WO2024008284A1

WO2024008284A1 - Rapid secondary cell (scell) reactivation by user equipment

Info

Publication number: WO2024008284A1
Application number: PCT/EP2022/068716
Authority: WO
Inventors: Andres Reial; Sina MALEKI; Ali Nader; Ilmiawan SHUBHI
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2024-01-11

Abstract

Embodiments include methods for a user equipment, (UE), configured to communicate with a radio access network, (RAN), via a primary serving cell, (PCell), and at least a first secondary cell, (SCell). Such methods include, while the first SCell is activated, deactivating the first SCell in response to receiving from a RAN node a first command to deactivate the first SCell. Such methods include subsequently receiving a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated, and synchronizing to the first SCell in response to the second command and without receiving any synchronization signals transmitted in the first SCell. In some embodiments, the methods include maintaining synchronization with the PCell while the first SCell is deactivated. Other embodiments include complementary methods for a RAN node, as well as UEs and RAN nodes configured to perform such methods.

Description

RAPID SECONDARY CELL (SCELL) REACTIVATION BY USER EQUIPMENT

TECHNICAL FIELD

The present disclosure relates generally to wireless networks, and more specifically to techniques for user equipment (UE) configured with a primary cell (PCell) and one or more secondary cells (SCells) to rapidly reactivate an SCell that has been deactivated.

BACKGROUND

Currently the fifth generation (“5G”) of cellular systems, also referred to as New Radio (NR), is being standardized within the Third-Generation Partnership Project (3GPP). NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device -to -device (D2D), and several other use cases. NR was initially specified in 3GPP Release 15 (Rel-15) and continues to evolve through subsequent releases, such as Rel-16 and Rel-17.

5G/NR technology shares many similarities with fourth-generation Long-Term Evolution (LTE). For example, NR uses CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) in the downlink (DL) from network to user equipment (UE), and both CP-OFDM and DFT-spread OFDM (DFT-S-OFDM) in the uplink (UL) from UE to network. As another example, NR DL and UL time- domain physical resources are organized into equal-sized 1-ms subframes. A subframe is further divided into multiple slots of equal duration, with each slot including multiple OFDM-based symbols. However, time-frequency resources can be configured much more flexibly for an NR cell than for an LTE cell. For example, rather than a fixed 15-kHz OFDM sub-carrier spacing (SCS) as in LTE, NR SCS can range from 15 to 240 kHz, with even greater SCS considered for future NR releases.

In addition to providing coverage via cells as in LTE, NR networks also provide coverage via “beams.” In general, a downlink (DL, i.e., network to UE) “beam” is a coverage area of a network- transmitted reference signal (RS) that may be measured or monitored by a UE. In NR, for example, RS can include any of the following: synchronization signal/ Physical Broadcast Channel (PBCH) block (SSB), channel state information RS (CSI-RS), tracking reference signals (or any other sync signal), positioning RS (PRS), demodulation RS (DMRS), phase-tracking reference signals (PTRS), etc. In general, SSB is available to all UEs regardless of the state of their connection with the network, while other RS (e.g., CSI-RS, DMRS, PTRS) are associated with specific UEs that have a network connection.

3GPP Rel-10 introduced support for channel bandwidths larger than 20 MHz in LTE, which continued into NR. To remain compatible with legacy UEs from earlier releases (e.g., LTE Rel-8), a wideband LTE Rel-10 carrier appears as multiple component carriers (CCs), each having the same structure as an LTE Rel-8 carrier. The Rel-10 UE can receive the multiple CCs based on Carrier Aggregation (CA). The CCs can also be considered “cells”, such that a UE in CA has one primary cell (PCell) and one or more secondary cells (SCells). These are referred to collectively as a “cell group”. NR includes support for CA in Rel-15 and subsequent releases. Nevertheless, CA involves tradeoffs between data throughput/latency (referred to collectively as “link performance”) and UE energy consumption. Link performance is best when a maximum number of available SCells are permanently activated and immediately available to the UE for data transmission/reception. Unfortunately, UE operations toward an activate SCell (e.g., DL control channel monitoring and measurements) cause significant UE energy consumption and, thus, are not feasible to be done over an extended duration when no data is being transmitted/received via the SCell.

