WO2021217591A1

WO2021217591A1 - Management of unstable standalone communications

Info

Publication number: WO2021217591A1
Application number: PCT/CN2020/088326
Authority: WO
Inventors: Fojian ZHANG; Hao Zhang; Chaofeng HUI; Jian Li; Yi Liu; Yuankun ZHU; Quanling ZHANG; Bo Yu
Original assignee: Qualcomm Incorporated
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2021-11-04

Abstract

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may establishes a connection between the UE and a standalone network of a first radio access technology, and determines, after establishing the connection, a radio link failure between the UE and the standalone network. The UE may then identify that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time. Upon identifying that the plurality of radio link failures is within the predetermined period of time, the UE disables a standalone network connectivity of the UE, and establishes dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

Description

MANAGEMENT OF UNSTABLE STANDALONE COMMUNICATIONS

FIELD OF TECHNOLOGY

The following relates generally to wireless communications and more specifically to management of unstable standalone communications.

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 orthogonal frequency division multiplexing (DFT-S-OFDM) . A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

A UE may support standalone architecture and non-standalone architecture to connect with multiple networks. In some cases, communications in a standalone architecture may be unstable and may adversely impact the performance of the UE.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support managing unstable standalone communications. Generally, the described techniques provide for improvements in communications systems supporting standalone communications. A user equipment (UE) may support a standalone architecture, where the UE is served by one or more base stations associated with a single radio access technology. Additionally or alternatively, the UE may support a non-standalone architecture, where different radio access technologies are utilized simultaneously. In some examples, a UE may establish connection with a standalone network of a first radio access technology. The UE may detect a radio link failure between the UE and the standalone network. In some cases, to mitigate the communications interruptions between a UE and a standalone network of a first radio access technology, the UE may maintain a counter to record the number of radio link failures. The UE may utilize the counter to identify that the radio link failure is one of a threshold number of radio link failures between the UE and the standalone network within a predetermined period of time. In some examples, the UE may disable a standalone network connectivity of the UE upon determining that the threshold number of radio link failures has occurred within the predetermined period of time. In some cases, the UE may establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

A method of wireless communication at a UE is described. The method may include establishing a connection between the UE and a standalone network of a first radio access technology, determining, after establishing the connection, a radio link failure between the UE and the standalone network, identifying that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disabling a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establishing dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to establish a connection between the UE and a standalone network of a first radio access technology, determine, after establishing the connection, a radio link failure between the UE and the standalone network, identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for establishing a connection between the UE and a standalone network of a first radio access technology, determining, after establishing the connection, a radio link failure between the UE and the standalone network, identifying that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disabling a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establishing dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to establish a connection between the UE and a standalone network of a first radio access technology, determine, after establishing the connection, a radio link failure between the UE and the standalone network, identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network, receiving a connection set up request from the standalone network after transmitting the connection re-establishment request, and re-establishing connectivity with the standalone network based on completion of a connection set up.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for incrementing a counter each time the connectivity with the standalone network may be re-established followed by a radio link failure of the set of radio link failures, where disabling the standalone network connectivity of the UE may be further based on the counter exceeding a threshold value within the predetermined period of time.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for initiating a back-off timer upon disabling the standalone network connectivity of the UE. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a deregistration request to the standalone network upon initiating the back-off timer, and receiving a deregistration accept message from the standalone network.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, establishing the dual connectivity further may include operations, features, means, or instructions for transmitting an attach request to the anchor cell of the second radio access technology based on receiving the deregistration accept message from the standalone network, receiving an attach accept message from the anchor cell of the second radio access technology, and activating an evolved packet system bearer upon receiving the attach accept message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the attach request includes an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for re-enabling connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, re-enabling the connectivity between the UE and the standalone network may include operations, features, means, or instructions for transmitting a registration request to the standalone network upon expiration of the back-off timer, and receiving a registration accept message from the standalone network.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, establishing the connection between the UE and the standalone network of the first radio access technology may include operations, features, means, or instructions for performing a radio resource control procedure with the standalone network of the first radio access technology to establish the connection. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first radio access technology may be a fifth generation (5G) network and the second radio access technology may be a 4G network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system that supports management of unstable standalone communications in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system that supports management of unstable standalone communications in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow that supports management of unstable standalone communications in accordance with aspects of the present disclosure.

FIGs. 4 and 5 show block diagrams of devices that support management of unstable standalone communications in accordance with aspects of the present disclosure.

FIG. 6 shows a block diagram of a communications manager that supports management of unstable standalone communications in accordance with aspects of the present disclosure.

FIG. 7 shows a diagram of a system including a device that supports management of unstable standalone communications in accordance with aspects of the present disclosure.

FIGs. 8 through 10 show flowcharts illustrating methods that support management of unstable standalone communications in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

A user equipment (UE) may support a standalone architecture, where the UE is served by one or more base stations associated with a single radio access technology. Additionally or alternatively, the UE may support a non-standalone architecture, where different radio access technologies are utilized simultaneously. For example, a non-standalone UE may anchor on or connect to a cell associated with a first radio access technology (e.g., Long-Term Evolution (LTE) ) , while facilitating communications with a cell associated with a second radio access technology (e.g., New Radio (NR) ) . In some cases, the cells associated with each radio access technology may be contained at a single base station or may be located on separate base stations.

As described herein, some wireless networks may be configured to operate in a dual-connectivity configuration. For example, a wireless network may be configured to operate in an evolved universal terrestrial radio access network (E-UTRAN) in NR, which may be referred to as EN-DC, as 5G EN-DC, or as a 5G NR dual-connectivity configuration or system, or some combination thereof. Broadly, the dual-connectivity configuration supports the UE being connected to two devices, such as base stations, (or nodes) at the same time. In some examples, one node (e.g., a master node) may be a 5G (e.g., an NR) node and a second node (e.g., a secondary node) may be an LTE node. In other examples, the master node may be an LTE node and the secondary node may be a 5G (e.g., NR) node. In some examples, the master node and the secondary node may be 5G (e.g., NR) nodes or they may both be LTE nodes. The dual-connectivity configuration may be supported when inter-connectivity has been established between the master node and secondary node, via one or more backhaul links, core network functions, or the like. Some examples of dual-connectivity may include the UE being simultaneously connected to the LTE and 5G NR node or the UE utilizing the LTE node for control plane information and the 5G NR node for user plane traffic, or any combination thereof. In some aspects, the dual-connectivity configuration may support direct or split signaling radio bearers (or both) .

