WO2021217492A1

WO2021217492A1 - Recovery method for missing data bearer during handoff in a multi-connectivity mode

Info

Publication number: WO2021217492A1
Application number: PCT/CN2020/087760
Authority: WO
Inventors: Hao Zhang; Jian Li; Chaofeng HUI; Fojian ZHANG
Original assignee: Qualcomm Incorporated
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2021-11-04

Abstract

A method and apparatus are described for a UE to recover from a missing data bearer during handover. The UE receives, from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR). Then, the UE receives, from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell. If the message reconfiguring the UE to attach to the second LTE cell is missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers, the UE transmits, to the second LTE cell, a tracking area update (TAU) request message. The TAU request message may include an indication that the UE supports DCNR.

Description

RECOVERY METHOD FOR MISSING DATA BEARER DURING HANDOFF IN A MULTI-CONNECTIVITY MODE

BACKGROUND

Field

This application relates to management of connectivity for a user equipment (UE) connecting to a wireless network.

Background

As New Radio (NR) networks begin deployment, it is expected that the first wave of networks and devices will be classed as non-standalone (NSA) . NR is often also referred to as 5G. NSA network and devices will be supported by existing E-UTRA, also referred to as LTE or 4G, infrastructure. When operating in an NSA mode, 5G devices can, for example, connect to the NR network for data-throughput improvements and can use LTE for low throughput and/or non-data duties.

SUMMARY

In one aspect, a method for wireless communications comprises receiving, by the UE from the first LTE cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with NR (DCNR) . Then the message continues with receiving, by the UE from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers. Then, the method continues with transmitting, by the UE to the second LTE cell, a tracking area update (TAU) request message. In one example, the message includes an indication that the UE supports DCNR.

In another aspect, a user equipment (UE) comprises a memory, a transceiver, and a processor in communication with the memory and the transceiver. The processor is configured to receive, via the transceiver from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ; receive, via the transceiver from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and transmit, via the transceiver to the second LTE cell, a tracking area update (TAU) request message.

In another aspect, a user equipment (UE) comprises means for receiving, by a user equipment (UE) from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ; means for receiving, by the UE from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and means for transmitting, by the UE to the second LTE cell, a tracking area update (TAU) request message.

In another aspect, a non-transitory, computer-readable medium stores code thereon, the code comprising instructions that, when executed by one or more processors of a user equipment (UE) , instruct the one or more processors to receive, from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ; receive, from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and transmit, to the second LTE cell, a tracking area update (TAU) request message.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGs. 1A and 1B illustrate an example of wireless communications systems in accordance with various aspects of the present disclosure.

FIG. 2 illustrates a sample flow diagram in which a user equipment (UE) that is already attached to an Evolved Universal Terrestrial Radio Access (E-UTRA) or Long-term Evolution (LTE) network or base station can add a connection to a New Radio (NR) or 5G network or base station in a Dual Connectivity (EN-DC) mode.

FIG. 3 illustrates a sample flow diagram in which a UE receives a data bearer configuration that is missing a data bearer and performs a recovery procedure to recover from the missing data bearer.

FIG. 4 illustrates an example method for wireless communications where a UE determines whether to disable a standalone (SA) mode.

FIG. 5 shows a diagram of a system including a device that supports non-standalone (NSA) connectivity in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

FIGs. 1A and 1B illustrate an example of a wireless communications systems in accordance with various aspects of the present disclosure. With reference to FIG. 1A. The wireless communications system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long-Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, a New Radio (NR) network, or a combination thereof. Wireless communication system 100 may support multi-connectivity UE but may not support a standalone mode for the UE to connect to the network via a first radio access technology (RAT) , e.g., NR. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology. Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations) . The UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

Each base station 105 may be associated with a particular geographic coverage area 120 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 120 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions, from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

The geographic coverage area 120 for a base station 105 may be divided into sectors making up only a portion of the geographic coverage area 120, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 120. In some examples, different geographic coverage areas 120 associated with different technologies may overlap and overlapping geographic coverage areas 120 associated with different technologies may be supported by the same base station 105 or by different base stations 105. For example, the same base station 105 or different base stations 105 may be configured to communicate using multiple radio access technologies (RATs) , such as 5G NR and 4G LTE, simultaneously, and the coverage areas 120 associated with the multiple RATs may overlap completely or partly. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 120.

The term “cell” refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) , and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) ) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband Internet-of-Things (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of devices. In some cases, the term “cell” may refer to a portion of a geographic coverage area 120 (e.g., a sector) over which the logical entity operates. Furthermore, a single physical base station 105 may be associated with more than one cell. For example, one cell can be associated with a master node (and can be referred to as a PCell) where another cell is associated with a secondary node (and can be referred to as a PSCell) . In some implementations, both the PCell and the PSCell can have equipment installed on the same base station 105. In one example, the PCell can be an LTE cell and the PSCell can be an NR cell associated with the same base station 105. In another example, the PCell can be an NR cell operating in a first frequency range and the PSCell can also be an NR cell but operating in a second frequency range different than the first frequency range, and both cells can be associated with the same base station 105.

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

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices, and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication) . M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs 115 may be designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications) . In some cases, UEs 115 may be designed to support critical functions (e.g., mission critical functions) , and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

In some cases, a UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol) . One or more of a group of UEs 115 utilizing D2D communications may be within the geographic coverage area 120 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 120 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some cases, groups of UEs 115 communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE 115 transmits to every other UE 115 in the group. In some cases, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1 or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2 or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .

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

At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC) . Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP) . In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105) .

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

Wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that can tolerate interference from other users.

Wireless communications system 100 may also operate in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz) , also known as the millimeter band. In some examples, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE 115 (e.g., for multiple-input multiple-output (MIMO) operations such as spatial multiplexing, or for directional beamforming) . However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. Techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

In some cases, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 may employ LTE License Assisted Access (LTE-LAA) or LTE-Unlicensed (LTE-U) radio access technology or NR technology in an unlicensed band such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with component carriers (CCs) operating in a licensed band. Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) , or a combination of both.

In some cases, the antennas of a base station 105 or UE 115 may be located within one or more antennas or antenna arrays, which may support MIMO operations such as spatial multiplexing, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

MIMO wireless systems use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115) , where both transmitting device and the receiving device are equipped with multiple antennas. MIMO communications may employ multipath signal propagation to increase the utilization of a radio frequency spectrum band by transmitting or receiving different signals via different spatial paths, which may be referred to as spatial multiplexing. The different signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the different signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the different signals may be referred to as a separate spatial stream, and the different antennas or different combinations of antennas at a given device (e.g., the orthogonal resource of the device associated with the spatial dimension) may be referred to as spatial layers.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105 or a UE 115) to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a direction between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying certain phase offset, timing advance/delay, or amplitude adjustment to signals carried via each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation) .

In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For instance, signals may be transmitted multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. A receiving device (e.g., a UE 115, which may be an example of a mmW receiving device) may try multiple receive beams when receiving various signals from the base station 105, such as synchronization signals or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive beams or receive directions.

In some cases, wireless communications system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may in some cases perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

In some cases, UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique of increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC) ) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) . HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., signal-to-noise conditions) . In some cases, a wireless device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of Ts = 1/30,720,000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (Tf = 307200 *Ts) . The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include ten subframes numbered from 0 to 9, and each subframe may have a duration of 1 millisecond. A subframe may be further divided into two slots each having a duration of 0.5 milliseconds, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases a subframe may be the smallest scheduling unit of the wireless communications system 100, and may be referred to as a transmission time interval (TTI) . In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs) .

In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols and in some instances, a symbol of a mini-slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots may be aggregated together for communication between a UE 115 and a base station 105.

A resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier (e.g., a 15 kHz frequency range) . A resource block may contain 12 consecutive subcarriers in the frequency domain (e.g., collectively forming a “carrier” ) and, for a normal cyclic prefix in each orthogonal frequency-division multiplexing (OFDM) symbol, 7 consecutive OFDM symbol periods in the time domain (1 slot) , or 84 total resource elements across the frequency and time domains. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of modulation symbols that may be applied during each symbol period) . Thus, the more resource elements that a UE 115 receives and the higher the modulation scheme (e.g., the higher the number of bits that may be represented by a modulation symbol according to a given modulation scheme) , the higher the data rate may be for the UE 115. In MIMO systems, a wireless communications resource may refer to a combination of a radio frequency spectrum band resource, a time resource, and a spatial resource (e.g., spatial layers) , and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

The term “carrier” refers to a set of radio frequency spectrum resources having a defined organizational structure for supporting uplink or downlink communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that may also be referred to as a frequency channel. In some examples a carrier may be made up of multiple sub-carriers (e.g., waveform signals of multiple different frequencies) . A carrier may be organized to include multiple physical channels, where each physical channel may carry user data, control information, or other signaling.

The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, NR, etc. ) . For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc. ) and control signaling that coordinates operation for the carrier. In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

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

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, or 20 MHz) . In some examples the system bandwidth may refer to a minimum bandwidth unit for scheduling communications between a base station 105 and a UE 115. In other examples a base station 105 or a UE 115 may also support communications over carriers having a smaller bandwidth than the system bandwidth. In such examples, the system bandwidth may be referred to as “wideband” bandwidth and the smaller bandwidth may be referred to as a “narrowband” bandwidth. In some examples of the wireless communications system 100, wideband communications may be performed according to a 20 MHz carrier bandwidth and narrowband communications may be performed according to a 1.4 MHz carrier bandwidth.

Devices of the wireless communications system 100 (e.g., base stations or UEs 115) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. For example, base stations 105 or UEs 115 may perform some communications according to a system bandwidth (e.g., wideband communications) , and may perform some communications according to a smaller bandwidth (e.g., narrowband communications) . In some examples, the wireless communications system 100 may include base stations 105 and/or UEs that can support simultaneous communications via carriers associated with more than one different bandwidth.

Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A UE 115 may be configured with multiple downlink CCs and one or more uplink CCs according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhanced component carriers (eCCs) . An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link) . An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum) . An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power) .

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include use of a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc. ) at reduced symbol durations (e.g., 16.67 microseconds) . A TTI in eCC may consist of one or multiple symbol periods. In some cases, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may use a combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across frequency) and horizontal (e.g., across time) sharing of resources.

