Fast radio link failure recovery

Abstract

This disclosure relates to techniques for fast recovery from radio link failure in a wireless communication system. A wireless device can establish a wireless link with a cell. The wireless device can detect a radio link failure of the wireless link. The wireless device can attempt to reestablish the wireless link using a previously provided wireless link configuration. If the cell accepts the attempt to reestablish the wireless link using the previously provided wireless link configuration, the wireless link can be reestablished according to the previously provided wireless link configuration.

Description

Technical Field

[0001] This application relates to wireless communication, and more specifically to systems, apparatus, and methods for rapid recovery from radio link failures in wireless communication systems.

[0002] Related technical descriptions

[0003] The use of wireless communication systems is growing rapidly. In recent years, wireless devices such as smartphones and tablets have become increasingly sophisticated. In addition to supporting phone calls, many mobile devices (i.e., user equipment or UE) now offer access to the internet, email, text messaging, and navigation using the Global Positioning System (GPS), and are capable of operating complex applications that utilize these capabilities. Furthermore, many different wireless communication technologies and standards exist. Some examples of wireless communication standards include GSM, UMTS (e.g., associated with WCDMA or TD-SCDMA air interfaces), LTE, LTE-A (LTE-Advanced), NR, HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN or Wi-Fi), and BLUETOOTH. TM wait.

[0004] The introduction of an ever-increasing number of features and functions into wireless communication devices necessitates continuous improvement of both wireless communication and the devices themselves. Ensuring the accuracy of signals transmitted and received by user equipment (UE) devices (e.g., wireless devices such as cellular phones, base stations, and relay stations used in wireless cellular communications) is of paramount importance. Furthermore, increasing the functionality of UE devices can significantly strain their battery life. Therefore, it is equally crucial to reduce the power requirements in UE device design while allowing them to maintain good transmission and reception capabilities for improved communication. Thus, improvements are expected in this area. Summary of the Invention

[0005] This paper presents implementation schemes for apparatus, systems, and methods for rapid recovery from radio link failures in wireless communication systems.

[0006] According to the techniques described herein, when re-establishing a radio link after a radio link failure, wireless devices and cellular base stations can restore previously provided radio link configurations. These previously provided radio link configurations may include the most recently used radio link configuration prior to the radio link failure, or may include configured fallback radio link configurations, and various other possibilities. At least according to some embodiments, using such previously provided radio link configuration information when re-establishing a radio link after a radio link failure can reduce the setup time and signaling overhead associated with radio link reconstruction, thereby potentially freeing up network resources and reducing any potential interruptions to user data communications caused by RLF (Radio Link Failure).

[0007] Such fast radio link failure recovery techniques can be used when a wireless device performs radio link failure recovery on the same cell to which the wireless device was attached before the radio link failure, or potentially when performing radio link failure recovery on another cell where previously provided radio link configuration information can be retrieved from the wireless device's previous serving cell. This document also describes techniques for using previously provided radio link configuration information with modifications when performing radio link reconstruction after a radio link failure, for combining this fast radio link failure recovery process with security, and various other features and considerations that can be used when performing fast radio link failure recovery according to the techniques described herein.

[0008] It should be noted that the technologies described herein can be implemented in and / or used in several different types of devices, including but not limited to base stations, access points, mobile phones, portable media players, tablets, wearable devices, unmanned aerial vehicles, unmanned flight controllers, automobiles and / or motor vehicles, and various other computing devices.

[0009] The present invention is intended to provide a brief overview of some of the subjects described in this document. Therefore, it should be understood that the above features are merely illustrative and should not be construed as narrowing the scope or substance of the subjects described herein in any way. Other features, aspects, and advantages of the subjects described herein will become apparent from the following detailed description, drawings, and claims. Attached Figure Description

[0010] A better understanding of the subject matter can be obtained by considering the following detailed description of the various embodiments in conjunction with the accompanying drawings, in which:

[0011] Figure 1 Exemplary (and simplified) wireless communication systems according to some implementation schemes are shown;

[0012] Figure 2An exemplary base station communicating with an exemplary wireless user equipment (UE) device according to some embodiments is shown;

[0013] Figure 3 This is an exemplary block diagram of a UE according to some implementation schemes;

[0014] Figure 4 This is an exemplary block diagram of a base station according to some implementation schemes;

[0015] Figure 5 This is a flowchart illustrating various aspects of exemplary possible methods for rapid recovery from radio link failures in a wireless communication system, according to some implementation schemes;

[0016] Figure 6 This is a signal flow diagram illustrating various aspects of a possible method for reconstructing an RRC connection after an RLF, according to some implementation schemes, where the network provides complete configuration information for the new RRC connection;

[0017] Figure 7 This is a signal flow diagram illustrating possible signaling aspects that can be performed between the UE and the serving cell to prepare for a possible fast RLF recovery before the RLF actually occurs, according to some implementation schemes; and

[0018] Figures 8 to 10 This is a signal flow diagram showing further details (including signaling aspects) of possible fast RLF recovery techniques that can be performed between the UE and the serving cell after an RLF occurs, according to some implementation schemes.

[0019] While the features described herein are susceptible to various modifications and alternatives, specific embodiments thereof are illustrated by way of example in the accompanying drawings and described in detail herein. However, it should be understood that the drawings and their detailed description are not intended to limit this document to the specific forms disclosed, but rather are intended to cover all modifications, equivalents, and alternatives falling within the substance and scope of the subject matter as defined by the appended claims. Detailed Implementation

[0020] acronym

[0021] Various acronyms are used throughout this disclosure. The definitions of the most prominent acronyms that may appear throughout this disclosure are as follows:

[0022] UE: User Equipment

[0023] RF: Radio Frequency

[0024] ·BS: Base Station

[0025] GSM: Global System for Mobile Communications

[0026] UMTS: Universal Mobile Telecommunications System

[0027] LTE: Long Term Evolution

[0028] NR: New Radio

[0029] TX: Transmission

[0030] ·RX: Receive

[0031] • RAT: Radio Access Technology

[0032] • TRP: Transmitter / Receiver Point

[0033] • DCI: Downlink Control Information

[0034] • CORESET: Control Resource Set

[0035] •QCL: Quasi-cooperative localization or quasi-cooperative position

[0036] • CSI: Channel State Information

[0037] • CSI-RS: Channel State Information Reference Signal

[0038] • CSI-IM: Channel State Information Interference Management

[0039] •CMR: Channel Measurement Resources

[0040] •IMR: Interference Measurement Resources

[0041] ZP: Zero Power

[0042] • NZP: Non-zero power

[0043] • CQI: Channel Quality Indicator

[0044] • PMI: Precoding Matrix Indicator

[0045] ·RI: Rank Indicator

[0046] the term

[0047] The following is a glossary of terms that will appear in this disclosure:

[0048] Memory media—any device of any type of nontransitory memory device or storage device. The term "memory media" is intended to include mounting media such as CD-ROMs, floppy disks, or magnetic tape devices; computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory such as flash memory, magnetic media, e.g., hard disk drives or optical storage devices; registers or other similar types of memory elements, etc. Memory media may also include other types of nontransitory memory or combinations thereof. Furthermore, memory media may reside in a first computer system executing a program, or may reside in a different second computer system connected to the first computer system via a network such as the Internet. In a later example, the second computer system may provide program instructions to the first computer system for execution. The term "memory media" may include two or more memory media that may reside in different locations on different computer systems connected via a network, for example. Memory media may store program instructions (e.g., representing a computer program) that can be executed by one or more processors.

[0049] Carrier medium—the memory medium as described above, and physical transmission medium, such as buses, networks and / or other physical transmission media for transmitting signals (such as electrical signals, electromagnetic signals or digital signals).

[0050] Computer system (or computer) — any of the various types of computing or processing systems, including personal computer systems (PCs), mainframe computer systems, workstations, network appliances, internet-connected appliances, personal digital assistants (PDAs), television systems, grid computing systems, or other devices or combinations thereof. Generally, the term "computer system" can be broadly defined as any device (or combination of devices) that includes at least one processor that executes instructions from a memory medium.

[0051] User equipment (UE) (or “UE device”) — any of various types of computer systems or devices that are mobile or portable and perform wireless communication. Examples of UE devices include mobile phones or smartphones (e.g., iPhone). TM Based on Android TM Phones), tablets (e.g., iPads) TM Samsung Galaxy TM ), portable gaming devices (e.g., Nintendo DS) TM PlayStation Portable TM Gameboy Advance TM iPhone TMThis includes wearable devices (e.g., smartwatches, smart glasses), laptops, PDAs, portable internet devices, music players, data storage devices, other handheld devices, automobiles and / or motor vehicles, unmanned aerial vehicles (UAVs) (e.g., drones), UAV controllers (UACs), etc. Generally speaking, the term "UE" or "UE device" can be broadly defined to encompass any electronic device, computing device, and / or telecommunications device (or a combination of these devices) that is easily transportable by the user and capable of wireless communication.

