WO2021168641A1

WO2021168641A1 - Fast radio link failure trigger

Info

Publication number: WO2021168641A1
Application number: PCT/CN2020/076521
Authority: WO
Inventors: Jinglin Zhang; Haojun WANG; Zhenqing CUI
Original assignee: Qualcomm Incorporated
Priority date: 2020-02-25
Filing date: 2020-02-25
Publication date: 2021-09-02

Abstract

Methods, systems, and devices for signaling for a fast radio link failure (RLF) trigger are described. A user equipment (UE) may transmit, to a base station, a random access preamble as part of a contention-based random access procedure. The UE may subsequently monitor a downlink channel for a contention resolution message associated with contention-based random access procedure and may, in some instances, determine a failure to decode the contention resolution message. Here, the UE may update a stored number of instances of contention resolution message failure corresponding to the failure to decode the contention resolution message. The UE may then perform an RLF determination procedure (e.g., to determine whether to trigger an RLF) based on the stored number of instances of contention resolution message failure. For example, the UE may trigger an RLF if the stored number of instances is greater than or equal to a threshold.

Description

FAST RADIO LINK FAILURE TRIGGER

FIELD OF TECHNOLOGY

The following relates generally to wireless communication and more specifically to a fast radio link failure (RLF) trigger.

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) .

Some wireless communications systems may implement radio link management techniques to manage radio link quality in the system. In some instances, a device may determine that a quality of a radio link is poor. Radio link failure may be declared based on the determination, thus triggering a process to establish a better radio link.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support a fast radio link failure (RLF) trigger in wireless systems. Generally, the described techniques provide for a user equipment (UE) to trigger an RLF in a wireless system in a case of persistent decoding failures. More specifically, in cases that a UE initiates a random access channel (RACH) procedure due to a scheduling request failure, the UE may be unable to decode a contention resolution message (e.g., message four of a four-step contention-based RACH procedure) due to, for example, a bit-length mismatch of the contention resolution message. The UE may store the number of instances of the contention resolution message failure (e.g., in a contention resolution message failure counter) and may increment the contention resolution message failure counter each time the UE fails to decode the contention resolution message. If the value of the contention resolution message failure counter exceeds a threshold quantity of contention resolution message decoding failures, the UE may trigger an RLF. The contention resolution message failure counter is different from a preamble transmission counter, which may also be employed to trigger radio link failure based on failure of any random access message failure (not just failure of a message four or contention resolution message) . Because the contention resolution message failure counter may have a lower threshold than that of a preamble transmission counter, RLF may declared faster in cases when RACH failure is due primarily to a message four failure.

A method of wireless communication at a UE is described. The method may include transmitting, to a base station, a random access preamble as part of a contention-based random access procedure, monitoring a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determining a failure to decode the contention resolution message based on monitoring the downlink control channel, updating a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and performing an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit, to a base station, a random access preamble as part of a contention-based random access procedure, monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determine a failure to decode the contention resolution message based on monitoring the downlink control channel, update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for transmitting, to a base station, a random access preamble as part of a contention-based random access procedure, monitoring a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determining a failure to decode the contention resolution message based on monitoring the downlink control channel, updating a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and performing an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to transmit, to a base station, a random access preamble as part of a contention-based random access procedure, monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determine a failure to decode the contention resolution message based on monitoring the downlink control channel, update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

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, a random access response (RAR) message based on transmitting the random access preamble, and transmitting a connection request based on receiving the RAR message, where monitoring the downlink control channel for the contention resolution message may be based on transmitting the connection request.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, updating the stored number of instances of contention resolution message failure may include operations, features, means, or instructions for incrementing a value of a contention resolution message failure counter based on the failure to decode the contention resolution message, where performing the RLF determination may be based on the value of the contention resolution message failure counter.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the RLF determination procedure further may include operations, features, means, or instructions for determining RLF based on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the RLF determination procedure further may include operations, features, means, or instructions for determining that the value of the contention resolution message failure counter may be less than a threshold quantity of contention resolution message decoding failures, and refraining from declaring RLF based on the determination that the value of the contention resolution message failure counter may be less than the threshold quantity.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for incrementing a value of a random access attempt counter based on failure of the contention-based random access procedure, where the random access attempt counter may be different from the contention resolution message failure counter.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for comparing the value of the random access attempt counter with a threshold quantity of random access failures, and determining RLF based on the value of the random access attempt counter exceeding the threshold quantity of random access failures.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for comparing the value of the random access attempt counter with a threshold quantity of random access failures, refraining from declaring RLF based on the value of the random access attempt counter being less than the threshold quantity of random access failures, transmitting, to the base station, an additional random access preamble based on RLF not being declared, incrementing the value of the contention resolution message failure counter based on a failure to decode an additional contention resolution message associated with the additional random access preamble, and performing, again, the RLF determination procedure which may be based, at least in part, on the value of the contention resolution message failure counter.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the RLF determination procedure further may include operations, features, means, or instructions for determining RLF based on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter may be less than a threshold quantity of random access failures.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for setting the value of the contention resolution message failure counter to zero based on a determination of RLF.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a scheduling request failure, where the contention-based random access procedure may be based at least in part in identifying the scheduling request failure.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, identifying the scheduling request failure further may include operations, features, means, or instructions for transmitting a scheduling request to the base station, initiating a timer based on transmitting the scheduling request, determining a failure to receive downlink control information in response to the scheduling request based on an expiration of the timer, incrementing a value of a scheduling request counter based on the failure to receive the downlink control information, and determining that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, where identifying the scheduling request failure may be based on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, monitoring the downlink control channel for the contention resolution message further may include operations, features, means, or instructions for monitoring the downlink control channel for the contention resolution message based on a determined length of a sounding reference signal indicator, where the failure to decode the contention resolution message may be based on the determined length of the sounding reference signal indicator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communication that supports fast radio link failure (RLF) trigger in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a system for wireless communication that supports fast RLF trigger in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow that supports fast RLF trigger in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of a flow chart that supports fast RLF trigger in accordance with aspects of the present disclosure.

FIGs. 5 and 6 show block diagrams of devices that support fast RLF trigger in accordance with aspects of the present disclosure.

FIG. 7 shows a block diagram of a user equipment (UE) coding manager that supports fast RLF trigger in accordance with aspects of the present disclosure.

FIG. 8 shows a diagram of a system including a device that supports fast RLF trigger in accordance with aspects of the present disclosure.

