WO2021217677A1

WO2021217677A1 - Restoration of data connectivity after radio link failure in standalone network

Info

Publication number: WO2021217677A1
Application number: PCT/CN2020/088535
Authority: WO
Inventors: Jian Li; Fojian ZHANG; Hao Zhang; Chaofeng HUI; Jianfu ZHANG; Xiaomin Dong; Haibo Liu; Wei He; Hong Wei
Original assignee: Qualcomm Incorporated
Priority date: 2020-05-01
Filing date: 2020-05-01
Publication date: 2021-11-04

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine, while registered with a New Radio standalone network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control reestablishment requests. The UE may perform a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold. Numerous other aspects are provided.

Description

RESTORATION OF DATA CONNECTIVITY AFTER RADIO LINK FAILURE IN STANDALONE NETWORK

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for restoration of data connectivity after radio link failure in a standalone network.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs) . A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP) , a radio head, a transmit receive point (TRP) , a New Radio (NR) BS, a 5G Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New Radio (NR) , which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP) . NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL) , using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink (UL) , as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method of wireless communication, performed by a user equipment (UE) , may include determining, while registered with a New Radio (NR) standalone (SA) network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests. The method may include performing a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.

In some aspects, a UE for wireless communication may include memory and one or more processors coupled to the memory. For example, the one or more processors may be operatively, electronically, communicatively, or otherwise coupled to the memory. The memory may include instructions executable by the one or more processors to cause the UE to determine, while registered with an NR SA network, that a count of RLFs for a cell satisfies a failure count threshold, based at least in part on transmitting one or more RRC reestablishment requests, and perform a TAU procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.

In some aspects, an apparatus for wireless communication may include means for determining, while registered with an NR SA network, that a count of RLFs for a cell satisfies a failure count threshold, based at least in part on transmitting one or more RRC reestablishment requests, and means for performing a TAU procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a base station in communication with a user equipment (UE) in a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 3 is a diagram illustrating an example of radio link failures in a standalone network, in accordance with various aspects of the present disclosure.

Fig. 4 is a diagram illustrating an example of restoration of data connectivity after radio link failure in a standalone network, in accordance with various aspects of the present disclosure.

Fig. 5 is a diagram illustrating an example process performed, for example, by a UE, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

It should be noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

Fig. 1 is a diagram illustrating a wireless network 100 in which aspects of the present disclosure may be practiced. The wireless network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. The wireless network 100 may include a number of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, an NR BS, a Node B, a gNB, a 5G node B (NB) , an access point, a transmit receive point (TRP) , and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG) ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in Fig. 1, a BS 110a may be a macro BS for a macro cell 102a, a BS 110b may be a pico BS for a pico cell 102b, and a BS 110c may be a femto BS for a femto cell 102c. A BS may support one or multiple (e.g., three) cells. The terms “eNB” , “base station” , “NR BS” , “gNB” , “TRP” , “AP” , “node B” , “5G NB” , and “cell” may be used interchangeably herein.

In some aspects, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network.

Wireless network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in Fig. 1, a relay station 110d may communicate with macro BS 110a and a UE 120d in order to facilitate communication between BS 110a and UE 120d. A relay station may also be referred to as a relay BS, a relay base station, a relay, and/or the like.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 watts) .

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120a, 120b, 120c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet) ) , an entertainment device (e.g., a music or video device, or a satellite radio) , a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE) . UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like. In some aspects, the processor components and the memory components may be coupled together. For example, the processor components (e.g., one or more processors) and the memory components (e.g., a memory) may be operatively coupled, communicatively coupled, electronically coupled, electrically coupled, and/or the like.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some aspects, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (e.g., without using a base station 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like) , a mesh network, and/or the like. In this case, the UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the base station 110.

As indicated above, Fig. 1 is provided as an example. Other examples may differ from what is described with regard to Fig. 1.

Fig. 2 shows a block diagram of a design 200 of base station 110 and UE 120, which may be one of the base stations and one of the UEs in Fig. 1. Base station 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general T ≥ 1 and R ≥ 1.

At base station 110, a transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS (s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS) ) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to various aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

At UE 120, antennas 252a through 252r may receive the downlink signals from base station 110 and/or other base stations and may provide received signals to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller/processor 280. A channel processor may determine reference signal received power (RSRP) , received signal strength indicator (RSSI) , reference signal received quality (RSRQ) , channel quality indicator (CQI) , and/or the like. In some aspects, one or more components of UE 120 may be included in a housing.

Network controller 130 may include communication unit 294, controller/processor 290, and memory 292. Network controller 130 may include, for example, one or more devices in a core network. Network controller 130 may communicate with base station 110 via communication unit 294.

