Unicast link radio link failure detection and management

Abstract

Methods, systems, and devices for wireless communications are described. A first user equipment (UE) may establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a plurality of streams. The first UE may determine a radio link state of the sidelink connection based on monitoring each of the plurality of streams. The first UE may, based on the determination, send a non-access stratum layer message to the second UE based at least on the radio link state of the sidelink connection.

Description

[0001] Cross-references

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 951,771, entitled “Unicast LinkRadio Link Failure Detection and Management,” filed by Cheng et al. on December 20, 2019, and U.S. Patent Application No. 17 / 118,806, entitled “Unicast Link Radio Link Failure Detection and Management,” filed by Cheng et al. on December 11, 2020; each of which is assigned to the present assignee. Technical Field

[0003] The following relates generally to wireless communications and, more particularly, to unicast link radio link failure (RLF) detection and management. Background Art

[0004] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcast, etc. These systems may be able to support communication with multiple users by sharing 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 use techniques 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 communication system may include multiple base stations or network access nodes, each of which simultaneously supports communication with multiple communication devices, which may be referred to as user equipment (UE). Summary of the invention

[0005] The described technology relates to improved methods, systems, devices and apparatuses for supporting unicast link radio link failure (RLF) detection and management. In general, the described technology provides various mechanisms for supporting wireless communication in a wireless network. Broadly speaking, various aspects of the described technology implement radio link management (RLM) / radio link failure (RLF) detection on a side link channel. For example, two user equipments (UEs) can communicate on a side link channel. A side link connection may include multiple streams for data communication between UEs. A stream generally refers to data communicated by separate data radio bearers (DRBs) with different quality of service (QoS) requirements, etc. Each UE may monitor the communication on each stream separately to determine the radio link state of the side link connection. For example, each UE may monitor confirmation messages associated with communications performed on each stream, may monitor the amount of data communicated on each stream according to a time period, or may otherwise determine whether the data is communicated on each stream in an acceptable manner and meets the associated QoS requirements. The UE may exchange non-access stratum (NAS) layer messages and / or access stratum (AS) messages based on the radio link state of the side link connection. For example, the UE may determine that at least one of the flows has no data being communicated, such as based on a lack of an acknowledgement message, based on an inactivity timer, based on a failure to meet QoS requirements of the flows, and the like.

[0006] Typically, the lack of data communicated on a stream may trigger concerns that the sidelink channel has degraded below an acceptable performance level and / or has degraded (e.g., is experiencing RLF). Therefore, rather than simply declaring RLF, the UE may determine whether data is being communicated through (multiple) other streams of the sidelink connection. If data is being communicated through at least one other stream of the sidelink connection, this may indicate that the sidelink connection has not failed, but may have degraded to a certain extent, so various parameters of the sidelink channel may be updated. In this case, the UE may send a message (e.g., a NAS message and / or an AS message) to another UE that updates or otherwise reconfigures the parameters for the sidelink connection, such as updating QoS parameters, selecting a new configuration for the sidelink connection, etc. If the UE determines that no data is being communicated through (multiple) other streams, this may indicate that the sidelink connection has failed and / or has degraded more significantly. In this case, the UE may send a keep-alive message to the other UE over a sidelink channel (e.g., using a signaling radio bearer (SRB) and / or one or more DRBs of the sidelink connection) to request confirmation that the sidelink connection is active. If the response to the keep-alive message indicates that the side link connection is active, the UE may resolve the lack of communication on the particular flow and / or send a message (e.g., a NAS and / or AS message) to the other UE to reconfigure various parameters of the side link connection. If no response to the keep-alive message is received from the other UE, the UE may determine that the side link connection has failed, and therefore disconnect the connection and begin an RLF recovery process. These techniques improve link management of side link connections between UEs, avoid unnecessary RLF declarations (e.g., unnecessarily disconnecting a side link connection and having to reestablish a new side link connection), etc.

[0007] A method of wireless communication at a first UE is described. The method may include establishing a sidelink connection with a second UE, wherein the sidelink connection is associated with a set of flows, determining a radio link state of the sidelink connection based on monitoring each flow of the set of flows, and based on the determination, sending a non-access stratum layer message to the second UE based at least on the radio link state of the sidelink connection.

[0008] An apparatus for wireless communication at a first UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a set of flows, determine a radio link state of the sidelink connection based on monitoring each flow of the set of flows, and based on the determination, send a non-access stratum layer message to the second UE based at least on the radio link state of the sidelink connection.

[0009] Another apparatus for wireless communication at a first UE is described. The apparatus may include means for establishing a sidelink connection with a second UE (wherein the sidelink connection is associated with a set of flows), determining a radio link state of the sidelink connection based on monitoring each flow of the set of flows, and sending a non-access stratum layer message to the second UE based on determining at least the radio link state of the sidelink connection.

[0010] A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor to establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a set of flows, determine a radio link state of the sidelink connection based on monitoring each flow of the set of flows, and based on the determination, send a non-access stratum layer message to the second UE based at least on the radio link state of the sidelink connection.

[0011] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for determining that no data can be communicated via a first flow of the flow set, and sending a non-access stratum layer message to a second UE, wherein the non-access stratum layer message includes a keep-alive message requesting confirmation from the second UE that a radio link state of the sidelink connection may be active.

[0012] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for receiving a response message from a second UE indicating that a radio link state of a sidelink connection with the second UE may be active, and sending a second message to the second UE to reconfigure one or more parameters of the sidelink connection based on the response message.

[0013] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of a side link connection may include operations, features, components, or instructions for reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection.

[0014] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of the side link connection may include operations, features, components, or instructions for reconfiguring one or more quality of service parameters configured for the side link connection.

[0015] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for determining that a radio link state of a side link connection with a second UE includes a radio link failure based on a lack of a response message from the second UE, and performing a radio link failure recovery process based on the radio link failure to establish a second side link connection with the second UE.

[0016] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, determining that no data may be communicated may include operations, features, components, or instructions for determining that data communicated via the first flow fails to meet quality of service requirements associated with the first flow.

[0017] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, determining that no data may have been communicated may include operations, features, components, or instructions for determining that no data may have been communicated over the first flow within a threshold time period associated with the first flow.

[0018] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for determining that no data can be communicated via a first stream of a stream set, determining that data can be communicated via a second stream of a stream set, determining that a radio link state of the sidelink connection includes a degraded radio link state, and sending a second message to a second UE to reconfigure one or more parameters of the sidelink connection.

[0019] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of a side link connection may include operations, features, components, or instructions for reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection.

[0020] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of the side link connection may include operations, features, components, or instructions for reconfiguring one or more quality of service parameters configured for the side link connection.

[0021] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for determining that a non-access stratum layer message is sent within a threshold time period, and avoiding sending a second non-access stratum layer message to a second UE based at least on the non-access stratum layer message.

[0022] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, determining a radio link state of a sidelink connection may include operations, features, components, or instructions for determining, for each flow in a set of flows, whether data communicated through each flow meets a quality of service requirement configured for the flow.

[0023] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the non-access stratum layer message includes a PC5 sidelink (PC5-S) message.

[0024] A method of wireless communication at a second UE is described. The method may include establishing a sidelink connection with a first UE, wherein the sidelink connection is associated with a set of flows, receiving a non-access stratum layer message from the first UE indicating a radio link state of the sidelink connection, wherein the non-access stratum layer message is based on a state of each flow of the set of flows at the first UE, and sending a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active.

[0025] An apparatus for wireless communication at a second UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to establish a sidelink connection with a first UE, wherein the sidelink connection is associated with a stream set, receive a non-access stratum layer message from the first UE indicating a radio link state of the sidelink connection, wherein the non-access stratum layer message is based on a state of each stream of the stream set at the first UE, and send a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active.

[0026] Another apparatus for wireless communication at a second UE is described. The apparatus may include means for establishing a sidelink connection with a first UE (wherein the sidelink connection is associated with a set of flows), receiving a non-access stratum layer message from the first UE indicating a radio link state of the sidelink connection (wherein the non-access stratum layer message is based on a state of each flow of the set of flows at the first UE), and sending a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active.

[0027] A non-transitory computer-readable medium storing code for wireless communication at a second UE is described. The code may include instructions executable by a processor to establish a sidelink connection with a first UE, wherein the sidelink connection is associated with a set of flows, receive a non-access stratum layer message from the first UE indicating a radio link state of the sidelink connection, wherein the non-access stratum layer message is based on a state of each flow of the set of flows at the first UE, and send a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active.

[0028] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for receiving a second message from the first UE based on the response message, the second message reconfiguring one or more parameters of the side link connection, and reconfiguring one or more parameters of the side link connection based at least in part on the second message.

[0029] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of a side link connection may include operations, features, components, or instructions for reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection.

[0030] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, reconfiguring one or more parameters of the side link connection may include operations, features, components, or instructions for reconfiguring one or more quality of service parameters configured for the side link connection.

[0031] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the non-access stratum layer message includes a keep-alive message requesting confirmation from the second UE that a radio link state of the sidelink connection may be active. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 An example of a wireless communication system supporting unicast link radio link failure (RLF) detection and management according to aspects of the present disclosure is shown.

[0033] Figure 2 An example of a wireless communication system supporting unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0034] Figure 3 An example of a process that supports unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0035] Figure 4 An example of a process that supports unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0036] Figure 5 An example of a process that supports unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0037] Figure 6 and Figure 7 A block diagram of a device supporting unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0038] Figure 8A block diagram of a communications manager supporting unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0039] Fig. 9 A diagram of a system including devices supporting unicast link RLF detection and management according to aspects of the present disclosure is shown.

[0040] Figures 10 to 14 A flow chart illustrating a method of supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0041] Wireless communication systems may use different interfaces to support wireless communication between devices. For example, the Uu interface may be used to support wireless communication between a base station and a user equipment (UE). The PC5 interface may be used to support wireless communication between UEs. Each interface type is unique in terms of configuration, requirements, and the like. For example, two UEs may establish a side link connection through a PC5 interface that supports multiple streams. A stream generally refers to data communicated through a separate data radio bearer (DRB), data communicated with different quality of service (QoS) requirements, and the like. Some wireless communication systems are configured so that no access stratum (AS) layer signaling is available for radio link management (RLM) / radio link failure (RLF). In addition, such wireless communication systems may also be configured so that there is no receiver-side lower layer indication of RLF support. Therefore, this may result in the UE communicating on the side link channel without an effective or efficient means to manage the side link connection. In some aspects, this may mean that the UE unnecessarily declares RLF for the side link connection when the link is still active but may have been degraded to some extent. Unnecessarily declaring RLF means wasting a lot of resources and time to disconnect the side link connection and then reestablish a new side link connection.

[0042] Aspects of the present disclosure are initially described in the context of a wireless communication system. Broadly speaking, various aspects of the technology implement RLM / RLF detection on a sidelink channel. For example, two UEs may communicate on a sidelink channel. A sidelink connection may include multiple streams for data communication between UEs. A stream generally refers to data communicated through separate DRBs with different QoS requirements, etc. Each UE may monitor the communication on each stream separately to determine the radio link state of the sidelink connection. For example, each UE may monitor confirmation messages associated with communications performed on each stream, may monitor the amount of data communicated on each stream according to a time period, or may otherwise determine whether the data is communicated on each stream in an acceptable manner and meets the associated QoS requirements. The UE may exchange NAS layer messages and / or AS messages based on the radio link state of the sidelink connection. For example, the UE may determine that at least one of the streams has no data being communicated, for example based on the lack of a confirmation message, based on an inactive timer, based on failure to meet the QoS requirements of the stream, etc.