FIGs. 9 through 11 show flowcharts illustrating methods that support fast RLF trigger in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some wireless communications systems, a user equipment (UE) may initiate a random access channel (RACH) procedure with a base station by transmitting a random access preamble to the base station. If the contention-based RACH procedure is successful, the UE may continue to exchange messages with the base station according to the contention-based RACH procedure. But if the contention-based RACH procedure is unsuccessful, the UE may increment a random access attempt counter and initiate the contention-based RACH procedure with the base station again by transmitting a second random access preamble. If the quantity of failed RACH attempts (e.g., indicated by a value stored by the random access attempt counter) exceeds a threshold quantity, the UE may declare radio link failure (RLF) . That is, the UE may perform the threshold quantity of failed RACH attempts prior to declaring an RLF. In one example, the UE may initiate the contention-based RACH procedure after identifying a scheduling request failure. In the example of initiating the contention-based RACH procedure after identifying the scheduling request failure, the UE may be unable to decode a contention resolution message from the base station (e.g., message four of a four-step RACH procedure) . In particular, the scheduling request failure may result in a bit-length mismatch of the contention resolution message resulting in the persistent decoding failure of the contention resolution message.

In some cases, the UE may utilize an additional counter associated with the decoding failure of the contention resolution message failure to trigger an RLF. Here, in the case of a decoding failure of the contention resolution message, the UE may increment a contention resolution message failure counter in addition to incrementing the random access attempt counter. Here, if the number of contention resolution message decoding failures indicated by the contention resolution message failure counter exceeds a threshold number, the UE may determine RLF. In some cases, a value of the threshold associated with the contention resolution message counter may be lower than the value of the random access attempt threshold. Thus, the UE may perform less failed RACH attempts prior to declaring RLF in the case of a persistent decoding failure of the contention resolution message when compared to other failures within the contention-based RACH procedure. Thus, the UE may trigger an RLF faster than cases when the UE does not experience a persistent decoding failure of the contention resolution message. The faster RLF may be implemented to realize one or more advantages. For example, the faster RLF may decrease a quantity of failed RACH attempts thus decreasing interruption time (e.g., resulting in decreased latency) and power consumption.

Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are subsequently described in the context process flows and a flow chart. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to fast radio link failure trigger.

FIG. 1 illustrates an example of a wireless communications system 100 that supports fast RLF trigger 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.

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.

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.

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

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

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

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

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

The wireless communications system 100 may 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.

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) .

In some cases, a UE 115 may initiate a contention-based RACH procedure with a base station 105 by transmitting a random access preamble to the base station 105. If the contention-based RACH procedure is successful, the UE 115 may continue to exchange messages with the base station 105 according to the contention-based RACH procedure. But if the contention-based RACH procedure is unsuccessful, the UE 115 may increment a random access attempt counter and initiate the contention-based RACH procedure with the base station 105 again by transmitting a second random access preamble. If the quantity of failed RACH attempts (e.g., indicated by a value stored by the random access attempt counter) exceeds a threshold quantity, the UE 115 may determine RLF. That is, the UE 115 may perform the threshold quantity of failed RACH attempts prior to declaring an RLF. In one example, the UE 115 may initiate the contention-based RACH procedure after identifying a scheduling request failure. In the example of initiating the contention-based RACH procedure after identifying the scheduling request failure, the UE 115 may be unable to decode a contention resolution message from the base station (e.g., message four) . In particular, the scheduling request failure may result in a bit-length mismatch of the contention resolution message resulting in the persistent decoding failure of the contention resolution message.

In some cases, the UE 115 may utilize an additional counter associated with the decoding failure of the contention resolution message failure to trigger an RLF. Here, in the case of a decoding failure of the contention resolution message, the UE 115 may increment a contention resolution message failure counter in addition to incrementing the random access attempt counter. Here, if the number of contention resolution message decoding failures indicated by the contention resolution message failure counter exceeds a threshold number, the UE 115 may determine RLF. In some cases, a value of the threshold associated with the contention resolution message counter may be lower than the value of the random access attempt threshold. Thus, the UE 115 may perform less failed RACH attempts prior to declaring RLF in the case of a persistent decoding failure of the contention resolution message when compared to other failures within the contention-based RACH procedure. Thus, the UE 115 may trigger an RLF faster than cases when the UE 115 does not experience a persistent decoding failure of the contention resolution message.

FIG. 2 illustrates an example of a wireless communications system 200 that supports fast RLF trigger in accordance with aspects of the present disclosure. In some examples, the wireless communications system 200 may implement aspects of wireless communications system 100 such as base station 105-a and UE 115-a, which may be examples of base stations 105 and UEs 115 as described with reference to FIG. 1.

The UE 115-a may be in communication with the base station 105-a by uplink channel 205 and downlink channel 210. The UE 115-a may transmit one or more scheduling requests 215 to the base station 105-a by the uplink channel 205 requesting an uplink grant. After transmitting each scheduling request 215, the UE 115-a may monitor the downlink channel 210 for the uplink grant (e.g., within downlink control information (DCI) ) . The UE 115-a may initiate a timer after transmitting each the scheduling request 215 and, if the UE 115-a fails to detect the DCI prior to an expiration of the timer, the UE 115-a may determine a failure to receive the DCI and increment a value of a scheduling request counter. For example, after the UE 115-a transmits the scheduling request 215-a, the UE 115-a may initiate the timer and monitor the downlink channel 210 for the DCI. If the UE 115-a fails to detect the DCI prior to the expiration of the timer, the UE 115-a may increment the scheduling request timer to store a value of ‘1, ’ indicating a first failed scheduling request transmission.

The UE 115-a may continue to transmit scheduling requests 215 until a value stored by the scheduling request counter exceeds a threshold quantity of scheduling request transmissions. For example, the UE 115-a may transmit the scheduling request 215-b and monitor the downlink channel 210 for DCI. If the timer expires without the UE 115-a detecting the DCI, the UE 115-a may increment the scheduling request counter. The UE 115-a may compare the value stored by the scheduling request counter and determine that the scheduling request counter exceeds the threshold quantity of scheduling request transmissions indicating a scheduling request failure.

After the scheduling request failure, the UE 115-a may release one or more resources (e.g., physical uplink control channel (PUCCH) resources, sounding reference signal (SRS) resources) and initiate a contention-based RACH procedure (e.g., a random access procedure) with the base station 105-a including one or more RACH messages 220-a sent by the uplink channel 205 and one or more RACH messages 220-b sent by the downlink channel 210. During an execution of the contention-based RACH procedure, the UE 115-a may transmit a random access preamble by the uplink channel 205 to the base station 105-b. Based on receiving the random access preamble, the base station 105-a may transmit a contention resolution message to the UE 115-a by the downlink channel 210. The UE 115-a may monitor the downlink channel 210 for the contention resolution message but may be unable to decode the contention resolution message. For example, there may be a bit-length mismatch of the contention resolution message due to the scheduling request failure. After detecting the failure to decode the contention resolution message, the UE 115-a may increment a contention resolution message failure counter. The UE 115-a may subsequently transmit a second random access preamble within the contention-based RACH messages 220-a to the base station 105-a. Again, the UE 115-a may fail to decode the contention resolution message within the contention-based RACH messages 220-b and thus increment the contention resolution message failure counter. The UE 115-a may continue to transmit a contention-based RACH preambles and, in some cases, fail to decode the contention resolution message until the value indicated by the contention resolution message failure counter exceeds the threshold value of failed contention resolution message failures. When the UE 115-a determines that the value indicated by the contention resolution message failure counter exceeds a threshold, the UE 115-a may determine RLF.

