WO2021056166A1

WO2021056166A1 - Recovery from master node link failure in dual-connectivity systems using bearer

Info

Publication number: WO2021056166A1
Application number: PCT/CN2019/107423
Authority: WO
Inventors: Punyaslok PURKAYASTHA; Gavin Bernard Horn; Peng Cheng; Xipeng Zhu
Original assignee: Qualcomm Incorporated
Priority date: 2019-09-24
Filing date: 2019-09-24
Publication date: 2021-04-01

Abstract

Methods, systems, and devices for wireless communications are described. A wireless device may be configured to communicate with a master node and a secondary node. If a master cell group associated with the master node fails, the wireless device may initiate or perform a master cell group recovery procedure. The master cell group recovery procedure may include using a secondary signaling radio bearer to transmit failure information related to the master cell group failure when a split signaling radio bearer is not configured. The secondary node may relay the master cell group failure information to the master node, which may determine a network response based on the master cell group failure information. The master node may transmit the network response to the secondary cell, which may relay the network response to the wireless device.

Description

RECOVERY FROM MASTER NODE LINK FAILURE IN DUAL-CONNECTIVITY SYSTEMS USING BEARER

FIELD OF TECHNOLOGY

The following relates generally to wireless communications and more specifically to recovery from master node link failure in dual-connectivity systems using signaling radio bearers.

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) .

In some examples, a UE may communicate with a network using first network access node that uses a radio access technology (RAT) and a second access node that uses the same or a different RAT. A UE that uses two network access nodes to communicate with a network may be referred to as operating in a dual-connectivity mode. Failure of a node in such a dual-connectivity mode presents challenges.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support recovering from a master node link failure. In some examples, a “master signaling radio bearer” may be configured between a wireless device, such as a UE, and a master node associated with a first radio access technology (RAT) . A “secondary signaling radio bearer” may be configured between the wireless device and a secondary node associated with a second RAT. A “split signaling radio bearer” may be configured between the wireless device, the master node, and the secondary node. A control signaling interface (e.g., an X2 or Xn interface) may be configured between the master node and the secondary node and may provide a signaling path between higher layers of the master node and the secondary node. In some examples, a radio link between a wireless device and a master node may fail. To recover a connection between a wireless device and a communications network after a master cell group failure, the split signaling radio bearer or the secondary signaling radio bearer or both may be used.

In some examples, a split signaling radio bearer may be prioritized over a secondary signaling radio bearer for the signaling of recovery. In some examples, additional or modified signaling or both may be used to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured. For example, a radio resource control (RRC) message used to convey information for dual-connectivity operation from a wireless device to a node may be modified to include an RRC message that includes information related to an MCG failure. Additionally, higher-layer containers used to convey information between nodes may be modified or added to convey the RRC message including information related to the MCG failure. Similarly, higher-layer containers used to convey information between nodes may be modified or added to convey a network response determined by the master node based on the received MCG failure information. Also, an RRC message used to convey the network response from the secondary node to the wireless device may be added. By using an added RRC message to convey the network response, a secondary node may avoid generating RRC message (s) corresponding to the network response and transmitting the secondary node-generated RRC message (s) to the wireless device. In some examples, a secondary node may generate RRC message (s) corresponding to the network response and transmit the RRC message (s) generated by the secondary node to the wireless device.

A method of wireless communications at a UE is described. The method may include receiving a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology, configuring a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based on receiving the configuration, detecting a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection, and initiating a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

An apparatus for wireless communications 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 receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology, configure a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based on receiving the configuration, detect a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection, and initiate a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

Another apparatus for wireless communications at a UE is described. The apparatus may include means for receiving a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology, configuring a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based on receiving the configuration, detecting a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection, and initiating a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

A non-transitory computer-readable medium storing code for wireless communications at a UE is described. The code may include instructions executable by a processor to receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology, configure a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based on receiving the configuration, detect a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection, and initiate a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the secondary signaling radio bearer between the UE and the secondary node before the failure of the master cell group may be detected based on receiving the configuration, determining that the split signaling radio bearer may be not configured based on detecting the failure of the master cell group, and transmitting, as part of the recovery procedure, a radio resource control message including information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the secondary signaling radio bearer based on determining that the split signaling radio bearer may be not configured.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the radio resource control message may include operations, features, means, or instructions for ciphering the radio resource control message based on a key associated with the master node.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a second radio resource control message includes the information, the second radio resource control message including an MCGFailureInformation message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the secondary node over the secondary cell group and as part of the recovery procedure, a second radio resource control message including a response associated with the master node, where the response may be based on the information, and managing, as part of the recovery procedure, the first radio resource control connection based on the response.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a third radio resource control configuration message originating from the master node includes the response.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a radio resource control reconfiguration message or a radio resource control release message originating from the master node includes the response.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, managing the first radio resource control connection may include operations, features, means, or instructions for performing a handover procedure between the master node and a target master node based on receiving the radio resource control reconfiguration message. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring a master signaling radio bearer between the UE and the target master node; and transmitting, to the target master node via the master signaling radio bearer, a third radio resource control message indicating a radio resource control reconfiguration is complete. In some cases, the third radio resource control message comprises an RRCReconfigurationComplete message

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, managing the first radio resource control connection may include operations, features, means, or instructions for releasing the first radio resource control connection based on receiving the radio resource control release message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second radio resource control message includes a radio resource control reconfiguration message or a radio resource control release message originating from the secondary node.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second radio resource control includes a DLInformationTransferMRDC message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the split signaling radio bearer between the UE, the master node, and the secondary node before the failure of the master cell group may be detected based on receiving the configuration, determining that the split signaling radio bearer may be configured based on detecting the failure of the master cell group, and transmitting, as part of the recovery procedure, a radio resource control message including information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the split signaling radio bearer based on determining that the split signaling radio bearer may be configured.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the radio resource control message includes an ULInformationTransferMRDC message, the radio resource control message being ciphered based on a key associated with the master node.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the secondary node over the secondary node and as part of the recovery procedure, a response originating from the master node based on the information, and managing, as part of the recovery procedure, the first radio resource control connection based on the response.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the secondary signaling radio bearer before the failure of the master cell group may be detected based on receiving the configuration.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, initiating the recovery procedure may include operations, features, means, or instructions for determining that the split signaling radio bearer and the secondary signaling radio bearer may be not configured based on detecting the failure of the master cell group, and performing, as part of the recovery procedure, a radio resource control connection reestablishment procedure based on the determining.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the split signaling radio bearer includes a split signaling radio bearer 1 (SRB1) and the secondary signaling radio bearer includes a signaling radio bearer 3 (SRB3) .

A method of wireless communications at a secondary node associated with a second radio access technology is described. The method may include receiving a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology, configuring a first radio resource control connection between the UE and the secondary node based on receiving the configuration, receiving an indication of a failure of the master cell group after configuring the first radio resource control connection, and initiating a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

An apparatus for wireless communications at a secondary node associated with a second radio access technology 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 receive a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology, configure a first radio resource control connection between the UE and the secondary node based on receiving the configuration, receive an indication of a failure of the master cell group after configuring the first radio resource control connection, and initiate a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

Another apparatus for wireless communications at a secondary node associated with a second radio access technology is described. The apparatus may include means for receiving a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology, configuring a first radio resource control connection between the UE and the secondary node based on receiving the configuration, receiving an indication of a failure of the master cell group after configuring the first radio resource control connection, and initiating a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

A non-transitory computer-readable medium storing code for wireless communications at a secondary node associated with a second radio access technology is described. The code may include instructions executable by a processor to receive a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology, configure a first radio resource control connection between the UE and the secondary node based on receiving the configuration, receive an indication of a failure of the master cell group after configuring the first radio resource control connection, and initiate a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the secondary signaling radio bearer before receiving the indication of the failure of the master cell group based on receiving the configuration, where the receiving includes receiving, over the secondary cell group and via the secondary signaling radio bearer, a radio resource control message comprising the indication of the failure of the master cell group from the UE, the indication comprising information associated with the failure of the master cell group.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for encapsulating, as part of the recovery procedure, the information associated with the failure of the master cell group in a higher-layer container, and transmitting, as part of the recovery procedure, the higher-layer container to the master node via a control interface between the secondary node and the master node.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the higher-layer container includes a radio resource control transfer message, and where the control interface includes one or both of an Xn interface or an X2 interface.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the master node, a response that may be encapsulated in a second higher-layer container based on transmitting the higher-layer container, where the response includes a second radio resource control message including information for managing a second radio resource control connection configured between the UE and the master node.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for encapsulating the second radio resource control message in a third radio resource control message, and transmitting the third radio resource control message to the UE over the secondary cell group and via the secondary signaling radio bearer.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for generating a third radio resource control message based on the information for managing the second radio resource control connection, where generating the third radio resource control message includes generating a radio resource control reconfiguration message or a radio resource control release message, and transmitting the third radio resource control message to the UE over the secondary cell group via the secondary signaling radio bearer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the third radio resource control message includes a DLInformationTransferMRDC message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the split signaling radio bearer before receiving the indication of the failure of the master cell group based on receiving the configuration, where the receiving includes receiving, from the UE, the indication of the failure of the master cell group over the secondary cell group and via the split signaling radio bearer, the indication comprising information associated with the failure of the master cell group; and relaying the indication of the failure of the master cell group to the master node via the split signaling radio bearer.