UEs 115 may be configured as multi-connectivity UEs in which UEs 115 are configured to communicate with one or more base stations 105 using multiple RATs (e.g., 5G NR, 4G LTE) . UEs 115 may be capable of connecting to the network using 5G NR, however, if a network operator does not support a standalone (SA) mode, the 5G NR-capable UE may then attach to the network using LTE and add an NR base station for additional connectivity where primary control of the connection of the UE to the network is through LTE.

With reference to FIG. 1B, communications system 100′ may implement aspects of wireless communications system 100. For example, wireless communications system 100′ includes an LTE base station 105-A, an NR base station 105-B, and a UE 115-A, which may be examples of the corresponding devices described with reference to FIG. 1A. Wireless communications system 100′ may support the use of techniques where an SA capable UE connects to a network in an NSA mode where, for various reasons, a network operator has not deployed or not yet deployed SA capability in the network.

In wireless communications system 100′, a UE 115-A may communicate with a network using a multi-connectivity, for example, dual-connectivity (DC) configuration. In such cases, UE 115-A may simultaneously communicate with different base stations 105 (e.g., LTE base station 105-A and NR base station 105-B) . LTE base station 105-A may provide a first cell 110-A and LTE base station 105-A may be referred to as a master node (MN) . First cell 110-A may correspond to a PCell in the DC deployment. Additionally, NR base station 105-B may provide a second cell 110-B of the DC configuration, and NR base station 105-B may be referred to as a secondary node (SN) . In some cases, second cell 110-B may correspond to a PSCell in the DC deployment, which may be configured with time-frequency resources for physical downlink control channel (PUCCH) . Additional SCells may be associated with each base station 105-A and 105-B. A master cell group (MCG) may then refer to a group of serving cells associated with the MN, comprising the PCell and optionally one or more SCells, and a secondary cell group (SCG) may then refer to a group of serving cells associated with the SN, comprising the PSCell and optionally one or more SCells. In some implementations, the SCells can provide additional carriers in addition to carriers of the PCell or PSCell for carrier aggregation. In a multi-connectivity implementation, such as dual-connectivity, while the transfer of data is split between the MN and the SN, control of multi-connectivity remains with the MN. Other non-scheduling related control information related to the SN can also be routed through the MN, while scheduling for the SN can be handled by the SN through the SN’s own physical downlink control channel (PDCCH) . Although shown as two different base stations 105-A and 105-B for purposes of illustration, it is understood that in some implementations, the PCell of the MN and the PSCell of the SN may be separate cells that are installed on the same physical base station (and as such, illustrated base stations 105-A and 105-B can be a single base station) .

The UE can indicate to the MN (e.g., LTE base station 105-A) a multi-connectivity (e.g., dual-connectivity) capability informing the MN that the UE (e.g., LTE base station 105-A) supports multi-connectivity. Once the UE is attached to the MN, the MN can initiate a process to add an SN (e.g., NR base station 105-B) connection between the UE and the network. The MN can instruct the UE to make measurements of signals associated with the SN and to report the measurements to MN. If the reported signal measurements suggest that a good communication link between the UE and the SN can be established, the MN provides the UE and the SN with all the parameters for them to establish a connection. The MN can be configured to control whether the SN is added or not.

In some cases, DC deployments may use different radio bearers for transmitted messages for each cell. For instance, when LTE base station 105-A is configured as a master node that provides a set of serving cells corresponding to the MCG, LTE base station 105-A may use a first set of signaling radio bearers (SRBs) (e.g., SRB1, SRB2) to transport messages for the MCG, such as RRC messages. Additionally, when NR base station 105-B is configured as a secondary node, NR base station 105-B may provide another set of serving cells that correspond to the SCG and may use a second set of SRBs (e.g., SRB3) to transport messages for the SCG. In some examples, a split bearer configuration may be supported, where a particular protocol layer (e.g., a packet data convergence protocol (PDCP) layer) for both the master node and secondary node may be used to route data streams to/from UE 115-A. Here, an SRB (e.g., SRB1/SRB2) may be split between the master node and the secondary node, and downlink messages sent from the master node to UE 115-A may be routed via lower-layers (e.g., radio link control (RLC) , medium access control (MAC) , physical (PHY) , etc. ) of either LTE base station 105-A (e.g., the master node) or NR base station 105-B (e.g., the secondary node) . In other cases, downlink messages may be routed via the lower-layers of both the master and secondary nodes. In the uplink, RRC messages from UE 115-A may be transmitted to the master node via the secondary node using the split bearer (e.g., via a “leg” associated with the secondary node) . For the signaling of data in the user plane, respective data radio bearers (DRBs) may be used by the MCG and SCG.

Additionally or alternatively, UE 115-A may communicate with a single base station 105 (e.g., LTE base station 105-A) using multiple carriers (e.g., CCs, which may also be referred to as layers, channels, etc. ) . In such cases, a CC may refer to each of the carriers used by UE 115-A in carrier aggregation (CA) operations. Further, a serving cell of LTE base station 105-A may correspond to each CC used in CA operation, where each serving cell may be different (e.g., based on the path loss experienced by different CCs on different radio frequency (RF) spectrum bands) . In some examples, one carrier may be designated as a primary carrier, or primary CC (PCC) , for UE 115-A, which may be served by a PCell of LTE base station 105-A. Additional carriers may be designated as secondary carriers, or secondary CCs (SCCs) , which may be served by SCells of LTE base station 105-A. CA operations may use the same or different RF bands for communications.