Thus, a Radio Access Network (RAN) node that provides the UE’s cell group typically activates one or more of the SCells only when there is data traffic that can utilize the additional capacity provided by the SCell(s). When the traffic reduces to a level that can be handled by fewer SCells, the RAN node deactivates one or more of the UE’s SCells. For example, SCell activation, deactivation, and reactivation may be performed via PCell signaling (e.g., Medium Access Control (MAC) control elements (CEs)).

In NR Rel-15, SCell activation/reactivation time is quite long (e.g., at least 100 ms) due to time reserved for the UE to synchronize with and perform measurements on SSBs transmitted on the newly activated SCell. Since the UE cannot utilize the SCell during this latency period, SCell deactivation/reactivation has been conventionally used as a longer-term solution to deal with trends in data traffic - rather than to address dynamic UE data traffic requirements.

To reduce SCell activation latency, NR Rel-17 introduced a Fast SCell Activation feature. Upon transmitting the SCell activation command via the UE’s PCell, the RAN node also transmits one non-periodic tracking RS (TRS) on the SCell. As such, UEs that support this feature can synchronize to the SCell without waiting to receive SSB. For example, fast SCell activation latency is -20-40 ms.

SUMMARY

However, the NR Rel-17 Fast SCell Activation feature is not part of baseline CA operation and, as such, is not guaranteed to be supported by UE and RAN vendors. Moreover, the NR Rel-17 Fast SCell Activation feature still introduces a significant, undesirable SCell activation latency. To use dynamic SCell activation to address dynamic UE data traffic requirements, there is a need for a better solution with less latency.

Embodiments of the present disclosure provide specific improvements to dynamic SCell activation, such as by providing, enabling, and/or facilitating solutions to exemplary problems summarized above and described in more detail below.

Some embodiments include methods (e.g., procedures) for a UE configured to communicate with a RAN via a PCell and at least a first SCell.

These exemplary methods can include, while the first SCell is activated, deactivating the first SCell in response to receiving from a RAN node a first command to deactivate the first SCell. These exemplary methods can also include subsequently receiving a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated. These exemplary methods can also include synchronizing to the first SCell in response to the second command and without receiving any synchronization signals (e.g., SSB or TRS) transmitted in the first SCell. In some embodiments, these exemplary methods can also include maintaining synchronization with the PCell while the first SCell is deactivated. In such case, synchronizing to the first SCell without receiving any synchronization signals transmitted in the first SCell can include performing fine synchronization with the first SCell based on the synchronization maintained with the PCell while the first SCell was deactivated.

Other embodiments include methods (e.g., procedures) for a RAN node configured to provide a PCell and at least a first SCell to a UE.

These exemplary methods can include sending, to a UE, a configuration for measurement and reporting by the UE. The configuration identifies the following: radio resources on which RS are or will be transmitted by the RAN node, and a mapping of the identified radio resources to a plurality of RAN node antenna ports used to transmit the RS. For example, the RS can be CSI-RS and the RAN node antenna ports can be CSI-RS ports.

These exemplary methods can also include, while the first SCell is activated, sending to the UE a first command to deactivate the first SCell. These exemplary methods can also include subsequently sending a second command to activate the first SCell to the UE via the PCell or via a second SCell that is activated. These exemplary methods can also include, after sending the second command but before a next-scheduled transmission of a synchronization signal in the first SCell, transmitting one or more of the following information via the first SCell: a physical control channel carrying downlink control information intended for the UE; and a physical data channel carrying data intended for the UE.

In some embodiments, these exemplary methods can also include maintaining synchronization with the UE via PCell while the first SCell is deactivated. In such embodiments, transmitting the information before the next-scheduled transmission of the synchronization signal is based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated.

Other embodiments include UEs (e.g., wireless devices) and RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, etc., or components thereof) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer- readable media storing program instructions that, when executed by processing circuitry, configure such UEs and RAN nodes to perform operations corresponding to any of the exemplary methods described herein.

These and other embodiments described herein can beneficially reduce SCell activation latency by removing dependence on RAN node synchronization signal transmission schedules. Instead, SCell activation latency is now dependent only on latency of UE receiver state change, which is ~3-5 ms when exiting light sleep or ~20 ms when exiting deep sleep. Accordingly, embodiments advantageously increase utility of dynamic SCell deactivation for UE energy consumption management as well as utilization of SCells for dynamic UE data capacity.