[0043] Typically, the lack of data communicated on a stream may trigger concerns that the sidelink channel has degraded below an acceptable performance level and / or has degraded (e.g., is experiencing RLF). Therefore, rather than simply declaring RLF, the UE may determine whether data is being communicated through other streams (multiple) of the sidelink connection. If data is being communicated, this may indicate that the sidelink connection may have degraded to a certain extent, so various parameters of the sidelink channel may be updated. In this case, the UE may send a message (e.g., a NAS message and / or an AS message) to another UE that updates or otherwise reconfigures the parameters for the sidelink connection, such as updating QoS parameters, selecting a new configuration for the sidelink connection, etc. In other cases, if data is being communicated through other streams (multiple) of the sidelink connection, the link may be operating correctly, and the alarm may be due to a lack of application layer data to be sent for that particular stream. If the UE determines that no data is being communicated through other streams (multiple), this may indicate that the sidelink connection has failed and / or degraded more significantly. In this case, the UE may send a keep-alive message to other UEs over a sidelink channel (e.g., using a signaling radio bearer (SRB) and / or one or more DRBs of the sidelink connection) to request confirmation that the sidelink connection is active. If a response to the keep-alive message indicates that the sidelink connection is active, the UE may resolve the lack of communication on a particular stream and / or send a message (e.g., a NAS and / or AS message) to other UEs to reconfigure various parameters of the sidelink connection. If no response to the keep-alive message is received from the other UEs, the UE may determine that the sidelink connection has failed and therefore disconnect the connection and begin an RLF recovery process. These techniques improve link management of sidelink connections between UEs, avoid unnecessary RLF declarations (e.g., unnecessarily disconnecting a sidelink connection and having to reestablish a new sidelink connection), and the like.

[0044] Aspects of the present disclosure are further illustrated and described by reference to apparatus diagrams, system diagrams, and flow diagrams related to unicast link RLF detection and management.

[0045] Figure 1 An example of a wireless communication system 100 supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The wireless communication system 100 includes a base station 105, a UE 115, and a core network 130. In some examples, the wireless communication 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 cases, the wireless communication system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission-critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

[0046] The base station 105 may communicate wirelessly with the UE 115 via one or more base station antennas. The base station 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a Node B, an eNode B (eNB), a next generation Node B or a Gigabit Node B (any of which may be referred to as a gNB), a Home Node B, a Home eNode B, or some other suitable terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macro or small cell base stations). The UE 115 described herein may be able to communicate with various types of base stations 105 and network devices including macro eNBs, small cell eNBs, gNBs, relay base stations, etc.

[0047] Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 are supported. Each base station 105 may provide communications coverage for the respective geographic coverage area 110 via a communications link 125, and the communications link 125 between the base station 105 and the UE 115 may utilize one or more carriers. The communications link 125 shown in the wireless communication system 100 may include an uplink transmission from the UE 115 to the base station 105, or a downlink transmission from the base station 105 to the UE 115. Downlink transmissions may also be referred to as forward link transmissions, and uplink transmissions may also be referred to as reverse link transmissions.

[0048] The geographic coverage area 110 of the base station 105 can be divided into sectors that constitute a portion of the geographic coverage area 110, and each sector can be associated with a cell. For example, each base station 105 can provide communication coverage for a macro cell, a small cell, a hotspot, or other types of cells, or various combinations thereof. In some examples, the base station 105 can be mobile, thereby providing communication coverage for a mobile geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies can overlap, and overlapping geographic coverage areas 110 associated with different technologies can be supported by the same base station 105 or different base stations 105. The wireless communication system 100 may include, for example, a heterogeneous LTE / LTE-A / LTE-A Pro or NR network, in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

[0049] The term "cell" refers to a logical communication entity for communicating with a base station 105 (e.g., via a carrier), and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) for distinguishing adjacent cells operating via the same or different carriers. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types that may provide access to different types of devices (e.g., machine type communication (MTC), narrowband Internet of Things (NB-IoT), enhanced mobile broadband (eMBB), or other). In some cases, the term "cell" may refer to a portion of a geographic coverage area 110 (e.g., a sector) on which the logical entity operates.

[0050] UE 115 can be dispersed throughout the wireless communication system 100, and each UE 115 can be stationary or mobile. UE 115 can also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where "device" can also be referred to as a unit, a station, a terminal, or a client. UE 115 can also be a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, UE 115 can also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, etc., which can be implemented in various items such as household appliances, vehicles, meters, etc.

[0051] Some UEs 115, such as MTC or IoT devices, may be low-cost or low-complexity devices and may provide automatic communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC may refer to data communication technology that allows devices to communicate with each other or with a base station 105 without human intervention. In some examples, M2M communication or MTC may include communication from devices that integrate sensors or meters to measure or capture information and relay the information to a central server or application that may utilize the information or present the information to a person interacting with the program or application. Some UEs 115 may be designed to collect information or implement automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based service charging.

[0052] Some UEs 115 may be configured to employ a reduced power consumption mode of operation, such as half-duplex communication (e.g., a mode that supports one-way communication via transmission or reception, but not simultaneous transmission and reception). In some examples, half-duplex communication may be performed at a reduced peak rate. Other power saving techniques for UE 115 include entering a power saving "deep sleep" mode when not engaged in active communications or operating over limited bandwidth (e.g., in accordance with narrowband communications). In some cases, UE 115 may be designed to support critical functions (e.g., mission critical functions), and the wireless communication system 100 may be configured to provide ultra-reliable communications for these functions.

[0053] In some cases, the UE 115 may also communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol). One or more of the group of UEs 115 utilizing D2D communication may be within the geographic coverage area 110 of the base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of the base station 105 or may not be able to receive transmissions from the base station 105. In some cases, the group of UEs 115 communicating via D2D communication may utilize a one-to-many (1:M) system in which each UE 115 transmits to each other UE 115 in the group. In some cases, the base station 105 facilitates the scheduling of resources for D2D communication. In other cases, D2D communication is performed between UEs 115 without involving the base station 105.

[0054] The base stations 105 may communicate with the core network 130 and with each other. For example, the base stations 105 may interface with the core network 130 via a backhaul link 132 (e.g., via an S1, N2, N3, or other interface). The base stations 105 may communicate with each other directly (e.g., directly between the base stations 105) or indirectly (e.g., via the core network 130) via a backhaul link 134 (e.g., via an X2, Xn, or other interface).

[0055] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connections, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC), which may include at least one mobile management entity (MME), at least one serving gateway (S-GW), and at least one packet data network (PDN) gateway (P-GW). The MME may manage non-access stratum (e.g., control plane) functions, such as mobility, authentication, and bearer management, for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be transmitted through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation and other functions. The P-GW may be connected to network operator IP services. Operator IP services may include access to the Internet, (multiple) intranets, IP multimedia subsystems (IMS), or packet switched (PS) streaming services.

[0056] At least some network devices, such as base stations 105, may include subcomponents such as access network entities, which may be examples of access node controllers (ANCs). Each access network entity may communicate with UE 115 through several other access network transmission entities, which may be referred to as radio heads, smart radio heads, or transmit / receive points (TRPs). In some configurations, the various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or integrated into a single network device (e.g., base station 105).

[0057] The wireless communication system 100 can operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Typically, the region of 300 MHz to 3 GHz is referred to as the ultra-high frequency (UHF) region or decimeter band because the wavelength range is approximately 1 decimeter to 1 meter long. UHF waves may be blocked or redirected by buildings and environmental features. However, these waves can penetrate structures enough to allow macro cells to serve UEs 115 indoors. Transmissions using UHF waves can be associated with smaller antennas and shorter ranges (e.g., less than 100 km) than transmissions using smaller frequencies and longer waves in the high frequency (HF) or very high frequency (VHF) portions of the spectrum with frequencies less than 300 MHz.

[0058] The wireless communication system 100 may also operate in the Super High Frequency (SHF) region using frequency bands from 3 GHz to 30 GHz (also known as centimeter wave bands). The SHF region includes frequency bands such as the 5 GHz Industrial, Scientific, and Medical (ISM) band, which may be used by devices that can tolerate interference from other users.

[0059] The wireless communication system 100 can also operate in the extremely high frequency (EHF) region (e.g., from 30 GHz to 300 GHz), also known as the millimeter wave band. In some examples, the wireless communication system 100 can support millimeter wave (mmW) communications between the UE 115 and the base station 105, and the extremely high frequency antennas of each device can be smaller and closer than the ultra-high frequency antennas. In some cases, this can facilitate the use of antenna arrays within the UE 115. However, the propagation of EHF transmissions may be subject to greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The technology disclosed herein can be used across transmissions using one or more different frequency regions, and the designated use of frequency bands across these frequency regions may vary by country or regulatory agency.

[0060] In some cases, the wireless communication system 100 can utilize licensed and unlicensed radio frequency spectrum bands. For example, the wireless communication system 100 can adopt license assisted access (LAA), LTE unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5GHz ISM band. When operating in an unlicensed radio frequency spectrum band, wireless devices such as base stations 105 and UE 115 can adopt a listen-before-talk (LBT) process to ensure that the channel is clear before sending data. In some cases, operations in unlicensed bands can be based on carrier aggregation configurations and component carriers operating in licensed bands (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum can be based on frequency division duplexing (FDD), time division duplexing (TDD), or a combination of both.

[0061] In some examples, the base station 105 or the 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) communication, or beamforming. For example, the wireless communication system 100 may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115), wherein the transmitting device is equipped with multiple antennas and the receiving device is equipped with one or more antennas. MIMO communication may employ multipath signal propagation to improve spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. For example, multiple signals may be transmitted by a transmitting device via different antennas or different combinations of antennas. Similarly, multiple signals may be received by a receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports for channel measurement and reporting. MIMO technology includes single-user MIMO (SU-MIMO), in which multiple spatial layers are sent to the same receiving device, and multi-user MIMO (MU-MIMO), in which multiple spatial layers are sent to multiple devices.

[0062] Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105 or a UE 115) to shape or direct an antenna beam (e.g., a transmit beam or a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining signals communicated via antenna elements of an antenna array so that signals propagating in a particular direction relative to the antenna array experience constructive interference and other signals experience destructive interference. Adjustments to signals transmitted via antenna elements may include the transmitting device or the receiving device applying certain amplitude and phase offsets to signals transmitted via each antenna element associated with the device. Adjustments associated with each antenna element may be defined by a set of beamforming weights associated with a particular direction (e.g., relative to the antenna array of the transmitting device or the receiving device, or relative to some other direction).

[0063] In one example, the base station 105 may use multiple antennas or antenna arrays to perform beamforming operations for directional communication with the UE 115. For example, the base station 105 may transmit some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) multiple times in different directions, which may include signals transmitted according to different beamforming weight sets associated with different transmission directions. The transmission of different beam directions can be used to identify (e.g., by the base station 105 or a receiving device, such as the UE 115) a beam direction for subsequent transmission and / or reception by the base station 105.

[0064] Some signals, such as data signals associated with a particular receiving device, may be transmitted by base station 105 in a single beam direction (e.g., a direction associated with a receiving device such as UE 115). In some examples, a beam direction associated with transmitting along a single beam direction may be determined based at least in part on signals transmitted in different beam directions. For example, UE 115 may receive one or more of the signals transmitted by base station 105 in different directions, and UE 115 may report to base station 105 an indication of the signal it received with the highest signal quality or other acceptable signal quality. Although these techniques are described with reference to signals transmitted by base station 105 in one or more directions, UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by UE 115), or for transmitting signals in a single direction (e.g., for transmitting data to a receiving device).

[0065] A receiving device (e.g., UE 115, which may be an example of a millimeter wave receiving device) may try multiple receive beams when receiving various signals from base station 105 (e.g., synchronization signals, reference signals, beam selection signals, or other control signals). For example, the receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as "listening" according to different receive beams or receive directions. In some examples, the receiving device may receive along a single beam direction using a single receive beam (e.g., when receiving a data signal). The single receive beam may be aligned in a beam direction determined based on listening according to different receive beam directions (e.g., a beam direction with the highest signal strength, the highest signal-to-noise ratio, or otherwise acceptable signal quality determined based on listening according to multiple beam directions).

[0066] In some cases, the antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays that may support MIMO operations, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be collocated on an antenna assembly (e.g., an antenna tower). In some cases, the antennas or antenna arrays associated with a base station 105 may be located at different geographic locations. A base station 105 may have an antenna array with several rows and columns of antenna ports that the base station 105 may use to support beamforming for communications with a UE 115. Similarly, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

[0067] In some cases, the wireless communication system 100 can be a packet-based network operating according to a layered protocol stack. In the user plane, the communication at the bearer or packet data aggregation protocol (PDCP) layer can be based on IP. The radio link control (RLC) layer can perform packet segmentation and reorganization to communicate on a logical channel. The medium access control (MAC) layer can perform priority processing and multiplex logical channels into transport channels. The MAC layer can also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer can provide the establishment, configuration and maintenance of the RRC connection between the base station 105 or the core network 130 that supports the radio bearer for user plane data. At the physical layer, the transport channel can be mapped to the physical channel.

