WO2021056512A1

WO2021056512A1 - Recovery from cell failure in carrier aggregation

Info

Publication number: WO2021056512A1
Application number: PCT/CN2019/108883
Authority: WO
Inventors: Punyaslok PURKAYASTHA; Gavin Bernard Horn; Peng Cheng
Original assignee: Qualcomm Incorporated
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2021-04-01

Abstract

Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for a user equipment (UE) operating in carrier aggregation potentially performing a fast recovery procedure in the even of a cell failure, based on messages exchanged via another serving cell. For example, upon detecting a degradation of communication quality of the first carrier on a first serving cell, such as a radio link failure (RLF)., the UE may determine whether one or more other serving cells are suitable for sending a message to a base station that indicates the degradation of the serving cell, and if so, send such a message in a suitable serving cell. The UE may receive from the base station a responsive message, such as an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.

Description

RECOVERY FROM CELL FAILURE IN CARRIER AGGREGATION

FIELD OF TECHNOLOGY

The following relates generally to wireless communications and more specifically to recovery from cell failure in carrier aggregation.

BACKGROUND

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

A base station and a UE may communicate via one or more carriers of one or more cells. In some cases, a link quality of a first cell may degrade, and a base station may send an indication to the UE to perform a handover procedure (e.g., to another cell, or to another base station, etc. ) . However, in some examples, a communication link on the primary cell may degrade, and a UE may not receive an indication from the base station to perform a handover procedure.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support recovery from cell failure in carrier aggregation. Generally, the described techniques provide for detecting a degradation of communication quality of the a first carrier on a first cell, determining whether a first parameter (e.g., signal strength) for a second carrier of a second cell satisfies a first threshold, sending a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell (e.g., indicating the degradation, radio link failure (RLF) , or the like) , and receiving from the base station, responsive to the first message, a second message that includes an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.

A method of wireless communications is described. The method may include detecting, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier, determining, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold, sending to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell, and receiving from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform a RRC reconfiguration procedure or an RRC release procedure.

An apparatus for wireless communications 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 detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier, determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold, send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell, and receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform a RRC reconfiguration procedure or an RRC release procedure.

Another apparatus for wireless communications is described. The apparatus may include means for detecting, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier, determining, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold, sending to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell, and receiving from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform a RRC reconfiguration procedure or an RRC release procedure.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier, determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold, send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell, and receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform a RRC reconfiguration procedure or an RRC release procedure.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for communicating with the base station via the second carrier of the second cell, and performing one or more measurements on the first carrier of the first cell and the second carrier of the second cell, where detecting the degradation of the first carrier may be based on the one or more measurements.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, detecting a degradation of the first carrier further may include operations, features, means, or instructions for detecting, based on the one or more measurements, radio link failure (RLF) of the carrier.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, detecting a degradation of the first carrier further may include operations, features, means, or instructions for determining, based on the one or more measurements, that a second parameter for the first carrier of the first cell may be below a second threshold.

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 base station, an indication of the second threshold, where determining that the second parameter for the first carrier of the first cell may be below the second threshold may be based on receiving the indication of the second threshold.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the one or more measurements include one or more of a reference signal received power (RSRP) and a reference signal received quality (RSRQ) .

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for including the performed one or more measurements in the first message, where the second message may be based on the performed one or more measurements.

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 base station, an indication of the first threshold, where determining whether the first parameter satisfies the first threshold may be based on the indication of the first threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the degradation, whether the first parameter for the second carrier satisfies the first threshold for at least a threshold amount of time, where sending the first message via the second carrier may be based on determining that the first parameter for the second carrier satisfies the first threshold for at least the threshold amount of time.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the base station, an indication of the threshold amount of time.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the detecting, that a respective first parameter for one or more of a set of additional carriers corresponding to a set of cells, where a set of respective parameters corresponds to the set of carriers satisfies the first threshold, and selecting the second carrier of the second cell from the one or more additional carriers.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the first parameter for the second carrier may be greater than each of the respective first parameters for the one or more additional carriers, where selecting the second carrier may be based on the first parameter for the second carrier being greater than each of the respective first parameters for the one or more additional carriers.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the degradation, that a configuration condition for the second cell may be satisfied, where sending the first message may be based on determining that the configuration condition may be satisfied.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration condition may include operations, features, means, or instructions for receiving, from the base station, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and HARQ signaling.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration condition may include operations, features, means, or instructions for receiving, from the base station, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration condition may include operations, features, means, or instructions for receiving, from the base station, a configuration message instructing the UE to send the first message via a first bearer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration condition may include operations, features, means, or instructions for receiving, from the base station, a configuration message indicating the first carrier of the first cell and the second carrier of the second cell may be optional carriers for transmitting the first message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing, based on receiving the second message, the RRC reconfiguration procedure.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the RRC reconfiguration procedure may include operations, features, means, or instructions for selecting a third carrier of a third cell, performing a handover procedure between the first carrier of the first cell and the third carrier of the third cell, and communicating with the base station via the third carrier of the third cell.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second cell and the third cell may be the same.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing, based on receiving the second message, the RRC release procedure, and entering an idle mode or an inactive mode based on performing the RRC release procedure.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for initiating, upon transmitting the first message, a timer, monitoring for the second message while the timer may be active, and receiving the second message prior to an expiration of the timer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the UE may be configured to perform an RRC reestablishment procedure if the second message may be not received before the expiration of the timer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first cell may be a primary cell and the second cell may be a secondary cell, the first cell may be a primary cell in a master cell group and the second cell may be a primary secondary cell in a secondary cell group; or, and the first cell may be the primary secondary cell in the secondary cell group and the second cell may be the primary cell in the master cell group.

A method of wireless communications is described. The method may include configuring a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell, receiving, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell, determining, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure, and transmitting, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

An apparatus for wireless communications 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 configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell, receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell, determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure, and transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

Another apparatus for wireless communications is described. The apparatus may include means for configuring a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell, receiving, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell, determining, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure, and transmitting, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell, receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell, determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure, and transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first message includes one or more measurements corresponding to the first carrier of the first cell and the second carrier of the second cell, where the determining may be based on the one or more measurements.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, an indication of a first threshold corresponding to a first parameter for a second carrier of a second cell, where receiving the first message may be based on the first threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, an indication of a threshold amount of time, where receiving the first message may be based on the first parameter for the second carrier of the second cell, the first threshold, and the threshold amount of time.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, an indication of a second threshold corresponding to the first parameter for the first carrier of the first cell, where receiving the first message may be based on the second threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and HARQ signaling.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, a configuration message instructing the UE to send the first message via a first bearer.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, a configuration message indicating that the first carrier of the first cell and the second carrier of the second cell may be optional carriers for transmitting the first message.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communications that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIGs. 4 and 5 show block diagrams of devices that support recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 6 shows a block diagram of a communications manager that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 7 shows a diagram of a system including a device that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIGs. 8 and 9 show block diagrams of devices that support recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 10 shows a block diagram of a communications manager that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIG. 11 shows a diagram of a system including a device that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

FIGs. 12 through 15 show flowcharts illustrating methods that support recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some examples, a base station may communicate with one or more user equipments (UEs) in a carrier aggregation mode. In such cases, the base station and one or more UEs may communicate via one or more carriers of multiple serving cells (e.g., a primary cell (PCell) and one or more secondary cells (SCells) . Where reference is made to communication via a cell (e.g., in a cell, using a cell, over a cell, on a cell, or the like) , it is to be understood that such communication is via a carrier that is supported (provided) by the cell.

Where a UE is in a carrier aggregation mode and a dual connectivity mode, the configured set of serving cells may include two subsets: a master cell group (MCG) and a secondary cell group (SCG) . The MCG may be provided by a first base station, which may be referred to as a master base station, and the SCG may be provided by a second base station, which may be referred to as a secondary base station. One of the cells in the SCG is the primary secondary cell (PSCell) .

