WO2021207920A1

WO2021207920A1 - Method for fast detect and recover from dual connectivity data stall

Info

Publication number: WO2021207920A1
Application number: PCT/CN2020/084663
Authority: WO
Inventors: Yi Liu; Zhenqing CUI; Jinglin Zhang; Xiangfeng KANG; Pan JIANG; Yuankun ZHU; Hong Wei; Haojun WANG; Kaikai YANG
Original assignee: Qualcomm Incorporated
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2021-10-21

Abstract

Method and apparatus are provided for fast detection and recovery from dual connectivity data stall. In accordance with some implementation, a UE in an NSA call may determine a number of detected PDCP SN fluctuation within a first detecting duration is greater than a first threshold wherein a PDCP SN fluctuation is detected when PDCP SN of a data packet compared to a prior data packet is greater than a second threshold, triggering RLF based on the determining, re-establishing the connection with the BS, and detaching then attaching to the first RAT where the attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold.

Description

METHOD FOR FAST DETECT AND RECOVER FROM DUAL CONNECTIVITY DATA STALL

TECHNICAL FIELD

The present disclosure relates generally to wireless communication systems, and more particularly, to methods and apparatus for detecting and recovering from dual connecitivity data stall.

INTRODUCTION

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR) . 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT) ) , and other requirements. Some aspects of NR may be based on the Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

As the demand for mobile broadband access continue to increase, there is a need to increase speed and efficiency in establishing and re-establishing connections to and from base stations.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved communications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide a method for wireless communications by a user equipment (UE) . The method generally includes attaching to a first radio access technology (RAT) comprising establishing a connection with a base station (BS) of the first RAT and indicating that the UE is capable of dual-connectivity, determining a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold wherein a PDCP SN fluctuation is detected when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold, triggering radio link failure (RLF) based on the determining, re-establishing the connection with the BS, and detaching then attaching to the first RAT after the re-establishing where the attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold. In an aspect, the method may further include starting a timer based the indicating that the UE is not capable of dual-connectivity, detaching then attaching to the first RAT based on expiry of the timer where attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity. In an aspect, the indicating that the UE is or is not capable of dual-connectivity may comprise sending to the BS an attach accept message with dual-connectivity enabled or disabled, respectively. In an aspect, the prior data packet may be an immediately prior data packet to the data packet.

Aspects generally include methods, apparatus, systems, computer readable mediums, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which 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.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram illustrating an example logical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of an example base station (BS) and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 5 illustrates a wireless communication network implementing dual connectivity with a split bearer configuration.

FIG. 6 illustrates an example UE operation of fast detect and recovery from dual-connectivity data stall in accordance with aspects of the present disclosure.

FIG. 7 illustrates an example UE flow chart of fast detect and recovery from EN-DC data stall in accordance with aspects of the present disclosure.

FIG. 8 illustrates a communications device 800 that may include various components configured to perform aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

In a split bearer configuration, a UE in a non-standalone (NSA) call can maintain a single PDCP entity for dual-connectivity (DC) connection. This PDCP entity can route data (received from an upper layer or from a lower layer for uplink and downlink respectively) via multiple (e.g., two) separate radio interface protocol entities to and from the network. For example, the PDCP entity may route data to and from the network via an LTE radio interface protocol entity over an LTE link and/or an NR radio interface protocol entity over an NR link. For uplink, the PDCP entity may perform sequence numbering by associating each packet with a sequence number in an ascending order prior to transmission to the lower layers (e.g., the LTE RLC or the NR RLC) . For downlink, the PDCP entity may verify the sequence number of received data packets to determine loss, duplicate, out-of-order data packets.

During an NSA connection, in some instances, a UE may detect and declare radio link failure (RLF) on an LTE master cell after the UE is connected to the LTE master cell and 5G NR radio bearer is configured. In such instances, the UE may experience large PDCP sequence number (SN) fluctuation after the PDCP layer of the UE is switched from LTE PDCP to NR PDCP as part of configuring the NSA connection. Upon detecting RLF, the UE may re-establish RRC connection to recover data service. However, in some instances when large PDCP SN fluctuation is observed, the UE may repeatedly experience RLF and observe large PDCP SN fluctuation. The repeated RLF and large PDCP SN fluctuation may persist if the UE remains with the same LTE master cell. In such instances, the UE may be unable to acquire data service in the area at least for a significant time. It may be desirable to change the behavior of the UE so that the UE may acquire data service earlier.

