User equipment-based timing advance estimation

Abstract

The invention relates to techniques for UE-based TA estimation. For example, a UE may connect to a base station via a first cell, and may be configured with information for TA estimation based on the UE. The information may be included in a cell configuration of the second cell, a group configuration of a group of cells, or a measurement configuration. The UE may perform a first timing measurement on a first reference signal transmitted by the first cell and a second timing measurement on a second reference signal transmitted by the second cell. Upon commanding a connection to the second cell (e.g., for a first cell to second cell handover), the UE may determine a timing difference between two timing measurements and determine a second TA for the second cell based on the first TA of the first cell and the timing difference.

Description

[0001] Cellular communications can be defined in various standards to enable communication between a user equipment (UE) and a cellular network. For example, the fifth generation mobile network (5G) is a wireless standard that aims to improve data transmission speed, reliability, availability, etc. Cellular coverage is a relevant feature for data transmission. A UE can be instructed to establish a connection with different cells of a cellular network to maintain cellular coverage. Timing advance (TA) relates to the timing of transmissions by a UE within a cell. BRIEF DESCRIPTION OF DRAWINGS

[0002] Figure 1 Examples of a network environment are illustrated in accordance with some embodiments.

[0003] Figure 2 Examples of network coverage based on base stations and cells provided by such base stations are illustrated in accordance with some embodiments.

[0004] Figure 3 Examples of timing advance (TA) estimation based on a user equipment (UE) are illustrated in accordance with some embodiments.

[0005] Figure 4 Examples of procedures related to TA estimation based on a UE are illustrated in accordance with some embodiments.

[0006] Figure 5 Examples of information indicated in RRC configuration for TA estimation based on a UE are illustrated in accordance with some embodiments.

[0007] Figure 6 Examples of information indicated in RRC configuration for TA estimation based on a UE are illustrated in accordance with some embodiments.

[0008] Figure 7 Another example of information indicated in RRC configuration for TA estimation based on a UE is illustrated in accordance with some embodiments.

[0009] Figure 8 Examples of commands to trigger a timing measurement to compute TA are illustrated in accordance with some embodiments.

[0010] Figure 9 Examples of indicating a capability of a UE to support TA estimation based on a UE are illustrated in accordance with some embodiments.

[0011] Figure 10 Examples of commands to correct TA estimation based on a UE are illustrated in accordance with some embodiments.

[0012] Figure 11 Examples of operational flow / algorithmic structures implemented by a UE to perform TA estimation based on a UE are illustrated in accordance with some embodiments.

[0013] Figure 12 An example of an operational flow / algorithm structure implemented by a network for triggering UE-based TA estimation is illustrated in accordance with some embodiments.

[0014] Figure 13 An example of a receiving component is illustrated in accordance with some embodiments.

[0015] Figure 14 An example of a UE is illustrated in accordance with some embodiments.

[0016] Figure 15 An example of a base station is illustrated in accordance with some embodiments. DETAILED DESCRIPTION

[0017] The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings can identify the same or similar elements. In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of various aspects of various embodiments. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of various embodiments can be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods can be omitted so as not to obscure the description of various embodiments. Unless otherwise noted, the phrase “A or B” means (A), (B), or (A and B) in terms of the present document.

[0018] Generally, when a user equipment (UE) is in network coverage of a network, the UE communicates with the network. Network coverage can be provided via a cell of the network. The UE can be connected to a first cell and can receive a command to connect to a second cell (e.g., a handover from a current serving cell to a new serving cell). Rather than the network providing a timing advance (TA) for the second cell, the UE can perform a UE-based TA estimation to determine the TA. Specifically, the UE can perform a first time measurement on a first reference signal of the first cell and a second time measurement on a second reference signal of the second cell, and determine a timing difference between the two measurements. The UE-based estimation can also include determining the TA for the second cell as a function of the TA of the first cell and the timing difference (e.g., as a sum of them). The UE can transmit data (e.g., uplink frames) over the connection with the second cell, with the uplink transmissions being timed according to the estimated TA.

[0019] To be able to perform and use UE-based TA estimation, a UE can be configured (e.g., via radio resource control (RRC) signaling) with information about measurement objects and / or candidate cells on which UE-based TA estimation can be performed. These cells include the second cell, and their operation is generally time-synchronized (although the UE need not know the time synchronization). This configuration information can be available to the UE prior to a command to connect to the second cell. Upon meeting certain measurement criteria (e.g., a reference signal received power and / or a reference signal received quality associated with the first cell falling below a threshold), the UE can detect the second cell and perform time measurements on a second reference signal based on determining that the second cell is a candidate cell for UE-based time estimation. Upon receiving the command, the UE can determine that the command indicates the second cell and can complete an estimation of a TA for the second cell. By doing so, UE-based TA estimation can be enabled, thereby avoiding a need to provide a network-based TA to the UE (e.g., as part of a random access channel (RACH) procedure). Because UE-based TA estimation can be performed in a faster manner than a procedure for network-based TA, overall mobility latency and throughput can be improved. These and other aspects of the disclosure are described herein below.

[0020] The following is a glossary of terms that can be found in the disclosure.

[0021] As used herein, the term “circuitry” refers to, is part of, or includes: hardware components such as an electronic circuit, a logic circuit, a processor (shared, dedicated, or group) or memory (shared, dedicated, or group), an Application Specific Integrated Circuit (ASIC), a field-programmable device (FPD) (for example, a field-programmable gate array (FPGA), a programmable logic device (PLD), a complex PLD (CPLD), a high-capacity PLD (HCPLD), a structured ASIC, a programmable system-on-a-chip (SoC)), a digital signal processor (DSP), etc., that are configured to provide the described functionality. In some embodiments, circuitry can execute one or more software or firmware programs to provide at least some of the described functionality. The term “circuitry” can also refer to the combination of one or more hardware elements (or a combination of circuits used in electrical or electronic systems) with the program code that the hardware elements are used to execute. In these embodiments, the combination of hardware elements and program code can be referred to as a particular type of circuitry.

[0022] As used herein, the term “processor circuitry” refers to, is part of, or includes circuitry capable of sequentially and automatically processing a series of arithmetic or logical operations or recording, storing, or transferring digital data. The term “processor circuitry” can refer to an application processor, a baseband processor, a central processing unit (CPU), a graphics processing unit, a single-core processor, a dual-core processor, a triple-core processor, a quad-core processor, or any other device capable of executing or otherwise operating computer-executable instructions such as program code, software modules, and / or functional processes.

[0023] As used herein, the term “interface circuitry” refers to, is part of, or includes circuitry that enables the exchange of information between two or more components or devices. The term “interface circuitry” can refer to one or more hardware interfaces, such as a bus, an I / O interface, a peripheral component interface, or a network interface card, among others.

[0024] As used herein, the term “user equipment” or “UE” refers to a device with radio communication capabilities and can describe a remote user of network resources in a communication network. Further, the terms “user equipment” or “UE” can be considered synonymous, and can be referred to as a client, a device, a mobile, a mobile device, a mobile terminal, a user terminal, a mobile unit, a mobile station, a mobile user, a subscriber, a user, a remote station, an access agent, a user agent, a receiver, a radio, a reconfigurable radio, a reconfigurable mobile device, and the like. Further, the terms “user equipment” or “UE” can include any type of wireless / wired device or any computing device including a wireless communication interface. A UE can have the primary function as a communication device to another UE or a network, and the UE can be integrated with other devices and / or systems (e.g., in a vehicle).

[0025] As used herein, the term “base station” refers to a device with radio communication capabilities, i.e., a device of a communication network (or more simply a network), and can be configured as an access node in a communication network. Access of a UE to a communication network can be managed at least in part by a base station, whereby the UE connects with the base station to access the communication network. Depending on the radio access technology (RAT), a base station can be referred to as a gNodeB (gNB), an eNodeB (eNB), an access point, and the like.

[0026] As used herein, the term “computer system” refers to any type of interlinked electronic devices, computer devices, or components thereof. Additionally, the term “computer system” or “system” can refer to various components of a computer communicatively coupled to one another. Further, the term “computer system” or “system” can refer to multiple computer devices or multiple computing systems communicatively coupled to one another and configured to share computing resources or networking resources.

[0027] As used herein, the term "resource" refers to a physical or virtual device, a physical or virtual component within a computing environment, or a physical or virtual component within a particular device, such as a computer device, a mechanical device, memory space, processor / CPU time, processor / CPU usage, processor and accelerator load, hardware time or usage, power supply, input / output operations, port or network socket, channel / link allocation, throughput, memory usage, storage, network, database and application, units of work, and the like. A "hardware resource" can refer to computing, storage, or network resources provided by a physical hardware element. A "virtualized resource" can refer to computing, storage, or network resources provided by a virtualization infrastructure to an application, device, system, and the like. The term "network resource" or "communication resource" can refer to a resource that a computer device / system is able to access via a communication network. The term "system resource" can refer to any kind of shared entity that provides a service, and can include a computing resource or a network resource. A system resource can be considered as a set of coherent functionalities, network data objects, or services that are accessible through a server, where such system resources reside on a single host or multiple hosts and are clearly identifiable.

[0028] As used herein, the term "channel" refers to any tangible or intangible conveyance medium used to convey data or a stream of data. The term "channel" can be synonymous with or equivalent to "communication channel," "data communication channel," "transmission channel," "data transmission channel," "access channel," "data access channel," "link," "data link," "carrier wave," "radio frequency carrier wave," or any other similar term denoting a pathway or medium through which data is conveyed. Additionally, the term "link" as used herein refers to a connection made between two devices for transmitting and receiving information.

[0029] As used herein, the terms "to instantiate" and "instantiate" and the like refer to the creation of an instance. An "instance" also refers to a concrete occurrence of an object that may, for example, occur during execution of program code.

[0030] The term "connected" can mean that two or more elements have an established signaling relationship with each other over a communication channel, link, interface, or reference point at a common communication protocol layer.

[0031] As used herein, the term "network element" refers to physical or virtualized equipment or infrastructure used to provide wired or wireless communication network services. The term "network element" can be considered synonymous with or referred to as a networked computer, networked hardware, network equipment, network node, virtualized network function, and the like.

[0032] The term "information element" refers to a structural element containing one or more fields. The term "field" refers to individual content of an information element, or a data element containing content. An information element can include one or more additional information elements.

[0033] Figure 1 A network environment 100 is illustrated in accordance with some embodiments. The network environment 100 can include a UE 104 and a network node 108. The network node 108 can be a base station providing a wireless access cell; for example, a Third Generation Partnership Project (3GPP) New Radio (NR) cell through which the UE 104 can communicate with the network node 108. The base station can be a component of a terrestrial network. The UE 104 and the network node 108 can communicate through an interface that is compatible with 3GPP technical specifications, such as technical specifications defining standards for a Fifth Generation (5G) NR system.