A method of wireless communications at a master node associated with a first radio access technology is described. The method may include receiving a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology, configuring a first radio resource control connection between the UE and the master node based on the configuration, identifying a failure of the master cell group after configuring the first radio resource control connection, and initiating a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

An apparatus for wireless communications at a master node associated with a first radio access technology 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 receive a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology, configure a first radio resource control connection between the UE and the master node based on the configuration, identify a failure of the master cell group after configuring the first radio resource control connection, and initiate a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

Another apparatus for wireless communications at a master node associated with a first radio access technology is described. The apparatus may include means for receiving a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology, configuring a first radio resource control connection between the UE and the master node based on the configuration, identifying a failure of the master cell group after configuring the first radio resource control connection, and initiating a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configura-le between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

A non-transitory computer-readable medium storing code for wireless communications at a master node associated with a first radio access technology is described. The code may include instructions executable by a processor to receive a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology, configure a first radio resource control connection between the UE and the master node based on the configuration, identify a failure of the master cell group after configuring the first radio resource control connection, and initiate a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the identifying may include operations, features, means, or instructions for receiving an indication of the failure of the master cell group based on receiving an MCGFailureInformation message; or, and determining the failure of the master cell group.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the secondary signaling radio bearer may be configured before the failure of the master cell group may be identified, and where the receiving may include operations, features, means, or instructions for receiving, over a control interface configured between the master node and the secondary node, a radio resource control message including the indication of the failure of the master cell group from the secondary node, the indication including information associated with the failure of the master cell group.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the control interface includes one or both of an Xn interface or an X2 interface.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, as part of the recovery procedure, an action for managing the first radio resource control connection configured between the UE and the master node based on the information included in the indication, and transmitting, as part of the recovery procedure, a second radio resource control message including a response to the secondary node via the control interface.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the higher-layer container includes a radio resource control transfer message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a radio resource control reconfiguration message or a radio resource control release message includes the response.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for encapsulating, as part of the recovery procedure, the second radio resource control message in a second higher-layer container, where transmitting the second radio resource control message includes transmitting the second higher-layer container to the secondary node via the control interface.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for ciphering the response based on a key associated with the master node.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the split signaling radio bearer may be configured before the failure of the master cell group may be identified, and where the receiving may include operations, features, means, or instructions for receiving the indication of the failure of the master cell group from the secondary node via the split signaling radio bearer, the indication including information associated with the failure of the master cell group.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a second radio resource control connection may be configured between the UE and the secondary node based on receiving the configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system that supports recovering from a master node link failure in accordance with various aspects of the present disclosure.

FIG. 2 illustrates aspects of a wireless communications subsystem that supports recovering from a master node link failure in accordance with various aspects of the present disclosure.

FIG. 3 illustrates aspects of a process for recovering from a master node link failure in accordance with various aspects of the present disclosure.

FIG. 4 shows a block diagram of a device that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIG. 5 shows a block diagram of a communications manager that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIG. 6 shows a diagram of a system including a device that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIGs 7 shows a block diagrams of a device that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIG. 8 shows a block diagram of a communications manager that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIG. 9 shows a diagram of a system including a device that supports recovering from a master node link failure in accordance with aspects of the present disclosure.

FIGs. 10 through 12 show flowcharts illustrating methods that support recovering from a master node link failure in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless networks may be configured to operate in a dual-connectivity (DC) configuration. For example, the wireless network may be configured to operate in an evolved universal terrestrial radio access network (E-UTRAN) in new radio (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 a long-term evolution (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) . Broadly, the dual-connectivity configuration leverages benefits of both LTE and 5G functionalities and capabilities concurrently to improve overall system performance.

In some examples, a “master signaling radio bearer” may be configured between a wireless device, such as a UE, and a master node associated with a first radio access technology (RAT) . A master signaling radio bearer (e.g., SRB1) may be a bearer that provides a signaling path between higher layers of the wireless device and the master node. A “secondary signaling radio bearer” may be configured between the wireless device and a secondary node associated with a second RAT. A secondary signaling radio bearer (e.g., SRB3) may be a bearer that provides a signaling path between higher layers of the wireless device and the secondary node. A “split signaling radio bearer” may be configured between the wireless device, the master node, and the secondary node. A split signaling radio bearer (e.g., split SRB1) may be a bearer that provides a signaling path between higher layers of the wireless device, the master node, and the secondary node. A control signaling interface (e.g., an X2 or Xn interface) may be configured between the master node and the secondary node and may provide a signaling path between higher layers of the master node and the secondary node. In some examples, a radio link between a wireless device and a master node may fail-e.g., a master cell group (MCG) associated with the master node may fail.

To recover a connection between a wireless device and a communications network after a master cell group failure, the split signaling radio bearer or the secondary signaling radio bearer or both may be used. To support recovery procedures over the split signaling radio bearer or the secondary signaling radio bearer or both, techniques for signaling recovery information over the split signaling radio bearer or the secondary signaling radio bearer (or both) may be performed.

In some examples, a split signaling radio bearer may be prioritized over a secondary signaling radio bearer for the signaling of recovery information-e.g., because a recovery procedure performed over the split signaling radio bearer may be less complex than a recovery procedure performed over the secondary signaling radio bearer. In some examples, additional or modified signaling or both may be used to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured. For example, a radio resource control (RRC) message used to convey information for dual-connectivity operation from a wireless device to a node may be modified to include an RRC message that includes information related to an MCG failure. Additionally, higher-layer containers used to convey information between nodes may be modified or added to convey the RRC message including information related to the MCG failure. Similarly, higher-layer containers used to convey information between nodes may be modified or added to convey a network response determined by the master node based on the received MCG failure information.

Also, an RRC message used to convey the network response from the secondary node to the wireless device may be added. By using an added RRC message to convey the network response, a secondary node may avoid generating RRC message (s) corresponding to the network response and transmitting the secondary node-generated RRC message (s) to the wireless device. That said, In some examples, a secondary node may generate RRC message (s) corresponding to the network response and transmit the RRC message (s) generated by the secondary node to the wireless device.

Aspects of the disclosure are initially described in the context of a wireless communications system. Specific examples are then described of a process for performing a recovery procedure over a split or secondary signaling radio bearer (or both) . Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to recovering from a master node link failure.

The wireless communications system 100 includes base stations 105, 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 a NR network. In some examples, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

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

Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in 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. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

The geographic coverage area 110 for a base station 105 may be divided into sectors making up a portion of the geographic coverage area 110, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 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, and overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

The term “cell” refers 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) ) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband Internet-of-Things (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of devices. In some examples, the term “cell” may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which the logical entity operates.

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

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 that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs 115 may be designed to collect information or enable automated behavior of machines. 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 UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications) . In some examples, UEs 115 may be designed to support critical functions (e.g., mission critical functions) , and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

In some examples, a UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol) . One or more of a group of 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 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 UEs 115 without the involvement of a base station 105.

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1, N2, N3, or another interface) . Base stations 105 may communicate with one another over backhaul links 134 (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) .

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) , which may include at least one mobility management entity (MME) , at least one serving gateway (S-GW) , and at least one Packet Data Network (PDN) gateway (P-GW) . The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be transferred through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the network operators IP services. The operators IP services may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC) . Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP) . In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105) .

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, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves may penetrate structures sufficiently for a macro cell to provide service to UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter range (e.g., less than 100 km) 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.

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. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that may be capable of tolerating interference from other users.

Wireless communications system 100 may also operate 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, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a UE 115. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. 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.

In some examples, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, 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 ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. 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, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) , or a combination of both.

In some examples, base station 105 or 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. For example, wireless communications system 100 may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115) , where the transmitting device is equipped with multiple antennas and the receiving device is equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which 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. 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 or a UE 115) to shape or steer an antenna beam (e.g., a transmit beam or 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 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 certain amplitude and phase offsets to signals carried via each of 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) .

In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For example, 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, which may include a signal being transmitted 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 the base station 105 or a receiving device, such as a UE 115) a beam direction for subsequent transmission and/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 at least in in part on a signal that was transmitted in different 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 the UE 115 may report to the base station 105 an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. 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 transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115, which may be an example of a mmW receiving device) may try multiple receive beams 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 applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive beams or receive directions. In some examples a receiving device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal) . The single receive beam may be aligned in a beam direction determined based at least in part on listening according to different receive beam directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio, or otherwise acceptable signal quality based at least in part on listening according to multiple beam directions) .

In some examples, the antennas of a base station 105 or UE 115 may be located within one or more antenna arrays, 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.

In some examples, wireless communications system 100 may be a packet-based network that operate 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 hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the RRC protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting signaling radio bearers for user plane data. At the Physical layer, transport channels may be mapped to physical channels.

In some examples, UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique of 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., signal-to-noise conditions) . In some examples, a wireless 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.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of Ts = 1/30,720,000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (ms) , where the frame period may be expressed as Tf = 307,200 Ts. The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some examples, a subframe may be the smallest scheduling unit of the wireless communications system 100 and may be referred to as a transmission time interval (TTI) . In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs) .