FIG. 2 illustrates a sample flow diagram in which a UE that is already attached to an E-UTRA or LTE network or base station can enter an multi-radio connectivity mode (e.g., EN-DC mode) where a connection to an NR or 5G network or base station is added. It is understood that the sample flow 200 is provided for illustrative purposes, and is merely one example of a scenario where a UE 115 can enter a multi-radio connectivity mode, e.g., a dual connectivity mode, e.g., an EN-DC or DCNR mode, after, for example, a determination that an operator of a network does not support, for example, SA NR. In the particular example provided here, the UE is attached to an LTE network and a connection to an NR network is added. However, it is understood that more generally the UE may attach to the network using a second RAT and add a connection to a first RAT. In one example, the UE attaches to the network using the second RAT in an non-standalone (NSA) mode in which the UE attaches to the network using the second RAT, e.g., LTE, but can also receive data using the first RAT, e.g., NR, in the multi-radio connectivity mode.

Although not discussed in detail with reference to flow 200, it is understood that certain messages, communications, or processes may have occurred prior to 203. For example, a random access procedure or random access control channel (RACH) procedure may have occurred for the UE 115 to gain access to, attach to, and/or be connected to the LTE network 201, for example, through a special cell (SpCell) of the LTE network 201. In addition, after connection is established, the LTE network 201 and the UE may have exchanged data, including downlink (DL) and/or uplink (UL) data, for example, where data exchanged with the network is exchanged using only LTE and is therefore LTE-only traffic. Such data can include control data or configuration data. Furthermore, for a UE that is 5G/NR capable, the UE 115 may indicate such capability to the LTE network 201. For example, in a situation where the network does not support NR in a SA mode, the UE 115 can indicate to the LTE network 201 that it has capability of connecting in EN-DC. As noted above, responsive to the indication by the UE 115 of EN-DC capability, the network 201 can take steps to add a 5G/NR node to enable the UE to exchange data with the 5G/NR node in addition to the LTE node, for example, in an EN-DC mode as described further below.

At 203, the LTE Network 201 can send an addition request to the NR Network 202 (where the addition request, for example, is subsequent to receipt of an indication by the UE of EN-DC capability of the UE 115) . In one example, the addition request can be an SgNB Addition Request message. The LTE Network 201, for example, can determine that the UE 115 is in a good signaling environment for NR signals based on measurements by the UE 115 of reference signals measured, for example, based on an RRC configuration sent to the UE 115 from the LTE Network 201. The addition request can serve as a resource request, in which the LTE Network 201 requests the NR Network 202 to allocate resources for the UE 115. As such, the addition request, may include information to enable the NR Network 202 to determine whether it can accommodate the resource allocation request, for example, reference signal measurements of NR signals reported by the UE 115 to the LTE Network 201 as well as other information useful to the NR Network 202 to determine whether it can accept the request.

At 206, if the NR Network 202 is able to admit the resource request, it can respond to the addition request message with an acknowledge message, for example, an SgNB Addition Request Acknowledge message. The NR Network 202 can decide the PSCell and other SCG SCells and, for example, provide a new SCG radio resource configuration to the LTE Network 201 in an NR RRC configuration message, which can be contained in some embodiments, in the SgNB Addition Request Acknowledge message.

At 209, the LTE Network 201 can send to the UE 115 an RRCConnectionReconfiguration message which can, for example, include the NR RRC configuration message received from the NR Network 202. The RRCConnectionReconfiguration and/or NR RRC configuration message can include an NR DRB configuration, a PDCP configuration (e.g., in a PDCP-Config information element) , and/or the like. The UE 115 can then apply the new configuration and, at 212, reply to the LTE Network 201 with an RRCConnectionReconfigurationComplete message. If, for some reason, the UE 115 is unable to comply with the configuration included in the RRCConnectionReconfiguration message, it can perform a reconfiguration failure procedure (not shown at 212) . In one example, performing the reconfiguration failure procedure can include the UE 115 sending a SCGFailureInformationNR message to the LTE Network 201 (not shown at 212) and setting a failure type in the message to correspond to a failure type associated with RRC reconfiguration failure, such as, for example, scg-reconfigFailure. In one implementation, when there is an RRC reconfiguration failure, the UE 115 does not apply any part of the reconfiguration and continues using the configuration it was using prior to the RRCConnectionReconfiguration message of 209. Where the reconfiguration fails, the UE remains connected to the LTE Network 201 and does not connect to the NR Network 202 (for example, does not connect to NR Network 202 in the EN-DC mode) .

At 215 the LTE Network 201 can send a reconfiguration complete message to the NR Network 202 to inform the NR Network 202 that the reconfiguration of the UE 115 was successful. In one example, such a message can be a SgNB ReconfigurationComplete message. This reconfiguration complete message can include, for example, any information provided to the LTE Network 201 from the UE 115, for example, in the RRCConnectionReconfigurationComplete message of 212.

At 218, the UE 115 performs registration with the NR Network 202. In one example, the UE can perform registration procedure through a SpCell of the SN (also referred to as a PSCell) . Aspects of registration to the 5G network can include synchronization of downlink framing, RACH procedure, and initial scheduling of data to be communicated over the NR Network 202. Once registration is complete, the UE 115 is connected to the NR Network 202. In this example, the UE 115 is now connected to both the LTE Network 201 and the NR Network 202.

