WO2021226942A1

WO2021226942A1 - Restoration of packet switched data when default bearer is removed

Info

Publication number: WO2021226942A1
Application number: PCT/CN2020/090287
Authority: WO
Inventors: Jian Li; Hao Zhang; Chaofeng HUI; Fojian ZHANG; Yi Liu; Yuankun ZHU; Pan JIANG; Jing Zhou; Jingnan QU
Original assignee: Qualcomm Incorporated
Priority date: 2020-05-14
Filing date: 2020-05-14
Publication date: 2021-11-18

Abstract

Certain aspects of the present disclosure provide techniques for restoration of packet switched data when a default bearer is removed. An example method generally includes performing a handover from a first cell to a second cell and receiving, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers. The method further includes removing a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message. The method also includes transmitting, to the second cell, a tracking area update request, which indicates a capability of the UE, after removing the data radio bearer.

Description

RESTORATION OF PACKET SWITCHED DATA WHEN DEFAULT BEARER IS REMOVED

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for restoration of packet switched data when a default bearer is removed.

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc. ) . Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

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. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) . To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

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 an apparatus and various techniques for preventing a stall in packet data network connectivity.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE) . The method generally includes performing a handover from a first cell to a second cell. The method also includes receiving, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers. The method further includes removing a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message. The method also includes transmitting, to the second cell, a tracking area update request, which indicates a capability of the UE, after removing the data radio bearer.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

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 appended 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.

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 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 wireless communication network, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of an example a base station (BS) and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 3A illustrates an example wireless communication network with a standalone 5G wireless network, in accordance with certain aspects of the present disclosure.

FIG. 3B illustrates an example wireless communication network with a non-standalone 5G wireless network, in accordance with certain aspects of the present disclosure.

FIG. 4 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 5 is a signaling flow diagram illustrating example operations for restoring packet data network connectivity, in accordance with aspects of the present disclosure.

FIG. 6 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with 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

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for restoration of packet switched data when a bearer is removed. After a handover and removal of a bearer (e.g., an Evolved Packet System (EPS) bearer identity (ID) ) , the UE may take various actions to restore packet switched (PS) data connectivity. In certain cases, the UE may transmit a tracking area update (TAU) request directly after removal of the bearer. In other cases, the UE may attempt to reconnect the PS data connection with the 4G RAN, and if the T3482 timer expires, the UE may transmit the TAU request. The various actions described herein may enable the UE to prevent an interruption in PS data connectivity after the handover, for example, due to a target cell in the handover not supporting 5G NSA mode and/or removal of the default EPS bearer.

The following description provides examples of restoration of PS data connectivity in communication systems, 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.

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 subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.

The techniques described herein may be used for various wireless networks and radio technologies. While aspects may be described herein using terminology commonly associated with 3G, 4G, and/or new radio (e.g., 5G NR) wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

NR access may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g., e.g., 24 GHz to 53 GHz or beyond) , massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC) . These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe. NR supports beamforming 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.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be a multi-RAT system with support for NR and Evolved Universal Terrestrial Radio Access (E-UTRA) . According to certain aspects, the UE 120a includes a bearer manager 122 that restores and/or prevents a stall in packet data network connectivity upon removal of a certain network bearer (e.g., an Evolved Packet System bearer) following a handover (such as a handover from the BS 110a to the BS 110b) , in accordance with aspects of the present disclosure.

As illustrated in FIG. 1, the wireless communication network 100 may include a number of BSs 110a-z (each also individually referred to herein as BS 110 or collectively as BSs 110) and other network entities. A BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell” , which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. 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 BSs for the

femto cells

102y and 102z, respectively. A BS may support one or multiple cells.

The BSs 110 communicate with UEs 120a-y (each also individually referred to herein as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. Wireless communication network 100 may also include relay stations (e.g., relay station 110r) , also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110) , or that relays transmissions between UEs 120, to facilitate communication between devices.

A network controller 130 may be in communication with a set of BSs 110 and provide coordination and control for these BSs 110 (e.g., via a backhaul) . In aspects, the network controller 130 may be in communication with a core network 132 (e.g., a 5G Core Network (5GC) ) , which provides various network functions such as Access and Mobility Management, Session Management, User Plane Function, Policy Control Function, Authentication Server Function, Unified Data Management, Application Function, Network Exposure Function, Network Repository Function, Network Slice Selection Function, etc.