[0034] The network node 108 can transmit information (e.g., data and control signaling) in the downlink direction by mapping logical channels onto transport channels and then mapping the transport channels onto physical channels. Logical channels can pass data between the RLC and MAC layers; transport channels can pass data between the MAC and PHY layers; and physical channels can pass information across the air interface. Physical channels can include a physical broadcast channel (PBCH); a physical downlink control channel (PDCCH); and a physical downlink shared channel (PDSCH).

[0035] The PBCH can be used to broadcast system information that the UE 104 can use for initial access to a serving cell. The PBCH can be transmitted in a synchronization signal (SS) / PBCH block along with a physical synchronization signal (PSS) and a secondary synchronization signal (SSS). The SS / PBCH block (SSB) can be used by the UE 104 during a cell search procedure and for beam selection.

[0036] The PDSCH can be used to pass terminal user application data, signaling radio bearer (SRB) messages, system information messages (except, for example, the MIB), and paging messages.

[0037] The PDCCH can pass downlink control information (DCI) that is used by a scheduler of the network node 108 to allocate both uplink and downlink resources. The DCI can also be used to provide uplink power control commands, configure a time slot format, or indicate that pre-emption has occurred.

[0038] The network node 108 can also transmit various reference signals to the UE 104. The reference signals can include demodulation reference signals (DMRS) for the PBCH, the PDCCH, and the PDSCH. The UE 104 can compare a received version of the DMRS with a known DMRS sequence that was transmitted to estimate the effects of the propagation channel. The UE 104 can then apply an inverse channel of the propagation channel during a demodulation process for transmissions of the corresponding physical channel.

[0039] The reference signals can also include CSI-RS. The CSI-RS can be a multi-purpose downlink transmission that can be used for CSI reporting, beam management, connected mode mobility, radio link failure detection, beam failure detection and recovery, and fine tuning of time and frequency synchronization.

[0040] The reference signals and information from the physical channels can be mapped to resources of a resource grid. There is one resource grid for a given antenna port, subcarrier spacing configuration, and transmission direction (e.g., downlink or uplink). The basic unit of the resource grid is a resource element, which can be defined by one subcarrier in the frequency domain and one orthogonal frequency-division multiplexing (OFDM) symbol in the time domain. Twelve consecutive subcarriers in the frequency domain can constitute a physical resource block (PRB). A resource element group (REG) can include one PRB in the frequency domain and one OFDM symbol in the time domain, e.g., twelve resource elements. A control channel element (CCE) can represent a grouping of resources for transmitting a PDCCH. One CCE can be mapped to multiple REGs; for example, six REGs.

[0041] Transmissions using different antenna ports can experience different radio channels. However, in some cases, different antenna ports can share common radio channel characteristics. For example, different antenna ports can have similar Doppler shift, Doppler spread, average delay, delay spread, or spatial receiver parameters (e.g., characteristics associated with a downlink receive signal angle of arrival at the UE). Antenna ports that share one or more of these large-scale radio channel characteristics can be considered to be quasi co-located (QCL) with each other. 3GPP has specified four types of QCL to indicate which particular channel characteristics are shared. In QCL Type A, antenna ports share Doppler shift, Doppler spread, average delay, and delay spread. In QCL Type B, antenna ports share Doppler shift and Doppler spread. In QCL Type C, antenna ports share Doppler shift and average delay. In QCL Type D, antenna ports share spatial receiver parameters.

[0042] The network node 108 can provide transmission configuration indicator (TCI) state information to the UE 104 to indicate QCL relationships between antenna ports for reference signals (e.g., synchronization signals / PBCH or CSI-RS) and downlink data or control signaling (e.g., PDSCH or PDCCH). The network node 108 can use a combination of RRC signaling, MAC control element signaling, and DCI to inform the UE 104 of these QCL relationships.

[0043] The UE 104 can use a physical uplink channel to transmit data and control information to the network node 108. Different types of physical uplink channels are possible, including a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH). The PUCCH carries control information from the UE 104 to the network node 108, such as uplink control information (UCI), while the PUSCH carries data traffic (e.g., end-user application data) and can carry UCI.

[0044] In one example, communication with the network node 108 and / or base station can use channels in a frequency range 1 (FR1) band (between 40 megahertz (MHz) and 7, 125 MHz) and / or a frequency range 2 (FR2) band (between 24,250 MHz and 52,600 MHz), although other frequency ranges are possible (e.g., frequency ranges with frequencies greater than 52,600 MHz). The FR1 band includes licensed and unlicensed frequency bands. The NR unlicensed band (NR-U) includes spectrum shared with other types of radio access technologies (RATs) (e.g., LTE-LAA, WiFi, etc.). Listen-before-talk (LBT) procedures can be used to avoid or minimize collisions between different RATs in the NR-U, whereby a device applies a clear channel assessment (CCA) check before using a channel.

[0045] In one example, the network node 108 is a base station that includes a CU and / or one or more DUs. In this example, network coverage provided to the UE 104 can change over time and / or depending on the location of the UE 104. Inter-DU mobility procedures or intra-DU mobility procedures can be performed to support mobility of the UE 104 and provide appropriate network coverage.

[0046] In particular, a DU can provide multiple cells (e.g., each cell provided via a transmission and reception point (TRP) connected to the DU). The DU can tightly synchronize the clocks of these cells such that their TAs can be time-synchronized. Thus, these cells can be candidate cells for UE-based TA estimation. In the context of layer 1 (L1) / layer 2 (L2) mobility, such cells can be referred to as L1 / L2 triggered mobility (LTM) cells, which are candidate cells for UE-based TA estimation.

[0047] The UE 104 can be camped in a serving cell. The base station can configure the UE 104 with multiple candidate LTM cells for UE-based TA estimation. For example, the base station can use one or more RRC messages to configure the UE 104 with groups of candidate LTM cells, where each group is provided by a DU of the base station.

[0048] In some instances, there can be a connection problem, such as a radio link failure or signal quality degradation, between the UE 104 and a serving cell. In response to the connection problem, the UE 104 can search for a neighboring cell to establish a connection with another cell from a group of candidate cells. The candidate cells can include some or all of the candidate LTM cells. In some instances, the candidate LTM cells can have a higher priority than the candidate non-LTM cells. The procedure to determine the TA of the target cell can depend on the selected target cell.

[0049] Specifically, if the target cell is a candidate LTM cell that belongs to the same group as the serving cell, the UE can perform UE-based TA estimation to determine the TA. If the target cell is a candidate non-LTM cell or a candidate LTM cell that belongs to a different group than the serving cell, the UE can not perform UE-based TA estimation. Instead, the UE can receive a network-based TA (e.g., a TA transmitted by a base station). Examples of LTM cells and related TA information are described in the following figures.

[0050] Figure 2 Examples of network coverage based on base stations and cells provided by such base stations are illustrated in accordance with some embodiments. The network can include a base station (which is an example of a network node 108) and can communicate with a UE 204 (which is an example of a UE 104) via the base station. The base station can include a CU and / or one or more DUs. In some embodiments, the base station can be a gNB, an eNB, etc. In Figure 2 In examples, the base station is illustrated as a gNB. In such examples, the CU of the gNB can be referred to as a gNB-CU and the DUs of the gNB can be referred to as gNB-DUs.

[0051] For illustrative purposes, Figure 2 A gNB-DU 210 and a gNB-CU 220 are illustrated. The gNB-DU 210 is connected to the gNB-CU 220 (although additional gNB-DUs can be connected to the gNB-CU 220 and / or the gNB-CU 220 can be connected to additional gNB-CUs of the network). The operations of the gNB-DU 210 can be controlled in part by the gNB-CU 220. The gNB-CU 220 can terminate the Fl interface that the gNB-DU 210 connects with. The gNB-DU 210 can terminate the Fl interface that the gNB-CU 220 connects with.

[0052] The gNB-CU 220 can be a logical node hosting at least one of the RRC, service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols of the base station. The gNB-DU 210 can be a logical node hosting at least one of the RLC, MAC, and physical (PHY) layers of the base station. The gNB-DU 210 can provide or support one or more cells. One cell is supported by one DU only. For example, the gNB-DU 210 can provide cells 230 (with physical cell ID “0” shown as PCI0), 231 (with physical cell ID “1” shown as PCI1), and 233 (with physical cell ID “3” shown as PCI3), 234 (with physical cell ID “4” shown as PCI4), 235 (with physical cell ID “5” shown as PCI5), and 236 (with physical cell ID “6” shown as PCI6). Each cell can be provided by a TRP connected to the gNB-DU 210. As used herein, a cell can refer to a TRP and / or a component of a base station that enables communication with a UE.

[0053] The cells 230-236 can be configured as candidate LTM cells for the UE 204. As Figure 2 As further illustrated in the middle, two sets of cells 230-236 are time synchronized: a first set 240 including cells 231-234 and a second set 250 including cells 235-236. Cell 230 is not time synchronized with any of the remaining cells. In particular, the clocks of the TRPs of cells 231-234 can be tightly controlled (e.g., by the gNB-DU 210 and / or the gNB-CU 220) such that the time difference between the clocks of the TRPs is known to the network (e.g., to the gNB-DU 210 and / or the gNB-CU 220) and can be minimal, reduced, or eliminated. Similarly, the clocks of the TRPs of cells 235-236 can be tightly controlled (e.g., by the gNB-DU 210 and / or the gNB-CU 220) such that the time difference between the clocks of the TRPs is known to the network. The clock synchronization of the first set 240, the clock synchronization of the second set 250, and the clock synchronization associated with cell 230 need not be tightly coordinated.

[0054] It should be understood that the number of UEs, CUs, and / or DUs and the grouping of LTM cells are for purposes of illustration only and do not imply any limitation on the present disclosure. A network can include any suitable number of UEs, CUs, and DUs suitable to implement an embodiment of the present disclosure.

[0055] Communications within the network may conform to any suitable standard, including but not limited to Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSMEDGE Radio Access Network (GERAN), Machine Type Communications (MTC), etc.

[0056] Furthermore, communication can be performed according to any generation of communication protocols currently known or to be developed in the future. Examples of communication protocols include, but are not limited to, first-generation (1G) communication protocols, second-generation (2G) communication protocols, 2.5G communication protocols, 2.75G communication protocols, third-generation (3G) communication protocols, fourth-generation (4G) communication protocols, 4.5G communication protocols, and fifth-generation (5G) communication protocols.