According to one or more aspects of the present disclosure, the UE may establish a connection with a standalone network of a first radio access technology (e.g., 5G standalone network) and may receive data transmissions from the standalone network. The UE may determine a radio link failure between the UE and the standalone network. In some cases, the UE may re-establish a connection with the standalone network in response to determining a radio link failure. However, if the UE frequently determines radio link failure and re-establishes connection with a standalone network after determining the radio link failure, then the efficiency and the user experience at the UE may suffer.

To mitigate the communications interruptions between a UE and a standalone network of a first radio access technology (such as base station associated with standalone 5G network) , the UE may maintain a counter to record the number of radio link failures. Specifically, the UE may increment the counter each time the connectivity with the standalone network is re-established followed by a radio link failure. If the counter reaches a preconfigured number in a preconfigured amount of time, the UE may determine that the standalone network connection (e.g., connection with a 5G standalone network) is unstable. In some examples, upon determining an unstable network connection, the UE may disable a standalone network connectivity of the UE. The UE may then enable dual-connectivity with an anchor cell of a second radio access technology (e.g., an LTE anchor cell) and a secondary cell of the first radio access technology (e.g., a secondary 5G cell) .

UEs capable of supporting uplink power control parameter indication for multi-panel transmission may utilize the techniques described herein to experience power saving, such as reduced power consumption and extended battery life while ensuring reliable and efficient communications between UEs and base stations. Particular aspects of the subject matter described in this disclosure may be implemented to realize one or more of the following potential advantages. The techniques employed by the described UEs may provide benefits and enhancements to the operation of the UEs. For example, operations performed by the UEs may provide improvements to wireless operations. In some examples, the UEs may support high reliability and low latency communications, among other examples, in accordance with aspects of the present disclosure. The described techniques may thus include features for improvements to power consumption, spectral efficiency, higher data rates and, in some examples, may promote enhanced efficiency for high reliability and low latency operations, among other benefits

Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are further described in the context of additional wireless communications systems and process flows. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to management of unstable standalone communications.

FIG. 1 illustrates an example of a wireless communications system 100 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be an LTE network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or an NR network. In some examples, the wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

The base stations 105 may be dispersed throughout a geographic area to form the wireless communications system 100 and may be devices in different forms or having different capabilities. The base stations 105 and the UEs 115 may wirelessly communicate via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which the UEs 115 and the base station 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area over which a base station 105 and a UE 115 may support the communication of signals according to one or more radio access technologies.

The UEs 115 may be dispersed throughout a coverage area 110 of the wireless communications system 100, and each UE 115 may be stationary, or mobile, or both at different times. The UEs 115 may be devices in different forms or having different capabilities. Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115, the base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment) , as shown in FIG. 1.

The base stations 105 may communicate with the core network 130, or with one another, or both. For example, the base stations 105 may interface with the core network 130 through one or more backhaul links 120 (e.g., via an S1, N2, N3, or other interface) . The base stations 105 may communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) , or indirectly (e.g., via core network 130) , or both. In some examples, the backhaul links 120 may be or include one or more wireless links.

One or more of the base stations 105 described herein may include or may be referred to by a person having ordinary skill 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 NodeB or a giga-NodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or other suitable terminology.

A UE 115 may include or may 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, among other examples. A UE 115 may also include or may be referred to as 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 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples.

The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115 that may sometimes act as relays as well as the base stations 105 and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in FIG. 1.

The UEs 115 and the base stations 105 may wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links 125. For example, a carrier used for a communication link 125 may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP) ) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR) . Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information) , control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system 100 may support communication with a UE 115 using carrier aggregation or multi-carrier operation. A UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers.

In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN) ) and may be positioned according to a channel raster for discovery by the UEs 115. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs 115 via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology) .

The communication links 125 shown in the wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode) .

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz) ) . Devices of the wireless communications system 100 (e.g., the base stations 105, the UEs 115, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 or UEs 115 that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM) ) . In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams) , and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE 115.

One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for the UE 115 may be restricted to one or more active BWPs.

The time intervals for the base stations 105 or the UEs 115 may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T _s=1/ (Δf _max·N _f) seconds, where Δf _max may represent the maximum supported subcarrier spacing, and N _f may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms) ) . Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023) .

Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . In some wireless communications systems 100, a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N _f) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation.

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI) . In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) ) .

Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET) ) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs 115. For example, one or more of the UEs 115 may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs) ) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets for sending control information to a specific UE 115.

Each base station 105 may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) , or others) . In some examples, a cell may also refer to a geographic coverage area 110 or a portion of a geographic coverage area 110 (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station 105. For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas 110, among other examples.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs 115 with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs 115 with service subscriptions with the network provider or may provide restricted access to the UEs 115 having an association with the small cell (e.g., the UEs 115 in a closed subscriber group (CSG) , the UEs 115 associated with users in a home or office) . A base station 105 may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers.

In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT) , enhanced mobile broadband (eMBB) ) that may provide access for different types of devices.

In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, the overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous network in which different types of the base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

The wireless communications system 100 may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timings, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timings, and transmissions from different base stations 105 may, in some examples, not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication) . M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans interacting with the application program. Some UEs 115 may be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples, half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for the UEs 115 include entering a power saving deep sleep mode when not engaging in active communications, operating over a limited bandwidth (e.g., according to narrowband communications) , or a combination of these techniques. For example, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a defined portion or range (e.g., set of subcarriers or resource blocks (RBs) ) within a carrier, within a guard-band of a carrier, or outside of a carrier.

The wireless communications system 100 may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs 115 may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions) . Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT) , mission critical video (MCVideo) , or mission critical data (MCData) . Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein.

In some examples, a UE 115 may also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol) . One or more UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of the UEs 115 communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE 115 transmits to every other UE 115 in the group. In some examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs 115 without the involvement of a base station 105.

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or 5G core (5GC) , which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME) , an access and mobility management function (AMF) ) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW) , a Packet Data Network (PDN) gateway (P-GW) , or a user plane function (UPF) ) . The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs 115 served by the base stations 105 associated with the core network 130. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services 150. The operators IP services 150 may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched Streaming Service.

Some of the network devices, such as a base station 105, may include subcomponents such as an access network entity 140, which may be an example of an access node controller (ANC) . Each access network entity 140 may communicate with the UEs 115 through one or more other access network transmission entities 145, which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs) . Each access network transmission entity 145 may include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105) .

The wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz) . Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs 115 located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

The wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz) , also known as the millimeter band. In some examples, the wireless communications system 100 may support millimeter wave (mmW) communications between the UEs 115 and the base stations 105, and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

The wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations 105 and the UEs 115 may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

A base station 105 or a UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

The base stations 105 or the UEs 115 may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords) . Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) , where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) , where multiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105, a UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation) .

A base station 105 or a UE 115 may use beam sweeping techniques as part of beam forming operations. For example, a base station 105 may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions. For example, the base station 105 may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station 105, or by a receiving device, such as a UE 115) a beam direction for later transmission or reception by the base station 105.

Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions and may report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality or an otherwise acceptable signal quality.

In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station 105 to a UE 115) . The UE 115 may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station 105 may transmit a reference signal (e.g., a cell-specific reference signal (CRS) , a channel state information reference signal (CSI-RS) ) , which may be precoded or unprecoded. The UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook) . Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal) . The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR) , or otherwise acceptable signal quality based on listening according to multiple beam directions) .

The wireless communications system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or a core network 130 supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels.

The UEs 115 and the base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC) ) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) . HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions) . In some examples, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

A UE may support operations to manage unstable standalone communications that may allow the UE to establish connections with multiple networks. In some wireless communications systems, a UE may establish a connection between the UE and a standalone network for 5G radio access technology. In some cases, network coverage may impact the connectivity at the UE. For example, in some standalone networks (such as standalone network for 5G radio access technology) , a UE may experience radio link failure. Upon determining the radio link failure, the UE may re-establish a radio resource control connection and attempt to re-connect to the standalone network. In some cases, the UE may determine another radio link failure after re-establishing the connection. Frequently alternating between radio link failures and re-establishing connections may result in an unstable radio resource control connection, and may thus adversely impact user experience at the UE.

According to one or more aspects of the present disclosure, the UE 115 may establish a connection with a standalone network of a first radio access technology (e.g., 5G standalone network) and may receive data transmissions from the standalone network. The UE 115 may determine a radio link failure between the UE 115 and the standalone network. In some cases, the UE 115 may perform a connection procedure (e.g., a radio resource control procedure) with the standalone network in response to determining a radio link failure. In some cases, the UE 115 may subsequently determine a second radio link failure after re-establishing the connection. In some implementations, the UE 115 may identify that the radio link failure is one of a set of radio link failures between the UE 115 and the standalone network within a predetermined period of time. For example, the UE 115 may increment a counter each time the UE 115 experiences a radio link failure after establishing a connection with a standalone network. If the counter reaches a preconfigured number in a preconfigured amount of time, the UE 115 may determine that the standalone network supported by a base station 105 is abnormal. In some cases, in response to the counter reaching a threshold, the UE 115 may disable a standalone network connectivity, and may enable a dual-connectivity with an anchor cell of a second radio access technology (anchor cell of 4G network) and a secondary cell of the first radio access technology (secondary cell of 5G network) .

FIG. 2 illustrates an example of a wireless communications system 200 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. In some examples, the wireless communications system 200 may implement aspects of wireless communications system 100. The wireless communications system 200 may include base stations 105-a, 105-b, and 105-c and UE 115-a, which may be examples of base stations 105 and a UE 115 as described with reference to FIG. 1. Each base station 105 may serve a geographic coverage area. In some cases, one or more of the geographic coverage areas served by base stations 105-a, 105-b, and 105-c may overlap. In the example of FIG. 2, the UE 115-a may operate in standalone mode and/or non-standalone mode. That is, the UE 115-a may support a standalone architecture, where the UE 115-a is served by one or more base stations associated with a single radio access technology. Additionally, the UE 115-a may support a non-standalone architecture, where different radio access technologies are utilized simultaneously. For example, a non-standalone UE may anchor on or connect to a cell associated with a first radio access technology (e.g., LTE) , while facilitating communications with a cell associated with a second radio access technology (e.g., NR) . In some cases, the cells associated with each radio access technology may be contained at a single base station or may be located on separate base stations.

In some cases, the UE 115-a may be configured to support improved communications by managing unstable radio resource control connections while operating in a standalone architecture (or standalone mode) . For example, the UE 115-a may limit communications on an abnormal network served by one base station 105 associated with a radio access technology to improve efficiency and reduce latency. As described herein, upon detecting abnormal network behavior while operating in a standalone mode, the UE 115-a may be configured to disable the standalone capability and switch to a non-standalone architecture. That is, the UE 115-a may be configured to enable dual-connectivity with another network served by another base station 105 if the UE 115-a determines that a standalone network is unstable. Additionally or alternatively, other wireless devices, such as base stations 105-a, 105-b, or 105-c, or some combination of these base stations 105, may implement procedures to improve unstable standalone communications.

In some cases, each network may be supported by a different base station 105, or each network may be supported by the same base station 105, or a combination thereof. In one example, base station 105-a may support a standalone 5G network, base station 150-b may support a 4G network, and base station 105-c may support a non-standalone 5G network. In some cases, a network may refer to a cell. As the UE 115-a is configured to support dual-connectivity, the UE 115-a may support communications with two base stations 105 (e.g., two networks) at a time. In one example, the UE 115-a may communicate with base station 105-a associated with a standalone network of a first radio access technology (e.g., 5G standalone network) via communication link 215. The UE 115-a may establish dual-connectivity with the base station 105-b associated with an anchor cell of a second radio access technology (e.g., 4G anchor cell or LTE anchor cell) over communication link 220-a, and with the base station 105-c associated with the secondary cell of the first radio access technology (e.g., a 5G non-standalone network) over communication link 220-b.

As described herein, some wireless communications systems provide for 5G standalone connections. The UE 115-a may establish a connection with base station 105-a and transmit and receive signals to base station 105-a over communication link 215. In some cases, UE 115-a may use base station 105-a, as base station 105-a supports a 5G network, for low-latency activities (e.g., online gaming, streaming) . In some cases, the UE 115-a may establish a standalone network with the base station 105-a. In some standalone networks (such as standalone network for 5G radio access technology) , a UE may experience radio link failure. In some examples, a 5G standalone network coverage may result in an unstable connection. In some wireless communications systems, 5G standalone cells may be sparsely distributed. For example, a UE near the edge of a coverage area of a 5G standalone cell may not have another 5G standalone cell to transfer to. As such, in some wireless communications systems, a UE may be registered to a 5G standalone network, and may experience a radio link failure. Upon determining the radio link failure, the UE may re-establish a radio resource control connection and attempt to re-connect to the 5G standalone network. To re-establish a radio resource control connection with a standalone network, a UE may perform a connection procedure, such as a radio resource control procedure.