In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols. In some examples, a symbol of a mini-slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Further, some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots are aggregated together and used for communication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that is operated according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a pre-defined 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 UEs 115. Carriers may be downlink or uplink (e.g., in an FDD mode) , or be configured to carry downlink and uplink communications (e.g., in a TDD mode) . In some examples, signal waveforms transmitted over a carrier may be made up of multiple sub-carriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM) ) .

The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR) . For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc. ) and control signaling that coordinates operation for the carrier. 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.

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 time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in a physical control channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces) .

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 predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz) . In some examples, each served UE 115 may be configured for operating over portions or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type) .

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) . 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. In MIMO systems, 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) , and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports 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 and/or UEs 115 that support simultaneous communications via carriers associated with more than one different carrier bandwidth.

Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as 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 FDD and TDD component carriers.

In some examples, wireless communications system 100 may utilize enhanced component carriers (eCCs) . An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some examples, an eCC may be associated with a carrier aggregation configuration or a dual-connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link) . An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum) . An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power) .

In some examples, an eCC may utilize a different symbol duration than other component carriers, which may include use of a reduced symbol duration as compared with symbol durations of the other component carriers. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc. ) at reduced symbol durations (e.g., 16.67 microseconds) . A TTI in eCC may consist of one or multiple symbol periods. In some examples, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

Wireless communications system 100 may be an NR system that may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across the frequency domain) and horizontal (e.g., across the time domain) sharing of resources.

A wireless communications system 100 may support dual-connectivity operation for a UE 115. That is, a UE 115 may be configured to establish and maintain multiple connections between multiple network nodes. In some examples, a first network node (e.g., a first base station 105) that is designated as a master node may use a first RAT (e.g., E-UTRA or NR) and a second network node (e.g., a second base station) that is designated as a secondary node may use a second RAT (e.g., E-UTRA NR) . In some examples, a first RRC connection may be configured between the UE 115 and the master node and a second RRC connection may be configured between the UE 115 and the secondary node.

A master signaling radio bearer may be configured between a UE 115 and a master node using a first RAT. A master signaling radio bearer (e.g., SRB1) may be a bearer that provides a signaling path between higher layers of the UE 115 and the master node. A secondary signaling radio bearer may be configured between the UE 115 and a secondary node using a second RAT. A secondary signaling radio bearer (e.g., SRB3) may be a bearer that provides a signaling path between higher layers of the UE 115 and the secondary node. A split signaling radio bearer may be configured between a UE 115, a master node, and a secondary node. A split signaling radio bearer (e.g., split SRB1) may be a bearer that provides a signaling path between higher layers of the UE 115, the master node, and the secondary node. A control signaling interface (e.g., X2 or Xn) may be configured between the master node and the secondary node and may provide a signaling path between higher layers of the master node and the secondary node. In some examples, a radio link between a UE 115 and a master node may fail-e.g., a master cell group may fail.

To recover a connection between a UE 115 and a communications network after a master cell group failure, the split signaling radio bearer and/or the secondary signaling radio bearer may be used. To support recovery procedures over the split signaling radio bearer and/or the secondary signaling radio bearer, techniques for signaling recovery information over the split signaling radio bearer and/or the secondary signaling radio bearer may be determined.

In some examples, a split signaling radio bearer may be prioritized over a secondary signaling radio bearer for the signaling of recovery information-e.g., because a recovery procedure performed over the split signaling radio bearer may be less complex than a recovery procedure performed over the secondary signaling radio bearer. In some examples, additional and/or modified signaling is used to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured.

Wireless communications subsystem 200 may include master node 207, which may be an example of a base station as described herein, including with reference to FIG. 1. Wireless communications subsystem 200 may include secondary node 209, which may be an example of a base station as described herein, including with reference to FIG. 1. Wireless communications subsystem 200 may include UE 215, which may be an example of a UE as described herein, including with reference to FIG. 1 Master node 207, secondary node 209, and UE 215 may communicate with one another using the techniques described herein, including with reference to FIG. 1.

UE 215 may be connected to master node 207 and secondary node 209 in a dual-connectivity configuration. Generally, the dual-connectivity configuration may include a network configured according to a 5G EN-DC or 5G NR dual-connectivity configuration. In some examples, the master node 207 may be associated with a 5G (e.g., NR) RAT and the secondary node 209 may be associated with an LTE RAT. In other examples, both of the master node 207 and the secondary node 209 may be associated with a 5G (e.g., NR) RAT. In other examples, both the master node 207 and the secondary node 209 may be associated with an LTE RAT. Generally, the described techniques may be applied to all multi-RAT dual-connectivity (MR-DC) configurations, which may also include NR-NR DC. Generally, UE 215 may connect to master node 207 and/or secondary node 209 via one or more wireless radio links, such as an MCG link 225 for master node 207 and an SCG link 230 for secondary node 209.

In some examples, master node 207 may be connected to secondary node 209 to exchange information via a wireless link and/or a wired link, such as a control interface 235 (e.g., an X2/Xn protocol connection) . One or both of master node 207 and secondary node 209 may also be connected to a core network 220 via a backhaul link, such as first network connection 240 and second network connection 245.

As discussed herein, a wireless device may use a split signaling radio bearer and/or a secondary signaling radio bearer configured at the wireless device to recover a connection between the wireless device and a communications network after a master cell group failure.

In some examples, a split signaling radio bearer may be prioritized over a secondary signaling radio bearer for the signaling of recovery information-e.g., because a recovery procedure performed over the split signaling radio bearer may be less complex than a recovery procedure performed over the secondary signaling radio bearer.

In some examples, additional and/or modified signaling may be used to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured. For example, an RRC message (which may be referred to as a ULInformationTransferMRDC message) used to convey uplink information for dual-connectivity operation from a wireless device to a node may be modified to support recovery procedures when a secondary signaling radio bearer is configured.

For example, the ULInformationTransferMRDC message may be used to convey one or more RRC messages including (1) an RRC message that includes measurements taken for the master or secondary link (which may be referred to as a MeasurementReport message) ; (2) an RRC message that includes information related to an RLC failure (which may be referred to as a FailureInformation message) ; and/or (3) an RRC message that includes information related to a failure of a master cell group (which may be referred to as a MCGFailureInformation message) .

Also, an RRC message (which may be referred to as a DLInformationTransferMRDC message) used to convey a network response determined by the master node from a secondary node to a UE may be introduced to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured. The DLInformationTransferMRDC message may include an RRC message directing the UE to reconfigure its RRC connection with the master node (which may be referred to as a FirstRAT_RRCReconfiguration message) or to release its RRC connection to the master node and/or the secondary node (which may be referred to as a FirstRAT_RRCRelease message) . In some examples, the FirstRAT_RRCReconfiguration message or the FirstRAT_RRCRelease message may be constructed by the master node and encapsulated by the secondary node in the DLInformationTransferMRDC message.

Also, higher-layer containers (e.g., RRC Transfer messages) that encapsulate RRC messages (e.g., an MCGFailureInformation message, a FirstRAT_RRCReconfiguration message, and/or a FirstRAT_RRCRelease message) and are transmitted between the master node and the secondary node may be modified and/or introduced to support recovery procedures when a secondary signaling radio bearer, and not a split signaling radio bearer, is configured.

For example, an MeNB RRC message may be introduced that contains FirstRAT_RRCReconfiguration or FirstRAT_RRCRelease messages, where a master node that uses a first RAT (e.g., E-UTRA) may use the MeNB RRC message to communicate the FirstRAT_RRCReconfiguration or FirstRAT_RRCRelease messages to a secondary node that uses a second RAT (e.g., NR) . In some examples, a UE Report message may be modified to contain an MCGFailureInformation message, where a secondary node that uses the first RAT may use the UE Report message to communicate the MCGFailureInformation message to a master node that uses the second RAT. In some examples, an E-UTRA UE Report message may be introduced that contains an MCGFailureInformation message, where a secondary node that uses the first RAT may use the E-UTRA UE Report message to communicate the MCGFailureInformation message to a master node that uses the second RAT.

Similarly, an MN RRC message may be introduced that contains FirstRAT_RRCReconfiguration or FirstRAT_RRCRelease messages, where a master node that uses a first RAT (e.g., NR) may use the MN RRC message to communicate the FirstRAT_RRCReconfiguration or FirstRAT_RRCRelease messages to a secondary node that uses a second RAT (e.g., E-UTRA or NR) . Also, a UE Report message may be modified to contain an MCGFailureInformation message, where a secondary node that uses the first RAT may use the UE Report message to communicate the MCGFailureInformation message to a master node that uses the second RAT.

In some examples, after detecting a radio link failure between UE 215 and a master node 207, UE 215 may determine whether a split signaling radio bearer (e.g., split SRB1) is configured, for example, before transmitting recovery signaling. If UE 215 determines that the split signaling radio bearer is configured, UE 215 may use the split signaling radio bearer to perform a recovery procedure. If UE 215 determines that the split signaling radio bearer is not configured, then UE 215 may determine whether the secondary signaling radio bearer (e.g., SRB3) is configured. If UE 215 determines that both the split signaling radio bearer and the secondary signaling radio bearer are not configured, UE 215 may initiate an RRC reestablishment procedure with the network. If UE 215 determines that the secondary signaling radio bearer is configured, however, the UE 215 may use the secondary signaling radio bearer to perform a recovery procedure.

