WO2021237661A1

WO2021237661A1 - Voice solution for new radio (nr) device

Info

Publication number: WO2021237661A1
Application number: PCT/CN2020/093209
Authority: WO
Inventors: Haibo Liu; Bing LENG; Jian Li; Hao Zhang; Xiaomeng Lu
Original assignee: Qualcomm Incorporated
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2021-12-02

Abstract

A method for wireless communication includes attempting to register with an internet protocol multimedia subsystem (IMS) via a first network, and receiving, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration. The method also includes comparing the retry time duration with a time threshold, and, if the retry time duration is greater than the time threshold, accessing a voice service via a second network during the retry time duration.

Description

VOICE SOLUTION FOR NEW RADIO (NR) DEVICE

BACKGROUND

Field

Aspects of the present disclosure relate generally to wireless communications, and more particularly, to providing a wireless device with voice service.

Background

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on.These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include fourth generation (4G) systems such as Long-Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , or discrete Fourier transform-spread-OFDM (DFT-S-OFDM) . A wireless multiple-access communications system may include multiple base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

A wireless communications system may be connected to an internet protocol (IP) multimedia subsystem (IMS) to provide UEs with voice services (e.g., voice over IP (VoIP) , video call, etc. ) .

SUMMARY

The following presents a simplified summary of one or more implementations in order to provide a basic understanding of such implementations. This summary is not an extensive overview of all contemplated implementations and is intended to neither identify key or critical elements of all implementations nor delineate the scope of any or all implementations. Its sole purpose is to present some concepts of one or more implementations in a simplified form as a prelude to the more detailed description that is presented later.

A first aspect relates to an apparatus for wireless communication. The apparatus includes a processor, a memory coupled with the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to attempt to register with an internet protocol multimedia subsystem (IMS) via a first network, and receive, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration. The instructions are also executable by the processor to cause the apparatus to compare the retry time duration with a time threshold, and, if the retry time duration is greater than the time threshold, access a voice service via a second network during the retry time duration.

A second aspect relates to a method for wireless communication. The method includes attempting to register with an internet protocol multimedia subsystem (IMS) via a first network, and receiving, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration. The method also includes comparing the retry time duration with a time threshold, and, if the retry time duration is greater than the time threshold, accessing a voice service via a second network during the retry time duration.

A third aspect relates to an apparatus for wireless communication. The apparatus includes means for attempting to register with an internet protocol multimedia subsystem (IMS) via a first network, and means for receiving, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration. The apparatus also includes means for comparing the retry time duration with a time threshold, and means for accessing a voice service via a second network during the retry time duration if the retry time duration is greater than the time threshold.

To the accomplishment of the foregoing and related ends, the one or more implementations include the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more implementations. These aspects are indicative, however, of but a few of the various ways in which the principles of various implementations may be employed and the described implementations are intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an example of a wireless communications system according to certain aspects of the present disclosure.

FIG. 1B shows an example of a core network connected to an IMS according to certain aspects of the present disclosure.

FIG. 2 shows an exemplary architecture for a NR core network according to certain aspects of the present disclosure.

FIG. 3 shows an example of a UE capable of communicating with two or more wireless networks according to certain aspects of the present disclosure.

FIG. 4 shows an exemplary architecture for a 4G core network according to certain aspects of the present disclosure.

FIG. 5 is a flow diagram illustrating a method for accessing a voice service from an IMS via a first network according to certain aspects of the present disclosure.

FIG. 6 is a flow diagram illustrating a method for accessing a voice service via a second network in the event of an IMS registration failure according to certain aspects of the present disclosure.

FIG. 7 shows an exemplary device in which aspects of the present disclosure may be implemented according to certain aspects of the present disclosure.

FIG. 8 is a flowchart illustrating a method for wireless communication according to certain aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

FIG. 1A shows an example of a wireless communications system 100 according to certain aspects of the present disclosure. The wireless communications system 100 includes base stations 105a to 105d, UEs 115a to 115g, and a core network 130 (shown in FIG. 1B) . In some examples, the wireless communications system 100 may include a New Radio (NR) network, a Long-Term Evolution (LTE) network, or a combination thereof.