Thus, a UE in carrier aggregation will be configured with a PCell and one or more SCells, and possibly a PSCell if also in dual connectivity. In some examples, a link quality on one cell (e.g., a cell on which the UE is communicating with a base station) may degrade (e.g., may fall below a threshold quality, or may experience radio link failure (RLF) ) . Generally, a first cell (e.g., a PCell) may be more reliable than a secondary cell. However, in some examples (e.g., due to UE movement, spatial path blocking, or the like) , a second cell (e.g., an SCell, a PSCell, or the like) may continue to be viable even after degradation of the first cell.

In some cases, a link quality of a first cell may degrade, and a base station may send an indication to the UE to perform a handover procedure (e.g., to another cell, or to another base station, etc. ) . However, in some examples, a communication link on the primary cell may degrade, and a UE may not receive (for a period of time) an indication from the base station to perform a handover procedure. In some examples, if the primary link fails, it may be inefficient to simply initiate RRC establishment procedures when the secondary link remains viable.

In some examples, when a radio link quality of a first cell degrades, the UE may determine whether to perform a fast re-establishment procedure. The UE may detect carrier degradation on a first carrier on the first cell, and may determine whether a first parameter for a second carrier of a second cell satisfies a first threshold. For instance, the UE may determine whether a signal strength on the second cell exceeds a previously configured signal strength threshold. If the second carrier of the second cell has a signal strength that satisfies the threshold, then the UE may send a first message on the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell (e.g., indicating an RLF of the first cell, or that signal strength on the first cell has fallen below a threshold) . In some cases, the UE may determine that multiple other cells correspond to a first parameter that satisfies the first threshold. In such cases, the UE may select one of the set of cells (e.g., may select the cell with the strongest signal level) , and may send the first message on the selected cell. In some examples, the UE may determine whether one or more preconditions are met prior to sending the first message.

The base station may determine a response to the first message. In some cases, the UE may include a report in the first message, indicating available measurements of one or more of the set of cells, additional frequencies, or the like. In such cases, the Base station may consider the report in determining which, if any, of the set of additional cells may be configurable to take the place of the first cell for subsequent communications. The base station, upon consideration of the first message, may send an indication to the UE to perform an RRC reconfiguration procedure or an RRC release procedure. For instance, if none of the set of additional cells has sufficiently high signal quality (e.g., the first parameter corresponding to the additional cells satisfies the first threshold) then the base station may send, in the second message, an indication to perform an RRC release procedure. In such cases, the UE may perform the RRC release procedure, and may enter an idle mode or an inactive mode. Alternatively, if the base station identifies a second carrier of a second cell that corresponds to a first parameter that satisfies the first threshold (e.g., the second cell on which the first message was transmitted, a third cell reported on in the first message, another set of frequency resources, a carrier corresponding to another base station, or the like) , then the base station may send, in the second message, an indication to perform the RRC configuration procedure for subsequent communication over the identified other carrier of the other cell. In such examples, the UE may perform a handover procedure, and may communicate subsequently via the indicated carrier on the newly selected cell.

Particular aspects of the subject matter described herein may be implemented to realize one or more advantages. The described techniques may support improvements in system efficiency, decreased system latency, improved signal quality, and improved user experience.

Aspects of the disclosure are initially described in the context of wireless communications systems and process flows. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to recovery from cell failure in carrier aggregation.

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

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

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

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

One or more of the base stations 105 described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or other suitable terminology.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

In some systems, the D2D communication link 135 may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115) . In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or with both.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

In some examples, a UE 115 may detect a degradation of communication quality of the a first carrier on a first cell, determine whether a first parameter (e.g., signal strength) for a second carrier of a second cell satisfies a first threshold, send a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell (e.g., indicating the degradation, radio link failure (RLF) , or the like) , and receive from the base station, responsive to the first message, a second message that includes an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure. Advantages of the described techniques may include improved system efficiency, decreased system latency, improved signal quality, and improved user experience.

In some examples, the UE 115 may perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell, and detecting the degradation of the first carrier is based at least in part on the one or more measurements. Advantages of performing the one or more measurements may include improved system efficiency, decreased system latency, improved signal quality, and improved user experience.

In some examples, the UE 115 may receiving, from the base station, an indication of the first threshold, the second threshold, or both. Advantages of receiving the indications of the first threshold and the second threshold may include improved system efficiency, decreased system latency, improved signal quality, and improved user experience.

FIG. 2 illustrates an example of a wireless communications system 200 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. In some examples, wireless communications system 200 may implement aspects of wireless communication system 100.

In some examples, a base station 105-a may communicate with one or more UEs 115 (e.g., UE 115-a) . Base station 105-a and UE 115-a may communicate in a carrier aggregation (CA) mode. In such examples, base station 105-a and UE 115-a may communicate via two or more carriers of multiple serving cells 205. In some examples, base station 105-a may configure two or more serving cells 205 (e.g., a primary cell (PCell) and one or more secondary cells (SCells) ) . For instance, serving cell 205-a may be an example of a Pcell, and serving cell 205-b and serving cell 205-c may be examples of SCells.

In some examples, UE 115-a may determine a link quality (e.g., signal strength) for one or more of the serving cells 205. For instance, base station 105-a may transmit one or more signals (e.g., reference signals) via one or more carriers of primary serving cell 205-a, and secondary serving cell 205-b and secondary serving cell 205-c. UE 115-a may receive the one or more signals, and may perform one or more measurements to determine link quality on the serving cells 205. For instance, UE 115-a may determine a respective reference signal received power (RSRP) , a reference signal received quality (RSRQ) , or the like, for each serving cell 205.

Base station 105-a and UE 115-a may communicate via a first serving cell (e.g., a PCell, such as serving cell 205-a) , and the link quality of serving cell 205-a may degrade (e.g., due to obstacles, user position change, interference, or the like) . UE 115-a may determine that a carrier or cell degradation has occurred by determining (e.g., by performing one or more measurements related to radio link monitoring (RLM) that serving cell 205-a has experienced RLF. In some examples, UE 115-a may determine that carrier or serving cell degradation has occurred by determining whether a parameter corresponding to serving cell 205-a satisfies a threshold (e.g., a threshold provided to UE 115-a by base station 105-a via, for instance, RRC signaling) . The parameter may represent a signal strength level, which may be based on one or more measurements (e.g., RSRP, RSRQ, or the like) . Thus, if a signal strength of serving cell 205-a is above or equal to a threshold signal strength value (which may be a fixed offset above a RLF threshold value) , then UE 115-a may continue to communicate via serving cell 205-a. However, if the signal strength of serving cell 205-a is not greater than or equal to the threshold signal strength value, then UE 115-a may determine to initiate a fast recovery procedure.

Upon determining that signal strength on serving cell 205-a has degraded, UE 115-a may determine whether to use a second serving cell 205 to send a first message indicating the status of serving cell 205-a to base station 105-a. In some cases, using another serving cell 205 (e.g., an SCell) may not be any more reliable than serving cell 205-a (e.g., a PCell) . If UE 115-a selects an unreliable serving cell 205 to indicate link degradation on serving cell 205-a, then UE 115-a may transmit multiple retransmissions over the unreliable serving cell 205. This may result in unnecessary delays in a recovery process, system congestion, increased latency, and decreased user experience. To increase the likelihood of a successful fast recovery process, UE 115-a may determine whether a parameter (e.g., signal strength) of a second serving cell (e.g., serving cell 205-b) satisfies a threshold (e.g., a threshold signal strength value) before transmitting a first message indicating the status of serving cell 205-a. The threshold signal strength value may be a fixed offset above a RLF threshold value to ensure that small changes to the serving cell 205-b to not cause the status of serving cell 205-b to experience RLF while attempting to transmit the first message, or shortly after recovery, for example. If the parameter of serving cell 205-b satisfies the threshold, then UE 115-a may transmit the first message to base station 105-a over serving cell 205-b.