After detecting a radio link failure and determining the secondary signaling radio bearer, and not the split signaling radio bearer, is configured, UE 215 may transmit an ULInformationTransferMRDC message to a secondary node 209 via the secondary signaling radio bearer.

After receiving the ULInformationTransferMRDC message via the secondary signaling radio bearer, the secondary node 209 may relay RRC message (s) included in the ULInformationTransferMRDC message (e.g., MeasurementReport message, FailureInformation message, and/or MCGFailureInformation message) to the master node 207 via an interface (e.g., an X2 or Xn interface) between the master node 207 and the secondary node 209. In some examples, the secondary node 209 encapsulates the RRC message (s) in a UE Report message or an E-UTRA UE Report message.

The master node 207 may process the RRC message (s) received from the secondary node 209 via the interface and determine a network response based on the information included in the RRC message (s) . For example, the master node 207 may determine that UE 215 should be handed off to another master node 207 (or a “target master node” ) or may determine that UE 215 should release an RRC connection. After determining the network response, the master node 207 select an RRC message (e.g., FirstRAT_RRCReconfiguration message or a FirstRAT_RRCRelease message) for conveying the network response.

In some examples, the master node 207 may transmit an RRC message directing UE to reconfigure its RRC connection with the master node 207-e.g., by sending a FirstRAT_RRCReconfiguration message-or to release its RRC connection with the master node 207 and/or the secondary node 209-e.g., by sending a FirstRAT_RRCRelease message) . After selecting the RRC message for conveying the network response, the master node 207 may transmit the RRC message to the secondary node 209 via the interface. In some examples, the master node 207 encapsulates the RRC message in an MeNB RRC message or an MN RRC Report message.

After receiving the RRC message conveying the network response via the interface, the secondary node 209 may provide the RRC message to UE 215. In some examples, the secondary node 209 may convey the RRC message by transmitting a DLInformationTransferMRDC message to UE 215 via the secondary signaling radio bearer. The DLInformationTransferMRDC message may include the information conveyed in a FirstRAT_RRCReconfiguration message or a FirstRAT_RRCRelease message received from the master node 207-e.g., the FirstRAT_RRCReconfiguration message or the FirstRAT_RRCRelease message may be embedded in, or encapsulated by, the DLInformationTransferMRDC message. Additionally or alternatively, the secondary node 209 may convey the network response by transmitting a SecondRAT_RRCReconfiguration message or a SecondRAT_RRCRelease message constructed by the secondary node 209 based on the information received in the FirstRAT_RRCReconfiguration message or the FirstRAT_RRCRelease message.

In some examples, the secondary node 209 may use the DLInformationTransferMRDC message to forward the network response to UE 215 based on the SecondRAT_RRCReconfiguration and SecondRAT_RRCRelease messages being solely configured to manage the RRC connection between the secondary node 209 and UE 215. That is, a SecondRAT_RRCReconfiguration message constructed by the secondary node 209 may not include information for directing UE 215 to reconfigure an RRC connection between UE 215 and another node-e.g., a SecondRAT_RRCReconfiguration message may be limited to directing UE 215 to reconfigure an RRC connection between UE 215 and the secondary node 209.

After receiving the network response from the secondary node 209 via the secondary signaling radio bearer, UE 215 may perform the indicated procedure. For example, UE 215 may engage in a handover procedure from the master node 207 to a target master node after receiving a FirstRAT_RRCReconfiguration message (e.g., within a DLInformationTransferMRDC message) from the secondary node 209. After completing the handover procedure, UE 215 may transmit an RRC message indicating that the reconfiguration of the RRC connection has been successfully completed (which may be referred to as an RRCReconfigurationComplete message) . In some examples, the RRCReconfigurationComplete message may be signaled over a master signaling radio bearer (e.g., SRB1) that is configured between UE 215 and target master node during the handover procedure-e.g., after performing a RACH procedure with the target master node. In other examples, UE 215 may release an RRC connection from the master node 207 and/or secondary node 209 after receiving a FirstRAT_RRCRelease message (e.g., within a DLInformationTransferMRDC message) from the secondary node 209.

Process flow 300 may be performed by UE 315 which may be an example of a UE described herein, including with reference to FIGs. 1-2. Process flow 300 may also be performed by master node 307 and secondary node 309 which may be examples of a master node, secondary node, and/or base station described herein, including with reference to FIGs. 1-2. In some examples, master node 307 uses a first RAT (e.g., LTE) and secondary node 309 uses a second RAT (e.g., 5G) . In some examples, master node 307 and secondary node 309 may exchange information with one another via a signaling control interface (e.g., Xn or X2) .

In some examples, process flow 300 illustrates a fast recovery procedure for a failed master radio link (or MCG) using a split signaling radio bearer and/or a secondary signaling radio bearer.

At arrow 320, UE 315, master node 307, and secondary node 309 may exchange control signaling (e.g., RRC signaling) . In some examples, UE 315 may indicate a capability to perform dual-connectivity operation to master node 307. In some examples, master node 307 may send a configuration to UE 315 that configures UE 315 for dual-connectivity operation. In some examples, master node 307 may also send a configuration to secondary node 309 configuring secondary node 309 to perform dual-connectivity communications with master node 307. In some examples, secondary node 309 may indicate a capability to perform dual-connectivity operation to master node 307.

In some examples, UE 315, secondary node 309, and master node 307 may exchange control signaling to establish RRC connections and signaling radio bearers. In some examples, UE 315 establishes an RRC connection with master node 307 before exchanging RRC signaling between UE 315 and master node 307. In some examples, UE 315 and master node 307 may exchange signaling to configure a master signaling radio bearer (e.g., SRB1) that provides a signaling path between higher layers of UE 315 and higher layers of master node 307. In some examples, after establishing an RRC connection with master node 307, UE 315 receives a configuration to configure a dual-connectivity mode. After configuring the dual-connectivity mode, UE 315 may establish an RRC connection with secondary node 309.

In some examples, UE 315 and secondary node 309 may exchange signaling to configure a secondary signaling radio bearer (e.g., SRB3) that provides a signaling path between higher layers of UE 315 and higher layers of secondary node 309. In some examples, UE 315, master node 307, and secondary node 309 exchange signaling to establish a split signaling radio bearer (e.g., split SRB1) that provides a direct signaling path between UE 315 and master node 307, a direct signaling path between UE 315 and secondary node 309, and an indirect signaling path between UE 315 and master node 307 that passes through (e.g., is relayed by) secondary node 309 to master node 307 over a control interface.

After establishing the one or RRC connections, UE 315 may begin exchanging communications between UE 315, master node 307, and/or secondary node 309. In some examples, communications between UE 315 and master node 307 using wireless resource (e.g., the PHY layer) may be performed over a master cell or master cell group. In some examples, RRC communications between UE 315 and master node 307 may be performed via a master signaling radio bearer or a split signaling radio bearer. In some examples, communications between UE 315 and secondary node 309 using wireless resources may be performed over a secondary cell or secondary cell group. In some examples, RRC communications between UE 315 and secondary node 309 may be performed over a secondary signaling radio bearer.

At block 325, UE 315 may detect a master cell group failure. In some examples, UE 315 may detect the master cell group failure based on one or more channel measurements performed by UE 315, among other examples. In some examples, master node 307 may also detect a master cell group failure-e.g., based on failing to receive a scheduled communication from UE 315-and may provide an indication to UE 315, or may initiate corrective action itself based on the failure, some combination of these, or other actions.

At decision block 330, UE 315 may determine whether a split signaling radio bearer is configured. If UE 315 determines that the split signaling radio bearer is configured, UE 315 may perform the action designated in block 335. Otherwise, if the UE 315 determines that the split signaling radio bearer is not configured, UE 315 may perform the action designated by decision block 340, among other examples.

At block 335, at least one of UE 315, master node 307, or secondary node 309 may perform a master cell group recovery procedure using the split signaling radio bearer. Performing the master cell group recovery procedure may include transmitting: an indication of the master cell group failure, channel measurements associated with the master cell group failure, and/or information relating to the master cell group failure (e.g., a type of failure) . In some examples, the master cell group recovery procedure using the split signaling radio bearer may be less complex than a master cell group recovery procedure that uses a secondary signaling radio bearer.

At decision block 340, UE 315 may determine whether a secondary signaling radio bearer is configured, for example but not limited to, after determining that the split signaling radio bearer is not configured. If the secondary signaling radio bearer is not configured, UE 315 may perform the action designated in block 345. Otherwise, if the secondary signaling radio bearer is configured, UE 315 may perform the action designated by arrow 350.

At block 345, UE 315 may initiate an RRC reestablishment procedure with master node 307, and in some examples, additionally or alternatively, with secondary node 309, based on determining that the split signaling radio bearer and the secondary signaling radio bearer are not configured.