The base stations 105a to 105d may wirelessly communicate with the UEs 115a to 115g via one or more base station antennas. A base station may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology. The wireless communications system 100 may include base stations 105a to 105d of different types (e.g., macro cell base stations and/or small cell base stations) . The UEs 115a to 115g described herein may be able to communicate with various types of base stations 105a to 105d and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

Each base station 105a to 105d may be associated with a respective geographic coverage area 110a to 110d in which communications with various UEs 115a to 115g is supported. Each base station 105a to 105d may provide communication coverage for the respective geographic coverage area 110a to 110d via communication links 125a to 125g, and a communication link between a base station 105a to 105d and a UE 115a to 115g may utilize one or more carriers. The communication links 125a to 125g shown in the wireless communications system 100 may include uplink transmissions from the UEs 115a to 115g to the base stations 105a to 105d and downlink transmissions from the base stations 105a to 105d to the UEs 115a to 115g. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

Each base station 105a to 105d may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105a to 105d may be stationary or movable. In some examples, different geographic coverage areas 110a to 110d associated with different technologies may overlap, and overlapping geographic coverage areas 110a to 110d associated with different technologies may be supported by the same base station 105a to 105d or by different base stations 105a to 105d. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different types of base stations 105a to 105d provide coverage for various geographic coverage areas 110a to 110d.

The UEs 115a to 115g may be dispersed throughout the wireless communications system 100, and each UE 115a to 115g may be stationary or mobile. A UE 115a to 115g may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client. A UE 115a to 115g may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115a to 115g may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.

The base stations 105a to 105d may communicate with the core network 130 (shown in FIG. 1B) and with one another. For example, the base stations 105a to 105d may interface with the core network 130 through backhaul links (e.g., via an S1 interface or another interface) . The base stations 105a to 105d may communicate with one another over backhaul links 134a to 134c (e.g., via an X2 interface or another interface) either directly (e.g., directly between base stations 105a to 105d) or indirectly (e.g., via the core network 130) .

The core network 130 (shown in FIG. 1B) may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, and mobility functions. The core network 130 may be an NR core network, a 4G core network (e.g., LTE core network) , or another type of core network.

FIG. 1B shows an example of UE 115a connected to base station 105b via communication link 125a. In this example, the UE 115a communicates with the core network 130 via base station 105b. However, it to be appreciated that the UE 115a may communicate with the core network 130 via any one of the

other base stations

105a, 105c and 105d. For example, the UE 115a may be handed over from base station 105b to another one of the

base stations

105a, 105c and 105d for communication with the core network 130 when the UE 115a moves from the coverage area 110b of base station 105b to the

coverage area

110a, 110b and 110d of the other one of the

base stations

105a, 105c and 105d.

In the example in FIG. 1B, the core network 130 is connected to an IMS 140 to provide the UE 115a with voice services (e.g., voice over IP (VoIP) , video call, and/or other IP-based voice services) . To access voice services, the UE 115a needs to register with the IMS 140, as discussed further below. After registering with the IMS 140, the UE 115a is able to access voice services from the IMS 140 through the core network 130. For the example of a voice call, the UE 115a sends voice packets to and receives voice packets from the IMS 140 through the core network 130. The core network 130 transports voice packets between the UE 115a and the IMS 140 using a packet-switched network.

FIG. 2 shows an exemplary implementation of the core network 130 for the example where the core network 130 is an NR core network. In this example, the core network 130 may include at least one access and mobility management function (AMF) 210, at least one session management function (SMF) 220, and at least one user plane function (UPF) 230. The AMF 210 and SMF 220 are part of the control plane of the core network 130 and are configured to manage control functions such as mobility, authentication, and session management. It is to be appreciated that the control plane may include additional functions, which are not shown in FIG. 2 for ease of illustration. The UPF 230 is part of a user plane of the core network 130 and is configured to transport packets (e.g., voice packets) between the UE 115a and the IMS 140.

In certain aspects, the UE 115a supports connectivity with multiple networks using multiple technologies. In this regard, FIG. 3 shows an example in which the UE 115a is able to attach to a second network. In one example, the first network discussed above with reference to FIGS. 1A, 1B and 2 is an NR network and the second network is a legacy network such as a fourth generation (4G) network (e.g., LTE network) , a third generation (3G) network (e.g., wideband code division multiple access (WCDMA) network, CDMA2000 network, etc. ) , or a second generation (2G) network (e.g., CDMA network, global system for mobile communication (GSM) network, etc. ) . The first network (e.g., NR network) includes the base stations 105a to 105d and the core network 130 discussed above. The second network includes the base stations 305a to 305c and the core network 330. The UE 115a may communicate with one or more base stations 305a to 305c in the second network via communication link 325 and communicate with the core network 330 via one or more of the base stations 305a to 305c. The UE 115a may, for example, connect to the second network when the UE 115a is outside the coverage area of the first network, when the UE 115a is unable to access one or more services through the first network, etc.

