management Function (SMF), and receive a Nsmf_PDU session context response including the mapped bearer contexts from the PGW-C and the SMF.
[0018] In an embodiment, the one or more processors may forward the context to the MME by being configured to transmit a forward context request to the MME, where a configurable timer is initiated by the MME in response to receiving the forward context request.
[0019] In an embodiment, the one or more processors may receive a forward context response including mapped context for Internet Protocol (IP) Multimedia Subsystem (IMS) signalling and data from the MME, where the mapped context may include Session Management (SM) context and UE context.
[0020] In an embodiment, the one or more processors may receive the forward context response by enabling the MME to transmit a create session request to a Serving Gateway (SGW), receive a create session response including bearer contexts from the SGW, and transmit a forward context response to the system in response to receiving the create session response.
[0021] In an embodiment, the one or more processors may enable the MME to stop the configurable timer based on the TAU request being received from the UE.
[0022] In an embodiment, the one or more processors may enable the MME to reject the TAU request by determining that the TAU request is received after an expiry of the configurable timer.
[0023] In an aspect, the present disclosure relates to a method for performing proactive signalling between core networks. The method includes establishing, by one or more processors associated with a system, a PDU session between at least one UE and a first core network. The method includes transmitting, by the one or more processors, a PDU session modification request for establishing a QoS flow for a voice call to a first radio network entity associated with the first core network. The method includes enabling, by the one or more processors, the first radio network entity associated with the first core network to trigger a fallback for the voice call, based on a plurality of parameters. The method includes receiving, by the one or more processors, a PDU session modification response from the first radio network entity associated with the first core network, where the PDU session modification response includes a flag indicating that the fallback for the voice call pertains to an Access Network (AN) release via inter-system redirection to a second radio network entity associated with a second core network. The method includes proactively receiving, by the one or more processors, context based on the flag, and forwarding the context to an MME of the second core network.
[0024] In an embodiment, the method may include enabling, by the one or more processors, the MME to receive a Tracking Area Update (TAU) request including a bearer identifier status from the at least one UE. The MME may transmit a TAU accept response with the bearer identifier status and piggyback a dedicated bearer activation request to the second radio network entity associated with the second core network for establishing the voice call, where the second radio network entity associated with the second core network may be enabled to send a Radio Resource Control (RRC) reconfiguration message with the TAU accept response and the dedicated bearer activation request to the at least one UE in response to receiving the TAU accept response. The MME may receive a dedicated bearer activation accept message from the at least one UE after activation of the dedicated bearer by the at least one UE.
[0025] In an embodiment, proactively receiving, by the one or more processors, the context may include transmitting, by the one or more processors, a Nsmf_PDU session context request including mapped bearer contexts to a PGW-C and a SMF, and receiving, by the one or more processors, a Nsmf_PDU session context response including the mapped bearer contexts from the PGW-C and the SMF.
[0026] In an embodiment, forwarding, by the one or more processors, the context to the MME may include transmitting, by the one or more processors, a forward context request to the MME, where a configurable timer is initiated by the MME in response to receiving the forward context request.
[0027] In an embodiment, the method may include receiving, by the one or more processors, a forward context response including mapped context for IMS signalling and data from the MME, where the mapped context includes SM context and UE context.
[0028] In an embodiment, receiving, by the one or more processors, the forward context response from the MME may include enabling the MME to transmit a create session request to an SGW, receive a create session response including bearer contexts from the SGW, and transmit the forward context response to the system in response to receiving the create session response.
[0029] In an embodiment, the method may include enabling, by the one or more processors, the MME to stop the configurable timer based on the TAU request being received from the at least one UE.

BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
[0031] The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:
[0032] FIG. 1A illustrates an exemplary sequential diagram (100A) depicting an existing Evolved Packet System (EPS) fallback with redirection.
[0033] FIG. 1B illustrates an exemplary sequential diagram (100B) for implementing an existing method of 5th Generation System (5GS) to EPS idle mode mobility over an N26 interface.
[0034] FIG. 1C illustrates an exemplary sequential diagram (100C) for implementing an existing method of EPS fallback with redirection.
[0035] FIG. 2 illustrates an exemplary network architecture (200) in which or with which embodiments of the present disclosure may be implemented.
[0036] FIG. 3 illustrates an exemplary block diagram (300) of a proposed system, in accordance with an embodiment of the present disclosure.
[0037] FIG. 4 illustrates an exemplary sequential diagram (400) of a proposed method, in accordance with an embodiment of the present disclosure.
[0038] FIG. 5 illustrates an exemplary computer system (500) in which or with which embodiments of the present disclosure may be implemented.