At arrow 350, UE 315 may transmit, and secondary node 309 may receive, failure information for the MCG to secondary node 309 over the secondary cell group via the secondary signaling radio bearer. In some examples, before transmitting the failure information, UE 315 may construct an RRC message (e.g., a ULInformationTransferMRDC message) that may be used to convey information for dual-connectivity operations. In some examples, UE 315 may also cipher the RRC message based on key (s) associated with master node 307. In some examples, the RRC message may be a container message that includes one or more RRC messages, including at least one RRC message (e.g., a MeasurementReport message, FailureInformation message, and/or an MCGFailureInformation message) indicating information relating to measurements associated with the MCG failure and/or a concurrent SCG failure (if applicable) , information relating to a type and/or cause of a concurrent SCG failure (if applicable) , and a type and/or cause of the MCG failure.

In some examples, if the master node 307 and the secondary node 309 use NR technology, the RRC container message may include a MeasurementReport message, a FailureInformation message, and/or an MCGFailureInformation message. In some examples, if the master node 307 uses E-UTRA technology and the secondary node 309 uses NR technology, the RRC container message may include an MCGFailureInformation message. In some examples, the MCGFailureInformation message may be intended for master node 307. In some examples, the RRC container message may be conveyed between UE 315 and secondary node 309 via the secondary signaling radio bearer.

At arrow 355, secondary node 309 may relay an RRC message related to the MCG failure (or an “MCG Failure message” ) , such as an MCGFailureInformation message, to master node 307 via a control interface between master node 307 and secondary node 309 using the secondary signaling radio bearer (e.g., SRB3) . In some examples, relaying the MCG Failure message may include extracting the MCG Failure message from the RRC container message and encapsulating the MCG Failure message in a higher-layer (e.g., Xn or X2) container message (or a “control interface container message” ) . In some examples, the MCG Failure message may be relayed to master node 307 as an octet string.

In some examples, if master node 307 uses a NR technology and secondary node 309 uses an E-UTRA technology (NE-DC) , secondary node 309 may transmit the MCG failure message to master node 307 in an NR UE Report message container via the control interface. In some examples, the NR UE Report message container may convey an MeasurementReport message and/or a FailureInformation message. In some examples, if master node 307 uses an E-UTRA technology and secondary node 309 uses an E-UTRA technology, secondary node 309 may transmit the MCG failure message to master node 307 in an E-UTRA UE Report message container via the control interface. In some examples, the E-UTRA UE Report message container may convey an MCGFailureInformation message.

In some examples, if master node 307 uses a NR or an E-UTRA technology and secondary node 309 uses an E-UTRA technology, secondary node 309 may transmit the MCG failure message to master node 307 using a single UE Report message container via the control interface. In some examples, the UE Report message container may convey a MeasurementReport message, a FailureInformation message, and/or an MCGFailureInformation message.

In some examples, if master node 307 uses an E-UTRA technology and secondary node 309 uses a NR technology (NGEN-DC or EN-DC) , secondary node 309 may transmit the MCG failure message to master node 307 in a UE Report message container via the control interface. In some examples, the UE Report message container may include a MeasurementReport message, a FailureInformation message, and/or an MCGFailureInformation message.

In some examples, if master node 307 uses a NR technology and secondary node 309 uses an E-UTRA technology (NE-DC) , secondary node 309 may transmit the MCG failure message to master node 307 in a UE Report message container via the control interface. In some examples, the UE Report message container may include an MCGFailureInformation message. In some examples, if master node 307 uses a NR technology and secondary node 309 uses an NR technology (NR-DC) , secondary node 309 may transmit the MCG Failure message to master node 307 in a UE Report message container via the control interface. In some examples, the UE Report message container may include a MeasurementReport message, a FailureInformation message, and/or an MCGFailureInformation message.

At block 360, master node 307 may extract the MCG Failure message from the higher-layer container received from secondary node 309. Master node 307 may process then MCG Failure message and use the failure information to determine a network response for managing the MCG failure. In some examples, the network response may be for UE 315 to be handed over from the master node 307 to a target master node to be performed-e.g., based on channel measurements reported by UE 315 for the target master node.

Handing UE 315 over from master node 307 to the target master node may include reconfiguring an RRC connection at UE 315 to be between UE 315 and the target master node. Master node 307 may construct an RRC reconfiguration message based on determining a handover procedure as the network response. In other cases, the network response may be for UE 315 to release an RRC connection to the master node and/or to place the RRC connection in an idle state-e.g., based on channel measurements reported by UE 315 for master node 307 and/or candidate target master nodes. Master node 307 may construct an RRC release message based on determining a release procedure as the network response.

At arrow 365, master node 307 may transmit, and secondary node 309 may receive, the network response via the control interface using the second signaling radio bearer. In some examples, the network response may be transmitted as an octet string ciphered (or encrypted) with a key of the master node 307 (e.g., a unique code assigned to master node 307) .

In some examples, before transmitting the network response, master node 307 may encapsulate the network response in a higher-layer container message. In some examples, if master node 307 uses an E-UTRA technology, master node 307 may transmit the higher-layer container message to secondary node 309 in an MeNB RRC message container message via the control interface. The MeNB RRC message container message may include an RRCReconfiguration message or an RRCRelease message. In some examples, if master node 307 uses a NR technology, master node 307 may transmit the higher-layer container message to secondary node 309 in an MN RRC message container via the control interface. The MN RRC message container message may include an RRCReconfiguration message or an RRCRelease message.

At arrow 370, secondary node 309 may relay, and UE 315 may receive, the network response over the secondary cell group and via the secondary signaling radio bearer. In some examples, relaying the network response may include extracting an RRC message included in a higher-layer container message received from master node 307. After extracting the RRC message, secondary node 309 may encapsulate the RRC message in an RRC container message (e.g., a DLInformationTransferMRDC message) and transmit the RRC container message to UE 315.

In other examples, secondary node 309 may transmit the extracted message without first encapsulating the RRC message. In yet other examples, secondary node 309 may generate a corresponding RRC message (e.g., an RRCReconfiguration message or an RRCRelease message) and transmit the generated RRC message to UE 315. By encapsulating the RRC message in an RRC container message, secondary node 309 may reserve RRC configuration messages originating from secondary node 309 for configuring secondary cell group RRC connections.

At block 375, UE 315 may process the network response (originating from master node 307) and manage an RRC connection configured at UE 315 based on the network response. In some examples, processing the network response includes extracting network response from an RRC container message used by secondary node 309 to relay the network response.

In other cases, processing the network response includes receiving the network response directly. In some examples, UE 315 may perform a handover procedure based on the network response-e.g., based on processing an RRCReconfiguration message. Performing the handover procedure may include transferring an RRC connection with master node 307 to a target master node. In some examples, during the handover procedure, UE 315 establishes a master signaling radio bearer (e.g., SRB1) between UE 315 and the target master node and transmits a message that the RRC reconfiguration is complete (e.g., in an RRCReconfigurationComplete message) to the target master node after performing a RACH procedure with the target master node via the master signaling radio bearer. In other cases, UE 315 may release an RRC connection with master node 307, which may include transitioning the RRC connection to an idle node-e.g., based on processing an RRCRelease message.

FIG. 4 shows a block diagram 400 of a device 405 that supports recovering from a master node link failure 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 recovering from a master node link failure, etc. ) . Information may be passed on to other components of the device 405. The receiver 410 may be included in a transceiver. The receiver 410 may utilize a single antenna or a set of antennas.

The communications manager 415 may receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology, configure a first RRC connection between the UE and the master node and a second RRC connection between the UE and the secondary node based on receiving the configuration, detect a failure of the master cell group after configuring the first RRC connection and the second RRC connection, and initiate a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. The communications manager 415 may be an example of aspects of the communications manager 610 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 DSP, an application-specific integrated circuit (ASIC) , a 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. The transmitter 420 may utilize a single antenna or a set of antennas.

FIG. 5 shows a block diagram 500 of a communications manager 505 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The communications manager 505 may be an example of aspects of a communications manager 415 described herein. The communications manager 505 may include a dual-connectivity manager 510, a cell group manager 515, a master cell group manager 520, a link recovery manager 525, and a security manager 530. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The dual-connectivity manager 510 may receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology. In some examples, the dual-connectivity manager 510 may configure the secondary signaling radio bearer between the UE and the secondary node before the failure of the master cell group is detected based on receiving the configuration. In some examples, the dual-connectivity manager 510 may configure the split signaling radio bearer between the UE, the master node, and the secondary node before the failure of the master cell group is detected based on receiving the configuration. In some examples, the dual-connectivity manager 510 may configure the secondary signaling radio bearer before the failure of the master cell group is detected based on receiving the configuration.

The cell group manager 515 may configure a first RRC connection between the UE and the master node and a second RRC connection between the UE and the secondary node based on receiving the configuration.

The master cell group manager 520 may detect a failure of the master cell group after configuring the first RRC connection and the second RRC connection. In some examples, the master cell group manager 520 may manage, as part of the recovery procedure, the first RRC connection based on the response. In some examples, the master cell group manager 520 may perform a handover procedure between the master node and a target master node based on receiving the RRC reconfiguration message. In some examples, the master cell group manager 520 may configuring a master signaling radio bearer between the UE and the target master node and transmitting, to the target master node via the master signaling radio bearer, a third radio resource control message (e.g., an RRCReconfigurationComplete message) indicating a radio resource control reconfiguration is complete. In some examples, the master cell group manager 520 may release the first RRC connection based on receiving the RRC release message.