[0052] A wireless device is any of various types of computer systems or devices that perform wireless communication. A wireless device can be portable (or mobile), or it can be stationary or fixed in a location. A UE is an example of a wireless device.

[0053] A communication device is any of various types of computer systems or devices that perform communication, which may be wired or wireless. A communication device may be portable (or mobile), or it may be stationary or fixed in a location. A wireless device is one example of a communication device. A UE is another example of a communication device.

[0054] Base station (BS) — The term “base station” has the full range of its usual meaning and includes at least a wireless communication station that is installed in a fixed location and used for communication as part of a wireless telephone system or radio system.

[0055] A processing element (or processor) is a component or combination of components capable of performing the functions of a device (such as a user equipment device or a cellular network device). A processing element may include, for example: a processor and associated memory, portions or circuitry of individual processor cores, an entire processor core, a processor array, circuitry such as an ASIC (Application-Specific Integrated Circuit), programmable hardware components such as a Field-Programmable Gate Array (FPGA), and any combination thereof.

[0056] Wi-Fi—The term “Wi-Fi” encompasses the full range of its common meaning and includes at least wireless communication networks, or RATs, which are provided by and through wireless LAN (WLAN) access points to provide connectivity to the Internet. Most modern Wi-Fi networks (or WLAN networks) are based on the IEEE 802.11 standard and are marketed under the name “Wi-Fi.” Wi-Fi (WLAN) networks are distinct from cellular networks.

[0057] Automatic—means an action or operation performed by a computer system (e.g., software executed by the computer system) or device (e.g., circuits, programmable hardware elements, ASICs, etc.) without requiring direct user input to specify or perform that action or operation. Therefore, the term "automatic" contrasts with an action performed or specified manually by a user, where the user provides input to directly perform that action. An automatic process can be initiated by user-provided input, but the subsequent actions performed "automatically" are not specified by the user; that is, they are not performed "manually," where the user specifies each action to be performed. For example, a user filling out a form by selecting each field and providing input to specify information (e.g., by typing information, selecting a checkbox, radio selection, etc.) is considered manually filling out the form, even though the computer system must update the form in response to the user's actions. The form can be automatically filled out by a computer system (e.g., software executed on the computer system) which analyzes the fields of the form and fills it out without any user input specifying answers for the fields. As indicated above, the user can invoke the automatic filling of the form but does not participate in the actual filling of the form (e.g., the user does not manually specify answers for the fields, but they are completed automatically). This manual provides various examples of operations that are automatically performed in response to actions taken by the user.

[0058] "Configured as"—Various components can be described as being "configured as" to perform one or more tasks. In such contexts, "configured as" is a broad expression generally meaning "having" a "structure" that performs one or more tasks during operation. Thus, a component can be configured to perform a task even when it is not currently performing one (e.g., a set of electrical conductors can be configured to electrically connect one module to another, even when the two modules are not connected). In some contexts, "configured as" can also be a broad expression generally meaning a structure that "has" a "circuit" that performs one or more tasks during operation. Thus, a component can be configured to perform a task even when it is not currently powered on. Typically, the circuit forming the structure corresponding to "configured as" can include hardware circuitry.

[0059] For ease of description, various components may be described as performing one or more tasks. Such descriptions shall be interpreted as including the phrase “configured to”. The statement that a component is configured to perform one or more tasks is expressly intended not to invoke the interpretation of paragraph 6 of section 112 of title 35 of the United States Code.

[0060] Figure 1 and Figure 2 -Exemplary communication system

[0061] Figure 1 Exemplary (and simplified) wireless communication systems that can implement various aspects of this disclosure according to some embodiments are shown. It should be noted that... Figure 1 The system described is merely one example of a possible system, and this implementation can be carried out in any of a variety of systems as needed.

[0062] As shown in the figure, this exemplary wireless communication system includes a base station 102 that communicates with one or more (e.g., any number) user equipments 106A, 106B, etc., up to 106N, via a transmission medium. Each user equipment may be referred to herein as a "user equipment" (UE) or UE device. Therefore, user equipment 106 is referred to as a UE or UE device.

[0063] Base station 102 may be a transceiver base station (BTS) or a cell site, and may include hardware and / or software for implementing wireless communication with UEs 106A to 106N. If base station 102 is implemented in an LTE environment, it may be referred to as an "eNodeB" or "eNB". If base station 102 is implemented in a 5G NR environment, it may alternatively be referred to as a "gNodeB" or "gNB". Base station 102 may also be equipped to communicate with network 100 (e.g., the core network of a cellular service provider, telecommunications networks such as the Public Switched Telephone Network (PSTN), and / or the Internet, and various other possible networks). Therefore, base station 102 facilitates communication between user equipments and / or between user equipments and network 100. The communication area (or coverage area) of a base station may be referred to as a "cell". Also as used herein, with respect to a UE, a base station may sometimes be considered to represent the network, taking into account both uplink and downlink communication of the UE. Therefore, a UE communicating with one or more base stations in the network may also be understood as a UE communicating with the network.

[0064] Base station 102 and user equipment can be configured to communicate via a transmission medium using any of a variety of radio access technologies (RATs), also known as wireless communication technologies or telecommunications standards, such as GSM, UMTS (WCDMA), LTE, LTE-A Advanced, LAA / LTE-U, 5G NR, 3GPP2, CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, etc.

[0065] Base station 102 and other similar base stations operating according to the same or different cellular communication standards may thus provide, as one or more cell networks, continuous or near-continuous overlapping services to UE 106 and similar devices over a geographic area via one or more cellular communication standards.

[0066] It should be noted that UE 106 can communicate using multiple wireless communication standards. For example, UE 106 can be configured to communicate using either or both of the 3GPP cellular communication standards or the 3GPP2 cellular communication standards. In some implementations, UE 106 can be configured to perform techniques for rapid recovery from radio link failures in a wireless communication system, such as the various methods described herein. UE 106 can also be configured, or alternatively configured, to use WLAN, BLUETOOTH, etc. TM It can communicate with one or more Global Navigation Satellite Systems (GNSS, such as GPS or GLONASS), one and / or more mobile television broadcasting standards (e.g., ATSC-M / H), etc. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0067] Figure 2 An exemplary user equipment 106 (e.g., one of devices 106A to 106N) communicating with base station 102 according to some embodiments is illustrated. UE 106 can be a device with wireless network connectivity, such as a mobile phone, handheld device, wearable device, computer or tablet, unmanned aerial vehicle (UAV), unmanned flight controller (UAC), automobile, or virtually any type of wireless device. UE 106 may include a processor (processing element) configured to execute program instructions stored in memory. UE 106 can perform any of the method embodiments of the present invention by executing such stored instructions. Alternatively or additionally, UE 106 may include programmable hardware elements, such as any of an FPGA (Field Programmable Gate Array), integrated circuit, and / or various other possible hardware components configured to perform (e.g., individually or in combination) any of or any portion of any of the method embodiments described herein. UE 106 may be configured to communicate using any of a plurality of wireless communication protocols. For example, UE 106 can be configured to communicate using two or more of CDMA2000, LTE, LTE-A, 5G NR, WLAN, or GNSS. Other combinations of wireless communication standards are also possible.

[0068] UE 106 may include one or more antennas communicating using one or more wireless communication protocols according to one or more RAT standards. In some embodiments, UE 106 may share one or more portions of the receive chain and / or transmit chain among multiple wireless communication standards. The shared radio components may include a single antenna, or may include multiple antennas for performing wireless communication (e.g., for MIMO). Typically, the radio components may include any combination of baseband processors, analog radio frequency (RF) signal processing circuitry (e.g., including filters, mixers, oscillators, amplifiers, etc.), or digital processing circuitry (e.g., for digital modulation and other digital processing). Similarly, the radio components may use the aforementioned hardware to implement one or more receive chains and transmit chains.

[0069] In some implementations, UE 106 may include separate transmit and / or receive chains (e.g., including separate antennas and other radio components) for each wireless communication protocol configured to communicate therewith. As another possibility, UE 106 may include one or more radio components shared among multiple wireless communication protocols, as well as one or more radio components uniquely used by a single wireless communication protocol. For example, UE 106 may include shared radio components for communication using either LTE or CDMA2000 1xRTT (or LTE or NR, or LTE or GSM), and for communication using Wi-Fi and BLUETOOTH. TM Each component communicates independently. Other configurations are also possible.