[0068] In some cases, UE 115 and base station 105 may support retransmission of data to increase the possibility of successfully receiving data. HARQ feedback is a technique to increase the possibility of correctly receiving data through communication link 125. HARQ may include a combination of error detection (e.g., using cyclic redundancy check (CRC)), forward error correction (FEC) and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve the throughput of the MAC layer under poor radio conditions (e.g., signal-to-noise ratio conditions). In some cases, a wireless device may support same-slot HARQ feedback, wherein the device may provide HARQ feedback in a specific time slot for data received in a previous symbol in the time slot. In other cases, the device may provide HARQ feedback in a subsequent time slot or according to some other time interval.

[0069] The time interval in LTE or NR can be expressed as a multiple of the basic time unit. For example, the basic time unit can refer to T s=1 / 30,720,000 second sampling period. The time intervals of the communication resources may be organized according to radio frames each having a duration of 10 milliseconds (ms), where the frame period may be represented as T f =307,200T s . A radio frame may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots, each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix preceding each symbol period). In addition to the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases, a subframe may be the minimum scheduling unit of the wireless communication system 100 and may be referred to as a transmission time interval (TTI). In other cases, the minimum scheduling unit of the wireless communication system 100 may be shorter than a subframe, or may be dynamically selected (e.g., in a burst of a shortened TTI (sTTI), or in a component carrier selected using an sTTI).

[0070] In some wireless communication systems, a time slot may be further divided into multiple mini-slots containing one or more symbols. In some cases, a symbol of a mini-slot or a mini-slot may be the minimum unit of scheduling. For example, the duration of each symbol may vary depending on the subcarrier spacing or the operating frequency band. In addition, some wireless communication systems may implement time slot aggregation, where multiple time slots or mini-slots are aggregated and used for communication between UE 115 and base station 105.

[0071] The term "carrier" refers to a collection of radio frequency spectrum resources with a defined physical layer structure for supporting communication over the communication link 125. For example, a carrier of the communication link 125 may include a portion of a radio frequency spectrum band that operates according to a physical layer channel for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a predefined frequency channel (e.g., an Evolved Universal Mobile Telecommunications System Terrestrial Radio Access (E-UTRA) Absolute Radio Frequency Channel Number (EARFCN)) and may be located by the UE 115 according to a channel raster for discovery. A carrier may be a downlink or uplink (e.g., in FDD mode), or may be configured to carry downlink and uplink communications (e.g., in TDD mode). In some examples, a signal waveform transmitted over a carrier may be composed of multiple subcarriers (e.g., using a multi-carrier modulation (MCM) technique such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)).

[0072] The organization structure of the carrier may be different for different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR). For example, communications on a carrier may be organized based on TTIs or time slots, where each TTI or time slot may include user data and control information or signaling to support decoding of the user data. The carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc.) and control signaling to coordinate the operation of the carrier. In some examples (e.g., in a carrier aggregation configuration), the carrier may also have acquisition signaling or control signaling to coordinate the operation of other carriers.

[0073] Physical channels can be multiplexed on a carrier according to various techniques. Physical control channels and physical data channels can be multiplexed on a downlink carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information sent in the physical control channel can be distributed in a cascaded manner between different control regions (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces).

[0074] A carrier can be associated with a particular bandwidth of the radio frequency spectrum, and in some examples, the carrier bandwidth can be referred to as the "system bandwidth" of the carrier or wireless communication system 100. For example, the carrier bandwidth can be one of several predetermined or defined bandwidths of a carrier for a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). In some examples, each serviced UE 115 can be configured to operate on part or all of the carrier bandwidth. In other examples, some UEs 115 can be configured to operate using a narrowband protocol type associated with a predefined portion or range (e.g., a set of subcarriers or RBs) within a carrier (e.g., an "in-band" deployment of a narrowband protocol type).

[0075] In a system using MCM technology, a resource element may include a symbol period (e.g., the duration of a modulation symbol) and a subcarrier, where the symbol period and the 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). Therefore, the more resource elements received by UE 115 and the higher the order of the modulation scheme, the higher the data rate may be for UE 115. In a MIMO system, wireless communication resources may refer to a combination of radio spectrum resources, time resources, and space resources (e.g., space layers), and the use of multiple space layers may further increase the data rate used to communicate with UE 115.

[0076] A device of the wireless communication system 100 (e.g., a base station 105 or a UE 115) may have a hardware configuration that supports communication on a specific carrier bandwidth, or may be configured to support communication on one of a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a base station 105 and / or a UE 115 that supports simultaneous communication via carriers associated with more than one different carrier bandwidths.

[0077] The wireless communication system 100 may support communication with the UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation or multi-carrier operation. The UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

[0078] In some cases, the wireless communication system 100 can utilize an enhanced component carrier (eCC). An eCC can have one or more characteristics, including a wider carrier or frequency channel bandwidth, a shorter symbol duration, a shorter TTI duration, or a modified control channel configuration. In some cases, an eCC can be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have suboptimal or non-ideal backhaul links). An eCC can also be configured for unlicensed spectrum or shared spectrum (e.g., allowing more than one operator to use the spectrum). An eCC characterized by a wide carrier bandwidth can include one or more segments that can be used by a UE 115 that is not able to monitor the entire carrier bandwidth or is otherwise configured to use a limited carrier bandwidth (e.g., to save power).

[0079] In some cases, an eCC may use a different symbol duration than other component carriers, which may include using a reduced symbol duration compared to the symbol duration of other component carriers. A shorter symbol duration may be associated with an increased spacing between adjacent subcarriers. A device utilizing an eCC, such as a UE 115 or a base station 105, may transmit a wideband signal (e.g., based on a frequency channel or carrier bandwidth of 20, 40, 60, 80 MHz, etc.) at a reduced symbol duration (e.g., 16.67 microseconds). A TTI in an eCC may consist of one or more symbol periods. In some cases, the TTI duration (i.e., the number of symbol periods in a TTI) may be variable.

[0080] The wireless communication system 100 may be an NR system that may utilize any combination of licensed, shared, and unlicensed spectrum bands, etc. The flexibility of eCC symbol duration and subcarrier spacing may allow eCC to be used across multiple spectrums. In some examples, NR shared spectrum may improve spectrum utilization and spectrum efficiency, particularly through dynamic vertical (e.g., across frequency domain) and horizontal (e.g., across time domain) resource sharing.

[0081] A UE 115 (e.g., a first UE 115) may establish a sidelink connection with a second UE 115, wherein the sidelink connection is associated with a plurality of streams. The UE 115 may determine a radio link state of the sidelink connection based on monitoring each of the plurality of streams. The UE 115 may send a non-access layer layer message to the second UE 115 based on the determination, at least based on the radio link state of the sidelink connection.

[0082] A UE 115 (e.g., a second UE 115) may establish a sidelink connection with a first UE 115, wherein the sidelink connection is associated with a plurality of streams. The UE 115 may receive a non-access stratum layer message indicating a radio link state of the sidelink connection from the first UE 115, wherein the non-access stratum layer message is based on a state of each of the plurality of streams at the first UE. The UE 115 may send a response message to the first UE 115 indicating that the radio link state of the sidelink connection with the first UE 115 is active.

[0083] Figure 2 An example of a wireless communication system 200 supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. In some examples, the wireless communication system 200 can implement aspects of the wireless communication system 100. The wireless communication system 200 can include a base station 205, a UE 210, and a UE 215, which can be examples of corresponding devices described herein. In some aspects, the UE 210 and the UE 215 can communicate via a side link connection.

[0084] Wireless communication systems can use different interfaces to support wireless communication between wireless devices. For example, the Uu interface can be used to support wireless communication between base station 205 and UE 210 and / or UE 215 on link 220 and / or 225, respectively. The PC5 interface can be used to support wireless communication between UE 210 and UE 215. Each interface type is unique in terms of configuration, requirements, etc. UE 210 and UE 215 can establish a side link connection through the PC5 interface, wherein the side link connection supports multiple streams (only the first stream 230 and the second stream 235 are shown as examples). Streams generally refer to data communicated through separate DRBs, data communicated with different QoS requirements, etc. Some wireless communication systems are configured so that no AS layer signaling can be used for RLM / RLF. Some wireless communication systems can also be configured so that there is no lower layer indication on the receiver side of RLF support. Therefore, this may cause the UE to communicate on the side link channel without an effective or efficient way to manage the side link connection. In some aspects, this may mean that the UE unnecessarily declares RLF for the side link connection when the link is still active but may have been degraded to some extent. Unnecessarily declaring RLF means wasting a lot of resources and time to disconnect the side link connection and then reestablish a new side link connection.

[0085] For example, for the NR PC5 interface, the UE may establish a Layer 2 (L2) link (e.g., a sidelink connection) with a peer UE using multiple associated QoS flows / DRBs. In some examples, traffic on the NR PC5 interface may be periodic, e.g., there is no guarantee that traffic for a particular flow will always be present. Some wireless communication systems may be configured such that there are no receiver-side synchronization / asynchronous (e.g., active or inactive) indications provided to upper layers. In contrast, some wireless communication systems may rely on HARQ feedback for link maintenance. However, when there are multiple QoS flows (e.g., mapped to DRBs), each flow may use a different configuration. Therefore, HARQ feedback from one QoS flow may not reflect problems with other QoS flows. In addition, due to non-periodic traffic, there may not be any HARQ feedback, which may further delay link problem detection.

[0086] Thus, aspects of the technology may include performing PC5-RRC based aggregation of different RLF triggers (e.g., data loss of communications) from DRBs (e.g., multiple flows) to avoid unnecessary RLF declarations. Aspects of the technology utilize an efficient NAS layer keep-alive mechanism to allow detection of RLF in a reliable and resource-efficient manner at the receiver and transmitter sides. In certain aspects, this may take into account the unique QoS requirements of each flow (e.g., DRB). In some aspects, this may include a PC5-RRC layer implemented at each UE aggregating different QoS flow / DRB information for RLM / RLF signaling before triggering NAS layer actions.

[0087] For example, UE 210 and UE 215 can establish a side link connection including multiple streams or otherwise associated with multiple streams. In the example shown in the wireless communication system 200, a first stream 230 and a second stream 235 are shown. However, it should be understood that the side link connection can have more than two streams. In general, UE 210 and UE 215 can monitor each stream in the side link connection to determine the radio link state of the side link connection. Although the technology described here is provided with reference to UE 210 (e.g., a first UE), it should be understood that UE 215 (e.g., a second UE) can also be configured to implement aspects of the described technology. UE 210 and UE 215 can generally exchange various messages at the AS layer and / or NAS layer based on the radio link state of the side link connection.

[0088] For example, UE 210 may monitor each flow configured for or otherwise associated with a sidelink connection to determine the radio link status. The monitoring may be based on acknowledgement feedback information, for example, determining whether an acknowledgement or negative acknowledgement HARQ feedback message is received, and if so, how many of each message type are received. For example, a threshold number of negative acknowledgements received within a time period may signal that no data is being successfully communicated over the flow. As another example, a failure to receive an acknowledgement or negative acknowledgement message for data sent over a flow may signal that no data is being successfully communicated over the flow.

[0089] Additionally or alternatively, monitoring can be based on a timer (e.g., an inactivity timer) associated with each flow. For example, the UE 210 can establish an inactivity timer for each flow to determine how much time has passed since data was successfully communicated through the flow. The value or threshold of the inactivity timer can be a configured value and / or can be determined by the UE 210 based on historical information of the flow (e.g., based on observed properties of data communicated through the flow). The UE 210 can also establish an inactivity timer for the flow based on QoS parameters associated with the flow, such as PC5 five quality indicators (PQI), data rate, maximum data burst rate (MDBV), average window, etc. The expiration of the inactivity timer can signal that no data is successfully communicated through the flow.