In some examples, UE 115-a may determine whether the parameter (e.g., signal strength) of service cell 205-b satisfies the threshold for a period of time (e.g., a set period of time) . That is, instead of determining a signal strength on a particular serving cell 205 (e.g., serving cell 205-b) instantaneously or for an amount of time that may be too short to determine an accurate signal strength, UE 115-a may evaluate (e.g., may perform one or more measurements) a signal strength on serving cell 205-b for at least a threshold amount of time to determine a more accurate signal strength. In some examples, base station 105-b may indicate, to UE 115-a, the threshold amount of time during which the signal strength of serving cell 205-b is to remain greater than or equal to the threshold if the UE 115-a is to perform a fast recovery procedure. For instance, base station 105-b may configure the threshold amount of time via higher layer signaling. In such examples, base station 105-b may transmit an RRC message including an RRC information element (IE) indicating the configured threshold amount of time (e.g., RRC IE: timeToTrigger) . UE 115-a may receive the RRC message, and may perform measurements (e.g., RSRP, RSRQ, etc. ) for at least the threshold amount of time indicated in the RRC message. If the signal strength of serving cell 205-b is greater than or equal to the threshold for the configured duration, then UE 115-a may initiate a fast recovery procedure (e.g., may send the first message described herein) .

In some examples, base station 105-a may configure UE 115-a with the threshold (e.g., a threshold signal strength value for sending the first message via one or more additional serving cells) . Base station 105-a may provide higher layer signaling (e.g., RRC signaling) indicating the threshold. For instance, base station 105-a may send an RRC message including an RRC IE indicating the threshold signal level (e.g., IE: ThreshForPCellRecovery) . UE 115-a may use the indicated threshold to determine whether another serving cell 205 can be used to send the first message and perform the fast recovery process. The RRC indicated threshold may correspond to a preferred or minimum level of reliability for a serving cell 205.

In some examples, UE 115-a may determine that multiple serving cells 205 have a signal strength that satisfies the threshold signal strength, and are viable options for sending the first message. For instance, serving cell 205-b (e.g., an SCell) and serving cell 205-c (e.g., an SCell) may have a signal strength that is equal to or above the threshold signal strength. UE 115-a may determine that both serving cell 205-b and serving cell 205-c are viable options for a fast recovery process based on performing one or more measurements (e.g., RSRP, RSRQ, or the like) on serving cell 205-b and serving cell 205-c. UE 115-a may select one of serving cell 205-b and serving cell 205-c on which to send the first message. The selecting may be implementation-based or in accordance with a wireless communications standard. In some examples, UE 115-a may select the additional serving cell 205 that has the highest signal strength, which may result in receiving a second message in response to the first message with a low delay. Thus, if link degradation occurs on serving cell 205-a, UE 115-a may determine that both serving cell 205-b and serving cell 205-c have signal strengths that satisfy the threshold signal strength value, and may compare the respective signal strengths of serving cell 205-b and serving cell 205-c. If UE 115-a determines that serving cell 205-b has a higher signal strength than serving cell 205-c, then UE 115-a may transmit the first message to base station 105-a on serving cell 205-b. In some examples, UE 115-a may include a report of the various signal strength measurements taken on a set of qualifying serving cells 205 (e.g., serving cell 205-b and serving cell 205-c) in the first message, and base station 105-a may select and indicate to UE 115-a the serving cell 205 UE 115-a is to use for one or more subsequent actions. In some cases, UE 115-a may select a second serving cell 205 for performing a fast recovery procedure if the signal strength of the serving cell 205 is greater than or equal to the configured threshold for at least the threshold amount of time, and if the serving cell 205 satisfies one or more preconditions described herein.

In some examples, UE 115-a may determine whether a potential second serving cell 205 for transmitting the first message to base station 105-a satisfies one or more preconditions. In such examples, UE 115-a may select a serving cell 205 for transmitting the first message to base station 105-a only if the serving cell 205 both has a signal strength that satisfies the first threshold and if the serving cell 205 satisfies the one or more preconditions.

In some examples, a precondition may be that a potential second serving cell 205 has been configured for downlink and uplink transmissions, and has been activated by base station 105-a. For example, base station 105-a may configure and activate serving cell 205-a for downlink and uplink transmissions. In such examples, base station 105-a may configure serving cell 205-b with one or more physical uplink control channel (PUCCH) resources that UE 115-a may use for transmitting uplink scheduling requests to obtain uplink grants for transmitting the first message (e.g., an RRC PCell failure indication) to base station 105-a upon detection of degradation on serving cell 205-a. Base station 105-a may also configure physical downlink control channel (PDCCH) resources and physical uplink control channel (PUSCH) resources on serving cell 205-b for downlink scheduling assignments, hybrid automatic repeat request (HARQ) Feedback on which base station 105-b may transmit a second message in response to the first message.

In some examples, a precondition may be that a potential second serving cell 205 has been configured to perform measurements on the potential second serving cell 205. That is, base station 105-a may configure UE 115-a to perform measurements on serving cell 205-b, to determine whether serving cell 205-b has a high enough signal strength to carry the first message to base station 105-a. In some examples, base station 105-a may configure UE 115-a to perform one or more measurements on serving cell 205-a to handle additional traffic loads.

In some examples, a precondition may be that UE 115-a is configured to send the first message of a particular bearer, such as a signal radio bearer 1 (SRB1) . In some examples, an SRB is used for communicating RRC messages (e.g., RRC connection reconfiguration, RRC connection release, or the like) . Thus, base station 105-a may configure UE 115-a such that the logical channel configuration of an SRB1 bearer allows the first message to be transmitted over a second serving cell 205 (e.g., an SCell, such as serving cell 205-b) .

In some examples, a precondition may be that a set of restrictions are not applied to the potential second serving cell 205 (e.g., serving cell 205-b) . In some cases, some restrictions may be placed on a serving cell 205 if an SRB1 logical channel configuration contains a list of allowed serving cells (e.g., an RRC IE AllowedServingCells may indicate a list of allowed serving cells 205) . In such examples, uplink media access control (MAC) service data units (SDUs) from the logical channel may only be mapped to serving cells indicated in the allowed serving cells IE. Such restrictions may be applied for some communication types (e.g., ultra reliable low latency communication (URLLC) ) or scenarios where DRB/SRB associated with a logical channel are configured with PDCP CA duplication in uplink, which may not be applicable to an SRB1 in the described techniques. Thus, a UE may determine that a second service cell 205 (e.g., serving cell 205-b) is not restricted (e.g., is allowed) before transmitting the first message over the second serving cell 205.

In some cases, there may be no second serving cells 205 that have a signal strength that satisfies the threshold signal strength value. In some examples, UE 115-a may determine that no second serving cell 205 satisfies the one or more preconditions described herein. In such examples, UE 115-a may refrain from transmitting a first message. Instead, UE 115-a may initiate a re-establishment procedure. In such scenarios, UE 115-a may identify one or more potential new serving cells 205 (e.g., different than serving cell 205-a, which may be an example of a PCell) , and may perform a random access procedure to initiate communications thereon.

UE 115-a may initiate a timer (e.g., a guard timer) upon transmitting the first message. If UE 115-a does not receive a response message from base station 105-a by the time the timer expires, then UE 115-a may initiate a re-establishment procedure.

Base station 105-a may receive, via serving cell 205-b (e.g., an SCell) , the first message indicating the status of serving cell 205-a (e.g., a PCell) . Base station 105-a may determine a network response to the first message, and may send a second message to UE 115-a in response to receiving the first message. For instance, base station 105-a may transmit, via serving cell 205-b, an instruction to perform an RRC reconfiguration procedure. The RRC reconfiguration procedure may include performing a handover from serving cell 205-a to another serving cell 205. In such examples, UE 115-a may perform a handover from serving cell 205-a to serving cell 205-b (the serving cell 205 on which the first and second messages have been transmitted) . In some examples, UE 115-a may perform a handover from serving cell 205-a to another serving cell that is different from 205-b. That is, as described above, UE 115-a may perform measurements on a set of serving cells 205 (e.g., including serving cell 205-a, serving cell 205-b, serving cell 205-c, other serving cells 205, other frequencies, serving cells 205 corresponding to another base station 105, or the like) . UE 115-a may include these measurements in the first message. Base station 105-a may select one of the serving cells 205 included in the first message (e.g., serving cell 205-c) , and may indicate in the second message that UE 115-a should perform a handover procedure between serving cell 205-a and serving cell 205-c and perform subsequent communications using serving cell 205-c. In some cases, serving cell 205-a may be a PCell and serving cell 205-c may be an SCell, and upon performing the indicated handover procedure as part of an RRC reconfiguration procedure, UE 115-a may select serving cell 205-c as a new PCell. In some examples, base station 105-a may instruct UE 115-a to perform a handover procedure to a serving cell 205 that is a PCell for another base station 105, and UE 115-a may perform the handover procedure and may communicate via the new PCell with the other base station 105.