FIG. 4 shows an exemplary implementation of the core network 330 for the example where the core network 330 is a 4G core network. In this example, the core network 330 may include at least one mobility management entity (MME) 410, at least one serving gateway (S-GW) 420, and at least one packet data network (PDN) gateway (P-GW) 430. The MME 410 may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs (e.g., UE 115a) served by base stations 305a to 305c. User packets (e.g., voice packets) may be transferred through the S-GW 420, which itself may be connected to the P-GW 430. The P-GW 430 may provide IP address allocation as well as other functions. The P-GW 430 may be connected to an IMS 440 to provide the UE 115a with voice services (e.g., voice over LTE (VoLTE) , and/or other IP-based voice service) . For the example of a voice call, the UE 115a sends voice packets to and receives voice packets from the IMS 440 via the core network 330. The core network 330 transports voice packets between the UE 115a and the IMS 440 through the S-GW 420 and the P-GW 430 using packet switching.

Although the second network is described above using the example where the second network is a 4G network, it is to be appreciated that the second network is not limited to this example. For example, the second network may be a 3G network or a 2G network in which the core network 330 supports voice calls (i.e., provides voice call services) for the UE 115a using a circuit-switched network.

The UE 115a needs to register with the IMS 140 via the core network 130 in order to access voice services (e.g., VoIP, video call, and/or other IP-based voice service) from the IMS 140. In this regard, FIG. 5 is a flow diagram illustrating an exemplary process for accessing a voice service from the IMS 140 via the first network. In this example, the first network is an NR network (e.g., a stand alone (SA) NR network) .

At block 510, the UE 115a starts attachment to the first network. To do this, the UE 115a may establish a communication link 125a (e.g., radio resource control (RRC) connection) between the UE 115a and a base station of the first network (e.g., one of base stations 105a to 105d) , and transmit an attach request to the AMF 210 via the base station (i.e., the UE 115a transmits the attach request to the base station which forwards the attach request to the AMF 210) . The attach request may include an identification (e.g., international mobile subscriber identity (IMSI) ) of the UE 115a and/or other information. Upon receiving the attach request, the AMF 210 identifies the UE 115a based on the identification of the UE 115a in the attach request and authenticates the UE 115a (e.g., according to an authentication procedure specified in an NR standard) .

If the AMF 210 successfully authenticates the UE 115a, then the AMF 210 may send an attach accept message to the UE 115a via the base station (e.g., one of base stations 105a to 105d) at block 520 (i.e., the AMF 210 sends the attach accept message to the base station which transmits the attach accept message to the UE 115a) . To complete attachment, the AMF 210 may establish a secure connection between the UE 115a and the AMF 210 (e.g., according to a security mode control procedure) . The secure connection may be used for non-access-stratum (NAS) signaling between the UE 115a and the AMF 210 via the base station (e.g., one of base stations 105a to 105b) . The AMF 210 may also direct the SMF 220 to create and manage a session for the UE 115a, which establishes and maintains a transport path between the UE 115a and the IMS 140 through the UPF 230. The transport path allows the UE 115a to communicate with the IMS 140 via the core network 130, as discussed further below.

At block 530, the UE 115a attempts to register with the IMS 140 for a voice service. The voice service may include VoIP, video call service, and/or another IP-based voice service. The UE 115a may attempt IMS registration by sending a registration request to the IMS 140 via the first network (i.e., the UE 115a transmits the registration request to the base station (e.g., one of base stations 105a to 105d) which forwards the registration request to the core network 130 which in turns forwards the request to the IMS 140) . The registration request may include an identification of the UE 115a and/or other information. Upon receiving the attach request, the IMS 140 identifies the UE 115a based on the identification of the UE 115a in the registration request and may authenticate the UE 115a (e.g., according to an IMS authentication and key agreement (IMS-AKA) procedure) . If registration is successful (e.g., the IMS 140 successfully authenticates the UE 115a) , then the IMS 140 may grant the UE 115a access to the voice service.

If the IMS registration fails, then the IMS 140 may send a failure message to the UE 115a at block 540 (e.g., the IMS 140 sends the failure message to the core network 130 which forwards the failure message to the base station (e.g., one of base stations 105a to 105d) which in turn transmits the failure message to the UE 115a) . The failure message may also be referred to as a failure response. The failure message may include a failure code (e.g., session initiation protocol (SIP) failure code) indicating a reason for the failure (e.g., temporary service unavailability, voice server is busy, server internal error, and the like) . The failure message may also include a retry time duration (e.g., located in a retry-after header of the failure message) . The retry time duration indicates a time duration for the UE 115a to wait before reattempting IMS registration. The retry time duration may be given in seconds or another unit of time. Thus, the UE 115a may receive the failure message at block 540 in response to the registration request in the event of an IMS registration failure.