[0090] Additionally or alternatively, monitoring may be based on whether data communicated by a flow meets a QoS configuration for the flow. For example, a threshold amount of data communicated by a flow within a period of time that fails to meet the QoS configuration for the flow may signal that no data is successfully communicated by the flow.

[0091] UE 210 may determine whether there is data successfully communicated through each flow in the side link connection based on monitoring, such as based on an inactivity timer, HARQ feedback, etc. If UE 210 determines that there is no data successfully communicated through the first flow 230 (as a non-limiting example), it may trigger an error indication (e.g., an RLF trigger) to the PC5-RRC layer. Based on the trigger, the PC5-RRC layer of UE 210 may query other (multiple) active flows (e.g., a second flow 235 associated with the same destination, such as an L2 identifier (ID) or L2 link ID with the same cast type) to determine whether there is data successfully communicated through (multiple) of these flows. Based on the response to the query, UE 210 may take various steps.

[0092] In one case, UE 210 may determine that there is no data successfully communicated through the second stream 235 and / or any other stream configured in the side link connection. In response, UE 210 may send a NAS layer message (e.g., a keep-alive message or signaling) to UE 215. In general, the NAS layer message may be configured to convey a request to UE 215 to confirm that the radio link state of the side link connection is active. In the case where UE 215 receives a keep-alive message, it may send a response message indicating that the radio link state of the side link connection is active to UE 210. For example, UE 215 may also monitor different streams configured for the side link connection to determine the radio link state from its perspective. If the response message indicates that the side link connection is active, this may signal or otherwise convey an indication that the side link connection is active, but may have been degraded to a certain extent (e.g., due to mobility) so that the data being communicated may not fully meet the QoS requirements associated with the stream and / or at least some of the data has been discarded.

[0093] Thus, UE 210 and UE 215 may exchange one or more messages (e.g., at the NAS layer and / or at the AS layer) to reconfigure various parameters of the side link connection. For example, UE 210 and UE 215 may select new QoS requirements for a flow (e.g., the first flow 230 that experiences data communication loss in this example) from a set of available or otherwise configured QoS configurations. That is, UE 210 and UE 215 (and / or base station 205) may configure multiple QoS configurations for the side link connection. UE 210 and UE 215 may select from the QoS configurations for each flow. In the event that communication through a flow is degraded, UE 210 and UE 215 may select a new QoS configuration for the flow to improve data communication.

[0094] Additionally or alternatively, this may also include modifying various NAS layer parameters associated with the QoS requirements of the flow. For example, UE 210 and UE 215 may adjust the transmit power level, may switch from negative acknowledgement mode to acknowledgement mode for the flow, may adjust the range for the flow, the delay for the flow, may adjust the peak error rate (PER) for the flow, etc.

[0095] Additionally or alternatively, UE 210 and UE 215 may select a new configuration for the side link connection from a set of available or otherwise configured configurations for the side link connection. That is, UE 210 and UE 215 (and / or base station 205) may configure multiple configurations for the side link connection. UE 210 and UE 215 may select from different configurations for the side link connection to improve data communication. Therefore, this may enable UE 210 and UE 215 to more efficiently manage each flow associated with the side link connection in a dynamic manner.

[0096] Additionally or alternatively, this may also include modifying various AS layer parameters associated with the QoS requirements of the flow. For example, UE 210 and UE 215 may adjust the modulation and coding scheme (MCS) used for the flow, etc.

[0097] In the event that UE 215 does not receive the keep-alive message (and therefore cannot respond), UE 210 may determine that no response message to the keep-alive message has been received from UE 215. This may signal or otherwise convey an indication that the sidelink connection is inactive (e.g., RLF has occurred). Accordingly, UE 210 may initiate an RLF recovery procedure in which it disconnects the sidelink connection with UE 215 and begins establishing a new sidelink connection. In some aspects, this may include UE 210 disconnecting the L2 link (and releasing all associated resources) and reporting an error to base station 205 over link 220 (e.g., using a UuRRC SidelinkUEInfo message). Alternatively, the NAS layer may choose to perform RLF recovery by maintaining a security association with UE 210 and performing another discovery for the same application layer ID.

[0098] In another case, UE 210 may determine that there is data successfully communicated by (multiple) other streams in the second stream 235 and / or the side link connection. This may indicate that the radio link state for the side link connection is a degraded radio link state, for example, the side link connection performance has been degraded to a certain extent, but is still suitable for wireless communication. In response, UE 210 may send a NAS layer message (e.g., a keep-alive message) to UE 215. In general, the NAS layer message may be configured to transmit a request from UE 215, which confirms that the radio link state of the side link connection is active. In this case, UE 215 may receive a keep-alive message and respond with a response message indicating that the radio link state of the side link connection is active. In this example, UE 210 may send another message (e.g., at the NAS layer and / or at the AS layer) to UE 215, which reconfigures various parameters of the side link connection, for example, changes QoS parameters, selects a new QoS configuration, selects a new configuration for the side link connection, etc.

[0099] In some aspects, the transmission of a NAS layer message (e.g., a keep-alive message) may depend on whether a previous keep-alive message was sent within a threshold time period. That is, after determining that the first stream 230 has no data being successfully communicated, the UE 210 may determine when the last keep-alive message was sent to the UE 215. If the last keep-alive message was sent within the threshold time period, the UE 210 may avoid sending another keep-alive message at that moment. Conversely, the UE 210 may again determine whether data is being successfully communicated through the first stream 230 after the threshold time period, and if not, if necessary, a second keep-alive message is sent. In some examples, the NAS layer message may be a PC5 sidelink (PC5-S) message.

[0100] In some aspects, the described techniques may support RLF triggering based on QoS parameters and cancellation based on AS layer keep-alive signaling. That is, since the error triggering to the NAS layer can be based on a single DRB (e.g., flow), different configurations for RLF triggering (e.g., queries implemented at the PC5-RRC layer) can be configured based on the QoS of the flow. For example, for each DRB, there may be an associated PQI and corresponding QoS parameters. Therefore, the criteria for triggering an RLF error (e.g., query) may be determined based on various factors. For example, based on the PQI, a guaranteed bit rate flow type may have an estimated traffic periodicity, for example, considering bit rate, average window, typical packet size, etc. Therefore, different inactivity timers may be used to trigger RLF indications for different DRBs. From the transmitter side (e.g., UE 215), based on the traffic pattern of the QoS flow (e.g., maximum data burst volume (MDBV)), UE 215 may determine that some burst QoS flows should have a higher RLC failure count before triggering an RLF indication. For such high burst flows, the channel busy rate (CBR) may also be considered.

[0101] Regarding NAS layer keep-alive signaling, this may consume considerable radio resources. Therefore, in some examples, a keep-alive message may be triggered due to a NAS layer indication. A keep-alive timer (e.g., a threshold time period) may be reset whenever the PC5-RRC layer has successful signaling. In some examples, a DRB layer transmission with successful HARQ may also cancel the keep-alive messaging.

[0102] Thus, aspects of the described technology introduce keep-alive signaling in the PC5-S protocol. In the keep-alive signaling management, this can take into account AS layer indications (e.g., to reduce waste). The PC5-RRC layer can handle RLF triggers to the NAS layer based on different DRB (e.g., flow) considerations. Due to RLF management, aspects of the described technology can also introduce PC5-RRC layer signaling to reconfigure DRBs. UE configuration for RLF detection (e.g., inactivity timer) can be based on QoS information.

[0103] Figure 3 An example of a process 300 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. In some examples, the process 300 can implement aspects of the wireless communication system 100 and / or 200. Aspects of the process 300 can be implemented by a first UE 305 and a second UE 310, which can be examples of corresponding devices described herein. In some aspects, the first UE 305 and the second UE 310 can perform wireless communication over a sidelink channel.

[0104] In some aspects, the first UE 305 may include a NAS layer 315 (e.g., an L3 or NAS protocol layer) and a PC5-RRC layer 320 (e.g., an L2 or AS protocol layer). Similarly, the second UE 310 may include a NAS layer 350 and a PC5-RRC layer 345. As discussed, the first UE 305 and the second UE 310 may have established a side link connection including multiple streams. Each stream may correspond to a different DRB and / or QoS requirement associated with data communication on the stream. Thus, in the example process 300, the first UE 305 may include a first DRB 325 and a second DRB 330. Similarly, the second UE 310 may include a first DRB 340 and a second DRB 335. Thus, the first DRB 325 of the first UE 305 and the first DRB 340 of the second UE 310 may correspond to or otherwise be associated with a first stream for data communication on the side link channel. The second DRB 330 of the first UE 305 and the second DRB 335 of the second UE 310 may correspond to or otherwise be associated with a second flow for communicating data on the sidelink channel. As described above, the first flow and the second flow (and any other flows configured for the sidelink connection) may have separate configurations, such as QoS requirements.

[0105] Thus, at 355, the first UE 305 and the second UE 310 may perform wireless communications (e.g., communicate data) over a first flow of the sidelink connection (e.g., via a first DRB 325 of the first UE 305 and a first DRB 340 of the second UE 310). The data communicated over the first flow may have associated QoS requirements, such as latency thresholds, reliability thresholds, throughput requirements, etc.

[0106] Similarly, at 360, the first UE 305 and the second UE 310 may perform wireless communications over a second flow of the sidelink connection (e.g., via a second DRB 330 of the first UE 305 and a second DRB 335 of the second UE 310). The data communicated over the second flow may have associated QoS requirements that are the same as or different from the QoS requirements of the first flow.

[0107] Typically, the first UE 305 and the second UE 310 may monitor data communicated on each stream configured for the side link connection. Based on the monitoring, each UE may determine the radio link state for the side link connection. However, at 360, the first UE 305 may determine that no data is being successfully communicated through the second stream (as indicated by an X). It should be understood that the lack of data successfully communicated through the second stream is provided only as a non-limiting example, and the technology may be implemented for any stream configured for the side link connection.

[0108] For example, the first UE 305 may determine that no data is being successfully communicated via the second flow based on an inactivity timer exceeding a threshold time / expiring, based on a lack of an acknowledgement message received for data communicated via the second flow, etc. As discussed, the determination that no data is being successfully communicated (e.g., RLF triggering) may be configured the same or differently for each flow. That is, the threshold for determining that no data is being successfully communicated via the second flow may be the same or different than the threshold for determining that no data is being successfully communicated via the first flow.

[0109] At 365, and for the first flow on DRB1, the first UE 305 may determine that it has no data successfully communicated within a threshold time (e.g., based on an inactivity timer with a configured value) and / or that it cannot send data over the first flow (e.g., based on HARQ feedback), and send an error indicator (e.g., RLF trigger) to the PC5-RRC layer 320 (e.g., the lack of data at 360 may trigger an error or RLF indication at 365). In some aspects, the error indication may be based on the data communicated over the second flow failing to meet the QoS requirements associated with the second flow.

[0110] At 370, and in response to the error indication, the PC5-RRC layer 320 may query other flows of the sidelink connection (including the first flow on DRB1) to determine whether they have experienced a loss of data communication. For example, the PC5-RRC layer 320 may check inactivity timers associated with the other flows, determine whether data communicated through the other flows is successful (e.g., based on HARQ feedback), determine whether data communicated through the other flows meets corresponding QoS requirements, and the like. Thus, the PC5-RRC layer 320 will query other active bearers (e.g., DRB1) with the same destination address (e.g., layer 2 ID with the same conversion type). The next step taken by the first UE 305 may depend on the response to the query at 370.

[0111] In a first option and at 375, the PC5-RRC layer 320 may determine that there is data successfully communicated via other flows (e.g., the first flow) of the sidelink channel. For example, the PC5-RRC layer 320 may determine that an inactivity timer associated with the other flows may not have reached a threshold / expired, data is being communicated and confirmed via the other flows, etc. In some aspects, the response to the query may also include measurement information of the associated flows, such as CQI, RSRP, etc.

