5G NR Voice Call EPS Fallback Enhancement

Abstract

The present disclosure relates to 5G NR voice call EPS fallback enhancement. The invention discloses an apparatus, system and method for performing a method for EPS fallback when a user equipment device (UE) initiates a voice call while camping on a 5G cell. The UE can camp on a 5G network by performing an IMS registration process / IMS SIP invitation process using IMS. The UE can initiate a voice call and determine that the voice call cannot be established through the 5G NR network. In response, the UE can perform a TAU process or a connection process with a cell of a 4G network. The IMS can be transmitted to the 4G network during the TAU process / connection process. In response to determining that the UE is prohibited from accessing the 4G network, the UE can switch back to the 5G network and transmit a SIP cancel request to the 5G NR network to allow the context associated with the UE to be cleared from the IMS.

Description

Technical Field

[0001] The present application relates to wireless devices, and more particularly to apparatus, systems and methods for 3GPP 5G NR voice call fallback to Evolved Packet System (EPS) enhancement. Background Art

[0002] The use of wireless communication systems is growing rapidly. In recent years, wireless devices such as smart phones and tablet computers have become increasingly sophisticated. In addition to supporting phone calls, many mobile devices now also provide access to the Internet, email, text messaging, and navigation using the Global Positioning System (GPS), and are capable of operating sophisticated applications that utilize these functions.

[0003] Long Term Evolution (LTE) has become the technology of choice for most wireless network operators around the world to provide mobile broadband data and high-speed Internet access to their user base. LTE defines a number of downlink (DL) physical channels classified as transport or control channels to carry information blocks received from the medium access control (MAC) and higher layers. LTE also defines the number of physical layer channels for the uplink (UL).

[0004] For example, LTE defines a physical downlink shared channel (PDSCH) as a DL transport channel. PDSCH is the primary data bearing channel allocated to users on a dynamic and opportunistic basis. PDSCH carries data in a transport block (TB) corresponding to a MAC protocol data unit (PDU), which is passed from the MAC layer to the physical (PHY) layer once per transmission time interval (TTI). PDSCH is also used to transmit broadcast information such as system information blocks (SIBs) and paging messages.

[0005] As another example, LTE defines the physical downlink control channel (PDCCH) as a DL control channel that carries the resource allocation of the UE contained in the downlink control information (DCI) message. Multiple PDCCHs can be transmitted in the same subframe using control channel elements (CCEs), each of which is nine groups of four resource elements called resource element groups (REGs). PDCCH uses quadrature phase shift keying (QPSK) modulation, where four QPSK symbols are mapped to each REG. In addition, depending on the channel conditions, 1, 2, 4, or 8 CCEs can be used to ensure sufficient robustness.

[0006] In addition, LTE defines the physical uplink shared channel (PUSCH) as a UL channel shared by all devices (user equipment, UE) in a radio cell to transmit user data to the network. The scheduling of all UEs is under the control of the LTE base station (enhanced Node B or eNB). The eNB uses an uplink scheduling grant (DCI format 0) to inform the UE of the resource block (RB) allocation and the modulation and coding scheme to be used. PUSCH typically supports QPSK and orthogonal amplitude modulation (QAM). In addition to user data, PUSCH also carries any control information required to decode the information, such as a transport format indicator and multiple-input multiple-output (MIMO) parameters. The control data is multiplexed with the information data before the digital Fourier transform (DFT) is unfolded.

[0007] The next telecommunication standard proposed to go beyond the current International Mobile Telecommunications Advanced (IMT-Advanced) standard is called the 5th Generation Mobile Network or 5th Generation Wireless System, or 5G for short (also called 5G-NR for 5G New Radio, also referred to as NR for short). Compared to the current LTE standard, 5G-NR proposes higher capacity for a higher density of mobile broadband users, while supporting device-to-device ultra-reliable and massive machine communications, as well as lower latency and lower battery consumption. In addition, the 5G-NR standard may allow for less restrictive UE scheduling than the current LTE standard. Therefore, efforts are underway to take advantage of the higher throughput possible at higher frequencies in the ongoing development of 5G-NR. Summary of the invention

[0008] Embodiments relate to apparatus, systems, and methods for 5G NR voice call fallback to Evolved Packet System (EPS) enhancements.

[0009] In some embodiments, a wireless device (e.g., such as a user equipment device (UE)) may be configured to camp on a cell (e.g., such as a gNB 604) of a 5G NR network, including performing one or more of an IMS registration process or an IMS SIP invitation process using an IMS serving the 5G NR network. The UE may be configured to initiate a voice call (e.g., over the 5G NR network) and determine that the voice call cannot be established over the 5G NR network. In response, the UE may be configured to perform one of a TAU process or a connection process with a cell of a 4G network, and the IMS may be transferred to the 4G network during one of the TAU process or the connection process. The UE may be configured to omit one or more of an IMS registration process or a SIP invitation process using the IMS before establishing a voice call over the 4G network. In some embodiments, in response to determining that the UE is prohibited from accessing the 4G network, the UE may be configured to transition back to the 5G NR network and transmit a SIP cancel request to the 5G NR network to allow the context associated with the UE to be cleared from the IMS.

[0010] In some embodiments, a wireless device (e.g., such as a user equipment device (UE)) may be configured to camp on a cell (e.g., such as a gNB 604) of a 5G NR network, including performing one or more of an IMS registration process or an IMS SIP invitation process using an IMS serving the 5G NR network. The UE may be configured to collect a list of 4G frequencies and cells that support VoPS co-located with a 5G NR cell in response to determining that the 5G NR network does not support voice calls. The frequencies and cells may be collected based on at least one of a frequency sent by the 5G NR network in redirection and / or handover during EPS fallback, a past 4G connection process and / or TAU process performed on a 4G cell co-located with the 5G NR cell, and / or a 4G frequency list received from an AP Assisted Cell Search (APACS) server. The UE may be configured to use the collected 4G frequencies to search for and camp on a selected 4G cell when initiating a voice call to continue the voice call.

[0011] The techniques described herein may be implemented in and / or used with a number of different types of devices, including, but not limited to, any of cellular telephones, tablet computers, wearable computing devices, portable media players, and a variety of other computing devices.

[0012] The present invention is intended to provide a brief overview of some of the themes described in this document. Therefore, it should be understood that the above features are only examples and should not be interpreted as narrowing the scope or essence of the themes described in this invention in any way. Other features, aspects and advantages of the themes described herein will become apparent through the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A better understanding of the present subject matter may be obtained when the following detailed description of various embodiments is considered in conjunction with the following drawings, in which:

[0014] Figure 1A An exemplary wireless communication system is shown in accordance with some embodiments.

[0015] Figure 1B Examples of base stations (BSs) and access points in communication with user equipment (UE) devices are shown in accordance with some embodiments.

[0016] Figure 2 An exemplary simplified block diagram of a WLAN access point (AP) is shown in accordance with some embodiments.

[0017] Figure 3An example block diagram of a UE according to some embodiments is shown.

[0018] Figure 4 An example block diagram of a BS according to some embodiments is shown.

[0019] Figure 5 An example block diagram of cellular communication circuitry is shown according to some embodiments.

[0020] Fig. 6A An example of the connection between the EPC network, LTE base stations (eNBs), and 5G NR base stations (gNBs) is shown.

[0021] Figure 6B An example of a protocol stack for eNB and gNB is shown.

[0022] Fig. 7A An example of a 5G network architecture according to some embodiments is shown, which combines 3GPP (e.g., cellular) and non-3GPP (e.g., non-cellular) access in the 5G CN.

[0023] Figure 7B An example of a 5G network architecture according to some embodiments is shown, which combines dual 3GPP (e.g., LTE and 5G NR) access and non-3GPP access in the 5G CN.

[0024] Figure 8 An example of a baseband processor architecture for a UE according to some embodiments is shown.

[0025] 9A to 9C An example of a connection architecture between a mobile network, a 4G network, and a 5G network is shown.

[0026] Fig. 10A An example of a call flow for VoNR is shown.

[0027] Fig. 10B An example of a call flow for EPS fallback when the N26 interface is not supported is shown.

[0028] FIG. 11A to FIG. 11D An example of EPS fallback when 5G NR dedicated resources are not available according to some embodiments is shown.

[0029] FIG. 12A to FIG. 12D An example of EPS fallback when a voice call is barred at call setup is shown according to some embodiments.

[0030] Fig.13 and Fig.14 A block diagram illustrating an example of a method for EPS fallback when establishing a voice call while residing on a 5G network according to some embodiments.

[0031] Although the features described herein are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and described in detail herein. However, it should be understood that the drawings and detailed description thereof are not intended to limit this document to the specific forms disclosed, but on the contrary, their purpose is to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the subject matter as defined by the appended claims. DETAILED DESCRIPTION

[0032] the term

[0033] The following is a glossary of terms used in this disclosure:

[0034] Memory medium - any of various types of non-transitory memory devices or storage devices. The term "memory medium" is intended to include installation media, such as CD-ROM, floppy disk or tape devices; computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory such as flash memory, magnetic media, for example, hard disk drive or optical storage device; registers or other similar types of memory elements, etc. The memory medium may also include other types of non-transitory memory or combinations thereof. In addition, the memory medium may be located in the first computer system executing the program, or may be located in a different second computer system connected to the first computer system via a network such as the Internet. In the latter case, the second computer system may provide program instructions to the first computer for execution. The term "memory medium" may include two or more memory media that may reside in different locations in different computer systems connected, for example, via a network. The memory medium may store program instructions (e.g., expressed as a computer program) that may be executed by one or more processors.

[0035] Carrier Medium—storage media as described above, and physical transmission media such as a bus, network, and / or other physical transmission media that transport signals such as electrical, electromagnetic or digital signals.

[0036] Programmable hardware element - includes various hardware devices that include multiple programmable function blocks connected via programmable interconnects. Examples include FPGA (field programmable gate array), PLD (programmable logic device), FPOA (field programmable object array), and CPLD (complex PLD). Programmable function blocks can vary from fine-grained (combinational logic unit or lookup table) to coarse-grained (arithmetic logic unit or processor core). Programmable hardware elements may also be referred to as "configurable logic units".

[0037] Computer System - Any of various types of computing or processing systems, including a personal computer system (PC), a mainframe computer system, a workstation, a network appliance, an Internet appliance, a personal digital assistant (PDA), a television system, a grid computing system, or other devices or combinations of devices. In general, the term "computer system" can be broadly defined to encompass any device (or combination of devices) having at least one processor that executes instructions from a memory medium.

[0038] User Equipment (UE) (or "UE device") - any of various types of computer system devices that are mobile or portable and that perform wireless communications. Examples of UE devices include mobile phones or smart phones (e.g., iPhone TM , based on Android TM phones), portable gaming devices (e.g., Nintendo DS TM , PlayStation Portable TM 、Gameboy Advance TM , iPhone TM ), laptop computers, wearable devices (e.g., smart watches, smart glasses), personal digital assistants, portable Internet devices, music players, data storage devices or other handheld devices, etc. In general, the term "UE" or "UE device" can be broadly defined to cover any electronic device, computing device and / or telecommunication device (or combination of devices) that is convenient for a user to carry and capable of wireless communication.

[0039] Base Station—The term “base station” has the full breadth of its ordinary meaning and includes at least a wireless communication station that is installed at a fixed location and used to communicate as part of a wireless telephone system or radio system.

[0040] Processing element - refers to various elements or combinations of elements that are capable of performing functions in a device such as user equipment or cellular network equipment. Processing elements may include, for example, processors and associated memory, portions or circuits of individual processor cores, entire processor cores, processor arrays, circuits such as ASICs (application specific integrated circuits), programmable hardware elements such as field programmable gate arrays (FPGAs), and any of the above combinations.

[0041] Channel - a medium used to transmit information from a sender (transmitter) to a receiver. It should be noted that since the characteristics of the term "channel" may vary according to different wireless protocols, the term "channel" used in the present invention may be considered to be used in a manner that conforms to the standards of the type of device to which the term is used. In some standards, the channel width may be variable (e.g., depending on device capabilities, frequency band conditions, etc.). For example, LTE may support scalable channel bandwidths of 1.4 MHz to 20 MHz. In contrast, a WLAN channel may be 22 MHz wide, while a Bluetooth channel may be 1 MHz wide. Other protocols and standards may include different definitions of channels. In addition, some standards may define and use multiple types of channels, such as different channels for uplink or downlink and / or different channels for different purposes such as data, control information, etc.

[0042] Frequency band—The term “frequency band” has the full breadth of its ordinary meaning and includes at least a segment of the spectrum (eg, radio frequency spectrum) in which channels are used or set aside for the same purpose.

[0043] Automatic—refers to an action or operation performed by a computer system (e.g., software executed by a computer system) or a device (e.g., a circuit, a programmable hardware element, an ASIC, etc.) without the need for user input to directly specify or perform the action or operation. Thus, the term "automatic" is in contrast to a user manually performing or specifying an action, where the user provides input to directly perform the action. An automatic process may be initiated by input provided by a user, but subsequent actions performed "automatically" are not specified by the user, i.e., are not performed "manually," where the user specifies each action to be performed. For example, a user filling out an electronic form by selecting each field and providing input specifying information (e.g., by typing in information, selecting checkboxes, radio selections, etc.) is manually filling out the form, even though the computer system must update the form in response to the user action. The form may be automatically filled out by a computer system, where the computer system (e.g., software executed on the computer system) analyzes the fields of the form and fills out the form without any user input specifying the answers to the fields. As indicated above, a user may invoke automatic filling out of a form, but not participate in the actual filling out of the form (e.g., the user does not manually specify the answers to the fields but rather they are automatically completed). This specification provides various examples of operations that are automatically performed in response to actions taken by a user.