At block 550, the UE 115a sets a timer in the UE 115a to the retry time duration and starts the timer. The timer expires at the end of the retry time duration. In FIG. 5, the retry time duration is labeled T1.

At block 560, the UE 115a stays on the first network while the timer is running. For example, the UE 115a may stay on the first network by maintaining the communication link (e.g., radio resource control (RRC) connection) between the UE 115a and the base station (e.g., one of base stations 105a to 105d) . The UE 115a may also stay on the first network by maintaining the connection (e.g., NAS signaling connection) between the UE 115a and the AMF 210. While the UE 115a stays on the first network, the SMF 220 may maintain the session of the UE 115a.

At block 570, the UE 115a determines whether the timer has expired. If the timer has not expired, then the UE 115a continues to stay on the first network. If the time has expired, then the UE 115a reattempts registration with the IMS 140 at block 580. The UE 115a may reattempt IMS registration by sending another registration request to the IMS 140 via the first network (i.e., the UE 115a transmits the registration request to the base station (e.g., one of base stations 105a to 105d) which forwards the registration request to the core network 130 which in turns forwards the request to the IMS 140) . The registration request may include an identification of the UE 115a and/or other information. If registration is successful, then the UE 115a may access the voice service from the IMS 140 via the first network. If registration fails again, then the UE 115a may receive another failure message including another retry time duration from the IMS 140 and return to block 550.

Thus, after successfully attaching to the first network (e.g., NR network) , the UE 115a attempts IMS registration to access a voice service from the IMS 140. If the IMS registration fails (e.g., due to network reasons) , then the UE 115a receives a failure message including a retry time duration from the IMS 140 via the first network. The UE 115a stays on the first network and waits for the retry time duration before making another attempt to register with the IMS 140. During the retry time duration, the UE 115a does not have access to voice services from the IMS 140. As a result, the UE 115a may not be able do a mobile originated (MO) voice call or a mobile terminated (MT) voice call during this duration.

Thus, if IMS registration fails, the UE 115a may not have voice capability for the retry time duration. If the retry time duration is long (e.g., on the order of minutes) , then the user experience may be substantially impacted as the user of the UE 115a is unable to make or receive a voice call for a long duration.

To address this, aspects of the present disclosure provide a time threshold, wherein, in the event of an IMS registration failure, the UE 115a compares the retry time duration with the time threshold. If the retry time duration is greater than the time threshold, then the UE 115 accesses a voice service via the second network (e.g., 4G network, 3G network or 2G network) . The UE 115a may stay on the second network for the retry time duration for the voice service. This allows the UE 115a to make and/or receive a voice call during the retry time duration, thereby improving the user experience. Other aspects of the present disclosure are discussed further below.

FIG. 6 is a flow diagram illustrating a process for accessing a voice service from the second network in the event of an IMS registration failure according to aspects of the present disclosure. In this example, the first network is an NR network (e.g., a stand alone (SA) NR network) . The second network may be a 4G network, a 3G network, or a 2G network.

The process illustrated in FIG. 6 includes

blocks

510, 520, 530, 540 and 550 in which the UE 115a attaches to the first network, attempts IMS registration, and starts the timer in the event of an IMS registration failure. Since a detailed description of

blocks

510, 520, 530, 540 and 550 is provided above with reference to FIG. 5, the description of these blocks is not repeated here for brevity.

At block 610, the UE 115a compares the retry time duration (labeled T1) with a time threshold. If the retry time duration is less than the time threshold, then the UE 115a proceeds to

blocks

560, 570 and 580, which are described above with reference FIG. 5. Thus, if the retry time duration is less than the time threshold, then the UE 115a stays on the first network for the retry time duration and reattempts IMS registration at block 580 after the timer expires at the end of the retry time duration. If the retry time duration is greater than the time threshold, then the UE 115a proceeds to block 620. As discussed further below, in this case, the UE 115a accesses a voice service via the second network during the retry time duration.

At block 620, the UE 115a searches for the second network. To do this, the UE 115a may perform a cell search in which the UE 115a searches (i.e., listens) for one or more signals broadcasted from one of the base stations 305a to 305c of the second network. The one or more signals may include timing references, system information, etc.