[0112] In response to determining that data is being successfully communicated through other streams, the PC5-RRC layer 320 can take several steps. One step can include canceling the trigger received at 365. That is, determining that data is being communicated through other streams can indicate that the side link connection has not experienced RLF, and thus avoids unnecessary triggering of the RLF recovery process and / or the transmission of NAS layer messages. In another example, and at 380, the first UE 305 can initiate PC5-RRC signaling to the second UE 310 to change to a different configuration. That is, the first UE 305 can send a message to the second UE 310 (at the NAS and / or AS layer) to reconfigure one or more parameters of the side link connection. This can include adjusting MCS, power level, range, etc. to improve compliance with associated QoS requirements. This can include selecting a new configuration for the QoS configuration and / or selecting a new configuration for the side link channel.

[0113] In some aspects, this may include triggering the NAS layer 315 to update the QoS flow configuration. In some aspects, the PC5-RRC layer 320 of the first UE 305 and the PC5-RRC layer 345 of the second UE 310 may have a set of QoS configurations configured for the flow, and select a new QoS configuration without notifying the NAS layer 315 of the first UE 305 and / or the NAS layer 350 of the second UE 310.

[0114] In a second option and at 385, a query regarding data successfully communicated through other flows may return an error indication. For example, the error indication may also be associated with inactivity timers of other flows reaching corresponding thresholds (e.g., expiring), failure to meet QoS requirements configured for each flow, lack of HARQ feedback for data communicated through a flow, etc.

[0115] In response and at 390, the PC5-RRC layer 320 may indicate an error (e.g., RLF trigger) to the NAS layer 315. At 390, this may trigger the NAS layer 315 to initiate (e.g., send) keep-alive signaling with the NAS layer 350 of the second UE 310. The keep-alive signaling (e.g., NAS layer message) sent at the NAS layer 315 may be sent over one or more flows and / or SRBs (e.g., to improve reliability and feedback from the second UE 310). In some aspects, the error indication may also carry or convey information identifying a cause of the error indication.

[0116] If the second UE 310 receives the keep-alive signaling at 395 and responds, this may trigger the PC5-RRC layer 320 of the first UE 305 and the PC5-RRC layer 345 of the second UE 310 to exchange various messages to reconfigure parameters associated with the flows of the sidelink connection. For example, they may renegotiate DRB and / or QoS flow configurations for any affected flows of the sidelink connection.

[0117] However, if the NAS layer signaling returns an error (e.g., the first UE 305 does not receive a response to the keep-alive signaling), the first UE 305 may declare RLF and initiate an RLF recovery process, for example, disconnecting the L2 link (e.g., the side link connection) and releasing all associated resources and reporting an error to its base station. Alternatively, the NAS layer 315 of the first UE 305 and the NAS layer 350 of the second UE 310 may choose to perform RLF recovery by maintaining (e.g., maintaining) a security association and having another discovery of the same application layer ID.

[0118] Thus, process 300 illustrates various techniques that may be used at the AS layer (e.g., PC5-RRC layer) and / or NAS layer of the first UE 305 and the second UE 310 in the event that RLF is detected on at least one flow (e.g., at least one DRB) of the sidelink connection. This may avoid situations where RLF is unnecessarily declared, which would utilize a significant amount of air resources to establish a new sidelink connection.

[0119] Figure 4An example of a process 400 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. In some examples, the process 400 may implement aspects of the wireless communication system 100 and / or 200 and / or the process 300. Aspects of the process 400 may be implemented by a first UE 405 and a second UE 410, which may be examples of respective devices described herein. In some aspects, the first UE 405 and the second UE 410 may perform wireless communication via a sidelink channel.

[0120] In some aspects, the first UE 405 may include a NAS layer 415 (e.g., an L3 or NAS protocol layer) and a PC5-RRC layer 420 (e.g., an L2 or AS protocol layer). Similarly, the second UE 410 may include a NAS layer 450 and a PC5-RRC layer 445. As discussed, the first UE 405 and the second UE 410 may have established a sidelink connection including multiple streams. Each stream may correspond to a different DRB and / or QoS requirement associated with data communication. Thus, in the example process 400, the first UE 405 may include a first DRB 425 and a second DRB 430. Similarly, the second UE 410 may include a first DRB 440 and a second DRB 435. Thus, the first DRB 425 of the first UE 405 and the first DRB 440 of the second UE 410 may correspond to or otherwise be associated with a first stream for data communication on the sidelink channel. The second DRB 430 of the first UE 405 and the second DRB 435 of the second UE 410 can correspond to or otherwise be associated with a second flow for communicating data on the sidelink channel. As described above, the first flow and the second flow (and any other flows configured for the sidelink connection) can have separate configurations, such as QoS requirements.

[0121] Thus, at 455, the first UE 405 and the second UE 410 may perform wireless communications (e.g., communicate data) over a first flow of the sidelink connection (e.g., via a first DRB 425 of the first UE 405 and a first DRB 440 of the second UE 410). The data communicated over the first flow may have associated QoS requirements, such as latency thresholds, reliability thresholds, throughput requirements, etc.

[0122] Similarly, at 460, the first UE 405 and the second UE 410 may perform wireless communications over a second flow of the sidelink connection (e.g., via a second DRB 430 of the first UE 405 and a second DRB 435 of the second UE 410). The data communicated over the second flow may have associated QoS requirements that are the same as or different from the QoS requirements of the first flow.

[0123] Typically, the first UE 405 and the second UE 410 may monitor the data communicated on each stream configured for the side link connection. Based on the monitoring, each UE may determine the radio link state for the side link connection. However, at 460, the first UE 405 may determine that no data is being successfully communicated through the second stream (as indicated by an X). It should be understood that the lack of data successfully communicated through the second stream is provided only as a non-limiting example, and the technology may be implemented for any stream configured for the side link connection.

[0124] For example, the first UE 405 may determine that no data is being successfully communicated via the second flow based on an inactivity timer exceeding a threshold time / expiring, based on a lack of an acknowledgement message received for data communicated via the first flow, based on a failure of data communicated via the first flow to meet associated QoS requirements, etc. As discussed, the determination that no data is being successfully communicated (e.g., RLF triggering) may be configured the same or differently for each flow. That is, the threshold for determining that no data is being successfully communicated via the first flow may be the same or different than the threshold for determining that no data is being successfully communicated via the second flow.

[0125] At 465, the NAS layer 415 of the first UE 405 and the NAS layer 450 of the second UE 410 may optionally exchange NAS layer messages (e.g., keep-alive messages). For example, the keep-alive messages may have been exchanged because the first UE 405 and / or the second UE 410 previously detected a loss of data communication on one of the streams connected through the side link according to periodic scheduling, etc.

[0126] At 470, and for the first flow on DRB1, the first UE 405 may determine that it has no data within a threshold time (e.g., based on expiration of an inactivity timer having a configured value) and / or that it cannot send data over the first flow (e.g., based on HARQ feedback), and send an error indication (e.g., an RLF trigger) to the NAS layer 415 (e.g., the lack of data at 460 may trigger the RLF indication at 470). In some aspects, the error indication may be based on the failure of data communicated over the second flow to meet QoS requirements associated with the flow, based on the lack of an acknowledgment message received for data communicated over the flow, based on the expiration of an inactivity timer or reaching a threshold time, etc.

[0127] That is, in some aspects, the NAS layer 415 (e.g., PC5-S, V2X layer) can handle errors from the AS layer based on maintaining active message delivery status. When data communicated through the first stream experiences an interruption, this triggers an error indication to the NAS layer 415. In some aspects, the error indication can carry or convey information that distinguishes the cause of the trigger, for example, due to expiration of an inactivity timer, due to continuous transmission errors (e.g., based on HARQ feedback and / or RLC error count reaching a threshold), and the like.

[0128] Based on the error indication and the triggering cause code, the NAS layer 415 may determine the appropriate action to take. As an example and for the case where the inactivity timer expires, the NAS layer 415 may wait for the next keep-alive period to send the next keep-alive message (e.g., in the case where keep-alive signaling is periodically exchanged between the NAS layer 415 of the first UE 405 and the NAS layer 450 of the second UE 410). For example, the NAS layer 415 may determine that keep-alive signaling was exchanged at 465 and / or that another scheduled keep-alive message is approaching, and therefore wait until the next scheduled keep-alive message.

[0129] As another example, for the case where the trigger is due to a transmission error, the NAS layer 415 may immediately trigger a keep-alive signaling. Thus, at 475, the NAS layer 415 of the first UE 405 may send a keep-alive message to the NAS layer 450 of the second UE 410. In some aspects of this example, the NAS layer 415 may also determine whether a previous NAS layer message (e.g., keep-alive signaling) was sent within a threshold time period, and if so, feedback may be provided to the second flow to wait until the next keep-alive signaling is scheduled.

[0130] If the second UE 410 receives the keep-alive signaling at 475 and responds, this may trigger the PC5-RRC layer 420 of the first UE 405 and the PC5-RRC layer 445 of the second UE 410 to exchange various messages to reconfigure parameters associated with the flows of the sidelink connection. For example, they may renegotiate DRB and / or QoS flow configurations for any affected flows of the sidelink connection.

[0131] However, if the NAS layer signaling returns an error (e.g., the first UE 405 does not receive a response to the keep-alive signaling), the first UE 405 may declare RLF and initiate an RLF recovery process, e.g., disconnect the L2 link (e.g., side link connection) and release all associated resources and report an error to its base station. Alternatively, the NAS layer 415 of the first UE 405 and the NAS layer 450 of the second UE 410 may choose to perform RLF recovery by maintaining (e.g., maintaining) a security association and having another discovery of the same application layer ID.

[0132] Thus, process 400 illustrates various techniques that may be used at the AS layer (e.g., PC5-RRC layer) and / or NAS layer of the first UE 405 and the second UE 410 in the event that RLF is detected on at least one flow (e.g., at least one DRB) of the sidelink connection. This may avoid situations where RLF is unnecessarily declared, which would utilize a significant amount of air resources to establish a new sidelink connection.

[0133] Figure 5 An example of a process 300 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. In some examples, the process 500 can implement aspects of the wireless communication system 100 and / or 200 and / or the process 300 and / or 400. Aspects of the process 500 can be implemented by a first UE 505 and a second UE 510, which can be examples of corresponding devices described herein. In some aspects, the first UE 505 and the second UE 510 can perform wireless communication via a sidelink connection.

[0134] At 515, the first UE 505 and the second UE 510 may establish a sidelink connection. The sidelink connection may be established via a PC5 interface and may include multiple flows. Typically, each flow may correspond to a data flow communicated via a specific DRB over the sidelink connection according to specific QoS requirements, etc.

[0135] At 520, the first UE 505 may determine the radio link state of the side link connection. For example, the first UE 505 may monitor the data of each stream communication through the side link connection to determine the radio link state. Although not shown, it should be understood that the second UE 510 may also monitor the communication of the stream through the side link connection to determine the radio link state from its perspective.

[0136] At 525, the first UE 505 may send (and the second UE 510 may receive) a NAS layer message based on the radio link state of the side link connection. In some aspects, the NAS layer message may include keep-alive signaling to determine whether the side link connection is active. In some aspects, the NAS layer message (and / or as layer messaging) may include information to reconfigure various QoS parameters of the flow.

[0137] In some aspects, this may include the first UE 505 determining that no data is being successfully communicated through the first stream (and / or any (multiple) other streams) of the multiple streams of the side link connection. Therefore, the first UE 505 may send a NAS layer message to the second UE 510, wherein the message includes a keep-alive signaling requesting confirmation from the second UE 510 that the radio link state of the side link connection is active. If the second UE 510 sends a response message indicating that the radio link state of the side link connection is active (and the first UE 505 receives a response), the first UE 505 may send (and the second UE 510 may receive) a second message (e.g., at the NAS layer and / or at the AS layer) to reconfigure one or more parameters of the side link connection. For example, they may reconfigure the side link connection from a first configuration to a second configuration from an available configuration set (e.g., from an available configuration set). As another example, they may reconfigure one or more QoS parameters configured for the side link connection. In some aspects, the first UE 505 may determine that it has not received a response message from the second UE 510. Based on the lack of response, the first UE 505 may determine that the radio link state of the side link connection is RLF. Therefore, the first UE 505 may perform an RLF recovery procedure to establish a second side link connection with the second UE 510.