[0070] Figure 3 - Block diagram of an exemplary UE device

[0071] Figure 3A block diagram of an exemplary UE 106 according to some embodiments is shown. As shown, UE 106 may include a System-on-Chip (SOC) 300, which may include parts for various purposes. For example, as shown, SOC 300 may include a processor 302 capable of executing program instructions for UE 106, and display circuitry 304 capable of performing graphics processing and providing display signals to a display 360. SOC 300 may also include sensor circuitry 370, which may include components for sensing or measuring any of a variety of possible characteristics or parameters of UE 106. For example, sensor circuitry 370 may include motion sensing circuitry configured to detect motion of UE 106, for example, using a gyroscope, accelerometer, and / or any of a variety of other motion sensing components. As another possibility, sensor circuitry 370 may include one or more temperature sensing components, for example, for measuring the temperature of each of one or more antenna panels and / or other components of UE 106. Any of a variety of other possible types of sensor circuitry may also or alternatively be included in UE 106 as needed. Processor 302 may also be coupled to memory management unit (MMU) 340, which may be configured to receive addresses from processor 302 and translate those addresses into locations in memory (e.g., memory 306, read-only memory (ROM) 350, NAND flash memory 310) and / or other circuitry or devices, such as display circuitry 304, radio components 330, connector I / F 320, and / or display 360. MMU 340 may be configured to perform memory protection and page table translation or setup. In some embodiments, MMU 340 may be included as part of processor 302.

[0072] As shown in the figure, the SOC 300 can be coupled to various other circuits of the UE 106. For example, the UE 106 may include various types of memory (e.g., including NAND flash memory 310), connector interface 320 (e.g., for coupling to computer systems, docking stations, charging stations, etc.), display 360, and wireless communication circuitry 330 (e.g., for LTE, LTE-A, NR, CDMA2000, BLUETOOTH). TM(e.g., Wi-Fi, GPS, etc.). UE device 106 may include at least one antenna (e.g., 335a) and may include multiple antennas (e.g., shown by antennas 335a and 335b) for performing wireless communication with base stations and / or other devices. Antennas 335a and 335b are shown by way of example, and UE device 106 may include fewer or more antennas. In general, one or more antennas are collectively referred to as antenna 335. For example, UE device 106 may use antenna 335 to perform wireless communication via radio circuitry 330. As described above, in some embodiments, the UE may be configured to use multiple wireless communication standards for wireless communication.

[0073] UE 106 may include hardware and software components, such as those described further herein, for implementing techniques for rapid recovery from radio link failures in a wireless communication system. The processor 302 of UE device 106 may be configured to implement some or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). In other embodiments, processor 302 may be configured as a programmable hardware element, such as an FPGA (Field-Programmable Gate Array) or as an ASIC (Application-Specific Integrated Circuit). Furthermore, as... Figure 3 As shown, processor 302 may be coupled to and / or interoperable with other components to perform techniques for rapid recovery from radio link failures in a wireless communication system, according to various embodiments disclosed herein. Processor 302 may also implement various other applications and / or end-user applications running on UE 106.

[0074] In some implementations, radio component 330 may include a separate controller dedicated to controlling communications for various corresponding RAT standards. For example, such as Figure 3 As shown, the radio component 330 may include a Wi-Fi controller 352, a cellular controller (e.g., an LTE and / or LTE-A controller) 354, and a BLUETOOTH controller. TM Controller 356, and in at least some embodiments, one or more of these controllers may be implemented as corresponding integrated circuits (referred to as ICs or chips), which communicate with each other and with the SOC 300 (more specifically with the processor 302). For example, Wi-Fi controller 352 may communicate with cellular controller 354 via a cell-ISM link or WCI interface, and / or BLUETOOTH TMController 356 can communicate with cellular controller 354 via a cell-ISM link or the like. Although three separate controllers are shown within radio component 330, other implementations with fewer or more similar controllers for various different RATs can be implemented in UE device 106.

[0075] Furthermore, implementation schemes in which the controller can perform functions associated with various radio access technologies are envisioned. For example, according to some implementation schemes, in addition to hardware and / or software components for performing cellular communications, the cellular controller 354 may also include hardware and / or software components for performing one or more activities associated with Wi-Fi, such as Wi-Fi preamble detection, and / or the generation and transmission of Wi-Fi physical layer preamble signals.

[0076] Figure 4 - Block diagram of an exemplary base station

[0077] Figure 4 A block diagram of an exemplary base station 102 according to some implementation schemes is shown. It should be noted that... Figure 4 The base station shown is merely one example of a possible base station. As illustrated, base station 102 may include a processor 404 capable of executing program instructions specific to base station 102. Processor 404 may also be coupled to a memory management unit (MMU) 440 or other circuitry or device, which may be configured to receive addresses from processor 404 and translate those addresses into locations in memory (e.g., memory 460 and read-only memory (ROM) 450).

[0078] Base station 102 may include at least one network port 470. Network port 470 may be configured to be coupled to a telephone network and provide access rights as described above. Figure 1 and Figure 2 The telephone network described herein includes multiple devices such as UE device 106. Network port 470 (or an additional network port) may also be configured, or alternatively configured, to be coupled to a cellular network, such as the core network of a cellular service provider. The core network may provide mobility-related services and / or other services to multiple devices such as UE device 106. In some cases, network port 470 may be coupled to the telephone network via the core network, and / or the core network may provide the telephone network (e.g., in other UE devices served by the cellular service provider).

[0079] Base station 102 may include at least one antenna 434 and possibly multiple antennas. One or more antennas 434 may be configured to operate as a wireless transceiver and may be further configured to communicate with UE device 106 via radio component 430. Antenna 434 communicates with radio component 430 via communication link 432. Communication link 432 may be a receive link, a transmit link, or both. Radio component 430 may be designed to communicate via various wireless telecommunication standards, including but not limited to NR, LTE, LTE-A WCDMA, CDMA2000, etc. Processor 404 of base station 102 may be configured to implement and / or support implementation of some or all of the methods described herein, for example by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively, processor 404 may be configured as a programmable hardware element such as a FPGA (Field-Programmable Gate Array), or as an ASIC (Application-Specific Integrated Circuit), or a combination thereof. In the case of certain RATs (e.g., Wi-Fi), base station 102 can be designed as an access point (AP), in which case network port 470 can be implemented to provide access to a wide area network and / or one or more local area networks, for example it may include at least one Ethernet port, and radio component 430 can be designed to communicate according to the Wi-Fi standard.

[0080] Figure 5 —Fast radio link failure recovery

[0081] Generally speaking, radio link monitoring can be an important part of cellular communication technology and wireless communication. In at least some cellular communication standards, this monitoring can lead to the detection of a radio link failure (RLF) in scenarios where the radio link portion of the cellular link between a wireless device and the cellular network becomes unreliable. When an RLF is detected, techniques for recovering from the RLF can be provided, for example, to facilitate the wireless device regaining a reliable radio link with the cellular network.

[0082] Because RLF can occur in a variety of scenarios and situations, in at least some instances, RLF recovery techniques may include completely reconfiguring the radio resource control (RRC) connection between the radio device and its serving cellular base station (e.g., the one providing the primary cell or PCell for the radio device). This can provide significant flexibility in how the radio device is configured after an RLF, but it can introduce significant signaling overhead and setup time for restoring the RRC connection. However, there are situations where the radio device can directly revert to its previously provided RRC configuration, potentially reducing the overhead and setup time for rebuilding the radio link with the serving cell of the radio device. This, in turn, can reduce service interruptions to the radio device and improve perceived user experience. For example, in scenarios such as temporary (e.g., brief) periods when a radio device loses its radio link, such as when riding an elevator, traveling through a tunnel, or briefly entering a basement with poor cellular reception, and various other possibilities, the radio device can restore the RRC configuration used before the RLF.

[0083] Therefore, it would be beneficial to provide techniques for rapidly recovering from radio link failures by rebuilding the radio link using previously provided configuration information. To illustrate a group of such possible techniques, Figure 5 This is a flowchart illustrating, according to at least some embodiments, a method for rapid recovery from radio link failure in a wireless communication system.

