WO2021203229A1

WO2021203229A1 - Preventing service loss in non-standalone mode of a shared cell

Info

Publication number: WO2021203229A1
Application number: PCT/CN2020/083444
Authority: WO
Inventors: Hao Zhang; Xiuqiu XIA; Tianya LIN
Original assignee: Qualcomm Incorporated
Priority date: 2020-04-07
Filing date: 2020-04-07
Publication date: 2021-10-14

Abstract

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may assign priorities to a stored list of candidate cells used for cell selection processes. The UE may determine a priority for each cell based on the number of public land mobile network identifiers (PLMN IDs) that are associated with each candidate cell, and based on whether a PLMN ID is requested by the non-access stratum (NAS). The UE may receive a NAS request identifying a first PLMN, and a PLMN list from each candidate cell that indicates PLMNs supported by the candidate cell. The UE may prioritize each candidate cell based on the number of PLMNs reported by the candidate cells, and by whether the first PLMN occupies a first entry in the PLMN list for the candidate cell. The UE may then perform a connection procedure with a candidate cell based on the determined priority.

Description

PREVENTING SERVICE LOSS IN NON-STANDALONE MODE OF A SHARED CELL

TECHNICAL FIELD

The following relates generally to wireless communications and more specifically to preventing service loss in non-standalone mode of a shared cell.

BACKGROUND

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) . A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

In some wireless communications systems, the network may not respond to an attach request or a tracking area update (TAU) request sent from a UE that is attempting to establish a network connection (e.g., a 5G or NR connection) . In some examples, after a number of failed connection attempts or upon expiration of a timer, the UE may release its radio resource control (RRC) connection and may camp on the next available PLMN, which is often has lesser or outdated service quality.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support preventing service loss in non-standalone mode of a shared cell. Generally, the described techniques provide for a device such as UE that may establish a network connection (e.g., a 5G NR connection) through a shared cell, where the cell is associated with multiple different public land mobile networks (PLMNs) served by a base station. A UE operating in a non-standalone mode of 5G may simultaneously connect to an LTE cell and one or more 5G cells. The LTE cell may provide control plane functionality for the one or more 5G cells. In some examples, however, when a UE is operating in non-standalone mode, network issues may result in the LTE cell becoming non-responsive to attach requests or tracking area update (TAU) update requests by the UE, causing an RRC connection to time out and release after a number of unsuccessful connection attempts. This behavior has been noticed especially in shared cells for which an NAS requested PLMN for the UE is not the first PLMN advertised by the shared cell.

To reduce service loss and increase service reliability, the UE may assign priorities to candidate cells within range of the UE for cell selection and re-selection at the RRC layer. For example, the UE may prioritize candidate cells based on the number of PLMN IDs that are associated with each candidate cell, and in some cases, based on whether a PLMN ID is requested by the non-access stratum (NAS) is a first entry in a PLMN list advertised by that candidate cell. For example, the UE may prioritize the candidate cells by assigning a highest priority to any candidate cell advertising support for only one PLMN ID corresponding to a NAS requested PLMN. The UE may assign a next highest priority to any candidate cells advertising support for multiple PLMN IDs, but for which the PLMN ID corresponding to the NAS requested PLMN occupies a first or top entry in the PLMN list advertised by the candidate cell. A lowest priority may be assigned to any candidate cell advertising support for the PLMN ID corresponding to the NAS requested PLMN, but at a second or later entry in the PLMN list advertised by the candidate cell. The UE may then perform a camping or connection procedure with a candidate cell based on the determined priority.

A method of wireless communications is described. The method may include receiving a non-access stratum request identifying a first public land mobile network (PLMN) , receiving, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritizing each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and performing a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

An apparatus for wireless communications is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a non-access stratum request identifying a first public land mobile network (PLMN) , receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

Another apparatus for wireless communications is described. The apparatus may include means for receiving a non-access stratum request identifying a first public land mobile network (PLMN) , receiving, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritizing each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and performing a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to receive a non-access stratum request identifying a first public land mobile network (PLMN) , receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the PLMN list from each candidate cell may include operations, features, means, or instructions for receiving a system information block from each candidate cell, the system information block including the PLMN list for that candidate cell.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, prioritizing each candidate cell in the set of candidate cells may include operations, features, means, or instructions for assigning a first priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry may be the only entry in the PLMN list for that candidate cell.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, prioritizing each candidate cell in the set of candidate cells further may include operations, features, means, or instructions for assigning a second priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry may be one of a set of entries in the PLMN list for that candidate cell. The second priority may be lower than the first priority.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, prioritizing each candidate cell in the set of candidate cells further may include operations, features, means, or instructions for assigning a third priority to any one candidate cell of the set of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell. The third priority may be lower than the first priority and the second priority.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the camping procedure or the connection procedure for the first candidate cell may include operations, features, means, or instructions for selecting the first candidate cell for the camping procedure or the connection procedure based on a determination that the first candidate cell may have a highest priority of the set of candidate cells according to the prioritizing.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, selecting the first candidate cell may be further based on a signal strength of the first candidate cell.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, performing the camping procedure or the connection procedure for the first candidate cell may include operations, features, means, or instructions for transmitting an attach request or a tracking area update request to the first candidate cell, and receiving an attach accept message or a tracking area update accept message from the first candidate cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communications that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications network that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow chart that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of a process flow chart that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIGs. 5 and 6 show block diagrams of devices that support preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIG. 7 shows a block diagram of a communications manager that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIG. 8 shows a diagram of a system including a device that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

FIGs. 9 through 13 show flowcharts illustrating methods that support preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some wireless communications networks, a device such as a user equipment (UE) may operate in a non-standalone (NSA) mode of 5G, and may simultaneously connect to an LTE cell and one or more 5G cells. The UE may establish a network connection (e.g., a 5G NR connection) through a shared cell, where the cell is associated with multiple different public land mobile networks (PLMNs) and served by a base station. The network may use NAS control protocols based on the Radio Resource Control (RRC) state of the (e.g., whether the UE is in a RRC_IDLE or RRC_CONNECTED state) to establish a connection of the UE to a serving cell. In some examples, however, when the UE is operating in an NSA mode, network issues may result in the LTE cell becoming non-responsive to attach requests or tracking area update (TAU) update requests by the UE. As a result, the RRC connection may time out and release after a number of unsuccessful connection attempts, causing the UE to camp on a next available PLMN (e.g., a 2G or 3G PLMN associated with the same PLMN ID) . This behavior has been noticed especially in shared cells for which a NAS requested PLMN for the UE is not the first PLMN advertised by the shared cell.