[0044] Approximately - refers to a value that is close to a correct or exact value. For example, approximately can refer to a value that is within 1% to 10% of an exact (or desired) value. However, it should be noted that the actual threshold value (or tolerance) may depend on the application. For example, in some embodiments, "approximately" may mean within 0.1% of some specified or desired value, while in various other embodiments, the threshold value may be, for example, 2%, 3%, 5%, etc., depending on the expectations or requirements of a particular application.

[0045] Concurrency - refers to parallel execution or implementation, where tasks, processes, or programs are executed in an at least partially overlapping manner. For example, concurrency can be achieved using "strong" or strict parallelism, where tasks are executed (at least partially) in parallel on respective computing elements, or using "weak parallelism", where tasks are executed in an interleaved manner (e.g., by time multiplexing of execution threads).

[0046] Various components may be described as being "configured to" perform one or more tasks. In such environments, "configured to" is a broad statement that generally means "having a structure" that performs one or more tasks during operation. Thus, even when the component is not currently performing the task, the component can be configured to perform the task (for example, a set of electrical conductors can be configured to electrically connect a module to another module even when the two modules are not connected). In some environments, "configured to" can be a broad statement that generally means "having a circuit system that performs one or more tasks during operation." Thus, even when the component is not currently turned on, the component can be configured to perform the task. Typically, the circuits that form the structure corresponding to "configured to" may include hardware circuits.

[0047] For ease of description, various components may be described as performing one or more tasks. Such descriptions should be interpreted as including the phrase "configured to". The description of a component being configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. §112(f) interpretation of that component.

[0048] Figure 1A and Figure 1B -Communication system

[0049] Figure 1A A simplified exemplary wireless communication system according to some embodiments is shown. Note that the system of FIG. 1 is only one example of a possible system, and features of the present disclosure may be implemented in any of a variety of systems as desired.

[0050] As shown, the exemplary wireless communication system includes a base station 102A, which communicates with one or more user equipment 106A, user equipment 106B to user equipment 106N, etc. through a transmission medium. Each user equipment may be referred to as a "user equipment" (UE) in this article. Therefore, user equipment 106 is referred to as UE or UE device.

[0051] The base station (BS) 102A may be a base transceiver station (BTS) or a cell site ("cellular base station") and may include hardware that enables wireless communications with the UEs 106A through 106N.

[0052] The communication area (or coverage area) of a base station may be referred to as a "cell". The base station 102A and the UE 106 may be configured to communicate over a transmission medium using any of a variety of radio access technologies (RATs), which are also referred to as wireless communication technologies or telecommunication standards, such as GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, Advanced LTE (LTE-A), 5G New Radio (5G NR), HSPA, 3GPP2CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), and the like. Note that if the base station 102A is implemented in the context of LTE, it may alternatively be referred to as an "eNodeB" or "eNB". Note that if the base station 102A is implemented in the context of 5G NR, it may alternatively be referred to as a "gNodeB" or "gNB".

[0053] As shown, base station 102A may also be configured to communicate with network 100 (e.g., a cellular service provider's core network, a telecommunications network such as a public switched telephone network (PSTN), and / or the Internet, among other possibilities). Thus, base station 102A may facilitate communications between user devices and / or between user devices and network 100. In particular, cellular base station 102A may provide UE 106 with various communication capabilities, such as voice, SMS, and / or data services.

[0054] Base station 102A and other similar base stations (such as base stations 102B...102N) operating according to the same or different cellular communication standards can therefore be provided as a network of cells that can provide continuous or nearly continuous overlapping service to UE 106A-N and similar devices over a geographic area via one or more cellular communication standards.

[0055] Thus, while base station 102A may act as a "serving cell" for UEs 106A-N as shown in FIG. 1 , each UE 106 may also be able to receive signals from (and possibly be within communication range of) one or more other cells (which may be provided by base stations 102B-N and / or any other base stations), which may be referred to as "neighboring cells." Such cells may also be able to facilitate communications between user devices and / or between user devices and network 100. Such cells may include "macro" cells, "micro" cells, "pico" cells, and / or cells of any various other granularity that provide service area sizes. For example, base stations 102A-B shown in FIG. 1 may be macro cells, while base station 102N may be a micro cell. Other configurations are also possible.

[0056] In some embodiments, base station 102A may be a next generation base station, e.g., a 5G New Radio (5G NR) base station or "gNB". In some embodiments, a gNB may be connected to a legacy Evolved Packet Core (EPC) network and / or to a New Radio Communications Core (NRC) network. In addition, a gNB cell may include one or more Transition and Reception Points (TRPs). In addition, a UE capable of operating in accordance with 5G NR may be connected to one or more TRPs within one or more gNBs.

[0057] It should be noted that UE 106 is capable of communicating using multiple wireless communication standards. For example, in addition to at least one cellular communication protocol (e.g., GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interface), LTE, LTE-A, 5G NR, HSPA, 3GPP2CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), etc.), UE 106 can be configured to communicate using wireless networking (e.g., Wi-Fi) and / or peer-to-peer wireless communication protocols (e.g., Bluetooth, Wi-Fi peer-to-peer, etc.). If desired, UE 106 can also or alternatively be configured to communicate using one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one or more mobile television broadcast standards (e.g., ATSC-M / H or DVB-H), and / or any other wireless communication protocols. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0058] Figure 1BA user equipment 106 (e.g., one of device 106A through device 106N) is shown in communication with a base station 102 and an access point 112 according to some embodiments. The UE 106 may be a device having cellular communication capabilities and non-cellular communication capabilities (e.g., Bluetooth, Wi-Fi, etc.), such as a mobile phone, a handheld device, a computer or tablet, or virtually any type of wireless device.

[0059] UE 106 may include a processor configured to execute program instructions stored in a memory. UE 106 may perform any of the method embodiments of the present invention by executing such stored instructions. Alternatively or in addition, UE 106 may include a programmable hardware element, such as a field programmable gate array (FPGA) configured to perform any of the method embodiments of the present invention or any part of any of the method embodiments of the present invention.

[0060] UE 106 may include one or more antennas for communicating using one or more wireless communication protocols or technologies. In some embodiments, UE 106 may be configured to communicate using, for example, CDMA2000 (1xRTT / 1xEV-DO / HRPD / eHRPD), LTE / Advanced LTE, or 5G NR using a single shared radio component and / or GSM, LTE, Advanced LTE, or 5G Nr using a single shared radio component. The shared radio may be coupled to a single antenna, or may be coupled to multiple antennas (e.g., for MIMO) for performing wireless communications. Typically, the radio component may include any combination of a baseband processor, an analog radio frequency (RF) signal processing circuit (e.g., including filters, mixers, oscillators, amplifiers, etc.), or a digital processing circuit (e.g., for digital modulation and other digital processing). Similarly, the radio component may use the aforementioned hardware to implement one or more receive chains and transmit chains. For example, UE106 may share one or more parts of a receive chain and / or transmit chain between multiple wireless communication technologies such as those discussed above.

[0061] In some embodiments, UE 106 may include a separate transmit chain and / or receive chain (e.g., including separate antennas and other radio components) for each wireless communication protocol configured to communicate with it. As another possibility, UE 106 may include one or more radio components shared between multiple wireless communication protocols, and one or more radio components used uniquely by a single wireless communication protocol. For example, UE 106 may include a shared radio component for communicating using either LTE or 5GNR (or LTE or 1xRTT, or LTE or GSM), and a separate radio component for communicating using each of Wi-Fi and Bluetooth. Other configurations are also possible.

[0062] Figure 2 —Access Point Block Diagram

[0063] Figure 2 An exemplary block diagram of an access point (AP) 112 is shown. Note that Figure 2 The block diagram of the AP 112 is only one example of a possible system. As shown, the AP 112 may include a processor 204 that may execute program instructions for the AP 112. The processor 204 may also be coupled (directly or indirectly) to a memory management unit (MMU) 240 or other circuit or device, which may be configured to receive addresses from the processor 204 and convert these addresses to locations in memory (e.g., memory 260 and read-only memory (ROM) 250).

[0064] AP 112 may include at least one network port 270. Network port 270 may be configured to couple to a wired network and provide access to the Internet to multiple devices such as UE 106. For example, network port 270 (or an additional network port) may be configured to couple to a local network, such as a home network or an enterprise network. For example, port 270 may be an Ethernet port. The local network may provide a connection to an additional network such as the Internet.

[0065] The AP 112 may include at least one antenna 234, which may be configured to function as a wireless transceiver and may be further configured to communicate with the UE 106 via the wireless communication circuit 230. The antenna 234 communicates with the wireless communication circuit 230 via a communication chain 232. The communication chain 232 may include one or more receive chains, one or more transmit chains, or both. The wireless communication circuit 230 may be configured to communicate via Wi-Fi or WLAN (e.g., 802.11). For example, when the AP is co-located with a base station in the case of a small cell, or in other cases where it may be desirable for the AP 112 to communicate via a variety of different wireless communication technologies, the wireless communication circuit 230 may also or alternatively be configured to communicate via various other wireless communication technologies, including, but not limited to, 5G NR, Long Term Evolution (LTE), Advanced LTE (LTE-A), Global System for Mobile (GSM), Wideband Code Division Multiple Access (WCDMA), CDMA2000, etc.

[0066] In some embodiments, as further described below, AP 112 may be configured to perform the method for 5G NR voice call fallback to Evolved Packet System (EPS) enhancements as further described herein.

[0067] Figure 3 —UE block diagram

[0068] Figure 3 An exemplary simplified block diagram of a communication device 106 according to some embodiments is shown. Note that Figure 3 The block diagram of the communication device is only an example of a possible communication device. According to the embodiment, in addition to other devices, the communication device 106 can be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (such as a laptop, a notebook or a portable computing device), a tablet computer and / or a combination of devices. As shown in the figure, the communication device 106 may include a group of components 300 configured to perform core functions. For example, the group of components can be implemented as a system on a chip (SOC), which may include parts for various purposes. Alternatively, the group of components 300 can be implemented as a separate component or a group of components for various purposes. This group of components 300 can be (for example, communicatively; directly or indirectly) coupled to various other circuits of the communication device 106.

[0069] For example, the communication device 106 may include various types of memory (e.g., including NAND flash memory 310), input / output interfaces such as a connector I / F 320 (e.g., for connecting to a computer system; a docking station; a charging station; an input device such as a microphone, a camera, a keyboard; an output device such as a speaker; etc.), a display 360 that may be integrated with the communication device 106 or external to the communication device 106, and cellular communication circuits 330 such as for 5G NR, LTE, GSM, etc., and short-range to medium-range wireless communication circuits 329 (e.g., Bluetooth TM In some embodiments, the communication device 106 may include wired communication circuitry (not shown), such as, for example, a network interface card for Ethernet.

[0070] Cellular communication circuitry 330 may be (e.g., communicatively; directly or indirectly) coupled to one or more antennas, such as antennas 335 and 336 as shown. Short-range to medium-range wireless communication circuitry 329 may also be (e.g., communicatively; directly or indirectly) coupled to one or more antennas, such as antennas 337 and 338 as shown. Alternatively, short-range to medium-range wireless communication circuitry 329 may be (e.g., communicatively; directly or indirectly) coupled to antennas 335 and 336 in addition to or in lieu of being (e.g., communicatively; directly or indirectly) coupled to antennas 337 and 338. Short-range to medium-range wireless communication circuitry 329 and / or cellular communication circuitry 330 may include multiple receive chains and / or multiple transmit chains for receiving and / or transmitting multiple spatial streams, such as in a multiple-input-multiple-output (MIMO) configuration.

[0071] In some embodiments, as further described below, the cellular communication circuit 330 may include dedicated receive chains (including and / or coupled to (e.g., communicatively; directly or indirectly) dedicated processors and / or radio components) for multiple RATs (e.g., a first receive chain for LTE and a second receive chain for 5G NR). In addition, in some embodiments, the cellular communication circuit 330 may include a single transmit chain that can switch between radio components dedicated to specific RATs. For example, a first radio component may be dedicated to a first RAT, such as LTE, and may communicate with a dedicated receive chain and a transmit chain shared with an additional radio component, such as a second radio component that may be dedicated to a second RAT (e.g., 5G NR) and may communicate with the dedicated receive chain and the shared transmit chain.

[0072] The communication device 106 may also include and / or be configured for use with one or more user interface elements. The user interface elements may include various elements such as a display 360 (which may be a touch screen display), a keyboard (which may be a separate keyboard or may be implemented as part of a touch screen display), a mouse, a microphone and / or speakers, one or more cameras, one or more buttons, and / or any of a variety of other elements capable of providing information to a user and / or receiving or interpreting user input.

[0073] The communication device 106 may also include one or more smart cards 345 having SIM (Subscriber Identity Module) functionality, such as one or more UICC cards (one or more Universal Integrated Circuit Cards) 345 .

[0074] As shown, the SOC 300 may include a processor 302 that may execute program instructions for the communication device 106 and a display circuit 304 that may perform graphics processing and provide display signals to a display 360. The one or more processors 302 may also be coupled to a memory management unit (MMU) 340 (which may be configured to receive addresses from the one or more processors 302 and convert those addresses to locations in a memory (e.g., memory 306, read-only memory (ROM) 350, NAND flash memory 310)) and / or to other circuits or devices (such as display circuit 304, short-range to medium-range wireless communication circuit 329, cellular communication circuit 330, connector I / F 320, and / or display 360). The MMU 340 may be configured to perform memory protection and page table translation or setup. In some embodiments, the MMU 340 may be included as part of the processor 302.

[0075] As described above, the communication device 106 may be configured to communicate using wireless and / or wired communication circuits. The communication device 106 may be configured to perform the method for 5G NR voice call fallback to Evolved Packet System (EPS) enhancement as further described herein.