[0084] Figure 5 The aspects of the method may be implemented by wireless devices and / or cellular base stations (such as UE 106 and BS 102 shown and described in the various figures herein), or more generally, may be implemented as needed in combination with any of the computer circuits, systems, devices, elements or components, etc., shown in the above figures. For example, the processor (and / or other hardware) of such devices may be configured to cause the devices to perform any combination of the illustrated method elements and / or other method elements.

[0085] It should be noted that, although the description uses methods involving the use of communication technologies and / or features associated with 3GPP and / or NR specification documents, Figure 5 This method describes at least some elements, but this description is not intended to limit this disclosure and can be used in any suitable wireless communication system as needed. Figure 5 The method encompasses various aspects. In various implementation schemes, some elements of the method shown may be performed simultaneously in a different order than those shown, may be replaced by other method elements, or may be omitted. Additional method elements may also be performed as needed. As shown in the figure, Figure 5 The method can be operated as follows.

[0086] In section 502, a wireless device can establish a radio link with a cellular base station. According to some implementations, the radio link may include a 5G NR-based cellular link. For example, the wireless device may establish a session with an AMF entity of the cellular network via one or more gNBs that provide radio access to the cellular network. Alternatively, the radio link may include an LTE-based cellular link. For example, the wireless device may establish a session with a mobility management entity of the cellular network via an eNB that provides radio access to the cellular network. Other types of cellular links are also possible according to various implementations, and the cellular network may also, or alternatively, operate according to another cellular communication technology (e.g., UMTS, CDMA2000, GSM, etc.).

[0087] Establishing a radio link may include, according to at least some implementations, establishing an RRC connection with a serving cellular base station. Establishing an RRC connection may include configuring various parameters for communication between the radio device and the cellular base station, establishing environmental information for the radio device, and / or any of various other possible characteristics, such as establishing an air interface for the radio device to communicate with a cellular network associated with the cellular base station. After establishing an RRC connection, the radio device may operate in an RRC connected state. In some instances, the RRC connection may also be released (e.g., after a period of inactivity relative to data communication), in which case the radio device may operate in an RRC idle state or an RRC inactive state. In some cases, such as due to radio device mobility, changes in radio medium conditions, and / or any other various possible reasons, the radio device may perform a handover (e.g., when in RRC connected mode) or cell reselection (e.g., when in RRC idle mode or RRC inactive mode) to a new serving cell.

[0088] According to at least some implementations, a wireless device can establish multiple wireless links, for example, with multiple TRPs in a cellular network, based on a multi-TRP configuration. In such scenarios, the wireless device may be configured (e.g., via RRC signaling) to have one or more Transmission Control Indicators (TCIs), which may correspond to various beams available for communication with the TRPs. Furthermore, there may be situations where one or more configured TCI states can be activated at a specific time by the wireless device's Media Access Control (MAC) control element (CE).

[0089] In at least some cases, establishing a wireless link may include the wireless device providing information about its capabilities. This capability information may include information related to any one of a variety of wireless device capabilities.

[0090] According to some implementations, a cellular base station may indicate to a wireless device that the cellular base station (or a cellular network associated with the cellular base station, or at least a portion of the cellular base station, such as a specific group of cellular base stations) supports the Fast Radio Link Failure (RLF) recovery feature. The Fast RLF recovery feature allows the wireless device to request the reconstruction of the radio link using previously provided radio link configuration information. For example, at least as a possibility, when reconstructing an RRC connection based on this feature after an RLF, a previously provided RRC configuration, such as the most recent RRC configuration used between the wireless device and the cellular base station before the RLF, can be restored. The indication of support for the Fast RLF recovery feature may be provided in broadcast system information (e.g., a System Information Block (SIB)), or as part of the RRC configuration information for the wireless device, and various other possibilities. In some instances, additionally or alternatively, the wireless device may indicate support for this feature to the cellular base station, for example, by including a support flag for the feature in the wireless device capability information provided from the wireless device to the cellular base station.

[0091] In some instances, a cellular base station may provide radio devices with a default or fallback radio link configuration that can be used according to this fast RLF recovery feature. For example, according to various implementations, the fallback RRC configuration may be provided when the RRC connection is initially established and / or may be configured or reconfigured after the RRC connection has been established. This fallback radio link configuration may apply only to the currently serving cellular base station (e.g., which provides the fallback radio link configuration) or may apply to multiple cells. At least in some instances, an indication may be provided to radio devices in one or more cells that the fallback radio link configuration is available for fast RLF recovery.

[0092] Cellular base stations can provide wireless devices with timer configuration information for a timer associated with the Fast RLF Recovery feature. For example, this timer configuration information can indicate the length of the Fast RLF Recovery Availability Timer available to the wireless device. This timer can be started by the wireless device when an RLF is detected, and the duration for which the Fast RLF Recovery feature remains available after the RLF can be controlled. For example, the wireless device can be configured not to attempt to use the Fast RLF Recovery feature if the Fast RLF Recovery Availability Timer expires.

[0093] In 504, the wireless device can detect the RLF (Recovery Link Failure). Detecting an RLF may include determining that one or more (e.g., specified and / or configured) triggers for the RLF have occurred. As a possibility, such triggers may include multiple consecutive instances of out-of-sync occurring (e.g., as part of radio link monitoring performed by the wireless device) exceeding a configured threshold. Other mechanisms for detecting RLFs and / or the types of triggers for RLFs are also possible. If configured, the wireless device may initiate a fast RLF recovery availability timer based on the detection of the wireless device's RLF.

[0094] In 506, a wireless device may attempt to rebuild the wireless link using previously provided wireless link configuration information. Attempting to rebuild the wireless link may include transmitting a request to the cellular base station to rebuild the wireless link (such as an RRC rebuild request). This request may include a portion of the wireless device's indication of its preference for using the previously provided wireless link configuration information.

[0095] It is possible that the wireless device may attempt to rebuild the wireless link using previously provided wireless link configuration information based on any of several considerations. For example, the wireless device may perform cell selection to determine which cell to attempt to rebuild the wireless link with, and may determine whether to attempt to rebuild the wireless link using previously provided wireless link configuration information based at least in part on the cell selected for the wireless link rebuilding attempt. For example, as one possibility, if the selected cell is the same cell on which the RLF occurred, the wireless device may determine to attempt to rebuild the wireless link using previously provided wireless link configuration information based at least in part on selecting the same cell on which the RLF occurred. As another possibility, if fallback wireless link configuration information has been provided for a cell group, and if a cell in that cell group is selected, the wireless device may determine to attempt to rebuild the wireless link using previously provided wireless link configuration information based at least in part on selecting a cell in that cell group. If such a timer is configured, another exemplary consideration may include the conditions of a fast RLF recovery availability timer. For example, if such a timer is configured and the timer has not expired, the wireless device can determine, at least in part, to attempt to rebuild the wireless link using the previously provided wireless link configuration information, based on the fact that the timer has not expired.

[0096] A cellular base station may, in response to a request from a wireless device to use previously configured radio link configuration information or an indication from the wireless device of its preference for using such information, similarly determine, based on any of several considerations, whether to use the previously provided radio link configuration information to rebuild the radio link. In some instances, the cellular base station may identify the wireless device based on information provided in the request to rebuild the radio link, such as a Short Message Authentication Code-Integrity (ShortMAC-I) or an Inactive Radio Network Temporary Identifier (I-RNTI), and may determine, at least in part, based on the wireless device's identification information, whether to continue using the previously configured radio link configuration information to rebuild the radio link. The cellular base station may determine whether the previously provided radio link configuration information is available to the cellular base station. For example, the cellular base station may determine whether the configuration information for the wireless device prior to the RLF occurred was stored by the cellular base station or has been refreshed. As another example, the cellular base station may determine whether the configuration information for the wireless device prior to the RLF occurred can be retrieved from another cellular base station in the cellular network using the wireless device's I-RNTI information.

[0097] If a cellular base station determines that it will not use previously provided radio link configuration information to rebuild the radio link, it may transmit an instruction to the radio device to rebuild the radio link using a new radio link configuration (e.g., an RRC rebuild message). In this case, the cellular base station may also provide the radio device with the new radio link configuration information, for example, in an RRC reconfiguration message.

[0098] If a cellular base station determines that it will use previously provided radio link configuration information to rebuild the radio link, it may transmit an instruction to the radio device to rebuild the radio link using the previously provided radio link configuration (e.g., an RRC rebuild or RRC reply message). In this case, the cellular base station may not need to provide the radio link configuration information to the radio device (e.g., an RRC reconfiguration message may not be required), which reduces the setup time and signaling overhead for rebuilding the radio link compared to a scenario where the radio link is reconfigured.