To reduce service loss and improve service reliability, the UE may assign priorities to candidate cells and within the range of the UE. According to the prioritization, the UE may avoid camping on a cell that may not accept to the TAU request or attach request. The UE may store a list of candidate cells for cell selection and re-selection at the RRC layer. The UE may prioritize candidate cells within the cell list based on the number of PLMN IDs that are associated with each candidate cell, and in some cases based on whether a PLMN ID is requested by the NAS and is a first or top entry in a PLMN list advertised by that candidate cell. For example, the UE may prioritize the candidate cells in the cell list by giving a shared cells a lower priority. Specifically, a highest priority may be given to a cell with only one PLMN ID corresponding to a NAS requested PLMN in PLMN list of a first system information block (SIB1) . The UE may assign a next highest priority to cells supporting multiple PLMN IDs in SIB1 with the NAS-requested PLMN ID of the UE occupying the first or top entry in the PLMN ID list. A lowest priority is assigned to any candidate cell advertising support for multiple PLMN IDs, but for which the PLMN ID corresponding to the NAS requested PLMN occupies a second or later entry in the PLMN list. Prioritizing the cell list may allow the UE to maintain a cell connection (e.g., LTE) to the selected cell to obtain or maintain NSA mode (e.g., 5G NR) service.

According to the priority given to the candidate cells, the UE may avoid camping on shared cells. In cases that the UE does camp on the shared cell, however, it may prioritize cells where the first PLMN ID in the PLMN ID list is NAS requested. The UE may assign lower priority to cells where the first PLMN ID in the PLMN ID list is not NAS requested. In addition the NAS may select a cell based on various metrics such as the signal strength or signal quality. The UE may perform a camping or connection procedure with a candidate cell based on the determined priority.

Aspects of the disclosure are initially described in the context of wireless communications systems. For example, aspects of the disclosure are described in the context of signaling between a UE, base station, and other higher layer signaling entities. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to preventing service loss in non-standalone mode of a shared cell.

FIG. 1 illustrates an example of a wireless communications system 100 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more base stations 105, one or more 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, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

The base stations 105 may be dispersed throughout a geographic area to form the wireless communications system 100 and may be devices in different forms or having different capabilities. The base stations 105 and the UEs 115 may wirelessly communicate via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which the UEs 115 and the base station 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area over which a base station 105 and a UE 115 may support the communication of signals according to one or more radio access technologies.

The UEs 115 may be dispersed throughout a coverage area 110 of the wireless communications system 100, and each UE 115 may be stationary, or mobile, or both at different times. The UEs 115 may be devices in different forms or having different capabilities. Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115, the base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment) , as shown in FIG. 1.

The base stations 105 may communicate with the core network 130, or with one another, or both. For example, the base stations 105 may interface with the core network 130 through one or more backhaul links 120 (e.g., via an S1, N2, N3, or other interface) . The base stations 105 may communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) , or indirectly (e.g., via core network 130) , or both. In some examples, the backhaul links 120 may be or include one or more wireless links.

One or more of the base stations 105 described herein may include or may be referred to by a person having ordinary skill 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 NodeB or a giga-NodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or other suitable terminology.

A UE 115 may include or may 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, among other examples. A UE 115 may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a multimedia/entertainment device (e.g., a radio, a MP3 player, a video device, etc. ) , a camera, a gaming device, a navigation/positioning device (e.g., GNSS (global navigation satellite system) devices based on, for example, GPS (global positioning system) , Beidou, GLONASS, or Galileo, a terrestrial-based device, etc. ) , a tablet computer, a laptop computer or a personal computer, a netbook, a smartbook, a personal computer, a smart device, a wearable device (e.g., a smart watch, smart clothing, smart glasses, virtual reality goggles, a smart wristband, smart jewelry (e.g., a smart ring, a smart bracelet) ) , a drone, a robot/robotic device, a vehicle, a vehicular device, a meter (e.g., parking meter, electric meter, gas meter, water meter) , a monitor, a gas pump, an appliance (e.g., kitchen appliance, washing machine, dryer) , a location tag, a medical/healthcare device, an implant, a sensor/actuator, a display, or any other suitable device configured to communicate via a wireless or wired medium. In some examples, a UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples.

The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115 that may sometimes act as relays as well as the base stations 105 and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in FIG. 1.

The UEs 115 and the base stations 105 may wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links 125. For example, a carrier used for a communication link 125 may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP) ) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR) . Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information) , control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system 100 may support communication with a UE 115 using carrier aggregation or multi-carrier operation. A UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers.

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. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN) ) and may be positioned according to a channel raster for discovery by the UEs 115. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs 115 via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology) .

The communication links 125 shown in the 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. Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode) .

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 determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz) ) . Devices of the wireless communications system 100 (e.g., the base stations 105, the UEs 115, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 or UEs 115 that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM) ) . In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams) , and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE 115.

One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for the UE 115 may be restricted to one or more active BWPs.

The time intervals for the base stations 105 or the UEs 115 may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T _s=1/ (Δf _max·N _f) seconds, where Δf _max may represent the maximum supported subcarrier spacing, and N _f may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms) ) . Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023) .

Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . In some wireless communications systems 100, a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N _f) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation.

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI) . In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) ) .

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 one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET) ) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs 115. For example, one or more of the UEs 115 may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs) ) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets for sending control information to a specific UE 115.

Each base station 105 may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer 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) , or others) . In some examples, a cell may also refer to a geographic coverage area 110 or a portion of a geographic coverage area 110 (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station 105. For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas 110, among other examples.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs 115 with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs 115 with service subscriptions with the network provider or may provide restricted access to the UEs 115 having an association with the small cell (e.g., the UEs 115 in a closed subscriber group (CSG) , the UEs 115 associated with users in a home or office) . A base station 105 may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers.