[0057] use Figure 2 As illustrated, UE 204 is connected to the serving cell (e.g., in connected mode). UE 204 can then establish a second connection with the target cell (e.g., during handover to a new serving cell). If the target cell and the serving cell are in the same set (e.g., first set 240 or second set 250), UE 204 can perform UE-based TA estimation given a coordination time difference. If the target cell and the serving cell are not in the same set (e.g., one cell is in first set 240, and the other is in second set 250 or cell 230), UE-based TA estimation may not be performed.

[0058] In one example, UE 204 may access a cell provided by gNB-DU 210. For example, UE 204 may initially connect to cell 234. Based on measurements, UE 204 may execute intra-DU mobility procedures to move from cell 234 to another cell provided by the first gNB-DU 210. For example, UE 204 may execute intra-DU mobility procedures to move to one of cells 231 or 233 in the first set 240 in a first case, or to one of cells 235 or 236 in the second set 250 in a second case. In the following text, intra-DU mobility is also referred to as gNB-DU intra-mobility.

[0059] Alternatively, based on the measurement results, UE 204 may execute inter-DU mobility procedures to move from cell 234 provided by gNB-DU 210 to a cell provided by another gNB-DU connected to gNB-CU in a third scenario. Hereinafter, inter-DU mobility is also referred to as gNB-DU mobility.

[0060] In the first case, UE-based TA estimation can be performed. In the second and third cases, UE-based TA estimation should not be performed.

[0061] In some embodiments, the UE 204 can be in dual connectivity (DC) with the gNB-CU 220. When the gNB-CU 220 is configured as a secondary node (SN) and the gNB-CU 240 is configured as a master node (MN) in the DC configuration, intra-DU mobility procedures and inter-DU mobility procedures can be allowed.

[0062] Figure 3 An example of UE-based TA estimation is illustrated, in accordance with some embodiments. UE-based TA estimation can also be referred to as UE-based TA acquisition, or more generally, TA estimation or TA acquisition performed by a UE.

[0063] In the example illustration, the UE is connected to a serving cell. At a first time, the UE receives a downlink frame 310 of the serving cell. At a second time, the UE transmits an uplink frame 320 to the serving cell. The second time is illustrated in Figure 3 as being before the first time by a first TA 310 corresponding to communications between the UE and the serving cell.

[0064] The UE can also not be connected to a neighboring cell (although a connection can have been established). At a third time, the UE receives a downlink frame 330 of the neighboring cell. The downlink frame 330 can indicate a reference signal (e.g., SSB, CSI-RS, etc.), where such a reference signal can be represented by one or more symbols of the downlink frame 330. The difference between the first time and the third time is illustrated in Figure 3 as a UE measured timing difference 302. Specifically, the UE can perform a timing measurement on the reference signal to determine the third time (e.g., the start of the DL frame 330) to then derive the time difference 302 relative to the start of the downlink frame 310 (e.g., where the first time can also be derived from the reference signal indicated in the downlink frame 310).

[0065] To transmit an uplink frame to the neighboring cell (e.g., once the UE is in connected mode with the neighboring cell), the UE can perform a UE-based time estimation of a second TA 302 for such an uplink frame. Here, the second TA 303 can be a function (e.g., a sum) of the first TA 301 and the timing difference 302.

[0066] In one example, the timing difference 302 measured by the UE can equal (or substantially equal within an acceptable margin of tolerance) a network coordinated time difference between the cells.

[0067] To ensure that the UE actual uplink timing is sufficiently close to the ideal (or intended) uplink timing, tight synchronization across cells is needed. It can be assumed that the absolute value of the uplink timing difference towards the serving cell and the target cell is the same as the absolute value of the downlink timing difference measured at the UE.

[0068] For non-synchronized networks, the measured TA includes both the synchronization error and the propagation delay difference between the two cells, which cannot be distinguished by the UE. Therefore, the measured timing difference cannot be used for uplink timing determination towards the target cell.

[0069] Tight synchronization can be achieved through a global navigation satellite system (GNSS), possibly in time division duplex (TDD) systems. There is no need to inform the UE how the network achieves synchronization. The base station can be aware of the synchronization, and this awareness can be specific to the base station implementation.

[0070] Since the strict synchronization requirement is specific to the base station implementation, techniques are needed to inform the UE which set of cells is strictly synchronized (so that the UE-based TA estimation can be allowed to be used). A signaling framework is also needed to trigger the timing measurement of the neighbor cell reference signals. Similarly, the network needs a signaling framework to inform the UE to perform the TA-based adjustment (e.g., in the context of LTM handover where the UE switches from one LTM cell to another). If the UE does not support UE-based TA estimation, the signaling framework needs to allow the UE not to perform the estimation. Similarly, if the target cell cannot handle RACH-less LTM handover, the network needs to be able to inform the UE not to perform the UE-based TA estimation (even when the UE is capable of doing so). Error correction of the TA after the UE has applied the TA-based estimation also needs to be supported. These and other features of the UE-based TA estimation techniques are further described herein below.

[0071] Figure 4 An example of a procedure related to UE-based TA estimation is illustrated in accordance with some embodiments. The procedure can be implemented by a UE 410 (an example of UE 204) and a network 420 (such as the network described herein above) including a base station CU and a DU. Generally, the UE 410 receives configuration information from the network 420 (e.g., its gNB-CU) for one or more sets of candidate cells for intra-DU mobility and / or for one or more sets of candidate cells for inter-DU mobility. The configuration information can be received via RRC signaling. Subsequently, the UE 410 can perform timing measurements on downlink signals across some or all of the candidate cells. Upon being instructed to establish one or more connections (e.g., via a MAC handover command), the UE can use one or more of the timing measurements to derive at least a TA for the new connection, and can use the TA for uplink transmission over the connection.

[0072] In the example illustration, the UE 410 receives an RRCReconfiguration message from the network 420 (or multiple ones of such messages from, e.g., a gNB-CU). The received RRC reconfiguration information indicates, among other things, a configuration of candidate cells including LTM candidate cells. The configuration for a candidate LTM cell can be referred to herein as an LTM candidate cell configuration. Additionally, the received RRC reconfiguration information indicates a configuration for a set of LTM cells (e.g., each set represents a set of cells with LTM association that can allow the UE to perform UE-based TA estimation). The configuration for a set of LTM cells can be referred to herein as an LTM group configuration. The LTM group configuration can be separate from and possibly referenced in the LTM cell configuration. Additionally or alternatively, the received RRC reconfiguration information indicates a configuration for one or more measurement objects. Such configuration can be referred to herein as a measurement object configuration. The measurement object configuration can indicate whether UE-based TA estimation is allowed. The UE 410 can respond to the network 420 (e.g., to the gNB-CU) with an RRCReconfigurationComplete message (or multiple ones of such messages).

[0073] Next, the UE can determine that a set of criteria is satisfied to trigger timing measurements. The set can relate to connection conditions, such as the RSRP and / or RSRQ of the serving cell falling below a threshold and / or the RSRP and / or RSRQ of a detected neighbor cell exceeding a threshold. Here, the UE can perform timing measurements on downlink reference signals (e.g., SSBs and / or CSI-RSs) of various cells. In one example, the cells can include the serving cell and the neighbor cell. In this example, timing measurements need not be performed on all neighbor cells. Specifically, the timing measurements can be used to possibly and subsequently complete UE-based TA estimation. Thus, timing measurements can be performed on candidate cells that belong to the same LTM group as the serving cell, such as candidate LTM cells. Timing measurements need not be performed on other detected neighbor cells.

[0074] The UE 410 can receive a connection command (e.g., a MAC CE for a handover for LTM handover) from the network 420 (e.g., from a gNB-CU or gNB-DU of a serving cell that the UE 410 is pre-occupied). The command can indicate a target cell, and optionally, a trigger for UE-based TA estimation (if applicable). If not explicitly indicated in the connection command, the UE can determine whether to implicitly trigger UE-based TA estimation. Specifically, based on the source cell (e.g., the current serving cell) and the target cell, the UE 410 can determine whether there is an LTM association between the two cells and whether UE-based TA estimation is to be used (e.g., in the case that the two cells belong to the same LTM group) according to LTM cell configuration information, LTM group configuration information, and / or measurement object configuration information. If so, the UE estimates a TA for uplink frame transmission to the target cell using timing measurements of the two cells determined prior to the connection command (e.g., as described in Figure 3

[0075] The UE 410 can then establish a connection with the target cell (e.g., with the associated TRP) by performing a handover. Data can then be exchanged between the UE 410 and the target cell. Uplink data transmission from the UE can be timed according to the determined TA. The network 420 (e.g., the gNB-CU or DU) can detect from the uplink data that the TA is incorrect (e.g., its value can exceed a certain threshold) (e.g., based on measurements of uplink frames). In this case, the network 420 can send a TA correction command. The command can be a Random Access Response (RAR) MAC CE (even when no RACH procedure is performed) and / or a TA MAC CE.

[0076] Figure 5 Examples of information indicated in RRC configuration for UE-based TA estimation are illustrated according to some embodiments. The RRC configuration information can be received from a base station CU and can indicate LTM cell configuration, LTM group configuration, and / or measurement object configuration, etc. for candidate LTM cells. Any or a combination of these configurations can indicate whether UE-based TA estimation is allowed (or enabled) and / or parameters for using UE-based estimation (e.g., a group of cells or candidate cells that allow UE-based TA estimation).

[0077] In Figure 5 ​In the example illustration of FIG. 5, the RRC configuration information indicates an RRCReconfiguration 510 that can be received from a gNB-CU (e.g., gNB-CU 220) of the base station. This RRCReconfiguration 510 can include a master cell group (MCG) configuration 512 and a secondary cell group (SCG) configuration 514. In addition, the RRCReconfiguration 510 includes a UE-based TA estimation indication 516. This indication 516 can correspond to or be included in, for example, a measurement object configuration for a measurement object, and can be used by the UE to determine whether UE-based TA estimation is allowed (or enabled) or disallowed (or disabled) for measurements associated with the measurement object.