[0099] In some instances, cellular base stations may be able to rebuild radio links using previously provided radio link configuration information with some modifications. For example, a cellular base station may provide incremental configuration to radio devices. The incremental configuration information may indicate changes in the radio link configuration relative to the previously provided radio link configuration. At least according to some implementations, this approach allows cellular networks to configure radio links more flexibly when rebuilding is performed after an RLF (Rebuildable Radio Link Request), while still potentially reducing setup time and signaling overhead.

[0100] In some instances, wireless devices and cellular base stations can effectively recover the radio link after a Regression Link Request (RLF) using previously provided configuration information, including the immediate ability to restore the security context of the radio link. For example, when a cellular base station instructs the use of previously provided radio link configuration information to rebuild the radio link, the wireless device can perform a horizontal key derivation to derive a key using the same next-hop chain count (NCC) from the radio link configuration prior to the RLF for encryption and integrity protection. Alternatively or additionally, the cellular base station can provide security information to the wireless device to support the security context for rebuilding the radio link. For example, when a cellular base station instructs the use of previously provided radio link configuration information to rebuild the radio link, the NCC of the radio link can be provided, and the wireless device can use the provided NCC to derive a key (e.g., K*gNB) for encryption and integrity protection.

[0101] As a possibility, previously provided radio link configuration information may include the most recently provided and acknowledged configuration information prior to an RLF (Recurrent Link Default). For example, if a radio device has transmitted an RRC (Recurrent Reconfiguration Complete) message back to the network, the previously provided radio link configuration information may be based on the most recent RRC reconfiguration message received by the radio device from the cellular network. At least in some instances, if the cellular base station provides RRC reconfiguration to the radio device when it is unable to provide an RRC reconfiguration complete message and / or the cellular base station has not received an RRC reconfiguration complete message from the radio device (e.g., due to an RLF), the RRC configuration for the radio device prior to the acknowledgment of the RRC reconfiguration may be used as the previously provided radio link configuration information. Alternatively, in some instances, if there is any ambiguity regarding what the most recent radio link configuration is (e.g., if the cellular network does not receive an RRC reconfiguration complete message in response to its latest RRC configuration message), the cellular base station may determine to provide fresh configuration information to configure the radio link, rather than using the previously provided radio link configuration information when rebuilding the radio link.

[0102] As another possibility, the previously provided radio link configuration information may include a fallback or default radio link configuration. For example, as previously noted, in some instances, before an RLF occurs, such as when an RRC connection is initially established, the cellular base station may be configured with a fallback RRC configuration for fast RLF recovery. In this scenario, the fallback radio link configuration can be used to rebuild the radio link.

[0103] Once the radio link has been re-established, the radio equipment and cellular base station can resume transmitting data and / or signaling over the radio link (e.g., on one or more signaling radio bearers and / or data radio bearers re-established using previously provided radio link configuration information).

[0104] Therefore, at least according to some implementation schemes, at least in some instances, Figure 5 The method can be used to quickly recover from radio link failures caused by wireless devices temporarily going out of range, which can potentially reduce the duration of cellular communication outages caused by such events and thereby improve the user experience.

[0105] Figures 6 to 10 and additional information

[0106] Figures 6 to 10 It shows that it can be combined if needed. Figure 5 Another aspect of the method used. However, it should be noted that in Figures 6 to 10 Shown and about Figures 6 to 10 The exemplary details described are not intended to limit this disclosure as a whole: many variations and alternatives to the details provided below are possible and should be considered within the scope of this disclosure.

[0107] In 3GPP-based cellular communication systems, a Radio Link Failure (RLF) may occur for a UE that is unable to communicate effectively with its serving cellular base station. According to at least some implementations, when a cellular link with the base station is established and used (or at least becomes available), the UE can monitor the radio link, including periodically determining whether the UE and the cellular base station are synchronized or out of sync, and declaring an RLF if a configured or specified number of out-of-sync instances occur consecutively. In at least some instances, a UE experiencing an RLF may attempt to perform RLF recovery, trying to rebuild the cellular link to minimize any interruption to cellular service.

[0108] In many RLF scenarios, a UE can temporarily exit communication (OOC) and select a previous primary cell (PCell) to restore cellular connectivity. For example, some common situations where a UE can enter OOC for a short period of time and then be able to restore cellular connectivity on the same primary cell may include when the UE enters an elevator, is carried into a basement with poor signal strength, or enters a tunnel (e.g., in a motor vehicle).

[0109] Existing connection rebuilding and reconfiguration procedures can be designed to initiate a new connection that may include a significant amount of connection setup and configuration signaling, during which user plane data services may be suspended. For example, in some instances, in NR, connection rebuilding and reconfiguration after an RLF may take up to 29 ms, while in LTE, such a procedure may take up to 28 ms. Other time lengths are also possible in various scenarios. In scenarios where a cellular link from the same cell that provided service before the RLF can be rebuilt, contextual information from the previous connection can be utilized to reduce the setup time for connection rebuilding. For example, techniques could be provided where, when a Radio Resource Control (RRC) connection is rebuilt after an RLF, the UE and the cellular base station agree to restore the previous configuration instead of exchanging RRC reconfiguration messages to provide a completely new configuration (e.g., one that may still be the same as or significantly overlap with the configuration of the previous connection).

[0110] Figure 6 This is a signal flow diagram illustrating various aspects of a possible method for re-establishing an RRC connection after an RLF (Reconnection-Reset Failure) according to some implementation schemes, where the network provides complete configuration information for the new RRC connection. As shown, the signal flow can be performed between cellular device 602 (e.g., UE) and cell (“cell #x”) 604 of the cellular network. In 606, cellular device 602 and cell 604 can establish and operate in RRC connection mode. In 608, the cellular device can detect a radio link failure. In 610, cellular device 602 can initiate connection re-establishment and release connection mode configuration information (e.g., configuration information for any secondary cells). In 612, cellular device 602 can perform cell selection for connection re-establishment, for example, based on signal strength and / or signal quality measurements of one or more cells near cellular device 602. Cell selection can cause cellular device 602 to select cell 604 on which to perform connection re-establishment. In step 614, cellular device 602 may prepare to send an RRC rebuild request, potentially including applying L1 and Media Access Control (MAC) default configurations (e.g., as configured by the network and / or specified in the 3GPP specification). In step 616, cellular device 602 may provide the RRC rebuild request to cell 604. In step 618, cell 604 may provide an RRC rebuild message to cellular device 602. In step 620, cellular device 602 may provide an RRC rebuild complete message to cell 604. In step 622, cell 604 may provide an RRC reconfiguration message to cellular device 602. In step 624, cellular device 602 may provide an RRC reconfiguration complete message to cell 604. User plane data communications that may have been suspended due to RLF can resume at this stage.

[0111] exist Figure 6In this scenario, after releasing the existing configuration, the UE can rely on the network to provide a new configuration. In contrast, if the UE maintains the configuration after the RLF (e.g., including security information, resource block (RB) allocation, SCell configuration information), it can restore the RRC connection more quickly (e.g., if the restoration is on the same cell for which it maintained the configuration) and potentially reduce signaling overhead and latency.

[0112] For example, the UE and cell may maintain the RRC reconfiguration procedure but may skip the RRC reconfiguration portion of the RRC connection reconfiguration. If the UE selects the same PCell as before the RLF in the RRC reconfiguration request (e.g., using signaling radio bearer 0 (SRB0)), the UE may indicate to the network that the UE can and prefers to restore from the stored configuration. If the network agrees, the network may retrieve the UE context (if possible) and send a reconfiguration message (which may also be referred to as message 4) (e.g., using SRB1), thereby commanding the UE to restore the previous configuration (e.g., including the security context). The UE may restore the previous configuration and restore SRB2 and any data radio bearers (DRBs). The UE may send an RRC reconfiguration complete message (which may also be referred to as message 5) to indicate success. In this scenario, no further RRC reconfiguration procedure is required. It should be noted that if the UE selects a different cell, or if the network does not agree to restore the previous configuration in message 4, the UE may release the configuration (e.g., according to 3GPP TS 38.331 5.3.7.2, as one possibility) and follow the network reconfiguration procedure, including RRC connections (e.g., according to 3GPP TS38.331 5.3.7.5, as one possibility).

[0113] This approach is relatively network-friendly because the network can control whether to continue using this simplified RLF recovery with stored configuration information or to perform an RLF recovery using configuration from scratch. When using simplified RLF recovery, the overhead of exchanging RRC reconfiguration messages between the UE and PCell can be saved, thereby saving potential RRC processing delays and / or potentially reducing RRC transmission latency (e.g., compared to situations where RRC rebuild requests / reconfigurations are not combined / multiplexed in the downlink).