[0138] In some aspects, the first UE 505 can determine that the data communicated via the first flow fails to meet the corresponding QoS requirements associated with the first flow. In some aspects, this can include the first UE 505 determining that no data has been successfully communicated via the first flow within a threshold time period associated with the first flow (e.g., based on an inactivity timer).

[0139] In some aspects, this can include the first UE 505 determining that no data is successfully communicated via the first stream, but data is being successfully communicated via the second stream of the side link connection (and / or any other stream of the side link connection). Therefore, the first UE 505 can determine that the radio link state of the side link connection is a degraded radio link state. Therefore, the first UE 505 can send (and the second UE 510 can receive) a second message (e.g., at the NAS layer and / or the AS layer) that reconfigures one or more parameters of the side link connection, e.g., selecting a new configuration for the side link connection, reconfiguring QoS parameters, etc.

[0140] In some aspects, the first UE 505 may determine that a NAS layer message is sent within a threshold time period and therefore refrain from sending a second NAS layer message.In some aspects, the NAS layer message may include a PC5-S message.

[0141] Figure 6A block diagram 600 of a device 605 supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The device 605 may be an example of aspects of the UE 115 as described herein. The device 605 may include a receiver 610, a communication manager 615, and a transmitter 620. The device 605 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0142] 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 unicast link RLF detection and management, etc.). The information may be passed to other components of the device 605. The receiver 610 may be a reference Fig. 9 Examples of aspects of transceiver 920 are described. Receiver 610 may utilize a single antenna or a collection of antennas.

[0143] The communication manager 615 can establish a side link connection with a second UE, wherein the side link connection is associated with a stream set, determine a radio link state of the side link connection based on monitoring each stream of the stream set, and based on the determination, send a non-access stratum layer message to the second UE based at least on the radio link state of the side link connection.

[0144] The communication manager 615 may also establish a sidelink connection with the first UE, wherein the sidelink connection is associated with a stream set, receive a non-access stratum layer message indicating a radio link state of the sidelink connection from the first UE, wherein the non-access stratum layer message is based on a state of each stream of the stream set at the first UE, and send a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active. The communication manager 615 may be an example of aspects of the communication manager 910 described herein.

[0145] The actions performed by the communication manager 615 as described herein may be implemented to achieve one or more potential advantages. One implementation may allow the UE 115 to save power and increase battery life by determining the radio link state of the side link connection. Another implementation may provide improved quality of service and reliability at the UE 115 because the side link connection may be enhanced.

[0146] The communication manager 615 or its subcomponents may be implemented by hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functions of the communication manager 615 or its subcomponents may be performed 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.

[0147] The communication manager 615 or its subcomponents can be physically located in a variety of locations, including being distributed so that portions of the functionality are implemented by one or more physical components at different physical locations. In some examples, the communication manager 615 or its subcomponents can be separate and distinct components according to various aspects of the present disclosure. In some examples, the communication manager 615 or its subcomponents can be combined with one or more other hardware components, including but not limited to input / output (I / O) components, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof according to various aspects of the present disclosure.

[0148] Transmitter 620 can transmit signals generated by other components of device 605. In some examples, transmitter 620 can be collocated with receiver 610 in a transceiver module. For example, transmitter 620 can be a reference Fig. 9 Examples of aspects of the transceiver 920 are described. The transmitter 620 may utilize a single antenna or a collection of antennas.

[0149] Figure 7 A block diagram 700 of a device 705 supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The device 705 may be an example of aspects of the device 605 or UE 115 as described herein. The device 705 may include a receiver 710, a communication manager 715, and a transmitter 735. The device 705 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0150] The receiver 710 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to unicast link RLF detection and management, etc.). The information may be passed to other components of the device 705. The receiver 710 may be a reference Fig. 9 Examples of aspects of the transceiver 920 are described. The receiver 710 may utilize a single antenna or a collection of antennas.

[0151] Communications manager 715 may be an example of aspects of communications manager 615 as described herein. Communications manager 715 may include connection manager 720, radio link state manager 725, and NAS layer message manager 730. Communications manager 715 may be an example of aspects of communications manager 910 as described herein.

[0152] The connection manager 720 may establish a sidelink connection with the second UE, wherein the sidelink connection is associated with the set of flows.

[0153] The radio link state manager 725 may determine the radio link state of the side link connection based on monitoring each flow in the set of flows.

[0154] The NAS layer message manager 730 may send a non-access stratum layer message to the second UE based on the determination, at least based on the radio link state of the sidelink connection.

[0155] The connection manager 720 may establish a sidelink connection with the first UE, wherein the sidelink connection is associated with a stream set.

[0156] The NAS layer message manager 730 may receive a non-access stratum layer message indicating a radio link status of a side link connection from a first UE, wherein the non-access stratum layer message is based on a status of each stream of the stream set at the first UE, and send a response message to the first UE indicating that the radio link status of the side link connection with the first UE is active.

[0157] Transmitter 735 can transmit signals generated by other components of device 705. In some examples, transmitter 735 can be collocated with receiver 710 in a transceiver module. For example, transmitter 735 can be a reference Fig. 9 Examples of aspects of the transceiver 920 are described. The transmitter 735 may utilize a single antenna or a collection of antennas.

[0158] Figure 8 A block diagram 800 of a communication manager 805 supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The communication manager 805 may be an example of aspects of the communication manager 615, the communication manager 715, or the communication manager 910 described herein. The communication manager 805 may include a connection manager 810, a radio link state manager 815, a NAS layer message manager 820, an RLF manager 825, a degraded link manager 830, a NAS message timing manager 835, and a QoS manager 840. Each of these modules may communicate with each other directly or indirectly (e.g., via one or more buses).

[0159] The connection manager 810 may establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a set of flows. In some examples, the connection manager 810 may establish a sidelink connection with a first UE, wherein the sidelink connection is associated with a set of flows.

[0160] The radio link state manager 815 may determine the radio link state of the side link connection based on each flow in the set of monitored flows.

[0161] The NAS layer message manager 820 may send a non-access stratum layer message to the second UE based on the determination, at least based on the radio link state of the side link connection. In some examples, the NAS layer message manager 820 may receive a non-access stratum layer message indicating the radio link state of the side link connection from the first UE, wherein the non-access stratum layer message is based on the state of each stream in the stream set at the first UE. In some examples, the NAS layer message manager 820 may send a response message to the first UE indicating that the radio link state of the side link connection with the first UE is active. In some cases, the non-access stratum layer message includes a PC5-S message. In some cases, the non-access stratum layer message includes a keep-alive message requesting confirmation from the second UE that the radio link state of the side link connection is active.

[0162] The RLF manager 825 may determine that there is no data communicated through the first stream of the stream set. In some examples, a non-access stratum layer message is sent to the second UE, wherein the non-access stratum layer message includes a keep-alive message requesting the second UE to confirm that the radio link state of the side link connection is active. In some examples, the RLF manager 825 may receive a response message from the second UE indicating that the radio link state of the side link connection with the second UE is active. In some examples, the RLF manager 825 may send a second message to the second UE based on the response message, and the second message reconfigures one or more parameters of the side link connection. In some examples, the RLF manager 825 may reconfigure the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection. In some examples, the RLF manager 825 may reconfigure one or more quality of service parameters configured for the side link connection. In some examples, based on the lack of a response message from the second UE, it is determined that the radio link state of the side link connection with the second UE includes a radio link failure.

[0163] In some examples, the RLF manager 825 may perform a radio link failure recovery procedure based on the radio link failure to establish a second side link connection with the second UE. In some examples, the RLF manager 825 may determine that data communicated over the first flow fails to meet a quality of service requirement associated with the first flow. In some examples, the RLF manager 825 may determine that no data has been communicated over the first flow within a threshold time period associated with the first flow.

[0164] The degraded link manager 830 may determine that no data is communicated via a first flow in the flow set. In some examples, the degraded link manager 830 may determine that data is communicated via a second flow in the flow set. In some examples, determining that the radio link state of the side link connection includes a degraded radio link state.

[0165] In some examples, the degraded link manager 830 may send a second message to the second UE to reconfigure one or more parameters of the side link connection. In some examples, the degraded link manager 830 may reconfigure the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection. In some examples, the degraded link manager 830 may reconfigure one or more quality of service parameters configured for the side link connection. In some examples, the degraded link manager 830 may receive a second message from the first UE to reconfigure one or more parameters of the side link connection based on the response message. In some examples, the degraded link manager 830 may reconfigure one or more parameters of the side link connection based at least in part on the second message.

[0166] In some examples, the degraded link manager 830 can reconfigure the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection. In some examples, the degraded link manager 830 can reconfigure one or more quality of service parameters configured for the side link connection.

[0167] The NAS message timing manager 835 may determine that the non-access stratum layer message is sent within a threshold time period. In some examples, the NAS message timing manager 835 may avoid sending a second non-access stratum layer message to the second UE based at least on the non-access stratum layer message.

[0168] The QoS manager 840 may determine, for each flow in the set of flows, whether data communicated through each flow meets the quality of service requirements configured for the flow.

[0169] Fig. 9A diagram of a system 900 including a device 905 that supports unicast link RLF detection and management according to aspects of the present disclosure is shown. The device 905 may be an example of or include components of a device 605, a device 705, or a UE 115 as described herein. The device 905 may include components for two-way voice and data communications, including components for sending and receiving communications, including a communication manager 910, an I / O controller 915, a transceiver 920, an antenna 925, a memory 930, and a processor 940. These components may be in electronic communication via one or more buses (e.g., bus 945).

[0170] The communication manager 910 can establish a side link connection with a second UE, wherein the side link connection is associated with a stream set, determine a radio link state of the side link connection based on monitoring each stream of the stream set, and based on the determination, send a non-access stratum layer message to the second UE based at least on the radio link state of the side link connection.

[0171] The communication manager 910 may also establish a side link connection with the first UE, wherein the side link connection is associated with a stream set, receive a non-access stratum layer message indicating a radio link status of the side link connection from the first UE, wherein the non-access stratum layer message is based on a status of each stream of the stream set at the first UE, and send a response message to the first UE indicating that the radio link status of the side link connection with the first UE is active.

[0172] I / O controller 915 can manage input and output signals of device 905. I / O controller 915 can also manage peripheral devices that are not integrated into device 905. In some cases, I / O controller 915 can represent a physical connection or port to an external peripheral device. In some cases, I / O controller 915 can utilize a computer such as a Or another known operating system. In other cases, I / O controller 915 can be represented or interacted with by a modem, keyboard, mouse, touch screen, or similar device. In some cases, I / O controller 915 can be implemented as part of a processor. In some cases, a user can interact with device 905 via I / O controller 915 or via hardware components controlled by I / O controller 915.

[0173] The transceiver 920 may communicate bidirectionally via one or more antennas, wired or wireless links as described herein. For example, the transceiver 920 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 920 may also include a modem for modulating packets and providing the modulated packets to an antenna for transmission, and demodulating packets received from an antenna.

[0174] In some cases, a wireless device may include a single antenna 925. However, in some cases, a device may have more than one antenna 925, which may be capable of transmitting or receiving multiple wireless transmissions simultaneously.

[0175] The memory 930 may include random access memory (RAM) and read-only memory (ROM). The memory 930 may store computer-readable computer executable code 935, which includes instructions that cause the processor to perform various functions described herein when executed. In some cases, the memory 930 may contain a basic I / O system (BIOS), etc., which may control basic hardware or software operations, such as interaction with peripheral components or devices.

[0176] Processor 940 may include an intelligent hardware device (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor 940 may be configured to operate a memory array using a memory controller. In other cases, the memory controller may be integrated into processor 940. Processor 940 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 930) to cause device 905 to perform various functions (e.g., functions or tasks supporting unicast link RLF detection and management).

[0177] The code 935 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 935 may be stored in a non-transitory computer-readable medium such as a system memory or other type of memory. In some cases, the code 935 may not be directly executed by the processor 940, but may cause a computer (e.g., when compiled and executed) to perform the functions described herein.

[0178] The actions performed by the processor 940, memory 930, I / O controller 915, communication manager 910, transceiver 920, and antenna 925 as described herein may be implemented to achieve one or more potential advantages. One implementation may allow the device 905 to save power and increase battery life by reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection. Another implementation may provide improved reliability and user experience at the device 905 by reducing signaling overhead.