[0076] As described herein, the communication device 106 may include hardware and software components for implementing the above-described features of the communication device 106 to send a scheduling profile for power saving to the network. The processor 302 of the communication device 106 may be configured to implement some or all of the features described in the present invention, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), the processor 302 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit). Alternatively (or in addition), in combination with one or more of the other components 300, 304, 306, 310, 320, 329, 330, 340, 345, 350, 360, the processor 302 of the communication device 106 may be configured to implement some or all of the features described in the present invention.

[0077] In addition, as described in the present invention, processor 302 may include one or more processing elements. Therefore, processor 302 may include one or more integrated circuits (ICs) configured to perform the functions of processor 302. In addition, each integrated circuit may include circuits (e.g., first circuits, second circuits, etc.) configured to perform the functions of one or more processors 302.

[0078] Further, as described herein, the cellular communication circuit 330 and the short-range to medium-range wireless communication circuit 329 may each include one or more processing elements. In other words, one or more processing elements may be included in the cellular communication circuit 330, and similarly, one or more processing elements may be included in the short-range to medium-range wireless communication circuit 329. Thus, the cellular communication circuit 330 may include one or more integrated circuits (ICs) configured to perform the functions of the cellular communication circuit 330. Furthermore, each integrated circuit may include a circuit (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of the cellular communication circuit 330. Similarly, the short-range to medium-range wireless communication circuit 329 may include one or more ICs configured to perform the functions of the short-range to medium-range wireless communication circuit 329. Furthermore, each integrated circuit may include a circuit (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of the short-range to medium-range wireless communication circuit 329.

[0079] Figure 4 —Block diagram of a base station

[0080] Figure 4 An exemplary block diagram of a base station 102 according to some embodiments is shown. Note that Figure 4The base station of is only one example of a possible base station. As shown, the base station 102 may include a processor 404 that may execute program instructions for the base station 102. The processor 404 may also be coupled to a memory management unit (MMU) 440 or other circuit or device, which may be configured to receive addresses from the processor 404 and convert these addresses to locations in memory (e.g., memory 460 and read-only memory (ROM) 450).

[0081] Base station 102 may include at least one network port 470. Network port 470 may be configured to couple to a telephone network and provide access to the network as described above in FIG. Figure 2 Multiple devices of the telephone network described in, such as UE device 106.

[0082] The network port 470 (or an additional network port) may also or alternatively be configured to couple to a cellular network, such as a core network of a cellular service provider. The core network may provide mobility-related services and / or other services to multiple devices, such as the UE device 106. In some cases, the network port 470 may be coupled to a telephone network via the core network, and / or the core network may provide a telephone network (e.g., in other UE devices served by the cellular service provider).

[0083] In some embodiments, base station 102 may be a next generation base station, such as a 5G New Radio (5G NR) base station, or "gNB". In such embodiments, base station 102 may be connected to a legacy evolved packet core (EPC) network and / or to an NR core (NRC) network. Furthermore, base station 102 may be considered a 5G NR cell and may include one or more transition and reception points (TRPs). Furthermore, a UE capable of operating in accordance with 5G NR may be connected to one or more TRPs within one or more gNBs.

[0084] The base station 102 may include at least one antenna 434 and possibly multiple antennas. The at least one antenna 434 may be configured to function as a wireless transceiver and may be further configured to communicate with the UE device 106 via the radio component 430. The antenna 434 communicates with the radio component 430 via a communication chain 432. The communication chain 432 may be a receive chain, a transmit chain, or both. The radio component 430 may be configured to communicate via various wireless communication standards, including but not limited to 5G NR, LTE, LTE-A, GSM, UMTS, CDMA2000, Wi-Fi, etc.

[0085] Base station 102 may be configured to perform wireless communications using multiple wireless communication standards. In some cases, base station 102 may include multiple radios that enable base station 102 to communicate according to multiple wireless communication technologies. For example, as one possibility, base station 102 may include an LTE radio component for performing communications according to LTE and a 5G NR radio component for performing communications according to 5GNR. In this case, base station 102 may be able to operate as both an LTE base station and a 5G NR base station. As another possibility, base station 102 may include a multimode radio component capable of performing communications according to any one of multiple wireless communication technologies (e.g., 5GNR and Wi-Fi, LTE and Wi-Fi, LTE and UMTS, LTE and CDMA2000, UMTS and GSM, etc.).

[0086] As further described later in the present invention, the base station 102 may include hardware and software components for implementing or supporting the implementation of the features described in the present invention. The processor 404 of the base station 102 may be configured to implement or support a portion or all of the implementation of the method described in the present invention, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, the processor 404 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit) or a combination thereof. Alternatively (or in addition), in combination with one or more of the other components 430, 432, 434, 440, 450, 460, and 470, the processor 404 of the base station 102 may be configured to implement or support a portion or all of the implementation of the features described in the present invention.

[0087] In addition, as described herein, processor 404 may be composed of one or more processing elements. In other words, one or more processing elements may be included in processor 404. Therefore, processor 404 may include one or more integrated circuits (ICs) configured to perform the functions of processor 404. In addition, each integrated circuit may include circuits (e.g., first circuits, second circuits, etc.) configured to perform the functions of one or more processors 404.

[0088] Additionally, as described herein, radio 430 may be comprised of one or more processing elements. In other words, one or more processing elements may be included in radio 430. Thus, radio 430 may include one or more integrated circuits (ICs) configured to perform the functions of radio 430. Furthermore, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of radio 430.

[0089] Figure 5 : Block diagram of a cellular communication circuit

[0090] Figure 5 An exemplary simplified block diagram of a cellular communication circuit according to some embodiments is shown. Note that Figure 5 The block diagram of the cellular communication circuit of is only one example of one possible cellular communication circuit. According to an embodiment, the cellular communication circuit 330 may be included in a communication device such as the communication device 106 described above. As described above, the communication device 106 may be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet computer, and / or a combination of devices, among other devices.

[0091] Cellular communication circuitry 330 may be (eg, communicatively; directly or indirectly) coupled to one or more antennas, such as ( Figure 3 In some embodiments, the cellular communication circuit 330 may include dedicated receive chains (including and / or coupled to (e.g., communicatively; directly or indirectly) dedicated processors and / or radio components) for multiple RATs (e.g., a first receive chain for LTE and a second receive chain for 5G NR). For example, Figure 5 As shown, cellular communication circuitry 330 may include modem 510 and modem 520. Modem 510 may be configured for communication according to a first RAT, such as, for example, LTE or LTE-A, and modem 520 may be configured for communication according to a second RAT, such as, for example, 5G NR.

[0092] As shown, the modem 510 may include one or more processors 512 and a memory 516 in communication with the processor 512. The modem 510 may communicate with a radio frequency (RF) front end 530. The RF front end 530 may include circuits for transmitting and receiving radio signals. For example, the RF front end 530 may include a receiving circuit (RX) 532 and a transmitting circuit (TX) 534. In some embodiments, the receiving circuit 532 may communicate with a downlink (DL) front end 550, which may include circuits for receiving radio signals via an antenna 335a.

[0093] Similarly, the modem 520 may include one or more processors 522 and a memory 526 in communication with the processor 522. The modem 520 may communicate with the RF front end 540. The RF front end 540 may include circuits for transmitting and receiving radio signals. For example, the RF front end 540 may include a receiving circuit 542 and a transmitting circuit 544. In some embodiments, the receiving circuit 542 may communicate with the DL front end 560, which may include circuits for receiving radio signals via the antenna 335b.

[0094] In some embodiments, the switch 570 may couple the transmit circuit 534 to an uplink (UL) front end 572. In addition, the switch 570 may couple the transmit circuit 544 to the UL front end 572. The UL front end 572 may include circuitry for transmitting radio signals via the antenna 336. Thus, when the cellular communication circuit 330 receives an instruction to transmit according to a first RAT (e.g., via a transmit chain including the transmit circuit 534 and the UL front end 572) supported by the modem 510, the switch 570 may be switched to a first state that allows the modem 510 to transmit signals according to the first RAT (e.g., via a transmit chain including the transmit circuit 534 and the UL front end 572). Similarly, when the cellular communication circuit 330 receives an instruction to transmit according to a second RAT (e.g., via a transmit chain including the transmit circuit 544 and the UL front end 572) supported by the modem 520, the switch 570 may be switched to a second state that allows the modem 520 to transmit signals according to the second RAT (e.g., via a transmit chain including the transmit circuit 544 and the UL front end 572).

[0095] In some embodiments, the cellular communication circuit 330 may be configured to perform the method for 5G NR voice call fallback to Evolved Packet System (EPS) enhancement as further described herein.

[0096] As described herein, the modem 510 may include hardware and software components for implementing the above-described features or for time-division multiplexing UL data for NSA NR operations and various other techniques described herein. For example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium), the processor 512 may be configured to implement part or all of the feature parts described herein. Alternatively (or in addition), the processor 512 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit). Alternatively (or in addition), in combination with one or more of the other components 530, 532, 534, 550, 570, 572, 335, and 336, the processor 512 may be configured to implement part or all of the feature parts described herein.

[0097] In addition, as described herein, processor 512 may include one or more processing elements. Thus, processor 512 may include one or more integrated circuits (ICs) configured to perform the functions of processor 512. In addition, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of processor 512.

[0098] As described herein, the modem 520 may include hardware and software components intended to implement the above-described features for transmitting a power-saving scheduling profile to a network, as well as various other techniques described herein. The processor 522 may be configured to implement part or all of the feature parts described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition), the processor 522 may be configured as a programmable hardware element such as an FPGA (field programmable gate array), or as an ASIC (application-specific integrated circuit). Alternatively (or additionally), in combination with one or more of the other components 540, 542, 544, 550, 570, 572, 335, and 336, the processor 522 may be configured to implement part or all of the feature parts described herein.

[0099] In addition, as described herein, processor 522 may include one or more processing elements. Thus, processor 522 may include one or more integrated circuits (ICs) configured to perform the functions of processor 522. In addition, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of processor 522.

[0100] 5G NR architecture with LTE

[0101] In some implementations, fifth generation (5G) wireless communications will initially be deployed concurrently with current wireless communications standards (e.g., LTE). For example, dual connectivity between LTE and 5G New Radio (5G NR or NR) has been specified as part of the initial deployment of NR. Figure 6A-6B As shown, the evolved packet core (EPC) network 600 may continue to communicate with the current LTE base station (e.g., eNB 602). In addition, the eNB 602 may communicate with the 5G NR base station (e.g., gNB 604), and data may be transferred between the EPC network 600 and the gNB 604. Thus, the EPC network 600 may be used (or reused), and the gNB 604 may serve as additional capacity for the user equipment, for example, to provide increased downlink throughput for the UE. In other words, LTE may be used for control plane signaling, and NR may be used for user plane signaling. Thus, LTE may be used to establish a connection with the network, and NR may be used for data services.

[0102] Figure 6B The proposed protocol stack for the eNB 602 and the gNB 604 is shown. As shown, the eNB 602 may include a medium access control (MAC) layer 632 that interfaces with the radio link control (RLC) layers 622a-622b. The RLC layer 622a may also interface with the packet data convergence protocol (PDCP) layer 612a, and the RLC layer 622b may interface with the PDCP layer 612b. Similar to the dual connectivity specified in LTE-Advanced Release 12, the PDCP layer 612a may interface with the EPC network 600 via a master cell group (MCG) bearer, while the PDCP layer 612b may interface with the EPC network 600 via a separate bearer.

[0103] In addition, as shown, the gNB 604 may include a MAC layer 634 that interfaces with the RLC layers 624a-624b. The RLC layer 624a may interface with the PDCP layer 612b of the eNB 602 via an X2 interface for information exchange and / or coordination (e.g., scheduling UEs) between the eNB 602 and the gNB 604. In addition, the RLC layer 624b may interface with the PDCP layer 614. Similar to the dual connectivity specified in Advanced LTE Release 12, the PDCP layer 614 may interface with the EPC network 600 via a secondary cell group (SCG) bearer. Therefore, the eNB 602 may be considered a master node (MeNB) and the gNB 604 may be considered a secondary node (SgNB). In some cases, the UE may be required to maintain a connection with both the MeNB and the SgNB. In such a scenario, the MeNB may be used to maintain a radio resource control (RRC) connection with the EPC, while the SgNB may be used for capacity (e.g., additional downlink and / or uplink throughput).

[0104] 5G Core Network Architecture—Interworking with Wi-Fi

[0105] In some embodiments, the 5G core network (CN) can be accessed via (or through) a cellular connection / interface (e.g., via a 3GPP communication architecture / protocol) and a non-cellular connection / interface (e.g., a non-3GPP access architecture / protocol such as a Wi-Fi connection). Fig. 7AAn example of a 5G network architecture according to some embodiments is shown, which combines 3GPP (e.g., cellular) and non-3GPP (e.g., non-cellular) access in 5G CN. As shown, a user equipment device (e.g., UE 106) can access 5G CN through both a radio access network (RAN, such as a gNB or base station 604) and an access point such as AP 112. AP 112 may include a connection to the Internet 700 and a connection to a non-3GPP interworking function (N3IWF) 702 network entity. N3IWF may include a connection to a core access and mobility management function (AMF) 704 of 5G CN. AMF 704 may include an instance of a 5G mobility management (5G MM) function associated with UE 106. In addition, RAN (e.g., gNB 604) may also have a connection to AMF 704. Therefore, 5G CN can support unified authentication on two connections and allow UE 106 access to be registered simultaneously via gNB 604 and AP 112. As shown, the AMF 704 may include one or more functional entities associated with the 5G CN (e.g., a network slice selection function (NSSF) 720, a short message service function (SMSF) 722, an application function (AF) 724, a unified data management (UDM) 726, a policy control function (PCF) 728, and / or an authentication server function (AUSF) 730). Note that these functional entities may also be supported by the session management function (SMF) 706a and SMF 706b of the 5G CN. The AMF 706 may be connected to (or communicate with) the SMF 706a. In addition, the gNB 604 may communicate with (or be connected to) a user plane function (UPF) 708a, which may also communicate with the SMF 706a. Similarly, the N3IWF 702 may communicate with the UPF 708b, which may also communicate with the SMF 706b. Both UPFs may communicate with data networks (eg, DNs 710a and 710b) and / or the Internet 700 and the IMS core network 710.