In some examples, the second message may be an RRC release message. In such examples, base station 105-a may determine that none of the serving cells 205 included in the first message satisfy a threshold signal strength threshold, or are otherwise not sufficiently reliable for subsequent communications. In such examples, base station 105-a may send the RRC release message to UE 115-a, and UE 115-a may enter an idle mode or an inactive mode.

The techniques described with respect to FIG. 2 are described with respect to a UE 115-a that is in a carrier aggregation mode without dual connectivity mode. However, the described techniques may similarly be applied to a UE 115 in a combined carrier aggregation and dual connectivity mode. In such examples, serving cells 205 may be configured into two subsets: an MCG and an SCG. The MCG may be provided by a first base station 105 (e.g., base station 105-a) which may be referred to as a master base station 105, and the SCG may be provided by a second base station 105 (not shown) , which may be referred to as a secondary base station. One serving cell 205 of the MCG may be a PCell, and the MCG may also include any number of secondary cells. One serving cell 205 of the SCG may be a primary secondary cell PSCell, and the SCG may also include any number of secondary cells.

As described herein, a UE 115-a may perform a fast recovery process by determining that a signal strength has degraded on a first serving cell 205, and transmitting a first message to a base station 105 on a second (e.g., still viable) serving cell 205. The UE 115-a may select the most reliable of a set of possible second serving cells 205. Thus, in a carrier aggregation mode, the first serving cell 205 may be a PCell, and the second serving cell 205 may be a SCell. In a carrier aggregation dual connectivity mode, the first serving cell 205 may be a PCell, and the second serving cell 205 may be an SCell of the MSG or SCG; the first serving cell 205 may be the PCell of the MSG, and the second serving cell 205 may be the PSCell of the SCG; the first serving cell 205 may be the PSCell of the SCG, and the second cell may be the PCell or an SCell of the MSG or SCG, etc.

FIG. 3 illustrates an example of a process flow 300 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. In some examples, process flow 300 may implement aspects of wireless communication system 100 and wireless communication system 200.

Base station 105-b and UE 115-b may communicate in a carrier aggregation (CA) mode. In such examples, base station 105-b and UE 115-b may communicate via two or more carriers of multiple serving cells. In some examples, base station 105-b may support and may configure UE 115-b to communicative via two or more serving cells (e.g., a primary cell (PCell) and one or more secondary cells (SCells) ) .

In some examples, base station 105-b may send one or more reference signals, which UE 115-b may receive and perform one or more measurements on (e.g., UE 115-b may perform RLM to determine signal strength on one or more serving cells) .

At 305, UE 115-b may detect degradation of a first carrier of a first cell (e.g., a PCell) . That is, UE 115-b may initiate an event-based fast recovery procedure (e.g., a conditional recovery procedure) by determining that an event has occurred (e.g., RLF or radio link degradation) , and determining whether a fast recovery procedure may be triggered based on the event. In some examples, UE 115-b may perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell, and may detect degradation of the first cell based on the one or more measurements. For instance, base station 105-b may configure UE 115-b with a second threshold different from the first threshold used at 310 (e.g., base station 105-b may transmit an RRC signal indicating a threshold signal strength value) , and UE 115-b may determine whether the parameter (e.g., the signal strength of the first cell) has fallen below the second threshold. In some examples, UE 115-b may perform one or more measurements (e.g., may perform RLM) and may detect RLF on the first cell. In some examples, the second threshold may be greater than or equal to the first threshold.

In some examples, the first threshold may be higher than the second threshold (e.g., by a fixed offset) . That is, if the first threshold (e.g., the threshold by which UE 115-b determines whether it can transmit the first message on the second cell) is too close to the second threshold (e.g., the threshold by which UE 115-b determines whether signal strength on the first cell has dropped too low for subsequent reliable communications) , then UE 115-b may attempt to send the first message at 325 unsuccessfully. This may occur because if the signal strength of the second cell is too close to RLF, then small changes in the link quality may result in one or more failed transmissions or retransmissions. Thus, the first threshold may be higher than the second threshold to increase the likelihood of successful transmission of the first message on the second cell. Where the first threshold and the second threshold have been configured by base station 105-b, UE 115-b may initiate a fast recovery procedure if the signal level on a PCell (e.g., based on RSRP or RSRQ measurement) is below the second threshold, and the SCell signal level (e.g., based on RSRP or RSRQ measurement) is greater than or equal to the first threshold. Or, if RLF occurs on the PCell, and the SCell signal level is greater than or equal to the first threshold, UE 115-b may initiate the fast recovery procedure.

At 310, UE 115-b may determine whether a first parameter (e.g., a signal strength) for a second carrier of a second cell (e.g., an SCell) satisfies a first threshold (e.g., is greater than or equal to a first threshold) . In some examples, base station 105-b may indicate (e.g., via an RRC IE) the first threshold. The UE 115-b may determine whether the first parameter (e.g., a signal strength value) for the second cell satisfies the first threshold (e.g., is equal to or greater than the threshold value) by performing one or more measurements (e.g., RSRP, RSRQ, or the like) . In some examples, UE 115-b may transmit the first message at 325 based at least in part on determining that the first parameter for the second cell satisfies the first threshold.

In some examples, UE 115-b may determine whether the parameter (e.g., signal strength) of service cell 205-b satisfies the threshold for a period of time (e.g., a set period of time) . That is, instead of determining a signal strength on a particular cell instantaneously or for an amount of time too short to determine an accurate signal strength, UE 115-b may evaluate (e.g., may perform one or more measurements) a signal strength cell for a at least a threshold amount of time to determine a more accurate signal strength. In some examples, base station 105-b may indicate, to UE 115-b, the threshold amount of time during which the signal strength of cell is to remain greater than or equal to the threshold if the UE 115-b is to perform a fast recovery procedure. For instance, base station 105-b may configure the threshold amount of time via higher layer signaling. In such examples, base station 105-b may transmit an RRC message including an RRC information element (IE) indicating the configured threshold amount of time (e.g., RRC IE: timeToTrigger) . UE 115-b may receive the RRC message, and may perform measurements (e.g., RSRP, RSRQ, etc. ) for the amount of time indicated in the RRC message. If the signal strength of cell is greater than or equal to the threshold for the configured duration, then UE 115-b may initiate a fast recovery procedure (e.g., may send the first message described herein) .

In some examples, UE 115-b may also determine whether the second carrier of the second cell satisfies one or more preconditions (e.g., one or more configuration conditions) . For instance, UE 115-b may receive, from base station 105-b, a resource allocation for uplink control signaling, downlink control signaling, an uplink scheduling request, HARQ signaling, or a combination thereof. UE 115-b may determine that a precondition is met based on receiving the resource allocation. In some examples, UE 115-b may receive, from base station 105-b, a configuration message instructing UE 115-b to perform one or more measurements on the first cell, the second cell, one or more additional cells, or the like. UE 115-b may determine that a precondition is met based on the configuration message. IN some cases, UE 115-b receive, from base station 105-b, a configuration message instructing UE 115-b to send the first message via a first bearer (e.g., an SRB1 bearer) . UE 115-b may determine that a precondition is met based on the configuration message. In some cases, UE 115-b may receive, from the base station, a configuration message indicating that the first cell and the second cell are optional carriers for transmitting the first message at 325, and UE 115-b may determine that a precondition is met based on the configuration message.

At 315, UE 115-b may, in some examples, initiate an RRC re-establishment procedure. For instance, UE 115-b may determine that the first parameter corresponding to the second cell does not satisfy the threshold (e.g., the signal strength of the second cell is below the threshold signal strength value) , and UE 115-b may initiate the RRC re-establishment procedure based on the determining.