The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. 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. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

The techniques described herein may be used for various wireless communication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . NR is an emerging wireless communications technology under development in conjunction with the 5G Technology Forum (5GTF) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, 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.

EXAMPLE WIRELESS COMMUNICATIONS SYSTEM

FIG. 1 illustrates an example wireless network 100, such as a new radio (NR) or 5G network, in which aspects of the present disclosure may be performed.

As illustrated in FIG. 1, the wireless network 100 may include a number of BSs 110 and other network entities. A BS may be a station that communicates with UEs. Each BS 110 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a Node B and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and eNB, Node B, 5G NB, AP, NR BS, NR BS, or TRP may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations 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, or the like using any suitable transport network.

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, etc. A frequency may also be referred to as a carrier, a frequency channel, etc. 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.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types 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) , UEs for users in the home, etc. ) . 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, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BS for the femto cells 102y and 102z, respectively. A BS may support one or multiple (e.g., three) cells.

The wireless network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., a BS or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that relays transmissions for other UEs. In the example shown in FIG. 1, a relay station 110r may communicate with the BS 110a and a UE 120r in order to facilitate communication between the BS 110a and the UE 120r. A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network 100. For example, macro BS may have a high transmit power level (e.g., 20 Watts) whereas pico BS, femto BS, and relays may have a lower transmit power level (e.g., 1 Watt) .

The wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, the BSs may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing, and transmissions from different BSs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.

A network controller 130 may be coupled to a set of BSs and provide coordination and control for these BSs. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, 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 medical equipment, a biometric sensor/device, a healthcare device, a medical device, a wearable device such as a smart watch, smart clothing, smart glasses, virtual reality goggles, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a gaming device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a positioning device (e.g., GPS, Beidou, GLONASS, Galileo, terrestrial-based) , 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) devices or enhanced or evolved MTC (eMTC) devices. MTC may refer to communication involving at least one remote device on at least one end of the communication and may include forms of data communication which involve one or more entities that do not necessarily need human interaction. MTC UEs may include UEs that are capable of MTC communications with MTC servers and/or other MTC devices through Public Land Mobile Networks (PLMN) , for example. Some UEs may be considered Internet of Things devices. The Internet of Things (IoT) is a network of physical objects or "things" embedded with, e.g., electronics, software, sensors, and network connectivity, which enable these objects to collect and exchange data. The Internet of Things allows objects to be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration between the physical world and computer-based systems, and resulting in improved efficiency, accuracy and economic benefit. When IoT is augmented with sensors and actuators, the technology becomes an instance of the more general class of cyber-physical systems, which also encompasses technologies such as smart grids, smart homes, intelligent transportation and smart cities. Each “thing” is generally uniquely identifiable through its embedded computing system but is able to interoperate within the existing Internet infrastructure. Narrowband IoT (NB-IoT) is a technology being standardized by the 3GPP standards body. This technology is a narrowband radio technology specially designed for the IoT, hence its name. Special focuses of this standard are on indoor coverage, low cost, long battery life and large number of devices. MTC/eMTC and/or IoT UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, 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. In FIG. 1, a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A dashed line with double arrows indicates interfering transmissions between a UE and a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth (e.g., system frequency band) into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a ‘resource block’ ) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal FFT size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks) , and there may be 1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR. NR may utilize OFDM with a cyclic prefix (CP) on the uplink and downlink and include support for half-duplex operation using time division duplex (TDD) . A single component carrier bandwidth of 100 MHz may be supported. NR resource blocks may span 12 sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 ms duration. Each radio frame may consist of 50 subframes with a length of 10 ms. Consequently, each subframe may have a length of 0.2 ms. Each subframe may indicate a link direction (i.e., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. Alternatively, NR may support a different air interface, other than an OFDM-based. NR networks may include entities such as central units (CU) and/or distributed units (DU) .