FIG. 2 illustrates example components of BS 110a and UE 120a (e.g., the wireless communication network 100 of FIG. 1) , which may be used to implement aspects of the present disclosure.

At the BS 110a, a transmit processor 220 may receive data from a data source 212 and control information from a controller/processor 240. 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) , group common PDCCH (GC PDCCH) , etc. The data may be for the physical downlink shared channel (PDSCH) , etc. A medium access control (MAC) -control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a physical downlink shared channel (PDSCH) , a physical uplink shared channel (PUSCH) , or a physical sidelink shared channel (PSSCH) .

The processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols, such as for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , PBCH demodulation reference signal (DMRS) , and channel state information reference signal (CSI-RS) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 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) 232a-232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 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 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120a, the antennas 252a-252r may receive the downlink signals from the BS 110a and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all the demodulators in transceivers 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink 260, and provide decoded control information to a controller/processor 280.

On the uplink, at UE 120a, a transmit processor 264 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 262 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 280. The transmit processor 264 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS) ) . The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the modulators in transceivers 254a-254r (e.g., for SC-FDM, etc. ) , and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas 234, processed by the modulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120a. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to the controller/processor 240.

The

memories

242 and 282 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

Antennas 252,

processors

266, 258, 264, and/or controller/processor 280 of the UE 120a and/or antennas 234,

processors

220, 230, 238, and/or controller/processor 240 of the BS 110a may be used to perform the various techniques and methods described herein. For example, as shown in FIG. 2, the controller/processor 280 of the UE 120a has a bearer manager 281 that restores and/or prevents a stall in packet data network connectivity upon removal of a certain network bearer (e.g., an Evolved Packet System bearer) , according to aspects described herein. Although shown at the controller/processor, other components of the UE 120a and BS 110a may be used to perform the operations described herein.

NR may utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. NR may support half-duplex operation using time division duplexing (TDD) . OFDM and single-carrier frequency division multiplexing (SC-FDM) partition the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. Modulation symbols may be 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 may be dependent on the system bandwidth. The minimum resource allocation, called a resource block (RB) , may be 12 consecutive subcarriers. The system bandwidth may also be partitioned into subbands. For example, a subband may cover multiple RBs. NR may support a base subcarrier spacing (SCS) of 15 KHz and other SCS may be defined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. ) .

FIG. 3A illustrates an example wireless communication network 300A with a standalone (SA) 5G wireless network, in accordance with certain aspects of the present disclosure. As shown, the wireless network 300A may include an Evolved Packet Core (EPC) 332A, a 4G Radio Access Network (RAN) 314A, a 5G Core Network (5GC) 332B, a 5G RAN 314B, and a UE 120. In aspects, the 4G RAN 314A may include one or more base stations (e.g., BS 110) and/or network controllers (e.g., network controller 130) , and the 5G RAN 314B may also include one or more base stations and/or network controllers. The EPC 332A may be in communication with the 4G RAN 314A via a user plane 316A and control plane 318A, and the 4G RAN 314A may be in communication with the UE 120 via the user plane 316A and control plane 318A through over-the-air resources (e.g., frequency-time resources) . In standalone mode, the 5GC 332B may be in communication with the 5G RAN 314B via a user plane 316B and control plane 318B, and the 5G RAN 314B may be in communication with the UE 120 via the user plane 316B and control plane 318B through over-the-air resources (e.g., frequency-time resources) . That is, the standalone 5G network provides a separate core network and 5G RAN as well as separate user plane and control plane traffic for various 5G wireless services (e.g., mmWave, eMBB, URLLC, or mMTC) .