At 221, the UE 115 can communicate with the LTE Network 201. Simultaneously, at 224, the UE 115 can also communicate with the NR Network 202. Since, typically, the SN has greater data throughput capacity, data communications between the UE 115 and the NR Network 202 at 224 can include data associated with high throughput, real time applications such as video streaming or virtual/augmented reality, to name a few examples. Otherwise, low throughput applications can, for example, be routed through the LTE Network 201 as shown in 221. In one implementation, only the MN provides control plane connection to the core network which, in the illustrated embodiment is the LTE MN of the LTE Network 201. Since the UE 115 is now in an EN-DC mode, UE 115 is connected to both LTE Network 201 and NR Network 202 in a dual connection mode. In one example scenario of a dual connection mode, the UE 115 can send and receive control and user data with the LTE Network 201 (including non-scheduling control data related to the NR Network 202) , but only sends and receives user data (along with scheduling related to the user data) to/from the NR Network 202. The data sent over the NR Network 202 can include PDCP packets sent over the NR Network 202. Although 221 is illustrated as labeled “LTE data traffic, ” it is understood that traffic sent over LTE can include data as well as control for both the LTE connection as well as non-scheduling control data related to the NR Network 202.

FIG. 3 illustrates a sample flow diagram in which a UE receives a data bearer configuration that is missing a data bearer, e.g., a default evolved packet system (EPS) bearer, and performs a recovery procedure to recover from the missing data bearer.

In the illustrated example of FIG. 3, it is understood that UE 115 is already connected to LTE Cell1 302, which is a dual connectivity with NR (DCNR) capable LTE cell, and further than UE 115 is an NR capable UE and that the UE 115 is capable of being connected to LTE Cell1 302 in an NR non-standalone (NSA) mode similar to that described with reference to FIG. 2. In FIG. 3, the UE 115 can be connected to both LTE Cell1 302 and an NR cell (not illustrated in FIG. 3) . Flow 300 then begins at 310 where the UE 115 is configured with a plurality of data bearers, for example, EPS data bearers. In the illustrated example, the EPS data bearers are assigned identifiers (IDs) 5, 6, and 7.

At 312, the UE 115 provides a measurement report to LTE Cell1 302 comprising measurements of signals transmitted by LTE Cell2 303, either as a part of periodic measurements reports provided to LTE Cell1 302 configured by RRC or a triggered measurement report in response to a configuration or request by LTE Cell1 302 to provide the measurement report. Such periodic or triggered reports can be based on a configuration received in an RRC reconfiguration message configuring the UE 115 to make measurements and send a report based on a certain criteria or periodically and/or the like. LTE Cell1 may configure and/or trigger measurement reports comprising measurements of signals transmitted by LTE Cell2 303 to enable LTE Cell1 302 to make a handover determination. For example, based on the measurement report of 312, if LTE Cell1 302 determines that the UE 115 is in a signaling environment where UE 115 receives a stronger signal from LTE Cell2 303, LTE Cell1 302 may determine to handover the LTE connection (as well as control of the NR connection as described above) to LTE Cell2 303.

After the RRC reconfiguration of 314, at 316 a handover process begins to handover the LTE connection from LTE Cell1 302 to LTE Cell2 303. Although not illustrated in detail, it is understood that the handover process can include steps such as communications between LTE Cell1 302 and LTE Cell2 303 to determine the load on LTE Cell2 303 (e.g., a resource status request message and/or the like) , transmitting by the LTE Cell1 302 to the LTE Cell2 303 information (e.g., a handover request message and/or the like) to enable the handover at LTE Cell2 303 (e.g., UE context information, security context information, radio bearer context information, E-UTRAN Radio Access Bearer (E-RAB) to radio bearer mapping, and/or the like) , reservation of resources by LTE Cell2 303, transmitting by the LTE Cell2 303 to the LTE Cell1 302 information (e.g., handover request acknowledge message and/or the like) to enable the UE 115 to perform a RACH procedure with the LTE Cell2, transmitting by the LTE Cell1 302 to the UE 115 an RRC reconfiguration message, transmitting by LTE Cell1 302 to LTE Cell2 303 downlink data packet for all data bearers, and/or accessing by the UE 115 the LTE Cell2 303 using a non-contention-based Random Access Channel (RACH) procedure, transmitting by the LTE Cell2 303 a request to release resources (e.g., a UE context release message) , and/or the like, as well as the communication of messages between LTE Cell1 302 and LTE Cell2 303 and entities in the core network such as the MME, the SGW, the PDN, and/or the like. If the RACH procedure is successful, at 318 LTE Cell2 303 transmits an RRCConnectionReconfiguration message to the UE 115 to configure the UE 115 for the new connection to LTE Cell2 303. In the illustrated example of FIG. 3, the RRCConnectionReconfiguration message of 318 includes data bearer information, e.g., EPS data bearers assigned IDs 6 and 7, but is missing a missing data bearer, e.g., EPS data bearer assigned ID 5. One reason that RRCConnectionReconfiguration message of 318 can be missing one or more data bearers includes a bearer context transfer failure, for example, where LTE Cell1 302 and LTE Cell2 303 are controlled by two different radio network controllers (RNCs) and the bearer context information, E-RAB to radio bearer mapping, and/or the like could not transfer correctly between the two LTE cells in view of the different RNCs.