At 320, UE 115-b may select a second carrier of the second cell from one or more additional carriers. For instance, UE 115-b may determine that a set of cells (e.g., a set of SCells) have a signal strength that satisfies the threshold, that the set of cells satisfies one or more preconditions, or both. The UE 115-a may select one of the set of cells (e.g., may select the cell that has the highest signal strength) and may send the first message on the selected cell at 325. In some examples, UE 115-b may include a report of measurements taken (e.g., RSRP, RSRQ, or the like) for each of the set of cells in the first message transmitted at 325. In some cases, none of the set of cells may satisfy the precondition, have a signal strength that is equal to or greater than the threshold, or both. In such cases, UE 115-b may initiate an RRC re-establishment procedure at 315.

At 325, UE 115-b may transmit, and base station 105-b may receive, a first message. UE 115-b may transmit the first message via the second cell. UE 115-b may transmit the first message over a PUSCH. The first message may be, for instance, an RRC PCell failure indication message. The first message may indicate a status of the first cell (e.g., RLF, signal strength degradation, or the like) . In some examples, the first message may be an RRC failure information message (e.g., an RRC IE: Failureinformation) . Such a message may be utilized where CA duplication is configured and activated or where CA duplication is not configured or activated.

In some examples, UE 115-b may initiate, upon transmitting the first message at 325, a timer. The timer may be, for instance, a guard timer. Base station 105-b may configure UE 115-b to perform an RRC reestablishment procedure if the second message is not received before the expiration of the timer. Thus, UE 115-b may monitor for a second message until the timer expires. If the timer expires prior to receiving a second message from base station 105-b, then UE 115-b may perform an RRC reestablishment procedure. If UE 115-b does receive the second message at 335, then UE 115-b may take one or more actions according to the second message at 340.

At 330, base station 105-b may determine a network response to the first message. For example, base station 105-b may determine whether to transmit an instruction to perform an RRC reconfiguration procedure or an RRC release procedure. If base station 105-b determines another cell on which to subsequently communicate, then base station 105-b may instruct UE 115-b to perform an RRC reconfiguration procedure. For instance, the second cell (e.g., on which the first message was transmitted at 325) may be a viable cell for subsequent communication (e.g., may satisfy a threshold signal strength value) . In such examples, base station 105-b may instruct UE 115-b to perform an RRC reconfiguration procedure, and subsequently communicate via the second cell (e.g., make the SCell on which the first message was transmitted at 325 a new PCell) . In some examples, where the first message includes a report of one or more measurements taken on each of a set of cells, base station 105-b may determine which, if any of the cells, is viable for subsequent communication. If none of the set of cells (e.g., including the second cell on which the first message was transmitted) is viable for subsequent communication (e.g., the signal strength of each of the set of cells is below a threshold signal strength value) , then base station 105-b may transmit an RRC release message.

At 335, base station 105-b may transmit, and UE 115-b may receive, a second message. The second message may include an instruction to perform an RRC release message or an RRC reconfiguration message, as described above.

At 340, UE 115-b may perform an RRC reconfiguration procedure or an RRC release procedure. For instance, if so instructed, UE 115-b may perform an RRC release procedure, and may enter an idle mode or an inactive mode. If UE 115-b receives an instruction at 435 to perform an RRC reconfiguration procedure, then UE 115-b may perform a handover from the first cell to another cell. The other cell may be an SCell (e.g., the cell on which the second message was received) or another cell (e.g., another SCell reported on in the first message, a PCell or SCell corresponding to another base station, another cell that is not one of the set of SCells, or the like) .

The techniques described with respect to FIG. 3 are described with respect to a UE 115-b that is in a carrier aggregation mode without a dual connectivity mode. However, the described techniques may similarly be applied to a UE 115 in a combined carrier aggregation and dual connectivity mode. In such examples, serving cells may be configured into two subsets: an MCG and an SCG. The MCG may be provided by a first base station 105 (e.g., base station 105-b) which may be referred to as a master base station 105, and the SCG may be provided by a second base station 105 (not shown) , which may be referred to as a secondary base station. One cell of the MCG may be a PCell, and the MCG may also include any number of secondary cells. One cell of the SCG may be a PSCell, and the SCG may also include any number of secondary cells.

As described herein, a UE 115-b may perform a fast recovery process by determining that a signal strength has degraded on a first cell, and transmitting a first message to a base station 105 on a second (e.g., still viable) cell. The UE 115-b may select the most reliable of a set of possible second cells. Thus, in a carrier aggregation mode, the first cell may be a PCell, and the second cell may be a SCell. In a carrier aggregation dual connectivity mode, the described techniques may be used for fast MCG recovery procedures. For instance, the first cell may be a PCell, and the second cell may be an SCell of the MSG or SCG; the first cell may be the PCell of the MSG, and the second cell may be the PSCell of the SCG; the first cell may be the PSCell of the SCG experiencing RLF, and the second cell may be the PCell or an SCell of the MSG or SCG, etc.

FIG. 4 shows a block diagram 400 of a device 405 that supports recovery from cell failure in carrier aggregation 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 recovery from cell failure in carrier aggregation, etc. ) . Information may be passed on to other components of the device 405. The receiver 410 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The receiver 410 may utilize a single antenna or a set of antennas.

The communications manager 415 may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier. The communications manager 415 may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold. The communications manager 415 may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell. The communications manager 415 may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure. The communications manager 415 may be an example of aspects of the communications manager 710 described herein.

The communications manager 415, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 415, or its sub-components may be executed by a general-purpose processor, a 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. For example, the transmitter 420 may be an example of aspects of the transceiver 720 described with reference to FIG. 7. The transmitter 420 may utilize a single antenna or a set of antennas.

In some examples, the communications manager 415 may be implemented as an integrated circuit or chipset for a mobile device modem, and the receiver 410 and transmitter 420 may be implemented as analog components (e.g., amplifiers, filters, antennas) coupled with the mobile device modem to enable wireless transmission and reception over one or more bands.

The communications manager 415 as described herein may be implemented to realize one or more potential advantages, including efficiency, decreased system latency, improved signal quality, and improved user experience.

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

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

The communications manager 515 may be an example of aspects of the communications manager 415 as described herein. The communications manager 515 may include a cell degradation manager 520, a threshold manager 525, a cell status manager 530, and an instruction manager 535. The communications manager 515 may be an example of aspects of the communications manager 710 described herein.

The cell degradation manager 520 may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier.

The threshold manager 525 may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold.

The cell status manager 530 may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell.

The instruction manager 535 may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure.

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

FIG. 6 shows a block diagram 600 of a communications manager 605 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The communications manager 605 may be an example of aspects of a communications manager 415, a communications manager 515, or a communications manager 710 described herein. The communications manager 605 may include a cell degradation manager 610, a threshold manager 615, a cell status manager 620, an instruction manager 625, a measurement manager 630, a RLF manager 635, a configuration condition manager 640, and a timer manager 645. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The cell degradation manager 610 may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier.

The threshold manager 615 may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold. In some examples, the threshold manager 615 may receive, from the base station, an indication of the second threshold, where determining that the second parameter for the first carrier of the first cell is below the second threshold is based on receiving the indication of the second threshold. In some examples, the threshold manager 615 may receive, from the base station, an indication of the first threshold, where determining whether the first parameter satisfies the first threshold is based on the indication of the first threshold. The threshold manager 615 may determine, based at least in part on the degradation, whether the first parameter for the second carrier satisfies the first threshold for at least a threshold amount of time, wherein sending the first message via the second carrier is based at least in part on determining that the first parameter for the second carrier satisfies the first threshold for at least the threshold amount of time. The threshold manager 615 may receive, from the base station, an indication of the threshold amount of time.

The cell status manager 620 may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell. In some examples, the cell status manager 620 may communicate with the base station via the second carrier of the second cell. In some examples, the cell status manager 620 may determine, based on the one or more measurements, that a second parameter for the first carrier of the first cell is below a second threshold.