DETAILED DESCRIPTION
[0039] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0040] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address all of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein.
[0041] The ensuing description provides exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an exemplary embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[0042] Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
[0043] Also, it is noted that individual embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function.
[0044] The word “exemplary” and/or “demonstrative” is used herein to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as “exemplary” and/or “demonstrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art. Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used in either the detailed description or the claims, such terms are intended to be inclusive—in a manner similar to the term “comprising” as an open transition word—without precluding any additional or other elements.
[0045] Reference throughout this specification to “one embodiment” or “an embodiment” or “an instance” or “one instance” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
[0047] FIG. 1A illustrates an exemplary sequential diagram (100A) depicting an existing Evolved Packet System (EPS) fallback with redirection.
[0048] With respect to FIG. 1A, at 102, a User Equipment (UE) may establish a Mobile Originated (MO) and a Mobile Terminated (MT) Internet Protocol (IP) Multimedia Subsystem (IMS) voice session in a 5th Generation System (5GS), and initiate a Quality of Service (QoS) flow for voice establishment.
[0049] At 104, a Next Generation-Radio Access Network (NG-RAN) may initiate a Packet Data Unit (PDU) session modification to setup the QoS flow for IMS voice by sending a request to a Policy Control Function (PCF).
[0050] At 106, the NG-RAN may trigger for fallback and perform optical measurement report solicitation.
[0051] At 108, the NG-RAN may reject the PDU session modification indicating the IMS voice fallback in progress.
[0052] At 110, the UE may perform redirection or handover to an Evolved Packet System (EPS), for example, the PCF.
[0053] At 112, the UE may perform a Tracking Area Update (TAU) procedure, after which context is transferred from an Access and Mobility Management Function (AMF) to a Mobility Management Entity (MME) over a N26 interface.
[0054] At 114, the UE may send a Packet Data Network (PDN) connectivity request with a request type “handover” to at least one of a Packet gateway (P-GW), a Serving Gateway (S-GW), and a User Plane Function (UPF).
[0055] At 116, the UE or the NG-RAN may initiate PDN connection modification to setup a dedicated bearer for voice.
[0056] At 118, the UE may establish the IMS voice session.
[0057] FIG. 1B illustrates an exemplary sequential diagram (100B) for implementing an existing method of 5GS to EPS idle mode mobility over an N26 interface.
[0058] With respect to FIG. 1B, at 122, the UE may perform a TAU trigger, and at 124, the UE may send a TAU request to an EPS, for example, eNodeB (eNB).
[0059] At 126, the eNB may send the TAU request to an MME.
[0060] At 128, the MME may send a context request to an AMF, upon receiving the TAU request.
[0061] At 130A-130C, the AMF may send a Network slice management function (NSMF)_PDU session context request to a Packet-Gateway-Control function (P-GW-C) or a Session Management Function (SMF). The P-GW-C or the SMF may perform N4 session modification along with a Packet-Gateway-User Plane (P-GW-U) or the UPF. Further, the P-GW-C or the SMF may send an NSMF_PDU session context response to the AMF.
[0062] At 132, the AMF may send the NSMF_PDU session context response to the MME.
[0063] At 134, based on the NSMF_PDU session context response, authentication/security may be enabled.
[0064] At 136, a context acknowledgment may be sent from the MME to the AMF.
[0065] At 138, the MME may send a create session request to a S-GW.
[0066] At 140, the S-GW may send a modify bearer request to the P-GW-C or the SMF.
[0067] At 142, the P-GW-C or the SMF may perform N4 session modification along with the P-GW-U or the UPF.
[0068] At 144, the P-GW-C or the SMF may send a modify bearer response to the S-GW.
[0069] At 146, the S-GW may send a create session response to the MME upon receiving the modify bearer response.
[0070] At 148, the MME may send an update location request to a Home Subscriber Service/Unified Data Management (HSS/UDM).
[0071] At 150 and 152, the HSS/UDM may send a Nudm_UECM deregistration notification request to the AMF. Further, the AMF may send a Nudm_SDM unsubscribe request to the HSS/UDM.
[0072] At 154, an update location response may be sent to the MME by the HSS/UDM.
[0073] At 156 and 158, a TAU accept response may be sent to the UE and perform TAU. The P-GW may require a dedicated bearer setup to perform the TAU.
[0074] FIG. 1C illustrates an exemplary sequential diagram (100C) for implementing an existing method of EPS fallback with redirection.
[0075] With respect to FIG. 1C, at 162, an AMF may send a PDU session resources modification request for establishing a voice call to a gNB.
[0076] At 164, the gNB may transmit a RRC release with redirect command to a UE.
[0077] At 166, the gNB may transmit a PDU session resources modification response to the AMF.
[0078] At 168, the UE may send a TAU request with a status of a bearer identifier status as active to an eNB.
[0079] At 170, the eNB may transmit the TAU request with the status of the bearer identifier status as active to the MME.
[0080] At 172, the MME may transmit a context request to the AMF. The AMF may send a PDU session context request to a SMF and a P-GW-C, where a session modification may be performed. Further, the SMF and a P-GW-C may send a PDU session context response to the AMF.
[0081] At 174, the AMF may send a context response to the MME in response to receiving the PDU session context response. The MME send an acknowledgement upon receiving the context response.
[0082] At 176, the MME may transmit a create session request for data and Internet Protocol (IP) Multimedia System (IMS) signalling to an SGW. The SGW may transmit a modify bearer request to the SMF and the P-GW-C. The session modification may be performed in response to receiving the modify bearer request. Further, the SMF and the P-GW-C may transmit a modify bearer response to the SGW.
[0083] At 178, the SGW may transmit a create session response for data and IMS signalling to the MME.
[0084] At 180, the MME may transmit a TAU accept message with the status of the bearer identifier status as active to the eNB. The eNB may transmit a RRC configuration request to add Data Radio Bearers (DRBs) mapped to the data and the IMS signalling to the UE, and receive a RRC configuration completion response from the UE. Further, the eNB may transmit the TAU accept message with the status of the bearer identifier status as active to the UE.