In some cases, the UE may perform the radio resource control procedure and may wait for an action by a serving base station. In some cases, the base station may accept the radio resource control re-establishment request transmitted by the UE and the UE may re-establish a connection with the base station. In some cases, existing network coverage conditions may result in a subsequent radio link failure. Such radio link failures followed by re-establishing connections may result in an unstable radio resource control connection. The UE may continue to detect radio link failures, and may continue to re-establish communication links with a standalone network. This repeated behavior may adversely impact the experience of a UE with a base station, and thus may adversely impact low-latency communications supported by the base station. Additionally, such repeated radio link failures may hamper user experience at the UE.

To mitigate the communications interruptions between a UE (such as UE 115-a) and a standalone network of a first radio access technology (such as base station 105-aassociated with standalone 5G network) , the UE 115-a may be configured with a counter to record the number of radio link failures. Specifically, to decrease latency and improve resource efficiency, the UE 115-a may be configured to detect when a 5G standalone network is unstable for that UE 115-a. Detection of an unstable connection may be accomplished via a counter at the UE 115-a that may be used to count a number of radio link failures the UE 115-a experiences within a time period. For example, each time UE 115-a detects a radio link failure, and performs a radio resource control procedure to re-establish a connection with a standalone network (e.g., 5G standalone network) , the UE 115-a may increment the counter. For instance, the UE 115-a may be configured to increment a counter “N_RLF” each time a radio link failure occurs after re-establishing a connection with the base station 105-a associated with a 5G standalone cell. If the counter reaches a preconfigured number in a preconfigured amount of time, the UE may determine that the 5G standalone network supported by base station 105-a is abnormal. In some cases, the counter may be configured to reset after a preconfigured amount of time, or at the event of a trigger, such as UE 115-a disconnecting from the first network (e.g., 5G network) . In response to the counter reaching a threshold, the UE 115-a may disable connectivity with base station 105-a associated with the standalone network of a first radio access technology (or standalone 5G network) . The UE may then enable dual-connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology. As described in the example of FIG. 2, the UE 115-a may enable dual-connectivity with the base station 105-b (anchor cell of 4G network) and the base station 105-c (secondary cell of 5G network) .

In some cases, upon establishing a dual-connectivity with the base station 105-b and the base station 105-c, the UE 115-a may start a timer, such as a back off timer (e.g., T_backoff_SA) . In some cases, the timer duration may be preconfigured, or may be dynamically, semi-persistently, or aperiodically updated by one or more networks or one or more base stations 105. In some implementations, the timer duration (e.g., some number of minutes, or some number of hours, or a combination thereof) may be selected by the UE 115-a. Upon the expiration of the timer, the UE 115-a may disable the dual-connectivity with the base station 105-b and the base station 105-c, and may re-enable connection with the base station 105-a.

FIG. 3 illustrates an example of a process flow 300 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. In some examples, the process flow 300 may implement aspects of wireless communications system 100 as described in FIG. 1 and wireless communications system 200 as described in FIG. 2. The process flow 300 may illustrate an example of disabling a standalone network connectivity and enabling dual connectivity for improved communications. For example, a UE 305, such as a UE described with reference to FIGs. 1 and 2, may support standalone communications and non-standalone communications. In one example, the UE 305 may be used for communications with an NR cell 310-a, or an LTE anchor cell 310-b, or a combination thereof. In some examples, The UE 305 may switch between cells 310 based on a previously enabled cell being abnormal. In some cases, the cells 310 may each be served by a different base station, or multiple cells 310 may be served by the same base station 105, where the one or more base stations may be examples of the corresponding wireless devices described with reference to FIG. 1 and FIG. 2. In some cases, a cell may refer to a network as described with reference to FIG. 2. In some cases, instead of a UE implementing procedures to improve unstable standalone communications, another device, such as a base station may implement the procedures.

In the following description of the process flow 300, the operations between the UE 305, the NR cell 310-a, and the LTE anchor cell 310-b may be transmitted in a different order than the example order shown, or the operations performed by the UE 305, the NR cell 310-a, and the LTE anchor cell 310-b may be performed in different orders or at different times. Some operations may also be omitted from the process flow 300, and other operations may be added to the process flow 300.

At 315, the UE 305 may be configured to operate in a 5G standalone mode. That is, the UE 305 may be registered to operate in a 5G standalone network.

At 320, the UE 305 may transmit a registration request (e.g., a 5G registration request) to NR cell 310-a (such as, a first cell associated with 5G radio access technology) . The UE 305 may transmit the registration request to establish a connection with the NR cell 310-a in a standalone mode. For instance, in the standalone mode, the UE 305 may be configured to be served only by the NR cell 310-a.

At 322, the NR cell 310-a may transmit a registration accept message (e.g., a 5G registration accept message) to the UE 305. As such, the UE 305 may establish a connection with the NR cell 310-a (e.g., a first cell associated with a first network) in a standalone mode.

At 324, the UE 305 may perform a radio resource control procedure with the standalone network of the first radio access technology (e.g., 5G network) to establish the connection. The UE 305 may utilize the radio resource control procedure to establish a connection between the UE 305 and a standalone network of a first radio access technology (e.g., 5G radio access technology) .

At 326, the UE 305 may determine a radio link failure between the UE 305 and the standalone network. For example, after establishing the connection with the NR cell 310-a, the UE 305 may determine that a radio link failure has occurred between the NR cell 310-a and the UE 305 operating in standalone mode. In some examples, the UE 305 may experience such a radio link failure due to insufficient network coverage.

In some cases, the UE 305 may re-establish a connection with the NR cell 310-a after a radio link failure. At 328, the UE 305 may initialize and/or increment a counter based on the radio link failure. In some cases, the UE 305 may determine whether a preconfigured count on the counter has been reached (e.g., a maximum count, threshold value) . For example, the UE 305 may identify that the radio link failure is one of a set of radio link failures between the UE 305 and the standalone network (e.g., network associated with the NR cell 310-a) within a predetermined period of time. If the preconfigured count has not been reached, at 334, then procedure 1 may be looped.

At 330, upon determining that the counter (at 328) has not reached a threshold value, the UE 305 may transmit a connection re-establishment request to the standalone network. For example, the UE 305 may transmit a radio resource control re-establishment request to the NR cell 310-a in response to determining the radio link failure between the UE and the standalone network.

At 332, the UE 305 may receive a connection set up request from the standalone network after transmitting the connection re-establishment request. For instance, the NR cell 310-a may receive the radio resource control re-establishment request, and may transmit a radio resource control setup request to the UE 305. In some cases, the UE 305 may perform a radio resource control setup in response to receiving the radio resource control setup request from the NR cell 310-a.