In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT) , enhanced mobile broadband (eMBB) ) that may provide access for different types of devices.

In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, the overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous network in which different types of the base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

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

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 such information to a central server or application program that makes use of the information or presents the information to humans interacting with the application program. Some UEs 115 may be designed to collect information or enable automated behavior of machines or other devices. 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. In an aspect, techniques disclosed herein may be applicable to MTC or IoT UEs. MTC or IoT UEs may include MTC/enhanced MTC (eMTC, also referred to as CAT-M, Cat M1) UEs, NB-IoT (also referred to as CAT NB1) UEs, as well as other types of UEs. eMTC and NB-IoT may refer to future technologies that may evolve from or may be based on these technologies. For example, eMTC may include FeMTC (further eMTC) , eFeMTC (enhanced further eMTC) , mMTC (massive MTC) , etc., and NB-IoT may include eNB-IoT (enhanced NB-IoT) , FeNB-IoT (further enhanced NB-IoT) , etc.

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 the UEs 115 include entering a power saving deep sleep mode when not engaging in active communications, operating over a limited bandwidth (e.g., according to narrowband communications) , or a combination of these techniques. For example, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a defined portion or range (e.g., set of subcarriers or resource blocks (RBs) ) within a carrier, within a guard-band of a carrier, or outside of a carrier.

The wireless communications system 100 may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs 115 may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions) . Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT) , mission critical video (MCVideo) , or mission critical data (MCData) . Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein.

In some examples, a UE 115 may also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol) . One or more UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of the 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 examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs 115 without the involvement of a base station 105.

In some systems, the D2D communication link 135 may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115) . In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or with both.

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) or 5G core (5GC) , which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME) , an access and mobility management function (AMF) ) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW) , a Packet Data Network (PDN) gateway (P-GW) , or a user plane function (UPF) ) . The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs 115 served by the base stations 105 associated with the core network 130. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services 150. The operators IP services 150 may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched Streaming Service.

Some of the network devices, such as a base station 105, may include subcomponents such as an access network entity 140, which may be an example of an access node controller (ANC) . Each access network entity 140 may communicate with the UEs 115 through one or more other access network transmission entities 145, which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs) . Each access network transmission entity 145 may include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105) .

The wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz) . Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs 115 located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) 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.

The 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, or 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, the wireless communications system 100 may support millimeter wave (mmW) communications between the UEs 115 and the base stations 105, and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The 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.

The wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations 105 and the UEs 115 may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

A base station 105 or a UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays or antenna panels, which may support MIMO operations 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 examples, 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. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

The base stations 105 or the UEs 115 may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords) . Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) , where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) , where multiple spatial layers are transmitted to multiple devices.

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, a UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path 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 some 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 amplitude offsets, phase offsets, or both to signals carried via 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) .

A base station 105 or a UE 115 may use beam sweeping techniques as part of beam forming operations. For example, a base station 105 may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions. For example, the base station 105 may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station 105, or by a receiving device, such as a UE 115) a beam direction for later transmission or reception by the base station 105.

Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions and may report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality or an otherwise acceptable signal quality.

In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station 105 to a UE 115) . The UE 115 may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station 105 may transmit a reference signal (e.g., a cell-specific reference signal (CRS) , a channel state information reference signal (CSI-RS) ) , which may be precoded or unprecoded. The UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook) . Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection 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 (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal) . The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR) , or otherwise acceptable signal quality based on listening according to multiple beam directions) .

The 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 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 error detection techniques, error correction techniques, or both to support retransmissions 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 a core network 130 supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels.

The UEs 115 and the base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for 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., low signal-to-noise conditions) . In some examples, a 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.

In some wireless communications networks, a device such as UE 115 may establish a network connection (e.g., a 5G NR connection) through a shared cell, where the cell is associated with multiple different public land mobile networks (PLMNs) and served by a base station 105. In some examples, however, the network may not respond to an attach request or tracking area update (TAU) update request, and the UE 115 may release an RRC connection after a number of unsuccessful connection attempts or after a defined number of counts, and may camp on a next available PLMN (e.g., a 2G or 3G PLMN associated with the same PLMN ID) .

To reduce service loss due to unsuccessful connection attempts, the UE 115 may monitor system information broadcasts by candidate cells to retrieve PLMN lists advertised by the respective candidate cells, and prioritize the candidate cells for cell selection and re-selection based on whether an NAS requested or preferred PLMN occupies a top or first position in the respective PLMN list and if the NAS requested or preferred PLMN occupies an only position in the respective PLMN list. Specifically, the UE 115 may assign a highest priority to a cell with only one PLMN ID in PLMN list of a first system information block (SIB1) if that PLMN ID corresponds to the NAS requested or preferred PLMN. The UE 115 may assign a next highest priority to cells having multiple PLMN IDs advertised in SIB1 with the NAS-requested PLMN ID of the UE 115 occupying the first entry in the PLMN ID list. A lowest priority is assigned to cells having multiple PLMN IDs in the PLMN list, and for which the NAS-requested PLMN ID is not the first entry in the PLMN ID list. The UE 115 may then perform a camping or connection procedure with a candidate cell based on the determined priority.

FIG. 2 illustrates an example of a wireless communications system 200 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. In some examples, wireless communications system 200 may implement aspects of wireless communications system 100. For example, wireless communications system 200 may implement signaling between higher layer entities and devices such as a base station 105-a and a UE 115-a, which may be examples of base stations 105 and UEs 115 described with reference to FIG. 1.

A wireless communications system 200 may implement a number of cell selection and reselection procedures to increase network efficiency and improve overall service for devices within the network. In some examples, the network may use non-access stratum (NAS) control protocols for PLMN selection, tracking area update (TAU) signaling, paging, authentication and Evolved Packet System (EPS) bearer establishment, modification, and release. Some such NAS control protocols may be based on the Radio Resource Control (RRC) state of the UE 115-a (e.g., whether the UE 115-a is in a RRC_IDLE or RRC_CONNECTED state) which may indicate a connection of the UE 115-a to a serving cell (e.g., cells 210-a, 210-b, or 210-c) .