[0179] Fig.10 A flow chart illustrating a method 1000 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The operations of the method 1000 may be implemented by the UE 115 or its components as described herein. For example, the operations of the method 1000 may be implemented by reference to Figures 6 to 9 The communication manager described herein performs. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0180] At 1005, the UE may establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a stream set. The operations of 1005 may be performed according to the methods described herein. In some examples, aspects of the operations of 1005 may be described with reference to Figures 6 to 9 The connection manager is executed.

[0181] At 1010, the UE may determine the radio link state of the side link connection based on each stream in the monitoring stream set. The operation of 1010 may be performed according to the method described herein. In some examples, the radio link state of the side link connection may be determined by, for example, referring to Figures 6 to 9 The radio link state manager is used to perform aspects of the operation of 1010.

[0182] At 1015, the UE may send a non-access layer message to the second UE based on the determination, at least based on the radio link state of the sidelink connection. The operations of 1015 may be performed according to the methods described herein. In some examples, aspects of the operations of 1015 may be described with reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0183] Fig.11 1 is a flowchart illustrating a method 1100 for supporting unicast link RLF detection and management according to aspects of the present disclosure. The operations of the method 1100 may be implemented by the UE 115 or components thereof, as described herein. For example, the operations of the method 1100 may be implemented by reference to Figures 6 to 9 The communication manager described herein performs. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0184] At 1105, the UE may establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a stream set. The operations of 1105 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be described with reference to Figures 6 to 9 The connection manager is executed.

[0185] At 1110, the UE may determine the radio link state of the side link connection based on each stream in the monitoring stream set. The operation of 1110 may be performed according to the method described herein. In some examples, the radio link state of the side link connection may be determined by, for example, Figures 6 to 9The radio link state manager is used to perform aspects of the operation of 1110.

[0186] At 1115, the UE may determine that no data is communicated via the first stream of the stream set. The operations of 1115 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be described with reference to Figures 6 to 9 The RLF manager is used to perform the above operations.

[0187] At 1120, the UE may send a non-access layer message to the second UE based on the determination, at least based on the radio link state of the sidelink connection. The operations of 1120 may be performed according to the methods described herein. In some examples, aspects of the operations of 1120 may be described with reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0188] At 1125, the UE may send a non-access stratum layer message to the second UE, wherein the non-access stratum layer message includes a keep-alive message requesting the second UE to confirm that the radio link state of the side link connection is active. The operations of 1125 may be performed according to the methods described herein. In some examples, aspects of the operations of 1125 may be described by reference to Figures 6 to 9 The RLF manager is used to perform the above operations.

[0189] Fig.12 A flow chart illustrating a method 1200 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The operations of the method 1200 may be implemented by the UE 115 or components thereof, as described herein. For example, the operations of the method 1200 may be implemented by reference to Figures 6 to 9 The communication manager described herein performs. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0190] At 1205, the UE may establish a sidelink connection with a second UE, wherein the sidelink connection is associated with a stream set. The operations of 1205 may be performed according to the methods described herein. In some examples, aspects of the operations of 1205 may be described with reference to Figures 6 to 9 The connection manager is executed.

[0191] At 1210, the UE may determine the radio link state of the side link connection based on monitoring each flow in the set of flows. The operations of 1210 may be performed according to the methods described herein. In some examples, the radio link state of the side link connection may be determined by, for example, Figures 6 to 9 The radio link state manager is used to perform aspects of the operation of 1210.

[0192] At 1215, the UE may send a non-access layer message to the second UE based on the determination, at least based on the radio link state of the sidelink connection. The operations of 1215 may be performed according to the methods described herein. In some examples, aspects of the operations of 1215 may be described by reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0193] At 1220, the UE may determine that no data is communicated via the first stream of the stream set. The operations of 1220 may be performed according to the methods described herein. In some examples, the UE may determine that no data is communicated via the first stream of the stream set. Figures 6 to 9 The downgrade link manager is used to perform aspects of the operation of 1220.

[0194] At 1225, the UE may determine that data is communicated via a second stream in the stream set. The operation of 1225 may be performed according to the method described herein. In some examples, the UE may determine that data is communicated via a second stream in the stream set. Figures 6 to 9 The downgrade link manager is used to perform aspects of the operation of 1225.

[0195] At 1230, the UE may determine that the radio link state of the side link connection includes a degraded radio link state. The operations of 1230 may be performed according to the methods described herein. In some examples, the radio link state of the side link connection may be determined by, for example, Figures 6 to 9 The downgrade link manager is used to perform aspects of the operation of 1230.

[0196] At 1235, the UE may send a second message to the second UE to reconfigure one or more parameters of the side link connection. The operation of 1235 may be performed according to the method described herein. In some examples, the UE may send a second message to the second UE to reconfigure one or more parameters of the side link connection. Figures 6 to 9 The downgraded link manager is used to perform aspects of the operation of 1235.

[0197] Fig.13 1 is a flowchart illustrating a method 1300 for supporting unicast link RLF detection and management according to aspects of the present disclosure. The operations of the method 1300 may be implemented by the UE 115 or its components as described herein. For example, the operations of the method 1300 may be implemented by reference to Figures 6 to 9 The communication manager described herein performs. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0198] At 1305, the UE may establish a sidelink connection with a first UE, wherein the sidelink connection is associated with a stream set. The operations of 1305 may be performed according to the methods described herein. In some examples, aspects of the operations of 1305 may be described with reference to Figures 6 to 9The connection manager is executed.

[0199] At 1310, the UE may receive a non-access stratum layer message from the first UE indicating a radio link status of the side link connection, wherein the non-access stratum layer message is based on a status of each flow in the flow set at the first UE. The operations of 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be described with reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0200] At 1315, the UE may send a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active. The operation of 1315 may be performed according to the methods described herein. In some examples, aspects of the operation of 1315 may be described by reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0201] Fig.14 A flow chart illustrating a method 1400 for supporting unicast link RLF detection and management according to aspects of the present disclosure is shown. The operations of the method 1400 may be implemented by the UE 115 or a component thereof, as described herein. For example, the operations of the method 1400 may be implemented by reference to Figures 6 to 9 The communication manager described herein performs. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0202] At 1405, the UE may establish a sidelink connection with a first UE, wherein the sidelink connection is associated with a stream set. The operations of 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be described with reference to Figures 6 to 9 The connection manager is executed.

[0203] At 1410, the UE may receive a non-access stratum layer message from the first UE indicating a radio link status of the side link connection, wherein the non-access stratum layer message is based on a status of each flow in the set of flows at the first UE. The operations of 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be described with reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0204] At 1415, the UE may send a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be described with reference to Figures 6 to 9 The NAS layer message manager is used to perform the above operations.

[0205] At 1420, the UE may receive a second message from the first UE to reconfigure one or more parameters of the side link connection based on the response message. The operation of 1420 may be performed according to the methods described herein. In some examples, the UE may receive a second message from the first UE to reconfigure one or more parameters of the side link connection based on the response message. Figures 6 to 9 The downgrade link manager is used to perform aspects of the operation of 1420.

[0206] At 1425, the UE may reconfigure one or more parameters of the side link connection based at least in part on the second message. The operations of 1425 may be performed according to the methods described herein. In some examples, the side link connection may be configured as described in reference to Figures 6 to 9 The downgrade link manager is used to perform aspects of the operation of 1425.

[0207] The following provides an overview of aspects of the present disclosure:

[0208] Aspect 1: A method for wireless communication at a first UE, comprising: establishing a side link connection with a second UE, wherein the side link connection is associated with multiple streams; determining a radio link state of the side link connection based at least in part on monitoring each of the multiple streams; and based on the determination, sending a non-access stratum layer message to the second UE based at least on the radio link state of the side link connection.

[0209] Aspect 2: The method according to Aspect 1 also includes: determining that no data is communicated through a first stream among multiple streams; and sending a non-access stratum layer message to a second UE, wherein the non-access stratum layer message includes a keep-alive message requesting the second UE to confirm that the radio link state of the side link connection is active.

[0210] Aspect 3: The method according to aspect 2, wherein determining that no data is communicated comprises determining that data communicated via the first flow fails to meet a quality of service requirement associated with the first flow.

[0211] Aspect 4: The method according to any one of aspects 2 to 3, wherein determining that no data has been communicated comprises determining that no data has been communicated via the first flow within a threshold time period associated with the first flow.

[0212] Aspect 5: The method according to any one of Aspects 1 to 4 further includes: receiving a response message from a second UE indicating that the radio link state of the side link connection with the second UE is active; and sending a second message to the second UE based at least in part on the response message, the second message reconfiguring one or more parameters of the side link connection.

[0213] Aspect 6: The method according to aspect 5, wherein reconfiguring one or more parameters of the sidelink connection comprises: reconfiguring the sidelink connection from a first configuration to a second configuration from a set of available configurations configured for the sidelink connection.

[0214] Aspect 7: The method according to any one of aspects 5 to 6, wherein reconfiguring one or more parameters of the side link connection comprises: reconfiguring one or more quality of service parameters configured for the side link connection.

[0215] Aspect 8: The method according to any one of Aspects 1 to 7 further includes: determining that the radio link state of the side link connection with the second UE includes a radio link failure based at least in part on the lack of a response message from the second UE; and performing a radio link failure recovery process based at least in part on the radio link failure to establish a second side link connection with the second UE.

[0216] Aspect 9: The method according to any one of Aspects 1 to 8 further includes: determining that no data is communicated through a first stream among multiple streams; determining that data is communicated through a second stream among multiple streams; determining that a radio link state of the side link connection includes a degraded radio link state; and sending a second message to a second UE to reconfigure one or more parameters of the side link connection.

[0217] Aspect 10: The method according to Aspect 9, wherein reconfiguring one or more parameters of the sidelink connection comprises: reconfiguring the sidelink connection from a first configuration to a second configuration from a set of available configurations configured for the sidelink connection.

[0218] Aspect 11: The method according to any one of aspects 9 to 10, wherein reconfiguring one or more parameters of the side link connection comprises: reconfiguring one or more quality of service parameters configured for the side link connection.

[0219] Aspect 12: The method according to any one of Aspects 1 to 11 further includes: determining that a non-access stratum layer message is sent within a threshold time period; and avoiding sending a second non-access stratum layer message to the second UE based at least on the non-access stratum layer message.

[0220] Aspect 13: The method according to any one of aspects 1 to 12, wherein determining the radio link status of the sidelink connection comprises: for each of a plurality of flows, determining whether data communicated through each flow meets a quality of service requirement configured for the flow.

[0221] Aspect 14: The method according to any one of aspects 1 to 13, wherein the non-access stratum layer message comprises a PC5 sidelink (PC5-S) message.

[0222] Aspect 15: A method for wireless communication at a second UE, comprising: establishing a sidelink connection with a first UE, wherein the sidelink connection is associated with multiple streams; receiving a non-access stratum layer message indicating a radio link status of the sidelink connection from the first UE, wherein the non-access stratum layer message is based at least in part on a status of each stream of the multiple streams at the first UE; and sending a response message to the first UE indicating that the radio link status of the sidelink connection with the first UE is active.

[0223] Aspect 16: The method according to Aspect 15 further includes: receiving a second message from the first UE to reconfigure one or more parameters of the side link connection based at least in part on the response message; and reconfiguring one or more parameters of the side link connection based at least in part on the second message.

[0224] Aspect 17: The method according to Aspect 16, wherein reconfiguring one or more parameters of the sidelink connection comprises: reconfiguring the sidelink connection from a first configuration to a second configuration from a set of available configurations configured for the sidelink connection.

[0225] Aspect 18: The method according to any one of Aspects 16 to 17, wherein reconfiguring one or more parameters of the side link connection comprises: reconfiguring one or more quality of service parameters configured for the side link connection.

[0226] Aspect 19: The method according to any one of aspects 15 to 18, wherein the non-access stratum layer message comprises a keep-alive message requesting the second UE to confirm that a radio link state of the side link connection is active.

[0227] Aspect 20: An apparatus for wireless communication at a first UE, comprising a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any one of aspects 1 to 14.