Upon performing the radio resource control setup, the UE 305 may transmit a radio resource control setup complete message to the standalone network. In the example of FIG. 3, the UE 305 may transmit the radio resource control setup complete message to the NR cell 310-a. Thus, the UE 305 may re-establish connectivity with the standalone network based on completion of a connection set up.

According to one or more aspects, the UE 305 may experience one or more radio link failures. The UE 305 may increment a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the set of radio link failures. That is, if the UE 305 experiences a radio link failure, the UE increments the counter at 328. The UE 305 may then verify whether a preconfigured count (e.g., a threshold counter value) is reached upon incrementing the counter.

In one example, the counter may reach the threshold value if the radio link failure (at 326) is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time. Additionally or alternatively, if the counter does not reach a threshold value, the UE 305 may loop procedure 1, at 336. Alternatively, if the counter reaches a threshold value, at 338, the UE 305 may initiate a back-off timer (e.g., T_backoff_SA) . For instance, the UE 305 may continue to re-establish a radio resource control with the standalone network up to a threshold number of times within a time period. If the UE 305 experiences a set of radio link failures that satisfies a threshold, then the UE 305 may determine that the radio resource control connection between the UE 305 and the standalone network (e.g., NR cell 310-a) is unstable. In some examples, upon identifying an unstable radio resource control connection, the UE 305 may disable a standalone network connectivity of the UE 305. As depicted herein, the UE 305 may start the back-off timer upon disabling the standalone network connectivity of the UE 305.

At 340, the UE 305 may transmit a deregistration request to the standalone network upon initiating the back-off timer. For example, the UE 305 may transmit to the NR cell 310-a, an indication of the UE 305 disabling the disabling the standalone network connectivity.

At 342, the NR cell 310-a may transmit a deregistration accept message to the UE 305. The UE 305 may determine that the standalone network has accepted the deregistration request transmitted by the UE 305. That is, the UE 305 may trigger a deregistration from the 5G standalone network.

In some examples, the UE 305 may switch to a 5G non-standalone network, That is, the UE 305 may establish dual connectivity with an anchor cell of a second radio access technology (e.g., LTE anchor cell 310-b) and a secondary cell of the first radio access technology (e.g., a secondary 5G cell) based on the disabling of the standalone network connectivity of the UE 305. Upon receiving the deregistration accept message, at 344, the UE 305 may transmit an attach request to the anchor cell of the second radio access technology. As depicted in the example of FIG. 3, the UE 305 may transmit the attach request to the LTE anchor cell 310-b based on receiving the deregistration accept message from the standalone network (e.g., from NR cell 310-a) . In some cases, the attach request may include an indication of a capability to support dual connectivity with E-UTRAN and NR.

At 346, the UE 305 may receive an attach accept message from the anchor cell of the second radio access technology (e.g., LTE anchor cell 310-b) . At 348, the UE 305 may activate an evolved packet system bearer upon receiving the attach accept message.

At 350, the LTE anchor cell 310-b in combination with a secondary 5G cell (not shown) may trigger a secondary cell group addition procedure. Upon completing the secondary cell group addition procedure, the UE 305 may be configured to communicate in a non-standalone mode. In one example, the UE 305 may communicate using the LTE anchor cell 310-b.

At 352, the UE 305 may determine that the back-off timer has expired. In one example, the UE 305 may re-enable connectivity between the UE 305 and the standalone network of the first radio access technology (or 5G) upon expiration of the back-off timer.

At 354, the UE 305 may transmit a registration request to the standalone network upon expiration of the back-off timer. As described herein, the UE 305 may transmit the registration request to the NR cell 310-a. At 356, the UE 305 may receive a registration accept message from the standalone network. Upon receiving the registration accept message, the UE 305 may be re-connected to a standalone network of the NR radio access technology.

FIG. 4 shows a block diagram 400 of a device 405 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The device 405 may be an example of aspects of a UE 115 as described herein. The device 405 may include a receiver 410, a communications manager 415, and a transmitter 420. The device 405 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 410 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to management of unstable standalone communications, etc. ) . Information may be passed on to other components of the device 405. The receiver 410 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The receiver 410 may utilize a single antenna or a set of antennas.

The communications manager 415 may establish a connection between the UE and a standalone network of a first radio access technology, determine, after establishing the connection, a radio link failure between the UE and the standalone network, identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE. The communications manager 415 may be an example of aspects of the communications manager 710 described herein.

The communications manager 415, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 415, or its sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The communications manager 415, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 415, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 415, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 420 may transmit signals generated by other components of the device 405. In some examples, the transmitter 420 may be collocated with a receiver 410 in a transceiver module. For example, the transmitter 420 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The transmitter 420 may utilize a single antenna or a set of antennas.

FIG. 5 shows a block diagram 500 of a device 505 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The device 505 may be an example of aspects of a device 405, or a UE 115 as described herein. The device 505 may include a receiver 510, a communications manager 515, and a transmitter 540. The device 505 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to management of unstable standalone communications, etc. ) . Information may be passed on to other components of the device 505. The receiver 510 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The receiver 510 may utilize a single antenna or a set of antennas.

The communications manager 515 may be an example of aspects of the communications manager 415 as described herein. The communications manager 515 may include a connection establishment component 520, a radio link failure component 525, a network disabling component 530, and a dual connectivity component 535. The communications manager 515 may be an example of aspects of the communications manager 710 described herein.

The connection establishment component 520 may establish a connection between the UE and a standalone network of a first radio access technology. The radio link failure component 525 may determine, after establishing the connection, a radio link failure between the UE and the standalone network and identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time.

The network disabling component 530 may disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time. The dual connectivity component 535 may establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

The transmitter 540 may transmit signals generated by other components of the device 505. In some examples, the transmitter 540 may be collocated with a receiver 510 in a transceiver module. For example, the transmitter 540 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The transmitter 540 may utilize a single antenna or a set of antennas.

FIG. 6 shows a block diagram 600 of a communications manager 605 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The communications manager 605 may be an example of aspects of a communications manager 415, a communications manager 515, or a communications manager 710 described herein. The communications manager 605 may include a connection establishment component 610, a radio link failure component 615, a network disabling component 620, a dual connectivity component 625, a counter component 630, a timer component 635, a deregistration component 640, and a registration component 645. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The connection establishment component 610 may establish a connection between the UE and a standalone network of a first radio access technology. In some examples, the connection establishment component 610 may perform a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.