[0078] In the example illustration of FIG. 5, the RRC configuration information indicates an RRCReconfiguration 510 that can be received from a gNB-CU (e.g., gNB-CU 220) of the base station. This RRCReconfiguration 510 can include a master cell group (MCG) configuration 512 and a secondary cell group (SCG) configuration 514. In addition, the RRCReconfiguration 510 includes a UE-based TA estimation indication 516. This indication 516 can correspond to or be included in, for example, a measurement object configuration for a measurement object, and can be used by the UE to determine whether UE-based TA estimation is allowed (or enabled) or disallowed (or disabled) for measurements associated with the measurement object. Figure 5 In the example illustration of FIG. 5, the RRC configuration information indicates an RRCReconfiguration 510 that can be received from a gNB-CU (e.g., gNB-CU 220) of the base station. This RRCReconfiguration 510 can include a master cell group (MCG) configuration 512 and a secondary cell group (SCG) configuration 514. In addition, the RRCReconfiguration 510 includes a UE-based TA estimation indication 516. This indication 516 can correspond to or be included in, for example, a measurement object configuration for a measurement object, and can be used by the UE to determine whether UE-based TA estimation is allowed (or enabled) or disallowed (or disabled) for measurements associated with the measurement object. Figure 2 In the example illustration of FIG. 5, the RRC configuration information indicates an RRCReconfiguration 510 that can be received from a gNB-CU (e.g., gNB-CU 220) of the base station. This RRCReconfiguration 510 can include a master cell group (MCG) configuration 512 and a secondary cell group (SCG) configuration 514. In addition, the RRCReconfiguration 510 includes a UE-based TA estimation indication 516. This indication 516 can correspond to or be included in, for example, a measurement object configuration for a measurement object, and can be used by the UE to determine whether UE-based TA estimation is allowed (or enabled) or disallowed (or disabled) for measurements associated with the measurement object.

[0079] In addition, the LTM configuration 520 includes a UE-based TA estimation indication 524. In one example, the indication 524 is for a group of candidate LTM cells (e.g., one indication for the first set 240, and a second indication for the second set 250). This indication 524 can correspond to or be included in, for example, an LTM group configuration for the group, and can be used by the UE to determine whether UE-based TA estimation is allowed (or enabled) or disallowed (or disabled) for measurements associated with candidate LTM cells belonging to the group.

[0080] As Figure 5Further to the illustration, each of the LTM cell configurations 522 can correspond to a candidate LTM cell and include its own RRCReconfiguration. In turn, each of such RRCReconfigurations can include a UE-based TA estimation indication that informs whether UE-based TA estimation can be used in association with the corresponding candidate LTM cell. In Figure 5 In the illustration, a first LTM cell configuration of the LTM cell configurations 522 corresponds to a first LTM cell (e.g., PCI0), a second LTM cell configuration of the LTM cell configurations 522 corresponds to a second LTM cell (e.g., PCI1), and so on, until a kth LTM cell configuration of the LTM cell configurations 522 corresponds to a kth LTM cell (e.g., PCI6). The first LTM cell (e.g., PCI0) can have a first RRC configuration 530 that includes a reference configuration 532 (e.g., one command for a candidate LTM cell), a delta configuration 534 (e.g., one specific to the candidate LTM cell), and a UE-based TA estimation indication 535. Similarly, the second LTM cell (e.g., PCI1) can have a second RRC configuration 540 that includes a reference configuration 542 (e.g., one command for a candidate LTM cell), a delta configuration 544 (e.g., one specific to the candidate LTM cell), and a UE-based TA estimation indication 545. Additionally or alternatively, the kth LTM cell (e.g., PCI6) can have a kth RRC configuration 550 that includes a reference configuration 552 (e.g., one command for a candidate LTM cell), a delta configuration 554 (e.g., one configuration specific to the candidate LTM cell), and a UE-based TA estimation indication 555. These and other configuration variants are further illustrated in the following figures.

[0081] Figure 6 Examples of information indicated in RRC configurations for UE-based TA estimation are illustrated in accordance with some embodiments. Figure 6 A first example is illustrated in the upper left side of Figure 6 A second example is illustrated in the lower right side of In both examples, the network provides a set of LTM cells to be considered by the UE as candidates for UE-based TA estimation. In both examples, information about the cells (e.g., the first set 240 or the second set 250) is provided as part of an RRC configuration.

[0082] In the first example, each candidate cell has its own candidate cell configuration information 610. The candidate cell configuration information 610 of a candidate cell includes a UE-based TA estimation indication 620 indicating whether this candidate cell is to be considered as a potential candidate for UE-based TA estimation. If yes, upon detecting a candidate cell (e.g., by receiving reference signals from it but not being in connected mode with it), the UE can perform timing measurements on such reference signals and can use these timing measurements to derive the TA of the candidate cell upon receiving a command triggering the use of UE-based TA estimation. Otherwise, no timing measurements can be performed and the UE can expect to receive a network-based TA for the candidate cell.

[0083] In the context of the 5G NR system, the following information can be defined in the technical specification to obtain the above method for explicit group configuration.

[0084]

[0085] In the first example, each candidate cell also has its own candidate cell configuration information. However, here, the UE is configured with an LTM group configuration (e.g., for the first set 240 or the second set 250). Specifically, a set of cell information 630 is stored by the UE and corresponds to this group configuration. The set of cell information 630 includes a UE-based TA estimation indication 640 indicating whether each cell in this set is to be considered as a potential candidate for UE-based TA estimation. If yes, upon detecting a candidate cell of this set (e.g., by receiving reference signals from it but not being in connected mode with it), the UE can perform timing measurements on such reference signals and can use these timing measurements to derive the TA of the candidate cell upon receiving a command triggering the use of UE-based TA estimation. Otherwise, no timing measurements can be performed and the UE can expect to receive a network-based TA for the candidate cell. Thus, the set of candidate cells is considered as a whole for UE-based TA estimation. The UE is only allowed to use this method when it is within these cells. For example, when the UE is connected to a serving cell and receives reference signals of another cell, and when these two cells belong to the same set for which the UE-based TA estimation indication 640 indicates that UE-based TA estimation is allowed, the UE can then perform timing measurements that can be subsequently used to determine the TA of the other cell.

[0086] In the context of the 5G NR system, the following information can be defined in the technical specification to obtain the above method for explicit group configuration.

[0087]

[0088]

[0089] Figure 7Another example of information indicated in RRC configuration for UE-based TA estimation is illustrated according to some embodiments. As in Figure 6 Unlike the information described in the above, the information here is related to measurement objects. For example, as part of the candidate cell configuration, the network does not provide any configuration on which LTM cells will be considered for UE-based TA estimation. Instead, as part of the measurement configuration, the UE is configured with which target measurement cells will be considered for UE-based TA estimation.

[0090] Figure 7 This approach is illustrated in, whereby the UE stores measurement configuration information 710 and cell configuration information 730. The measurement configuration information 710 corresponds to one or more measurement configurations, while the cell configuration information 730 corresponds to one or more cell configurations. The measurement configurations are separate and excluded from the cell configurations, and vice versa. The measurement configuration information 710 includes a UE-based TA estimation indication 720 that indicates whether UE-based TA estimation is allowed (or enabled) or not allowed (or disabled) for the configured measurement (or set of configured measurements).

[0091] In one example, the measurement configuration for a measurement corresponds to the measurement configuration information 710 and can be transmitted as part of the serving cell that configures the measurement. In the context of a 5G NR system, the following information can be defined in the technical specification to obtain the above approach for explicit group configuration.

[0092]

[0093] In another example, the measurement configuration for a measurement corresponds to the measurement configuration information 710 and can be transmitted as part of a candidate neighboring cell. In the context of a 5G NR system, the following information can be defined in the technical specification to obtain the above approach for explicit group configuration.

[0094]

[0095]

[0096] In another example, the measurement configuration for a measurement corresponds to the measurement configuration information 710 and can be configured independently of the LTM cells (e.g., including the serving cell and the candidate neighboring cells). In the context of a 5G NR system, the following information can be defined in the technical specification to obtain the above approach for explicit group configuration.

[0097]

[0098]

[0099] Figure 8An example of a command to trigger a timing measurement to compute TA is illustrated according to some embodiments. The UE can have been configured for UE-based TA estimation as described herein above. Thus, the UE can perform a timing measurement for a candidate cell according to the configuration. Subsequently, the network can send a command to the UE to trigger completion of the UE-based TA estimation. Specifically, the command can indicate a target cell, and the UE can use the relevant timing measurement to derive a TA for uplink transmissions to the target cell. The trigger can be explicit by indicating that UE-based TA estimation is to be used. Alternatively, the trigger can be implicit, whereby the UE can determine based on the target cell and the source cell that the relevant configuration allows for UE-based TA estimation.

[0100] In one example, the command comprises a MAC CE command. For example, the measurement trigger (to use time measurement in order to determine the timing difference 302 and compute TA 303) can come from a MAC CE. The MAC CE can include the target cell for which the timing difference 302 is needed. This approach means that there is no RRC-specific configuration for UE-based TA estimation. Instead, at runtime, the network triggers the UE to measure the timing difference 302 via a MAC CE.

[0101] In another illustration, as part of a MAC CE for LTM handover, the network can provide a trigger that the UE should measure the timing difference 302 for a target cell, and then derive TA 303 based on the timing difference 302, so that the UE applies TA 303 as part of the LTM handover. In this illustration, the network can control the UE-based TA estimation application based on whether the target TRP / cell actually supports the feature, regardless of whether the source and target cells are tightly synchronized. For this illustration, multiple approaches are possible. In one approach, the UE performs the timing difference computation and derives TA 303 as part of the LTM handover command. In another approach, the network first sends a MAC CE (as in the illustration above) to trigger the UE to perform the timing difference computation and derive TA 303. However, the UE does not actually apply TA 302 until an LTM handover MAC CE is received from the network.

[0102] Figure 8The above two figures are illustrated with a MAC CE (e.g., like the handover MAC CE in the first figure or the LTM MAC CE in the second figure) that indicates the configuration type (e.g., can be used for UE-based TA estimation). The MAC CE includes a MAC CE type differentiation 810 that indicates the configuration type (e.g., can be used for UE-based TA estimation), a trigger for UE-based TA estimation 820 (e.g., used in case of explicit trigger, where the trigger 820 can indicate whether to derive and apply TA, or to derive but not apply TA, or to apply TA if previously derived), and target neighbor cell SSB information or index for timing difference computation 830 (e.g., which can identify the target cell and specific reference signal to use), and other information. Each of this type of information can be set according to its specific scenario in the MAC CE.

[0103] Figure 9 An example of indicating the capability of the UE 910 to support UE-based TA estimation is illustrated in accordance with some embodiments. In one example, the UE 910 sends capability information to the network (e.g., via RRC signaling) indicating whether the UE 910 supports UE-based TA estimation. Additionally or alternatively, the capability information can be more granular, whereby the UE 910 can indicate its support for UE-based TA estimation in association with one or more parameters. These parameters can include frequency, frequency band, frequency band combination, number of target cells, number of frequencies, number of frequency bands, number of frequency band combinations, etc. The network can then configure the UE 910 based on the capability information, and can subsequently trigger UE-based TA estimation when applicable.