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs) . In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time–frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., eNB, 5G Node B, Node B, transmission reception point (TRP) , access point (AP) ) may correspond to one or multiple BSs. NR cells can be configured as access cell (ACells) or data only cells (DCells) . For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals-in some case cases DCells may transmit SS. NR BSs may transmit downlink signals to UEs indicating the cell type. Based on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based on the indicated cell type.

FIG. 2 illustrates an example logical architecture of a distributed radio access network (RAN) 200, which may be implemented in the wireless communication system illustrated in FIG. 1. A 5G access node 206 may include an access node controller (ANC) 202. The ANC may be a central unit (CU) of the distributed RAN 200. The backhaul interface to the next generation core network (NG-CN) 204 may terminate at the ANC. The backhaul interface to neighboring next generation access nodes (NG-ANs) may terminate at the ANC. The ANC may include one or more TRPs 208 (which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, or some other term) . As described above, a TRP may be used interchangeably with “cell. ”

The TRPs 208 may be a DU. The TRPs may be connected to one ANC (ANC 202) or more than one ANC (not illustrated) . For example, for RAN sharing, radio as a service (RaaS) , and service specific AND deployments, the TRP may be connected to more than one ANC. A TRP may include one or more antenna ports. The TRPs may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture 200 may be used to illustrate fronthaul definition. The architecture may be defined that support fronthauling solutions across different deployment types. For example, the architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter) .

The architecture may share features and/or components with LTE. According to aspects, the next generation AN (NG-AN) 210 may support dual connectivity with NR. The NG-AN may share a common fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 208. For example, cooperation may be preset within a TRP and/or across TRPs via the ANC 202. According to aspects, no inter-TRP interface may be needed/present.

According to aspects, a dynamic configuration of split logical functions may be present within the architecture 200. As will be described in more detail with reference to FIG. 5, the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU or CU (e.g., TRP or ANC, respectively) . According to certain aspects, a BS may include a central unit (CU) (e.g., ANC 202) and/or one or more distributed units (e.g., one or more TRPs 208) .

FIG. 3 illustrates an example physical architecture of a distributed RAN 300, according to aspects of the present disclosure. A centralized core network unit (C-CU) 302 may host core network functions. The C-CU may be centrally deployed. C-CU functionality may be offloaded (e.g., to advanced wireless services (AWS) ) , in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions. Optionally, the C-RU may host core network functions locally. The C-RU may have distributed deployment. The C-RU may be closer to the network edge.

A DU 306 may host one or more TRPs (edge node (EN) , an edge unit (EU) , a radio head (RH) , a smart radio head (SRH) , or the like) . The DU may be located at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120 illustrated in FIG. 1, which may be used to implement aspects of the present disclosure. As described above, the BS may include a TRP. One or more components of the BS 110 and UE 120 may be used to practice aspects of the present disclosure. For example, antennas 452, Tx/Rx 222,

processors

466, 458, 464, and/or controller/processor 480 of the UE 120 and/or antennas 434,

processors

460, 420, 438, and/or controller/processor 440 of the BS 110 may be used to perform the operations described herein and illustrated with reference to FIGs. 8-11.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, which may be one of the BSs and one of the UEs in FIG. 1. For a restricted association scenario, the base station 110 may be the macro BS 110c in FIG. 1, and the UE 120 may be the UE 120y. The base station 110 may also be a base station of some other type. The base station 110 may be equipped with antennas 434a through 434t, and the UE 120 may be equipped with antennas 452a through 452r.

At the base station 110, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the Physical Broadcast Channel (PBCH) , Physical Control Format Indicator Channel (PCFICH) , Physical Hybrid ARQ Indicator Channel (PHICH) , Physical Downlink Control Channel (PDCCH) , etc. The data may be for the Physical Downlink Shared Channel (PDSCH) , etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal. A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.