FIG. 3B illustrates an example wireless communication network 300B with a non-standalone (NSA) 5G wireless network, in accordance with certain aspects of the present disclosure. As shown, the wireless network 300B may include an EPC 332A, a 4G RAN 314A, a 5G RAN 314B, and a UE 120. The 5G RAN 314B may be in communication with the

EPC

332A and 4G RAN 314A through the user plane 316B. In other words, the non-standalone 5G wireless network may lack a dedicated 5G core network, but instead rely on the EPC 332A to provide, for example, non-access stratum functions (e.g., mobility management and session management) and a gateway to a packet data network (e.g., the internet) . In aspects, the non-standalone 5G network may also lack a dedicate 5G control plane, such that the control plane for 5G services route through the 4G RAN 314A. In certain cases, the non-standalone 5G network may focus on providing eMBB and mmWave services without support for other 5G services such as URLLC or mMTC.

While the examples depicted in FIGs. 3A and 3B are described herein with respect to separate RANs to facilitate understanding, aspects of the present disclosure may also be applied to co-located and/or integrated RANs. For example, a base station and/or RAN may support various RATs including 2G, 3G, 4G, and/or 5G.

Example Restoration of Packet Switched Data When Default Bearer is Removed

In certain wireless communication systems, a UE may support non-standalone (NSA) 5G mode where control signaling for 4G and 5G services may be carried via the 4G RAN, and 5G data services may be carried via the 5G RAN, for example, as described herein with respect to FIG. 3B. In certain cases, after a handover in NSA mode, the 4G RAN may reconfigure the data radio bearers for a UE, such as removing a default Evolved Packet System (EPS) bearer. After removal of the default EPS bearer, the UE may not be able to reestablish a packet switched (PS) data connection with the 4G RAN or 5G RAN, for example, in certain cases where the target cell in the handover does not support or is not configured for NSA 5G radio access.

As an example, suppose the EPS bearer identities (IDs) 5, 6, and 7 are active on a UE, which is 5G NR capable and supports NSA 5G mode. After a handover from a 4G cell to another 4G cell, the UE may receive, from the 4G RAN, a radio resource control (RRC) reconfiguration message that provides data radio bearers with EPS bearer IDs 6 and 7. In other words, the RRC reconfiguration message provides data radio bearers without the EPS bearer ID 5, which was previously active before the handover, and the UE may remove the data radio bearer associated with the EPS bearer ID 5. The UE may attempt to setup a PS data connection with the 4G RAN by sending a packet data connectivity request to the 4G RAN. With no response from the 4G RAN and upon expiration of the T3482 timer, the UE may send another packet data connectivity request to the 4G RAN. In certain cases, the UE may loop through the transmission of the packet data connectivity request and the expiration of the T3482 timer several times. As a result, the UE may be stuck in a state without PS data connectivity to the 4G RAN and 5G RAN.

Aspects of the present disclosure provide an apparatus and various techniques for restoring PS data connectivity when a bearer is removed. After a handover and removal of a bearer (e.g., an EPS bearer ID) , the UE may take various actions to restore PS data connectivity. In certain cases, the UE may transmit a tracking area update (TAU) request directly after removal of the bearer. In other cases, the UE may attempt to reconnect the PS data connection with the 4G RAN, and if the T3482 timer expires, the UE may transmit the TAU request. The various actions described herein may enable the UE to prevent an interruption in PS data connectivity after the handover, for example, due to a target cell not supporting 5G NSA mode and/or removal of a default EPS bearer.

FIG. 4 is a flow diagram illustrating example operations 400 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 400 may be performed, for example, by UE (e.g., the UE 120a in the wireless communication network 100) . The operations 400 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 400 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 400 may begin, at 402, where the UE may perform a handover from a first cell (e.g., the BS 110a of FIG. 1) to a second cell (e.g., the BS 110b of FIG. 1) . At 404, the UE may receive, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities (IDs) , and the one or more network bearer IDs are missing at least one network bearer ID from an active configuration of the one or more data radio bearers. At 406, the UE may remove a data radio bearer, associated with the at least one missing network bearer ID, from the active configuration of the one or more data radio bearers based on the message. At 408, the UE may transmitting, to the second cell, a tracking area update request, which indicates a capability of the UE, after removing the data radio bearer.

In certain aspects, performing the handover at 402 may involve providing measurements to the first cell and receiving, from the first cell, an indication to perform the handover. For example, the UE may transmit to the first cell measurements of various reference signals (e.g., synchronization signals) from the second cell, and the UE may receive, from the first cell, an RRC connection reconfiguration message indicating to perform the handover to the second cell.