[0085] At 182, the MME may transmit a dedicated bearer context activation request to the eNB. The eNB may again transmit the RRC configuration request to add Data Radio Bearers (DRBs) mapped to the data and the IMS signalling to the UE, and receive a RRC configuration completion response from the UE.
[0086] At 184, the eNB may send the dedicated bearer context activation request to the UE.
[0087] At 186, the UE may transmit a dedicated bearer context activation accept message to the MME.
[0088] In the existing method, the MME may first add the QOS flows for the data and the IMS and then add the QOS flow for the voice call as a separate signalling. This request-response based signalling may consume extra time. Therefore, there is, a need for an improved system and a method for performing proactive signalling between one or more core networks to save the connection time.
[0089] The present disclosure relates to a 5th Generation New Radio (5G NR) voice call EPS fallback enhancement for proactive signaling to save extra signaling and connection time. The present disclosure provides a system and a method to enhance a 5G system (5GS) to perform proactive signalling between a 5G Radio Access Network (RAN) (for example, gNodeB), AMF, SMF, MME, P-GW, S-GW, and a Long-Term Evolution (LTE) RAN (for example, eNodeB) to obtain a UE context. The system may establish a QOS bearer while a UE is still in the process of moving to a 4G system (for example, an Evolved Packet System (EPS)).
[0090] The various embodiments of the present disclosure will be explained in detail with reference to FIGs. 2 to 5.
[0091] FIG. 2 illustrates an exemplary network architecture (200) in which or with which embodiments of the present disclosure may be implemented.
[0092] Referring to FIG. 2, the network architecture (200) may include one or more computing devices (204-1, 204-2…204-N) associated with one or more users (202-1, 202-2…202-N) in an environment. A person of ordinary skill in the art will appreciate that the terms “computing device(s)” and “User Equipment (UE)” may be used interchangeably throughout the disclosure. A person of ordinary skill in the art will understand that one or more users (202-1, 202-2…202-N) may be individually referred to as the user (202) and collectively referred to as the users (202). Similarly, a person of ordinary skill in the art will understand that one or more UEs (204-1, 204-2…204-N) may be individually referred to as the UE (204) and collectively referred to as the UE (204). Although three UEs (204) are depicted in FIG. 2, however any number of the UEs (204) may be included without departing from the scope of the ongoing description.
[0093] In an embodiment, the UE (204) may include smart devices operating in a smart environment, for example, an Internet of Things (IoT) system. In such an embodiment, the UE (204) may include, but is not limited to, smart phones, smart watches, smart sensors (e.g., mechanical, thermal, electrical, magnetic, etc.), networked appliances, networked peripheral devices, networked lighting system, communication devices, networked vehicle accessories, networked vehicular devices, smart accessories, tablets, smart television (TV), computers, smart security system, smart home system, other devices for monitoring or interacting with or for the users (202) and/or entities, or any combination thereof. A person of ordinary skill in the art will appreciate that the UE (204) may include, but is not limited to, intelligent, multi-sensing, network-connected devices, that can integrate seamlessly with each other and/or with a central server or a cloud-computing system or any other device that is network-connected.
[0094] In an embodiment, the UE (204) may include, but is not limited to, a handheld wireless communication device (e.g., a mobile phone, a smart phone, a phablet device, and so on), a wearable computer device (e.g., a head-mounted display computer device, a head-mounted camera device, a wristwatch computer device, and so on), a Global Positioning System (GPS) device, a laptop computer, a tablet computer, or another type of portable computer, a media playing device, a portable gaming system, and/or any other type of computer device with wireless communication capabilities, and the like. In an embodiment, the UE (204) may include, but is not limited to, any electrical, electronic, electromechanical, or an equipment, or a combination of one or more of the above devices such as virtual reality (VR) devices, augmented reality (AR) devices, laptop, a general-purpose computer, desktop, personal digital assistant, tablet computer, mainframe computer, or any other computing device, wherein the UE (204) may include one or more in-built or externally coupled accessories including, but not limited to, a visual aid device such as a camera, an audio aid, a microphone, a keyboard, and input devices for receiving input from the user (202) or the entity such as a touchpad, a touch enabled screen, an electronic pen, and the like. A person of ordinary skill in the art will appreciate that the UE (204) may not be restricted to the mentioned devices and various other devices may be used.
[0095] Referring to FIG. 2, the UE (204) may communicate with a system (208) through a network (206). In an embodiment, the network (206) may include at least one of a Fifth Generation (5G) network, or the like. The network (206) may enable the UE (204) to communicate with other devices in the network architecture (200) and/or with the system (208). The network (206) may include a wireless card or some other transceiver connection to facilitate this communication. In another embodiment, the network (206) may be implemented as, or include any of a variety of different communication technologies such as a wide area network (WAN), a local area network (LAN), a wireless network, a mobile network, a Virtual Private Network (VPN), the Internet, the Public Switched Telephone Network (PSTN), or the like.
[0096] In accordance with embodiments of the present disclosure, the system (208) may be designed and configured for enhancing a 5GS to perform proactive signalling between a 5G RAN (for example, gNodeB (gNB)), SMF, MME, P-GW, S-GW, and an LTE RAN (for example, eNodeB (eNB)) to obtain a UE context. The system (208) may establish a QOS bearer while the UE (204) is still in the process of moving to a 4G system (for example, an EPS). It may be appreciated that the system (208) may be interchangeably referred to as an Access and Mobility Management Function (AMF) hereinafter.
[0097] In an embodiment, the system (208) may be connected with one or more core network(s) (210-1, 210-2…210-N). A person of ordinary skill in the art will understand that one or more core network(s) (210-1, 210-2…210-N) may be individually referred to as the core network (210) and collectively referred to as the core network (210). For example, a first core network (210-1) may be a 5th Generation (5G) core network in a 5GS, and a second core network (210-2) may be a 4th Generation (4G) core network in the EPS.