At the UE 120, the antennas 452a through 452r may receive the downlink signals from the base station 110 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 454 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480. According to one or more cases, CoMP aspects can include providing the antennas, as well as some Tx/Rx functionalities, such that they reside in distributed units. For example, some Tx/Rx processing can be done in the central unit, while other processing can be done at the distributed units. For example, in accordance with one or more aspects as shown in the diagram, the BS mod/demod 432 may be in the distributed units.

On the uplink, at the UE 120, a transmit processor 464 may receive and process data (e.g., for the Physical Uplink Shared Channel (PUSCH) ) from a data source 462 and control information (e.g., for the Physical Uplink Control Channel (PUCCH) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal. The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the modulators 454a through 454r (e.g., for SC-FDM, etc. ) , and transmitted to the base station 110. At the BS 110, the uplink signals from the UE 120 may be received by the antennas 434, processed by the demodulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120. The receive processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/

processors

440 and 480 may direct the operation at the base station 110 and the UE 120, respectively. The processor 440 and/or other processors and modules at the base station 110 may perform or direct, e.g., the processes for the techniques described herein. The processor 480 and/or other processors and modules at the UE 120 may also perform or direct, e.g., execution of the functional blocks illustrated in FIG. 9, and/or other processes for the techniques described herein. The

memories

442 and 482 may store data and program codes for the BS 110 and the UE 120, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, the network 100 may implement a split bearer in a ETURA NR-dual connectivity (EN-DC) configuration. A radio bearer is a service provided by Layer 2 to transport user data packets and/or signaling data between a UE and a network. A radio bearer that transports user data may be referred to as a data radio bearer (DRB) . A radio bearer that transports signaling data may be referred to as a signaling radio bearer (SRB) . The split bearer may transport data between a UE 120 and the network via two radio interface protocols over two wireless communication links (e.g., a NR link and an LTE link) . In NR and LTE radio interface protocols, Layer 2 may include several sublayers, such as a PDCP sublayer, a RLC sublayer, and a MAC sublayer. The PDCP sublayer may receive data packets from an upper layer (e.g., transmission control protocol/Internet protocol (TCP/IP) layer) and transport the data packets via the RLC sublayer, the MAC sublayer, and a physical (PHY) layer for OTA transmission. At the receiver side, data packets are received via a PHY layer, a MAC sublayer, an RLC sublayer, and a PDCP layer, which delivers the data packets to an upper layer. In a split bearer configuration, data may be split post-PDCP and transmitted or received through different RLC/MAC/PHY layers to and from a peer side as described in greater detail herein.

FIG. 5 illustrates a wireless communication network 500 implementing dual connectivity with a split bearer configuration according to some aspects of the present disclosure. Though the figure shows a dual connectivity illustration, additional degrees of connectivity can be implemented too. The network 500 may correspond to a portion of the network 100. In particular, the network 500 may configure a UE such as the UE 120 to implement a split bearer configuration for UL transmission as shown in FIG. 5. FIG. 5 shows a UE 515 communicatively coupled to a network 550 via an LTE wireless communication link 504 and an NR wireless communication link 506. The UE 515 may correspond to a UE 120 of FIG. 1. The UE 515 includes an upper layer entity 510, a PDCP entity 520, and two radio

interface protocol entities

530 and 540. The upper layer entity 510 may include a network stack such as TCP/IP. The radio

interface protocol entities

530 and 540 provide two separate paths to and from the network 550. The UE 515 may include hardware and/or software components configured to implement the upper layer entity 510, the PDCP entity 520, and the radio

interface protocol entities

530 and 540.

In the illustrated example of FIG. 5, the radio interface protocol entity 530 implements an LTE RAT and the radio interface protocol entity 540 implements an NR RAT. The LTE radio interface protocol entity 530 includes an LTE RLC entity 532, an LTE MAC entity 534, and an LTE PHY entity 536. The NR radio interface protocol entity 540 includes an NR RLC entity 542, an NR MAC entity 544, and an NR PHY entity 546. While FIG. 5 is described in the context of a radio bearer split between an LTE RAT and an NR RAT, a similar split radio bearer configuration can be applied to an NR-NR dual connectivity. In other words, the radio

interface protocol entities

530 and 540 are NR radio interface protocol entities and the

wireless communication links

504 and 506 are NR communication links. In some other instances, the split radio bearer can be configured between other suitable RATs.