These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below. BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1-2 show exemplary high-level views of 5G/NR network architecture

Figure 3 shows an exemplary configuration of 5G/NR user plane (UP) and control plane (CP) protocol layers.

Figure 4 shows an exemplary time-frequency resource grid for an NR slot.

Figures 5-7 show exemplary NR synchronization signal/PBCH block (SSB) arrangements.

Figure 8 shows a conventional SCell activation procedure and associated UE energy consumption.

Figure 9 shows an SCell activation procedure and associated UE energy consumption, according to embodiments of the present disclosure.

Figures 10A-B show a flow diagram of an exemplary method (e.g., procedure) for a UE (e.g., wireless device), according to various embodiments of the present disclosure.

Figure 11 shows a flow diagram of an exemplary method (e.g., procedure) for a RAN node (e.g., base station, eNB, gNB, ng-eNB, etc.), according to various embodiments of the present disclosure.

Figure 12 shows a communication system according to various embodiments of the present disclosure.

Figure 13 shows a UE according to various embodiments of the present disclosure.

Figure 14 shows a network node according to various embodiments of the present disclosure.

Figure 15 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where a step must necessarily follow or precede another step due to some dependency. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will be apparent from the following description.

Furthermore, the following terms are used throughout the description given below: • Radio Node: As used herein, a “radio node” can be either a radio access node or a wireless device.”

• Node: As used herein, a “node” can be a network node or a wireless device.

• Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (RAN node) in a 3GPP Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low-power base station (e.g., micro, pico, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point, a remote radio unit/head (RRU or RRH), and a relay node.

• Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), a Packet Data Network Gateway (P-GW), an access and mobility management function (AMF), a session management function (AMF), a user plane function (UPF), a Service Capability Exposure Function (SCEF), or the like.

• Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that has access to (i.e., is served by) a cellular communications network by communicate wirelessly with network nodes and/or other wireless devices. Communicating wirelessly can involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. Some examples of a wireless device include, but are not limited to, smart phones, mobile phones, cell phones, voice over IP (VoIP) phones, wireless local loop phones, desktop computers, personal digital assistants (PDAs), wireless cameras, gaming consoles or devices, music storage devices, playback appliances, wearable devices, wireless endpoints, mobile stations, tablets, laptops, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart devices, wireless customer-premise equipment (CPE), mobile-type communication (MTC) devices, Intemet-of-Things (loT) devices, vehicle-mounted wireless terminal devices, etc. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short).

• Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g., a radio access node or equivalent name discussed above) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and/or operable to communicate directly or indirectly with a wireless device and/or with other network nodes or equipment in the cellular communications network, to enable and/or provide wireless access to the wireless device, and/or to perform other functions (e.g., administration) in the cellular communications network.

Note that the description herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system. Furthermore, although the term “cell” is used herein, it should be understood that (particularly with respect to 5G NR) beams may be used instead of cells and, as such, concepts described herein apply equally to both cells and beams.

Figure 1 illustrates an exemplary high-level view of the 5G network architecture, consisting of a Next Generation RAN (NG-RAN) 199 and a 5G Core (5GC) 198. NG-RAN 199 can include a set of gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs 100, 150 connected via interfaces 102, 152, respectively. In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface 140 between gNBs 100 and 150. With respect the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof.

NG-RAN 199 is layered into a Radio Network Layer (RNL) and a Transport Network Layer (TNL). The NG-RAN architecture, i.e., the NG-RAN logical nodes and interfaces between them, is defined as part of the RNL. For each NG-RAN interface (NG, Xn, Fl) the related TNL protocol and the functionality are specified. The TNL provides services for user plane transport and signaling transport.

The NG RAN logical nodes shown in Figure 1 include a central (or centralized) unit (CU or gNB- CU) and one or more distributed (or decentralized) units (DU or gNB-DU). For example, gNB 100 includes gNB-CU 110 and gNB-DUs 120 and 130. CUs (e.g., gNB-CU 110) are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. Each DU is a logical node that hosts lower-layer protocols and can include, depending on the functional split, various subsets of the gNB functions. As such, each of the CUs and DUs can include various circuitry needed to perform their respective functions, including processing circuitry, transceiver circuitry (e.g., for communication), and power supply circuitry.

A gNB-CU connects to gNB-DUs over respective Fl logical interfaces, such as interfaces 122 and 132 shown in Figure 1. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB. In other words, the Fl interface is not visible beyond gNB-CU.