FIG. 3 illustrates an example of a process flow 300 that supports fast RLF trigger in accordance with aspects of the present disclosure. In some examples, the process flow 300 may implement aspects of

wireless communications systems

100 and 200 such as base station 105-b and UE 115-b, which may be examples of base stations 105 and UEs 115 as described with reference to FIGs. 1 and 2. Additionally, the process flow 300 may illustrate communications between the base station 105-b and the UE 115-b as described with reference to FIGs. 1 and 2.

At 305, the base station 105-b may transmit a configuration message (e.g., an RRCReconfiguration message) to the UE 115-b. The configuration message may indicate, to the UE 115-b, a configuration for an SRS. At 310, the UE 115-b may transmit a configuration message response (e.g., an RRCReconfigurationComplete message) to the base station 105-b based on receiving the configuration message at 305.

At 315-a, the UE 115-b may transmit a scheduling request to the base station 105-b (e.g., on a valid PUCCH resource for a scheduling request) . For example, the UE 115-b may determine an arrival of uplink data to be transmitted to the base station 105-b and transmit the scheduling request based on the arrival of the uplink data. After transmitting the scheduling request 315-a, the UE 115-b may initiate a timer (e.g., an sr-ProhibitTimer) after transmitting the scheduling request 315-a. If the UE 115-b fails to detect uplink DCI (e.g., including an uplink grant in response to the scheduling request 315-a) , the UE 115-b may determine a failure to receive or decode the uplink DCI from the base station 105-b. For example, the base station 105-b may not receive the scheduling request 315-a and may therefore not transmit a corresponding uplink DCI including an uplink grant. Thus, the UE 115-b may increment a scheduling request counter (e.g., an SR_COUNTER) storing a value indicating a quantity of transmitted scheduling requests and corresponding uplink DCI receiving or decoding failures. The scheduling request counter may be initialized to store a value of ‘0’ . Thus, after determining a first failure of receiving or decoding a scheduling request, the UE 115-b may increment the scheduling request counter to store a value of ‘1’ . After incrementing the scheduling request counter, the UE 115-b may compare the value stored within the scheduling request counter to a threshold number of scheduling request transmissions (e.g., sr-TransMax) . If the value stored within the scheduling request counter is less than the threshold number of scheduling request transmissions, the UE 115-b may indicate (e.g., by radio resource control (RRC) messaging) to release PUCCH and SRS resources associated with the base station 105-b. The UE 115-b may additionally clear other assignments or resources associated with the base station 105-b (e.g., configured downlink assignments, clear uplink grants, physical uplink shared channel (PUSCH) resources for semi-persistent channel state indicator (CSI) reporting) .

At 325, the UE 115-b may initiate a contention-based RACH procedure (e.g., a random access procedure) and transmit a random access preamble (e.g., message one of the contention-based RACH procedure) to the base station 105-b. Here, the UE 115-b may initiate the contention-based RACH procedure based on identifying the scheduling request failure at 320. At 330, the UE 115-b may receive a random access response (RAR) message (e.g., message two of the contention-based RACH procedure) from the base station 105-b based on transmitting the random access preamble at 325.

At 335, the UE 115-b may transmit a connection request (e.g., message three of the contention-based RACH procedure) to the base station 105-b based on receiving the RAR message at 330. The connection request may include a cell radio network temporary identity (C-RNTI) media access control (MAC) control element (CE) and a base station repeater (BSR) . When the UE 115-b transmits the connection request, the UE 115-b may additionally initiate a timer (e.g., an ra-ContentionResolutionTimer) .

When the base station 105-b receives the connection request at 335, the base station 105-b may be unable to determine that the UE 115-b initiated the contention-based RACH procedure in response to identifying the scheduling request failure at 320. That is, the UE 115-b may include the C-RNTI MAC CE within the connection request for contention-based RACH procedures initiated in response to other conditions. For example, the UE 115-b may include the C-RNTI MAC CE within the connection request for contention-based RACH procedures initiated for beam failure recovery (e.g., in a case that the physical downlink control channel (PDCCH) transmission is addressed to the C-RNTI) . In another example, the UE 115-b may include the C-RNTI MAC CE within the connection request for contention-based RACH procedures initiated by a PDCCH order (e.g., in the case that PDCCH transmission is addressed to the C-RNTI) . In another example, the UE 115-b may include the C-RNTI MAC CE within the connection request for contention-based RACH procedures initiated by the MAC sublayer or by the RRC sublayer (e.g., in the case that the PDCCH transmission is addressed to the C-RNTI and contains an uplink grant for a new transmission) .

At 340, the base station 105-b may transmit a contention resolution message (e.g., message four of the contention-based RACH procedure) to the UE 115-b. For example, the base station 105-b may transmit the contention resolution message by uplink DCI (e.g., UL DCI 0_1) . The contention resolution message may include an SRS resource indicator field (e.g., SRS resource indicator bits) . The SRS resource indicator field may include a number of bits defined based on a value of a higher layer parameter (e.g., a usage parameter or a txConfig parameter of value ‘codeBook’ or ‘nonCodeBook’ ) . For example, when the higher layer parameter is set to a first value (e.g., the ‘codeBook’ value) , the number of bits within the SRS resource indicator field by be defined according to Equation 1, shown below:

Here, N _SRS may be a number of configured SRS resources in the SRS resource set associated with the higher layer parameter. Additionally, L _max may be defined by a higher layer parameter associated with a maximum number of layers supported by the UE 115-b. For example, if the UE 115-b supports operation with a certain number of layers (e.g., maxMIMO-Layers) and the corresponding higher layer parameter (e.g., the maxMIMO-Layers parameters of PUSCH-ServingCellConfig) of the base station 105-b is configured, L _max may be given by the maxMIMO-Layers parameter. Alternatively, L _max may be given by a maximum number of layers for PUSCH supported by the UE 115-b for the base station 105-b for non-codebook based operation.