[0106] Figure 7BAn example of a 5G network architecture according to some embodiments is shown, which combines dual 3GPP (e.g., LTE and 5G NR) access and non-3GPP access in 5G CN. As shown, a user equipment device (e.g., UE 106) can access 5GCN through a radio access network (RAN, such as gNB or base station 604 or eNB or base station 602) and an access point such as AP 112. AP 112 may include a connection to the Internet 700 and a connection to the N3IWF 702 network entity. N3IWF may include a connection to the AMF 704 of the 5G CN. AMF 704 may include an instance of a 5G MM function associated with UE 106. In addition, the RAN (e.g., gNB 604) may also have a connection to AMF 704. Therefore, 5G CN can support unified authentication on two connections and allow UE 106 access to be registered simultaneously via gNB 604 and AP 112. In addition, 5G CN can support dual registration of UE on both traditional networks (e.g., LTE via base station 602) and 5G networks (e.g., via base station 604). As shown, base station 602 can have connections to mobility management entity (MME) 742 and service gateway (SGW) 744. MME 742 can have connections to both SGW 744 and AMF 704. In addition, SGW 744 can have connections to both SMF 706a and UPF 708a. As shown, AMF 704 can include one or more functional entities associated with 5G CN (e.g., NSSF 720, SMSF 722, AF 724, UDM 726, PCF 728 and / or AUSF 730). It should be noted that UDM 726 can also include home subscriber server (HSS) functions, and PCF can also include policy and charging rules functions (PCRF). It should also be noted that these functional entities can also be supported by SMF 706a and SMF 706b of 5G CN. AMF 706 can be connected to (or communicate with) SMF 706a. In addition, gNB 604 can communicate with (or be connected to) UPF 708a, which can also communicate with SMF 706a. Similarly, N3IWF702 can communicate with UPF 708b, which can also communicate with SMF 706b. Both UPFs can communicate with data networks (e.g., DN710a and 710b) and / or the Internet 700 and the IMS core network 710.

[0107] Note that in various embodiments, one or more of the above-mentioned network entities may be configured to perform methods for improving security checks in 5G NR networks, including, for example, mechanisms for 5G NR voice call fallback to Evolved Packet System (EPS) enhancements as further described herein.

[0108] Figure 8 An example of a baseband processor architecture for a UE (e.g., UE 106) according to some embodiments is shown. As described above, Figure 8 The baseband processor architecture 800 described in the figure can be implemented on one or more radio components (e.g., the radio components 329 and / or 330 described above) or modems (e.g., modems 510 and / or 520) as described above. As shown in the figure, the non-access layer 810 may include a 5G NAS 820 and a traditional NAS 850. The traditional NAS 850 may include a communication connection with a traditional access layer (AS) 870. The 5G NAS 820 may include a communication connection with a 5G AS 840 and a non-3GPP AS 830 and a Wi-Fi AS 832. The 5G NAS 820 may include functional entities associated with two access layers. Therefore, the 5G NAS820 may include multiple 5G MM entities 826 and 828 and 5G session management (SM) entities 822 and 824. The traditional NAS 850 may include functional entities such as a short message service (SMS) entity 852, an evolved packet system (EPS) session management (ESM) entity 854, a session management (SM) entity 856, an EPS mobility management (EMM) entity 858, and a mobility management (MM) / GPRS mobility management (GMM) entity 860. In addition, the traditional AS 870 may include functional entities such as an LTE AS 872, a UMTS AS 874, and / or a GSM / GPRS 876.

[0109] Therefore, the baseband processor architecture 800 allows for a common 5G-NAS for both 5G cellular and non-cellular (e.g., non-3GPP access). Note that, as shown, 5G MM can maintain a separate connection management and registration management state machine for each connection. In addition, a device (e.g., UE106) can register to a single PLMN (e.g., 5G CN) using 5G cellular access as well as non-cellular access. In addition, a device can be in a connected state in one access and in an idle state in another access, or vice versa. Finally, there may be a common 5G-MM procedure (e.g., registration, deregistration, identification, authentication, etc.) for both accesses.

[0110] It should be noted that in various embodiments, one or more of the above-mentioned functional entities of the 5G NAS and / or 5G AS may be configured to perform, for example, the method for 5G NR voice call fallback to Evolved Packet System (EPS) enhancement as further described herein.

[0111] Voice call EPS fallback enhancement

[0112] In the current implementation, a mobile station such as a user equipment device (UE) may operate in a standalone mode on a 5G radio access network such as 5G NR, or in a non-standalone mode. In standalone mode, the mobile station may have a single registration coordinated between the 5G core and the Evolved Packet System (EPS) core. For example, Fig. 9A As shown, a mobile station such as a UE 900 may maintain control plane (CP) and user plane (UP) connections with a 5G base station 910. The 5G base station 910 may maintain a control plane connection (via an NG2 interface) and a user plane connection (via an NG3 interface) with a 5G core 912. The 5G core may (optionally) interact with the EPS core 922 via an N26 interface. Such an interface between the 5G core and the EPS core may allow the mobile station to have an Internet Protocol (IP) address reservation when the mobile station moves between radio access networks (RANs). For example, when the RAN changes from 5G to 4G, the mobile station may perform a tracking area update (TAU) or a connection procedure (e.g., depending on N26 interface support) to transmit a packet data network (PDN) and IP address reservation.

[0113] Additionally, to support voice calls on a mobile station capable of working with 5G NR, current implementations provide multiple options. For example, in non-standalone mode, a mobile station may continue to conduct a Voice over LTE (VoLTE) call while supporting active Secondary Cell Group (SCG) bearers (e.g., to support data) on a user plane link with a 5G base station. For example, Fig. 9B As shown, the UE 900 may maintain control plane (CP) and user plane (UP) connections with the 4G base station 920. In addition, the UE 900 may maintain a user plane connection with the 5G base station 910. The 4G base station 910 may have both a user plane connection and a control plane connection with the 5G base station 910. In addition, the 4G base station 910 may maintain a control plane connection (via the S1-MME interface) and a user plane connection (via the S1-U interface) with the EPS core 922. The EPS core may (optionally) interact with the EPS core 922 via the N26 interface. Therefore, when a VoLTE call is made in non-standalone mode, the call may be made via the 4G network.

[0114] Alternatively, in standalone mode, if both the 5G RAN and the mobile station support it, the mobile station may continue to make NR voice (VoNR) calls. However, when the 5G RAN or the mobile station does not support VoNR, the mobile station may fall back to EPS when initiating a voice call. In such a specific implementation, if the N26 interface is supported, the mobile station may be redirected (or handed over) to a 4G base station, and a tracking area update (TAU) procedure may be performed to continue the call over VoLTE. However, if the N26 interface is not supported, the mobile station may be redirected to a 4G base station, and an LTE connection procedure (e.g., using a handover tag set) may be performed to continue the call over VoLTE. In either case, there may be a delay (sometimes significant, e.g., noticeable to the user) in voice call establishment.

[0115] As another option for wireless devices that do not support the N26 interface, they may be configured for dual registration, e.g. Fig. 9C As shown. In such implementations, the UE 900 may have independent registrations on both the 4G network and the 5G network. This may require dual transmitters (e.g., a transmitter dedicated to the 4G connection and a transmitter dedicated to the 5G connection), or the UE 900 may be configured to share a single transmitter between the connections with detuning. In such implementations, the UE 900 may use a 4G connection for voice calls (e.g., VoLTE) and a 5G connection for data (e.g., similar to a non-standalone scenario).

[0116] Fig. 10AAn example of a call flow for VoNR according to a current specific implementation is shown. As shown, at 1002, the UE 900 may perform a 5G registration process with the 5G core 912. During the process, the 5G core 912 may indicate support for IMS voice (VoIMS), for example, via a packet voice session (VoPS) parameter with a value of 1. At 1004, the UE 900 may perform an IP multimedia subsystem (IMS) protocol data unit (PDU) session establishment process with the 5G core 912. At 1006, the UE 900 may perform an IMS session initiation protocol (SIP) registration process for voice and / or short message service (SMS) support. At 1008, the UE 900 may initiate a mobile originated (MO) voice call. At 1010, the UE 900 may perform an RRC establishment process with the 5G base station 910. At 1012, the UE 900 may transmit a service request (with a service type set to data) to the 5G core 912. At 1014, the UE 900 may send a SIP invite message to the IMS 1000. At 1016, the IMS 1000 may transmit a 183 session progress message to the 5G core 912. At 1018, the 5G core 912 and the 5G base station 910 may initiate a PDU session modification to establish a flow for an IMS voice call. At 1020, the IMS 1000 and the UE 900 may establish an NR dedicated bearer for the MO voice call. At 1022, the UE 900 and the IMS 1000 may participate in an IMS voice session over NR.

[0117] Fig. 10BAn example of a call flow for EPS fallback when the N26 interface is not supported according to the current specific implementation is shown. As shown, at 1002, the UE 900 may perform a 5G registration process to the 5G core 912. During this process, the 5G core 912 may indicate support for VoIMS, for example, via a packet voice session (VoPS) parameter with a value of 1. In addition, the 5G core 912 may indicate that the N26 interface is unavailable, for example, via an interworking (IWK) N26 parameter with a value of 0. At 1004, the UE 900 may perform an IP Multimedia Subsystem (IMS) protocol data unit (PDU) session establishment process with the 5G core 912. At 1006, the UE 900 may perform an IMS session initiation protocol (SIP) registration process for voice and / or short message service (SMS) support. At 1008, the UE 900 may initiate a mobile originated (MO) voice call. At 1010, the UE 900 may perform an RRC establishment procedure with the 5G base station 910. At 1012, the UE 900 may transmit a service request (with a service type set to data) to the 5G core 912. At 1014, the UE 900 may send a SIP invite message to the IMS 1000. At 1016, the IMS 1000 may transmit a 183 session progress message to the 5G core 912. At 1018, the 5G core 912 and the 5G base station 910 may initiate a PDU session modification to establish a process for an IMS voice call. At 1030, the PDU session modification may be rejected while indicating that an IMS voice fallback to EPS is in progress. At 1032, the UE 902 may perform inter-RAT measurements. At 1034, the UE 900 may be redirected to the 4G base station 920. At 1036, the UE 900 may establish an LTE security context with the EPS core 922. At 1038, the UE may perform an LTE connection procedure through a PDN establishment with the EPS core 922. At 1040, the EPS core 922 and the UE 900 may establish an EPS dedicated bearer for the MO voice call. At 1042, the UE 900 and the IMS 1000 may participate in an IMS voice session over LTE.

[0118] As mentioned above, due to the unavailability of dedicated bearer resources for 5G NR voice in 5G RAN, most networks may not be able to use (support) VoNR, at least in the initial implementation. In such cases, the network may redirect the UE to 4G (e.g., LTE) for voice calls, which results in call initiation delays and poor user experience, especially when the N26 interface is not supported. In some cases, VoNR may not be used due to network access prohibition. In some cases, VoNR may not be used due to lower layer problems, IMS SIP message timeouts, IMS SIP rejections, IMS SIP errors, etc.

[0119] Embodiments described herein provide systems, methods, and / or mechanisms for enhancing EPS fallback when a mobile station initiates a voice call over 5G NR. In some embodiments, when falling back to EPS, the IMS registration process may be skipped (omitted). In some embodiments, when falling back to EPS, the SIP invitation process may be skipped (omitted). In some embodiments, when a voice call is triggered over 5G NR and a 5G base station (such as gNB 604) initiates a connection release process with redirection, a UE such as UE 106 may:

[0120] Ensure that the LTE cell on which the UE is camped after redirection has the same Registered Public Land Mobile Network (RPLMN) or Equivalent PLMN (E-PLMN) as the 5G NR cell from which the call was initiated;

[0121] Ensuring that the LTE cell supports VoLTE (e.g., via checking for IMS VoPS support during a Tracking Area Update (TAU) procedure); and / or

[0122] Depending on the availability of the N26 interface, once the UE camps on the redirected LTE cell, the UE may perform a TAU procedure when the N26 interface is supported, or a connection procedure when the N26 interface is not supported.

[0123] In some embodiments, the UE may avoid dual access barring checks and / or avoid access barring checks on LTE when access barring parameters are more conservative on LTE. For example, since the access barring check may have been done via NR (e.g., when initiating a voice call), the UE may not need to apply any further barring checks when initiating an RRC connection on the LTE cell as part of the voice call fallback process (e.g., for an RRC connection established to send a TAU, which may be mitigated from any barring checks). Additionally, during EPS fallback, when the UE moves from NR to LTE, the network (e.g., a 4G network) may be aware of the EPS fallback process for voice calls and may mitigate any access barring checks for the duration of the voice service.

[0124] In some embodiments, the UE may avoid access barring checks on LTE if the access barring parameters are more conservative on LTE than on NR during the EPS fallback process. For example, if the barring factor is p30 on NR (e.g., only 30 out of 100 call attempts are allowed) and the barring factor is p70 on LTE (e.g., 70 out of 100 call attempts are allowed), the UE may skip initiating any access barring checks on LTE when it is redirected to LTE as part of EPS fallback.