In aspects, the message at 404 may be received through radio resource control (RRC) signaling. For example, the message at 404 may be an RRC connection reconfiguration message indicating the one or more data radio bearers associated with the one or more network bearer IDs. In certain cases, the RRC connection reconfiguration message may provide a list of data radio bearers to add or modify, where each data radio bearer is associated with a different network bearer ID. That is, the UE may receive, from the second cell, a message reconfiguring the UE to attach to the second cell via data radio bearers, and the message is missing at least one network bearer ID of one or more active network bearers.

In certain aspects, a network bearer ID may be an Evolved Packet System (EPS) bearer ID (e.g., an integer value referred to as eps-BearerIdentity in the RadioResourceConfigDedicated information element) associated with a data radio bearer. For example, the network bearer identities received at 404 may be identities for EPSs.

In certain aspects, the network bearer identity, which is missing from the message at 404, may be associated with a default bearer. In other words, the UE may be configured with a default EPS bearer ID, and the message at 404 may provide a list of data radio bearers, which is missing the default EPS bearer ID.

In aspects, removing the data radio bearer at 406 may involve the UE identifying that a network bearer ID is missing from the RRC connection reconfiguration message and removing the data radio bearer based on the identification. For example, the UE may identify that the at least one network bearer identity associated with the data radio bearer is missing from the message and remove the data radio bearer based on the identification.

In aspects, the active configuration of the data radio bearers may be the configuration of data radio bearers that the UE uses to communicate with the RAN. In other words, before receiving the RRC connection reconfiguration message at 404, the UE may communicate with the RAN via a set of data radio bearers in the active configuration, and the RRC connection reconfiguration message at 404 may provide an update to the active configuration, such as a removal of an EPS bearer ID associated with a certain data radio bearer.

In aspects, the UE may take various actions to prevent a stall in the PS data connectivity after the handover and removal of the data radio bearer. For example, transmitting the tracking area update request at 408 may include the UE transmitting the tracking area update directly after removing the data radio bearer. That is, the UE may transmit the tracking area update request in response to the handover and removal of the data radio bearer. In other words, if the UE determines that a data radio bearer has been removed after a handover, the UE may transmit the tracking area update request based on the determination.

In certain cases, transmitting the tracking area update request at 408 may occur after the removal of the data radio bearer as well as one or more attempts to reestablish PS data connectivity. For example, after the removal of the data radio bearer, the UE may transmit, to the second cell, a request to setup a bearer (e.g., an EPS bearer) to a packet data network (e.g., via a packet data network (PDN) connectivity request) . The UE may send the PDN connectivity request message to initiate establishment of a PDN connection. The UE may run a timer (e.g., the T3482 timer) after transmitting the request to setup the bearer, and if the UE does not receive a response from the network and the timer expires, the UE may transmit the tracking update request at 408. In certain cases, the UE may make multiple attempts to establish PDN connectivity before transmitting the tacking area update request. In other words, the UE may transmit the tracking area update request after a plurality of expirations of the timer.

In aspects, the tracking area update request may be used to update certain UE specific parameters in the network and prevent a stall in the PS data connectivity. In certain cases, the second cell (i.e., the target cell to which the handover is performed) may not support NSA 5G mode, and thus, the PS data connectivity may stall due to the mismatch in support between the UE and second cell. The tracking area update request at 408 may indicate an update regarding a capability of the UE. In certain aspects, the capability of the UE may be that the UE does not support dual-connectivity with a first radio access technology (RAT) and a second RAT. In aspects, the first RAT may be Evolved Universal Terrestrial Radio Access (E-UTRA) (i.e., 4G RAT) , and the second RAT may be Fifth Generation (5G) New Radio (NR) (i.e., 5G RAT) . In other words, the tracking area update request may indicate that the UE does not support dual connectivity with a 4G RAN and a 5G RAN. The tracking area update request may enable the UE to fall back to 4G radio access (among other RATs) without 5G radio access and reestablish PS data connectivity after the handover and removal of the data radio bearer. In certain aspects, the tracking update request may enable the UE to trigger the network to activate a default EPS bearer for the UE as further described herein with respect to the activate default EPS bearer context request message, and thus, prevent a stall in PS data connectivity.