Additionally or alternatively, when the higher layer parameter (e.g., the txConfig parameter) is set to a second value (e.g., the ‘nonCodeBook’ value) , the number of bits within the SRS resource indicator field by be defined according to Equation 2, shown below:

log ₂ (N _SRS) (2)

In the case that the UE 115-b initiates the contention-based RACH procedure in response to identifying the scheduling request failure, there may be a bit mismatch associated with the SRS resource indicator field (e.g., based on the UE 115-b releasing the SRS resources after identifying the scheduling request failure) . That is, the UE 115-b may attempt to decode the contention resolution message 340 according to a first bit length of the SRS resource indicator field while the actual length of the SRS resource indicator field within the contention resolution message is a second bit length different than the first bit length. Thus, the UE 115-b may be unable to decode the contention resolution message 340.

At 345, the UE 115-b may determine a failure to decode the contention resolution message. That is, at 345 the timer the UE 115-b initiated based on transmitting the connection request may expire. The UE 115-b may monitor a downlink control channel for the contention resolution message from the initiation of the timer to the expiration of the timer. When the timer expires without the UE 115-b detecting the contention resolution message, the UE 115-b may determine a failure to decode the contention resolution message. After determining the failure to decode the contention resolution message, the UE 115-b may increment a value stored by a contention resolution message failure counter (e.g., indicating a number of instances of contention resolution message failure) . The contention resolution message failure counter may be initialized to store a value of ‘0’ . Thus, after determining a first failure of decoding the contention resolution message, the UE 115-b may increment the contention resolution message failure counter to store a value of ‘1’ .

After updating the value stored by the contention resolution message failure counter, the UE 115-b may determine whether to perform an RLF procedure at 350 based on the value stored by the contention resolution message failure counter. That is, the UE 115-b may compare the value stored by the contention resolution message failure counter to a threshold quantity of contention resolution message decoding failures. In some cases, the threshold quantity of contention resolution message decoding failures may be configurable (e.g., set by a higher layer parameter, set based on signaling from the base station 105-b) . If the UE 115-b determines that the value stored by the contention resolution message failure counter is less than the threshold quantity of contention resolution message decoding failures, the UE 115-b may refrain from declaring RLF or performing the RLF procedure. The UE 115-b may then increment a value of a random access attempt counter and determine whether to perform the RLF procedure again based on the value of the random access attempt counter. If the value of the random access attempt counter is less than the threshold quantity of random access failures, the UE 115-b may transmit a random access preamble again and attempt the contention-based RACH procedure again.

Alternatively, if the UE 115-b determines that the value stored by the contention resolution message failure counter is greater than or equal to the threshold quantity of contention resolution message decoding failures, the UE 115-b may determine RLF. In some cases, the magnitude of the threshold quantity of contention resolution message decoding failures may be less than the threshold quantity of random access failures. Thus, if the contention-based RACH procedure fails due to a persistent failure of the UE 115-b decoding the contention resolution message, the UE 115-b may determine RLF prior to a case when the U 115-b only declares RLF when the random access attempt counter exceeds the threshold quantity of random access failures. For example, the UE 115-b may determine an RLF when a value stored by the random access attempt counter is less than the threshold quantity of random access failures because a value stored by the contention resolution failure counter is equal to or greater than the threshold quantity of contention resolution message decoding failures. After the UE 115-b determines the RLF, the UE 115-b may reset the values of the contention resolution failure counter and the random access attempt counter to zero.

FIG. 4 illustrates an example of a flowchart 400 that supports fast RLF trigger in accordance with aspects of the present disclosure. In some examples, the flowchart 400 may implement aspects of FIGs. 1 through 3. For example, the steps of the flowchart 400 may be executed by a UE 115 as described with reference to FIGs. 1 through 3.

At 405, a UE may trigger a contention-based RACH procedure. For example, the UE may detect a scheduling request failure and trigger the contention-based RACH procedure based on detecting the scheduling request failure.

At 410, the UE may transmit a random access preamble to a base station.

At 415, the UE may determine if the contention-based RACH procedure is successful. If the contention-based RACH procedure is successful, the UE may proceed to block 440. Alternatively, when the contention-based RACH procedure is not successful (e.g., in the case of a contention-based RACH failure) , the UE may proceed to block 420.

At 420, the UE may determine if the contention-based RACH failure is due to a contention resolution message (e.g., a message four) failure. If the contention-based RACH failure is not due to a contention resolution message failure, the UE may proceed to block 440. Alternatively, when the contention-based RACH failure is due to a contention resolution message failure, the UE may proceed to block 425.

At 425, the UE may update (e.g., increment) a value stored by the contention resolution message counter.

At 430, the UE may determine whether the value stored by the contention resolution message counter is less than a threshold quantity of contention resolution message decoding failures. If the value stored by the contention resolution message counter is less than the threshold quantity of contention resolution message decoding failures, the UE may proceed to block 440. Alternatively, when the value stored by the contention resolution message counter is greater than or equal to the threshold quantity of contention resolution message decoding failures, the UE may proceed to block 435 and determine RLF.

At block 440, the UE may increment a value of a random access attempt counter and determine whether the value of the random access attempt counter is less than a threshold quantity of random access failures. If the UE determines that the value of the random access attempt counter is less than a threshold quantity of random access failures, the UE may proceed to block 410 and transmit the random access preamble again. Alternatively, if the UE determines that the value of the random access attempt counter is greater than or equal to a threshold quantity of random access failures, the UE may proceed to block 445.

At block 445, the UE may end the contention-based RACH procedure. Here, the UE may determine that the contention-based RACH procedure resulted in a successful contention resolution. The UE may additionally stop a timer associated with the contention-based RACH procedure (e.g., an ra-ContentionResolutionTimer) and discard a temporary C-RNTI.

FIG. 5 shows a block diagram 500 of a device 505 that supports fast RLF trigger in accordance with aspects of the present disclosure. The device 505 may be an example of aspects of a UE 115 as described herein. The device 505 may include a receiver 510, an UE coding manager 515, and a transmitter 520. 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 fast RLF trigger, 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 820 described with reference to FIG. 8. The receiver 510 may utilize a single antenna or a set of antennas.

The UE coding manager 515 may transmit, to a base station, a random access preamble as part of a contention-based random access procedure, monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determine a failure to decode the contention resolution message based on monitoring the downlink control channel, update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure. The UE coding manager 515 may be an example of aspects of the UE coding manager 810 described herein.

The UE coding manager 515, 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 UE coding manager 515, or its sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The UE coding manager 515, 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 UE coding manager 515, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the UE coding manager 515, 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 520 may transmit signals generated by other components of the device 505. In some examples, the transmitter 520 may be collocated with a receiver 510 in a transceiver module. For example, the transmitter 520 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 520 may utilize a single antenna or a set of antennas.