[0098] Although FIG. 2 shows exemplary components of the network architecture (200), in other embodiments, the network architecture (200) may include fewer components, different components, differently arranged components, or additional functional components than depicted in FIG. 2. Additionally, or alternatively, one or more components of the network architecture (200) may perform functions described as being performed by one or more other components of the network architecture (200).
[0099] FIG. 3 illustrates an exemplary block diagram (300) of the system (208), in accordance with an embodiment of the present disclosure.
[00100] In an embodiment, and as shown in FIG. 3, the system (208) may include one or more processors (302). The one or more processors (302) may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, logic circuitries, and/or any devices that manipulate data based on operational instructions. Among other capabilities, the one or more processor(s) (302) may be configured to fetch and execute computer-readable instructions stored in a memory (304) of the system (208). The memory (304) may store one or more computer-readable instructions or routines, which may be fetched and executed to create or share the data units over a network service. The memory (304) may comprise any non-transitory storage device including, for example, volatile memory such as Random-Access Memory (RAM), or non-volatile memory such as Erasable Programmable Read-Only Memory (EPROM), flash memory, and the like.
[00101] In an embodiment, the system (208) may also comprise an interface(s) (306). The interface(s) (306) may comprise a variety of interfaces, for example, a variety of interfaces, for example, interfaces for data input and output devices, referred to as I/O devices, storage devices, and the like. The interface(s) (306) may facilitate communication of the system (208) with various devices coupled to it. The interface(s) (306) may also provide a communication pathway for one or more components of the system (208). Examples of such components include, but are not limited to, processing engine(s) (308) and a database (310).
[00102] In an embodiment, the processing engine(s) (308) may be implemented as a combination of hardware and programming (for example, programmable instructions) to implement one or more functionalities of the processing engine(s) (308). In the examples described herein, such combinations of hardware and programming may be implemented in several different ways. For example, the programming for the processing engine(s) (308) may be processor-executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the one or more processors (302) may comprise a processing resource (for example, one or more processors), to execute such instructions. In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, implement the processing engine(s) (308). In such examples, the system (208) may comprise the machine-readable storage medium storing the instructions and the processing resource to execute the instructions, or the machine-readable storage medium may be separate but accessible to the system (208) and the processing resource. In other examples, the processing engine(s) (308) may be implemented by electronic circuitry.
[00103] In an embodiment, the database (310) may comprise data that may be either stored or generated as a result of functionalities implemented by any of the components of the processor(s) (302) or the processing engine(s) (308) or the system (208).
[00104] In an embodiment, the processing engine(s) (308) may include one or more engines selected from any of an acquisition engine (312), a triggering engine (314), a transmission engine (316), and other engines (318). The other engines (318) may include, but not limited to, an Input/Output (I/O) engine, a determination engine, and the like.
[00105] In an embodiment, the one or more processors (302) may, via the acquisition engine (312), receive a Packet Data Unit (PDU) session establishment request from the UE (204). The one or more processors (302) may establish a PDU session between the UE (204) and a first core network (210-1). In an embodiment, the one or more processors (302) may, via the transmission engine (316), transmit a PDU session modification request for establishing a Quality of Service (QoS) flow for a voice call to a first radio network entity associated with the first core network (210-1).
[00106] It may be appreciated that the first core network may be interchangeably referred to as a 5G core network, and the first radio network entity associated with the first core network may be interchangeably referred to as a gNB throughout the description as provided herein. It may be appreciated that a second core network may be interchangeably referred to as a 4G core network and a second radio network entity associated with the second core network (210-2) may be interchangeably referred to as an eNB throughout the description as provided herein. In an embodiment, the system (208) may camp on the 5GS and may be interchangeably referred to as an Access and Mobility Management Function (AMF).
[00107] In an embodiment, the one or more processors (302) may, via the triggering engine (314), enable the first radio network entity associated with the first core network (210-1) to trigger a fallback for the voice call, based on a plurality of parameters. The plurality of parameters may include, but not limited to, UE capabilities, an indication from the AMF, network configurations, and radio conditions.
[00108] In an embodiment, the one or more processors (302) may, via the acquisition engine (312), receive a PDU session modification response from the first radio network entity associated with the first core network (210-1). The PDU session modification response may be a PDU session modification rejection message by determining that the fallback for voice call to the second radio network entity associated with the second core network (210-2) is ongoing. The PDU session modification response may include a flag indicating that the fallback for the voice call pertains to an Access Network (AN) release via inter-system redirection to the second radio network entity associated with the second core network (210-2).
[00109] In an embodiment, the one or more processors (302) may proactively receive context based on the flag. In an embodiment, the one or more processors (302) may forward the context to the MME of the second core network (210-2).
[00110] In an embodiment, the one or more processors (302) may proactively receive the context by transmitting a Network Slice Management Function (Nsmf)_PDU session context request including mapped bearer contexts to a Packet Data Network Gateway Control plane (PGW-C) and a Session Management Function (SMF). The one or more processors (302) may receive a Nsmf_PDU session context response including the mapped bearer contexts from the PGW-C and the SMF. The mapped bearer contexts may include, but not limited to, PGW-C control plane tunnel information of a Packet Data Network (PDN) connection corresponding to the PDU session, EPS Bearer Identifier (EBI) for each EPS bearer, PGW-U tunnel information for each EPS bearer, and EPS QoS parameters for each EPS bearer.