[0114] Figure 7This is a signal flow diagram illustrating further possible details (including signaling aspects) of a method, according to some implementations, that can be performed between the UE and the serving cell to prepare for a possible fast RLF recovery before an actual RLF occurs. As shown, signal flow can be performed between UE 702 and cell 704 of the cellular network. In 706, UE 702 and cell 704 may be in RRC connected mode. In 708, cell 704 may provide an RRC reconfiguration message to UE 702. The RRC reconfiguration message may include an indication to enable the fast RLF recovery feature and may indicate a timer value (“t3xx”) that limits the time window during which the UE can use the fast RLF recovery feature. In 710, UE 702 may provide an RRC reconfiguration complete message to cell 704, thereby confirming the reconfiguration. It should be noted that either or both of the indication to enable the fast RLF recovery feature and the timer may alternatively or additionally be indicated in system information broadcast by cell 704 (e.g., in a System Information Block (SIB)). This timer may also not be used at UE 702, for example because the network may be able to reject the UE's request to use the fast RLF recovery feature based on the obsolescence of the stored configuration and / or for any of a variety of other possible reasons.

[0115] In 712, UE 702 can detect an RLF. In 714, UE 702 can start a configured timer T3XX for fast RLF recovery based on a configured timer value t3xx. In 716, UE 702 can initiate connection re-establishment and can store, rather than release, the configuration of the previous connection. In 718, UE 702 can perform cell selection for connection re-establishment, for example, based on signal strength and / or signal quality measurements of one or more cells near UE 702. Cell selection may cause UE 702 to select cell 704 on which to perform connection re-establishment. In 720, UE 702 can apply the L1 and MAC default configurations. In 722, UE 702 and cell 704 can transmit a Random Access Channel (RACH) message and a Random Access Response (RAR) message (which may also be referred to as message 1 and message 2), respectively. In 724, if timer T3XX has not expired, the UE can attempt fast RLF recovery. In this scenario, UE 702 may provide an RRC reconstruction request to cell 704, indicating that fast RLF recovery configuration information is available at UE 702. In 726, cell 704 may provide UE 702 with an RRC reply or RRC reconstruction message indicating the restoration of a previously (e.g., stored) configuration. In 728, UE 702 may provide cell 704 with an RRC reply complete or RRC reconstruction complete message, which completes the RRC connection reconstruction.

[0116] Figures 8 to 9This is a signal flow diagram illustrating additional possible details (including signaling aspects) of possible fast RLF recovery techniques that can be performed between the UE and the serving cell after an RLF occurs, according to some implementation schemes.

[0117] In particular, Figure 8 The diagram illustrates various aspects of a scenario where cell 804 instructs cell 804 to acknowledge UE 802's fast RLF recovery. In the illustrated scenario, at 806, UE 802 may send an RRC reconstruction request to cell 804 and may stop timer T3XX started when the RLF was declared. At 808, cell 804 may provide an RRC reply message to UE 802 in response to the RRC reconstruction request. Optionally, incremental configuration information may be provided to UE 802 (e.g., only indicating changes to previous configurations that have been agreed upon for the connection between UE 802 and cell 804). It is possible that the next-hop (NH) chain counter (NCC) may not be included in the RRC reply message; for example, the UE and cell 804 may use horizontal key derivation to derive a new K*gNB for encryption. At 810, UE 802 may send an RRC reply completion message to cell 804. It should be noted that, as an alternative to stopping timer T3XX when starting the procedure (e.g., when sending an RRC rebuild request), timer T3XX can be stopped when the UE sends an RRC reply completion message to cell 804.

[0118] Figure 9 The diagram illustrates various aspects of a scenario where cell 904 indicates that it does not recognize UE 902's fast RLF recovery. In the illustrated scenario, in 906, UE 902 may send an RRC reconstruction request to cell 904 and may stop timer T3XX started when the RLF is declared. In 908, cell 904 may provide an RRC reconstruction message to UE 902 in response to the RRC reconstruction request. The RRC reconstruction message may include NCC. Optionally, in 910, RRC reconfiguration may be embedded in a container of the RRC reconstruction message, for example, to avoid the RRC reconfiguration procedure. In 912, UE 902 may send an RRC reconstruction complete message to cell 904. For example, if the RRC configuration is embedded in a container of the RRC reconstruction message, then optionally, in 914, an RRC reconfiguration complete indication may be embedded in a container of the RRC reconstruction complete message. Similar to... Figure 8 In some scenarios, as an alternative to stopping timer T3XX when starting the program (e.g., when sending an RRC rebuild request), timer T3XX can be stopped when the UE sends an RRC rebuild complete message to cell 904.

[0119] Figure 10This is a signal flow diagram illustrating aspects (including signaling) of an alternative method for a fast RLF recovery technique that can be performed between the UE and the serving cell after an RLF occurs, according to some implementation schemes. As shown, signal flow can be performed between UE 1002 and cell 1004 of the cellular network. In the illustrated scenario, at 1006, UE 1002 can send an RRC reconstruction request to cell 1004 and can stop timer T3XX started when the RLF was declared. At 1008, cell 1004 can provide an RRC reconstruction message to UE 1002 in response to the RRC reconstruction request. Figure 10 In the illustrated method, cell 1004 may always send an RRC rebuild message in response to an RRC rebuild request, for example, regardless of whether cell 1004 approves the use of a previous configuration. Therefore, cell 1004 may include a flag indicating whether UE 1002 should reuse the previous configuration. An NCC may be included; if the network accepts horizontal key export, the NCC may remain the same. Optionally, cell 1004 may include incremental configuration information. It should be noted that the flag indicating whether the network can accept the reuse of a previous configuration may be provided unencrypted (plaintext). If incremental configuration information is provided, this information may still be encrypted (e.g., using security information associated with the previously indicated acceptable configuration).

[0120] It should be noted that message 3 of the RRC reconstruction procedure (e.g., RRC reconstruction request) may include a Short Message Authentication Code-Integrity (ShortMAC-I) to help the network identify the UE making the transmission request. If the UE indicates a preference for using the previously configured settings, the network may consider the request after successfully identifying the UE (e.g., based on the Physical Cell Identifier (PCI) and the Cell Radio Network Temporary Identifier (C-RNTI)).

[0121] The NR may require that protected messages be used whenever configuration is applied (from the network to the UE). For message 4 of the RRC reconstruction procedure for fast RLF recovery, in scenarios where the network accepts fast RLF recovery using the previously configured settings and the RRC reply message is used as message 4, the gNB can remain the same, thus eliminating the need for Packet Data Convergence Protocol (PDCP) relocation. Therefore, horizontal key export can be performed by the gNB to export a new key (K*gNB) for protecting the RRC reply message (e.g., to provide encryption and integrity protection). For message 4 of the RRC reconstruction procedure for fast RLF recovery, in scenarios where the network accepts fast RLF recovery using the previously configured settings and the RRC reconstruction message is used as message 4, clean text message 4 can be used if configuration is not included. In scenarios where the network does not accept fast RLF recovery using the previously configured settings, the gNB can send an RRC reconstruction message as message 4, and it is possible that no additional configuration information is encapsulated when the message may not be encrypted. The UE's NCC may be included, and the UE can perform horizontal or vertical key export based on the NCC.

[0122] It should also be noted that, according to at least some implementation schemes, inter-gNB scenarios can be supported, for example, where the UE can perform fast RLF recovery on a different cell than the cell on which the RLF occurred. In this scenario, security considerations may include the possible use of two-hop forward security. For example, if horizontal key export was used earlier, it is possible that the target gNB cannot use horizontal key export again. Therefore, in this scenario, it is possible that message 4 always includes the new NCC. In some scenarios, the UE may include a bit indicator from message 3 to indicate whether horizontal or vertical key export was used in the previous KgNB generation.

[0123] Another potentially important consideration for using previously configured fast RLF recovery techniques between the UE and the network may include consistency between the UE and the network regarding the previous configuration used for fast RLF recovery. For example, according to at least some implementations, such as in scenarios where the network has potentially sent an RRC reconfiguration message but has not received an RRC reconfiguration completion message to confirm the reconfiguration, the network may not know when the UE entered the RLF, and therefore may not necessarily know what the UE's previous configuration was at the time of the RLF.