The PDCP entity 520 may be an NR PDCP. The PDCP entity 520 may provide services to the upper layer entity 510, for example, including transfer of user plane data, header compression and decompression, ciphering and integrity protection, maintenance of PDCP sequence numbers, and in-sequence packet delivery. The PDCP entity 520 may receive acknowledged data transfer service (including indication of successful delivery of PDCP PDU) and/or unacknowledged data transfer services from the LTE RLC entity 532 and the NR RLC entity 542.

The LTE radio interface protocol entity 530 and the NR radio interface protocol entity 540 may operate independent of each other but may provide substantially similar services and/or functionalities.

RLC entities

532 and 542 may perform packet concatenation, segmentation, re-segmentation, and reassembly, and/or ARQ. In some instances, the LTE RLC entity 532 may perform packet reordering, whereas the NR RLC entity 542 may not perform packet reordering since packet reordering is performed at the NR PDCP entity 520. In the transmitting path, the

MAC entities

534 and 544 may perform mapping between logical channels and transport channels, multiplexing of MAC service data units (SDUs) from one or different logical channels onto transport blocks (TBs) to be delivered to corresponding

entities

536 and 546 on transport channels, respectively, and/or HARQ retransmissions. In the receiving path, the

MAC entities

534 and 544 may perform demultiplexing of MAC SDUs from one or different logical channels from TBs delivered from the corresponding

PHY entities

536 and 546 on transport channels, respectively, scheduling information reporting, error correction through HARQ, and/or facilitate quality of service (QoS) handling. The

PHY entities

536 and 546 carry data information to and from

corresponding MAC entities

534 and 544, respectively. The

PHY entities

536 and 546 may perform cell search, cell measurements, error coding, error decoding, modulation, demodulation, and/or physical channel scheduling and reporting.

In some aspects, the PDCP entity 520 receives data packets from the upper layer entity 510 and buffers the data packets in a UL PDCP queue 502 (e.g., at a buffer memory) . A PDCP entity may add PDCP packet headers to data packets (e.g., upper layer packets) and perform sequence numbering to associate each data packet with a sequence number in an ascending order. The data packets may be referred to as PDCP packets or PDCP PDUs. A PDCP packet being transmitted via the LTE radio interface protocol entity 530 may be processed by the LTE RLC entity 532, the LTE MAC entity 534, and the LTE PHY entity 536 prior to transmission over the wireless communication link 504 (e.g., a LTE link) . Similarly, a PDCP packet being transmitted via the NR radio interface protocol entity 540 may be processed by the NR RLC entity 542, the NR MAC entity 544, and NR PHY entity 546 prior to transmission over the wireless communication link 506 (e.g., a NR link) .

In certain aspects, a UE in an NSA call may experience repeated radio link failure (RLF) exhibiting large PDCP SN fluctuation. This may result in the UE failing repeated attempts at connection re-establishment and not able to acquire data service for a significant period of time. It may be desirable to change the behavior of the UE in such situation so that the UE may acquire data service earlier.

EXAMPLE FAST DETECT AND RECOVER FROM DC DATA STALL

During an NSA connection, in some instances, a UE may detect and declare radio link failure (RLF) on an LTE master cell after the UE is connected to the LTE master cell and 5G NR radio bearer is configured. In such instances, the UE may experience large PDCP sequence number (SN) fluctuation after the PDCP layer of the UE is switched from LTE PDCP to NR PDCP as part of configuring the NSA connection. Upon detecting RLF, the UE may re-establish RRC connection to recover data service. However, in some instances when large PDCP SN fluctuation is observed, the UE may repeatedly experience RLF and observe large PDCP SN fluctuation. The repeated RLF may persist if the UE remains with the same LTE master cell. In such instances, the UE may be unable to acquire data service in the area at least for a significant time. It may be desirable to change the behavior of the UE so that the UE may acquire data service earlier.