At 320, the UE 115 removes the missing data bearer. In the illustrated example, EPS data bearer ID 5 is a default bearer and hence all default PS data depends upon proper configuration of this EPS data bearer, which can include an IP address to enable the UE 115 to communicate with the PDN. As such, the data bearer missing from the RRCConnectionReconfiguration message of 318 can result in degradation in service to the UE 115. In the example of the message of 318 missing the EPS data bearer ID 5, this means that PS data service can be affected. In other examples, where the missing EPS bearer is bearer ID 6 or 7, other aspects of service to the UE 115 can be affected such as any service that uses IMS, such as voice over IP (VoIP) and others. As such, to maintain proper service to the UE 115, the UE 115 can try to get the network to establish the EPS bearer.

In response to the missing data bearer, the UE 115 may perform a recovery procedure at 322. For example, as shown, at 324, the UE 115 may transmit to the LTE Cell2 303 a PDN connectivity request in order for the UE 115 to request the set up of a default EPS bearer to a PDN. If the PDN connectivity request is accepted by the network, the network initiates the establishment of a default EPS bearer context activation procedure.

Once the PDN connectivity request of 324 is transmitted, the UE 115 can set a timer, e.g., a PDN response timer. Once the timer expires, the UE 115 may try and send another PDN connectivity request 324. The UE 115 may try to send the PDN connectivity request at 324 several times, e.g., a Loop _max number of times. If after each request is sent, a new timer is started, and each timer expires without a network response, then the UE 115 moves from recovery procedure 322 to another recovery procedure using tracking area update (TAU) messages. As such, if, as shown 326, no response is received from the network and the timer has expired, flow 300 moves to 327 to determine whether the UE 115 has looped through PDN connectivity request and timer expiration a Loop _max number of times. If the PDN connectivity request has not been resent a Loop _max number of times, the flow returns to 324 and the UE 115 transmits another PDN connectivity request. However, if the UE 115 has transmitted a Loop _max number of PDN connectivity requests and each time a timer has expired with no response from the network, then flow 300 moves from 327 to 328 where another recovery procedure using TAU messages can be used.

At 328, the UE 115 transmits a TAU request to LTE Cell2 303. In one example, the TAU request includes an indication that the UE 115 supports DCNR. In one example, the TAU request message can provide such an indication to the LTE cell 302 by setting a DCNR bit to “dual connectivity with NR supported” in a UE Network capability information element (IE) of the TAU request message. For example, when the value of the bit is zero (0) , the bit indicates that the UE does not support DCNR, and when the value of the bit is one (1) , the bit indicates that the UE does support DCNR. Hence, at 328, in one implementation, the DCNR bit can be set to one (1) .

The TAU request message of 328 may help to resynchronize the UE 115 with the network. As such, after the UE 115 receives a TAU accept message at 330 from the LTE Cell2 303, the UE 115 may again send a PDN connectivity request message similar to the message sent at 324. If successful, the LTE Cell2 303 can respond (e.g., transmit) with an activate bearer context request message at 334 including information for the data bearer missing from 318, e.g., EPS bearer assigned ID 5. The UE 115 receives the activate bearer context request message. Responsive to the activate bearer context request message of 334, the UE 115 can respond with an activate bearer context accept message at 336.

FIG. 4 illustrates an example method 400 for wireless communications by a user equipment (UE) for recovering from a missing data bearer during a handover while in a multi-connectivity mode, e.g., a dual connectivity mode such as ENDC/DCNR. Method 400 begins at 410 with receiving, by the UE from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) . In one example, the message indicating that the UE is to attach to a second LTE cell capable of supporting DCNR can include an RRC connection reconfiguration message (received from LTE Cell1 302) similar to that discussed above at 314 with reference to FIG. 3.

Method 400 continues at 420 with receiving, by the UE from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers. In one example, the message reconfiguring the UE to attach to the second LTE cell that is missing at least one missing EPS bearer of one or more active EPS bearers can include an RRC connection reconfiguration message (received from LTE Cell2 303) similar to that of 318 with reference to FIG. 3, an RRCConnectionReestablishment message, and/or the like. In one example, the at least one missing EPS bearer is an EPS bearer assigned ID 5.

Method 400 continues at 430 with transmitting, by the UE to the second LTE cell, a tracking area update (TAU) request message. In one example, the TAU request message can include an indication that the UE supports DCNR. In one example, the TAU request message can include a TAU request message similar to that of 328 with reference to FIG. 3.

In one implementation, method 400 can optionally include at 440, before transmitting the TAU request message at 430, transmitting, by the UE to the second LTE cell, one or more initial PDN connectivity requests, wherein transmitting the TAU request message comprises transmitting the TAU request message responsive to not receiving a response from the second LTE cell to any of the one or more initial PDN connectivity requests before a timer expires. In one example, transmitting one or more initial PDN connectivity requests can include transmitting a PDN connectivity request similar to that of 322 and 324. In one example, the one or more initial PDN connectivity requests are five (5) initial PDN connectivity requests. A subsequent initial PDN connectivity request is transmitted responsive to not receiving the response from the second LTE cell before a timer corresponding to each of the initial PDN connectivity requests expires. If a timer expires before any response from the network and/or the second LTE cell after each of the, for example, five initial PDN connectivity requests, the method 400 can then proceed to block 430. In the description above, the initial PDN connectivity requests are referred to as “initial” to indicate that they occur before sending a TAU request.