After detecting the one or more signals, the UE 115a attaches to the second network at block 630. The UE 115a may leave the first network before attaching to the second network. The UE 115a may attach to the second network by establishing a communication link 325 between the UE 115a and a base station of the second network (e.g., one of the base stations 305a to 305c) , and transmitting an attach request to the core network 330 via the base station (i.e., the UE 115a transmits the attach request to the base station which forwards the attach request to the core network 330) . The attach request may include an identification (e.g., IMSI) of the UE 115a and/or other information. Upon receiving the attach request, the core network 330 identifies the UE 115a based on the identification of the UE 115a in the attach request and authenticates the UE 115a. For the example where the core network 330 is a 4G core network, the MME 410 may authenticate the UE 115a. If the core network 330 successfully authenticates the UE 115a, then the core network 330 may create a session for the UE 115a to establish a transport path for carrying voice traffic for the UE 115a through the core network 330. For the example where the network core is a 4G core, the MME 410 may create and manage a session for the UE 115a, which establishes and maintains a transport path between the UE 115a and the IMS 440 through the S-GW 420 and P-GW 430.

At block 635, the UE 115a accesses a voice service via the second network. For example, the UE 115a may make a voice call or receive a voice call via the second network. For the example where the second network is a 4G network, the UE 115a may register with the IMS 440 via the second network and access the voice service (e.g., VoIP) from the IMS 440 via the second network. In this example, the UE 115a may transmit voice packets to and receive voice packets from the IMS 440 during a voice call via the core network 330 (e.g., via the S-GW 420 and P-GW 430 in the core network 330) . For the example where the second network is a 3G network or a 2G network, the UE 115a may access a circuit-switched voice service via the second network. In this example, voice traffic for the UE 115a is transported through a circuit-switched network in the core network 330.

At block 640, the UE 115a stays on the second network while the timer is running.

At block 650, the UE 115a determines whether the timer has expired. If the timer has not expired, then the UE 115a continues to stay on the second network. If the time has expired, then the UE 115a searches for the first network at block 655. To do this, the UE 115a may perform a cell search in which the UE 115a searches (i.e., listens) for one or more signals broadcasted from one of the base stations 105a to 105d of the first network. The one or more signals may include timing references, system information, etc.

After detecting the one or more signals, the UE 115a starts attachment to the first network at block 660. To do this, the UE 115a may establish a communication link 125a between the UE 115a and a base station of the first network (e.g., one of the base stations 105a to 105d) , and transmit an attach request to the AMF 210 via the base station where the attach request includes an identification (i.e., IMSI) of the UE 115a and/or other information. Upon receiving the attach request, the AMF 210 identifies the UE 115a based on the identification of the UE 115a in the attach request and authenticates the UE 115a.

If the AMF 210 successfully authenticates the UE 115a, then the AMF 210 may send an attach accept message to the UE 115a via the base station (e.g., one of the base station 105a to 105d) at block 670. To complete attachment, the AMF 210 may establish a secure connection between the UE 115a and the AMF 210 (e.g., according to a security mode control procedure) . The secure connection may be used for NAS signaling between the UE 115a and the AMF 210. The AMF 210 may also direct the SMF 220 to create and manage a session for the UE 115a, which establishes and maintains a transport path between the UE 115a and the IMS 140 through the UPF 230.

At block 580, the UE 115a reattempts registration with the IMS 140 (e.g., by sending another registration request to the IMS 140 via the first network) . If registration is successful, then the UE 115a may access the voice service from the IMS 140 via the first network. If registration fails again, then the UE 115a may receive another failure message including another retry time duration from the IMS 140 and return to block 550.

Thus, in the event of an IMS registration failure, the UE 115a accesses a voice service via the second network if the retry time duration is larger than the time threshold. This allows UE 115a to make and/or receive a voice call during the retry time duration, thereby improving the user experience.

In certain aspects, the time threshold may be between 15 seconds and 120 seconds (e.g., 30 seconds) . The time threshold may be set, for example, based on a time (e.g., average time) it takes for the UE 115a to detect and attach to the second network for voice service. In this example, the faster the UE 115a is capable of detecting and attaching to the second network for voice service, the shorter the time threshold.

FIG. 7 illustrates an example device 700 according to certain aspects of the present disclosure. The device 700 may be configured to operate in a UE (e.g., UE 115a) and may be configured to perform one or more of the operations described herein. The device 700 may include a processor 720, a timer 722, a memory 710, a transceiver 730, an antenna array 760, one or more antennas 770, and a user interface 740. These components may be in electronic communication via one or more buses 745.