[0125] In some embodiments, access barring parameters for voice calls due to EPS fallback procedures may be introduced in LTE SIB-2. The access barring parameters may allow the network to select a different set of access barring parameters for native VoLTE calls initiated over LTE (as opposed to EPS fallback voice calls). For example, the access barring parameters may include: ssac-BarringForMMTEL-Voice-r12 AC-BarringConfig OPTIONAL, --Need OPTIONAL

[0126] ssac-BarringForMMTEL-Video-r12 AC-BarringConfig OPTIONAL--Need OP

[0127] ssac-BarringForMMTEL-EpsFallbackVoice-r16 AC-BarringConfigOPTIONAL,--Need OP

[0128] Therefore, the network may relax the access barring parameters for EPS fallback voice calls compared to native LTE voice calls, for example, because the network may assume that the access barring check via 5G NR has been performed.

[0129] In some embodiments, if the UE is barred from access on LTE and / or if LTE is experiencing a random access channel (RACH) failure, the UE may transition back to 5G NR and transmit a SIP cancel request (e.g., a "SIP CANCEL" message with "RELEASE_CAUSE" set to "EPS-fallback failure") to allow the IMS server to release the UE's context. In some embodiments, such action may avoid "zombie" sessions associated with the UE from lingering at the IMS server, since the IMS SIP INVITE may have been successfully sent when the UE was on 5G NR at the time of call initiation. In some embodiments, Table 7.2A.18.11-2 of Section 7.2A.18.11.2 of 3GPP TS 24.229 may be updated to reflect a cause value for EPS fallback failure of the protocol value "RELEASE_CAUSE". In some embodiments, Section U.3.1.x may be updated to reflect such changes, for example:

[0130] When the EPS fallback procedure fails due to access being barred in EPS (Access Class Barring, EAB, ACDC, or NAS signaling connection establishment) as described in 3GPP TS 24.301 [8J] or due to a lower layer failure on LTE (e.g., RACH failure), ...

[0131] In some embodiments, when access attempts to voice services are prohibited on the current 5G NR cell, the UE may use a multi-step approach to make voice calls over NR. Note that access barring in 5G NR may be broadcast in SIB-1 messages via the uac-BarringForCommon parameter and the uac-BarringPerPLMN-List parameter. In addition, the network may apply a barring factor that may be any value from p00 (all calls are barred) to p95 (5% of calls are barred), and the UE may pick a random number between 0-100, where the service is barred if the picked random number is greater than the barring factor. Note that the uac-BarringPerPLMNList parameter may apply to the entire PLMN, while uac-BarringForCommon may apply to a single cell. Thus, in some embodiments, if the uac-BarringPerPLMN-List parameter (or information element) is not included in the SIB-1 message (e.g., is not present), and the UE is barred from making voice calls as part of uac-BarringForCommon, the UE may attempt to reselect to another 5G NR cell in the same PLMN before attempting EPS fallback. In some embodiments, if the uac-BarringPerPLMN-List parameter (or information element) is present and the UE is barred for voice calls, the UE may attempt to transition (or move) to an E-PLMN in the 5G core network before attempting EPS fallback. In some embodiments, if none of the previous conditions are met and / or are possible, the UE may attempt to transition (or move) out of the 5G core network if the UE is barred from making voice calls (or voice services).

[0132] In some implementations, to mitigate call setup delays that may be associated with a UE attempting to reselect to a new cell, the UE may decide a priori to fall back to EPS for voice services (e.g., whenever an NR cell has a non-p100 access barring factor for voice services). In other words, even before the user attempts a voice call, the UE may decide to fall back to EPS in order to be on a system that reliably allows voice services over IMS.

[0133] In some embodiments, the UE may pre-select and store a random number regardless of the voice call trigger from the user. Thus, the UE may know whether the UE will be barred for voice services before the voice call is triggered. In some embodiments, when the UE detects that voice services will be barred (e.g., based on the selected random number), the UE may attempt to switch to another 5G NR cell in the same PLMN (e.g., if the current cell is barred) or switch to an E-PLMN (e.g., if the current PLMN is barred).

[0134] In some embodiments, if VoNR is not possible due to lower layer problems (e.g., such as RACH failure and / or RRC connection failure), the UE may fall back to LTE and retry the service request over LTE after experiencing the lower layer failure for a specified amount of time. In some embodiments, if the IMS SIP message times out on NR, the UE may fall back to LTE and trigger the voice call as a circuit switched fallback (CSFB), because the IMS SIP level failure may indicate a problem with the core network (e.g., if the problem is at the core network, LTE may also experience similar problems). In some embodiments, if the IMS SIP is rejected and / or if there is an IMS SIP failure on NR, the UE may fall back to LTE and initiate re-registration with IMS. In some embodiments, if the IMS SIP is rejected on LTE, the UE may move to CSFB for voice calls. In some embodiments, if the IMS SIP is rejected and / or if there is an IMS SIP failure on NR, the UE may fall back to LTE and trigger the voice call as a CSFB. In some embodiments, if the UE receives an RRC Connection Reject as part of a voice call establishment on NR, the UE may fall back to LTE and initiate the call as VoLTE.

[0135] In some embodiments, if VoNR cannot be achieved due to unavailability of user plane resources for IMS PDUs, the UE may fall back to LTE and re-initiate IMS registration over LTE followed by IMS SIP signaling for the voice call. In some embodiments, the UE may fall back to LTE based on a network response to a service request including a "PDU Session Reactivation Result" IE and a reason of "Insufficient User Plane Resources for PDU Session" for the IMS PDU. Note that such a response from the network may be a service accept or service reject response. In some embodiments, if the UE receives a network service reject message with a reject reason of any one, any combination, and / or all of "congestion", "maximum number of PUD sessions reached", and / or "restricted service area", the UE may fall back to LTE and initiate the voice call as VoLTE.

[0136] In some embodiments, if the N26 interface is not supported and VoNR is not possible (e.g., due to access barring, IMS VoPS not supported in 5G, registration acceptance, etc.; in other words, in any case that may trigger EPS fallback), the UE may switch to dual registration mode to allow IMS registration to be completed through EPS, thereby allowing the voice call to proceed as a VoLTE call. In some embodiments, this may help reduce call setup delays for voice calls because the EPS fallback phase may be eliminated.

[0137] FIG. 11A to FIG. 11D and FIG. 12A to FIG. 12D A signaling diagram of an example of a method for EPS fallback enhancement according to some embodiments is shown. The signaling shown in Figures 11 and 12 may be used with any of the systems, methods, or devices shown in the figures, in addition to other devices. In various embodiments, some of the signaling shown may be performed concurrently in a different order than shown, or may be omitted. Additional signaling may also be performed as needed.

[0138] FIG. 11A to FIG. 11DAn example of EPS fallback when 5G NR dedicated resources are not available according to some embodiments is shown. At 1102, a UE 106, which may include a baseband layer (e.g., a radio component 330) and an application layer (e.g., a processor 302) (e.g., as described herein), may initiate a registration process to a 5G network 1164. The 5G network 1104 may include one or more base stations, such as gNB 604, and may operate according to a 3GPP fifth generation new radio (5G NR or NR) radio access technology (RAT). During the registration process, the 5G network 1164 may indicate that VoNR is supported and that the N26 interface is supported. At 1104, the baseband layer may send access barring parameters (e.g., a barring factor and / or a barring time) for a voice call originated by a mobile station to the application layer. At 1106, the baseband processor may perform an IMS default PDU session establishment with the 5G network 1164. At 1108, the application layer may perform an IMS SIP registration for voice and / or SMS and receive NR cell information. At 1110, the application layer may initiate a voice call originated by the mobile station. At 1111, the UE 106 may perform an access barring check on the 5G NW 1104. At 1112, assuming that the UE 106 passes the barring check, the baseband layer may perform an RRC establishment process with the 5G network 1164. The baseband layer may indicate the cause of the RRC establishment process as a voice call originated by the mobile station, and may also initiate a service request with the service type set to data. At 1114, the application layer may perform a SIP invitation process with the IMS 1100 and provide NR cell information. At 1116, the IMS 1100 may send a 183 session progress message to the 5G network 1164. The 183 session progress message may indicate that the 5G NR dedicated service quality is not available. At 1118, the 5G network 1164 may send an RRC connection release message to the baseband layer of the UE 106. The RRC connection release may include a redirection to the LTE indication. At 1120, the baseband processor may send an update including the LTE cell information to the application layer. In some embodiments, at 1121, the application layer may perform an access barring check on the 4G network 1162 (note that in some embodiments, for example, as described herein, the application layer may skip such an access barring check). At 1122, the baseband processor may perform a tracking area update (TAU) procedure and an RRC establishment procedure with the 4G network 1162. In some embodiments, the IMS context and Internet PDN of the UE 106 may be transmitted to the 4G network 1162. In some embodiments, the TAU procedure may include a subsequent request bit set to 1. At 1124, the application layer may perform an IMS SIP registration for voice and / or SMS and receive the LTE cell information. At 1126, the application layer may perform a SIP invitation procedure with the IMS 1100 and provide the LTE cell information.Note that in some implementations, UE 106 may skip one or both of the IMS SIP registration at 1124 and / or the SIP invitation process at 1126 (eg, as described in the example of FIG. 1 ). FIG. 11B to FIG. 11D ). At 1128, the 4G NW 1128 may perform EPS bearer establishment with the baseband layer. At 1130, the baseband layer may pass quality of service information to the application layer. At 1132, the application layer may establish an audio session with the baseband layer. At 1134, the application layer may make an IMS VoLTE call with the 4G network 1162. At 1136, the 4G network 1162 may deactivate the EPS bearer, and at 1138, the application layer may indicate the end of the voice call to the baseband layer. At 1140, the baseband layer may initiate a (fast return to NR) FRNR process with the 5G network 1164 to return to the NR network.

[0139] FIG. 12A to FIG. 12DAn example of EPS fallback when a voice call is prohibited at call establishment according to some embodiments is shown. At 1202, a UE 106, which may include a baseband layer (e.g., a radio component 330) and an application layer (e.g., a processor 302) (e.g., as described herein), may initiate a registration process to a 5G network 1164. The 5G network 1204 may include one or more base stations, such as gNB 604, and may operate according to a 3GPP fifth generation new radio (5G NR or NR) radio access technology (RAT). During the registration process, the 5G network 1164 may indicate that VoNR is supported and that the N26 interface is supported. At 1204, the baseband layer may send access prohibition parameters (e.g., prohibition factor and / or prohibition time) for a voice call originated by a mobile station to the application layer. At 1206, the baseband processor may perform an IMS default PDU session establishment with the 5G network 1164. At 1208, the application layer may perform an IMS SIP registration for voice and / or SMS and receive NR cell information. At 1210, the application layer may initiate a mobile originated voice call. At 1211, the UE 106 may perform an access barring check on the 5G NW 1204. At 1212, assuming that the UE 106 does not pass the barring check, the application layer may request the baseband layer to select the next best cell / RAT. At 1213, for example, when the baseband layer is in an RRC idle state, the baseband layer may determine whether to move to another NR cell or downgrade to LTE. In some embodiments, when the baseband layer is in an RRC connected state or an inactive state, the baseband layer may trigger a local connection release before determining whether to move to another NR cell or downgrade to LTE. At 1220, the baseband processor may send an update including LTE cell information to the application layer. At 1222, the baseband processor may perform a tracking area update (TAU) procedure and an RRC establishment procedure with the 4G network 1162. In some embodiments, the IMS context and Internet PDN of the UE 106 may be transmitted to the 4G network 1162. In some embodiments, the TAU procedure may include a subsequent request bit set to 1. At 1224, the application layer may perform an IMS SIP registration for voice and / or SMS and receive the LTE cell information. At 1226, the application layer may perform a SIP Invite procedure with the IMS 1100 and provide the LTE cell information. Note that in some embodiments, the UE 106 may skip one or both of the IMS SIP registration at 1224 and / or the SIP Invite procedure at 1226 (e.g., as described in the example of FIG. 12). FIG. 12B to FIG. 12D). At 1228, 4GNW 1228 may perform EPS bearer establishment with the baseband layer. At 1230, the baseband layer may pass quality of service information to the application layer. At 1232, the application layer may establish an audio session with the baseband layer. At 1234, the application layer may make an IMSVoLTE call with the 4G network 1162. At 1236, the 4G network 1162 may deactivate the EPS bearer, and at 1238, the application layer may indicate the end of the voice call to the baseband layer. At 1240, the baseband layer may initiate a FRNR process with the 5G network 1164 to return to the NR network.

[0140] Fig.13 A block diagram illustrating an example of a method for Evolved Packet System (EPS) fallback when establishing a voice call while residing on a fifth generation (5G) network according to some embodiments. Fig.13 The method shown in can also be used together with any one of the system, method or device shown in the figure. In various embodiments, some of the method elements shown can be performed concurrently in an order different from the order shown, or can be omitted. Additional method elements can also be performed as required. As shown in the figure, the method can be operated as follows.

[0141] At 1302, a UE such as UE 106 may camp on a cell of a 5G network (e.g., such as gNB 604). In some embodiments, the 5G network may operate according to 5G NR. Camping on the cell may include performing one or more of an IMS registration process or an IMS SIP invitation process with an IMS serving the 5G network.

[0142] The UE may initiate a voice call at 1304. In some embodiments, the voice call may be initiated over a 5G network, e.g., as described herein.