In some examples, the cell status manager 620 may determine, based on the detecting, that a respective first parameter for one or more of a set of additional carriers corresponding to a set of cells, where a set of respective parameters corresponds to the set of carriers satisfies the first threshold. In some examples, the cell status manager 620 may select the second carrier of the second cell from the one or more additional carriers. In some examples, the cell status manager 620 may determine that the first parameter for the second carrier is greater than each of the respective first parameters for the one or more additional carriers, where selecting the second carrier is based on the first parameter for the second carrier being greater than each of the respective first parameters for the one or more additional carriers. In some cases, the first cell is a primary cell and the second cell is a secondary cell. In some cases, the first cell is a primary cell in a master cell group and the second cell is a primary secondary cell in a secondary cell group; or. In some cases, the first cell is the primary secondary cell in the secondary cell group and the second cell is the primary cell in the master cell group.

The instruction manager 625 may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure. In some examples, the instruction manager 625 may perform, based on receiving the second message, the RRC reconfiguration procedure. In some examples, the instruction manager 625 may select a third carrier of a third cell. In some examples, the instruction manager 625 may perform a handover procedure between the first carrier of the first cell and the third carrier of the third cell. In some examples, the instruction manager 625 may communicate with the base station via the third carrier of the third cell.

In some examples, the instruction manager 625 may perform, based on receiving the second message, the RRC release procedure. In some examples, the instruction manager 625 may enter an idle mode or an inactive mode based on performing the RRC release procedure. In some cases, the second cell and the third cell are the same.

The measurement manager 630 may perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell, where detecting the degradation of the first carrier is based on the one or more measurements. In some examples, the measurement manager 630 may include the performed one or more measurements in the first message, where the second message is based on the performed one or more measurements. In some cases, the one or more measurements include one or more of a reference signal received power (RSRP) and a reference signal received quality (RSRQ) .

The RLF manager 635 may detect, based on the one or more measurements, radio link failure (RLF) of the carrier.

The configuration condition manager 640 may determine, based on the degradation, that a configuration condition for the second cell is satisfied, where sending the first message is based on determining that the configuration condition is satisfied. In some examples, the configuration condition manager 640 may receive, from the base station, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and HARQ signaling. In some examples, the configuration condition manager 640 may receive, from the base station, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell. In some examples, the configuration condition manager 640 may receive, from the base station, a configuration message instructing the UE to send the first message via a first bearer. In some examples, the configuration condition manager 640 may receive, from the base station, a configuration message indicating the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.

The timer manager 645 may initiate, upon transmitting the first message, a timer. In some examples, the timer manager 645 may monitor for the second message while the timer is active. In some examples, the timer manager 645 may receive the second message prior to an expiration of the timer. In some cases, the UE is configured to perform an RRC reestablishment procedure if the second message is not received before the expiration of the timer.

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

The communications manager 710 may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier. The communications manager 710 may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold. The communications manager 710 may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell. The communications manager 710 may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure.

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

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

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

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

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

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

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

FIG. 8 shows a block diagram 800 of a device 805 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The device 805 may be an example of aspects of a base station 105 as described herein. The device 805 may include a receiver 810, a communications manager 815, and a transmitter 820. The device 805 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 810 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 recovery from cell failure in carrier aggregation, etc. ) . Information may be passed on to other components of the device 805. The receiver 810 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 810 may utilize a single antenna or a set of antennas.

The communications manager 815 may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell. The communications manager 815 may receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell. The communications manager 815 may determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure. The communications manager 815 may transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure. The communications manager 815 may be an example of aspects of the communications manager 1110 described herein.

The communications manager 815, 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 815, 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 815, 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 815, 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 815, 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 820 may transmit signals generated by other components of the device 805. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 820 may utilize a single antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The device 905 may be an example of aspects of a device 805, or a base station 105 as described herein. The device 905 may include a receiver 910, a communications manager 915, and a transmitter 935. The device 905 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 910 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 recovery from cell failure in carrier aggregation, etc. ) . Information may be passed on to other components of the device 905. The receiver 910 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 910 may utilize a single antenna or a set of antennas.

The communications manager 915 may be an example of aspects of the communications manager 815 as described herein. The communications manager 915 may include a cell configuration manager 920, a cell status manager 925, and an instruction manager 930. The communications manager 915 may be an example of aspects of the communications manager 1110 described herein.

The cell configuration manager 920 may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell.

The cell status manager 925 may receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell.

The instruction manager 930 may determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure and transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

The transmitter 935 may transmit signals generated by other components of the device 905. In some examples, the transmitter 935 may be collocated with a receiver 910 in a transceiver module. For example, the transmitter 935 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 935 may utilize a single antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a communications manager 1005 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The communications manager 1005 may be an example of aspects of a communications manager 815, a communications manager 915, or a communications manager 1110 described herein. The communications manager 1005 may include a cell configuration manager 1010, a cell status manager 1015, an instruction manager 1020, a measurement manager 1025, a threshold manager 1030, and a configuration condition manager 1035. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The cell configuration manager 1010 may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell.

The cell status manager 1015 may receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell.

The instruction manager 1020 may determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure. In some examples, the instruction manager 1020 may transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure. In some cases, the first message includes one or more measurements corresponding to the first carrier of the first cell and the second carrier of the second cell, where the determining is based on the one or more measurements.

The threshold manager 1030 may transmit, to the UE, an indication of a first threshold corresponding to a first parameter for a second carrier of a second cell, where receiving the first message is based on the first threshold. In some examples, the threshold manager 1030 may transmit, to the UE, an indication of a second threshold corresponding to the first parameter for the first carrier of the first cell, where receiving the first message is based on the second threshold. The threshold manager 1030 may transmit, to the UE, an indication of a threshold amount of time, wherein receiving the first message is based at least in part on the first parameter for the second carrier of the second cell, the first threshold, and the threshold amount of time.

The configuration condition manager 1035 may transmit, to the UE, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and HARQ signaling. In some examples, the configuration condition manager 1035 may transmit, to the UE, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell. In some examples, the configuration condition manager 1035 may transmit, to the UE, a configuration message instructing the UE to send the first message via a first bearer. In some examples, the configuration condition manager 1035 may transmit, to the UE, a configuration message indicating that the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.

FIG. 11 shows a diagram of a system 1100 including a device 1105 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The device 1105 may be an example of or include the components of device 805, device 905, or a base station 105 as described herein. The device 1105 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 1110, a network communications manager 1115, a transceiver 1120, an antenna 1125, memory 1130, a processor 1140, and an inter-station communications manager 1145. These components may be in electronic communication via one or more buses (e.g., bus 1150) .

The communications manager 1110 may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell, receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell, determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure, and transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.

The network communications manager 1115 may manage communications with the core network (e.g., via one or more wired backhaul links) . For example, the network communications manager 1115 may manage the transfer of data communications for client devices, such as one or more UEs 115.

The transceiver 1120 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1120 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1120 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125. However, in some cases the device may have more than one antenna 1125, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 1130 may include RAM, ROM, or a combination thereof. The memory 1130 may store computer-readable code 1135 including instructions that, when executed by a processor (e.g., the processor 1140) cause the device to perform various functions described herein. In some cases, the memory 1130 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 1140 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, the processor 1140 may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor 1140. The processor 1140 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1130) to cause the device 1105 to perform various functions (e.g., functions or tasks supporting recovery from cell failure in carrier aggregation) .

The inter-station communications manager 1145 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 1145 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 1145 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

The code 1135 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1135 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1135 may not be directly executable by the processor 1140 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 12 shows a flowchart illustrating a method 1200 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The operations of method 1200 may be implemented by a UE 115 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. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally, or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1205, the UE may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier. 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 cell degradation manager as described with reference to FIGs. 4 through 7.

At 1210, the UE may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold. 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 threshold manager as described with reference to FIGs. 4 through 7.

At 1215, the UE may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell. 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 cell status manager as described with reference to FIGs. 4 through 7.

At 1220, the UE may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure. 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 an instruction manager as described with reference to FIGs. 4 through 7.