On the uplink, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like) , and transmitted to base station 110. In some aspects, the UE 120 includes a transceiver. The transceiver may include any combination of antenna (s) 252, modulators and/or demodulators 254, MIMO detector 256, receive processor 258, transmit processor 264, and/or TX MIMO processor 266. The transceiver may be used by a processor (e.g., controller/processor 280) and memory 282 to perform aspects of any of the methods described herein, for example, as described with reference to Figs. 4-5.

At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. Base station 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. In some aspects, the base station 110 includes a transceiver. The transceiver may include any combination of antenna (s) 234, modulators and/or demodulators 232, MIMO detector 236, receive processor 238, transmit processor 220, and/or TX MIMO processor 230. The transceiver may be used by a processor (e.g., controller/processor 240) and memory 242 to perform aspects of any of the methods described herein, for example, as described with reference to Figs. 4-5.

Controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with restoration of data connectivity after radio link failure (RLF) in a standalone (SA) network, as described in more detail elsewhere herein. For example, controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 500 of Fig. 5, and/or other processes as described herein.

Memories

242 and 282 may store data and program codes for base station 110 and UE 120, respectively. In some aspects, memory 242 and/or memory 282 may comprise a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, interpreting, and/or the like) by one or more processors of the base station 110 and/or the UE 120, may perform or direct operations of, for example, process 500 of Fig. 5, and/or other processes as described herein. In some aspects, executing instructions may include running the instructions, converting the instructions, compiling the instructions, interpreting the instructions, and/or the like. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE 120 may include means for determining, while registered with an NR SA network, that a count of RLFs for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests, means for performing a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold, and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2, such as controller/processor 280, transmit processor 264, TX MIMO processor 266, MOD 254, antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, and/or the like.

As indicated above, Fig. 2 is provided as an example. Other examples may differ from what is described with regard to Fig. 2.

Fig. 3 is a diagram illustrating an example 300 of RLFs in an SA network, in accordance with various aspects of the present disclosure. Fig. 3 shows a signaling diagram for a UE (e.g., a UE 120 depicted in Figs. 1 and 2) in a 5G (NR) SA network.

The UE may perform a registration procedure to register with the NR SA network, as shown by reference number 305. For example, the UE may transmit a registration request to an NR cell and receive a registration accept message. As shown by reference number 310, the UE may establish an RRC connection with the cell. The NR SA network may provide NR data service over the RRC connection.

The UE may experience an RLF, as shown by reference number 315. For example, the UE may detect, at a physical layer, one or more decoding errors for a communication on a physical downlink channel with the RRC connection. The one or more decoding errors may be due to a poor signal or the UE being out of synchronization with the NR SA network. The UE may determine that an RLF occurred based at least in part on detecting the one or more decoding errors. In some aspects, the UE may utilize timers (e.g., T310) or other physical layer indications (e.g., N310) for detecting physical layer problems and for determining whether there is an RLF of the RRC connection. In some aspects, the UE may report a reason for an RLF to a base station.

The UE may attempt to reestablish the RRC connection. As shown by reference number 320, the UE may transmit an RRC reestablishment request. As shown by reference number 325, the UE may receive an RRC setup message. As shown by reference number 330, the UE may transmit an RRC setup complete message if the RRC setup is successful. Reference numbers 315 to 330 may be part of a procedure for determining that an RLF occurred and for reestablishing the RRC connection. This procedure may repeat in a loop and the UE may fail to maintain data service due to the RRC connection being unstable. The UE wastes power, processing resources, and signaling resources by repeatedly detecting RLFs and reestablishing the RRC connection.

As indicated above, Fig. 3 is provided as an example. Other examples may differ from what is described with respect to Fig. 3.

Fig. 4 is a diagram illustrating an example 400 of restoration of data connectivity after RLF in an SA network, in accordance with various aspects of the present disclosure. Fig. 4 includes some signals that are in the signaling diagram shown in Fig. 3.

According to various aspects described herein, the UE may address RRC connection instability of a cell by falling back to a non-standalone (NSA) mode on another cell (e.g., LTE cell) . For example, the UE may perform a TAU procedure with an LTE cell. The TAU procedure is a procedure applicable to LTE networks and normally updates a location of the UE within an LTE network. If the 5G SA cell and the LTE cell are maintained by the same operator, the UE does not need a new registration and a TAU procedure is sufficient to attach the UE to the LTE cell. By falling back to the LTE cell, the UE may avoid repeated requests to reestablish an unstable RRC connection with the 5G SA cell. As a result, the UE may restore access to the Internet and provide another opportunity to access an NR data service.

In some aspects, the UE may determine that an RRC connection to a cell is unstable by counting RLFs that occur for the cell. For example, as shown by reference number 405, the UE may count a quantity of RLFs, and determine whether the count of RLFs satisfies a failure count threshold (e.g., maximum count) . If the count does not satisfy the failure count threshold, the UE may continue to reestablish the RRC connection to the cell. In some aspects, the count of RLFs is determined based at least in part on a timer that is set to a particular duration of time and/or is reset when the NR data service is restored for a minimum amount of time.