After transmitting the tracking area update request, the UE may receive an acknowledgement from the RAN. For example, the UE may receive, from the second cell, a tracking update accept message that acknowledges the tracking area update request.

After receiving the acknowledgment of the tracking area update request, the UE may request PDN connectivity with the core network (e.g., the EPC) . For example, the operations 400 may include the UE transmitting, to the second cell, a packet data network connectivity request and receiving, from the second cell, a message activating the at least one missing network bearer (e.g., an activate default EPS bearer context request message) in response to the packet data network connectivity request. The activate default EPS bearer context request message may provide a default EPS bearer ID for the UE to activate in the active configuration of data radio bearers. The UE may transmit, to the second cell, an acknowledgement of the activation of the at least one missing network bearer (e.g., an activate default EPS bearer context accept message) . The activate default EPS bearer context accept message may acknowledge the activation of the default EPS bearer.

In certain aspects, the UE may support communicating with a 5G RAN in NSA 5G mode. That is, the UE may be NR capable and support NSA 5G mode. For example, the UE may be configured to communicate with the first and second cells in a NSA 5G mode, for example, as described herein with respect to FIG. 3B. In aspects, the UE may communicate control signaling with the first and second cells via 4G control signaling protocols. For example, the UE may receive the message via control signaling for a 4G RAT (e.g., E-UTRA) , and the UE may transmit, to the second cell, the tracking area update request via the control signaling for the 4G RAT.

FIG. 5 is a signaling flow diagram illustrating example operations 500 for restoring PS data when a bearer is removed, in accordance with certain aspects of the present disclosure. As shown, at 502, the UE 120 may be configured with various data radio bearers having EPS bearer IDs 5, 6, and 7, where the default EPS bearer of the UE has an EPS bearer ID of 5. At 504, the UE 120 may send, to a first cell 110a, a measurement report of neighbor cells, such as the second cell 110b, for handover operations. In aspects, the first cell 110a and second cell 110b may be 4G cells. That is, the the first and

second cells

110a, 110b may communicate via a 4G RAT such as E-UTRA. At 506, the UE 120 may receive, from the first cell 110a, an RRC connection reconfiguration message that indicates to perform a handover to the second cell 110b. For example, the RRC connection reconfiguration message may include various parameters for network controlled mobility, such as a cell identity of the target cell (e.g., the parameter -targetPhysCellId) and a carrier frequency (e.g., the parameter -carrierFreq) for the handover in the mobility control information parameters (e.g., the information element -mobilityControlInfo) . At 508, the UE 120 may perform a handover from the first cell 110a to the second cell 110b based on the RRC connection reconfiguration message at 504.

At 510, the UE 120 may receive, from the second cell 110b, a RRC connection reconfiguration message that provides a list of data radio bearers associated with EPS bearer IDs 6 and 7. In other words, the previously default EPS bearer (e.g., EPS bearer ID 5) may be missing from the RRC connection reconfiguration message. At 512, the UE 120 may identify that the default EPS bearer is missing from the reconfiguration message and remove a data radio bearer associated with the default EPS bearer ID based on the identification of the missing EPS bearer.

In aspects, the UE may take various actions to prevent a stall in the PS data connectivity after the handover and removal of the data radio bearer. For example, as shown in Case 1 at 514, the UE 120 may transmit a tracking area update (TAU) request to the second cell 110b directly after determining that the EPS bearer has been removed. The TAU request may indicate that the UE 120 does not support dual-connectivity with NR, and the TAU request may trigger the RAN to initiate activation of a new default EPS bearer after receiving a PDN connectivity request as further described herein. In aspects, the TAU request may enable the UE to fall back to 4G radio access without 5G radio access.

In other cases (e.g., Case 2) , the UE 120 may attempt to reestablish PDN connectivity before requesting a TAU. For example, at 516, the UE 120 may transmit a PDN connectivity request to the second cell 110b. At 518, the UE 120 may determine that the T3482 timer has expired due to receiving no response from the network, and at 520, the UE 120 may send, to the second cell 110b, the TAU request with the indication of no support for dual-connectivity with NR.