FIG. 13 shows a flowchart illustrating a method 1300 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 may be performed by a communications manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally, or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1305, the UE may receive, from the base station, an indication of the first threshold, where determining whether the first parameter satisfies the first threshold is based on the indication of the first threshold. The operations of 1305 may be performed according to the methods described herein. In some examples, aspects of the operations of 1305 may be performed by a threshold manager as described with reference to FIGs. 4 through 7.

At 1310, the UE may detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier. The operations of 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be performed by a cell degradation manager as described with reference to FIGs. 4 through 7.

At 1315, the UE may determine, based on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold. The operations of 1315 may be performed according to the methods described herein. In some examples, aspects of the operations of 1315 may be performed by a threshold manager as described with reference to FIGs. 4 through 7.

At 1320, the UE may send to the base station, based on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell. The operations of 1320 may be performed according to the methods described herein. In some examples, aspects of the operations of 1320 may be performed by a cell status manager as described with reference to FIGs. 4 through 7.

At 1325, the UE may receive from the base station, based on the first message, a second message via the second carrier of the second cell, the second message including an instruction to perform an RRC reconfiguration procedure or an RRC release procedure. The operations of 1325 may be performed according to the methods described herein. In some examples, aspects of the operations of 1325 may be performed by an instruction manager as described with reference to FIGs. 4 through 7.

FIG. 14 shows a flowchart illustrating a method 1400 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The operations of method 1400 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1400 may be performed by a communications manager as described with reference to FIGs. 8 through 11. 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 below. Additionally, or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1405, the base station may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell. The operations of 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be performed by a cell configuration manager as described with reference to FIGs. 8 through 11.

At 1410, the base station may receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell. The operations of 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1410 may be performed by a cell status manager as described with reference to FIGs. 8 through 11.

At 1415, the base station may determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be performed by an instruction manager as described with reference to FIGs. 8 through 11.

At 1420, the base station may transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure. The operations of 1420 may be performed according to the methods described herein. In some examples, aspects of the operations of 1420 may be performed by an instruction manager as described with reference to FIGs. 8 through 11.

FIG. 15 shows a flowchart illustrating a method 1500 that supports recovery from cell failure in carrier aggregation in accordance with aspects of the present disclosure. The operations of method 1500 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1500 may be performed by a communications manager as described with reference to FIGs. 8 through 11. 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 below. Additionally, or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1505, the base station may transmit, to the UE, an indication of a first threshold corresponding to a first parameter for a second carrier of a second cell, where receiving the first message is based on the first threshold. The operations of 1505 may be performed according to the methods described herein. In some examples, aspects of the operations of 1505 may be performed by a threshold manager as described with reference to FIGs. 8 through 11.

At 1510, the base station may configure a UE for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell. The operations of 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a cell configuration manager as described with reference to FIGs. 8 through 11.

At 1515, the base station may receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell. The operations of 1515 may be performed according to the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a cell status manager as described with reference to FIGs. 8 through 11.

At 1520, the base station may determine, based on the first message, whether to instruct the UE to perform a RRC reconfiguration procedure, or an RRC release procedure. The operations of 1520 may be performed according to the methods described herein. In some examples, aspects of the operations of 1520 may be performed by an instruction manager as described with reference to FIGs. 8 through 11.

At 1525, the base station may transmit, to the UE via the second carrier of the second cell, a second message including an instruction to perform the RRC reconfiguration procedure or the RRC release procedure. The operations of 1525 may be performed according to the methods described herein. In some examples, aspects of the operations of 1525 may be performed by an instruction manager as described with reference to FIGs. 8 through 11.

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 random-access memory (RAM) , read-only memory (ROM) , electrically erasable programmable ROM (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items (e. g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

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

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

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

Claims

A method for wireless communications, comprising:

detecting, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier;

determining, based at least in part on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold;

sending to the base station, based at least in part on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell; and

receiving from the base station, based at least in part on the first message, a second message via the second carrier of the second cell, the second message comprising an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.
The method of claim 1, further comprising:

communicating with the base station via the second carrier of the second cell; and

performing one or more measurements on the first carrier of the first cell and the second carrier of the second cell, wherein detecting the degradation of the first carrier is based at least in part on the one or more measurements.
The method of claim 2, wherein detecting a degradation of the first carrier further comprises:

detecting, based at least in part on the one or more measurements, radio link failure (RLF) of the carrier.
The method of claim 2, wherein detecting a degradation of the first carrier further comprises:

determining, based at least in part on the one or more measurements, that a second parameter for the first carrier of the first cell is below a second threshold.
The method of claim 4, further comprising:

receiving, from the base station, an indication of the second threshold, wherein determining that the second parameter for the first carrier of the first cell is below the second threshold is based at least in part on receiving the indication of the second threshold.
The method of claim 2, wherein the one or more measurements comprise one or more of a reference signal received power (RSRP) and a reference signal received quality (RSRQ) .
The method of claim 2, further comprising:

including the performed one or more measurements in the first message, wherein the second message is based at least in part on the performed one or more measurements.
The method of claim 1, further comprising:

receiving, from the base station, an indication of the first threshold, wherein determining whether the first parameter satisfies the first threshold is based at least in part on the indication of the first threshold.
The method of claim 1, further comprising:

determining, based at least in part on the degradation, whether the first parameter for the second carrier satisfies the first threshold for at least a threshold amount of time, wherein sending the first message via the second carrier is based at least in part on determining that the first parameter for the second carrier satisfies the first threshold for at least the threshold amount of time.
The method of claim 11, further comprising:

receiving, from the base station, an indication of the threshold amount of time.
The method of claim 1, further comprising:

determining, based at least in part on the detecting, that a respective first parameter for one or more of a set of additional carriers corresponding to a set of cells, wherein a set of respective parameters corresponds to the set of carriers satisfies the first threshold; and

selecting the second carrier of the second cell from the one or more additional carriers.
The method of claim 11, further comprising:

determining that the first parameter for the second carrier is greater than each of the respective first parameters for the one or more additional carriers, wherein selecting the second carrier is based at least in part on the first parameter for the second carrier being greater than each of the respective first parameters for the one or more additional carriers.
The method of claim 1, further comprising:

determining, based at least in part on the degradation, that a configuration condition for the second cell is satisfied, wherein sending the first message is based at least in part on determining that the configuration condition is satisfied.
The method of claim 13, wherein the configuration condition comprises:

receiving, from the base station, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and hybrid automatic repeat request (HARQ) signaling.
The method of claim 13, wherein the configuration condition comprises:

receiving, from the base station, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.
The method of claim 13, wherein the configuration condition comprises:

receiving, from the base station, a configuration message instructing the UE to send the first message via a first bearer.
The method of claim 13, wherein the configuration condition comprises:

receiving, from the base station, a configuration message indicating the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.
The method of claim 1, further comprising:

performing, based at least in part on receiving the second message, the RRC reconfiguration procedure.
The method of claim 18, wherein performing the RRC reconfiguration procedure comprises:

selecting a third carrier of a third cell;

performing a handover procedure between the first carrier of the first cell and the third carrier of the third cell; and

communicating with the base station via the third carrier of the third cell.
The method of claim 19, wherein the second cell and the third cell are the same.
The method of claim 1, further comprising:

performing, based at least in part on receiving the second message, the RRC release procedure; and

entering an idle mode or an inactive mode based at least in part on performing the RRC release procedure.
The method of claim 1, further comprising:

initiating, upon transmitting the first message, a timer;

monitoring for the second message while the timer is active; and

receiving the second message prior to an expiration of the timer.
The method of claim 22, wherein the UE is configured to perform an RRC reestablishment procedure if the second message is not received before the expiration of the timer.
The method of claim 1, wherein:

the first cell is a primary cell and the second cell is a secondary cell;

the first cell is a primary cell in a master cell group and the second cell is a primary secondary cell in a secondary cell group; or; and

the first cell is the primary secondary cell in the secondary cell group and the second cell is the primary cell in the master cell group.
A method for wireless communications, comprising:

configuring a user equipment (UE) for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell;

receiving, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell;

determining, based at least in part on the first message, whether to instruct the UE to perform a radio resource control (RRC) reconfiguration procedure, or an RRC release procedure; and