In some examples, UE 115-a while in RRC_IDLE may perform cell selection (or reselection) , and the UE 115-a may determine a cell in which to camp. In some cases, UE 115-a may receive system information from one or more candidate cells. The UE may receive the information in one or more system information blocks (SIBs) 205, which may contain cell selection parameters such as a list of PLMNs associated with each of the one or more candidate cells. In some cases, the NAS may select or request a cell based at least in part on a priority of the cell, the priority based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. In addition the NAS may select a cell based on various metrics such as the signal strength or signal quality. The UE 115-a may perform a camping or connection procedure with a candidate cell based on the priority.

In some examples, the UE 115-a may lose service (for example, LTE service) when camping on a cell that is associated with two or more different PLMNs (e.g., a shared cell 210-b) . In such cases, the UE 115-a may not support NR5G service based on the camping failure (e.g., TAU request or attach request failure) in LTE, and the UE 115-a may fall back to legacy service (e.g., 2G, 3G) for the shared cell. For example, the UE 115-a may be associated with a first PLMN (e.g., the UE 115-a may have hardware associated with the first PLMN) and may reject service associated with a second PLMN provided or prioritized by the shared cell. In addition, network issues may result in the LTE cell becoming non-responsive to attach requests of TAU update requests by the UE 115-a, causing an RRC connection to time out and release.

In some other cases, the UE 115-a may select a PLMN ID that is not on top of a PLMN Identity list (e.g., the PLMN ID that is NAS requested may not be on the top of the PLMN identity list) , and the network may release RRC connection (e.g., without TAU/ACCEPT or ATTACH ACCEPT) . In such cases, the UE 115-a may reject TAU/ATTACH and may lose LTE service in addition to NSA or 5G service (which may use LTE as an anchoring service) . The UE 115-a may repeat or loop an attachment procedure (e.g., TAU or ATTACH) until the number of attempts satisfies a threshold number of counts. In cases where the attachment procedure is unsuccessful for a threshold number of counts, NAS will try to camp on or establish an RRC connection with the next available PLMN (e.g., a 2/3G PLMN with the same PLMN ID) .

To reduce service loss and improve cell selection, the candidate cells in the cell list may be prioritized according to various factors. According to the prioritization, the UE 115-a may avoid camping on a cell that may not accept a TAU or attach request (e.g., such as shared cells) . In addition, prioritizing the cell list may also allow the UE to maintain a cell connection (e.g., LTE) to the selected cell to obtain NSA service.

The UE 115-a may store a list of candidate cells (e.g., cells 210-a. 210-b, 210-c) for cell selection and re-selection in the RRC. The UE 115-a may determine a priority for cell selection based on the number of PLMN IDs that are associated with each candidate cell, and in some cases based on whether a PLMN ID is requested by the NAS. For example, UE 115- a may prioritize the candidate cells in the cell list by giving shared cells a lower priority. A highest priority may be given to a cell with only one PLMN ID in plmn-IdentityList of a first system information block (SIB1) . A second priority may be assigned to a candidate cell containing more than one PLMN ID located in a plmn-IdentityList of the SIB1, were a first PLMN ID is NAS requested. In some other cases, a third priority may be assigned to a candidate cell containing more than one PLMN ID located in a plmn-IdentityList of the SIB1, were a first PLMN ID of the more than one PLMN IDs is not NAS requested. In such cases, the first priority may be a higher priority than both the second and third priorities, and the second priority is higher than the third priority.

According to the priority assigned to the candidate cells, the UE 115-a may avoid camping on shared cells. In cases that the UE does camp on the shared cell, however, it may prioritize cells where the first PLMN ID in the PLMN ID list is NAS requested. The UE 115-a may assign lower priority to cells where the first PLMN ID in the PLMN ID list is not NAS requested.

In some implementations, the UE 115-a may perform the prioritization of the candidate cells before TAU or attach procedure. For example, the NAS may request a PLMN ID to RRC. RRC may evaluate the cell and selects a camping cell to which RRC reports the cell ID and the PLMN ID to the NAS. Later, NAS requests a TAU or attach procedure based on the priority.

FIG. 3 illustrates an example of a process flow chart 300 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. In some examples, process flow chart 300 may implement aspects of wireless communications system 100. For example, the wireless communications system 100 may implement signaling according to process flow chart 300 between higher layer entities and devices such as a base station and a UE, which may be examples of base stations 105 and UEs 115 described with reference to FIGs. 1 and 2.

In process flow chart 300, the UE may support a number of different service types (e.g., 2G, 3G, 4G, 5G, etc. ) and may operate using NSA mode. At 305, the NAS may identify a first PLMN and may transmit a service request (e.g., SERVICE_REQ (PLMN 1) ) to the RRC.

At 310, the RRC (UE) may identify a number of candidate cells associated with the first PLMN for an RRC connection (e.g., cell_1, cell_2, and cell_3) , and may determine associated signal strengths for the identified cells, and may rank the cells based on signal strength or radio link quality. For example, the UE may identify cell_1 as having the strongest signal power, cell_2 having a next strongest signal power, and cell 3 as having the weakest signal power of the identified cells. The RRC (UE) may in some examples assign highest priority to the first cell (e.g., cell_1)

At 315, the RC (UE) may notify the NAS of the prioritization of the cells, and may transmit a service indication identifying cell_1 (e.g., SERVICE_IND (Cell_1) ) .

Procedure 320 displays a RRC connection and establishment procedure associated with a TAU or attach request, which in some cases may prompt the UE to perform a contention-based random access procedure or another connection establishment process. At 325, the NAS (UE) may transmit an RRC connection establishment request to the RRC which may include a TAU or attach request (e.g., RRC CONN_EST_REQ ATTACH_REQ or TRACKING_AREA_UPDATE_REQ) . At 330 the RRC may transmit an RRC connection request to the first cell (e.g., CELL 1) . At 335, if the cell accepts the connection, it may transmit a RRCConnectionSetup message to the RRC (UE) . The UE returns the RRCConnectionSetupComplete message at 340, and includes the NAS message and identifier of the selected PLMN. At 345, the cell may release the connection with the RRC (UE) and may transmit an RRCConnectionRelease message. At 350, the RRC (UE) may notify the NAS (UE) of the released connection (e.g., transmitting RRC_CONN_REL message) .