The memory 710 may store instructions 715 that are executable by the processor 720 to cause the device 700 to perform one or more of the operations described herein. The processor 2120 may include a general-purpose processor, a digital signal processor (DSP) , a central processing unit (CPU) , a microcontroller, an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof. The memory 710 may include, by way of example, random access memory (RAM) , flash memory, read only memory (ROM) , programmable read only memory (PROM) , erasable programmable read only memory (EPROM) , electrically erasable programmable read only memory (EEPROM) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof.

The transceiver 730 is coupled to the antenna array 760. The antenna array 760 may be configured to transmit signals to and/or receive signals from one or more base stations 105a to 105d in the first network. In certain aspects, the antenna array 760 may employ beamforming to enable the transceiver 730 to electronically steer transmissions to the first network and/or electrically steer reception from the first network. In certain aspects, the transceiver 730 and the antenna array 760 may be used to transmit a registration request to a base station (e.g., one of the base stations 105a to 105d) in the first network and receive a failure message from the base station in the event of an IMS registration failure.

The transceiver 730 may also be coupled to the one or more antennas 770 and may be configured to transmit and/or receive signals via the one or more antennas 770 (e.g., for communication with the second network) .

The timer 722 is configured to keep track of a time duration (e.g., retry time duration) . In certain aspects, when the transceiver 730 receives a retry time duration in a failure message, the processor 720 may set the timer 722 to the retry time duration and start the timer. The timer 722 expires at the end of the retry time duration. In response to the timer 722 expiring, the processor 720 may reattempt IMS registration by generating a registration request and sending the registration request to the transceiver 730 for transmission to the first network.

The user interface 740 may be configured to receive data from a user (e.g., via keypad, mouse, etc. ) and provide the data to the processor 720. The user interface 740 may also be configured to output data from the processor 720 to the user (e.g., via a display, a speaker, etc. ) . In this case, the data may undergo additional processing before being output to the user.

FIG. 8 illustrates a method 800 for wireless communication according to certain aspects of the present disclosure. The method 800 may be performed at a UE (e.g., UE 115a) .

At block 810, an attempt is made to register with an internet protocol multimedia subsystem (IMS) via a first network. For example, the UE 115a may attempt to register with the IMS (e.g., IMS 140) by sending a registration request to the IMS via the first network. In the this example, the UE 115a may transmit the request to one of the base stations 105a to 105d in the first network, in which the request is forwarded from the base station to the IMS 140 through the core network 130. The registration attempt may be performed by the processor 720, the transceiver 730, the antenna array 760 and/or the one or more antennas 770.

At block 820, a failure message is received, via the first network, from the IMS in response to the registration attempt, the failure message including a retry time duration. For example, the UE 115a may receive the failure message from one of the base stations 105a to 105d, in which the failure message is forwarded from the IMS to the base station through the core network 130. The failure message may be received by the antenna array 760, the one or more antennas 770 and/or the transceiver 730. The failure message may include an SIP failure core indicating a reason for the failure (e.g., service unavailable, server busy, internal server error, etc. ) .

At block 830, the retry time duration is compared with a time threshold. The comparison may be made by the processor 720. In some examples, the time threshold may be between 15 seconds and 120 seconds.

At block 840, if the retry time duration is greater than the time threshold, a voice service is accessed via a second network during the retry time duration. For example, the UE 115a may access the voice services via the second network by making a voice call or receiving a voice call via the second network. The second network may include a 4G network, a 3G network, a 2G network, or another network. For the example of a 4G network, the UE 115 may access the voice service by receiving voice packets from and/or transmitting voice packets to one of the base stations 305a to 305c of the second network. For the example of a 3G network or a 2G network, the voice service may comprise a circuit-switched voice service in which voice traffic is carried over a circuit-switched network. The accessing of the voice service via the second network may be performed by the processor 720, the transceiver 730, the antenna array 760 and/or the one or more antennas 770.

The method 800 may optionally include reattempting to register with the IMS after the retry time duration. For example, the UE 115a may attempt to register with the IMS by sending a first registration request to the IMS via the first network, and reattempt to register with the IMS by sending a second registration request to the IMS via the first network. The UE 115a may send the first registration request and the second registration request using the transceiver 730, the antenna array 760 and/or the one or more antennas 770.

The method 800 may optionally include staying on the first network during the retry time duration if the retry time duration is less than the time threshold. For example, the UE 115a may stay on the first network by maintaining a communication link (e.g., an RRC connection) between the UE 115a and one of the base stations (e.g., 105a to 105d) of the first network. The communication link may be maintained by the processor 720, the transceiver 730, the antenna array 760 and/or the one or more antennas 770. In certain aspects, the UE 115a may leave the first network if the retry time duration is greater than the time threshold.