[00111] In an embodiment, the one or more processors (302) may forward the context to the MME of the second core network (210-2) by transmitting a forward context request to the MME. The MME may initiate a configurable timer in response to receiving the forward context request. The one or more processors (302) may receive a forward context response including mapped context for Internet Protocol (IP) Multimedia Subsystem (IMS) signalling and data from the MME. The mapped context may include, but not limited to, Session Management (SM) context and UE context.
[00112] In an embodiment, the one or more processors (302) may enable the MME to receive a Tracking Area Update (TAU) request from the at least one UE (204) before an expiry of a configurable timer. The TAU request may include a status of a bearer identifier as active. In an embodiment, the MME may transmit a create session request to a Serving Gateway (SGW). In an embodiment, the MME may receive a create session response including bearer contexts from the SGW. In an embodiment, the MME may transmit the forward context response to the system (208) in response to receiving the create session response. In an embodiment, the MME may send a TAU accept response with the status of the bearer identifier as active to the second radio network entity associated with the second core network (210-2). The TAU accept response may include an EPS Session Management (ESM) container including a dedicated bearer activation request to activate a dedicated bearer.
[00113] In an embodiment, the one or more processors (302) may enable the MME to stop the configurable timer based on the TAU request being received from the UE (204). In an embodiment, the MME may release the UE context to the AMF by determining that the TAU request is received after a configured time. In an embodiment, the MME may reject the TAU request by determining that the TAU request is received after an expiry of the configurable timer.
[00114] In an embodiment, the one or more processors (302) may enable the second radio network entity associated with the second core network (210-2) to transmit a Radio Resource Control (RRC) reconfiguration message with the dedicated bearer activation request to the at least one UE (204) in response to receiving the TAU accept response. The RRC reconfiguration message may include two Non-Access Stratum (NAS) Downlink (DL) messages in a dedicatedNASList container. The two NAS DL messages may be the TAU accept response and the dedicated bearer activation request. The RRC reconfiguration message may be transmitted to the at least one UE (204) to add Data Radio Bearer (DRB) for the voice call, data, and IMS signalling. In an embodiment, the second core network (210-2) may receive a dedicated bearer activation accept message from the at least one UE (204) after activating the dedicated bearer by the at least one UE (204).
[00115] Although FIG. 3 shows an exemplary block diagram (300) of the proposed system (208), in other embodiments, the system (208) may include fewer components, different components, differently arranged components, or additional functional components than depicted in FIG. 3. Additionally, or alternatively, one or more components of the system (208) may perform functions described as being performed by one or more other components of the system (208).
[00116] FIG. 4 illustrates an exemplary sequential diagram (400) of a proposed method, in accordance with an embodiment of the present disclosure.
[00117] With respect to FIG. 4, at 402, a UE (204) may camp on a first core network (210-1) for example, an NG-RAN or a 5G core network in a 5GS and an MO or MT IMS voice session establishment may be initiated.
[00118] At 404, a system (208) may transmit a PDU session modification request to a first radio network entity for example, a gNB associated with the first core network (210-1) to setup a QoS flow for a voice call. The system (208) may be referred to as an AMF.
[00119] At 406, the gNB may be configured to support EPS fallback for IMS voice and decide to trigger fallback to a second radio network entity for example, an eNB associated with a second core network (210-2) for example, a 4G core network, by considering UE capabilities, indication from the AMF (208) that "Redirection for EPS fallback for voice is possible", network configuration (e.g., N26 availability configuration), and radio conditions.
[00120] At 408, the gNB may provide a response indicating rejection of the PDU session modification to setup QoS flow for IMS voice received in step 404. The gNB may transmit a PDU session response message towards a PGW-C and a SMF (or a Home-SMF (H-SMF) and a P-GW-C via a Visited SMF (VSMF), in case of roaming scenario) via the AMF (208). The PDU session response message may be sent with an indication that mobility due to fallback for IMS voice is ongoing. The gNB may include a flag that specifies the “fallback type” as AN release via an inter-system redirection to the eNBand not hand over.
[00121] At 410, the gNB may initiate either handover or AN release via the inter-system redirection to the eNB by considering the UE capabilities.
[00122] At 412, the AN Release via the inter-system redirection to the eNB may be considered where the UE (204) receives a Radio Resource Control (RRC) release command with redirection information. The AMF (208) may check a “Fallback type” flag and if the flag is AN release via the inter-system redirection to the eNB, the AMF (208) may request the PGW-C and the SMF to provide a Session Management (SM) context by using a Nsmf_PDUSession_ContextRequest that also includes mapped EPS bearer contexts.
[00123] At 414, the SMF may return mapped EPS bearer contexts, which include PGW-C control plane tunnel information of PDN connection corresponding to a PDU session, EBI for each EPS bearer, PGW-U tunnel information for each EPS bearer, and EPS QoS parameters for each EPS bearer.
[00124] At 416, the AMF (208) may select an MME of the second core network (210-2) and transmit a forward context request to the MME. The forward context request may include the mapped SM EPS UE context for 5G QoS Identifier (5QI) 5(IMS signalling) and 5QI 9(data). In addition, the AMF (208) may indicate the MME about creation of a dedicated bearer for voice call (5QI 1).
[00125] At 418, once the MME receives the forward context request from the AMF (208), the MME may start a configurable timer. The timer may stop once the MME receives a TAU request from the UE (204). If the TAU request is not received within a configured time, the MME may release the UE context. If the TAU is received after the timer expiry, the MME may reject the TAU request.
[00126] At 420, the UE (204) may select best LTE cell after receiving a RRC release with redirection command, and camp on the selected LTE cell. A UE Non-Access Stratum (NAS) layer may trigger the TAU request.