[0143] At 1306, the UE may determine that the voice call cannot be established. In some embodiments, the UE may determine that the voice call cannot be established via the cell and / or through the 5G network. In some embodiments, determining that the voice call cannot be established may include the UE determining that the first cell has a p00 access barring parameter for voice services, for example, the first cell may bar all voice services. In some embodiments, determining that the voice call cannot be established may include the UE detecting and / or experiencing a lower layer failure on the first cell within a specified time period, and determining that the voice call cannot be established through the 5G network based on the lower layer failure occurring within the specified time period. In some embodiments, determining that the voice call cannot be established may include the UE determining that the IMS SIP message has timed out on the 5G network and indicating that the voice call will use circuit switched fallback (CSFB) while performing one of the TAU process or the connection process. In some embodiments, determining that the voice call cannot be established may include the UE determining that user plane resources are not available for an IMS protocol data unit (PDU) session. In some embodiments, determining that the voice call cannot be established may include the UE receiving a response to a service request from the 5G network, the service request including an information element indicating the result of the service request, the information element having a value indicating the cause as "user plane resources are insufficient for PDU session". In some embodiments, determining that the voice call cannot be established may include the UE receiving a network service rejection from the 5G network in response to the service request, wherein the rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

[0144] In some embodiments, determining that a voice call cannot be established may include the UE selecting a random number regardless of the voice call trigger, and comparing the random number with the access barring parameter of the first cell. In such embodiments, the UE may determine (at least in part) based on the comparison that a voice call cannot be established via the first cell. In addition, in such embodiments, the UE may determine that the first cell is prohibited from accessing the 5G network, but the public land mobile network (PLMN) associated with the UE is not prohibited from accessing the 5G network. In response, before performing one of the TAU process or the connection process, the UE may reselect to another cell in the 5G network that is in the public PLMN with the first cell. In addition, the UE may determine that the PLMN associated with the UE is prohibited from accessing the 5G network, and switch to an equivalent PLMN in the 5G network before performing one of the TAU process or the connection process.

[0145] In some embodiments, determining that the voice call cannot be established may include the UE determining that the IMS SIP message is rejected on the 5G network and initiating an IMS re-registration process on the 4G network. In such embodiments, in response to the failure of the IMS re-registration process, the UE may indicate that the voice call will use circuit switched fallback (CSFB).

[0146] At 1308, the UE may perform one of a TAU procedure or a connection procedure with a cell of the 4G network. In some embodiments, the 4G network may operate according to LTE. In some embodiments, the IMS may be transmitted to the 4G network during one of the TAU procedure or the connection procedure. In some embodiments, the TAU procedure may be performed when the 5G network indicates that the N26 interface between the 5G network and the 4G network is supported. In some embodiments, the connection procedure may be performed when the 5G indicates that the N26 interface between the 5G network and the 4G network is not supported. In some embodiments, the UE may determine that the 5G cell and the 4G cell are associated with a public registered public land mobile network (RPLMN) or an equivalent PLMN (E-PLMN) before performing one of the TAU procedure or the connection procedure. In some embodiments, the UE may determine that the 4G cell supports packet voice service (VoPS), such as VoLTE, before performing one of the TAU procedure or the connection procedure.

[0147] At 1310, the UE may omit one or more of an IMS registration process or a SIP INVITE process with IMS before establishing a voice call over the 4G network.

[0148] In some embodiments, the UE may pass an access bar check on the 5G network and, based on the access bar parameters of the 5G network being more restrictive than the access bar parameters of the 4G network, omit the access bar check on the 4G network. In some embodiments, the UE may receive access bar parameters specific to the EPS fallback process from the 4G network. In some embodiments, in response to determining that the UE is barred from accessing the 4G network, the UE may perform one or more remedial processes. For example, the UE may transition back to the 5G network and transmit a SIP cancel request to the 5G network to allow the context associated with the UE to be cleared from the IMS.

[0149] As another example of a remedial process, in some embodiments, in response to determining that the UE is prohibited from making a voice call on the 5G network, the UE may determine that the cell is prohibited from accessing the 5G network, but the public land mobile network (PLMN) associated with the UE is not prohibited from accessing the 5G network. In such embodiments, before performing one of the TAU process or the connection process, the UE may reselect to another cell in the 5G network that is in a common PLMN with the first cell.

[0150] As another example of a remedial process, in some embodiments, in response to determining that the UE is prohibited from making a voice call on the 5G network, the UE may determine that a public land mobile network (PLMN) associated with the UE is prohibited from accessing the 5G network. In such embodiments, the UE may transition to an equivalent PLMN in the 5G network before performing one of the TAU process or the connection process.

[0151] In some embodiments, as further described herein, the UE may, in response to determining that the 5G network does not support voice calls, collect a list of 4G frequencies and cells that support VoPS co-located with a 5G cell. In some embodiments, the frequencies and cells may be collected based on at least one of a frequency sent by the 5G network during EPS fallback in redirection and / or switching, a past 4G connection process and / or TAU process performed on a 4G cell co-located with a 5G cell, and / or a 4G frequency list received from an AP Assisted Cell Search (APACS) server. In addition, when initiating a voice call, the UE may use the collected 4G frequencies to search for and camp on the selected 4G cell to continue the voice call. In some embodiments, the UE may fail to camp on the selected 4G cell and remove the selected 4G cell and associated frequencies from the list.

[0152] VoLTE instead of EPS fallback

[0153] As described above, in some implementations, VoNR may not be available (not supported), so IMS voice calls may use EPS fallback or RAT fallback in standalone mode. In addition, EPS fallback may use handover or redirection of voice calls to E-UTRAN (LTE). In some cases where EPS fallback with redirection is used, the UE may have to search for an LTE cell and perform an LTE TAU process and / or connection process before continuing with the IMS voice call. Errors / delays during redirection (e.g., lost SIP messages) may cause a delay in voice call establishment of at least 2 to 4 seconds, resulting in a degraded user experience. In addition, in the case of EPS fallback with handover, the initial deployment of 5G NR may have a high NR to LTE handover failure rate, so the overall voice call performance of EPS fallback may not be as good as current VoLTE. In addition, without prior knowledge of an LTE system that supports IMS voice, using VoLTE instead of EPS fallback when independently residing on NR may cause the UE to select the wrong LTE system, which may also result in call setup failures and / or long delays.

[0154] In some embodiments, a UE such as UE 106 may cache LTE frequencies known to support VoLTE while the UE camps on a co-located NR cell in standalone mode. In some embodiments, the UE may collect VoLTE frequencies co-located with the current NR cell based on one or more of LTE frequencies sent by the NW during EPS fallback in redirection and / or handover, past LTE connection / TAU procedures completed on an LTE cell co-located with the current NR cell, and / or a list of LTE frequencies from an APACS server. In some embodiments, when a user initiates a voice call, the UE may use knowledge of available VoLTE frequencies to search for an LTE cell, camp on an LTE cell, and proceed with the IMS voice call over LTE. In some embodiments, if the UE fails to camp on the selected frequency and / or if VoLTE is not supported, the UE may remove the selected frequency from its cache list. In some embodiments, if the UE does not have a priori information of the VoLTE frequency and the UE is within NR coverage in standalone mode, the UE may revert to using enhanced 3GPP EPS fallback, for example, as described herein.

[0155] Fig.14 A block diagram of another example of a method for Evolved Packet System (EPS) fallback when establishing a voice call while residing on a fifth generation (5G) network according to some embodiments is shown. Among other devices, Fig.14 The method shown in can also be used together with any one of the system, method or device shown in the figure. In various embodiments, some of the method elements shown can be performed concurrently in an order different from the order shown, or can be omitted. Additional method elements can also be performed as required. As shown in the figure, the method can be operated as follows.

[0156] At 1402, a UE such as UE 106 may camp on a cell of a 5G network (e.g., such as gNB 604). In some embodiments, the 5G network may operate according to 5G NR. Camping on the cell may include performing one or more of an IMS registration process or an IMS SIP invitation process with an IMS serving the 5G network.

[0157] At 1404, in response to determining that the 5G network does not support voice calls, a list of 4G frequencies and cells that support VoPS co-located with the 5G cell is collected. In some embodiments, the frequencies and cells may be collected based on at least one of frequencies sent by the 5G network in redirection and / or handover during EPS fallback, past 4G connection procedures and / or TAU procedures performed on a 4G cell co-located with the 5G cell, and / or a 4G frequency list received from an AP Assisted Cell Search (APACS) server.

[0158] In some embodiments, in order to determine that a voice call cannot be established, the UE may determine that the first cell has a p00 access barring parameter for voice services, for example, the first cell may bar all voice services. In some embodiments, in order to determine that a voice call cannot be established, the UE may detect and / or experience a lower layer failure on the first cell within a specified time period, and determine that a voice call cannot be established through the 5G network based on the lower layer failure occurring within the specified time period. In some embodiments, in order to determine that a voice call cannot be established, the UE may determine that an IMS SIP message times out on the 5G network and indicates that the voice call will use a circuit switched fallback (CSFB) while performing one of the TAU process or the connection process. In some embodiments, in order to determine that a voice call cannot be established, the UE may determine that user plane resources are not available for an IMS protocol data unit (PDU) session. In some embodiments, in order to determine that a voice call cannot be established, the UE may receive a response to a service request from the 5G network, the service request including an information element indicating the result of the service request, the information element having a value indicating the cause as "user plane resources are insufficient for PDU session". In some embodiments, to determine that a voice call cannot be established, the UE may receive a network service rejection from the 5G network in response to the service request, where the rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

[0159] In some embodiments, in order to determine that a voice call cannot be established, the UE may select a random number (e.g., between 0 and 1 and / or between 0 and 100) regardless of the voice call trigger, and compare the random number with the access barring parameter of the first cell. In such embodiments, the UE may determine (at least in part) based on the comparison that a voice call cannot be established via the first cell. In addition, in such embodiments, the UE may determine that the first cell is prohibited from accessing the 5G network, but the public land mobile network (PLMN) associated with the UE is not prohibited from accessing the 5G network. In response, before performing one of the TAU process or the connection process, the UE may reselect to another cell in the 5G network that is in the public PLMN with the first cell. In addition, the UE may determine that the PLMN associated with the UE is prohibited from accessing the 5G network, and switch to an equivalent PLMN in the 5G network before performing one of the TAU process or the connection process.

[0160] In some embodiments, to determine that the voice call cannot be established, the UE may determine to reject the IMS SIP message on the 5G network and initiate an IMS re-registration process on the 4G network. In such embodiments, in response to the failure of the IMS re-registration process, the UE may indicate that the voice call will use circuit switched fallback (CSFB).

[0161] At 1406, when initiating a voice call, the UE may use the collected 4G frequencies to search for and camp on the selected 4G cell to continue the voice call. In some implementations, the UE may fail to camp on the selected 4G cell and remove the selected 4G cell and associated frequencies from the list.

[0162] In some embodiments, the UE may perform one of a TAU process or a connection process with a cell of a 4G network. In some embodiments, the 4G network may operate according to LTE. In some embodiments, the IMS may be transmitted to the 4G network during one of the TAU process or the connection process. In some embodiments, the TAU process may be performed when the 5G network indicates that the N26 interface between the 5G network and the 4G network is supported. In some embodiments, the connection process may be performed when the 5G indicates that the N26 interface between the 5G network and the 4G network is not supported. In some embodiments, the UE may determine that the 5G cell and the 4G cell are associated with a public registered public land mobile network (RPLMN) or an equivalent PLMN (E-PLMN) before performing one of the TAU process or the connection process. In some embodiments, the UE may determine that the 4G cell supports packet voice service (VoPS), such as VoLTE, before performing one of the TAU process or the connection process.

[0163] In some implementations, the UE may omit one or more of an IMS registration process or a SIP INVITE process with IMS before establishing a voice call over the 4G network.

[0164] In some embodiments, the UE may pass an access barring check on the 5G network and omit the access barring check on the 4G network based on the access barring parameters of the 5G network being more restrictive than the access barring parameters of the 4G network. In some embodiments, the UE may receive access barring parameters specific to the EPS fallback procedure from the 4G network.

[0165] In some embodiments, the UE may pass the access barring check on the 5G network and omit the access barring check on the 4G network based on the access identifier of the current process as an EPS fallback process.

[0166] Other Implementations

[0167] In some embodiments, a method for Evolved Packet System (EPS) fallback when establishing a voice call while camping on a fifth generation (5G) network may include a user equipment device (UE, such as UE 106):

[0168] Residing on a first cell of the 5G network, including performing one or more of an Internet Protocol (IP) Multimedia Subsystem (IMS) registration process or an IMS Session Initiation Protocol (SIP) invitation process using an IMS serving the 5G network;

[0169] Initiate a voice call;

[0170] Determining that a voice call cannot be established;

[0171] performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a fourth generation (4G) network co-located with and / or indicated by the 5G network, wherein the IMS is transmitted to the 4G network during one of the TAU procedure or the attach procedure; and

[0172] Before establishing a voice call over the 4G network, one or more of an IMS registration process or a SIP INVITE process with the IMS is omitted.

[0173] In some implementations, the TAU process may be performed when the 5G network indicates support for the N26 interface between the 5G network and the 4G network. In some implementations, the connection process may be performed when the 5G network indicates that the N26 interface between the 5G network and the 4G network is not supported.

[0174] In some embodiments, the method may further include the UE determining, before performing one of the TAU procedure or the connection procedure, that the first cell and the second cell are associated with a Public Registered Public Land Mobile Network (RPLMN) or an Equivalent PLMN (E-PLMN).

[0175] In some embodiments, the method may further include the UE determining that the second cell supports Voice over Packet Service (VoPS).

[0176] In some embodiments, the method may further include the UE passing an access barring check on the 5G network, and omitting the access barring check on the 4G network based on that the access barring parameters of the 5G network are more restrictive than the access barring parameters of the 4G network.

[0177] In some embodiments, the method may further include the UE receiving, from the 4G network, access barring parameters specific to the EPS fallback procedure for voice calls.

[0178] In some embodiments, the method may further include the UE transitioning back to the 5G network in response to determining that the UE is barred from accessing the 4G network, and transmitting a SIP cancel request to the 5G network to allow a context associated with the UE to be cleared from the IMS.