[0104] In Figure 9 In the illustrated example, the network includes an NR cell 920 and a core network 930. The UE 910 determines that cell selection criteria are met to select the NR cell 920, such that a connection can be established with it according to a registration procedure. Next, the registration procedure is performed. As part of this procedure, UE capability exchange is performed. Specifically, the NR cell 920 sends a UE capability query to the UE 910 requesting the UE 910 to indicate its capability to support UE-based TA estimation. The UE 910 then responds with a capability response indicating its capability to support UE-based TA estimation. The NR cell 920 can send the received UE capability information to the core network 930 for storage and subsequent use (e.g., by the NR cell 920 or other cells of the network 930).

[0105] In one example, the UE capability indicates whether the UE 910 is capable of performing UE-based TA estimation based on measuring downlink reference signals of a target cell. In one approach, the UE capability is such that if the UE 910 reports support for UE-based TA estimation, the UE capability also indicates whether the UE 910 can measure / derive on any target frequency regardless of whether the UE 910's current serving frequency is the same or different from the frequency of the target cell. In another approach, the UE capability can be reported as an intra-frequency capability. Specifically, when the UE reports UE-based TA estimation, then the intra-frequency capability indicates the UE's 910 capability to derive TA estimates for all target neighbor cells that are on the same frequency as the serving cell. In another approach, the UE capability can be reported as a per-band capability. Specifically, the UE capability can be reported per band, where when the UE 910 reports capability for a particular band, then the UE 910 has the capability to derive TA estimates for all target neighbor cells in that band. In yet another approach, the UE capability can be reported as a per-band combination capability. In this approach, when the UE 910 reports capability for a band combination, then the UE 910 has the capability to derive TA estimates for all target neighbor cells that are part of the band combination. Additionally or alternatively, the UE 910 can report both per-band and per-band combination UE capability. Specifically, when the UE 910 reports a band combination, the UE 910 also reports a set of bands, and the UE 910 is capable of deriving TA estimates for all target neighbor cells on that set of bands as long as the UE 910 operates in that band combination (e.g., the serving cell uses the bands of that band combination).

[0106] In one example, the UE 910 can report its capability regarding how many potential target cell reference signals the UE 910 can measure / keep for future LTM switching. In one approach, the UE 910 can report a UE capability that informs the network of how many timing (e.g., number) differences 302 the UE 910 can measure to derive TA. The number can be a number (e.g., maximum number) of target cells, target frequencies, bands, and / or band combinations. Of course, any of the last two examples can be used as part of the UE capability.

[0107] In one example, the UE 910 can report its capability to one or more duplexing technologies. For example, the capability information indicates the UE's 910 capability to perform UE-based TA estimation for any band operating in frequency division duplex (FDD) duplexing. Additionally or alternatively, the capability information indicates the UE's 910 capability to perform UE-based TA estimation for any band in time division duplex (TDD) duplexing.

[0108] In one example, the UE 910 can report its capability for one or more frequency bands. For example, the capability information indicates a capability of the UE 910 to perform UE-based TA estimation for any frequency band operating in the FR1 range. Additionally or alternatively, the capability information indicates a capability of the UE 910 to perform UE-based TA estimation for any frequency band in the FR2-1 range. Additionally or alternatively, the capability information indicates a capability of the UE 910 to perform UE-based TA estimation for any frequency band in the FR2-2 range.

[0109] Figure 10 An example of a command to correct UE-based TA estimation is illustrated in accordance with some embodiments. Generally, a UE can derive a TA for a cell as described herein above. The UE can then begin transmitting data (e.g., uplink data) to the cell with the timing of the data set based on the TA. The network (e.g., the cell or a DU or CU) can determine that a TA correction is needed. For example, timing measurements can be performed on uplink frames to determine that a timing offset exceeds an expected TA or timing threshold. In another example, detection of uplink data can fail or an error rate of such detection can exceed a threshold. The network can then send a TA correction to the UE.

[0110] In one example, the UE-based TA estimation does not rely on a RACH procedure. In other words, the UE does not send a RACH message to obtain a TA from the network (instead, the UE derives the TA). Because there is no RACH message, the UE does not need to expect or monitor for a RAR response indicating the TA. However, upon detecting that a TA correction is needed, the network can send a RAR response (e.g., a RAR MAC CE) indicating the TA correction, and the UE can be configured to monitor for and detect such RAR responses. In another example, the network sends a TA MAC CE to the UE indicating the TA correction.

[0111] In one example, a MAC CE (such as a TA MAC CE) is used to indicate the TA correction. The MAC CE can have a wide range of corrections, similar to a RAR MAC CE used in a typical RACH procedure, where the MAC CE is sent independent of the RACH procedure and includes more than six bits for the correction (e.g., providing a range of (0-3846) Tc, by including 12 bits for the correction).

[0112] In one example, a RAR MAC CE is used, where the RAR MAC CE is transmitted independent of the RACH procedure. To enable such RACH-less use of the RAR MAC CE, the CE can include a specific identifier (e.g., a cell radio network temporary identifier (C-RNTI)). The UE can be configured (e.g., by the network or preprogrammed) to parse the RAR MAC CE. Upon detecting the RAR MAC CE with the specific identifier (e.g., a match between the identifier in the RAR MAC CE and an identifier stored by the UE), the UE can apply the TA adjustment indicated by the RAM MAC CE.

[0113] Figure 10 The two examples above are illustrated in connection with a MAC CE (e.g., a TA MAC CE with a wide range of RAR MAC CE or a RAR MAC CE used independent of the RACH procedure). The MAC CE includes a MAC CE type differentiation 1010 indicating a TA command type (e.g., usable for TA correction), a timing advance group (TAG) identifier (ID) 1020 (e.g., indicating a TA group to which the TA correction command applies), an extended range timing advance command 1030 (e.g., a bit field longer than six bits, such as a twelve bit field providing a wide correction range, such as (0-3846) Tc range in the case of 12 bits). The extended range timing advance command 1040 can be repeated. Further, the MAC CE can include a C-RNTI (not shown).

[0114] In one example, the UE performs a UE-based estimation and estimates a TA (e.g., based on the timing difference 302) and determines that the TA to be applied exceeds the UE’s capabilities. For example, the UE can need an amount of time to refine its transmit radio frequency chain for its connection with the target cell. The TA can not support the amount of time (e.g., by being smaller). In this case, the UE can follow the procedure for radio link failure recovery for LTMs.

[0115] For example, the UE can declare a radio link failure event. Following this, the UE can search for a suitable candidate cell. If the candidate cell meets the cell selection criteria and the candidate cell is an LTM cell, the UE can generate a message including a UE identification (e.g., C-RNTI, current PCI, ShortMac-l, etc.) and a new cause of the failure (e.g., LTM reconfiguration failure, radio link failure, etc.). The UE can further wait for a response and proceed as indicated by the response. In some instances, the UE can initiate a timer and respond according to whether a response message is received before the timer expires or whether no message is received when the timer expires.

[0116] In the radio link failure procedure, it is assumed that both the UE and the selected candidate cell are configured for LTM. In some embodiments, the UE is configured for LTM, however, the selected candidate cell is not configured for LTM. In this instance, the UE can take the legacy operation of RRC connection reestablishment to establish a connection with the selected candidate cell. An example of the radio link failure procedure is described in WO Patent Application No. PCT / CN2023 / 075637, filed on February 13, 2023, for “RADIO LINK FAILURE AND HANDOVER FAILURE IN LAYER 1 / LAYER 2 MOBILITY,” the contents of which are incorporated herein by reference in their entirety.

[0117] Figure 11 An example of an operational flow / algorithm structure implemented by a UE to perform UE-based TA estimation is illustrated in accordance with some embodiments. The UE is an example of any of the UEs described in the present disclosure.

[0118] The operational flow / algorithm structure 1100 can include establishing a first connection with a first cell of a plurality of cells, at 1102. For example, the first cell is a serving cell provided by a base station DU. The connection can be established using an RRC establishment procedure, an RRC reconnection procedure, or a handover procedure.

[0119] The operational flow / algorithm structure 1100 can include determining that a second cell of the plurality of cells is a candidate cell for UE-based timing advance (TA) estimation, at 1104. For example, the second cell is a neighboring cell provided by the same base station DU, a different base station DU, or a base station CU. The determination can be based on RRC configuration information including a UE-based TA estimation indication. The indication can be part of a cell configuration of the second cell, a group configuration including a group of cells including at least the second cell, and / or a measurement configuration.

[0120] The operational flow / algorithm structure 1100 can include performing a timing measurement using a reference signal of the second cell based on the second cell being the candidate cell, at 1106. For example, based on a cell selection criterion, the UE detects the second cell (e.g., by being a neighboring cell of the serving cell) but has not established a connection with it (e.g., by being in a connected mode with it). The reference signal can be a SSB or a CSI-RS transmitted in a downlink frame of the second cell.

[0121] The operational flow / algorithmic structure 1100 can include receiving, at 1108, a command to establish a second connection with a second cell. For example, the command can include a MAC CE handover command and / or a MAC CE LTM handover. The command can indicate the second cell and can explicitly or implicitly trigger a computation of a timing difference based on time measurements (and similar time measurements of reference signals of the first cell), and a computation of a second TA based on a first TA of the first cell and the timing difference, for use in association with uplink transmissions to the second cell. The command can trigger any one or a combination of the computation of the timing difference, the computation of the TA, or the application of the TA for uplink transmissions.

[0122] The operational flow / algorithmic structure 1100 can include performing, at 1110, UE-based TA estimation by determining, at least after receiving the command and based on a first TA of the first cell and timing measurements, a second TA of the second cell. For example, after receiving the command, the second TA is computed as described in Figure 3 The UE can also establish the second connection with the second cell in response to the command (e.g., by using a handover procedure), and can use the second TA for uplink transmissions over the connection.

[0123] Figure 12 An example of an operational flow / algorithmic structure for triggering UE-based TA estimation implemented by a network is illustrated in accordance with some embodiments. The network is an example of any of the networks described in this disclosure.

[0124] The operational flow / algorithmic structure 1200 can include establishing, at 1202, a first connection with a user equipment (UE) via a first cell of a plurality of cells. For example, the first cell is a serving cell provided by a base station DU. The connection can be established using an RRC establishment procedure, an RRC reconnection procedure, or a handover procedure.

[0125] The operational flow / algorithmic structure 1200 can include determining, at 1204, that a second cell of the plurality of cells is a candidate cell for UE-based timing advance (TA) estimation. For example, the UE can have transmitted capability information to the network, where the capability information indicates support for UE-based TA estimation by the UE. The network can also determine that the second cell is tightly synchronized with the first cell, such that upon a handover from the first cell, the second cell can be allowed to perform UE-based TA estimation.