In some cases, the network may release RRC connection (e.g., without TAU/ACCEPT or ATTACH ACCEPT) . In such cases, the UE may reject the TAU or ATTACH request and may lose service. The UE may repeat or loop an attachment procedure at 355 (e.g., TAU or ATTACH) until the number of attempts satisfies a threshold number of counts. In cases where the attachment procedure is unsuccessful for a threshold number of counts or at the expiration of a timer, NAS will try to camp or establish an RRC connection on the next available PLMN at 360 (e.g., a legacy service with the same PLMN ID) before ending the connection procedure at 365.

FIG. 4 illustrates an example of a process flow chart 400 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. In some examples, process flow chart 400 may implement aspects of wireless communications system 100. For example, wireless communications system 200 may implement signaling between higher layer entities and devices such as a base station and a UE, which may be examples of base stations 105 and UEs 115 described with reference to FIGs. 1–3.

In the example process flow chart in FIG. 4, the network may reduce service loss and improve cell selection by prioritizing different candidate cells in the cell list in RRC according to various factors. The prioritization may allow the UE to maintain a cell connection (e.g., LTE) to the selected cell to obtain NSA service. The UE may determine a priority for cell selection based on the number of PLMN IDs that are associated with each candidate cell, and in some cases based on whether a PLMN ID is requested by the NAS. For example, a UE may prioritize the cell list by giving a shared cell a lower priority.

In some implementations, the UE may be configured to support different radio access technologies (RATs) (e.g., LTE, NR) , and may support NSA mode communications. The NAS (UE) may be associated with a first PLMN (e.g., PLMN1) and at 405 may transmit a service request (e.g., SERVICE_REQ (PLMN 1) ) to the RRC (UE) . The RRC (UE) may receive the NAS request that identifies the first PLMN. The RRC (UE) may identify a number of candidate cells (e.g., cell_1, cell_2, cell_3) and may receive, from each candidate cell in the number of candidate cells, a PLMN list indicating one or more PLMNs supported by each respective candidate cell. For example, the RRC (UE) may receive a SIB from each candidate cell containing the PLMN list for each of the candidate cells. In addition, the RRC (UE) may determine a signal power or radio link quality associated with each of the candidate cells. For example, the RRC (UE) may determine that cell_1 power is strongest, and that PLMN1 and PLMN2 are in the plmn-IdentityList of SIB1. In addition, the RRC (UE) may determine that the cell_2 power is lower than cell_1, but higher than cell_3, and that PLMN1 and PLMN2 are in plmn-IdentityList of SIB1, and that PLMN1 is first in the plmn-IdentityList. Further, the RRC (UE) may determine that the cell-3 power is lower than cell_2, and that PLMN1 is the only PLMN in the plmn-IdentityList of SIB1.

At 410, the RRC (UE) may prioritize each candidate cell of the list of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell.

For assigning priorities, the RRC (UE) may assign a first priority to any one candidate cell of the number of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell. For example, the RRC UE may assign the first priority to cell_3.

The RRC (UE) may further assign a second priority to any one candidate cell of the number of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a number of entries in the PLMN list for that candidate cell, wherein the second priority is lower than the first priority. For example, the RRC (UE) may assign the second priority to cell_2.

In addition, the RRC (UE) may assign a third priority to any one candidate cell of the number of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, wherein the third priority is lower than the first priority and the second priority. For example, the RRC (UE) may assign the third priority to cell_1.

At 415, the RRC (UE) may notify the NAS (UE) of the priorities given to the number of candidate cells. For example, the RRC (UE) may use a service indicator (SERVICE_IND) that indicates cell_3 as having the first priority.

At 420, the NAS (UE) may begin to perform a camping procedure or a connection procedure for a candidate cell in the number of candidate cells based on the prioritizing. For example, the NAS (UE) may select the first candidate cell (e.g., cell_3) for the camping procedure or the connection procedure based on determining that the first candidate cell has a highest priority of the number of candidate cells according to the prioritizing. The NAS (UE) may transmit an attach request or a tracking area update request to the first candidate cell. For example, the NAS (UE) may transmit a RRC CONN_EST_REQ (ATTACH_REQ/TRACKING_AREA_UPDATE_REQ) message to cell_3.

At 425, the NAS (UE) may receive an attach accept message or a TAU accept message from the first candidate cell (e.g., cell_3) . At 430, the NAS (UE) may end the RRC connection procedure.

FIG. 5 shows a block diagram 500 of a device 505 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The device 505 may be an example of aspects of a UE 115 as described herein. The device 505 may include a receiver 510, a communications manager 515, and a transmitter 520. The device 505 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to preventing service loss in non-standalone mode of a shared cell, etc. ) . Information may be passed on to other components of the device 505. The receiver 510 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The receiver 510 may utilize a single antenna or a set of antennas.

The communications manager 515 may receive a non-access stratum request identifying a first public land mobile network (PLMN) , receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The communications manager 515 may be an example of aspects of the communications manager 810 described herein.

The communications manager 515, or its sub-components, may be implemented in hardware, software (e.g., executed by a processor) , or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 515, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC) , a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The communications manager 515, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 515, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 515, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The transmitter 520 may transmit signals generated by other components of the device 505. In some examples, the transmitter 520 may be collocated with a receiver 510 in a transceiver module. For example, the transmitter 520 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 520 may utilize a single antenna or a set of antennas.

In some examples, communications manager 515 may be implemented as an integrated circuit or chipset for a mobile device modem, and the receiver 510 and transmitter 520 may be implemented as analog components (e.g., amplifiers, filters, antennas, etc. ) coupled with the mobile device modem to enable wireless transmission and reception.

The communications manager 515 as described herein may be implemented to realize one or more potential advantages. Various implementations may enable increased communications quality and signaling strength between a UE and a selected cell. In addition, at least one implementation may reduce the number of times a UE may lose service due to shared cell connections.