FIG. 6 shows a block diagram 600 of a device 605 that supports fast RLF trigger in accordance with aspects of the present disclosure. The device 605 may be an example of aspects of a device 505, or a UE 115 as described herein. The device 605 may include a receiver 610, an UE coding manager 615, and a transmitter 645. The device 605 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 610 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 fast RLF trigger, etc. ) . Information may be passed on to other components of the device 605. The receiver 610 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The receiver 610 may utilize a single antenna or a set of antennas.

The UE coding manager 615 may be an example of aspects of the UE coding manager 515 as described herein. The UE coding manager 615 may include a random access preamble transmitter 620, a contention resolution message monitorer 625, a decoding failure determiner 630, a failure number storage manager 635, and an RLF manager 640. The UE coding manager 615 may be an example of aspects of the UE coding manager 810 described herein.

The random access preamble transmitter 620 may transmit, to a base station, a random access preamble as part of a contention-based random access procedure.

The contention resolution message monitorer 625 may monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure.

The decoding failure determiner 630 may determine a failure to decode the contention resolution message based on monitoring the downlink control channel.

The failure number storage manager 635 may update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message.

The RLF manager 640 may perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

The transmitter 645 may transmit signals generated by other components of the device 605. In some examples, the transmitter 645 may be collocated with a receiver 610 in a transceiver module. For example, the transmitter 645 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 645 may utilize a single antenna or a set of antennas.

FIG. 7 shows a block diagram 700 of a UE coding manager 705 that supports fast RLF trigger in accordance with aspects of the present disclosure. The UE coding manager 705 may be an example of aspects of a UE coding manager 515, a UE coding manager 615, or a UE coding manager 810 described herein. The UE coding manager 705 may include a random access preamble transmitter 710, a contention resolution message monitorer 715, a decoding failure determiner 720, a failure number storage manager 725, an RLF manager 730, a random access preamble receiver 735, a connection request transmitter 740, and a scheduling request manager 745. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The random access preamble transmitter 710 may transmit, to a base station, a random access preamble as part of a contention-based random access procedure. In some examples, the random access preamble transmitter 710 may transmit, to the base station, an additional random access preamble based on RLF not being declared.

The contention resolution message monitorer 715 may monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure. In some examples, the contention resolution message monitorer 715 may monitor the downlink control channel for the contention resolution message based on a determined length of a sounding reference signal indicator, where the failure to decode the contention resolution message is based on the determined length of the sounding reference signal indicator.

The decoding failure determiner 720 may determine a failure to decode the contention resolution message based on monitoring the downlink control channel.

The failure number storage manager 725 may update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message. In some examples, the failure number storage manager 725 may increment a value of a contention resolution message failure counter based on the failure to decode the contention resolution message, where performing the RLF determination is based on the value of the contention resolution message failure counter. In some cases, the failure number storage manager 725 may increment a value of a random access attempt counter based on failure of the contention-based random access procedure, where the random access attempt counter is different from the contention resolution message failure counter. In some instances, the failure number storage manager 725 may increment the value of the contention resolution message failure counter based on a failure to decode an additional contention resolution message associated with the additional random access preamble. In some examples, the failure number storage manager 725 may set the value of the contention resolution message failure counter to zero based on a determination of RLF.

The RLF manager 730 may perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure. In some examples, the RLF manager 730 may determine RLF based on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures. In some instances, the RLF manager 730 may determine that the value of the contention resolution message failure counter is less than a threshold quantity of contention resolution message decoding failures. In some cases, the RLF manager 730 may refrain from declaring RLF based on the determination that the value of the contention resolution message failure counter is less than the threshold quantity. In some examples, the RLF manager 730 may perform, again, the RLF determination procedure, which is based, at least in part, on the value of the contention resolution message failure counter. In some cases, the RLF manager 730 may determine RLF based on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter is less than a threshold quantity of random access failures.

In some examples, the RLF manager 730 may compare the value of the random access attempt counter with a threshold quantity of random access failures. In some instances, the RLF manager 730 may determine RLF based on the value of the random access attempt counter exceeding the threshold quantity of random access failures. In some cases, the RLF manager 730 may compare the value of the random access attempt counter with a threshold quantity of random access failures. In some examples, the RLF manager 730 may refrain from declaring RLF based on the value of the random access attempt counter being less than the threshold quantity of random access failures.

The random access preamble receiver 735 may receive, from the base station, a RAR message based on transmitting the random access preamble.

The connection request transmitter 740 may transmit a connection request based on receiving the RAR message, where monitoring the downlink control channel for the contention resolution message is based on transmitting the connection request.

The scheduling request manager 745 may identify a scheduling request failure, where the contention-based random access procedure is based at least in part in identifying the scheduling request failure. In some examples, the scheduling request manager 745 may transmit a scheduling request to the base station. In some cases, the scheduling request manager 745 may initiate a timer based on transmitting the scheduling request. In some instances, the scheduling request manager 745 may determine a failure to receive downlink control information in response to the scheduling request based on an expiration of the timer. In some cases, the scheduling request manager 745 may increment a value of a scheduling request counter based on the failure to receive the downlink control information. In some examples, the scheduling request manager 745 may determine that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, where identifying the scheduling request failure is based on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.

FIG. 8 shows a diagram of a system 800 including a device 805 that supports fast RLF trigger in accordance with aspects of the present disclosure. The device 805 may be an example of or include the components of device 505, device 605, or a UE 115 as described herein. The device 805 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including an UE coding manager 810, an I/O controller 815, a transceiver 820, an antenna 825, memory 830, and a processor 840. These components may be in electronic communication via one or more buses (e.g., bus 845) .

The UE coding manager 810 may transmit, to a base station, a random access preamble as part of a contention-based random access procedure, monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure, determine a failure to decode the contention resolution message based on monitoring the downlink control channel, update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message, and perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.

The I/O controller 815 may manage input and output signals for the device 805. The I/O controller 815 may also manage peripherals not integrated into the device 805. In some cases, the I/O controller 815 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 815 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 815 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 815 may be implemented as part of a processor. In some cases, a user may interact with the device 805 via the I/O controller 815 or via hardware components controlled by the I/O controller 815.

The transceiver 820 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 820 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 820 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 825. However, in some cases the device may have more than one antenna 825, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 830 may include random access memory (RAM) and read-only memory (ROM) . The memory 830 may store computer-readable, computer-executable code 835 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 830 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 840 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 840 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 840. The processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks supporting fast RLF trigger) .