[0126] The operational flow / algorithmic structure 1200 can include transmitting, to the UE, a command to establish a second connection with a second cell, at 1206. For example, the command can include a MAC CE handover command and / or a MAC CE LTM handover. The command can indicate the second cell and can explicitly or implicitly trigger a computation of a timing difference based on time measurements (and similar time measurements of reference signals of the first cell) and a computation of a second TA based on a first TA of the first cell and the timing difference for use in association with uplink transmissions to the second cell. The command can trigger any one or a combination of the computation of the timing difference, the computation of the TA, or the application of the TA for uplink transmissions.

[0127] The operational flow / algorithmic structure 1200 can include forgoing transmitting, to the UE, a network-based TA to be used for the second connection based on the second cell being a candidate cell, at 1208. For example, because the UE supports UE-based TA estimation and the second cell is a candidate cell, the network can determine that there is no need to transmit a TA to the UE. Instead, the network can assume that the UE can derive a TA for uplink transmissions by the UE to the second cell.

[0128] The operational flow / algorithmic structure 1200 can include establishing, via the second cell, the second connection with the UE, at 1210. For example, the connection is established in response to the command (e.g., by using a handover procedure).

[0129] The operational flow / algorithmic structure 1200 can include receiving, from the UE, data over the second connection, the data being associated with a TA determined by the UE based on UE-based TA estimation, at 1212. For example, the data is received in uplink frames transmitted by the UE over the second connection. The timing of the uplink frames can depend on the TA determined by the UE. As needed, the network can subsequently transmit a command to the UE to correct the TA.

[0130] Figure 13 A receive component 1300, e.g., of a UE or base station, is illustrated in accordance with some embodiments. The receive component 1300 can include an antenna panel 1304 that includes a plurality of antenna elements. The panel 1304 is shown as having four antenna elements, but other embodiments can include other numbers of antenna elements.

[0131] The antenna panel 1304 can be coupled to an analog beamforming (BF) component that includes a plurality of phase shifters 1308(1) through 1308(4). The phase shifters 1308(1) through 1308(4) can be coupled with a radio frequency (RF) chain 1312. The RF chain 1312 can amplify a received analog RF signal, down-convert the RF signal to baseband, and convert the analog baseband signal to a digital baseband signal that can be provided to a baseband processor for further processing.

[0132] In various embodiments, control circuitry, which can reside in a baseband processor, can provide the BF weights (e.g., W1-W4) to the phase shifters 1308(1)-(4), which can represent phase shift values to provide a receive beam at the antenna panel 1304. The BF weights can be determined according to channel-based beamforming.

[0133] Figure 14 A UE 1400 according to some embodiments is illustrated. The UE 1400 can be similar to and substantially interchangeable with any of the UEs described above herein.

[0134] Similar to the description above with respect to the UE 144, the UE 1400 can be any mobile or non-mobile computing device, such as a mobile phone, a computer, a tablet, an industrial wireless sensor (e.g., a microphone, a carbon dioxide sensor, a pressure sensor, a humidity sensor, a thermometer, a motion sensor, an accelerometer, a laser scanner, a fluid level sensor, an inventory sensor, a voltage / current meter, an actuator, etc.), a video surveillance / monitoring device (e.g., a camera, a video camera, etc.), a wearable device, or a loose IoT device. In some embodiments, the UE can be a capacity reduced UE or a NR light UE.

[0135] The UE 1400 can include a processor 1404, RF interface circuitry 1408, memory / storage 1412, a user interface 1416, sensors 1420, drive circuitry 1422, a power management integrated circuit (PMIC) 1424, and a battery 1428. The components of the UE 1400 can be implemented as integrated circuits (ICs), portions of ICs, discrete electronic devices, or other modules, logic components, hardware, software, firmware, or a combination thereof. Figure 14 The block diagram of FIG. 14 is intended to show a high-level view of some of the components of the UE 1400. However, some of the components shown can be omitted in some embodiments, additional components can be present, and different arrangements of the components shown can occur in other embodiments.

[0136] The components of the UE 1400 can be coupled through one or more interconnects 1432, which can represent any type of interface, input / output, bus (local, system, or expansion), transmission line, trace, optical connection, etc. that allows various circuit components (on common or different chips or chip sets) to interact with one another.

[0137] The processor 1404 can include processor circuitry such as baseband processor circuitry (BB) 1404A, central processor unit circuitry (CPU) 1404B, and graphics processor unit circuitry (GPU) 1404C. The processor 1404 can include any type of circuit or processor circuitry for executing computer executable instructions such as program code, software modules, or functions processes from the memory / storage 1412 to cause the UE 1400 to perform operations as described herein.

[0138] In some embodiments, the baseband processor circuitry 1404A can access a communication protocol stack 1436 in the memory / storage 1412 for communicating over a 3GPP compatible network. Generally, the baseband processor circuitry 1404A can access the communication protocol stack to perform user plane functions at the PHY layer, MAC layer, RLC layer, PDCP layer, SDAP layer, and PDU layer; and control plane functions at the PHY layer, MAC layer, RLC layer, PDCP layer, RRC layer, and non-access stratum (NAS) layer. In some embodiments, PHY layer operations can additionally / alternatively be performed by components of the RF interface circuitry 1408.

[0139] The baseband processor circuitry 1404A can generate or process baseband signals or waveforms that carry information which is conveyed to or from the 3GPP compatible network. In some embodiments, waveforms for NR can be based on cyclic prefix OFDM (CP-OFDM) in the uplink or downlink, and discrete Fourier transform spread OFDM (DFT-S-OFDM) in the uplink.

[0140] The baseband processor circuitry 1404A can also access group information from the memory / storage 1412 to determine search space groups in which multiple repetitions of a PDCCH can be transmitted.

[0141] The memory / storage 1412 can include any type of volatile or nonvolatile memory that can be distributed throughout the UE 1400. In some embodiments, some of the memory / storage 1412 can reside on the processor 1404 itself (e.g., L1 cache and L2 cache) while other memory / storage 1412 resides outside of the processor 1404 but can be accessible via a memory interface. The memory / storage 1412 can include any suitable type of volatile or non-volatile memory, such as, but not limited to, dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory, or any other type of memory device technology.

[0142] The RF interface circuitry 1408 can include transceiver circuitry and radio frequency front module (RFEM) that allows the UE 1400 to communicate with other devices over the air interface of a network. The RF interface circuitry 1408 can include various elements arranged in transmit or receive paths. These elements can include, for example, switches, mixers, amplifiers, filters, synthesizer circuitry, control circuitry, etc.

[0143] In the receive path, the RFEM can receive a radiated signal from the air interface via the antenna 1450 and continue to filter and amplify (with a low noise amplifier) the signal. The signal can be provided to a receiver of the transceiver that down-converts the RF signal to a baseband signal that is provided to the baseband processor of the processor 1404.

[0144] In the transmit path, a transmitter of the transceiver up-converts baseband signals, received from the baseband processor, and provides RF signals that are amplified by a power amplifier of the RFEM before they are radiated across the air interface via the antenna 1450.

[0145] In various embodiments, the RF interface circuitry 1408 can be configured to transmit / receive signals in a manner compatible with NR access technology.

[0146] The antenna 1450 can include multiple antenna elements that each convert electrical signals to and from radio waves to travel through the air and be received as signals. These antenna elements can be arranged in one or more antenna panels. The antenna 1450 can have an antenna panel that is omnidirectional, directional, or a combination thereof to enable beamforming and multiple-input, multiple-output communication. The antenna 1450 can include microstrip antennas, printed antennas fabricated on the surface of one or more printed circuit boards, patch antennas, phased array antennas, etc. The antenna 1450 can have one or more panels designed for a particular frequency band including the frequency bands in FR1 or FR2.

[0147] The user interface circuitry 1416 includes various input / output (I / O) devices that allow a user to interact with the UE 1400. User interface 1416 includes input device circuitry and output device circuitry. Input device circuitry includes any physical or virtual means for entering or providing input to the UE 1400. Output device circuitry includes any physical or virtual means for outputting or providing information from the UE 1400.

[0148] The sensors 1420 can include devices, modules, or subsystems whose purpose is to detect events or changes in its environment and send the information (sensor data) about the detected events to some other device, module, subsystem, etc. Examples of such sensors include, inter alia, inertial measurement units comprising accelerometers, gyroscopes, or magnetometers; microelectromechanical systems or nanoelectromechanical systems including three-axis accelerometers, three-axis gyroscopes, or magnetometers; liquid level sensors; flow sensors; temperature sensors (e.g., thermistors); pressure sensors; barometric sensors; gravimeters; altimeters; image capture devices (e.g., cameras or lensless apertures); light detection and ranging sensors; proximity sensors (e.g., infrared radiation detectors, etc.); depth sensors; ambient light sensors; ultrasonic transceivers; microphones or other like audio capture devices; etc.

[0149] The drive circuitry 1422 can include software and hardware elements that operate to control particular devices embedded in, or attached to, or otherwise part of the UE 1400. The drive circuitry 1422 can include individual drivers that allow other components to interact with or control various input / output (I / O) devices that can be present in, or connected to, the UE 1400. For example, the drive circuitry 1422 can include a display driver to control and allow access to a display device, a touchscreen driver to control and allow access to a touchscreen interface, sensor drivers to obtain sensor readings from sensor circuitry 1420 and control and allow access to the sensor circuitry 1420, a driver to obtain actuator positions of electromechanical components or to control and allow access to electromechanical components, a camera driver to control and allow access to an embedded image capture device, and an audio driver to control and allow access to one or more audio devices.

[0150] The PMIC 1424 can manage power provided to the various components of the UE 1400. In particular, with respect to the processor 1404, the PMIC 1424 can control power source selection, voltage scaling, battery charging, or DC-to-DC conversion.

[0151] In some embodiments, the PMIC 1424 can control, or otherwise be part of, various power saving mechanisms of the UE 1400. For example, if the platform UE is in an RRC_Connected state, in which it is still connected to a RAN node as it expects to receive traffic shortly, then the platform UE can enter a state known as Discontinuous Reception (DRX) in which it periodically powers down for a time, to conserve power. If there is no data traffic for an extended period of time, then the UE 1400 can transition off to an RRC_Idle state where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The UE 1400 goes into a very low power state and it performs paging where again it periodically wakes up to listen to the network and then powers down again. The UE 1400 can not receive data in this state; in order to receive data, it must transition back to RRC_Connected state. An additional power saving mode can be sleep, where the device is unavailable to the network for periods longer than the paging interval (from seconds to hours). In this period, the device is completely powered off and it cannot be reached. Any data sent to it will cause a large delay and it is assumed that the delay is acceptable.

[0152] The battery 1428 can power the UE 1400, although in some examples the UE 1400 can be installed in a fixed location, and can have a power supply coupled to an electrical grid. The battery 1428 can be a lithium ion battery, a metal-air battery (such as a zinc-air battery, an aluminum-air battery, a lithium-air battery, and so forth). In some examples, such as in vehicle-based applications, the battery 1428 can be a typical lead-acid automotive battery.