FIG. 6 illustrates an example UE operation of fast detect and recovery from dual-connectivity data stall in accordance with aspects of the present disclosure. In certain aspects, operation 600 illustrated in FIG. 6 may be done by a UE 120. According to the operation 600 in FIG. 6, the UE may attach to a first radio access technology (RAT) , wherein the attaching comprises establishing a connection with a base station (BS) of the first RAT and indicating to the BS that the UE is capable of dual-connectivity. In an aspect, dual connectivity may allow a UE to simultaneously transmit and receive data on multiple component carriers from two cell groups via a master node and a secondary node. Dual connectivity may include but is not limited to multi-radio dual connectivity (MR-DC) , E-UTRAN new radio (NR) dual connectivity (EN-DC) , NG-RAN E-UTRA-NR dual connectivity (NGEN-DC) , NR E-UTRA (NE-DC) , and NR-NR dual connectivity (NR-DC) .

According to the operation 600 in FIG. 6, in step 610, the UE may determine that a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold. In certain aspects, UE may detect a PDCP SN fluctuation when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold. In an aspect, the prior data packet used for detecting PDCP SN fluctuation may be a data packet immediately prior to the data packet that it is compared with. The second threshold may be a predetermined value or may be dynamic depending on various factors based on but not limited to channel condition, UE capability, etc. In an aspect, the second threshold may signify a PDCP SN change between packets that may be out of the ordinary. In an aspect, the UE may count the number of times that PDCP SN fluctuation is detected to determine whether the number of PDCP SN fluctuation exceeds the first threshold. The first threshold may be a predetermined value or may be dynamic depending on various factors based on but not limited to channel condition, priority of connection/data, etc. In an aspect, the first threshold may signify a number of PDCP SN fluctuations that may likely result in the repeated RLF that may occur if not addressed. According to the operation 600 in FIG. 6, in step 615, the UE may trigger radio link failure (RLF) based on the determining. In certain aspects, the UE may trigger RLF when the UE determines that the number of PDCP SN within the first detecting duration is greater than the first threshold. In an aspect, the first detecting duration is a time duration. According to the operation 600 in FIG. 6, in step 620, the UE may re-establish the connection with the BS. In certain aspects, the UE may attempt to re-establish the connection in response to triggering RLF.

According to the operation 600 in FIG. 6, in step 625, the UE may detach then attach to the first RAT after the re-establishing, wherein attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination, after the re-establishing, that a number of detected PDCP SN fluctuation in a second detecting duration is greater than the first threshold. In certain aspects, the UE may detach then attach to the first RAT indicating that the UE is not capable of dual-connectivity. In an aspect, the UE by indicating that the UE is not capable of dual-connectivity may only be connected to the first RAT and the dual connection may not be attempted by the BS and/or UE. By establishing a non dual-connectivity connection with only the first RAT, the UE may not observe the PDCP SN fluctuation associated with the RLF and thus avoid further RLF. In an aspect, the UE may indicate that the UE is not capable of dual-connectivity by sending to the BS an attach accept message with dual-connectivity disabled. In certain aspects, the UE may detach and attach after the re-establishing if the UE determines that the number of PDCP SN fluctuation within the second detecting duration but after the re-establishing is greater than the first threshold. In an aspect, the second detecting duration may be the equal to the first detecting duration. In an aspect, a UE observing the RLF with PDCP SN fluctuation after re-establishing connection may signify that declaring RLF and re-establishing connection may not solve the issue and may likely see repeated RLF again.

According to the operation 600 in FIG. 6, in step 630, the UE may optionally start a timer based on the indicating that the UE is not capable of dual connectivity. In certain aspects, the UE may start the timer when the UE sends the indication or after. According to the operation 600 in FIG. 6, in step 635, the UE may optionally detach then attach to the first RAT based on expiry of the timer, wherein attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity. In certain aspects, the UE may detach then attach indicting that the UE is capable of dual-connectivity when the timer expires or after. In an aspect, the UE may indicate that the UE is capable of dual-connectivity by sending to the BS an attach accept message with dual-connectivity enabled. In an aspect, timer expiry may indicate that sufficient time has passed where RLF with PDCP SN fluctuation may not be observed.