[00127] At 422, the UE (204) may initiate a TAU procedure by sending the TAU request with a status of EBI for the IMS and the data as active to the eNB.
[00128] At 424, the MME may receive the TAU request from the UE (204) before the timer expiry.
[00129] At 426, the MME may transmit a create session request (bearer contexts including QCI 9, QCI 5, and QCI 1) to the SGW.
[00130] At 428, the SGW may respond with a create session response including bearer contexts for the QCI9, the QCI 5, and the QCI 1 to the MME.
[00131] At 430, the MME upon receiving the create session response from the SGW, may transmit a forward context response to the AMF (208).
[00132] At 432, the MME may send a TAU accept message to the UE (204) and may include the status of the QCI 5 and the QCI 9. Along with the TAU accept message, the MME may also include an ESM container in the TAU accept message that may carry “Activate dedicated eps bearer request” to activate the QCI 1.
[00133] At 434, in response, the second radio network entity associated with the second core network (210-2) may send an RRC reconfiguration message to the UE (204) that may add DRBs mapped to the QCI 9, the QCI 5, and the QCI 1. The reconfiguration message may also carry a dedicated NAS list container that carries “Activate dedicated bearer request” to be delivered to the UE (204).
[00134] At 436, after activating the dedicated bearer, the UE (204) may respond to the gNB with “Activate dedicated EPS bearer context accept message”. This may ensure proactive signalling between the first core network (210-1) and the second core network (210-2), thereby saving extra signalling and time in the EPS fallback.
[00135] FIG. 5 illustrates an exemplary computer system (500) in which or with which embodiments of the present disclosure may be implemented.
[00136] As shown in FIG. 5, the computer system (500) may include an external storage device (510), a bus (520), a main memory (530), a read only memory (540), a mass storage device (550), a communication port (560), and a processor (570). A person skilled in the art will appreciate that the computer system (500) may include more than one processor (570) and communication ports (560). Processor (570) may include various modules associated with embodiments of the present disclosure.
[00137] In an embodiment, the communication port (560) may be any of an RS-232 port for use with a modem-based dialup connection, a 10/100 Ethernet port, a Gigabit or 10 Gigabit port using copper or fiber, a serial port, a parallel port, or other existing or future ports. The communication port (560) may be chosen depending on a network, such a Local Area Network (LAN), Wide Area Network (WAN), or any network to which computer system connects.
[00138] In an embodiment, the memory (530) may be Random Access Memory (RAM), or any other dynamic storage device commonly known in the art. Read-only memory (540) may be any static storage device(s) e.g., but not limited to, a Programmable Read Only Memory (PROM) chips for storing static information e.g., start-up or Basic Input/Output System (BIOS) instructions for the processor (570).
[00139] In an embodiment, the mass storage (550) may be any current or future mass storage solution, which may be used to store information and/or instructions. Exemplary mass storage solutions include, but are not limited to, Parallel Advanced Technology Attachment (PATA) or Serial Advanced Technology Attachment (SATA) hard disk drives or solid-state drives (internal or external, e.g., having Universal Serial Bus (USB) and/or Firewire interfaces), one or more optical discs, Redundant Array of Independent Disks (RAID) storage, e.g., an array of disks (e.g., SATA arrays).
[00140] In an embodiment, the bus (520) communicatively couples the processor(s) (570) with the other memory, storage and communication blocks. The bus (520) may be, e.g., a Peripheral Component Interconnect (PCI)/PCI Extended (PCI-X) bus, Small Computer System Interface (SCSI), Universal Serial Bus (USB) or the like, for connecting expansion cards, drives and other subsystems as well as other buses, such a front side bus (FSB), which connects the processor (570) to the computer system (500).
[00141] Optionally, operator and administrative interfaces, e.g., a display, keyboard, joystick, and a cursor control device, may also be coupled to the bus (520) to support direct operator interaction with the computer system (500). Other operator and administrative interfaces may be provided through network connections connected through the communication port (560). Components described above are meant only to exemplify various possibilities. In no way should the aforementioned exemplary computer system (500) limit the scope of the present disclosure.
[00142] While the foregoing describes various embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the present disclosure is determined by the claims that follow. The present disclosure is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the present disclosure when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[00143] The present disclosure provides a system and a method to perform proactive signalling between a 5th Generation System (5GS) and an Evolved Packet System (EPS).
[00144] The present disclosure enhances 5G New Radio (NR) voice call EPS fallback.
[00145] The present disclosure saves connection time in an EPS fallback call.
[00146] The present disclosure obtains User Equipment (UE) context and establishes a Quality of Service (QOS) bearer in an efficient manner, while a UE is still in a process of moving to a 4th Generation (4G) system (for example, EPS).
, Claims:1. A system (208) for performing proactive signalling between core networks, the system (208) comprising:
one or more processors (302); and
a memory (304) operatively coupled to the one or more processors (302), wherein the memory (304) comprises processor-executable instructions, which on execution, cause the one or more processors (302) to:
establish a Packet Data Unit (PDU) session between at least one User Equipment (UE) (204) and a first core network (210-1)
transmit a PDU session modification request for establishing a Quality of Service (QoS) flow for a voice call to a first radio network entity associated with the first core network (210-1);
enable the first radio network entity associated with the first core network (210-1) to trigger a fallback for the voice call, based on a plurality of parameters;
receive a PDU session modification response from the first radio network entity associated with the first core network (210-1), wherein the PDU session modification response comprises a flag indicating that the fallback for the voice call pertains to an Access Network (AN) release via inter-system redirection to a second radio network entity associated with a second core network (210-2); and
proactively receive context based on the flag and forward the context to a Mobility Management Entity (MME) of the second core network (210-2).