[0153] Figure 15 A gNB 1500 according to some embodiments is illustrated. The gNB 1500 can be similar to and substantially inter changeable with any of the base stations described above herein.

[0154] The gNB 1500 can include a processor 1504, RAN interface circuitry 1508, core network (CN) interface circuitry 1512, and memory / storage circuitry 1516.

[0155] The components of the gNB 1500 can be coupled with various other components over one or more interconnects 1528.

[0156] The processor 1504, RAN interface circuitry 1508, memory / storage circuitry 1516 (including communication protocol stack 1510), antenna 1550, and interconnect 1528 can be similar to those described above with respect to Figure 14

[0157] The CN interface circuitry 1512 can provide connectivity to a core network (e.g., a Fifth Generation Core Network (5GC) using Fifth Generation Core Network (5GC) compatible network interface protocols such as carrier Ethernet protocols or some other suitable protocol). Network connectivity can be provided to / from the gNB 1500 via fiber or wireless backhaul. The CN interface circuitry 1512 can include one or more specialized processors or FPGAs for communicating using one or more of the aforementioned protocols. In some implementations, the CN interface circuitry 1512 can include multiple controllers for providing connectivity to other networks using the same or different protocols.

[0158] It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled in a way to minimize risk of unintentional or unauthorized access or use, and the nature of authorization should be clearly expressed to the users.

[0159] ​For one or more embodiments, at least one of the components illustrated in one or more of the preceding figures can be configured to perform one or more operations, techniques, procedures, or methods set forth in the following EMBODIMENT SECTIONS. For example, the baseband circuitry described above in connection with one or more of the preceding figures can be configured to operate in accordance with one or more of the following embodiments. For another example, circuitry associated with a UE, base station, network element, etc., described above in connection with one or more of the preceding figures can be configured to operate in accordance with one or more of the embodiments set forth in the following EMBODIMENT SECTIONS.

[0160] It is well understood that, where personally identifiable information is used, it is to be handled in a manner that is consistent with privacy policy and practices that are generally recognized as meeting or exceeding industry or governmental requirements for privacy. Specifically, personally identifiable information should be managed and handled in a manner that minimizes risk of unintentional or unauthorized access or use, and that is in compliance with privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for privacy.

[0161] For one or more embodiments, at least one of the components illustrated in one or more of the preceding figures can be configured to perform one or more operations, techniques, procedures, or methods set forth in the following EMBODIMENT SECTIONS. For example, the baseband circuitry described above in connection with one or more of the preceding figures can be configured to operate in accordance with one or more of the following embodiments. For another example, circuitry associated with a UE, base station, network element, etc., described above in connection with one or more of the preceding figures can be configured to operate in accordance with one or more of the embodiments set forth in the following EMBODIMENT SECTIONS.

[0162] Example

[0163] In the following sections, additional example embodiments are provided.

[0164] Example 1 includes a method implemented by a user equipment (UE), the method comprising: establishing a first connection with a first cell of a plurality of cells; determining that a second cell of the plurality of cells is a candidate cell for a UE-based timing advance (TA) estimation; performing a timing measurement using a reference signal of the second cell based on the second cell being the candidate cell; receiving a command to establish a second connection with the second cell; and performing the UE-based TA estimation by determining a second TA of the second cell based on a first TA of the first cell and the timing measurement at least after receiving the command.

[0165] Example 2 includes the method of Example 1, wherein the timing measurement is performed prior to receiving the command.

[0166] Example 3 includes the method of any of Examples 1-2, further comprising receiving a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells to be considered candidate cells for the UE-based TA estimation, wherein the set includes the second cell.

[0167] Example 4 includes the method of any of Examples 1-3, further comprising receiving a radio resource control (RRC) configuration indicating a cell configuration for the second cell, wherein the cell configuration indicates that the UE-based TA estimation is allowed for the second cell.

[0168] Example 5 includes the method of Example 4, wherein the RRC configuration indicates another cell configuration for a third cell of the plurality of cells, wherein the another cell configuration indicates that the UE-based TA estimation is not allowed for the third cell.

[0169] Example 6 includes the method of any of Examples 1-5, further comprising receiving a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells and that the UE-based TA estimation is allowed for the set; and determining that the second cell belongs to the set of cells.

[0170] Example 7 includes the method of any of Examples 1-6, further comprising receiving a cell configuration and a measurement configuration, wherein the cell configuration indicates a configuration of the second cell, and wherein the measurement configuration is separate from the cell configuration and indicates that the UE-based TA estimation is allowed for the second cell.

[0171] Example 8 includes the method of Example 7, wherein the cell configuration is received from the first cell.

[0172] Example 9 includes the method of Example 7, wherein the cell configuration is a radio resource control (RRC) independent of reception of the first cell and the second cell.

[0173] Example 10 includes the method of any of Examples 1-9, wherein the command includes a medium access control (MAC) control element (CE) associated with a handover to the second cell, wherein the MAC CE indicates the second cell and a trigger for the UE-based TA estimation.

[0174] Example 11 includes the method of any of Examples 1-10, wherein the command includes a layer 1 / layer 2 triggered mobility (LTM) handover indicating the second cell and a trigger for the UE-based TA estimation.

[0175] Example 12 includes the method of any of Examples 1-11, wherein the command comprises a medium access control (MAC) control element (CE) and a layer 1 / layer 2 triggered mobility (LTM) handover associated with a handover to the second cell, wherein the MAC CE indicates a trigger for the UE-based TA estimation, and wherein the LTM handover indicates that the second TA is to be used for communication over the second connection.

[0176] Example 13 includes the method of any of Examples 1-12, further comprising sending capability information to a network indicating that the UE is capable of performing the UE-based TA estimation based on measurements of reference signals of a target cell.

[0177] Example 14 includes the method of Example 13, wherein the command is received from the network based on the capability information and indicates a trigger for performing the UE-based TA estimation.

[0178] Example 15 includes the method of Example 13, wherein the capability information indicates that the UE is capable of performing the measurements and deriving a timing difference between two cells independent of whether the two cells use a same frequency.

[0179] Example 16 includes the method of any of Examples 14-15, wherein the capability information indicates an intra-frequency capability of the UE to perform the UE-based TA estimation for all target cells that use a same frequency as a serving cell.

[0180] Example 17 includes the method of any of Examples 14-16, wherein the capability information indicates an intra-band capability of the UE to perform the UE-based TA estimation for all target cells that use a same band as a serving cell.

[0181] Example 18 includes the method of any of Examples 14-17, wherein the capability information indicates a capability of the UE to perform the UE-based TA estimation for any band operating in frequency division duplex (FDD) duplexing or in time division duplex (TDD) duplexing.

[0182] Example 19 includes the method of any of Examples 14-18, wherein the capability information indicates a capability of the UE to perform the UE-based TA estimation for any band operating in a FR1 range, any band in a FR2-1 range, or any band in a FR2-2 range.

[0183] Example 20 includes the method of any of Examples 14-19, wherein the capability information indicates a band combination capability of the UE to perform the UE-based TA estimation for a band combination.

[0184] Example 21 includes the method of any of Examples 14-20, wherein the capability information indicates a per-band combination capability of the UE to perform the UE-based TA estimation for all target cells that use a band combination as a serving cell.

[0185] Example 22 includes the method of any of Examples 14-21, wherein the capability information indicates a maximum number of cells for which the UE is capable of performing reference signal measurements.

[0186] Example 23 includes the method of any of Examples 14-22, wherein the capability information indicates a maximum number of frequencies for which the UE is capable of performing reference signal measurements.

[0187] Example 24 includes the method of any of Examples 1-23, further comprising: receiving a medium access control (MAC) control element (CE) that uses more than six bits to indicate a TA correction; and updating the second TA based on the TA correction.

[0188] Example 25 includes the method of any of Examples 1-24, further comprising: receiving a random access response (RAR) medium access control (MAC) control element (CE) that indicates a TA correction, wherein the RAR MAC CE is received independent of a random access channel (RACH) procedure; and updating the second TA based on the TA correction.

[0189] Example 26 includes the method of any of Examples 1-25, further comprising: determining that the second TA is outside of a capability of the UE; and initiating a link recovery facility for layer 1 / layer 2 triggered mobility (LTM).

[0190] Example 27 includes a method implemented by a network, the method comprising: establishing a first connection with a user equipment (UE) via a first cell of a plurality of cells; determining that a second cell of the plurality of cells is a candidate cell for UE-based timing advance (TA) estimation; sending a command to the UE to establish a second connection with the second cell; forgoing sending a network-based TA to be used for the second connection based on the second cell being a candidate cell; establishing the second connection with the UE via the second cell; and receiving data from the UE over the second connection, the data being associated with a TA determined by the UE based on the UE-based TA estimation.

[0191] Example 28 includes the method of Example 27, further comprising transmitting, to the UE, a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells to be considered candidate cells for the UE-based TA estimation, wherein the set includes the second cell.

[0192] Example 29 includes the method of any of Examples 27-28, further comprising transmitting, to the UE, a radio resource control (RRC) configuration indicating a cell configuration for the second cell, wherein the cell configuration indicates that the UE-based TA estimation is allowed for the second cell.

[0193] Example 30 includes the method of any of Examples 27-29, further comprising transmitting, to the UE, a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells and that the UE-based TA estimation is allowed for the set, wherein the second cell belongs to the set of cells.

[0194] Example 31 includes the method of any of Examples 27-30, further comprising transmitting, to the UE, a cell configuration and a measurement configuration, wherein the cell configuration indicates a configuration of the second cell, and wherein the measurement configuration is separate from the cell configuration and indicates that the UE-based TA estimation is allowed for the second cell.

[0195] Example 32 includes the method of any of Examples 27-31, further comprising generating the command based on the determining that the second cell is a candidate cell, wherein the command includes a medium access control (MAC) control element (CE) associated with a handover to the second cell, and wherein the MAC CE indicates the second cell and a trigger for the UE-based TA estimation.

[0196] Example 33 includes the method of any of Examples 27-32, wherein the command includes either first a layer 1 / layer 2 triggered mobility (LTM) handover indicating the second cell and a first trigger for the UE-based TA estimation, or a medium access control (MAC) control element (CE) associated with a handover to the second cell and a second LTM handover, wherein the MAC CE indicates a second trigger for the UE-based TA estimation, and wherein the second LTM handover indicates that the TA is to be used for communicating over the second connection.

[0197] Example 34 includes the method of any of Examples 27-33, further comprising receiving, from the UE, capability information indicating that the UE is capable of performing the UE-based TA estimation based on measurements of reference signals of a target cell, wherein the command is transmitted based on the capability information and indicates a trigger for performing the UE-based TA estimation.