Figure 2 shows a high-level view of an exemplary 5G network architecture, including a NG-RAN 299 and a 5GC 298. As shown in the figure, NG-RAN 299 can include gNBs (e.g., 210a, b) and ng-eNBs (e.g., 220a, b) that are interconnected with each other via respective Xn interfaces. The gNBs and ng- eNBs are also connected via the NG interfaces to 5GC 298, more specifically to Access and Mobility Management Functions (AMFs, e.g., 230a,b) via respective NG-C interfaces and to User Plane Functions (UPFs, e.g., 240a, b) via respective NG-U interfaces. Moreover, the AMFs 230a, b can communicate with one or more policy control functions (PCFs, e.g., 250a, b) and network exposure functions (NEFs, e.g., 260a, b). Each of the gNBs 210 can support the NR radio interface including frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of ng-eNBs 220 can support the fourth-generation (4G) Long-Term Evolution (LTE) radio interface. Unlike conventional LTE eNBs, however, ng-eNBs 220 connect to the 5GC via the NG interface. Each of the gNBs and ng-eNBs can serve a geographic coverage area including one more cells, such as cells 211a-b and 221a-b shown in Figure 2. Depending on the cell in which it is located, a UE 205 can communicate with the gNB or ng- eNB serving that cell via the NR or LTE radio interface, respectively. Although Figure 2 shows gNBs and ng-eNBs separately, it is also possible that a single NG-RAN node provides both types of functionality.

Each of the gNBs 210 can include and/or be associated with a plurality of Transmission Reception Points (TRPs). Each TRP is typically an antenna array with one or more antenna elements and is located at a specific geographical location. In this manner, a gNB associated with multiple TRPs can transmit the same or different signals from each of the TRPs. For example, a gNB can transmit different version of the same signal on multiple TRPs to a single UE. Each of the TRPs can also employ beams for transmission and reception towards the UEs served by the gNB, as discussed above.

Figure 3 shows an exemplary configuration of NR UP and CP protocol layers between a UE (310), a gNB (320), and an AMF (330), such as those shown in Figures 1-2. The Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between the UE and the gNB are common to UP and CP. The PDCP layer provides ciphering/deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP. In addition, PDCP provides header compression and retransmission for UP data.

On the UP side, Internet protocol (IP) packets arrive to the PDCP layer as service data units (SDUs), and PDCP creates protocol data units (PDUs) to deliver to RLC. The Service Data Adaptation Protocol (SDAP) layer handles quality-of-service (QoS) including mapping between quality of service (QoS) flows and Data Radio Bearers (DRBs) and marking QoS flow identifiers (QFI) in UL and DL packets. The RLC layer transfers PDCP PDUs to the MAC through logical channels (LCH). RLC provides error detection/correction, concatenation, segmentation/ reassembly, sequence numbering, reordering of data transferred to/from the upper layers. The MAC layer provides mapping between LCHs and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), hybrid ARQ (HARQ) error correction, and dynamic scheduling (on gNB side). The PHY layer provides transport channel services to the MAC layer and handles transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming.

On control plane (CP) side, the non-access stratum (NAS) layer is between UE and AMF and handles UE/gNB authentication, mobility management, and security control. The RRC layer sits below NAS in the UE but terminates in the gNB rather than the AMF. RRC controls communications between UE and gNB at the radio interface as well as the mobility of a UE between cells in the NG-RAN. RRC also broadcasts system information (SI) and performs establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) and used by UEs. Additionally, RRC controls addition, modification, and release of carrier aggregation (CA) and dual-connectivity (DC) configurations for UEs. RRC also performs various security functions such as key management.

After a UE is powered ON it will be in the RRC IDLE state until an RRC connection is established with the network, at which time the UE will transition to RRC CONNECTED state (e.g., where data transfer can occur). The UE returns to RRC IDLE after the connection with the network is released. In RRC IDLE state, the UE’s radio circuitry is active on a discontinuous reception (DRX) schedule configured by upper layers. During DRX active periods (also referred to as “DRX On durations”), an RRC IDLE UE receives SI broadcast in the cell where the UE is camping, performs measurements of neighbor cells to support cell reselection, and monitors a paging channel on Physical Downlink Control Channel (PDCCH) for pages (also referred to as paging messages) from 5GC via gNB. An NR UE in RRC IDLE state is not known to the gNB serving the cell where the UE is camping. However, NR RRC includes an RRC INACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRC INACTIVE has some properties similar to a “suspended” condition used in LTE.