The link recovery manager 525 may initiate a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. In some examples, the link recovery manager 525 may determine that the split signaling radio bearer is not configured based on detecting the failure of the master cell group. In some examples, the link recovery manager 525 may transmit, as part of the recovery procedure, an RRC message including information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the secondary signaling radio bearer based on determining that the split signaling radio bearer is not configured.

In some examples, the link recovery manager 525 may receive, from the secondary node over the secondary cell group and as part of the recovery procedure, a second RRC message including a response associated with the master node, where the response is based on the information. In some examples, the link recovery manager 525 may determine that the split signaling radio bearer is configured based on detecting the failure of the master cell group. In some examples, the link recovery manager 525 may transmit, as part of the recovery procedure, an RRC message including information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the split signaling radio bearer based on determining that the split signaling radio bearer is configured. In some examples, the link recovery manager 525 may receive, from the secondary node over the secondary node and as part of the recovery procedure, a response originating from the master node based on the information.

In some examples, the link recovery manager 525 may determine that the split signaling radio bearer and the secondary signaling radio bearer are not configured based on detecting the failure of the master cell group. In some examples, the link recovery manager 525 may perform, as part of the recovery procedure, an RRC connection reestablishment procedure based on the determining. In some examples, a second RRC message includes the information in an MCGFailureInformation message. In some examples, a third RRC configuration message originating from the master node includes the response. In some examples, an RRC reconfiguration message or an RRC release message originating from the master node includes the response. In some examples, the second RRC message includes an RRC reconfiguration message or an RRC release message originating from the secondary node. In some examples, the second RRC includes a DLInformationTransferMRDC message. In some examples, the RRC message includes an ULInformationTransferMRDC message, the RRC message being ciphered based on a key associated with the master node. In some examples, the split signaling radio bearer includes a split signaling radio bearer 1 (SRB1) and the secondary signaling radio bearer includes a signaling radio bearer 3 (SRB3) .

The security manager 530 may cipher the RRC message based on a key associated with the master node.

FIG. 6 shows a diagram of a system 600 including a device 605 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The device 605 may be an example of or include the components of device 405 or a UE 115 as described herein. The device 605 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 610, an I/O controller 615, a transceiver 620, an antenna 625, memory 630, and a processor 640. These components may be in electronic communication via one or more buses (e.g., bus 645) .

The communications manager 610 may be an example of communications manager 415 or communications manager 505 as described in FIGs. 4 and 5.

The I/O controller 615 may manage input and output signals for the device 605. The I/O controller 615 may also manage peripherals not integrated into the device 605. In some examples, the I/O controller 615 may represent a physical connection or port to an external peripheral. In some examples, the I/O controller 615 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 615 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some examples, the I/O controller 615 may be implemented as part of a processor. In some examples, a user may interact with the device 605 via the I/O controller 615 or via hardware components controlled by the I/O controller 615.

The transceiver 620 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described herein. For example, the transceiver 620 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 620 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 examples, the wireless device may include a single antenna 625. However, In some examples the device may have more than one antenna 625, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 630 may include random-access memory (RAM) and read-only memory (ROM) . The memory 630 may store computer-readable, computer-executable code 635 including instructions that, when executed, cause the processor to perform various functions described herein. In some examples, the memory 630 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 640 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 examples, the processor 640 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 640. The processor 640 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 630) to cause the device 605 to perform various functions (e.g., functions or tasks supporting recovering from a master node link failure) .

The code 635 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 635 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some examples, the code 635 may not be directly executable by the processor 640 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 7 shows a block diagram 700 of a device 705 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The device 705 may be an example of aspects of a base station 105, a master node, or a secondary node as described herein. The device 705 may include a receiver 710, a communications manager 715, and a transmitter 720. The device 705 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 710 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 recovering from a master node link failure, etc. ) . Information may be passed on to other components of the device 705. The receiver 710 may be included in a transceiver. The receiver 710 may utilize a single antenna or a set of antennas.

In some examples, when device 705 is configured as a master node, the communications manager 715 may receive a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology, configure a first RRC connection between the UE and the master node based on the configuration, identify a failure of the master cell group after configuring the first RRC connection, and initiate a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

In some examples, when device 705 is configured as a secondary node, the communications manager 715 may also receive a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology, configure a first RRC connection between the UE and the secondary node based on receiving the configuration, receive an indication of a failure of the master cell group after configuring the first RRC connection, and initiate a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.

The communications manager 715, 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 715, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC) , a 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 715, 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 715, 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 715, 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 720 may transmit signals generated by other components of the device 705. In some examples, the transmitter 720 may be collocated with a receiver 710 in a transceiver module. The transmitter 720 may utilize a single antenna or a set of antennas.

FIG. 8 shows a block diagram 800 of a communications manager 805 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The communications manager 805 may be an example of aspects of a communications manager 715 described herein. The communications manager 805 may include a dual-connectivity manager 810, a cell group manager 815, a master cell group manager 820, a link recovery manager 825, a control transfer manager 830, and a security manager 835. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

In some examples, when communications manager 805 is included in a master node, the dual-connectivity manager 810 may receive a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology.

The cell group manager 815 may configure a first RRC connection between the UE and the master node based on the configuration. In some examples, a second RRC connection is configured between the UE and the secondary node based on receiving the configuration.

The master cell group manager 820 may identify a failure of the master cell group after configuring the first RRC connection. In some examples, the master cell group manager 820 may receive an indication of the failure of the master cell group based on receiving an MCGFailureInformation message; or. In some examples, the master cell group manager 820 may determine the failure of the master cell group.

The link recovery manager 825 may initiate a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. In some examples, the link recovery manager 825 may determine, as part of the recovery procedure, an action for managing the first RRC connection configured between the UE and the master node based on the information included in the indication. In some examples, the link recovery manager 825 may transmit, as part of the recovery procedure, a second RRC message including a response to the secondary node via the control interface. In some examples, the link recovery manager 825 may receive the indication of the failure of the master cell group from the secondary node via the split signaling radio bearer, the indication including information associated with the failure of the master cell group. In some examples, an RRC reconfiguration message or an RRC release message includes the response.

The control transfer manager 830 may receive, over a control interface configured between the master node and the secondary node, an RRC message including the indication of the failure of the master cell group from the secondary node, the indication including information associated with the failure of the master cell group. In some examples, encapsulating, as part of the recovery procedure, the second RRC message in a second higher-layer container, where transmitting the second RRC message includes transmitting the second higher-layer container to the secondary node via the control interface. In some examples, the control interface includes one or both of an Xn interface or an X2 interface. In some examples, the higher-layer container includes an RRC transfer message.

The security manager 835 may cipher the response based on a key associated with the master node.

In some examples, when communications manager 805 is included in a master node, the communications manager 805 may include a dual-connectivity manager 8, a cell group manager 815, a master cell group manager 20, a link recovery manager 825, and a control transfer manager 830. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The dual-connectivity manager 810 may receive a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology. In some examples, configuring the secondary signaling radio bearer before receiving the indication of the failure of the master cell group based on receiving the configuration, where the receiving includes receiving, over the secondary cell group and via the secondary signaling radio bearer, a radio resource control message comprising the indication of the failure of the master cell group from the UE, the indication comprising information associated with the failure of the master cell group. In some examples, configuring the split signaling radio bearer before receiving the indication of the failure of the master cell group based on receiving the configuration, where the receiving includes receiving, from the UE, the indication of the failure of the master cell group over the secondary cell group and via the split signaling radio bearer, the indication comprising information associated with the failure of the master cell group; and relaying the indication of the failure of the master cell group to the master node via the split signaling radio bearer.

The cell group manager 815 may configure a first RRC connection between the UE and the secondary node based on receiving the configuration.

The master cell group manager 820 may receive an indication of a failure of the master cell group after configuring the first RRC connection.

The link recovery manager 825 may initiate a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. In some examples, generating a third RRC message based on the information for managing the second RRC connection, where generating the third RRC message includes generating an RRC reconfiguration message or an RRC release message. In some examples, the link recovery manager 825 may transmit the third RRC message to the UE over the secondary cell group via the secondary signaling radio bearer. In some examples, the third RRC message includes a DLInformationTransferMRDC message.

The control transfer manager 830 may encapsulate, as part of the recovery procedure, the information associated with the failure of the master cell group in a higher-layer container. In some examples, the control transfer manager 830 may transmit, as part of the recovery procedure, the higher-layer container to the master node via a control interface between the secondary node and the master node. In some examples, the control transfer manager 830 may receive, from the master node, a response that is encapsulated in a second higher-layer container based on transmitting the higher-layer container, where the response includes a second RRC message including information for managing a second RRC connection configured between the UE and the master node. In some examples, the control transfer manager 830 may encapsulate the second RRC message in a third RRC message. In some examples, the control transfer manager 830 may transmit the third RRC message to the UE over the secondary cell group and via the secondary signaling radio bearer. In some examples, the higher-layer container includes an RRC transfer message, and where the control interface includes one or both of an Xn interface or an X2 interface.