Based on implementing the prioritization techniques as described herein, one or more processors of the device 505 (e.g., processor (s) controlling or incorporated with one or more of receiver 510, communications manager 515, and transmitter 520) may reduce the number of times a device 505 may attempt to connect or reconnect to a network. In addition, the prioritization may reduce power usage and improve communications quality between devices in the network.

FIG. 6 shows a block diagram 600 of a device 605 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The device 605 may be an example of aspects of a device 505, or a UE 115 as described herein. The device 605 may include a receiver 610, a communications manager 615, and a transmitter 640. The device 605 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 610 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to preventing service loss in non-standalone mode of a shared cell, etc. ) . Information may be passed on to other components of the device 605. The receiver 610 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The receiver 610 may utilize a single antenna or a set of antennas.

The communications manager 615 may be an example of aspects of the communications manager 515 as described herein. The communications manager 615 may include a PLMN identifier 620, a PLMN list module 625, a prioritization component 630, and a connection establishment component 635. The communications manager 615 may be an example of aspects of the communications manager 810 described herein.

The PLMN identifier 620 may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The PLMN list module 625 may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The prioritization component 630 may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell.

The connection establishment component 635 may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

The transmitter 640 may transmit signals generated by other components of the device 605. In some examples, the transmitter 640 may be collocated with a receiver 610 in a transceiver module. For example, the transmitter 640 may be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 640 may utilize a single antenna or a set of antennas.

FIG. 7 shows a block diagram 700 of a communications manager 705 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The communications manager 705 may be an example of aspects of a communications manager 515, a communications manager 615, or a communications manager 810 described herein. The communications manager 705 may include a PLMN identifier 710, a PLMN list module 715, a prioritization component 720, a connection establishment component 725, a SIB receiver 730, a cell selection component 735, and a TAU attach component 740. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The PLMN identifier 710 may receive a non-access stratum request identifying a first public land mobile network (PLMN) .

The PLMN list module 715 may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The SIB receiver 730 may receive a system information block from each candidate cell, the system information block including the PLMN list for that candidate cell.

The prioritization component 720 may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell.

In some examples, the prioritization component 720 may assign a first priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell.

In some examples, the prioritization component 720 may assign a second priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a set of entries in the PLMN list for that candidate cell, where the second priority is lower than the first priority.

In some examples, the prioritization component 720 may assign a third priority to any one candidate cell of the set of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, where the third priority is lower than the first priority and the second priority.

The cell selection component 735 may select the first candidate cell for the camping procedure or the connection procedure based on a determination that the first candidate cell has a highest priority of the set of candidate cells according to the prioritizing. In some examples, the cell selection component 735 may select the first candidate cell is further based on a signal strength of the first candidate cell.

The TAU attach component 740 may transmit an attach request or a tracking area update request to the first candidate cell. In some examples, the TAU attach component 740 may receive an attach accept message or a tracking area update accept message from the first candidate cell.

The connection establishment component 725 may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

FIG. 8 shows a diagram of a system 800 including a device 805 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The device 805 may be an example of or include the components of device 505, device 605, or a UE 115 as described herein. The device 805 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 810, an I/O controller 815, a transceiver 820, an antenna 825, memory 830, and a processor 840. These components may be in electronic communication via one or more buses (e.g., bus 845) .

The communications manager 810 may receive a non-access stratum request identifying a first public land mobile network (PLMN) , receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell, prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell, and perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing.

The I/O controller 815 may manage input and output signals for the device 805. The I/O controller 815 may also manage peripherals not integrated into the device 805. In some cases, the I/O controller 815 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 815 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 815 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 815 may be implemented as part of a processor. In some cases, a user may interact with the device 805 via the I/O controller 815 or via hardware components controlled by the I/O controller 815.

The transceiver 820 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 820 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 820 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 825. However, in some cases the device may have more than one antenna 825, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 830 may include RAM and ROM. The memory 830 may store computer-readable, computer-executable code 835 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 830 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 840 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a 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, the processor 840 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 840. The processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks supporting preventing service loss in non-standalone mode of a shared cell) .

The code 835 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 835 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 835 may not be directly executable by the processor 840 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 9 shows a flowchart illustrating a method 900 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The operations of method 900 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 900 may be performed by a communications manager as described with reference to FIGs. 5 through 8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 905, the UE may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The operations of 905 may be performed according to the methods described herein. In some examples, aspects of the operations of 905 may be performed by a PLMN identifier as described with reference to FIGs. 5 through 8.

At 910, the UE may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The operations of 910 may be performed according to the methods described herein. In some examples, aspects of the operations of 910 may be performed by a PLMN list module as described with reference to FIGs. 5 through 8.

At 915, the UE may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. The operations of 915 may be performed according to the methods described herein. In some examples, aspects of the operations of 915 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 920, the UE may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The operations of 920 may be performed according to the methods described herein. In some examples, aspects of the operations of 920 may be performed by a connection establishment component as described with reference to FIGs. 5 through 8.

FIG. 10 shows a flowchart illustrating a method 1000 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The operations of method 1000 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1000 may be performed by a communications manager as described with reference to FIGs. 5 through 8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1005, the UE may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The operations of 1005 may be performed according to the methods described herein. In some examples, aspects of the operations of 1005 may be performed by a PLMN identifier as described with reference to FIGs. 5 through 8.

At 1010, the UE may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The operations of 1010 may be performed according to the methods described herein. In some examples, aspects of the operations of 1010 may be performed by a PLMN list module as described with reference to FIGs. 5 through 8.

At 1015, the UE may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. The operations of 1015 may be performed according to the methods described herein. In some examples, aspects of the operations of 1015 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1020, the UE may assign a first priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell. The operations of 1020 may be performed according to the methods described herein. In some examples, aspects of the operations of 1020 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1025, the UE may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The operations of 1025 may be performed according to the methods described herein. In some examples, aspects of the operations of 1025 may be performed by a connection establishment component as described with reference to FIGs. 5 through 8.