As briefly mentioned above, 5G/NR technology shares many similarities with LTE. For example, NR uses CP-OFDM in the DL and both CP-OFDM and DFT-spread OFDM (DFT-S-OFDM) in the UL. As another example, NR DL and UL time-domain physical resources are organized into equal-sized 1-ms subframes. A subframe is further divided into multiple slots of equal duration, with each slot including multiple OFDM-based symbols.

Figure 4 shows an exemplary time-frequency resource grid for an NR slot. As illustrated in Figure 4, a resource block (RB) consists of a group of 12 contiguous OFDM subcarriers for a duration of a 14-symbol slot. Like in LTE, a resource element (RE) consists of one subcarrier in one symbol. An NR slot can include 14 OFDM symbols for normal cyclic prefix and 12 symbols for extended cyclic prefix.

In general, an NR physical channel corresponds to a set of REs carrying information that originates from higher layers. Downlink (DL, i.e., RAN node to UE) physical channels include Physical Downlink Shared Channel (PDSCH), Physical Downlink Control Channel (PDCCH), and Physical Broadcast Channel (PBCH).

PDSCH is the main physical channel used for unicast DL data transmission, but also for transmission of random access response (RAR), certain system information blocks (SIBs), and paging information. PBCH carries the basic system information (SI) required by the UE to access a cell. PDCCH is used for transmitting DL control information (DCI) including scheduling information for DL messages on PDSCH, grants for UL transmission on PUSCH, and channel quality feedback (e.g., CSI) for the UL channel.

Uplink (UL, i.e., UE to RAN node) physical channels include Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH), and Physical Random-Access Channel (PRACH). PUSCH is the uplink counterpart to the PDSCH. PUCCH is used by UEs to transmit uplink control information (UCI) including HARQ feedback for RAN node DL transmissions, channel quality feedback (e.g., CSI) for the DL channel, scheduling requests (SRs), etc. PRACH is used for random access preamble transmission. PDCCH is confined to a region containing a particular number of symbols and a particular number of subcarriers, referred to as the control resource set (CORESET). A CORESET can include one or more RBs (i.e., multiples of 12 REs) in the frequency domain and 1-3 OFDM symbols in the time domain. For example, the CORESET can be in the first two symbols in a DL slot and each of the other 12 symbols contains PDSCH. Depending on the particular CORESET configuration, however, the first two symbols can also carry PDSCH or other information, as required.

The smallest unit used for defining CORESET is resource element group (REG), which spans one RB (i.e., 12 REs) in frequency and one OFDM symbol in time. CORESET resources can be indicated to a UE by RRC signaling. In addition to PDCCH, each REG in a CORESET contains DMRS to aid in the estimation of the radio channel over which that REG was transmitted. An NR control channel element (CCE) consists of six REGs, which may be contiguous or distributed in frequency.

NR data scheduling can be performed dynamically, e.g., on a per-slot basis. In each slot, the gNB transmits DL control information (DCI) over PDCCH that indicates which RRC CONNECTED UE is scheduled to receive data in that slot, as well as which RBs will carry that data. A UE first detects and decodes DCI and, if the DCI includes DL scheduling information for the UE, receives the corresponding PDSCH based on the DL scheduling information. DCI formats 1 0 and 1 1 are used to convey PDSCH scheduling. Likewise, DCI on PDCCH can include UL grants that indicate which UE is scheduled to transmit data on PUCCH in that slot, as well as which RBs will carry that data. A UE first detects and decodes DCI and, if the DCI includes an uplink grant for the UE, transmits the corresponding PUSCH on the resources indicated by the UL grant.

PDCCH configuration (possibly including multiple options) is part of a search space configuration associated with a bandwidth part (BWP) in a serving cell. This search space configuration is provided to the UE via RRC and does not depend on individual PDCCH payloads. The contents of a scheduling DCI carried in PDCCHs defines a payload structure (e.g., size and MCS) scheduled DL data carried in the subsequent PDSCH. Cell radio network temporary identifiers (C-RNTIs) used for PDCCH transmissions are also configured via RRC.