FIG. 7 illustrates an example UE flow chart of fast detect and recovery from EN-DC data stall in accordance with aspects of the present disclosure. According to the flow chart 700 in FIG. 7, the UE may register to a network with EN-DC capability enabled. For example, the UE may send an attach accept message with DC-NR parameter set to 1. The UE may detect frequent PDCP SN fluctuation during and/or after attach. Frequent PDCP SN fluctuation may be detected by detecting more than a threshold number of PDCP SN fluctuations within a time duration. The PDCP SN fluctuation may be observed by observing the difference in PDCP SN of close in time data packets being larger than a threshold. If frequent PDCP SN fluctuation is not detected, the UE may keep the EN-DC capability enabled. If not, the UE may trigger RLF and re-establish the RRC connection. If the UE detects frequent PDCP SN fluctuation again after UE re-establishes the RRC connection, then the UE may detach and then attach with EN-DC capability disabled. For example, the UE may attach with DC-NR parameter set to 0 or disabled in the attach accept message. However, if the UE does not see frequent PDCP SN fluctuation again after the re-establishment, the UE may keep the connection with EN-DC capability enabled. The UE may optionally start an ENDC_Forbid_Timer when attaching with EN-DC capability disabled. While the ENDC_Forbid_Timer is running the UE may keep the EN-DC capability disabled. If ENDC_Forbid_Timer expires, the UE may detach and attach with EN-DC capability enabled.

FIG. 8 illustrates a communications device 800 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 6, and other aspects described herein and illustrated in the drawings. The communications device 800 includes a processing system 802 coupled to a transceiver 808. The transceiver 808 is configured to transmit and receive signals for the communications device 800 via an antenna 810, such as the various signals as described herein. The processing system 802 may be configured to perform processing functions for the communications device 800, including processing signals received and/or to be transmitted by the communications device 800.

The processing system 802 includes a processor 804 coupled to a computer-readable medium/memory 812 via a bus 806. In certain aspects, the computer-readable medium/memory 812 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 804, cause the processor 804 to perform the operations illustrated in FIG. 6, or other operations for performing the various techniques discussed herein. In certain aspects, computer-readable medium/memory 812 stores code 814 for detecting frequent PDCP SN fluctuations in a first detecting duration. In certain aspects, computer-readable medium/memory 812 stores code 816 for determining to detach and attach with either dual connectivity disabled based on the whether the number of detected frequent PDCP SN fluctuation in a first detecting duration exceed a threshold. In certain aspects, computer-readable medium/memory 812 stores code 818 for triggering RLF based on the determining.

In certain aspects, the processor 804 has circuitry configured to implement the code stored in the computer-readable medium/memory 812. The processor 804 includes circuitry (not illustrated) for detecting frequent PDCP SN fluctuations in a first detecting duration, determining to detach and attach with either dual connectivity disabled based on the whether the number of detected frequent PDCP SN fluctuation in a first detecting duration exceed a threshold, and triggering RLF based on the determining.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or. ” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. As used herein, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” For example, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. Unless specifically stated otherwise, the term “some” refers to one or more. 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) . As used herein, including in the claims, the term “and/or, ” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language claims. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

For example, means for transmitting and/or means for receiving may comprise one or more of a transmit processor 420, a TX MIMO processor 430, a receive processor 438, or antenna (s) 434 of the base station 110 and/or the transmit processor 464, a TX MIMO processor 466, a receive processor 458, or antenna (s) 452 of the user equipment 120. Additionally, means for obtaining, means for designating, means for aggregating, means for collecting, means for selecting, means for switching, and means for detecting may comprise one or more processors, such as the controller/processor 480, transmit processor 464, receive processor 458, and/or MIMO processor 466 of the user equipment 120.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, phase change memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