FIG. 11 shows a flowchart illustrating a method 1100 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The operations of method 1100 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1100 may be performed by a communications manager as described with reference to FIGs. 5 through 8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1105, the UE may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The operations of 1105 may be performed according to the methods described herein. In some examples, aspects of the operations of 1105 may be performed by a PLMN identifier as described with reference to FIGs. 5 through 8.

At 1110, the UE may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The operations of 1110 may be performed according to the methods described herein. In some examples, aspects of the operations of 1110 may be performed by a PLMN list module as described with reference to FIGs. 5 through 8.

At 1115, the UE may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. The operations of 1115 may be performed according to the methods described herein. In some examples, aspects of the operations of 1115 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1120, the UE may assign a first priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell. The operations of 1120 may be performed according to the methods described herein. In some examples, aspects of the operations of 1120 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1125, the UE may assign a second priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a set of entries in the PLMN list for that candidate cell, where the second priority is lower than the first priority. The operations of 1125 may be performed according to the methods described herein. In some examples, aspects of the operations of 1125 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1130, the UE may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The operations of 1130 may be performed according to the methods described herein. In some examples, aspects of the operations of 1130 may be performed by a connection establishment component as described with reference to FIGs. 5 through 8.

FIG. 12 shows a flowchart illustrating a method 1200 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The operations of method 1200 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1200 may be performed by a communications manager as described with reference to FIGs. 5 through 8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1205, the UE may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The operations of 1205 may be performed according to the methods described herein. In some examples, aspects of the operations of 1205 may be performed by a PLMN identifier as described with reference to FIGs. 5 through 8.

At 1210, the UE may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The operations of 1210 may be performed according to the methods described herein. In some examples, aspects of the operations of 1210 may be performed by a PLMN list module as described with reference to FIGs. 5 through 8.

At 1215, the UE may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. The operations of 1215 may be performed according to the methods described herein. In some examples, aspects of the operations of 1215 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1220, the UE may assign a first priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell. The operations of 1220 may be performed according to the methods described herein. In some examples, aspects of the operations of 1220 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1225, the UE may assign a second priority to any one candidate cell of the set of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a set of entries in the PLMN list for that candidate cell, where the second priority is lower than the first priority. The operations of 1225 may be performed according to the methods described herein. In some examples, aspects of the operations of 1225 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1230, the UE may assign a third priority to any one candidate cell of the set of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, where the third priority is lower than the first priority and the second priority. The operations of 1230 may be performed according to the methods described herein. In some examples, aspects of the operations of 1230 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1235, the UE may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The operations of 1235 may be performed according to the methods described herein. In some examples, aspects of the operations of 1235 may be performed by a connection establishment component as described with reference to FIGs. 5 through 8.

FIG. 13 shows a flowchart illustrating a method 1300 that supports preventing service loss in non-standalone mode of a shared cell in accordance with aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 may be performed by a communications manager as described with reference to FIGs. 5 through 8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1305, the UE may receive a non-access stratum request identifying a first public land mobile network (PLMN) . The operations of 1305 may be performed according to the methods described herein. In some examples, aspects of the operations of 1305 may be performed by a PLMN identifier as described with reference to FIGs. 5 through 8.

At 1310, the UE may receive, from each candidate cell in a set of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell. The operations of 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be performed by a PLMN list module as described with reference to FIGs. 5 through 8.

At 1315, the UE may prioritize each candidate cell in the set of candidate cells based on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell. The operations of 1315 may be performed according to the methods described herein. In some examples, aspects of the operations of 1315 may be performed by a prioritization component as described with reference to FIGs. 5 through 8.

At 1320, the UE may perform a camping procedure or a connection procedure for a first candidate cell in the set of candidate cells based on the prioritizing. The operations of 1320 may be performed according to the methods described herein. In some examples, aspects of the operations of 1320 may be performed by a connection establishment component as described with reference to FIGs. 5 through 8.

At 1325, the UE may select the first candidate cell for the camping procedure or the connection procedure based on a determination that the first candidate cell has a highest priority of the set of candidate cells according to the prioritizing. The operations of 1325 may be performed according to the methods described herein. In some examples, aspects of the operations of 1325 may be performed by a cell selection component as described with reference to FIGs. 5 through 8.

It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein.

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 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 components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, 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 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. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 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 herein may 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 may be accessed by a general-purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM) , read-only memory (ROM) , electrically erasable programmable ROM (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 may be used to carry or store desired program code means in the form of instructions or data structures and that may 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 computer-readable 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 example 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. ” As used herein, the term “and/or, ” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

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 “example” 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, 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 having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill 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, comprising:

receiving a non-access stratum request identifying a first public land mobile network (PLMN) ;

receiving, from each candidate cell in a plurality of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell;

prioritizing each candidate cell in the plurality of candidate cells based at least in part on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell; and

performing a camping procedure or a connection procedure for a first candidate cell in the plurality of candidate cells based at least in part on the prioritizing.
The method of claim 1, wherein receiving, from each candidate cell in the plurality of candidate cells, the PLMN list comprises:

receiving a system information block from each candidate cell, the system information block comprising the PLMN list for that candidate cell.
The method of claim 1, wherein prioritizing each candidate cell in the plurality of candidate cells comprises:

assigning a first priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell.
The method of claim 3, wherein prioritizing each candidate cell in the plurality of candidate cells further comprises:

assigning a second priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a plurality of entries in the PLMN list for that candidate cell, wherein the second priority is lower than the first priority.
The method of claim 4, wherein prioritizing each candidate cell in the plurality of candidate cells further comprises:

assigning a third priority to any one candidate cell of the plurality of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, wherein the third priority is lower than the first priority and the second priority.
The method of claim 1, wherein performing the camping procedure or the connection procedure for the first candidate cell comprises:

selecting the first candidate cell for the camping procedure or the connection procedure based at least in part on a determination that the first candidate cell has a highest priority of the plurality of candidate cells according to the prioritizing.
The method of claim 6, wherein:

selecting the first candidate cell is further based at least in part on a signal strength of the first candidate cell.
The method of claim 1, wherein performing the camping procedure or the connection procedure for the first candidate cell comprises:

transmitting an attach request or a tracking area update request to the first candidate cell; and