The method 800 may optionally include, if the retry time duration is less than the time threshold, setting a timer to the retry time duration, starting the timer, staying on the first network while the timer is running, and reattempting to register with the IMS via the first network after the timer expires. The timer may correspond to timer 722. The setting and starting of the timer may be performed by the processor 720. The staying on the first network may be performed by the processor 720, the transceiver 730, the antenna array 760 and/or the one or more antennas 770.

Any reference to an element herein using a designation such as “first, ” “second, ” and so forth does not generally limit the quantity or order of those elements. Rather, these designations are used herein as a convenient way of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element.

Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration. ” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect electrical coupling between two structures. As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

An apparatus for wireless communication, comprising:

a processor;

a memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

attempt to register with an internet protocol multimedia subsystem (IMS) via a first network;

receive, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration;

compare the retry time duration with a time threshold; and

if the retry time duration is greater than the time threshold, access a voice service via a second network during the retry time duration.
The apparatus of claim 1, wherein the instructions cause the apparatus to attempt to register with the IMS by sending a registration request to the IMS via the first network.
The apparatus of claim 1, wherein the first network is a new radio (NR) network.
The apparatus of claim 3, wherein the second network is a fourth generation (4G) network.
The apparatus of claim 4, wherein the voice service comprises a voice over internet protocol (VoIP) service.
The apparatus of claim 1, wherein the second network is a third generation (3G) or a second generation (2G) network.
The apparatus of claim 6, wherein the voice service comprises a circuit-switched voice service.
The apparatus of claim 1, wherein the time threshold is between 15 seconds and 120 seconds.
The apparatus of claim 1, wherein the instructions cause the apparatus to access the voice service via the second network by making a voice call via the second network or receiving a voice call via the second network.
The apparatus of claim 1, wherein the instructions cause the apparatus to reattempt to register with the IMS via the first network after the retry time duration.
The apparatus of claim 10, wherein the instructions cause the apparatus to access the voice service via the second network by making a voice call via the second network or receiving a voice call via the second network.
The apparatus of claim 10, wherein the instructions cause the apparatus to attempt to register with the IMS by sending a first registration request to the IMS via the first network, and reattempt to register with the IMS by sending a second registration request to the IMS via the first network.
The apparatus of claim 10, wherein the instructions cause the apparatus to stay on the first network during the retry time duration if the retry time duration is less than the time threshold.
The apparatus of claim 1, wherein, if the retry time duration is less than the time threshold, the instructions cause the apparatus to:

stay on the first network during the retry time duration; and

reattempt to register with the IMS via the first network after the retry time duration.
The apparatus of claim 14, wherein the instructions cause the apparatus to attempt to register with the IMS by sending a first registration request to the IMS via the first network, and reattempt to register with the IMS by sending a second registration request to the IMS via the first network.
The apparatus of claim 14, wherein the instructions cause the apparatus to stay on the first network by maintaining a communication link with a base station of the first network.
The apparatus of claim 16, wherein the communication link comprises a radio resource control (RRC) connection.
The apparatus of claim 1, wherein, if the retry time duration is less than threshold, the instructions cause the apparatus to:

set a timer to the retry time duration;

start the timer;

stay on the first network while the timer is running; and

reattempt to register with the IMS via the first network after the timer expires.
The apparatus of claim 1, wherein the failure message includes a session initiation protocol (SIP) failure code.
The apparatus of claim 19, wherein the SIP failure code indicates at least one of service unavailable, server busy, or internal server error.
The apparatus of claim 19, wherein the retry time duration is located in a retry-after header of the failure message.
A method for wireless communication, comprising:

attempting to register with an internet protocol multimedia subsystem (IMS) via a first network;

receiving, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration;

comparing the retry time duration with a time threshold; and

if the retry time duration is greater than the time threshold, accessing a voice service via a second network during the retry time duration.
The method of claim 22, wherein attempting to register with the IMS comprises sending a registration request to the IMS via the first network.
The method of claim 22, wherein the first network is a new radio (NR) network.
The method of claim 24, wherein the second network is a fourth generation (4G) network.
The method of claim 25, wherein the voice service comprises a voice over internet protocol (VoIP) service.
The method of claim 22, wherein the second network is a third generation (3G) or a second generation (2G) network.
The method of claim 27, wherein the voice service comprises a circuit-switched voice service.
The method of claim 22, wherein the time threshold is between 15 seconds and 120 seconds.
The method of claim 22, wherein accessing the voice service via the second network comprises making a voice call via the second network or receiving a voice call via the second network.
The method of claim 22, further comprising reattempting to register with the IMS via the first network after the retry time duration.
The method of claim 31, wherein accessing the voice service via the second network comprises making a voice call via the second network or receiving a voice call via the second network.
The method of claim 31, wherein attempting to register with the IMS comprises sending a first registration request to the IMS via the first network, and reattempting to register with the IMS comprises sending a second registration request to the IMS via the first network.
The method of claim 31, further comprising staying on the first network during the retry time duration if the retry time duration is less than the time threshold.
The method of claim 22, further comprising, if the retry time duration is less than the time threshold,