After transmitting the TAU request at 514 or 520, the UE 120 may receive, from the second cell 110b, a TAU accept acknowledging the TAU request at 522. At 524, the UE 120 may transmit a PDN connectivity request to the second cell 110b. At 526, the UE 120 may receive, from the second cell 110b, a message activating the missing EPS bearer (e.g., an activate default EPS bearer context request) . At 528, the UE 120 may transmit, to the second cell 110b, an acknowledgement of the message activating the missing EPS bearer (e.g., an activate default EPS bearer context accept) . At 530, the UE 120 may receive data traffic from the second cell 110b or transmit data traffic to the second cell 110b via the default EPS bearer.

While the example depicted in FIG. 5 is described herein with respect to separate cells to facilitate understanding, aspects of the present disclosure may also be applied to co-located and/or integrated cells. As an example, the first cell 110a and second cell 110b may be co-located and/or integrated in the same base station. For example, the first cell 110a may operate via a certain carrier frequency at a base station, and the second cell 110b may operate at a different carrier frequency at the base station.

FIG. 6 illustrates a wireless communications device 600 (e.g., the UE 120) 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. 4. The communications device 600 includes a processing system 602 coupled to a transceiver 608 (e.g., a transmitter and/or a receiver) . The transceiver 608 is configured to transmit and receive signals for the communications device 600 via an antenna 610, such as the various signals as described herein. The processing system 602 may be configured to perform processing functions for the communications device 600, including processing signals received and/or to be transmitted by the communications device 600.

The processing system 602 includes a processor 604 coupled to a computer-readable medium/memory 612 via a bus 606. In certain aspects, the computer-readable medium/memory 612 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 604, cause the processor 604 to perform the operations illustrated in FIG. 4, or other operations for performing the various techniques discussed herein for restoration of PS data. In certain aspects, computer-readable medium/memory 612 stores code for receiving 614, code for transmitting 616, code for performing 618, and/or code for removing 620. In certain aspects, the processor 604 has circuitry configured to implement the code stored in the computer-readable medium/memory 612. The processor 604 includes circuitry for receiving 624, circuitry for transmitting 626, circuitry for performing 628, and/or circuitry for removing 630.

The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR) , 3GPP Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , 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) , time division synchronous code division multiple access (TD-SCDMA) , 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) . LTE and LTE-Aare releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-Aand 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) . NR is an emerging wireless communications technology under development.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB) , access point (AP) , distributed unit (DU) , carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. 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 an 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.

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 computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC 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. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. 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. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) , and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, 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 communicate directly with one another in addition to communicating with a scheduling entity.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. 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.

As used herein, 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, 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 is to be accorded the full scope consistent with the language of the claims, wherein 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. ” Unless specifically stated otherwise, the term “some” refers to one or more. 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. No claim element is to be construed under the provisions of 35 U.S.C. §112 (f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

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.

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 (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, 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, for example, instructions for performing the operations described herein and illustrated in FIGs. 4 and/or FIG. 5.

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 by a user equipment, comprising:

performing a handover from a first cell to a second cell;

receiving, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers;

removing a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message; and

transmitting, to the second cell, a tracking area update request, which indicates a capability of the UE, after removing the data radio bearer.
The method of claim 1, wherein transmitting the tracking area update request comprises transmitting the tracking area update request directly after removing the data radio bearer.
The method of claim 1, wherein transmitting the tracking area update request comprises:

transmitting, to the second cell, a packet data network connectivity request;

running a timer after transmitting the packet data network connectivity request; and

upon expiration of the timer, transmitting the tracking area update request.
The method of claim 3, wherein transmitting the tracking area update request comprises transmitting the tracking area update request after a plurality of expirations of the timer.
The method of claim 1, further comprising receiving, from the second cell, a tracking area update accept message.
The method of claim 1, further comprising:

transmitting, to the second cell, a packet data network connectivity request;

receiving, from the second cell, a message activating the at least one missing network bearer; and