2. The system (208) as claimed in claim 1, wherein the one or more processors (302) are to enable the MME to:
receive a Tracking Area Update (TAU) request comprising a bearer identifier status from the at least one UE (204);
transmit a TAU accept response with the bearer identifier status and piggyback a dedicated bearer activation request to the second radio network entity associated with the second core network (210-2) for establishing the voice call, wherein the one or more processors (302) are to enable the second radio network entity associated with the second core network (210-2) to send a Radio Resource Control (RRC) reconfiguration message with the TAU accept response and the dedicated bearer activation request to the at least one UE (204) in response to receiving the TAU accept response; and
receive a dedicated bearer activation accept message from the at least one UE (204) after activation of the dedicated bearer by the at least one UE (204).

3. The system (208) as claimed in claim 1, wherein the first core network (210-1) is a 5th Generation (5G) core network and the first radio network entity associated with the first core network (210-1) is a Next-Generation Node B (gNB), and wherein the second core network (210-2) is a 4th Generation (4G) core network and the second radio network entity associated with the second core network (210-2) is an Evolved Node B (eNB).

4. The system (208) as claimed in claim 1, wherein the plurality of parameters comprises at least one of: UE capabilities, an indication from the system (208), network configurations, and radio conditions.

5. The system (208) as claimed in claim 1, wherein the one or more processors (302) are to proactively receive the context by being configured to:
transmit a Network Slice Management Function (Nsmf)_PDU session context request comprising mapped bearer contexts to a Packet Data Network Gateway Control plane (PGW-C) and a Session Management Function (SMF); and
receive a Nsmf_PDU session context response comprising the mapped bearer contexts from the PGW-C and the SMF.
6. The system (208) as claimed in claim 1, wherein the one or more processors (302) are to forward the context to the MME by being configured to:
transmit a forward context request to the MME, wherein a configurable timer is initiated by the MME in response to receiving the forward context request.