[0198] Example 35 includes the method of any of Examples 27-34, further comprising transmitting, to the UE, a medium access control (MAC) control element (CE) that uses more than six bits to indicate a TA correction.

[0199] Example 36 includes the method of any of Examples 27-35, further comprising transmitting, to the UE, a random access response (RAR) medium access control (MAC) control element (CE) that indicates a TA correction, wherein the RAR MAC CE is transmitted independent of a random access channel (RACH) procedure.

[0200] Example 37 includes an apparatus comprising means for performing one or more elements of a method described in or related to any of Examples 1-36.

[0201] Example 38 includes one or more non-transitory computer-readable media comprising instructions to cause a device, upon execution of the instructions by one or more processors of the device, to perform one or more elements of a method described in or related to any of Examples 1-36.

[0202] Example 39 includes an apparatus comprising logic, modules, or circuitry to perform one or more elements of a method described in or related to any of Examples 1-36.

[0203] Example 40 includes an apparatus comprising one or more processors and one or more computer-readable media comprising instructions to cause the one or more processors, upon execution of the instructions, to perform one or more elements of a method described in or related to any of Examples 1-36.

[0204] Example 41 includes a system comprising means for performing one or more elements of a method described in or related to any of Examples 1-36.

[0205] Example 42 includes a network comprising means for performing one or more elements of a method described in or related to any of Examples 1-36.

[0206] Example 43 includes one or more non-transitory computer-readable media comprising instructions to cause a network, upon execution of the instructions by one or more processors of the network, to perform one or more elements of the method in accordance with or related to any of examples 1-36.

[0207] Example 44 includes a network comprising logic, modules, or circuitry to perform one or more elements of the method in accordance with or related to any of examples 1-36.

[0208] Example 45 includes a network comprising one or more processors and one or more computer-readable media comprising instructions to cause the one or more processors, upon execution of the instructions, to perform one or more elements of the method in accordance with or related to any of examples 1-36.

[0209] Any of the above examples can be combined with any other example (or combination of examples), unless otherwise expressly stated. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of implementations to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of various implementations. No aspect of any implementation is intended to be dedicated to or be in the public domain.

[0210] Any of the above examples can be combined with any other example (or combination of examples), unless otherwise expressly stated. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of implementations to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of various implementations. No aspect of any implementation is intended to be dedicated to or be in the public domain.

[0211] While the above implementations have been described with some detail, once armed with the above disclosure many variations and modifications will become apparent to those skilled in the art. It is intended that the following claims be construed to include all such variations and modifications as falling within the scope of the disclosure.

Claims

1. A method implemented by a user equipment (UE), the method comprising: establishing a first connection with a first cell of a plurality of cells; determining that a second cell of the plurality of cells is a candidate cell for a UE-based timing advance (TA) estimation; performing a timing measurement using a reference signal of the second cell based on the second cell being a candidate cell; receiving a command to establish a second connection with the second cell; and performing the UE-based TA estimation by determining a second TA of the second cell based on a first TA of the first cell and the timing measurement at least after receiving the command.

2. The method of claim 1, wherein the timing measurement is performed before receiving the command.

3. The method of claim 1, further comprising: receiving a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells to be considered candidate cells for the UE-based TA estimation, wherein the set includes the second cell.

4. The method of claim 1, further comprising: receiving a radio resource control (RRC) configuration indicating a cell configuration for the second cell, wherein the cell configuration indicates that the UE-based TA estimation is allowed for the second cell.

5. The method of claim 4, wherein the RRC configuration indicates another cell configuration for a third cell of the plurality of cells, wherein the other cell configuration indicates that the UE-based TA estimation is not allowed for the third cell.

6. The method of claim 1, further comprising: receiving a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells and allowing the UE-based TA estimation for the set; and determining that the second cell belongs to the set of cells.

7. The method of claim 1, further comprising: receiving a cell configuration and a measurement configuration, wherein the cell configuration indicates a configuration of the second cell, and wherein the measurement configuration is separate from the cell configuration and indicates that the UE-based TA estimation is allowed for the second cell.

8. The method of claim 7, wherein the cell configuration is received from the first cell.

9. The method of claim 7, wherein the cell configuration is a received radio resource control (RRC) independent of the first cell and the second cell.

10. A user equipment (UE), the UE comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, configure the UE to: establish a first connection with a first cell of a plurality of cells; determine that a second cell of the plurality of cells is a candidate cell for a UE-based timing advance (TA) estimation; perform a timing measurement using a reference signal of the second cell based on the second cell being a candidate cell; ​ ​ receive a command to establish a second connection with the second cell; and perform the UE-based TA estimation by determining a second TA of the second cell based at least on the first TA of the first cell and the timing measurement after receiving the command.

11. The UE of claim 10, wherein the command comprises a medium access control (MAC) control element (CE) associated with a handover to the second cell, wherein the MAC CE indicates the second cell and a trigger for the UE-based TA estimation.

12. The UE of claim 10, wherein the command comprises a layer 1 / layer 2 triggered mobility (LTM) handover that indicates the second cell and a trigger for the UE-based TA estimation.

13. The UE of claim 10, wherein the command comprises a medium access control (MAC) control element (CE) associated with a handover to the second cell and a layer 1 / layer 2 triggered mobility (LTM) handover, wherein the MAC CE indicates a trigger for the UE-based TA estimation, and wherein the LTM handover indicates that the second TA is to be used for communication over the second connection.

14. The UE of claim 10, wherein the execution of the instructions further configures the UE to: send capability information to a network indicating that the UE is capable of performing the UE-based TA estimation based on measurements of reference signals of a target cell.

15. The UE of claim 14, wherein the command is received from the network based on the capability information and indicates a trigger for performing the UE-based TA estimation.

16. The UE of claim 14, wherein the capability information indicates that the UE is capable of performing the measurements and deriving a timing difference between two cells independent of whether the two cells use a same frequency.

17. The UE of claim 14, wherein the capability information indicates an intra- frequency capability of the UE to perform the UE-based TA estimation for all target cells that use a same frequency as a serving cell.

18. The UE of claim 14, wherein the capability information indicates an intra- band capability of the UE to perform the UE-based TA estimation for all target cells that use a same frequency band as a serving cell.

19. The UE of claim 14, wherein the capability information indicates a capability of the UE to perform the UE-based TA estimation for any frequency band operating in a frequency division duplex (FDD) duplexing manner or in a time division duplex (TDD) duplexing manner.

20. The UE of claim 14, wherein the capability information indicates a capability of the UE to perform the UE-based TA estimation for any frequency band operating in a FR1 range, any frequency band in a FR2-1 range, or any frequency band in a FR2-2 range.

21. The UE of claim 14, wherein the capability information indicates a frequency band combination capability of the UE to perform the UE-based TA estimation for a frequency band combination.

22. The UE of claim 14, wherein the capability information indicates a per-band combination capability of the UE to perform the UE-based TA estimation for all target cells using a band combination as a serving cell.

23. The UE of claim 14, wherein the capability information indicates a maximum number of cells for which the UE can perform reference signal measurements.

24. The UE of claim 14, wherein the capability information indicates a maximum number of frequencies for which the UE can perform reference signal measurements.

25. The UE of claim 10, wherein the execution of the instructions further configure the UE to: receive a medium access control (MAC) control element (CE) that uses more than six bits to indicate a TA correction; and update the second TA based on the TA correction.

26. The UE of claim 10, wherein the execution of the instructions further configure the UE to: receive a random access response (RAR) medium access control (MAC) control element (CE) that indicates a TA correction, wherein the RAR MAC CE is received independent of a random access channel (RACH) procedure; and update the second TA based on the TA correction.

27. The UE of claim 10, wherein the execution of the instructions further configure the UE to: determine that the second TA exceeds a capability of the UE; and initiate a link recovery facility for layer 1 / layer 2 triggered mobility (LTM).

28. A method implemented by a network, the method comprising: establishing a first connection with a user equipment (UE) via a first cell of a plurality of cells; determining that a second cell of the plurality of cells is a candidate cell for UE-based timing advance (TA) estimation; sending a command to the UE to establish a second connection with the second cell; abandoning sending a network-based TA to be used for the second connection based on the second cell being a candidate cell; establishing the second connection with the UE via the second cell; and receiving data from the UE over the second connection, the data being associated with a TA determined by the UE based on the UE-based TA estimation.

29. The method of claim 28, further comprising: sending a radio resource control (RRC) configuration to the UE, the RRC configuration indicating a set of cells of the plurality of cells to be considered candidate cells for the UE-based TA estimation, wherein the set includes the second cell.

30. The method of claim 28, further comprising: sending a radio resource control (RRC) configuration to the UE indicating a cell configuration for the second cell, wherein the cell configuration indicates that the UE-based TA estimation is allowed for the second cell.

31. The method of claim 28, further comprising: ​ ​ ​ ​ ​ ​ ​ ​ transmitting, to the UE, a radio resource control (RRC) configuration indicating a set of cells of the plurality of cells and allowing the UE-based TA estimation for the set, wherein the second cell belongs to the set of cells.

32. The method of claim 28, further comprising: transmitting, to the UE, a cell configuration and a measurement configuration, wherein the cell configuration indicates a configuration of the second cell, and wherein the measurement configuration is separate from the cell configuration and indicates that the UE-based TA estimation is allowed for the second cell.

33. The method of claim 28, further comprising: generating the command based on determining that the second cell is a candidate cell, wherein the command comprises a medium access control (MAC) control element (CE) associated with a handover to the second cell, and wherein the MAC CE indicates the second cell and a trigger for the UE-based TA estimation.

34. The method of claim 28, wherein the command comprises: a layer 1 / layer 2 triggered mobility (LTM) handover indicating the second cell and a first trigger for the UE-based TA estimation, or a medium access control (MAC) control element (CE) associated with a handover to the second cell and a second LTM handover, wherein the MAC CE indicates a second trigger for the UE-based TA estimation, and wherein the second LTM handover indicates that the TA is to be used for communicating over the second connection.

35. The method of claim 28, further comprising: receiving, from the UE, capability information indicating that the UE is capable of performing the UE-based TA estimation based on measurements of reference signals of a target cell, wherein the command is transmitted based on the capability information and indicates a trigger for performing the UE-based TA estimation.

36. The method of claim 28, further comprising: transmitting, to the UE, a medium access control (MAC) control element (CE) that uses more than six bits to indicate a TA correction.

37. The method of claim 28, further comprising: transmitting, to the UE, a random access response (RAR) medium access control (MAC) control element (CE) indicating a TA correction, wherein the RAR MAC CE is transmitted independent of a random access channel (RACH) procedure.

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