transmitting, to the second cell, an acknowledgement of the activation of the at least one missing network bearer.
The method of claim 1, wherein the message is received through radio resource control (RRC) signaling.
The method of claim 1, wherein the message is an RRC connection reconfiguration message.
The method of claim 1, wherein the capability of the UE is that UE does not support dual-connectivity with a first radio access technology (RAT) and a second RAT.
The method of claim 9, wherein the first RAT is Evolved Universal Terrestrial Radio Access (E-UTRA) , and the second radio access technology is Fifth Generation (5G) New Radio (NR) .
The method of claim 1, wherein the network bearer identities are identities for an Evolved Packet System (EPS) .
The method of claim 1, wherein removing the data radio bearer comprises:

identifying that the at least one network bearer identity associated with the data radio bearer is missing from the message; and

removing the data radio bearer based on the identification.
The method of claim 12, wherein the network bearer identity is associated with a default bearer.
The method of claim 1, wherein the UE is configured to communicate with the first and second cells in a non-standalone 5G mode.
The method of claim 1, wherein:

receiving the indication comprises receiving the message via control signaling for E-UTRA; and

transmitting, to the second cell, the tracking area update request via the control signaling for E-UTRA.
An apparatus for wireless communication, comprising:

a processing system configured to perform a handover from a first cell to a second cell; and

a transceiver configured to receive, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers,

wherein the processing system is configured to remove a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message, and

wherein the transceiver is configured to transmit, to the second cell, a tracking area update request, which indicates a capability of the apparatus, after removing the data radio bearer.
The apparatus of claim 16, wherein the transceiver is configured to transmit the tracking area update request directly after removing the data radio bearer.
The apparatus of claim 16, wherein:

the transceiver is configured to transmit, to the second cell, a packet data network connectivity request;

the processing system is configured to run a timer after transmitting the packet data network connectivity request; and

the transceiver is configured to transmit, upon expiration of the timer, the tracking area update request.
The apparatus of claim 18, wherein the transceiver is configured to transmit the tracking area update request after a plurality of expirations of the timer.
The apparatus of claim 16, wherein the transceiver is configured to receive, from the second cell, a tracking area update accept message.
The apparatus of claim 16, wherein the transceiver is configured to:

transmit, to the second cell, a packet data network connectivity request;

receive, from the second cell, a message activating the at least one missing network bearer; and

transmit, to the second cell, an acknowledgement of the activation of the at least one missing network bearer.
The apparatus of claim 16, wherein the message is received through radio resource control (RRC) signaling.
The apparatus of claim 16, wherein the message is an RRC connection reconfiguration message.
The apparatus of claim 16, wherein the capability of the apparatus is that the apparatus does not support dual-connectivity with a first radio access technology (RAT) and a second RAT.
The apparatus of claim 24, wherein the first RAT is Evolved Universal Terrestrial Radio Access (E-UTRA) , and the second radio access technology is Fifth Generation (5G) New Radio (NR) .
The apparatus of claim 16, wherein the network bearer identities are identities for an Evolved Packet System (EPS) .
The apparatus of claim 16, wherein the processing system is configured to:

identify that the at least one network bearer identity associated with the data radio bearer is missing from the message; and

remove the data radio bearer based on the identification.
The apparatus of claim 27, wherein the network bearer identity is associated with a default bearer.
The apparatus of claim 16, wherein the apparatus is configured to communicate with the first and second cells in a non-standalone 5G mode.
The apparatus of claim 16, wherein:

the transceiver is configured to receive the indication comprises receiving the message via control signaling for E-UTRA; and

the transceiver is configured to transmit, to the second cell, the tracking area update request via the control signaling for E-UTRA.
An apparatus for wireless communication, comprising:

means for performing a handover from a first cell to a second cell;

means for receiving, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers;

means for removing a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message; and

means for transmitting, to the second cell, a tracking area update request, which indicates a capability of the apparatus, after removing the data radio bearer.
A computer readable medium having instructions stored thereon for:

performing a handover from a first cell to a second cell;

receiving, from the second cell, a message to reconfigure one or more data radio bearers associated with one or more network bearer identities, wherein the one or more network bearer identities are missing at least one network bearer identity from an active configuration of the one or more data radio bearers;

removing a data radio bearer, associated with the at least one missing network bearer identity, from the active configuration of the one or more data radio bearers based on the message; and

transmitting, to the second cell, a tracking area update request, which indicates a capability of a user equipment, after removing the data radio bearer.