transmitting, to the UE via the second carrier of the second cell, a second message comprising an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.
The method of claim 25, wherein the first message comprises one or more measurements corresponding to the first carrier of the first cell and the second carrier of the second cell, wherein the determining is based at least in part on the one or more measurements.
The method of claim 25, further comprising:

transmitting, to the UE, an indication of a first threshold corresponding to a first parameter for a second carrier of a second cell, wherein receiving the first message is based at least in part on the first threshold.
The method of claim 27, further comprising:

transmitting, to the UE, an indication of a threshold amount of time, wherein receiving the first message is based at least in part on the first parameter for the second carrier of the second cell, the first threshold, and the threshold amount of time.
The method of claim 25, further comprising:

transmitting, to the UE, an indication of a second threshold corresponding to the first parameter for the first carrier of the first cell, wherein receiving the first message is based at least in part on the second threshold.
The method of claim 25, further comprising:

transmitting, to the UE, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and hybrid automatic repeat request (HARQ) signaling.
The method of claim 25, further comprising:

transmitting, to the UE, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.
The method of claim 25, further comprising:

transmitting, to the UE, a configuration message instructing the UE to send the first message via a first bearer.
The method of claim 25, further comprising:

transmitting, to the UE, a configuration message indicating that the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.
An apparatus for wireless communications, comprising:

a processor,

memory coupled with the processor; and

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

detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier;

determine, based at least in part on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold;

send to the base station, based at least in part on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell; and

receive from the base station, based at least in part on the first message, a second message via the second carrier of the second cell, the second message comprising an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

communicate with the base station via the second carrier of the second cell; and

perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell, wherein detecting the degradation of the first carrier is based at least in part on the one or more measurements.
The apparatus of claim 35, wherein the instructions to detect a degradation of the first carrier further are executable by the processor to cause the apparatus to:

detect, based at least in part on the one or more measurements, radio link failure (RLF) of the carrier.
The apparatus of claim 35, wherein the instructions to detect a degradation of the first carrier further are executable by the processor to cause the apparatus to:

determine, based at least in part on the one or more measurements, that a second parameter for the first carrier of the first cell is below a second threshold.
The apparatus of claim 37, wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from the base station, an indication of the second threshold, wherein determining that the second parameter for the first carrier of the first cell is below the second threshold is based at least in part on receiving the indication of the second threshold.
The apparatus of claim 35, wherein the one or more measurements comprise one or more of a reference signal received power (RSRP) and a reference signal received quality (RSRQ) .
The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

include the performed one or more measurements in the first message, wherein the second message is based at least in part on the performed one or more measurements.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from the base station, an indication of the first threshold, wherein determining whether the first parameter satisfies the first threshold is based at least in part on the indication of the first threshold.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

determine, based at least in part on the detecting, that a respective first parameter for one or more of a set of additional carriers corresponding to a set of cells, wherein a set of respective parameters corresponds to the set of carriers satisfies the first threshold; and

select the second carrier of the second cell from the one or more additional carriers.
The apparatus of claim 42, wherein the instructions are further executable by the processor to cause the apparatus to:

determine that the first parameter for the second carrier is greater than each of the respective first parameters for the one or more additional carriers, wherein selecting the second carrier is based at least in part on the first parameter for the second carrier being greater than each of the respective first parameters for the one or more additional carriers.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

determine, based at least in part on the degradation, that a configuration condition for the second cell is satisfied, wherein sending the first message is based at least in part on determining that the configuration condition is satisfied.
The apparatus of claim 44, wherein the configuration condition comprises:

receive, from the base station, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and hybrid automatic repeat request (HARQ) signaling.
The apparatus of claim 44, wherein the configuration condition comprises:

receive, from the base station, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.
The apparatus of claim 44, wherein the configuration condition comprises:

receive, from the base station, a configuration message instructing the UE to send the first message via a first bearer.
The apparatus of claim 44, wherein the configuration condition comprises:

receive, from the base station, a configuration message indicating the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

perform, based at least in part on receiving the second message, the RRC reconfiguration procedure.
The apparatus of claim 49, wherein the instructions to perform the RRC reconfiguration procedure are executable by the processor to cause the apparatus to:

select a third carrier of a third cell;

perform a handover procedure between the first carrier of the first cell and the third carrier of the third cell; and

communicate with the base station via the third carrier of the third cell.
The apparatus of claim 50, wherein the second cell and the third cell are the same.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

perform, based at least in part on receiving the second message, the RRC release procedure; and

enter an idle mode or an inactive mode based at least in part on performing the RRC release procedure.
The apparatus of claim 34, wherein the instructions are further executable by the processor to cause the apparatus to:

initiate, upon transmitting the first message, a timer;

monitor for the second message while the timer is active; and

receive the second message prior to an expiration of the timer.
The apparatus of claim 53, wherein the UE is configured to perform an RRC reestablishment procedure if the second message is not received before the expiration of the timer.
The apparatus of claim 34, wherein:

the first cell is a primary cell and the second cell is a secondary cell;

the first cell is a primary cell in a master cell group and the second cell is a primary secondary cell in a secondary cell group; or; and

the first cell is the primary secondary cell in the secondary cell group and the second cell is the primary cell in the master cell group.
An apparatus for wireless communications, comprising:

a processor,

memory coupled with the processor; and

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

configure a user equipment (UE) for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell;

receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell;

determine, based at least in part on the first message, whether to instruct the UE to perform a radio resource control (RRC) reconfiguration procedure, or an RRC release procedure; and

transmit, to the UE via the second carrier of the second cell, a second message comprising an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.
The apparatus of claim 56, wherein the first message comprises one or more measurements corresponding to the first carrier of the first cell and the second carrier of the second cell, wherein the determining is based at least in part on the one or more measurements.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, an indication of a first threshold corresponding to a first parameter for a second carrier of a second cell, wherein receiving the first message is based at least in part on the first threshold.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, an indication of a second threshold corresponding to the first parameter for the first carrier of the first cell, wherein receiving the first message is based at least in part on the second threshold.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, a resource allocation for one or more of uplink control signaling, downlink control signaling, an uplink scheduling request, and hybrid automatic repeat request (HARQ) signaling.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, a configuration message instructing the UE to perform one or more measurements on the first carrier of the first cell and the second carrier of the second cell.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, a configuration message instructing the UE to send the first message via a first bearer.
The apparatus of claim 56, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit, to the UE, a configuration message indicating that the first carrier of the first cell and the second carrier of the second cell are optional carriers for transmitting the first message.
An apparatus for wireless communications, comprising:

means for detecting, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier;

means for determining, based at least in part on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold;

means for sending to the base station, based at least in part on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell; and

means for receiving from the base station, based at least in part on the first message, a second message via the second carrier of the second cell, the second message comprising an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.
An apparatus for wireless communications, comprising:

means for configuring a user equipment (UE) for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell;

means for receiving, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell;

means for determining, based at least in part on the first message, whether to instruct the UE to perform a radio resource control (RRC) reconfiguration procedure, or an RRC release procedure; and

means for transmitting, to the UE via the second carrier of the second cell, a second message comprising an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

detect, while communicating with a base station via a first carrier of a first cell, a degradation of the first carrier;

determine, based at least in part on the degradation, whether a first parameter for a second carrier of a second cell that is different from the first cell satisfies a first threshold;

send to the base station, based at least in part on the determining, a first message via the second carrier of the second cell, the first message indicating a status of the first carrier of the first cell; and

receive from the base station, based at least in part on the first message, a second message via the second carrier of the second cell, the second message comprising an instruction to perform a radio resource control (RRC) reconfiguration procedure or an RRC release procedure.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

configure a user equipment (UE) for communications via a first carrier of a first cell and a second carrier of a second cell that is different from the first cell;

receive, from the UE via the second carrier of the second cell, a first message indicating a status of the first carrier of the first cell;

determine, based at least in part on the first message, whether to instruct the UE to perform a radio resource control (RRC) reconfiguration procedure, or an RRC release procedure; and

transmit, to the UE via the second carrier of the second cell, a second message comprising an instruction to perform the RRC reconfiguration procedure or the RRC release procedure.