[0228] Aspect 21: An apparatus for wireless communication at a first UE, comprising at least one component for performing the method of any one of aspects 1 to 14.

[0229] Aspect 22: A non-transitory computer-readable medium storing a code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform the method of any one of aspects 1 to 14.

[0230] Aspect 23: An apparatus for wireless communication at a second UE, comprising a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any one of aspects 15 to 19.

[0231] Aspect 24: An apparatus for wireless communication at a second UE, comprising at least one component for performing the method of any one of aspects 15 to 19.

[0232] Aspect 25: A non-transitory computer-readable medium storing a code for wireless communication at a second UE, the code comprising instructions executable by a processor to perform the method of any one of aspects 15 to 19.

[0233] It should be noted that the methods described herein describe possible implementations, and that operations and steps may be rearranged or otherwise modified, and other implementations are possible. Furthermore, aspects from two or more methods may be combined.

[0234] The technology described herein can be used for various wireless communication systems, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA) and other systems. CDMA systems can implement radio technologies, such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. IS-2000 versions can be generally referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is generally referred to as CDMA2000 1xEV-DO, high speed packet data (HRPD), etc. UTRA includes broadband CDMA (WCDMA) and other variants of CDMA. TDMA systems can implement radio technologies, such as global system for mobile communications (GSM).

[0235] OFDMA systems can implement radio technologies such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). The technology described herein can be used for the systems and radio technologies mentioned herein as well as other systems and radio technologies. Although aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for example purposes, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable to applications other than LTE, LTE-A, LTE-A Pro, or NR applications.

[0236] A macro cell typically covers a relatively large geographic area (e.g., a radius of several kilometers) and may allow unrestricted access to a UE through a service subscription with a network provider. Compared to a macro cell, a small cell may be associated with a base station with lower power, and the small cell may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency band as a macro cell. According to various examples, a small cell may include a pico cell, a femto cell, and a micro cell. For example, a pico cell may cover a small geographic area and may allow unrestricted access to a UE through a service subscription with a network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access through a UE associated with a femto cell (e.g., a UE in a closed subscriber group (CSG), a UE for a user in a home, etc.). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or more (e.g., two, three, four, etc.) cells and may also support communications using one or more component carriers.

[0237] The wireless communication systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operation.

[0238] The information and signals described herein may be represented using any of a variety of different techniques and technologies. 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.

[0239] The various illustrative blocks and modules described in conjunction with the disclosure herein may be implemented or executed using a general purpose processor, a DSP, an ASIC, 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 an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

[0240] 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 or transmitted on a computer-readable medium as one or more instructions or codes. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hard wiring, or any combination of these. Features that implement the functions may also be physically located in various locations, including being distributed so that portions of the functions are implemented in different physical locations.

[0241] Computer readable medium includes both non-transitory computer storage medium and communication medium, and computer storage medium and communication medium include any medium that helps to transfer computer program from one place to another place.Non-transitory storage medium can be any available medium that can be accessed by general or special computer.As an example and not limitation, non-transitory computer readable medium can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, CD (CD) ROM or other optical disk storage, disk storage or other magnetic storage device or can be used for carrying or storing required program code mode in the form of instruction or data structure and can be accessed by general or special computer or general or special processor Any other non-transitory medium.In addition, any connection is appropriately referred to as computer readable medium.For example, if coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (such as infrared, radio and microwave) are used to send software from website, server or other remote source, coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology (such as infrared, radio and microwave) are included in the definition of medium. Disk and disc, as used herein, includes 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.

[0242] As used herein, including in the claims, "or" as used in a list of items (e.g., a list of items preceded by a phrase such as "at least one" or "one or more"), indicates an inclusive list, so 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). In addition, as used herein, the phrase "based on" should not be interpreted as a reference to a closed set of conditions. For example, an exemplary step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of this disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "based at least in part on."

[0243] In the drawings, similar components or features may have the same reference number. In addition, various components of the same type may be distinguished by following the reference number with a dash and a second reference that distinguishes between similar components. If only the first reference number is used in the specification, the specification applies to any one similar component having the same first reference number, regardless of the second or other subsequent reference numbers.

[0244] The descriptions set forth herein in conjunction with the accompanying drawings describe example configurations and do not represent all examples that may be implemented or within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration," rather than "preferred" or "superior to other examples." For the purpose of providing an understanding of the described technology, the detailed description includes specific details. However, the technologies may be practiced without these specific details. In some cases, in order to avoid obscuring the concepts of the described examples, known structures and devices are shown in block diagram form.

[0245] The description provided herein enables those skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but conforms to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for wireless communication at a first user equipment (UE), comprising: establishing a sidelink connection with a second UE, wherein the sidelink connection is associated with a plurality of flows; determining a radio link state of the sidelink connection based at least in part on monitoring each of the plurality of flows; based on the determination, sending a non-access stratum layer message to the second UE based at least on the radio link state of the sidelink connection; as well as sending a second message to the second UE to reconfigure one or more parameters of the side link connection, wherein reconfiguring the one or more parameters of the side link connection comprises: reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection, or reconfiguring one or more quality of service parameters configured for the side link connection.

2. The method according to claim 1, further comprising: determining that no data is communicated via a first stream of the plurality of streams; as well as The non-access stratum layer message is sent to the second UE, wherein the non-access stratum layer message includes a keep-alive message requesting the second UE to confirm that the radio link state of the sidelink connection is active.

3. The method according to claim 1, further comprising: receiving a response message from the second UE indicating that the radio link state of the sidelink connection with the second UE is active, Wherein sending a second message to the second UE to reconfigure one or more parameters of the sidelink connection is based at least in part on receiving the response message.

4. The method according to claim 1, further comprising: determining, based at least in part on a lack of a response message from the second UE, that the radio link status of the sidelink connection with the second UE comprises a radio link failure; as well as A radio link failure recovery procedure is performed based at least in part on the radio link failure to establish a second sidelink connection with the second UE.

5. The method of claim 2, wherein determining that no data is communicated comprises: It is determined that data communicated via the first flow fails to satisfy a quality of service requirement associated with the first flow.

6. The method of claim 2, wherein determining that no data is communicated comprises: It is determined that no data has been communicated via the first flow within a threshold time period associated with the first flow.

7. The method according to claim 1, further comprising: determining that no data is communicated via a first stream of the plurality of streams; determining that data is communicated via a second stream of the plurality of streams; as well as Determining the radio link state of the sidelink connection comprises a degraded radio link state, wherein sending a second message to the second UE to reconfigure one or more parameters of the sidelink connection is based at least in part on the degraded radio link state.

8. The method according to claim 1, further comprising: determining that the non-access stratum layer message is sent within a threshold time period; as well as At least based on the non-access stratum layer message, avoid sending a second non-access stratum layer message to the second UE.

9. The method of claim 1 , wherein determining the radio link state of the sidelink connection comprises: For each flow in the plurality of flows, a determination is made as to whether data communicated through each flow satisfies a quality of service requirement configured for the flow.

10. The method of claim 1, wherein the non-access stratum layer message comprises a PC5 sidelink (PC5-S) message.

11. A method for wireless communication at a second user equipment (UE), comprising: establishing a sidelink connection with a first UE, wherein the sidelink connection is associated with a plurality of flows; receiving, from the first UE, a non-access stratum layer message indicating a radio link status of the sidelink connection, wherein the non-access stratum layer message is based at least in part on a status of each of the plurality of flows at the first UE; sending a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active; receiving, based at least in part on the response message, from the first UE, a second message that reconfigures one or more parameters of the sidelink connection; as well as Reconfigure the one or more parameters of the side link connection based at least in part on the second message, wherein reconfiguring the one or more parameters of the side link connection comprises: reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection, or reconfiguring one or more quality of service parameters configured for the side link connection.

12. The method of claim 11, wherein the non-access stratum layer message comprises a keep-alive message requesting the second UE to confirm that the radio link state of the sidelink connection is active.

13. An apparatus for wireless communication at a first user equipment (UE), comprising: means for establishing a sidelink connection with a second UE, wherein the sidelink connection is associated with a plurality of flows; means for determining a radio link state of the sidelink connection based at least in part on monitoring each of the plurality of flows; means for sending a non-access stratum layer message to the second UE based on the determining, at least based on the radio link state of the sidelink connection; as well as A component for sending a second message to the second UE to reconfigure one or more parameters of the side link connection, wherein the component for sending the second message to the second UE to reconfigure one or more parameters of the side link connection includes: a component for reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection, or a component for reconfiguring one or more quality of service parameters of the side link connection.

14. The apparatus according to claim 13, further comprising: means for determining that no data is communicated via a first stream of the plurality of streams; as well as Means for sending the non-access stratum layer message to the second UE, wherein the non-access stratum layer message comprises a keep-alive message requesting confirmation from the second UE that the radio link state of the sidelink connection is active.

15. The apparatus according to claim 14, further comprising: A component for receiving a response message from the second UE indicating that the radio link state of the sidelink connection with the second UE is active, wherein the component for sending a second message to the second UE to reconfigure one or more parameters of the sidelink connection is based at least in part on receiving the response message.

16. The apparatus according to claim 14, further comprising: means for determining, based at least in part on a lack of a response message from the second UE, that the radio link status of the sidelink connection with the second UE comprises a radio link failure; as well as Means for performing a radio link failure recovery procedure based at least in part on the radio link failure to establish a second sidelink connection with the second UE.

17. The apparatus of claim 14, wherein the means for determining that no data is communicated comprises: Means for determining that data communicated via the first flow fails to satisfy a quality of service requirement associated with the first flow.

18. The apparatus of claim 14, wherein the means for determining that no data is communicated comprises: Means for determining that no data has been communicated via the first flow within a threshold time period associated with the first flow.

19. The apparatus according to claim 13, further comprising: means for determining that no data is communicated via a first stream of the plurality of streams; means for determining that data is communicated via a second stream of the plurality of streams; as well as Means for determining that the radio link state of the sidelink connection comprises a degraded radio link state, wherein the means for sending a second message to the second UE to reconfigure one or more parameters of the sidelink connection is based at least in part on the degraded radio link state.

20. The apparatus of claim 13, further comprising: means for determining that the non-access stratum layer message is sent within a threshold time period; as well as A component for avoiding sending a second non-access stratum layer message to the second UE based at least on the non-access stratum layer message.

21. The apparatus of claim 13, wherein the means for determining the radio link state of the sidelink connection comprises: Means for determining, for each flow of the plurality of flows, whether data communicated via each flow satisfies a quality of service requirement configured for the flow.

22. The apparatus of claim 13, wherein the non-access stratum layer message comprises a PC5 sidelink (PC5-S) message.

23. An apparatus for wireless communication at a second user equipment (UE), comprising: means for establishing a sidelink connection with a first UE, wherein the sidelink connection is associated with a plurality of flows; means for receiving, from the first UE, a non-access stratum layer message indicating a radio link status of the sidelink connection, wherein the non-access stratum layer message is based at least in part on a status of each of the plurality of flows at the first UE; means for sending a response message to the first UE indicating that the radio link state of the sidelink connection with the first UE is active; means for receiving, from the first UE, a second message reconfiguring one or more parameters of the sidelink connection based at least in part on the response message; as well as and a component for reconfiguring the one or more parameters of the side link connection based at least in part on the second message, wherein the component for reconfiguring the one or more parameters of the side link connection comprises: a component for reconfiguring the side link connection from a first configuration to a second configuration from a set of available configurations configured for the side link connection, or a component for reconfiguring one or more quality of service parameters configured for the side link connection.

24. The apparatus of claim 23, wherein the non-access stratum layer message comprises a keep-alive message requesting confirmation from the second UE that the radio link state of the sidelink connection is active.

25. A non-transitory computer-readable medium having one or more computer-executable instructions stored thereon, which, when executed by one or more processors of a first user equipment (UE), cause the one or more processors to perform the method according to any one of claims 1-10.

26. A non-transitory computer-readable medium having one or more computer-executable instructions stored thereon, which, when executed by one or more processors of a second user equipment (UE), cause the one or more processors to perform the method according to any one of claims 11-12.

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