[0124] As an option for handling this scenario, since the network has not yet received the RRC reconfiguration complete message from the UE, the network can determine, based on the RRC reconfiguration message, not to modify the configuration used for the UE. If the network must modify its network resources (e.g., due to load balancing and / or other reasons), making the previous configuration no longer valid at the network, the network can determine to cause Fast RLF recovery to fail and instead instruct the UE to perform a full RRC rebuild including RRC reconfiguration.

[0125] On the UE side, if the UE applies the configuration indicated in the RRC reconfiguration message, generates and provides an RRC reconfiguration completion message to L1, but cannot deliver the RRC reconfiguration completion message due to an RLF, the UE can determine that the configuration prior to (e.g., before the last one) the RRC reconfiguration completion message was sent before the RLF occurred, until the UE receives a low-level acknowledgment that the RRC reconfiguration completion message was sent before the RLF occurred. As another possibility, the network may be able to enclose the new configuration in message 4 in a manner similar to the RRC response procedure (e.g., to eliminate any inconsistencies). However, in this scenario, signaling overhead may not be significantly reduced, for example, compared to a method that provides this information in the first RRC reconfiguration message after the RRC reconstruction. Therefore, at least according to some embodiments, a method can be used in which, in the event of inconsistency between the UE and the network regarding the configuration to be used for fast RLF recovery, the network rejects fast RLF recovery and executes the UE's full configuration. At least in some implementations, if the network is configuring the t3xx timer value for fast RLF recovery (e.g., in an RRCReconfiguration message), the network may store the UE's configuration for a period of time at least equal to the length of the t3xx timer period to facilitate configuration recovery.

[0126] In some implementations, the network may provide a default or fallback configuration for the UE when establishing an RRC connection (e.g., at the time of the original connection establishment), which is intended for RLF situations. In this scenario, both the network and the UE may store this configuration for the UE for potential use later in RLF recovery. At least as a possibility, this default / fallback configuration may be provided after security is established, at the time of the original connection establishment. For example, this default / fallback configuration may be provided during an RRC reconfiguration procedure. The network may be able to update the default / fallback configuration (e.g., in a subsequent RRC reconfiguration procedure), but in this case, in a scenario where an RLF occurs during an RRC reconfiguration procedure that updates the default / fallback configuration, the UE and the network may also (albeit relatively less) lose synchronization regarding RRC reconfiguration. In some instances, the network may provide an I-RNTI for the UE to use to resume the RRC connection after an RLF, along with a list of cells on which the I-RNTI can be used for fast RLF recovery, such that even if a different cell is selected after the RLF than the cell the UE was attached to before the RLF occurred, the UE context can potentially be obtained from the cell.

[0127] In some implementations, the network may provide the NCC a priori in early configuration to prepare for possible RLF recovery scenarios. This allows the UE to avoid horizontal key derivation. When the network identifies the UE in message 3 based on shortMAC-I or I-RNTI, the cell can use this NCC to generate a key to encrypt message 4 and restore the SRB2 and any configured DRBs for the UE.

[0128] While common scenarios where the fast RLF recovery technique described herein can be used may include when a UE recovers to the same gNB (PCell) to which the UE was attached before the RLF, as previously noted, support for such fast RLF recovery can also be provided to a different gNB than the one to which the UE was attached before the RLF. As part of this support, the network may be configured with a list of cell groups in which the network allows the UE to perform fast RLF recovery. Fast RLF recovery at the target gNB may involve the target gNB receiving message 3 from the UE requesting fast RLF recovery for verification via the source gNB. If a default / fallback configuration is provided, the target gNB may acquire and apply the default / fallback configuration provided for the UE. The default / fallback configuration may be a generic configuration provided on top of the default PHY configuration (e.g., provided in SIB1 and / or via the 3GPP RRC / PHY specification). Therefore, in this scenario, the default / fallback configuration can be valid for a specific cell group, as long as the network can retrieve the UE context (e.g., including security authentication) within that cell group (e.g., based on an RRC rebuild request sent by the UE). Alternatively, if no default / fallback configuration is provided, the target gNB can retrieve the previous configuration from the source gNB, and if the network agrees to restore that previous configuration, the target gNB can send an "OK" response in message 4 in response to an RRC rebuild request to restore that configuration sent by the UE.

[0129] Further exemplary implementations are provided below.

[0130] One set of embodiments may include a wireless device comprising: an antenna; a radio component operatively coupled to the antenna; and a processor operatively coupled to the radio component; wherein the wireless device is configured to: establish a radio resource control (RRC) connection with a first cell; detect a radio link failure in the RRC connection; and transmit an RRC reconstruction request, wherein the RRC reconstruction request indicates a preference for restoring a previously configured RRC configuration.

[0131] According to some implementation schemes, the RRC connection with the first cell has a first RRC configuration, wherein the previously configured RRC configuration indicated by the wireless device as preferred is the first RRC configuration.

[0132] According to some implementations, the wireless device is further configured to receive RRC configuration information for use in fast radio link failure recovery, wherein the previously configured RRC configuration indicated by the wireless device as preferred is the fallback RRC configuration.

[0133] According to some implementation schemes, the RRC reconstruction request is provided to the first cell, wherein the radio device is further configured to: determine, at least in part, a preference for restoring the previously configured RRC configuration based on the RRC reconstruction request provided to the first cell.

[0134] According to some implementations, the wireless device is further configured to receive an indication from a first cell in a group of cells on which fast radio link failure recovery using a previously configured RRC configuration is permitted, wherein the RRC reconstruction request is provided to a cell in the group of cells on which fast radio link failure recovery using a previously configured RRC configuration is permitted.

[0135] According to some implementations, the wireless device is further configured to: receive an RRC reply message in response to an RRC reconstruction request, wherein the RRC reply message indicates the restoration of the previously configured RRC configuration; and perform a horizontal key export to export a key for use in the encryption and integrity protection of the RRC reply message.

[0136] According to some implementations, the wireless device is further configured to: receive an RRC reconstruction message in response to an RRC reconstruction request, wherein the RRC reconstruction message indicates restoration of the previously configured RRC configuration, wherein the RRC reconstruction message indicates a next-hop chain count (NCC); and perform horizontal or vertical key derivation at least in part based on the NCC indicated in the RRC reconstruction message to derive a key for use in encryption and integrity protection of the RRC connection.

[0137] According to some implementations, the wireless device is further configured to: receive a timer value indicating a time window for rapid radio link failure recovery; and start a timer with the timer value based at least in part on the detection of a radio link failure in the RRC connection, wherein the RRC reconstruction request indicates a preference for restoring the previously configured RRC configuration.

[0138] Another set of embodiments may include an apparatus comprising: a processor configured to cause a wireless device to: establish a radio link with the cell provided by a cellular base station; detect a radio link failure of the radio link; and transmit a request to rebuild the radio link with the cell using a previously provided radio link configuration.

[0139] According to some implementations, the processor is further configured to enable the wireless device to receive from the cell an instruction to rebuild the wireless link using a previously provided wireless link configuration.

[0140] According to some implementations, the processor is further configured to enable the wireless device to receive security information from the cell for use in rebuilding the wireless link using previously provided wireless link configuration.

[0141] According to some implementations, the processor is further configured to enable the wireless device to receive incremental configuration information from the cell indicating changes in the wireless link configuration relative to previously provided wireless link configuration.

[0142] According to some implementations, the processor is further configured to cause the wireless device to: receive from the cell an instruction to rebuild the wireless link using new wireless link configuration information, wherein based on the instruction to rebuild the wireless link using new wireless link configuration information, the previously provided wireless link configuration is not used to rebuild the wireless link.

[0143] Another set of embodiments may include a cellular base station comprising: an antenna; a radio component operatively coupled to the antenna; and a processor operatively coupled to the radio component; wherein the cellular base station is configured to: establish a radio link with a wireless device; and receive a request from the wireless device to re-establish the radio link, wherein the request to re-establish the radio link indicates a preference for restoring previously configured radio link configuration information.

[0144] According to some implementation schemes, the cellular base station is further configured to transmit instructions to wireless devices to rebuild the wireless link using previously configured wireless link configuration information.

[0145] According to some implementation schemes, the cellular base station is further configured to transmit security information to wireless devices for use in rebuilding the wireless link using previously configured wireless link configuration information.

[0146] According to some implementations, the processor is further configured to enable the wireless device to transmit incremental configuration information indicating changes in the configuration of the wireless link relative to previously configured wireless link configuration information.

[0147] According to some implementation schemes, the cellular base station is further configured to transmit instructions to wireless devices to rebuild the wireless link using a new wireless link configuration.

[0148] According to some implementation schemes, the cellular base station is further configured to provide timer configuration information to wireless devices, wherein the timer configuration information indicates the timer length of a fast radio link failure recovery availability timer.