The radio link failure component 615 may determine, after establishing the connection, a radio link failure between the UE and the standalone network. In some examples, the radio link failure component 615 may identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time.

The network disabling component 620 may disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time. The dual connectivity component 625 may establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE. In some cases, the first radio access technology is a 5G network and the second radio access technology is a 4G network.

In some examples, the connection establishment component 610 may transmit a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network. In some examples, the connection establishment component 610 may receive a connection set up request from the standalone network after transmitting the connection re-establishment request. In some examples, the connection establishment component 610 may re-establish connectivity with the standalone network based on completion of a connection set up.

The counter component 630 may increment a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the set of radio link failures, where disabling the standalone network connectivity of the UE is further based on the counter exceeding a threshold value within the predetermined period of time.

The timer component 635 may initiate a back-off timer upon disabling the standalone network connectivity of the UE. In some examples, the connection establishment component 610 may re-enable connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.

In some examples, the dual connectivity component 625 may transmit an attach request to the anchor cell of the second radio access technology based on receiving the deregistration accept message from the standalone network. In some examples, the dual connectivity component 625 may receive an attach accept message from the anchor cell of the second radio access technology.

In some examples, the dual connectivity component 625 may activate an evolved packet system bearer upon receiving the attach accept message. In some cases, the attach request includes an indication of a capability to support dual connectivity with E-UTRAN and NR.

The deregistration component 640 may transmit a deregistration request to the standalone network upon initiating the back-off timer. In some examples, the deregistration component 640 may receive a deregistration accept message from the standalone network.

The registration component 645 may transmit a registration request to the standalone network upon expiration of the back-off timer. In some examples, the registration component 645 may receive a registration accept message from the standalone network.

FIG. 7 shows a diagram of a system 700 including a device 705 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The device 705 may be an example of or include the components of device 405, device 505, or a UE 115 as described herein. The device 705 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 710, an I/O controller 715, a transceiver 720, an antenna 725, memory 730, and a processor 740. These components may be in electronic communication via one or more buses (e.g., bus 745) .

The communications manager 710 may establish a connection between the UE and a standalone network of a first radio access technology, determine, after establishing the connection, a radio link failure between the UE and the standalone network, identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time, disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time, and establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE.

The I/O controller 715 may manage input and output signals for the device 705. The I/O controller 715 may also manage peripherals not integrated into the device 705. In some cases, the I/O controller 715 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 715 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 715 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 715 may be implemented as part of a processor. In some cases, a user may interact with the device 705 via the I/O controller 715 or via hardware components controlled by the I/O controller 715.

The transceiver 720 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described herein. For example, the transceiver 720 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 720 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 725. However, in some cases the device may have more than one antenna 725, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 730 may include random-access memory (RAM) and read-only memory (ROM) . The memory 730 may store computer-readable, computer-executable code 735 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 730 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 740 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 740 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 740. The processor 740 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 730) to cause the device 705 to perform various functions (e.g., functions or tasks supporting management of unstable standalone communications) .

The code 735 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 735 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 735 may not be directly executable by the processor 740 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 8 shows a flowchart illustrating a method 800 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The operations of method 800 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 800 may be performed by a communications manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At 805, the UE may establish a connection between the UE and a standalone network of a first radio access technology. The operations of 805 may be performed according to the methods described herein. In some examples, aspects of the operations of 805 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 810, the UE may determine, after establishing the connection, a radio link failure between the UE and the standalone network. The operations of 810 may be performed according to the methods described herein. In some examples, aspects of the operations of 810 may be performed by a radio link failure component as described with reference to FIGs. 4 through 7.

At 815, the UE may identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time. The operations of 815 may be performed according to the methods described herein. In some examples, aspects of the operations of 815 may be performed by a radio link failure component as described with reference to FIGs. 4 through 7.

At 820, the UE may disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time. The operations of 820 may be performed according to the methods described herein. In some examples, aspects of the operations of 820 may be performed by a network disabling component as described with reference to FIGs. 4 through 7.

At 825, the UE may establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE. The operations of 825 may be performed according to the methods described herein. In some examples, aspects of the operations of 825 may be performed by a dual connectivity component as described with reference to FIGs. 4 through 7.

FIG. 9 shows a flowchart illustrating a method 900 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The operations of method 900 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 900 may be performed by a communications manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At 905, the UE may establish a connection between the UE and a standalone network of a first radio access technology. The operations of 905 may be performed according to the methods described herein. In some examples, aspects of the operations of 905 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 910, the UE may determine, after establishing the connection, a radio link failure between the UE and the standalone network. The operations of 910 may be performed according to the methods described herein. In some examples, aspects of the operations of 910 may be performed by a radio link failure component as described with reference to FIGs. 4 through 7.

At 915, the UE may transmit a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network. The operations of 915 may be performed according to the methods described herein. In some examples, aspects of the operations of 915 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 920, the UE may receive a connection set up request from the standalone network after transmitting the connection re-establishment request. The operations of 920 may be performed according to the methods described herein. In some examples, aspects of the operations of 920 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 925, the UE may re-establish connectivity with the standalone network based on completion of a connection set up. The operations of 925 may be performed according to the methods described herein. In some examples, aspects of the operations of 925 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 930, the UE may increment a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of a set of radio link failures. The operations of 930 may be performed according to the methods described herein. In some examples, aspects of the operations of 930 may be performed by a counter component as described with reference to FIGs. 4 through 7.

At 935, the UE may disable a standalone network connectivity of the UE based on the set of radio link failures being within a predetermined period of time. In some cases, disabling the standalone network connectivity of the UE is further based on the counter exceeding a threshold value within the predetermined period of time. The operations of 935 may be performed according to the methods described herein. In some examples, aspects of the operations of 935 may be performed by a network disabling component as described with reference to FIGs. 4 through 7.

At 940, the UE may establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based on the disabling of the standalone network connectivity of the UE. The operations of 940 may be performed according to the methods described herein. In some examples, aspects of the operations of 940 may be performed by a dual connectivity component as described with reference to FIGs. 4 through 7.

FIG. 10 shows a flowchart illustrating a method 1000 that supports management of unstable standalone communications in accordance with aspects of the present disclosure. The operations of method 1000 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1000 may be performed by a communications manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At 1005, the UE may establish a connection between the UE and a standalone network of a first radio access technology. The operations of 1005 may be performed according to the methods described herein. In some examples, aspects of the operations of 1005 may be performed by a connection establishment component as described with reference to FIGs. 4 through 7.