FIG. 9 shows a diagram of a system 900 including a device 905 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The device 905 may be an example of or include the components of device 705 or a base station 105 as described herein. The device 905 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 910, a network communications manager 915, a transceiver 920, an antenna 925, memory 930, a processor 940, and an inter-station communications manager 945. These components may be in electronic communication via one or more buses (e.g., bus 950) .

The communications manager 910 be an example of a communications manager 715 or a communications manager 805 as described with reference to FIGs. 7 and 8.

The network communications manager 915 may manage communications with the core network (e.g., via one or more wired backhaul links) . For example, the network communications manager 915 may manage the transfer of data communications for client devices, such as one or more UEs 115.

The transceiver 920 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described herein. For example, the transceiver 920 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 920 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 examples, the wireless device may include a single antenna 925. However, In some examples the device may have more than one antenna 925, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 930 may include RAM, ROM, or a combination thereof. The memory 930 may store computer-readable code 935 including instructions that, when executed by a processor (e.g., the processor 940) cause the device to perform various functions described herein. In some examples, the memory 930 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 940 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 examples, the processor 940 may be configured to operate a memory array using a memory controller. In some examples, a memory controller may be integrated into processor 940. The processor 940 may be configured to execute computer- readable instructions stored in a memory (e.g., the memory 930) to cause the device 905 to perform various functions (e.g., functions or tasks supporting recovering from a master node link failure) .

The inter-station communications manager 945 may manage communications with other base station 105 and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 945 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager 945 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

The code 935 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 935 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some examples, the code 935 may not be directly executable by the processor 940 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 10 shows a flowchart illustrating a method 1000 that supports recovering from a master node link failure 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 6. 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 receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second 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 dual-connectivity manager as described with reference to FIGs. 4 through 6.

At 1010, the UE may configure a first RRC connection between the UE and the master node and a second RRC connection between the UE and the secondary node based on receiving the configuration. 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 cell group manager as described with reference to FIGs. 4 through 6.

At 1015, the UE may detect a failure of the master cell group after configuring the first RRC connection and the second RRC connection. 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 master cell group manager as described with reference to FIGs. 4 through 6.

At 1020, the UE may initiate a recovery procedure for the master cell group based on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. 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 link recovery manager as described with reference to FIGs. 4 through 6.

FIG. 11 shows a flowchart illustrating a method 1100 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The operations of method 1100 may be implemented by a secondary node or its components as described herein. For example, the operations of method 1100 may be performed by a communications manager as described with reference to FIGs. 7 through 9. In some examples, a secondary node may execute a set of instructions to control the functional elements of the secondary node to perform the functions described herein. Additionally, or alternatively, a secondary node may perform aspects of the functions described herein using special-purpose hardware.

At 1105, the secondary node may receive a configuration to communicate over a secondary cell group with a UE that is also configured to communicate over a master cell group with a master node associated with a first radio access technology. The operations of 1105 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be performed by a dual-connectivity manager as described with reference to FIGs. 7 through 9.

At 1110, the secondary node may configure a first RRC connection between the UE and the secondary node based on receiving the configuration. The operations of 1110 may be performed according to the methods described herein. In some examples, aspects of the operations of 1110 may be performed by a cell group manager as described with reference to FIGs. 7 through 9.

At 1115, the secondary node may receive an indication of a failure of the master cell group after configuring the first RRC connection. The operations of 1115 may be performed according to the methods described herein. In some examples, aspects of the operations of 1115 may be performed by a master cell group manager as described with reference to FIGs. 7 through 9.

At 1120, the secondary node may initiate a recovery procedure for the master cell group based on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. The operations of 1120 may be performed according to the methods described herein. In some examples, aspects of the operations of 1120 may be performed by a link recovery manager as described with reference to FIGs7 through 9.

FIG. 12 shows a flowchart illustrating a method 1200 that supports recovering from a master node link failure in accordance with aspects of the present disclosure. The operations of method 1200 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1200 may be performed by a communications manager as described with reference to FIGs. 7 through 9. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described herein. Additionally, or alternatively, a base station may perform aspects of the functions described herein using special-purpose hardware.

At 1205, the base station may receive a configuration to communicate over a master cell group with a UE that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology. The operations of 1205 may be performed according to the methods described herein. In some examples, aspects of the operations of 1205 may be performed by a dual-connectivity manager as described with reference to FIGs. 7 through 9.

At 1210, the base station may configure a first RRC connection between the UE and the master node based on the configuration. The operations of 1210 may be performed according to the methods described herein. In some examples, aspects of the operations of 1210 may be performed by a cell group manager as described with reference to FIGs. 7 through 9.

At 1215, the base station may identify a failure of the master cell group after configuring the first RRC connection. The operations of 1215 may be performed according to the methods described herein. In some examples, aspects of the operations of 1215 may be performed by a master cell group manager as described with reference to FIGs. 7 through 9.

At 1220, the base station may initiate a recovery procedure for the master cell group based on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, where the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node. The operations of 1220 may be performed according to the methods described herein. In some examples, aspects of the operations of 1220 may be performed by a link recovery manager as described with reference to FIGs. 7 through 9.

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.

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, example, 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 examples, known structures and devices are shown in block diagram form 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 communications at a user equipment (UE) , comprising:

receiving a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology;

configuring a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

detecting a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection; and

initiating a recovery procedure for the master cell group based at least in part on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The method of claim 1, further comprising:

configuring the secondary signaling radio bearer between the UE and the secondary node before the failure of the master cell group is detected based at least in part on receiving the configuration;

determining that the split signaling radio bearer is not configured based at least in part on detecting the failure of the master cell group; and

transmitting, as part of the recovery procedure, a radio resource control message comprising information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the secondary signaling radio bearer based at least in part on determining that the split signaling radio bearer is not configured.
The method of claim 2, wherein the radio resource control message comprises a ULInformationTransferMRDC message, the method further comprising:

ciphering the radio resource control message based at least in part on a key associated with the master node.
The method of claim 2, wherein a second radio resource control message comprises the information, the second radio resource control message comprising an MCGFailureInformation message.
The method of claim 2, further comprising:

receiving, from the secondary node over the secondary cell group and as part of the recovery procedure, a second radio resource control message comprising a response associated with the master node, wherein the response is based at least in part on the information; and

managing, as part of the recovery procedure, the first radio resource control connection based at least in part on the response.
The method of claim 5, wherein a third radio resource control configuration message originating from the master node comprises the response.
The method of claim 5, wherein a radio resource control reconfiguration message or a radio resource control release message originating from the master node comprises the response.
The method of claim 5, wherein the second radio resource control message comprises a radio resource control reconfiguration message or a radio resource control release message originating from the secondary node.
The method of claim 5, wherein the second radio resource control message comprises a DLInformationTransferMRDC message.
The method of claim 7, wherein managing the first radio resource control connection comprises:

performing a handover procedure between the master node and a target master node based at least in part on receiving the radio resource control reconfiguration message.
The method of claim 10, further comprising:

configuring a master signaling radio bearer between the UE and the target master node; and

transmitting, to the target master node via the master signaling radio bearer, a third radio resource control message indicating a radio resource control reconfiguration is complete, wherein the third radio resource control message comprises an RRCReconfigurationComplete message.
The method of claim 7, wherein managing the first radio resource control connection comprises:

releasing the first radio resource control connection based at least in part on receiving the radio resource control release message.
The method of claim 1, further comprising:

configuring the split signaling radio bearer between the UE, the master node, and the secondary node before the failure of the master cell group is detected based at least in part on receiving the configuration;

determining that the split signaling radio bearer is configured based at least in part on detecting the failure of the master cell group; and

transmitting, as part of the recovery procedure, a radio resource control message comprising information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the split signaling radio bearer based at least in part on determining that the split signaling radio bearer is configured.
The method of claim 13, wherein the radio resource control message comprises an ULInformationTransferMRDC message, the radio resource control message being ciphered based at least in part on a key associated with the master node.
The method of claim 13, further comprising:

receiving, from the secondary node over the secondary node and as part of the recovery procedure, a response originating from the master node based at least in part on the information; and

managing, as part of the recovery procedure, the first radio resource control connection based at least in part on the response.
The method of claim 13, further comprising:

configuring the secondary signaling radio bearer before the failure of the master cell group is detected based at least in part on receiving the configuration.
The method of claim 1, wherein initiating the recovery procedure comprises:

determining that the split signaling radio bearer and the secondary signaling radio bearer are not configured based at least in part on detecting the failure of the master cell group; and

performing, as part of the recovery procedure, a radio resource control connection reestablishment procedure based at least in part on the determining.
The method of claim 1, wherein the split signaling radio bearer comprises a split signaling radio bearer 1 (SRB1) and the secondary signaling radio bearer comprises a signaling radio bearer 3 (SRB3) .
A method for wireless communications at a secondary node associated with a second radio access technology, comprising:

receiving a configuration to communicate over a secondary cell group with a user equipment (UE) that is also configured to communicate over a master cell group with a master node associated with a first radio access technology;

configuring a first radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

receiving an indication of a failure of the master cell group after configuring the first radio resource control connection; and

initiating a recovery procedure for the master cell group based at least in part on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The method of claim 19, further comprising:

configuring the secondary signaling radio bearer before receiving the indication of the failure of the master cell group based at least in part on receiving the configuration, wherein the receiving comprises:

receiving, over the secondary cell group and via the secondary signaling radio bearer, a radio resource control message comprising the indication of the failure of the master cell group from the UE, the indication comprising information associated with the failure of the master cell group.
The method of claim 20, further comprising:

encapsulating, as part of the recovery procedure, the information associated with the failure of the master cell group in a higher-layer container; and

transmitting, as part of the recovery procedure, the higher-layer container to the master node via a control interface between the secondary node and the master node.
The method of claim 21, wherein the higher-layer container comprises a radio resource control transfer message, and wherein the control interface comprises one or both of an Xn interface or an X2 interface.
The method of claim 21, further comprising:

receiving, from the master node, a response that is encapsulated in a second higher-layer container based at least in part on transmitting the higher-layer container, wherein the response includes a second radio resource control message comprising information for managing a second radio resource control connection configured between the UE and the master node.
The method of claim 23, wherein the second higher-layer container comprises a radio resource control transfer message.
The method of claim 23, further comprising:

encapsulating the second radio resource control message in a third radio resource control message; and

transmitting the third radio resource control message to the UE over the secondary cell group and via the secondary signaling radio bearer.
The method of claim 23, further comprising:

generating a third radio resource control message based at least in part on the information for managing the second radio resource control connection, wherein generating the third radio resource control message comprises generating a radio resource control reconfiguration message or a radio resource control release message; and

transmitting the third radio resource control message to the UE over the secondary cell group via the secondary signaling radio bearer.
The method of claim 26, wherein the third radio resource control message comprises a DLInformationTransferMRDC message.
The method of claim 19, further comprising:

configuring the split signaling radio bearer before receiving the indication of the failure of the master cell group based at least in part on receiving the configuration, wherein the receiving comprises:

receiving, from the UE, the indication of the failure of the master cell group over the secondary cell group and via the split signaling radio bearer, the indication comprising information associated with the failure of the master cell group; and

relaying the indication of the failure of the master cell group to the master node via the split signaling radio bearer.
A method for wireless communications at a master node associated with a first radio access technology, comprising:

receiving a configuration to communicate over a master cell group with a user equipment (UE) that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology;

configuring a first radio resource control connection between the UE and the master node based at least in part on the configuration;

identifying a failure of the master cell group after configuring the first radio resource control connection; and

initiating a recovery procedure for the master cell group based at least in part on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The method of claim 29, wherein the identifying comprises:

receiving an indication of the failure of the master cell group based at least in part on receiving an MCGFailureInformation message; or

determining the failure of the master cell group.
The method of claim 30, wherein the secondary signaling radio bearer is configured before the failure of the master cell group is identified, and wherein the receiving comprises:

receiving, over a control interface configured between the master node and the secondary node, a radio resource control message comprising the indication of the failure of the master cell group from the secondary node, the indication comprising information associated with the failure of the master cell group.
The method of claim 31, wherein the control interface comprises one or both of an Xn interface or an X2 interface, and wherein the radio resource control message comprises a radio resource control transfer message.
The method of claim 31, wherein the radio resource control message is received in a higher-layer container, the method further comprising:

determining, as part of the recovery procedure, an action for managing the first radio resource control connection configured between the UE and the master node based at least in part on the information included in the indication; and

transmitting, as part of the recovery procedure, a second radio resource control message comprising a response to the secondary node via the control interface.
The method of claim 33, wherein the higher-layer container comprises a radio resource control transfer message.
The method of claim 33, wherein a radio resource control reconfiguration message or a radio resource control release message comprises the response.
The method of claim 33, further comprising:

encapsulating, as part of the recovery procedure, the second radio resource control message in a second higher-layer container, wherein transmitting the second radio resource control message comprises:

transmitting the second higher-layer container to the secondary node via the control interface.
The method of claim 33, further comprising:

ciphering the response based on a key associated with the master node.
The method of claim 30, wherein the split signaling radio bearer is configured before the failure of the master cell group is identified, and wherein the receiving comprises:

receiving the indication of the failure of the master cell group from the secondary node via the split signaling radio bearer, the indication comprising information associated with the failure of the master cell group.
The method of claim 29, wherein a second radio resource control connection is configured between the UE and the secondary node based at least in part on receiving the configuration.
An apparatus for wireless communications 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:

receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology;

configure a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

detect a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The apparatus of claim 40, wherein the instructions are further executable by the processor to cause the apparatus to:

configure the secondary signaling radio bearer between the UE and the secondary node before the failure of the master cell group is detected based at least in part on receiving the configuration;

determine that the split signaling radio bearer is not configured based at least in part on detecting the failure of the master cell group; and

transmit, as part of the recovery procedure, a radio resource control message comprising information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the secondary signaling radio bearer based at least in part on determining that the split signaling radio bearer is not configured.
The apparatus of claim 40, wherein the instructions are further executable by the processor to cause the apparatus to:

configure the split signaling radio bearer between the UE, the master node, and the secondary node before the failure of the master cell group is detected based at least in part on receiving the configuration;

determine that the split signaling radio bearer is configured based at least in part on detecting the failure of the master cell group; and

transmit, as part of the recovery procedure, a radio resource control message comprising information associated with the failure of the master cell group to the secondary node over the secondary cell group and via the split signaling radio bearer based at least in part on determining that the split signaling radio bearer is configured.
An apparatus for wireless communications at a secondary node associated with a second radio access technology, comprising:

a processor,

memory coupled with the processor; and

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

receive a configuration to communicate over a secondary cell group with a user equipment (UE) that is also configured to communicate over a master cell group with a master node associated with a first radio access technology;

configure a first radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

receive an indication of a failure of the master cell group after configuring the first radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The apparatus of claim 43, wherein the instructions are further executable by the processor to cause the apparatus to:

configure the secondary signaling radio bearer before receiving the indication of the failure of the master cell group based at least in part on receiving the configuration, wherein the receiving comprises.
An apparatus for wireless communications at a master node associated with a first radio access technology, comprising:

a processor,

memory coupled with the processor; and

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

receive a configuration to communicate over a master cell group with a user equipment (UE) that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology;

configure a first radio resource control connection between the UE and the master node based at least in part on the configuration;

identify a failure of the master cell group after configuring the first radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
The apparatus of claim 45, wherein the identifying comprises:

receive an indication of the failure of the master cell group based at least in part on receiving an MCGFailureInformation message; or; and

determine the failure of the master cell group.
An apparatus for wireless communications at a user equipment (UE) , comprising:

means for receiving a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology;

means for configuring a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

means for detecting a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection; and

means for initiating a recovery procedure for the master cell group based at least in part on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
An apparatus for wireless communications at a secondary node associated with a second radio access technology, comprising:

means for receiving a configuration to communicate over a secondary cell group with a user equipment (UE) that is also configured to communicate over a master cell group with a master node associated with a first radio access technology;

means for configuring a first radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

means for receiving an indication of a failure of the master cell group after configuring the first radio resource control connection; and

means for initiating a recovery procedure for the master cell group based at least in part on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
An apparatus for wireless communications at a master node associated with a first radio access technology, comprising:

means for receiving a configuration to communicate over a master cell group with a user equipment (UE) that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology;

means for configuring a first radio resource control connection between the UE and the master node based at least in part on the configuration;

means for identifying a failure of the master cell group after configuring the first radio resource control connection; and

means for initiating a recovery procedure for the master cell group based at least in part on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
A non-transitory computer-readable medium storing code for wireless communications at a user equipment (UE) , the code comprising instructions executable by a processor to:

receive a configuration to communicate over a master cell group with a master node associated with a first radio access technology and over a secondary cell group with a secondary node associated with a second radio access technology;

configure a first radio resource control connection between the UE and the master node and a second radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

detect a failure of the master cell group after configuring the first radio resource control connection and the second radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on detecting the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
A non-transitory computer-readable medium storing code for wireless communications at a secondary node associated with a second radio access technology, the code comprising instructions executable by a processor to:

receive a configuration to communicate over a secondary cell group with a user equipment (UE) that is also configured to communicate over a master cell group with a master node associated with a first radio access technology;

configure a first radio resource control connection between the UE and the secondary node based at least in part on receiving the configuration;

receive an indication of a failure of the master cell group after configuring the first radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on receiving the indication of the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.
A non-transitory computer-readable medium storing code for wireless communications at a master node associated with a first radio access technology, the code comprising instructions executable by a processor to:

receive a configuration to communicate over a master cell group with a user equipment (UE) that is also configured to communicate over a secondary cell group with a secondary node associated with a second radio access technology;

configure a first radio resource control connection between the UE and the master node based at least in part on the configuration;

identify a failure of the master cell group after configuring the first radio resource control connection; and

initiate a recovery procedure for the master cell group based at least in part on identifying the failure of the master cell group and whether one or more of a split signaling radio bearer or a secondary signaling radio bearer are configured for the UE, wherein the split signaling radio bearer is configurable between the UE, the master node, and the secondary node and the secondary signaling radio bearer is configurable between the UE and the secondary node.