Whether method 400 includes optional block 440, or proceeds through 410, 420 and 430 without including block 440, method 400 optionally continues at 450 with receiving, by the UE from the second LTE cell, a TAU accept message. In one example, the TAU accept message can be similar to the TAU accept message of 330 with reference to FIG. 3.

Method 400 optionally proceeds from block 450 to block 460 with, responsive to the TAU accept message, transmitting, by the UE to the second LTE cell, an after TAU request PDN connectivity request. The after TAU request PDN connectivity request is transmitted after the TAU request as opposed to the initial PDN connectivity request (s) which occur before the TAU request. The after TAU request PDN connectivity request can be similar to the PDN connectivity request of 332 with reference to FIG. 3.

Method 400 optionally proceeds from block 460 to block 470 with receiving, by the UE from the second LTE cell, a message activating the at least one missing EPS bearer. In one example, the message activating the at least one missing EPS bearer can include an activate bearer context request accept message similar to that of 336 with reference to FIG. 3.

Means for performing the functionality of any of the aspects described with reference to FIG. 4-such as

blocks

410, 420, 430, 440, 450, 460, and/or 470-can, but not necessarily, include antenna 540, transceiver 535, bus 510, UE communications manager 515, modem manager 516, modem manager 517, processor 520, and/or memory 525 with reference to FIG. 5. It is understood above that the UE may transmit and receive via a transceiver, for example transceiver 535.

FIG. 5 shows a diagram of a system 500 including a device 505 that supports non-standalone (NSA) connectivity in accordance with aspects of the present disclosure. Device 505 may be an example of or include the components of UE 115 as described above, e.g., with reference to FIGs. 1 through 4. Device 505 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE communications manager 515, processor 520, memory 525, software 530, transceiver 535, antenna 540, I/O controller 545, and I/O component (s) 550. These components may be in communication (e.g., electronic communication) , or coupled, via one or more buses (e.g., bus 510) . To power the other components, device 505 may include a battery 555. Device 505 may communicate wirelessly with one or more base stations, for example base station 105-A and 105-B (as described above, for example, with reference to FIG. 1B) .

UE communications manager 515 of FIG. 5 may include a modem manager 516 associated with a master node and a modem manager 517 associated with a secondary node. In scenarios where the MN and SN operate using different RATs, modem manager 517 can, for example, be associated with a first RAT, such as NR, while modem manager 516 can, for example, be associated with a second RAT, such as LTE. As such, modem manager 516 can provide for management of aspects of the communications between the UE and the LTE cell in FIGs. 2, 3, and 4.

Processor 520 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU) , a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, processor 520 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 520. Processor 520 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks recovery from missing data bearer during handoff) . Information such as operating system (OS) information, application statistics, application throughputs, temperatures, battery charge or voltage status may be inter-communicated between various parts of device 505 via bus 510 and the inter- communication may incorporate an interface such as a modem to application processor interface.

Memory 525 may include random access memory (RAM) and read only memory (ROM) . The memory 525 may be a non-transitory computer-readable medium storing store computer-readable, computer-executable code or software 530 including instructions that, when executed, instruct a processor (e.g., processor 520, UE communications manager 515) to perform various functions described herein, for example, as described in FIGs. 2, 3, and/or 4. In some cases, the memory 525 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

Software 530 may include code to implement aspects of the present disclosure, including code to support recovery from missing data bearer during handover in a multi-connectivity mode. Software 530 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 530 may not be directly executable by a processor but may instruct a computer (e.g., when compiled and executed) to perform functions described herein, for example, as described in FIGs. 2, 3, and/or 4.

Transceiver 535 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 535 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 535 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets from signals received from the antennas. As such, transceiver 535 can be in communication with processor 520 and enable the processor 520 to transmit and receive messages via the transceiver 535. In one example, transceiver 535 may include multiple modems (separate or integrated) associated with multiple RATs. For example, transceiver 535 may include at least a 5G /NR modem and a 4G /LTE modem, although it is understood that, in other implementations, a single modem may perform modulation/demodulation for both 5G and 4G. In such a single modem implementation, it is understood that it may be possible to reduce power or power down certain subcomponents of the single modem.

In some cases, the wireless device may include a single antenna 540. However, in some cases the device may have more than one antenna 540, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. Additionally or alternatively, antenna (s) 540 can include one or more antenna arrays, where each antenna array comprises a plurality of antenna elements.

I/O controller 545 may manage input and output signals for device 505. I/O controller 545 may also manage peripherals not integrated into device 505. In some cases, I/O controller 545 may represent a physical connection or port to an external peripheral. In some cases, I/O controller 545 may utilize an operating system such as

or another known operating system. In other cases, I/O controller 545 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller 545 may be implemented as part of a processor. In some cases, a user may interact with device 505 via I/O controller 545 or via hardware components controlled by I/O controller 545.

I/O component (s) 550 may include various components and/or parts that enable interaction with device 505. For example, I/O components (s) may include a screen, touchscreen, speaker, microphone, keyboard or other I/O device.

Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single carrier frequency division multiple access (SC-FDMA) , and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA) , etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD) , etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM) .

An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB) , E-UTRA, Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS) . LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM are described in documents from the 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 systems and radio technologies mentioned above as well as other systems and radio technologies. While aspects of an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications.