At 1010, the UE may determine, after establishing the connection, a radio link failure between the UE and the standalone network. The operations of 1010 may be performed according to the methods described herein. In some examples, aspects of the operations of 1010 may be performed by a radio link failure component as described with reference to FIGs. 4 through 7.

At 1015, the UE may identify that the radio link failure is one of a set of radio link failures between the UE and the standalone network within a predetermined period of time. The operations of 1015 may be performed according to the methods described herein. In some examples, aspects of the operations of 1015 may be performed by a radio link failure component as described with reference to FIGs. 4 through 7.

At 1020, the UE may disable a standalone network connectivity of the UE based on the set of radio link failures being within the predetermined period of time. The operations of 1020 may be performed according to the methods described herein. In some examples, aspects of the operations of 1020 may be performed by a network disabling component as described with reference to FIGs. 4 through 7.

At 1025, the UE may initiate a back-off timer upon disabling the standalone network connectivity of the UE. The operations of 1025 may be performed according to the methods described herein. In some examples, aspects of the operations of 1025 may be performed by a timer component as described with reference to FIGs. 4 through 7.

At 1030, the UE may transmit a deregistration request to the standalone network upon initiating the back-off timer. The operations of 1030 may be performed according to the methods described herein. In some examples, aspects of the operations of 1030 may be performed by a deregistration component as described with reference to FIGs. 4 through 7.

At 1035, the UE may receive a deregistration accept message from the standalone network. The operations of 1035 may be performed according to the methods described herein. In some examples, aspects of the operations of 1035 may be performed by a deregistration component as described with reference to FIGs. 4 through 7.

It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

Example 1: A method of wireless communication at a UE, comprising: establishing a connection between the UE and a standalone network of a first radio access technology; determining, after establishing the connection, a radio link failure between the UE and the standalone network; identifying that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time; disabling a standalone network connectivity of the UE based at least in part on the plurality of radio link failures being within the predetermined period of time; and establishing dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based at least in part on the disabling of the standalone network connectivity of the UE.

Example 2: The method of example 1, further comprising: transmitting a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network; receiving a connection set up request from the standalone network after transmitting the connection re-establishment request; and re-establishing connectivity with the standalone network based at least in part on completion of a connection set up.

Example 3: The method of any of examples 1 or 2, further comprising: incrementing a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the plurality of radio link failures, wherein disabling the standalone network connectivity of the UE is further based at least in part on the counter exceeding a threshold value within the predetermined period of time.

Example 4: The method of any of examples 1 to 3, further comprising: initiating a back-off timer upon disabling the standalone network connectivity of the UE.

Example 5: The method of any of examples 1 to 4, further comprising: transmitting a deregistration request to the standalone network upon initiating the back-off timer; and receiving a deregistration accept message from the standalone network.

Example 6: The method of any of examples 1 to 5, further comprising: transmitting an attach request to the anchor cell of the second radio access technology based at least in part on receiving the deregistration accept message from the standalone network; receiving an attach accept message from the anchor cell of the second radio access technology; and activating an evolved packet system bearer upon receiving the attach accept message.

Example 7: The method of any of examples 1 to 6, wherein the attach request comprises an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio.

Example 8: The method of any of examples 1 to 7, further comprising: re-enabling connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.

Example 9: The method of any of examples 1 to 8, further comprising: transmitting a registration request to the standalone network upon expiration of the back-off timer; and receiving a registration accept message from the standalone network.

Example 10: The method of any of examples 1 to 9, further comprising: performing a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.

Example 11: The method of any of examples 1 to 10, wherein the first radio access technology is a fifth generation (5G) network and the second radio access technology is a 4G network.

Example 12: An apparatus comprising at least one means for performing a method of any of examples 1 to 11.

Example 13: An apparatus for wireless communications comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of examples 1 to 11.

Example 14: A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to perform a method of any of examples 1 to 11.

Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

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 example 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. ”

In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other examples. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A method for wireless communication at a user equipment (UE) , comprising:

establishing a connection between the UE and a standalone network of a first radio access technology;

determining, after establishing the connection, a radio link failure between the UE and the standalone network;

identifying that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time;

disabling a standalone network connectivity of the UE based at least in part on the plurality of radio link failures being within the predetermined period of time; and

establishing dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based at least in part on the disabling of the standalone network connectivity of the UE.
The method of claim 1, further comprising:

transmitting a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network;

receiving a connection set up request from the standalone network after transmitting the connection re-establishment request; and

re-establishing connectivity with the standalone network based at least in part on completion of a connection set up.
The method of claim 2, further comprising.

incrementing a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the plurality of radio link failures, wherein disabling the standalone network connectivity of the UE is further based at least in part on the counter exceeding a threshold value within the predetermined period of time.
The method of claim 1, further comprising:

initiating a back-off timer upon disabling the standalone network connectivity of the UE.
The method of claim 4, further comprising:

transmitting a deregistration request to the standalone network upon initiating the back-off timer; and

receiving a deregistration accept message from the standalone network.
The method of claim 5, wherein establishing the dual connectivity further comprises:

transmitting an attach request to the anchor cell of the second radio access technology based at least in part on receiving the deregistration accept message from the standalone network;

receiving an attach accept message from the anchor cell of the second radio access technology; and

activating an evolved packet system bearer upon receiving the attach accept message.
The method of claim 6, wherein the attach request comprises an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio.
The method of claim 4, further comprising:

re-enabling connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.
The method of claim 8, wherein re-enabling the connectivity between the UE and the standalone network comprises:

transmitting a registration request to the standalone network upon expiration of the back-off timer; and

receiving a registration accept message from the standalone network.
The method of claim 1, wherein establishing the connection between the UE and the standalone network of the first radio access technology comprises:

performing a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.
The method of claim 1, wherein the first radio access technology is a fifth generation (5G) network and the second radio access technology is a 4G network.
An apparatus for wireless communication at a user equipment (UE) , comprising:

a processor,

memory coupled with the processor; and

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

establish a connection between the UE and a standalone network of a first radio access technology;

determine, after establishing the connection, a radio link failure between the UE and the standalone network;

identify that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time;

disable a standalone network connectivity of the UE based at least in part on the plurality of radio link failures being within the predetermined period of time; and

establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based at least in part on the disabling of the standalone network connectivity of the UE.
The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network;

receive a connection set up request from the standalone network after transmitting the connection re-establishment request; and

re-establish connectivity with the standalone network based at least in part on completion of a connection set up.
The apparatus of claim 13, wherein the instructions are further executable by the processor to cause the apparatus to:

increment a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the plurality of radio link failures, wherein disabling the standalone network connectivity of the UE is further based at least in part on the counter exceeding a threshold value within the predetermined period of time.
The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to:

initiate a back-off timer upon disabling the standalone network connectivity of the UE.
The apparatus of claim 15, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit a deregistration request to the standalone network upon initiating the back-off timer; and

receive a deregistration accept message from the standalone network.
The apparatus of claim 16, wherein the instructions to establish the dual connectivity further are executable by the processor to cause the apparatus to:

transmit an attach request to the anchor cell of the second radio access technology based at least in part on receiving the deregistration accept message from the standalone network;

receive an attach accept message from the anchor cell of the second radio access technology; and

activate an evolved packet system bearer upon receiving the attach accept message.
The apparatus of claim 17, wherein the attach request comprises an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio.
The apparatus of claim 15, wherein the instructions are further executable by the processor to cause the apparatus to:

re-enable connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.
The apparatus of claim 19, wherein the instructions to re-enable the connectivity between the UE and the standalone network are executable by the processor to cause the apparatus to:

transmit a registration request to the standalone network upon expiration of the back-off timer; and

receive a registration accept message from the standalone network.
The apparatus of claim 12, wherein the instructions to establish the connection between the UE and the standalone network of the first radio access technology are executable by the processor to cause the apparatus to:

perform a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.
The apparatus of claim 12, wherein the first radio access technology is a fifth generation (5G) network and the second radio access technology is a 4G network.
An apparatus for wireless communication at a user equipment (UE) , comprising:

means for establishing a connection between the UE and a standalone network of a first radio access technology;

means for determining, after establishing the connection, a radio link failure between the UE and the standalone network;

means for identifying that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time;

means for disabling a standalone network connectivity of the UE based at least in part on the plurality of radio link failures being within the predetermined period of time; and

means for establishing dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based at least in part on the disabling of the standalone network connectivity of the UE.
The apparatus of claim 23, further comprising:

means for transmitting a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network;

means for receiving a connection set up request from the standalone network after transmitting the connection re-establishment request; and

means for re-establishing connectivity with the standalone network based at least in part on completion of a connection set up.
The apparatus of claim 24, further comprising:

means for incrementing a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the plurality of radio link failures, wherein disabling the standalone network connectivity of the UE is further based at least in part on the counter exceeding a threshold value within the predetermined period of time.
The apparatus of claim 23, further comprising:

means for initiating a back-off timer upon disabling the standalone network connectivity of the UE.
The apparatus of claim 26, further comprising:

means for transmitting a deregistration request to the standalone network upon initiating the back-off timer; and

means for receiving a deregistration accept message from the standalone network.
The apparatus of claim 27, wherein the means for establishing the dual connectivity further comprises:

means for transmitting an attach request to the anchor cell of the second radio access technology based at least in part on receiving the deregistration accept message from the standalone network;

means for receiving an attach accept message from the anchor cell of the second radio access technology; and

means for activating an evolved packet system bearer upon receiving the attach accept message.
The apparatus of claim 28, wherein the attach request comprises an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio.
The apparatus of claim 26, further comprising:

means for re-enabling connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.
The apparatus of claim 30, wherein the means for re-enabling the connectivity between the UE and the standalone network comprises:

means for transmitting a registration request to the standalone network upon expiration of the back-off timer; and

means for receiving a registration accept message from the standalone network.
The apparatus of claim 23, wherein the means for establishing the connection between the UE and the standalone network of the first radio access technology comprises:

means for performing a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.
The apparatus of claim 23, wherein the first radio access technology is a fifth generation (5G) network and the second radio access technology is a 4G network.
A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE) , the code comprising instructions executable by a processor to:

establish a connection between the UE and a standalone network of a first radio access technology;

determine, after establishing the connection, a radio link failure between the UE and the standalone network;

identify that the radio link failure is one of a plurality of radio link failures between the UE and the standalone network within a predetermined period of time;

disable a standalone network connectivity of the UE based at least in part on the plurality of radio link failures being within the predetermined period of time; and

establish dual connectivity with an anchor cell of a second radio access technology and a secondary cell of the first radio access technology based at least in part on the disabling of the standalone network connectivity of the UE.
The non-transitory computer-readable medium of claim 34, wherein the instructions are further executable to:

transmit a connection re-establishment request to the standalone network in response to determining the radio link failure between the UE and the standalone network;

receive a connection set up request from the standalone network after transmitting the connection re-establishment request; and

re-establish connectivity with the standalone network based at least in part on completion of a connection set up.
The non-transitory computer-readable medium of claim 35, wherein the instructions are further executable to:

increment a counter each time the connectivity with the standalone network is re-established followed by a radio link failure of the plurality of radio link failures, wherein disabling the standalone network connectivity of the UE is further based at least in part on the counter exceeding a threshold value within the predetermined period of time.
The non-transitory computer-readable medium of claim 34, wherein the instructions are further executable to:

initiate a back-off timer upon disabling the standalone network connectivity of the UE.
The non-transitory computer-readable medium of claim 37, wherein the instructions are further executable to:

transmit a deregistration request to the standalone network upon initiating the back-off timer; and

receive a deregistration accept message from the standalone network.
The non-transitory computer-readable medium of claim 38, wherein the instructions to establish the dual connectivity further are executable to:

transmit an attach request to the anchor cell of the second radio access technology based at least in part on receiving the deregistration accept message from the standalone network;

receive an attach accept message from the anchor cell of the second radio access technology; and

activate an evolved packet system bearer upon receiving the attach accept message.
The non-transitory computer-readable medium of claim 39, wherein the attach request comprises an indication of a capability to support dual connectivity with Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and New Radio.
The non-transitory computer-readable medium of claim 37, wherein the instructions are further executable to:

re-enable connectivity between the UE and the standalone network of the first radio access technology upon expiration of the back-off timer.
The non-transitory computer-readable medium of claim 41, wherein the instructions to re-enable the connectivity between the UE and the standalone network are executable to:

transmit a registration request to the standalone network upon expiration of the back-off timer; and

receive a registration accept message from the standalone network.
The non-transitory computer-readable medium of claim 34, wherein the instructions to establish the connection between the UE and the standalone network of the first radio access technology are executable to:

perform a radio resource control procedure with the standalone network of the first radio access technology to establish the connection.
The non-transitory computer-readable medium of claim 34, wherein the first radio access technology is a fifth generation (5G) network and the second radio access technology is a 4G network.