[0149] According to some implementation schemes, the cellular base station is further configured to: identify the wireless device using one or more of Short Message Authentication Code-Integrity (ShortMAC-I) or Inactive Radio Network Temporary Identifier (I-RNTI); and determine, at least in part, whether to restore previous wireless link configuration information used by the wireless link for re-establishing the wireless link based on identifying the wireless device using one or more of ShortMAC-I or I-RNTI.

[0150] Another exemplary implementation may include a method comprising: performing any or all of the foregoing examples by a wireless device.

[0151] Another exemplary embodiment may include a device comprising: an antenna; a radio component coupled to the antenna; and a processing element operatively coupled to the radio component, wherein the device is configured to implement any or all of the foregoing examples.

[0152] Another set of exemplary embodiments may include a non-transitory computer-accessible memory medium comprising program instructions that, when executed at the device, cause the device to implement any or all of the portions of any of the foregoing examples.

[0153] Another exemplary set of implementations may include a computer program comprising instructions for performing any or all portions of any of the examples described above.

[0154] Another exemplary set of embodiments may include an apparatus that includes means for performing any or all elements of any of the examples described above.

[0155] Another set of exemplary embodiments may include an apparatus that includes a processing element configured to cause a wireless device to perform any or all of the elements of any of the foregoing examples.

[0156] As is widely recognized, the use of personally identifiable information should comply with privacy policies and practices that are generally accepted to meet or exceed industry or governmental requirements for protecting user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly explained to users.

[0157] By interpreting each message / signal X received by the user equipment (UE) in the downlink as a message / signal X transmitted by the base station, and interpreting each message / signal Y transmitted by the UE in the uplink as a message / signal Y received by the base station, any method described herein for operating the UE can serve as the basis for a corresponding method for operating the base station.

[0158] Embodiments of this disclosure may be implemented in any of a variety of forms. For example, in some embodiments, the subject matter may be implemented as a computer-implemented method, a computer-readable storage medium, or a computer system. In other embodiments, the subject matter may be implemented using one or more custom-designed hardware devices such as ASICs. In still other embodiments, the subject matter may be implemented using one or more programmable hardware elements such as FPGAs.

[0159] In some embodiments, a non-transitory computer-readable storage medium (e.g., a non-transitory memory element) may be configured to store program instructions and / or data, wherein if the program instructions are executed by a computer system, the computer system performs a method, such as any of the method embodiments described herein, or any combination of the method embodiments described herein, or any subset of any method embodiments described herein, or any combination of such subsets.

[0160] In some embodiments, a device (e.g., a UE) may be configured to include a processor (or a set of processors) and a memory medium (or memory elements), wherein the memory medium stores program instructions, and wherein the processor is configured to read from and execute the program instructions, wherein the program instructions are executable to implement any of the various method embodiments described herein (or any combination of the method embodiments described herein, or any subset or any combination of such subsets of any method embodiments described herein). The device may be implemented in any of a variety of forms.

[0161] Although the above embodiments have been described in considerable detail, many variations and modifications will become apparent to those skilled in the art once the disclosure is fully understood. This disclosure is intended to render the following claims as encompassing all such variations and modifications.

Claims

1. A method for wireless communication, comprising: establishing, by a wireless device: a radio resource control (RRC) connection with a first cell; receiving a timer value indicating a time window for fast radio link failure recovery; detecting a radio link failure of the RRC connection; starting, based at least in part on detecting the radio link failure of the RRC connection, a timer with the timer value; transmitting, based at least in part on the timer not expiring, an RRC reestablishment request, wherein the RRC reestablishment request indicates a preference to resume a previously configured RRC configuration; and receiving, from a cellular base station, an indication to reestablish the RRC connection using the previously configured RRC configuration.

2. The method of claim 1, wherein the RRC connection with the first cell has a first RRC configuration, wherein the previously configured RRC configuration indicated as preferred by the wireless device is the first RRC configuration.

3. The method of claim 1, further comprising: receiving RRC configuration information configuring a fallback RRC configuration for use in fast radio link failure recovery, wherein the previously configured RRC configuration indicated as preferred by the wireless device is the fallback RRC configuration.

4. The method of claim 1, wherein the RRC reestablishment request is transmitted to the first cell, wherein the method further comprises: determining, based at least in part on the RRC reestablishment request transmitted to the first cell, the preference to resume the previously configured RRC configuration.

5. The method of claim 1, further comprising: receiving an indication from the first cell that is in a group of cells that allow fast radio link failure recovery using a previously configured RRC configuration, wherein the RRC reestablishment request is transmitted to a cell in the group of cells that allow fast radio link failure recovery using a previously configured RRC configuration.

6. The method of claim 1, further comprising: receiving an RRC resume message in response to the RRC reestablishment request, wherein the RRC resume message indicates to resume the previously configured RRC configuration; and performing horizontal key derivation to derive keys for use in ciphering and integrity protection of the RRC resume message.

7. The method of claim 1, further comprising: receiving an RRC reestablishment message in response to the RRC reestablishment request, wherein the RRC reestablishment message indicates to resume the previously configured RRC configuration, wherein the RRC reestablishment message indicates a next hop chain count (NCC); and performing horizontal or vertical key derivation to derive keys for use in ciphering and integrity protection of the RRC connection based at least in part on the NCC indicated in the RRC reestablishment message.

8. The method of claim 1, further comprising: receiving, from the cellular base station, incremental configuration information indicating a change in configuration of the RRC connection relative to the previously configured RRC configuration.

9. An apparatus for wireless communication, comprising: a processor configured to cause a wireless device to: establishing a radio link with a cell provided by a cellular base station; detecting a radio link failure of the radio link; performing cell selection to determine which cell to attempt to reestablish the radio link with; determining, based at least in part on the cell selected for radio link reestablishment attempt, whether to use a previously configured RRC configuration to reestablish the radio link, including determining to prefer using the previously configured RRC configuration to reestablish the radio link in response to determining to reestablish the radio link with the cell; and transmitting a request to reestablish the radio link with the cell using the previously provided radio link configuration.

10. The apparatus of claim 9, wherein the processor is further configured to cause the wireless device to: receive, from the cell, an indication to reestablish the radio link using the previously provided radio link configuration.

11. The apparatus of claim 10, wherein the processor is further configured to cause the wireless device to: receive, from the cell, security information for use in reestablishing the radio link using the previously provided radio link configuration.

12. The apparatus of claim 10, wherein the processor is further configured to cause the wireless device to: receive, from the cell, delta configuration information indicating a change in the radio link configuration relative to the previously provided radio link configuration.

13. The apparatus of claim 9, wherein the processor is further configured to cause the wireless device to: receive, from the cell, an indication to reestablish the radio link using new radio link configuration information, wherein the previously provided radio link configuration is not used to reestablish the radio link based on the indication to reestablish the radio link using new radio link configuration information.

14. A method for wireless communication, comprising: by a cellular base station: establishing a radio link with a wireless device; providing timer configuration information to the wireless device, wherein the timer configuration information indicates a timer length of a fast radio link failure recovery availability timer; receiving, from the wireless device, a request to reestablish the radio link, wherein the request to reestablish the radio link is transmitted based at least in part on a timer started with the timer length not expiring when the wireless device detects a radio link failure, and indicates a preference for recovering previously configured radio link configuration information; transmitting, to the wireless device, an indication to reestablish the radio link using the previously configured radio link configuration information.

15. The method of claim 14, further comprising: transmitting, to the wireless device, security information for use in reestablishing the radio link using the previously configured radio link configuration information.

16. The method of claim 14, further comprising: transmitting, to the wireless device, an indication to reestablish the radio link using new radio link configuration.

17. The method of claim 14, further comprising: transmitting, to the wireless device, delta configuration information indicating a change in a configuration of the radio link relative to the previously configured radio link configuration information.

18. The method of claim 14, further comprising: identify the wireless device using one or more of a short message authentication code-integrity (shortMAC-I) or an inactive radio network temporary identifier (I-RNTI); and determine whether to resume a previous wireless link configuration information for the wireless link that reestablishes the wireless link based at least in part on identifying the wireless device using one or more of the shortMAC-I or the I-RNTI.

19. An apparatus for wireless communication, comprising: a processor configured to perform the operations of the method of any of claims 1-8 or 14-18 when executing instructions stored in memory.

20. A non-transitory computer-readable storage medium storing program instructions executable by one or more processors to cause a wireless device or a cellular base station to perform the operations of the method of any of claims 1-8 or 14-18.

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