The wireless communications system 100 or systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timing, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timing, and transmissions from different base stations 105 may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

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

The various illustrative blocks and modules described in connection with the disclosure herein 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 conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

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

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

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

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

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

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

Claims

A method for wireless communications by a user equipment (UE) comprising:

receiving, by the UE from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ;

receiving, by the UE from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and

transmitting, by the UE to the second LTE cell, a tracking area update (TAU) request message.
The method of claim 1, further comprising transmitting, by the UE to the second LTE cell, before transmitting the TAU request message, one or more initial PDN connectivity requests, wherein transmitting the TAU request message comprises transmitting the TAU request message responsive to not receiving a response from the second LTE cell to any of the one or more initial PDN connectivity requests before the a timer expires.
The method of claim 2, wherein the one or more initial PDN connectivity requests comprise five initial PDN connectivity requests and wherein a subsequent initial PDN connectivity request is transmitted responsive to not receiving the response from the second LTE cell before the timer corresponding to each of the initial PDN connectivity requests expires.
The method of any of claims 1 or 2, further comprising:

receiving, by the UE from the second LTE cell, a TAU accept message; and

responsive to the TAU accept message, transmitting, by the UE to the second LTE cell, an after TAU request PDN connectivity request; and

receiving, by the UE from the second LTE cell, a message activating the at least one missing EPS bearer.
The method of any of claims 1 to 4, wherein the TAU request message includes an indication that the UE supports DCNR.
The method of any of claims 1 to 5, wherein the at least one missing EPS bearer comprises an EPS bearer assigned an identifier (ID) of 5.
A user equipment (UE) comprising:

a memory;

a transceiver; and

a processor in communication with the memory and the transceiver, the processor configured to:

receive, via the transceiver from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ;

receive, via the transceiver from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and

transmit, via the transceiver to the second LTE cell, a tracking area update (TAU) request message.
The UE of claim 7, the processor further configured to transmit, via the transceiver to the second LTE cell, before transmitting the TAU request message, one or more initial PDN connectivity requests, wherein the processor is configured to transmit the TAU request message responsive to not receiving a response from the second LTE cell to any of the one or more initial PDN connectivity requests before the a timer expires.
The UE of claim 8, wherein the one or more initial PDN connectivity requests comprise five initial PDN connectivity requests and wherein a subsequent initial PDN connectivity request is transmitted responsive to not receiving the response from the second LTE cell before the timer corresponding to each of the initial PDN connectivity requests expires.
The UE of any of claims 7 or 8, the processor further configured to:

receive, via the transceiver the second LTE cell, a TAU accept message; and

responsive to the TAU accept message, transmit, via the transceiver to the second LTE cell, an after TAU request PDN connectivity request; and

receive, via the transceiver the second LTE cell, a message activating the at least one missing EPS bearer.
The UE of any of claims 7 to 10, wherein the TAU request message includes an indication that the UE supports DCNR.
The UE of any of claims 7 to 11, wherein the at least one missing EPS bearer comprises an EPS bearer assigned an identifier (ID) of 5.
An apparatus for wireless communications comprising:

means for receiving, by a user equipment (UE) from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ;

means for receiving, by the UE from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and

means for transmitting, by the UE to the second LTE cell, a tracking area update (TAU) request message.
The apparatus of claim 13, further comprising means for transmitting, by the UE to the second LTE cell, before transmitting the TAU request message, one or more initial PDN connectivity requests, wherein the means for transmitting the TAU transmits the TAU request message responsive to not receiving a response from the second LTE cell to any of the one or more initial PDN connectivity requests before a timer expires.
The apparatus of any of claims 13 or 14, further comprising:

means for receiving, by the UE from the second LTE cell, a TAU accept message; and

means for, responsive to the TAU accept message, transmitting, by the UE to the second LTE cell, an after TAU request PDN connectivity request; and

means for receiving, by the UE from the second LTE cell, a message activating the at least one missing EPS bearer.
A non-transitory, computer-readable medium storing code thereon, the code comprising instructions that, when executed by one or more processors of a user equipment (UE) , instruct the one or more processors to:

receive, from a first Long-Term Evolution (LTE) cell, a message indicating that the UE is to attach to a second LTE cell capable of supporting dual connectivity with New Radio (NR) (DCNR) ;

receive, from the second LTE cell, a message reconfiguring the UE to attach to the second LTE cell, the message reconfiguring the UE to attach to the second LTE cell missing at least one missing evolved packet system (EPS) bearer of one or more active EPS bearers; and

transmit, to the second LTE cell, a tracking area update (TAU) request message.
The non-transitory, computer-readable medium of claim 16, the instructions further instructing the one or more processors to transmit, to the second LTE cell, before transmitting the TAU request message, one or more initial PDN connectivity requests, wherein the instructions instruct the one or more processors to transmit the TAU request message responsive to not receiving a response from the second LTE cell to any of the one or more initial PDN connectivity requests before a timer expires.
The non-transitory, computer-readable medium of any of claims 16 or 17, the instructions further instructing the one or more processors to:

receive, from the second LTE cell, a TAU accept message; and

transmit, responsive to the TAU accept message, to the second LTE cell, an after TAU request PDN connectivity request; and

means for receiving, by the UE from the second LTE cell, a message activating the at least one missing EPS bearer.