staying on the first network during the retry time duration; and

reattempting to register with the IMS via the first network after the retry time duration.
The method of claim 35, wherein attempting to register with the IMS comprises sending a first registration request to the IMS via the first network, and reattempting to register with the IMS comprises sending a second registration request to the IMS via the first network.
The method of claim 35, wherein staying on the first network comprises maintaining a communication link with a base station of the first network.
The method of claim 37, wherein the communication link comprises a radio resource control (RRC) connection.
The method of claim 22, further comprising, if the retry time duration is less than threshold,

setting a timer to the retry time duration;

starting the timer;

staying on the first network while the timer is running; and

reattempting to register with the IMS via the first network after the timer expires.
The method of claim 22, wherein the failure message includes a session initiation protocol (SIP) failure code.
The method of claim 40, wherein the SIP failure code indicates at least one of service unavailable, server busy, or internal server error.
The method of claim 40, wherein the retry time duration is located in a retry-after header of the failure message.
An apparatus for wireless communication, comprising:

means for attempting to register with an internet protocol multimedia subsystem (IMS) via a first network;

means for receiving, via the first network, a failure message from the IMS in response to the registration attempt, the failure message including a retry time duration;

means for comparing the retry time duration with a time threshold; and

means for accessing a voice service via a second network during the retry time duration if the retry time duration is greater than the time threshold.
The apparatus of claim 43, wherein the means for attempting to register with the IMS comprises means for sending a registration request to the IMS via the first network.
The apparatus of claim 43, wherein the first network is a new radio (NR) network.
The apparatus of claim 45, wherein the second network is a fourth generation (4G) network.
The apparatus of claim 46, wherein the voice service comprises a voice over internet protocol (VoIP) service.
The apparatus of claim 43, wherein the second network is a third generation (3G) or a second generation (2G) network.
The apparatus of claim 48, wherein the voice service comprises a circuit-switched voice service.
The apparatus of claim 43, wherein the time threshold is between 15 seconds and 120 seconds.
The apparatus of claim 43, wherein the means for accessing the voice service via the second network comprises means for making a voice call via the second network or means for receiving a voice call via the second network.
The apparatus of claim 43, further comprising means for reattempting to register with the IMS via the first network after the retry time duration.
The apparatus of claim 43, wherein the means for accessing the voice service via the second network comprises means for making a voice call via the second network or means for receiving a voice call via the second network.
The apparatus of claim 53, wherein the means for attempting to register with the IMS comprises means for sending a first registration request to the IMS via the first network, and the means for reattempting to register with the IMS comprises means for sending a second registration request to the IMS via the first network.
The apparatus of claim 53, further comprising means for staying on the first network during the retry time duration if the retry time duration is less than the time threshold.
The apparatus of claim 43, further comprising, if the retry time duration is less than the time threshold,

means for staying on the first network during the retry time duration; and

means for reattempting to register with the IMS via the first network after the retry time duration.
The apparatus of claim 56, wherein the means for attempting to register with the IMS comprises means for sending a first registration request to the IMS via the first network, and the means for reattempting to register with the IMS comprises means for sending a second registration request to the IMS via the first network.
The apparatus of claim 56, wherein the means for staying on the first network comprises means for maintaining a communication link with a base station of the first network.
The apparatus of claim 58, wherein the communication link comprises a radio resource control (RRC) connection.
The apparatus of claim 43, further comprising, if the retry time duration is less than the time threshold,

means for setting a timer to the retry time duration;

means for starting the timer;

means for staying on the first network while the timer is running; and

means for reattempting to register with the IMS via the first network after the timer expires.
The apparatus of 43, wherein the failure message includes a session initiation protocol (SIP) failure code.
The apparatus of claim 61, wherein the SIP failure code indicates at least one of service unavailable, server busy, or internal server error.
The apparatus of claim 61, wherein the retry time duration is located in a retry-after header of the failure message.