[0179] In some embodiments, the method may also include the UE, in response to determining that the UE is prohibited from making voice calls on the 5G network, determining that the first cell is prohibited from accessing the 5G network, but a public land mobile network (PLMN) associated with the UE is not prohibited from accessing the 5G network, and reselecting another cell in the 5G network that is in a common PLMN with the first cell before performing one of the TAU process or the connection process.

[0180] In some embodiments, the method may also include the UE, in response to determining that the UE is prohibited from making a voice call on the 5G network, determining that a public land mobile network (PLMN) associated with the UE is prohibited from accessing the 5G network, and switching to an equivalent PLMN in the 5G network before performing one of the TAU procedure or the connection procedure.

[0181] In some embodiments, the method may further include, in response to determining that the 5G network does not support voice calls, the UE collecting a list of fourth generation (4G) frequencies and cells supporting a packet voice service (VoPS) co-located with the first cell, and when initiating a voice call, using the collected 4G frequencies to search for and camp on a selected 4G cell to continue the voice call. In some embodiments, the frequencies may be collected based on at least one of the following:

[0182] The frequencies sent by the 5G network during EPS fallback in redirection and / or handover;

[0183] a past 4G connection procedure and / or a Tracking Area Update (TAU) procedure performed on a 4G cell co-located with the first cell; and / or

[0184] A list of 4G frequencies received from a crowd-sourced cell deployment database server maintained by the equipment manufacturer or some other entity.

[0185] In such embodiments, the method may further include the UE failing to camp on the selected 4G cell and removing the selected 4G cell and associated frequency from the list.

[0186] In some embodiments, determining that the voice call cannot be established may include the UE determining that the first cell has a p00 access barring parameter for voice services.

[0187] In some embodiments, determining that the voice call cannot be established may include the UE:

[0188] Random numbers are selected without considering voice call triggers;

[0189] comparing the random number with an access barring parameter of the first cell; and

[0190] Based on the comparison, it is determined that the voice call cannot be established via the first cell.

[0191] In such embodiments, the method may further include the UE:

[0192] determining that the first cell is barred from accessing the 5G network, but a public land mobile network (PLMN) associated with the UE is not barred from accessing the 5G network; and

[0193] Before performing one of the TAU procedure or the connection procedure, reselect to another cell in the 5G network that is in a common PLMN with the first cell.

[0194] In some embodiments, the method may further include the UE:

[0195] determining that a public land mobile network (PLMN) associated with the UE is prohibited from accessing the 5G network; and

[0196] Transition to an equivalent PLMN in the 5G network before performing either the TAU procedure or the connection procedure.

[0197] In some embodiments, determining that the voice call cannot be established may include the UE:

[0198] detecting and / or experiencing a lower layer failure on the first cell within a specified time period; and

[0199] Determining that a voice call cannot be established over the 5G network based on lower layer failures occurring within a specified time period.

[0200] In some embodiments, determining that the voice call cannot be established may include the UE:

[0201] Determining that IMS SIP messages time out on 5G networks; and

[0202] Indicates that the voice call will use Circuit Switched Fallback (CSFB) while performing one of the TAU procedure or the Connect procedure.

[0203] In some embodiments, determining that the voice call cannot be established may include the UE:

[0204] Determining that IMS SIP messages are rejected on 5G networks; and

[0205] Initiate the IMS re-registration process on the 4G network.

[0206] In such embodiments, the method may further include the UE indicating, in response to failure of the IMS re-registration procedure, that the voice call is to use Circuit Switched Fallback (CSFB).

[0207] In some embodiments, determining that the voice call cannot be established may include the UE determining that user plane resources are not available for an IMS protocol data unit (PDU) session.

[0208] In some embodiments, determining that the voice call cannot be established may include the UE receiving a response to a service request from the 5G network, the service request including an information element indicating a result of the service request, the information element having a value indicating the cause is "insufficient user plane resources for the PDU session."

[0209] In some embodiments, determining that the voice call cannot be established may include the UE receiving a network service rejection from the 5G network in response to the service request, wherein the rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

[0210] In some embodiments, the UE may include:

[0211] one or more antennas;

[0212] one or more radio components, wherein each of the one or more radio components is configured to perform cellular communications using at least one radio access technology (RAT); and

[0213] one or more processors coupled to the one or more radios, wherein the one or more processors and the one or more radios are configured to perform voice and / or data communications;

[0214] The one or more processors are configured to cause the UE to perform the method.

[0215] In some embodiments, a non-transitory computer-readable storage medium stores program instructions executable by a processing circuit to cause the UE to perform the method.

[0216] In some embodiments, a method for Evolved Packet System (EPS) fallback when establishing a voice call while camping on a fifth generation (5G) network may include a user equipment device (UE, such as UE 106):

[0217] Residing on a first cell of the 5G network, including performing one or more of an Internet Protocol (IP) Multimedia Subsystem (IMS) registration process or an IMS Session Initiation Protocol (SIP) invitation process using an IMS serving the 5G network;

[0218] In response to determining that the 5G network does not support voice calls, collecting a list of fourth generation (4G) frequencies and cells that support voice over packet service (VoPS) co-located with the first cell, wherein the frequencies are collected based on at least one of:

[0219] The frequencies sent by the 5G network during EPS fallback in redirection and / or handover;

[0220] a past 4G connection procedure and / or a Tracking Area Update (TAU) procedure performed on a 4G cell co-located with the first cell; and / or

[0221] A 4G frequency list received from an AP Assisted Cell Search (APACS) server; and

[0222] When a voice call is initiated, the collected 4G frequencies are used to search for and camp on the selected 4G cell to continue the voice call.

[0223] In some embodiments, the method may further include the UE:

[0224] Failure to camp on the selected 4G cell; and

[0225] The selected 4G cell and associated frequency are removed from the list.

[0226] In some embodiments, the method may further include the UE:

[0227] performing one of a Tracking Area Update (TAU) procedure or an attachment procedure using the selected cell of the 4G network; and

[0228] Before establishing a voice call over the 4G network, one or more of an IMS registration process or a SIP INVITE process with the IMS is omitted.

[0229] In such embodiments, the IMS may be transferred to the 4G network during one of the TAU process or the connection process. In some embodiments, the TAU process may be performed when the 5G network indicates support for the N26 interface between the 5G network and the 4G network. In some embodiments, the connection process is performed when the 5G indicates that the N26 interface between the 5G network and the 4G network is not supported.

[0230] In some embodiments, the method may further include the UE determining, prior to performing one of a TAU procedure or a connection procedure, that the first cell and the selected cell are associated with a Public Registered Public Land Mobile Network (RPLMN) or an Equivalent PLMN (E-PLMN).

[0231] In some embodiments, the method may further include the UE:

[0232] Through access barring checks on 5G networks; and

[0233] The access barring parameters based on the 5G network are more restrictive than those on the 4G network, and the access barring check on the 4G network is omitted.

[0234] In some embodiments, the method may further include the UE:

[0235] Through access barring checks on 5G networks; and

[0236] The access barring check on the 4G network is omitted based on the identification of the current procedure as an EPS fallback procedure.

[0237] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may also include the UE determining that the first cell has a p00 access barring parameter for voice services.

[0238] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may further include the UE:

[0239] Random numbers are selected without considering voice call triggers;

[0240] comparing the random number with an access barring parameter of the first cell; and

[0241] Based on the comparison, determining that the voice call cannot be established via the first cell. In some embodiments, the method may also include the UE:

[0242] determining that the first cell is barred from accessing the 5G network, but a public land mobile network (PLMN) associated with the UE is not barred from accessing the 5G network; and

[0243] Before performing one of the TAU procedure or the connection procedure, reselecting to another cell in the 5G network that is in a common PLMN with the first cell. In some embodiments, the method may also include the UE:

[0244] determining that a public land mobile network (PLMN) associated with the UE is prohibited from accessing the 5G network; and

[0245] Transition to an equivalent PLMN in the 5G network before performing either the TAU procedure or the connection procedure.

[0246] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may further include the UE:

[0247] detecting and / or experiencing a lower layer failure on the first cell within a specified time period; and

[0248] Determining that a voice call cannot be established over the 5G network based on lower layer failures occurring within a specified time period.

[0249] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may further include the UE:

[0250] Determining that IMS SIP messages time out on 5G networks; and

[0251] Indicates that the voice call will use Circuit Switched Fallback (CSFB) while performing one of the TAU procedure or the Connect procedure.

[0252] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may further include the UE:

[0253] Determining that IMS SIP messages are rejected on 5G networks; and

[0254] Initiating an IMS re-registration procedure on the 4G network. In some embodiments, the method may further include the UE indicating that the voice call will use circuit switched fallback (CSFB) in response to a failure of the IMS re-registration procedure.

[0255] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may also include the UE determining that user plane resources are not available for an IMS protocol data unit (PDU) session.

[0256] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may also include the UE receiving a response to the service request from the 5G network, the service request including an information element indicating the result of the service request, the information element having a value indicating the cause is "insufficient user plane resources for PDU session".

[0257] In some embodiments, in order to determine that the 5G network does not support voice calls, the method may also include the UE receiving a network service rejection from the 5G network in response to the service request, wherein the rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

[0258] In some embodiments, the method may further include the UE receiving access barring parameters specific to the EPS fallback procedure from the 4G network.

[0259] In some embodiments, the UE may include:

[0260] one or more antennas;

[0261] one or more radio components, wherein each of the one or more radio components is configured to perform cellular communications using at least one radio access technology (RAT); and

[0262] one or more processors coupled to the one or more radios, wherein the one or more processors and the one or more radios are configured to perform voice and / or data communications;

[0263] The one or more processors are configured to cause the UE to perform the method.

[0264] In some embodiments, a non-transitory computer-readable storage medium stores program instructions executable by a processing circuit to cause the UE to perform the method.

[0265] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0266] The embodiments of the present disclosure may be implemented in any of a variety of forms. For example, some embodiments may be implemented as computer-implemented methods, computer-readable storage media, or computer systems. Other embodiments may be implemented using one or more custom-designed hardware devices such as ASICs. Other embodiments may be implemented using one or more programmable hardware elements such as FPGAs.

[0267] In some embodiments, a non-transitory computer-readable storage medium may be configured such that it stores program instructions and / or data, wherein if the program instructions are executed by a computer system, the computer system is caused to perform a method, such as any one of the method embodiments described herein, or any combination of the method embodiments described herein, or any subset of any of the method embodiments described herein or any combination of such subsets.

[0268] In some embodiments, a device (e.g., UE 106) may be configured to include a processor (or a group of processors) and a memory medium, wherein the memory medium stores program instructions, wherein the processor is configured to read and execute the program instructions from the memory medium, wherein the program instructions are executable to implement any of the various method implementations described herein (or any combination of the method implementations described herein, or any subset of any of the method implementations described herein, or any combination of such subsets). The device may be implemented in any of various forms.

[0269] Although the above embodiments have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to encompass all such variations and modifications.

[0270] Priority data

[0271] This patent application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62 / 888,078, filed on August 16, 2019, and entitled “5G NR Voice Call EPS Fallback Enhancements,” which is hereby incorporated by reference in its entirety as if fully and completely set forth herein.

Claims

1. A user equipment device UE, the user equipment device comprising: one or more antennas; one or more radio components, wherein each of the one or more radio components is configured to perform cellular communications using at least one radio access technology, RAT; one or more processors coupled to the one or more radios, wherein the one or more processors and the one or more radios are configured to perform voice and / or data communications; The one or more processors are configured to cause the UE to: Residing on a first cell of a fifth generation new radio 5G NR network, comprising performing one or more of an Internet Protocol IP Multimedia Subsystem (IMS) registration procedure or an IMS Session Initiation Protocol (SIP) Invite procedure using an IMS serving the 5G NR network; After attempting to initiate a voice call, determining that the voice call cannot be established; performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a fourth generation (4G) network co-located with the 5G NR network and / or indicated by the 5G NR network, wherein during one of the TAU procedure or the attach procedure, an IMS context and an Internet packet data network (PDN) data of the UE are transmitted to the 4G network; as well as Before establishing the voice call over the 4G network, one or more of an IMS registration process or a SIP invitation process using the IMS is omitted.

2. The UE according to claim 1, The one or more processors are further configured to cause the UE to: In response to determining that the UE is prohibited from accessing the 4G network, switching back to the 5G NR network; and A SIP cancel request is transmitted to the 5G NR network to allow the context associated with the UE to be cleared from the IMS.

3. The UE according to claim 1, wherein the TAU procedure is performed when the 5G NR network indicates support for an N26 interface between the 5G NR network and the 4G network; and The connection process is performed when the 5G NR network indicates that the N26 interface between the 5G NR network and the 4G network is not supported.

4. The UE according to claim 1, The one or more processors are further configured to cause the UE to: It is determined that the first cell and the second cell are associated with a common registration public land mobile network RPLMN or an equivalent PLMN (E-PLMN) before performing one of the TAU procedure or the connection procedure.

5. The UE according to claim 1, The one or more processors are further configured to cause the UE to: It is determined that the second cell supports voice over packet service VoPS.

6. The UE according to claim 1, The one or more processors are further configured to cause the UE to: passing an access barring check on the 5G NR network; and Based on the fact that the access barring parameters of the 5G NR network are more restrictive than the access barring parameters of the 4G network, the access barring check on the 4G network is omitted.

7. The UE according to claim 1, The one or more processors are further configured to cause the UE to: Access barring parameters specific to an EPS fallback procedure for voice calls are received from the 4G network.

8. The UE according to claim 1, The one or more processors are further configured to cause the UE to: In response to determining that the UE is prohibited from making the voice call on the 5G NR network, performing at least one remedial process.