In some aspects, if the count does satisfy the failure count threshold (e.g., three RLFs within 30 seconds) , the UE may stop repeating RRC reestablishment requests. As shown by reference number 410, the UE may switch to an NSA mode, where the UE may prepare to attach to an NSA network. While not as low-latency and simplified as an NR SA network, an NSA network utilizes an existing LTE infrastructure with an LTE anchor to provide access to the internet and access to an NR data service.

The UE may perform a TAU procedure to fall back to an NSA cell (LTE cell shown in Fig. 4) of the NSA network from the 5G SA cell. The UE may transmit a TAU request to the LTE cell, as shown by reference number 415, and receive a TAU accept message, as shown by reference number 420. The TAU request may include information related to evolved packet system bearers, UE identification information, a UE capability, and/or the like. The TAU request may indicate a UE capability for dual connectivity with NR (DCNR) , which may enable the UE to access the NR data service with the NSA network by adding a secondary cell group.

As shown by reference number 425, the UE may transmit a service request to the LTE cell to gain access to the Internet. As a result, the UE is able to transfer data, as shown by reference number 430, and not experience repeated RLFs. The UE also saves power, processing resources, and signaling resources by not repeatedly detecting RLFs and reestablishing an unstable RRC connection.

As indicated above, Fig. 4 is provided as an example. Other examples may differ from what is described with respect to Fig. 4.

Fig. 5 is a diagram illustrating an example process 500 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 500 is an example where the UE (e.g., UE 120 and/or the like) performs operations associated with restoration of data connectivity after RLF in an SA network.

As shown in Fig. 5, in some aspects, process 500 may include determining, while registered with an NR SA network, that a count of RLFs for a cell satisfies a failure count threshold, based at least in part on transmitting one or more RRC reestablishment requests (block 510) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may determine, while registered with an NR SA network, that a count of RLFs for a cell satisfies a failure count threshold, based at least in part on transmitting one or more RRC reestablishment requests, as described above.

As further shown in Fig. 5, in some aspects, process 500 may include performing a TAU procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold (block 520) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may perform a TAU procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold, as described above.

Process 500 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, determining that the count of RLFs satisfies the failure count threshold includes determining that the count of RLFs satisfies the failure count threshold before expiration of a timer.

In a second aspect, alone or in combination with the first aspect, determining that the count of RLFs satisfies the failure count threshold includes determining an RLF based at least in part on detecting a decoding error for a communication on a physical downlink channel.

In a third aspect, alone or in combination with one or more of the first and second aspects, performing the TAU procedure includes transmitting a TAU request to another cell and receiving a TAU accept message.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the TAU request indicates a capability for dual connectivity.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the TAU request indicates a capability for DCNR.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process 500 includes transmitting a service request to the other cell.

Although Fig. 5 shows example blocks of process 500, in some aspects, process 500 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 5. Additionally, or alternatively, two or more of the blocks of process 500 may be performed in parallel.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term “component” is intended to be broadly construed as hardware, software, and/or a combination of hardware and software. As used herein, a processor is implemented in hardware, software, and/or a combination of hardware and software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

As used herein, satisfying a threshold may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, software, and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code-it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) , and may be used interchangeably with “one or more. ” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

Claims

A method of wireless communication performed by a user equipment (UE) , comprising:

determining, while registered with a New Radio (NR) standalone network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests; and

performing a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.
The method of claim 1, wherein determining that the count of RLFs satisfies the failure count threshold includes determining that the count of RLFs satisfies the failure count threshold before expiration of a timer.
The method of claim 1, wherein determining that the count of RLFs satisfies the failure count threshold includes determining an RLF based at least in part on detecting a decoding error for a communication on a physical downlink channel.
The method of claim 1, wherein performing the TAU procedure includes transmitting a TAU request to another cell and receiving a TAU accept message.
The method of claim 4, wherein the TAU request indicates a capability for dual connectivity.
The method of claim 5, wherein the TAU request indicates a capability for dual connectivity with NR.
The method of claim 4, further comprising transmitting a service request to the other cell.
A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors coupled to the memory, the memory including instructions executable by the one or more processors to cause the UE to:

determine, while registered with a New Radio (NR) standalone network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests; and

perform a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions, when executed by one or more processors of a user equipment (UE) , cause the UE to:

determine, while registered with a New Radio (NR) standalone network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests; and

perform a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.
An apparatus for wireless communication, comprising:

means for determining, while registered with a New Radio (NR) standalone network, that a count of radio link failures (RLFs) for a cell satisfies a failure count threshold, based at least in part on transmitting one or more radio resource control (RRC) reestablishment requests; and

means for performing a tracking area update (TAU) procedure, based at least in part on the determining that the count of RLFs satisfies the failure count threshold.