The code 835 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communication. The code 835 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 835 may not be directly executable by the processor 840 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 9 shows a flowchart illustrating a method 900 that supports fast RLF trigger in accordance with aspects of the present disclosure. The operations of method 900 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 900 may be performed by a UE coding manager as described with reference to FIGs. 5 through 8. 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 905, the UE may transmit, to a base station, a random access preamble as part of a contention-based random access procedure. The operations of 905 may be performed according to the methods described herein. In some examples, aspects of the operations of 905 may be performed by a random access preamble transmitter as described with reference to FIGs. 5 through 8.

At 910, the UE may monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure. The operations of 910 may be performed according to the methods described herein. In some examples, aspects of the operations of 910 may be performed by a contention resolution message monitorer as described with reference to FIGs. 5 through 8.

At 915, the UE may determine a failure to decode the contention resolution message based on monitoring the downlink control channel. The operations of 915 may be performed according to the methods described herein. In some examples, aspects of the operations of 915 may be performed by a decoding failure determiner as described with reference to FIGs. 5 through 8.

At 920, the UE may update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message. The operations of 920 may be performed according to the methods described herein. In some examples, aspects of the operations of 920 may be performed by a failure number storage manager as described with reference to FIGs. 5 through 8.

At 925, the UE may perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure. The operations of 925 may be performed according to the methods described herein. In some examples, aspects of the operations of 925 may be performed by an RLF manager as described with reference to FIGs. 5 through 8.

FIG. 10 shows a flowchart illustrating a method 1000 that supports fast RLF trigger in accordance with aspects of the present disclosure. The operations of method 1000 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1000 may be performed by a UE coding manager as described with reference to FIGs. 5 through 8. 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 1005, the UE may transmit, to a base station, a random access preamble as part of a contention-based random access procedure. The operations of 1005 may be performed according to the methods described herein. In some examples, aspects of the operations of 1005 may be performed by a random access preamble transmitter as described with reference to FIGs. 5 through 8.

At 1010, the UE may monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure. The operations of 1010 may be performed according to the methods described herein. In some examples, aspects of the operations of 1010 may be performed by a contention resolution message monitorer as described with reference to FIGs. 5 through 8.

At 1015, the UE may determine a failure to decode the contention resolution message based on monitoring the downlink control channel. The operations of 1015 may be performed according to the methods described herein. In some examples, aspects of the operations of 1015 may be performed by a decoding failure determiner as described with reference to FIGs. 5 through 8.

At 1020, the UE may increment a value of a contention resolution message failure counter based on the failure to decode the contention resolution message. The operations of 1020 may be performed according to the methods described herein. In some examples, aspects of the operations of 1020 may be performed by a failure number storage manager as described with reference to FIGs. 5 through 8.

At 1025, the UE may determine RLF based on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures. The operations of 1025 may be performed according to the methods described herein. In some examples, aspects of the operations of 1025 may be performed by an RLF manager as described with reference to FIGs. 5 through 8.

FIG. 11 shows a flowchart illustrating a method 1100 that supports fast RLF trigger in accordance with aspects of the present disclosure. The operations of method 1100 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1100 may be performed by a UE coding manager as described with reference to FIGs. 5 through 8. 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 1105, the UE may transmit, to a base station, a random access preamble as part of a contention-based random access procedure. The operations of 1105 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be performed by a random access preamble transmitter as described with reference to FIGs. 5 through 8.

At 1110, the UE may receive, from the base station, a RAR message based on transmitting the random access preamble. The operations of 1110 may be performed according to the methods described herein. In some examples, aspects of the operations of 1110 may be performed by a random access preamble receiver as described with reference to FIGs. 5 through 8.

At 1115, the UE may transmit a connection request based on receiving the RAR message, where monitoring the downlink control channel for the contention resolution message is based on transmitting the connection request. The operations of 1115 may be performed according to the methods described herein. In some examples, aspects of the operations of 1115 may be performed by a connection request transmitter as described with reference to FIGs. 5 through 8.

At 1120, the UE may monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure. The operations of 1120 may be performed according to the methods described herein. In some examples, aspects of the operations of 1120 may be performed by a contention resolution message monitorer as described with reference to FIGs. 5 through 8.

At 1125, the UE may determine a failure to decode the contention resolution message based on monitoring the downlink control channel. The operations of 1125 may be performed according to the methods described herein. In some examples, aspects of the operations of 1125 may be performed by a decoding failure determiner as described with reference to FIGs. 5 through 8.

At 1130, the UE may update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message. The operations of 1130 may be performed according to the methods described herein. In some examples, aspects of the operations of 1130 may be performed by a failure number storage manager as described with reference to FIGs. 5 through 8.

At 1135, the UE may perform an RLF determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure. The operations of 1135 may be performed according to the methods described herein. In some examples, aspects of the operations of 1135 may be performed by an RLF manager as described with reference to FIGs. 5 through 8.

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

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

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

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

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

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

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

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

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

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

Claims

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

transmitting, to a base station, a random access preamble as part of a contention-based random access procedure;

monitoring a downlink control channel for a contention resolution message associated with the contention-based random access procedure;

determining a failure to decode the contention resolution message based at least in part on monitoring the downlink control channel;

updating a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message; and

performing a radio link failure determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.
The method of claim 1, further comprising:

identifying a scheduling request failure, wherein the contention-based random access procedure is based at least in part in identifying the scheduling request failure.
The method of claim 2, wherein identifying the scheduling request failure further comprises:

transmitting a scheduling request to the base station;

initiating a timer based at least in part on transmitting the scheduling request;

determining a failure to receive downlink control information in response to the scheduling request based at least in part on an expiration of the timer;

incrementing a value of a scheduling request counter based at least in part on the failure to receive the downlink control information; and

determining that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, wherein identifying the scheduling request failure is based at least in part on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.
The method of claim 1, wherein monitoring the downlink control channel for the contention resolution message further comprises:

monitoring the downlink control channel for the contention resolution message based at least in part on a determined length of a sounding reference signal indicator, wherein the failure to decode the contention resolution message is based at least in part on the determined length of the sounding reference signal indicator.
The method of claim 1, further comprising:

receiving, from the base station, a random access response message based at least in part on transmitting the random access preamble; and

transmitting a connection request based at least in part on receiving the random access response message, wherein monitoring the downlink control channel for the contention resolution message is based at least in part on transmitting the connection request.
The method of claim 1, wherein updating the stored number of instances of contention resolution message failure comprises:

incrementing a value of a contention resolution message failure counter based at least in part on the failure to decode the contention resolution message, wherein performing the radio link failure determination is based at least in part on the value of the contention resolution message failure counter.
The method of claim 6, wherein performing the radio link failure determination procedure further comprises:

determining radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures.
The method of claim 6, wherein performing the radio link failure determination procedure further comprises:

determining that the value of the contention resolution message failure counter is less than a threshold quantity of contention resolution message decoding failures; and

refraining from declaring radio link failure based at least in part on the determination that the value of the contention resolution message failure counter is less than the threshold quantity.
The method of claim 8, further comprising:

incrementing a value of a random access attempt counter based at least in part on failure of the contention-based random access procedure, wherein the random access attempt counter is different from the contention resolution message failure counter.
The method of claim 9, further comprising:

comparing the value of the random access attempt counter with a threshold quantity of random access failures; and

determining radio link failure based at least in part on the value of the random access attempt counter exceeding the threshold quantity of random access failures.
The method of claim 9, further comprising:

comparing the value of the random access attempt counter with a threshold quantity of random access failures;

refraining from declaring radio link failure based at least in part on the value of the random access attempt counter being less than the threshold quantity of random access failures;

transmitting, to the base station, an additional random access preamble based at least in part on radio link failure not being declared;

incrementing the value of the contention resolution message failure counter based at least in part on a failure to decode an additional contention resolution message associated with the additional random access preamble; and

performing, again, the radio link failure determination procedure which is based, at least in part, on the value of the contention resolution message failure counter.
The method of claim 6, wherein performing the radio link failure determination procedure further comprises:

determining radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter is less than a threshold quantity of random access failures.
The method of claim 6, further comprising:

setting the value of the contention resolution message failure counter to zero based at least in part on a determination of radio link failure.
An apparatus for wireless communication at a user equipment (UE) , comprising:

a processor,

memory coupled with the processor; and

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

transmit, to a base station, a random access preamble as part of a contention-based random access procedure;

monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure;

determine a failure to decode the contention resolution message based at least in part on monitoring the downlink control channel;

update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message; and

perform a radio link failure determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.
The apparatus of claim 14, wherein the instructions are further executable by the processor to cause the apparatus to:

identify a scheduling request failure, wherein the contention-based random access procedure is based at least in part in identifying the scheduling request failure.
The apparatus of claim 15, wherein the instructions to identify the scheduling request failure further are executable by the processor to cause the apparatus to:

transmit a scheduling request to the base station;

initiate a timer based at least in part on transmitting the scheduling request;

determine a failure to receive downlink control information in response to the scheduling request based at least in part on an expiration of the timer;

increment a value of a scheduling request counter based at least in part on the failure to receive the downlink control information; and

determine that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, wherein identifying the scheduling request failure is based at least in part on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.
The apparatus of claim 14, wherein the instructions to monitor the downlink control channel for the contention resolution message further are executable by the processor to cause the apparatus to:

monitor the downlink control channel for the contention resolution message based at least in part on a determined length of a sounding reference signal indicator, wherein the failure to decode the contention resolution message is based at least in part on the determined length of the sounding reference signal indicator.
The apparatus of claim 14, wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from the base station, a random access response message based at least in part on transmitting the random access preamble; and

transmit a connection request based at least in part on receiving the random access response message, wherein monitoring the downlink control channel for the contention resolution message is based at least in part on transmitting the connection request.
The apparatus of claim 14, wherein the instructions to update the stored number of instances of contention resolution message failure are executable by the processor to cause the apparatus to:

increment a value of a contention resolution message failure counter based at least in part on the failure to decode the contention resolution message, wherein performing the radio link failure determination is based at least in part on the value of the contention resolution message failure counter.
The apparatus of claim 19, wherein the instructions to perform the radio link failure determination procedure further are executable by the processor to cause the apparatus to:

determine radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures.
The apparatus of claim 19, wherein the instructions to perform the radio link failure determination procedure further are executable by the processor to cause the apparatus to:

determine that the value of the contention resolution message failure counter is less than a threshold quantity of contention resolution message decoding failures; and

refrain from declaring radio link failure based at least in part on the determination that the value of the contention resolution message failure counter is less than the threshold quantity.
The apparatus of claim 21, wherein the instructions are further executable by the processor to cause the apparatus to:

increment a value of a random access attempt counter based at least in part on failure of the contention-based random access procedure, wherein the random access attempt counter is different from the contention resolution message failure counter.
The apparatus of claim 22, wherein the instructions are further executable by the processor to cause the apparatus to:

compare the value of the random access attempt counter with a threshold quantity of random access failures; and

determine radio link failure based at least in part on the value of the random access attempt counter exceeding the threshold quantity of random access failures.
The apparatus of claim 22, wherein the instructions are further executable by the processor to cause the apparatus to:

compare the value of the random access attempt counter with a threshold quantity of random access failures;

refrain from declaring radio link failure based at least in part on the value of the random access attempt counter being less than the threshold quantity of random access failures;

transmit, to the base station, an additional random access preamble based at least in part on radio link failure not being declared;

increment the value of the contention resolution message failure counter based at least in part on a failure to decode an additional contention resolution message associated with the additional random access preamble; and

perform, again, the radio link failure determination procedure which is based, at least in part, on the value of the contention resolution message failure counter.
The apparatus of claim 19, wherein the instructions to perform the radio link failure determination procedure further are executable by the processor to cause the apparatus to:

determine radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter is less than a threshold quantity of random access failures.
The apparatus of claim 19, wherein the instructions are further executable by the processor to cause the apparatus to:

set the value of the contention resolution message failure counter to zero based at least in part on a determination of radio link failure.
An apparatus for wireless communication at a user equipment (UE) , comprising:

means for transmitting, to a base station, a random access preamble as part of a contention-based random access procedure;

means for monitoring a downlink control channel for a contention resolution message associated with the contention-based random access procedure;

means for determining a failure to decode the contention resolution message based at least in part on monitoring the downlink control channel;

means for updating a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message; and

means for performing a radio link failure determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.
The apparatus of claim 27, further comprising:

means for identifying a scheduling request failure, wherein the contention-based random access procedure is based at least in part in identifying the scheduling request failure.
The apparatus of claim 28, wherein the means for identifying the scheduling request failure further comprises:

means for transmitting a scheduling request to the base station;

means for initiating a timer based at least in part on transmitting the scheduling request;

means for determining a failure to receive downlink control information in response to the scheduling request based at least in part on an expiration of the timer;

means for incrementing a value of a scheduling request counter based at least in part on the failure to receive the downlink control information; and

means for determining that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, wherein identifying the scheduling request failure is based at least in part on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.
The apparatus of claim 27, wherein the means for monitoring the downlink control channel for the contention resolution message further comprises:

means for monitoring the downlink control channel for the contention resolution message based at least in part on a determined length of a sounding reference signal indicator, wherein the failure to decode the contention resolution message is based at least in part on the determined length of the sounding reference signal indicator.
The apparatus of claim 27, further comprising:

means for receiving, from the base station, a random access response message based at least in part on transmitting the random access preamble; and

means for transmitting a connection request based at least in part on receiving the random access response message, wherein monitoring the downlink control channel for the contention resolution message is based at least in part on transmitting the connection request.
The apparatus of claim 27, wherein the means for updating the stored number of instances of contention resolution message failure comprises:

means for incrementing a value of a contention resolution message failure counter based at least in part on the failure to decode the contention resolution message, wherein performing the radio link failure determination is based at least in part on the value of the contention resolution message failure counter.
The apparatus of claim 32, wherein the means for performing the radio link failure determination procedure further comprises:

means for determining radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures.
The apparatus of claim 32, wherein the means for performing the radio link failure determination procedure further comprises:

means for determining that the value of the contention resolution message failure counter is less than a threshold quantity of contention resolution message decoding failures; and

means for refraining from declaring radio link failure based at least in part on the determination that the value of the contention resolution message failure counter is less than the threshold quantity.
The apparatus of claim 34, further comprising:

means for incrementing a value of a random access attempt counter based at least in part on failure of the contention-based random access procedure, wherein the random access attempt counter is different from the contention resolution message failure counter.
The apparatus of claim 35, further comprising:

means for comparing the value of the random access attempt counter with a threshold quantity of random access failures; and

means for determining radio link failure based at least in part on the value of the random access attempt counter exceeding the threshold quantity of random access failures.
The apparatus of claim 35, further comprising:

means for comparing the value of the random access attempt counter with a threshold quantity of random access failures;

means for refraining from declaring radio link failure based at least in part on the value of the random access attempt counter being less than the threshold quantity of random access failures;

means for transmitting, to the base station, an additional random access preamble based at least in part on radio link failure not being declared;

means for incrementing the value of the contention resolution message failure counter based at least in part on a failure to decode an additional contention resolution message associated with the additional random access preamble; and

means for performing, again, the radio link failure determination procedure which is based, at least in part, on the value of the contention resolution message failure counter.
The apparatus of claim 32, wherein the means for performing the radio link failure determination procedure further comprises:

means for determining radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter is less than a threshold quantity of random access failures.
The apparatus of claim 32, further comprising:

means for setting the value of the contention resolution message failure counter to zero based at least in part on a determination of radio link failure.
A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE) , the code comprising instructions executable by a processor to:

transmit, to a base station, a random access preamble as part of a contention-based random access procedure;

monitor a downlink control channel for a contention resolution message associated with the contention-based random access procedure;

determine a failure to decode the contention resolution message based at least in part on monitoring the downlink control channel;

update a stored number of instances of contention resolution message failure based on determination of the failure to decode the contention resolution message; and

perform a radio link failure determination procedure which is based, at least in part, on the stored number of instances of contention resolution message failure.
The non-transitory computer-readable medium of claim 40, wherein the instructions are further executable to:

identify a scheduling request failure, wherein the contention-based random access procedure is based at least in part in identifying the scheduling request failure.
The non-transitory computer-readable medium of claim 41, wherein the instructions to identify the scheduling request failure further are executable to:

transmit a scheduling request to the base station;

initiate a timer based at least in part on transmitting the scheduling request;

determine a failure to receive downlink control information in response to the scheduling request based at least in part on an expiration of the timer;

increment a value of a scheduling request counter based at least in part on the failure to receive the downlink control information; and

determine that the value of the scheduling request counter exceeds a threshold quantity of scheduling request transmissions, wherein identifying the scheduling request failure is based at least in part on determining that the value of the scheduling request counter exceeds the threshold quantity of scheduling request transmissions.
The non-transitory computer-readable medium of claim 40, wherein the instructions to monitor the downlink control channel for the contention resolution message further are executable to:

monitor the downlink control channel for the contention resolution message based at least in part on a determined length of a sounding reference signal indicator, wherein the failure to decode the contention resolution message is based at least in part on the determined length of the sounding reference signal indicator.
The non-transitory computer-readable medium of claim 40, wherein the instructions are further executable to:

receive, from the base station, a random access response message based at least in part on transmitting the random access preamble; and

transmit a connection request based at least in part on receiving the random access response message, wherein monitoring the downlink control channel for the contention resolution message is based at least in part on transmitting the connection request.
The non-transitory computer-readable medium of claim 40, wherein the instructions to update the stored number of instances of contention resolution message failure are executable to:

increment a value of a contention resolution message failure counter based at least in part on the failure to decode the contention resolution message, wherein performing the radio link failure determination is based at least in part on the value of the contention resolution message failure counter.
The non-transitory computer-readable medium of claim 45, wherein the instructions to perform the radio link failure determination procedure further are executable to:

determine radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures.
The non-transitory computer-readable medium of claim 45, wherein the instructions to perform the radio link failure determination procedure further are executable to:

determine that the value of the contention resolution message failure counter is less than a threshold quantity of contention resolution message decoding failures; and

refrain from declaring radio link failure based at least in part on the determination that the value of the contention resolution message failure counter is less than the threshold quantity.
The non-transitory computer-readable medium of claim 47, wherein the instructions are further executable to:

increment a value of a random access attempt counter based at least in part on failure of the contention-based random access procedure, wherein the random access attempt counter is different from the contention resolution message failure counter.
The non-transitory computer-readable medium of claim 48, wherein the instructions are further executable to:

compare the value of the random access attempt counter with a threshold quantity of random access failures; and

determine radio link failure based at least in part on the value of the random access attempt counter exceeding the threshold quantity of random access failures.
The non-transitory computer-readable medium of claim 48, wherein the instructions are further executable to:

compare the value of the random access attempt counter with a threshold quantity of random access failures;

refrain from declaring radio link failure based at least in part on the value of the random access attempt counter being less than the threshold quantity of random access failures;

transmit, to the base station, an additional random access preamble based at least in part on radio link failure not being declared;

increment the value of the contention resolution message failure counter based at least in part on a failure to decode an additional contention resolution message associated with the additional random access preamble; and

perform, again, the radio link failure determination procedure which is based, at least in part, on the value of the contention resolution message failure counter.
The non-transitory computer-readable medium of claim 45, wherein the instructions to perform the radio link failure determination procedure further are executable to:

determine radio link failure based at least in part on the value of the contention resolution message failure counter exceeding a threshold quantity of contention resolution message decoding failures while a value of a random access attempt counter is less than a threshold quantity of random access failures.
The non-transitory computer-readable medium of claim 45, wherein the instructions are further executable to:

set the value of the contention resolution message failure counter to zero based at least in part on a determination of radio link failure.