9. The UE according to claim 8, Wherein the at least one remedial process comprises at least one of the following: determining that the first cell is prohibited from accessing the 5G NR network, but a public land mobile network PLMN associated with the UE is not prohibited from accessing the 5G NR network, and reselecting to another cell in the 5G NR network that is in a common PLMN with the first cell before performing one of the TAU procedure or the connection procedure; determining that a public land mobile network PLMN associated with the UE is prohibited from accessing the 5G NR network, and switching to an equivalent PLMN in the 5G NR network before performing one of the TAU procedure or the connection procedure; or A list of fourth generation 4G frequencies and cells supporting packet voice service (VoPS) co-located with the first cell is collected, and when initiating the voice call, the collected list of 4G frequencies is used to search for and stay on the selected 4G cell to continue the voice call.

10. The UE according to claim 1, In order to determine that the voice call cannot be established, the at least one processor is further configured to cause the UE to perform at least one of the following operations: detecting and / or experiencing a lower layer failure on the first cell within a specified time period, and determining that the voice call cannot be established over the 5G NR network based on the lower layer failure occurring within the specified time period; determining that an IMS SIP message times out on the 5G NR network and indicating that the voice call will use circuit switched fallback (CSFB) while performing one of the TAU procedure or the connect procedure; determining to reject an IMS SIP message on the 5G NR network and to initiate an IMS re-registration procedure on the 4G network; Determining that user plane resources are not available for an IMS protocol data unit (PDU) session; receiving a response to the service request from the 5G NR network, the service request including an information element indicating a result of the service request, the information element having a value indicating a cause as "insufficient user plane resources for the PDU session"; or Receiving a network service rejection from the 5G NR network in response to the service request, wherein a rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

11. The UE according to claim 1, The at least one processor is further configured to cause the UE to: In response to failure of the IMS registration procedure, indicating that the voice call will use Circuit Switched Fallback (CSFB).

12. An apparatus comprising: Memory; as well as at least one processor in communication with the memory, wherein the at least one processor is configured to: Residing on a first cell of a first network, comprising performing one or more of an Internet Protocol IP Multimedia Subsystem (IMS) registration procedure or an IMS Session Initiation Protocol (SIP) invitation procedure using an IMS serving the first network; After attempting to initiate the voice call, determining that the voice call cannot be established; performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a second network co-located with and / or indicated by the first network, wherein an IMS context and Internet Packet Data Network (PDN) data of the device are transferred to the second network during one of the TAU procedure or the attach procedure; as well as switching back to the first network in response to determining that the second network is prohibited; as well as A SIP cancel request is transmitted to the first network to allow a context associated with the device to be cleared from the IMS.

13. The device according to claim 12, in, To determine that the voice call cannot be established, the at least one processor is configured to determine that the first cell has a p00 access barring parameter for voice services.

14. The device according to claim 12, in, To determine that the voice call cannot be established, the at least one processor is configured to: A random number between 0 and 1 is selected without considering the voice call trigger; comparing the random number with an access barring parameter of the first cell; as well as Based on the comparison, it is determined that the voice call cannot be established via the first cell.

15. The device according to claim 14, wherein the at least one processor is further configured to: determining that the first cell is barred from accessing the first network, but a public land mobile network PLMN associated with the apparatus is not barred from accessing the first network; and Before performing one of the TAU procedure or the connection procedure, reselect to another cell in the first network that is in a common PLMN with the first cell.

16. The device according to claim 14, wherein the at least one processor is further configured to: determining that a public land mobile network PLMN associated with the apparatus is prohibited from accessing the first network; and Transitioning to an equivalent PLMN in the first network before performing one of the TAU procedure or the attach procedure.

17. A non-transitory computer-readable storage medium storing program instructions executable by a processing circuit to cause a user equipment device UE to: Residing on a first cell of a fifth generation 5G New Radio NR network, comprising performing one or more of an Internet Protocol IP Multimedia Subsystem (IMS) registration procedure or an IMS Session Initiation Protocol (SIP) Invite procedure using an IMS serving the 5G NR network; After attempting to initiate the voice call, determining that the voice call cannot be established; performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a fourth generation (4G) network co-located with the 5G NR network and / or indicated by the 5G NR network, wherein during one of the TAU procedure or the attach procedure, an IMS context and an Internet packet data network (PDN) data of the UE are transmitted to the 4G network; as well as Before establishing the voice call over the 4G network, one or more of an IMS registration process or a SIP invitation process using the IMS is omitted.

18. The non-transitory computer readable memory medium of claim 17, The program instructions are further executable to cause the UE to: In response to determining that the UE is prohibited from accessing the 4G network, switching back to the 5G NR network; and A SIP cancel request is transmitted to the 5G NR network to allow the context associated with the UE to be cleared from the IMS.

19. The non-transitory computer readable memory medium of claim 17, In order to determine that the voice call cannot be established, the program instructions can be further executed to cause the UE to perform at least one of the following operations: detecting and / or experiencing a lower layer failure on the first cell within a specified time period, and determining that the voice call cannot be established over the 5G NR network based on the lower layer failure occurring within the specified time period; determining that an IMS SIP message times out on the 5G NR network and indicating that the voice call will use circuit switched fallback (CSFB) while performing one of the TAU procedure or the connect procedure; determining to reject an IMS SIP message on the 5G NR network and to initiate an IMS re-registration procedure on the 4G network; Determining that user plane resources are not available for an IMS protocol data unit (PDU) session; receiving a response to the service request from the 5G NR network, the service request including an information element indicating a result of the service request, the information element having a value indicating a cause as "insufficient user plane resources for the PDU session"; or Receiving a network service rejection from the 5G NR network in response to the service request, wherein a rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

20. The non-transitory computer readable memory medium of claim 17, The program instructions are further executable to cause the UE to: In response to failure of the IMS registration procedure, indicating that the voice call will use Circuit Switched Fallback (CSFB).

21. The non-transitory computer readable memory medium of claim 17, wherein the TAU procedure is performed when the 5G NR network indicates support for an N26 interface between the 5G NR network and the 4G network; and The connection process is performed when the 5G NR network indicates that the N26 interface between the 5G NR network and the 4G network is not supported.

22. The non-transitory computer readable memory medium of claim 17, The program instructions are further executable to cause the UE to: determine that the first cell and the second cell are associated with a public registration public land mobile network RPLMN or an equivalent PLMN (E-PLMN) before performing one of the TAU procedure or the connection procedure.

23. The non-transitory computer readable memory medium of claim 17, wherein the program instructions are further executable to cause the UE to: It is determined that the second cell supports voice over packet service VoPS.

24. The non-transitory computer readable memory medium of claim 17, wherein the program instructions are further executable to cause the UE to: passing an access barring check on the 5G NR network; and Based on the fact that the access barring parameters of the 5G NR network are more restrictive than the access barring parameters of the 4G network, the access barring check on the 4G network is omitted.

25. The non-transitory computer readable memory medium of claim 17, The program instructions are further executable to cause the UE to: Access barring parameters specific to an EPS fallback procedure for voice calls are received from the 4G network.

26. The non-transitory computer readable memory medium of claim 17, wherein the program instructions are further executable to cause the UE to: In response to determining that the UE is prohibited from making the voice call on the 5G NR network, performing at least one remedial process.

27. The non-transitory computer readable memory medium of claim 26, Wherein the at least one remedial process comprises at least one of the following: determining that the first cell is prohibited from accessing the 5G NR network, but a public land mobile network PLMN associated with the UE is not prohibited from accessing the 5G NR network, and reselecting to another cell in the 5G NR network that is in a common PLMN with the first cell before performing one of the TAU procedure or the connection procedure; determining that a public land mobile network PLMN associated with the UE is prohibited from accessing the 5G NR network, and switching to an equivalent PLMN in the 5G NR network before performing one of the TAU procedure or the connection procedure; or A list of fourth generation 4G frequencies and cells supporting packet voice service (VoPS) co-located with the first cell is collected, and when initiating the voice call, the collected list of 4G frequencies is used to search for and stay on the selected 4G cell to continue the voice call.

28. A method performed by a user equipment device UE, comprising: Residing on a first cell of a fifth generation new radio 5G NR network, comprising performing one or more of an Internet Protocol IP Multimedia Subsystem (IMS) registration procedure or an IMS Session Initiation Protocol (SIP) Invite procedure using an IMS serving the 5G NR network; After attempting to initiate a voice call, determining that the voice call cannot be established; performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a fourth generation (4G) network co-located with the 5G NR network and / or indicated by the 5G NR network, wherein during one of the TAU procedure or the attach procedure, an IMS context and an Internet packet data network (PDN) data of the UE are transmitted to the 4G network; as well as Before establishing the voice call over the 4G network, one or more of an IMS registration process or a SIP invitation process using the IMS is omitted.

29. The method according to claim 28, further comprising: In response to determining that the UE is prohibited from accessing the 4G network, switching back to the 5G NR network; as well as A SIP cancel request is transmitted to the 5G NR network to allow the context associated with the UE to be cleared from the IMS.

30. The method according to claim 28, wherein the TAU procedure is performed when the 5G NR network indicates support for an N26 interface between the 5G NR network and the 4G network; and The connection process is performed when the 5G NR network indicates that the N26 interface between the 5G NR network and the 4G network is not supported.

31. The method of claim 28, further comprising: It is determined that the first cell and the second cell are associated with a common registration public land mobile network RPLMN or an equivalent PLMN (E-PLMN) before performing one of the TAU procedure or the connection procedure.

32. The method of claim 28, further comprising: It is determined that the second cell supports packet voice service VoPS.

33. The method of claim 28, further comprising: passing an access barring check on the 5G NR network; as well as Based on the fact that the access barring parameters of the 5G NR network are more restrictive than the access barring parameters of the 4G network, the access barring check on the 4G network is omitted.

34. The method of claim 28, further comprising: Access barring parameters specific to an EPS fallback procedure for voice calls are received from the 4G network.

35. The method of claim 28, further comprising: In response to determining that the UE is prohibited from making the voice call on the 5G NR network, performing at least one remedial procedure.

36. The method according to claim 35, Wherein the at least one remedial process comprises at least one of the following: determining that the first cell is prohibited from accessing the 5G NR network, but a public land mobile network PLMN associated with the UE is not prohibited from accessing the 5G NR network, and reselecting to another cell in the 5G NR network that is in a common PLMN with the first cell before performing one of the TAU procedure or the connection procedure; determining that a public land mobile network PLMN associated with the UE is prohibited from accessing the 5G NR network, and switching to an equivalent PLMN in the 5G NR network before performing one of the TAU procedure or the connection procedure; or A list of fourth generation 4G frequencies and cells supporting packet voice service (VoPS) co-located with the first cell is collected, and when initiating the voice call, the collected list of 4G frequencies is used to search for and stay on the selected 4G cell to continue the voice call.

37. The method according to claim 28, In order to determine that the voice call cannot be established, the method further includes at least one of the following operations: detecting and / or experiencing a lower layer failure on the first cell within a specified time period, and determining that the voice call cannot be established over the 5G NR network based on the lower layer failure occurring within the specified time period; determining that an IMS SIP message times out on the 5G NR network and indicating that the voice call will use circuit switched fallback (CSFB) while performing one of the TAU procedure or the connect procedure; determining to reject an IMS SIP message on the 5G NR network and to initiate an IMS re-registration procedure on the 4G network; Determining that user plane resources are not available for an IMS protocol data unit (PDU) session; receiving a response to the service request from the 5G NR network, the service request including an information element indicating a result of the service request, the information element having a value indicating a cause as "insufficient user plane resources for the PDU session"; or Receiving a network service rejection from the 5G NR network in response to the service request, wherein a rejection reason is at least one of congestion, a maximum number of PUD sessions reached, and / or a restricted service area.

38. The method of claim 28, further comprising: In response to failure of the IMS registration procedure, indicating that the voice call will use Circuit Switched Fallback (CSFB).

39. A computer program product comprising program instructions, the program instructions being executable by a processing circuit to cause a user equipment device UE to perform the operation of any of the methods of claims 28-38.

40. A method comprising causing an apparatus to: Residing on a first cell of a first network, comprising performing one or more of an Internet Protocol IP Multimedia Subsystem (IMS) registration procedure or an IMS Session Initiation Protocol (SIP) invitation procedure using an IMS serving the first network; After attempting to initiate the voice call, determining that the voice call cannot be established; performing one of a tracking area update (TAU) procedure or an attach procedure using a second cell of a second network co-located with and / or indicated by the first network, wherein an IMS context and Internet Packet Data Network (PDN) data of the device are transferred to the second network during one of the TAU procedure or the attach procedure; as well as switching back to the first network in response to determining that the second network is prohibited; as well as A SIP cancel request is transmitted to the first network to allow a context associated with the device to be cleared from the IMS.

41. The method according to claim 40, in, To determine that the voice call cannot be established, the method further includes causing the apparatus to determine that the first cell has a p00 access barring parameter for voice services.

42. The method according to claim 40, in, In order to determine that the voice call cannot be established, the method further includes causing the apparatus to: A random number between 0 and 1 is selected without considering the voice call trigger; comparing the random number with an access barring parameter of the first cell; as well as Based on the comparison, it is determined that the voice call cannot be established via the first cell.

43. The method of claim 42, further comprising causing the device to: determining that the first cell is barred from accessing the first network, but a public land mobile network PLMN associated with the apparatus is not barred from accessing the first network; and Before performing one of the TAU procedure or the connection procedure, reselect to another cell in the first network that is in a common PLMN with the first cell.

44. The method of claim 42, further comprising causing the device to: determining that a public land mobile network PLMN associated with the apparatus is prohibited from accessing the first network; and Transitioning to an equivalent PLMN in the first network before performing one of the TAU procedure or the attach procedure.

45. A non-transitory computer-readable memory medium storing program instructions executable by a processing circuit to cause an apparatus to perform the operations of any of the methods of claims 40-44.

46. ​​A computer program product comprising program instructions executable by a processing circuit to cause an apparatus to perform the operations of any of the methods of claims 40-44.

Images