receiving an attach accept message or a tracking area update accept message from the first candidate cell.
An apparatus for wireless communications, comprising:

a processor,

memory coupled to the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

receive a non-access stratum request identifying a first public land mobile network (PLMN) ;

receive, from each candidate cell in a plurality of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell;

prioritize each candidate cell in the plurality of candidate cells based at least in part on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell; and

perform a camping procedure or a connection procedure for a first candidate cell in the plurality of candidate cells based at least in part on the prioritizing.
The apparatus of claim 9, wherein the instructions to receiving, from each candidate cell in the plurality of candidate cells, the PLMN list are executable by the processor to cause the apparatus to:

receive a system information block from each candidate cell, the system information block comprising the PLMN list for that candidate cell.
The apparatus of claim 9, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells are executable by the processor to cause the apparatus to:

assign a first priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell.
The apparatus of claim 11, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells further are executable by the processor to cause the apparatus to:

assign a second priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a plurality of entries in the PLMN list for that candidate cell, wherein the second priority is lower than the first priority.
The apparatus of claim 12, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells further are executable by the processor to cause the apparatus to:

assign a third priority to any one candidate cell of the plurality of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, wherein the third priority is lower than the first priority and the second priority.
The apparatus of claim 9, wherein the instructions to perform the camping procedure or the connection procedure for the first candidate cell are executable by the processor to cause the apparatus to:

select the first candidate cell for the camping procedure or the connection procedure based at least in part on a determination that the first candidate cell has a highest priority of the plurality of candidate cells according to the prioritizing.
The apparatus of claim 14, wherein selecting the first candidate cell is further based at least in part on a signal strength of the first candidate cell.
The apparatus of claim 9, wherein the instructions to perform the camping procedure or the connection procedure for the first candidate cell are executable by the processor to cause the apparatus to:

transmit an attach request or a tracking area update request to the first candidate cell; and

receive an attach accept message or a tracking area update accept message from the first candidate cell.
An apparatus for wireless communications, comprising:

means for receiving a non-access stratum request identifying a first public land mobile network (PLMN) ;

means for receiving, from each candidate cell in a plurality of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell;

means for prioritizing each candidate cell in the plurality of candidate cells based at least in part on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell; and

means for performing a camping procedure or a connection procedure for a first candidate cell in the plurality of candidate cells based at least in part on the prioritizing.
The apparatus of claim 17, wherein the means for receiving, from each candidate cell in the plurality of candidate cells, the PLMN list comprises:

means for receiving a system information block from each candidate cell, the system information block comprising the PLMN list for that candidate cell.
The apparatus of claim 17, wherein the means for prioritizing each candidate cell in the plurality of candidate cells comprises:

means for assigning a first priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell.
The apparatus of claim 19, wherein the means for prioritizing each candidate cell in the plurality of candidate cells further comprises:

means for assigning a second priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a plurality of entries in the PLMN list for that candidate cell, wherein the second priority is lower than the first priority.
The apparatus of claim 20, wherein the means for prioritizing each candidate cell in the plurality of candidate cells further comprises:

means for assigning a third priority to any one candidate cell of the plurality of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, wherein the third priority is lower than the first priority and the second priority.
The apparatus of claim 17, wherein the means for performing the camping procedure or the connection procedure for the first candidate cell comprises:

means for selecting the first candidate cell for the camping procedure or the connection procedure based at least in part on a determination that the first candidate cell has a highest priority of the plurality of candidate cells according to the prioritizing.
The apparatus of claim 22, wherein selecting the first candidate cell is further based at least in part on a signal strength of the first candidate cell.
The apparatus of claim 17, wherein the means for performing the camping procedure or the connection procedure for the first candidate cell comprises:

means for transmitting an attach request or a tracking area update request to the first candidate cell; and

means for receiving an attach accept message or a tracking area update accept message from the first candidate cell.
A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

receive a non-access stratum request identifying a first public land mobile network (PLMN) ;

receive, from each candidate cell in a plurality of candidate cells, a PLMN list indicating one or more PLMNs supported by that candidate cell;

prioritize each candidate cell in the plurality of candidate cells based at least in part on a number of PLMNs supported by that candidate cell and whether the first PLMN occupies a first entry in the PLMN list for that candidate cell; and

perform a camping procedure or a connection procedure for a first candidate cell in the plurality of candidate cells based at least in part on the prioritizing.
The non-transitory computer-readable medium of claim 25, wherein the instructions to receiving, from each candidate cell in the plurality of candidate cells, the PLMN list are executable to:

receive a system information block from each candidate cell, the system information block comprising the PLMN list for that candidate cell.
The non-transitory computer-readable medium of claim 25, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells are executable to:

assign a first priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is the only entry in the PLMN list for that candidate cell.
The non-transitory computer-readable medium of claim 27, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells further are executable to:

assign a second priority to any one candidate cell of the plurality of candidate cells for which the first PLMN occupies the first entry in the PLMN list for that candidate cell and for which the first entry is one of a plurality of entries in the PLMN list for that candidate cell, wherein the second priority is lower than the first priority.
The non-transitory computer-readable medium of claim 28, wherein the instructions to prioritize each candidate cell in the plurality of candidate cells further are executable to:

assign a third priority to any one candidate cell of the plurality of candidate cells for which a PLMN other than the first PLMN occupies the first entry in the PLMN list for that candidate cell, wherein the third priority is lower than the first priority and the second priority.
The non-transitory computer-readable medium of claim 25, wherein the instructions to perform the camping procedure or the connection procedure for the first candidate cell are executable to:

select the first candidate cell for the camping procedure or the connection procedure based at least in part on a determination that the first candidate cell has a highest priority of the plurality of candidate cells according to the prioritizing.
The non-transitory computer-readable medium of claim 30, wherein selecting the first candidate cell is further based at least in part on a signal strength of the first candidate cell.
The non-transitory computer-readable medium of claim 25, wherein the instructions to perform the camping procedure or the connection procedure for the first candidate cell are executable to:

transmit an attach request or a tracking area update request to the first candidate cell; and

receive an attach accept message or a tracking area update accept message from the first candidate cell.