7. The system (208) as claimed in claim 6, wherein in response to transmitting the forward context request to the MME, the one or more processors (302) are to receive a forward context response comprising mapped context for Internet Protocol (IP) Multimedia Subsystem (IMS) signalling and data from the MME, wherein the mapped context comprises Session Management (SM) context, and UE context.

8. The system (208) as claimed in claim 7, wherein the one or more processors (302) are to receive the forward context response by enabling the MME to:
transmit a create session request to a Serving Gateway (SGW);
receive a create session response comprising bearer contexts from the SGW; and
transmit the forward context response to the system (208) in response to receiving the create session response.

9. The system (208) as claimed in claim 6, wherein the one or more processors (302) are to enable the MME to stop the configurable timer based on the TAU request being received from the at least one UE (204).
10. The system (208) as claimed in claim 6, wherein the one or more processors (302) are to enable the MME to reject the TAU request by determining that the TAU request is received after the expiry of the configurable timer.

11. A method for performing proactive signalling between core networks, the method comprising:
establishing, by one or more processors (302) associated with a system (208), a Packet Data Unit (PDU) session between at least one User Equipment (UE) (204) and a first core network (210-1);
transmitting, by the one or more processors (302), a PDU session modification request for establishing a Quality of Service (QoS) flow for a voice call to a first radio network entity associated with the first core network (210-1);
enabling, by the one or more processors (302), the first radio network entity associated with the first core network (210-1) to trigger a fallback for the voice call, based on a plurality of parameters;
receiving, by the one or more processors (302), a PDU session modification response from the first radio network entity associated with the first core network (210-1), wherein the PDU session modification response comprises a flag indicating that the fallback for the voice call pertains to an Access Network (AN) release via inter-system redirection to a second radio network entity associated with a second core network (210-2); and
proactively receiving, by the one or more processors (302), context based on the flag, and forwarding, by the one or more processors (302), the context to a Mobility Management Entity (MME) of the second core network (210-2).

12. The method as claimed in claim 11, comprising enabling, by the one or more processors (302), the MME to:
receive a Tracking Area Update (TAU) request comprising a bearer identifier status from the at least one UE (204);
transmit a TAU accept response with the bearer identifier status and piggyback a dedicated bearer activation request to the second radio network entity associated with the second core network (210-2) for establishing the voice call, wherein the second radio network entity associated with the second core network (210-2) is enabled to send a Radio Resource Control (RRC) reconfiguration message with the TAU accept response and the dedicated bearer activation request to the at least one UE (204) in response to receiving the TAU accept response; and
receive a dedicated bearer activation accept message from the at least one UE (204) after activation of the dedicated bearer by the at least one UE (204).

13. The method as claimed in claim 11, wherein proactively receiving, by the one or more processors (302), the context comprises:
transmitting, by the one or more processors (302), a Network Slice Management Function (Nsmf)_PDU session context request comprising mapped bearer contexts to a Packet Data Network Gateway Control plane (PGW-C) and a Session Management Function (SMF); and
receiving, by the one or more processors (302), a Nsmf_PDU session context response comprising the mapped bearer contexts from the PGW-C and the SMF.

14. The method as claimed in claim 11, wherein forwarding, by the one or more processors (302), the context to the MME comprises:
transmitting, by the one or more processors (302), a forward context request to the MME, wherein a configurable timer is initiated by the MME in response to receiving the forward context request.

15. The method as claimed in claim 14, comprising:
in response to transmitting the forward context request to the MME, receiving, by the one or more processors, a forward context response comprising mapped context for Internet Protocol (IP) Multimedia Subsystem (IMS) signalling and data from the MME, wherein the mapped context comprises Session Management (SM) context, and UE context.
16. The method as claimed in claim 15, wherein receiving, by the one or more processors, the forward context response from the MME comprises enabling the MME to:
transmit a create session request to a Serving Gateway (SGW);
receive a create session response comprising bearer contexts from the SGW; and
transmit the forward context response to the system (208) in response to receiving the create session response.

17. The method as claimed in claim 14, comprising enabling, by the one or more processors (302), the MME to stop the configurable timer based on the TAU request being received from the at least one UE (204).