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

attaching to a first radio access technology (RAT) , wherein the attaching comprises establishing a connection with a base station (BS) of the first RAT and indicating to the BS that the UE is capable of dual-connectivity;

determining a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold, wherein a PDCP SN fluctuation is detect when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold;

triggering radio link failure (RLF) based on the determining;

re-establishing the connection with the BS; and

detaching then attaching to the first RAT after the re-establishing, wherein attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination, after the re-establishing, that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold.
The method of claim 1, further comprising:

starting a timer based the indicating that the UE is not capable of dual-connectivity; and

detaching then attaching to the first RAT based on expiry of the timer, wherein attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity.
The method of claim 1, wherein the indicating that the UE is not capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity disabled.
The method of claim 2, wherein the indicating that the UE is capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity enabled
The method of claim 1, wherein the prior data packet is an immediately prior data packet to the data packet.
A user equipment (UE) for wireless communication capable of dual-connectivity, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

attach to a first radio access technology (RAT) , wherein the attaching comprises establishing a connection with a base station (BS) of the first RAT and indicating to the BS that the UE is capable of dual-connectivity;

determine a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold, wherein a PDCP SN fluctuation is detect when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold;

trigger radio link failure (RLF) based on the determining;

re-establish the connection with the BS; and

detach then attach to the first RAT after the re-establishing, wherein attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination, after the re-establishing, that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold.
The UE of claim 6, the at least one processor coupled to the memory and configured to further:

start a timer based the indicating that the UE is not capable of dual-connectivity; and

detach then attach to the first RAT based on expiry of the timer, wherein attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity.
The UE of claim 6, wherein the indicating that the UE is not capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity disabled.
The UE of claim 7, wherein the indicating that the UE is capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity enabled
The UE of claim 6, wherein the prior data packet is an immediately prior data packet to the data packet.
An apparatus for wireless communication performed by a user equipment (UE) capable of dual-connectivity, comprising:

means for attaching to a first radio access technology (RAT) , wherein the attaching comprises establishing a connection with a base station (BS) of the first RAT and indicating to the BS that the UE is capable of dual-connectivity;

means for determining a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold, wherein a PDCP SN fluctuation is detect when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold;

means for triggering radio link failure (RLF) based on the determining;

means for re-establishing the connection with the BS; and

means for detaching then attaching to the first RAT after the re-establishing, wherein attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination, after the re-establishing, that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold.
The apparatus of claim 11, further comprising:

means for starting a timer based the indicating that the UE is not capable of dual-connectivity; and

means for detaching then attaching to the first RAT based on expiry of the timer, wherein attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity.
The apparatus of claim 11, wherein the indicating that the UE is not capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity disabled.
The apparatus of claim 12, wherein the indicating that the UE is capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity enabled
The apparatus of claim 11, wherein the prior data packet is an immediately prior data packet to the data packet.
A non-transitory computer readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

attach to a first radio access technology (RAT) , wherein the attaching comprises establishing a connection with a base station (BS) of the first RAT and indicating to the BS that the UE is capable of dual-connectivity;

determine a number of detected packet data convergence protocol (PDCP) sequence number (SN) fluctuation within a first detecting duration is greater than a first threshold, wherein a PDCP SN fluctuation is detect when PDCP SN associated with a data packet compared to the PDCP SN associated with a prior data packet to the data packet is greater than a second threshold; trigger radio link failure (RLF) based on the determining;

re-establish the connection with the BS; and

detach then attach to the first RAT after the re-establishing, wherein attaching to the first RAT after the re-establishing comprises indicating that the UE is not capable of dual-connectivity and is based on a second determination, after the re-establishing, that a number of detected PDCP SN fluctuation a second detecting duration is greater than the first threshold.
The non-transitory computer-readable medium of claim 16, the code comprising instructions executable by a processor to further:

start a timer based the indicating that the UE is not capable of dual-connectivity; and

detach then attach to the first RAT based on expiry of the timer, wherein attaching to the first RAT based on expiry of the timer comprises indicating to the BS that the UE is capable of dual-connectivity.
The non-transitory computer-readable medium of claim 16, wherein the indicating that the UE is not capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity disabled.
The non-transitory computer-readable medium of claim 17, wherein the indicating that the UE is capable of dual-connectivity comprises sending to the BS an attach accept message with dual-connectivity enabled
The non-transitory computer-readable medium of claim 16, wherein the prior data packet is an immediately prior data packet to the data packet.