Given a previously configured search spaces, a UE tries to detect a PDCCH addressed to it according to multiple hypotheses (also referred to as “candidates”) in a process known as “blind decoding.” PDCCH candidates span 1, 2, 4, 8, or 16 CCEs, with the number of CCEs referred to as the aggregation level (AL) of the PDCCH candidate. If more than one CCE is used, the information in the first CCE is repeated in the other CCEs. By varying AL, PDCCH can be made more or less robust for a certain payload size. In other words, PDCCH link adaptation can be performed by adjusting AL. Depending on AL, PDCCH candidates can be located at various time-frequency locations in the CORESET.

A hashing function can be used to determine the CCEs corresponding to PDCCH candidates that a UE must monitor within a search space set. The hashing is done differently for different UEs. In this manner, CCEs used by the UEs are randomized and the probability of collisions between multiple UEs having messages included in a CORESET is reduced. Once a UE decodes a DCI, it de-scrambles the CRC with RNTI(s) that is(are) assigned to it and/or associated with the particular PDCCH search space. In case of a match, the UE considers the detected DCI as being addressed to it, and follows the instructions (e.g., scheduling information) in the DCI.

Within the NR DL, certain REs within each subframe are reserved for the transmission of RS. These include DMRS mentioned above, which are transmitted to aid the UE in the reception of an associated PDCCH or PDSCH. Other DL reference signals include positioning RS (PRS) and channel state information RS (CSI-RS), the latter of which are monitored by the UE for the purpose of providing channel quality feedback for the DL channel. Additionally, phase-tracking RS (PTRS) are used by the UE to identify common phase error (CPE) present in sub-carriers of a received DL OFDM symbol.

PDCCH DMRS are mapped with the same density to all REGs in all OFDM symbols of a given PDCCH candidate. In particular, PDCCH DMRS is included in Res 1, 5, and 9 in each REG, giving a density of 1:4. Also, PDCCH DMRS are scrambled by Gold sequences that can be configured to be UE- specific, e.g., via RRC.

PDSCH DMRS can be allocated in individual symbols or in consecutive symbol pairs, but in either case are confined to the bandwidth and duration of PDSCH scheduled (i.e., via PDCCH) for a particular UE. There are two types of frequency mapping and two types of symbol mapping available for PDSCH DM-RS. For frequency mapping, Type-1 is comb-based with two code division multiplexing (CDM) groups while Type-2 is non-comb-based with three CDM groups. For symbol mapping, in Type- A slot-based scheduling, PDSCH DMRS starts in symbol 2 or 3 of the slot (where 0 is the initial symbol). In Type-B non-slot-based scheduling, PDSCH DMRS starts in the first symbol of the scheduled PDSCH duration. In either type, PDSCH DMRS can be inserted throughout the scheduled PDSCH duration (e.g., in a slot) in various configurations.

Other RS-like DL signals include Primary Synchronization Sequence (PSS) and Secondary Synchronization Sequence (SSS), which facilitate the UEs time and frequency synchronization and acquisition of system parameters (e.g., via PBCH). For example, PSS can be used for coarse synchronization and cell group identification while SSS can be used for cell identification. PSS, SSS, and PBCH are collectively referred to as an SS/PBCH block (SSB). Each NR SSB carries NR-PSS, NR-SSS, and NR-PBCH in four (4) successive symbols.

Each SSB burst includes one or multiple SSBs, with the SSB burst being repeated periodically such as every 5, 10, 20, 40, 80, or 160 milliseconds (ms). A UE is configured with one or more SSB block measurement timing configurations (SMTC), which provide information about SSB transmissions on cells of certain carrier frequency. SMTC includes parameters such as periodicity, duration of each repetition, time offset with respect to a reference time (e.g., serving cell’s SFN), etc.

Figures 5-7 show exemplary SSB arrangements. In particular, Figure 5 shows the arrangement of a single SSB in four successive symbols, n ... n+3. The SSB bandwidth is 240 subcarriers, with NR-PSS and NR-SSS carried in the central 127 sub-carriers in symbols n and n+2, respectively. NR-PBCH spans the entire SSB bandwidth in symbols n+1 and n+3, as well as the four PRBs (48 subcarriers) on each end of the SSB bandwidth in symbol n+2. PBCH also includes DMRS to facilitate channel estimation and demodulation.

Figure 6 shows arrangement of SSBs within two consecutive timeslots, m and m+1, for various sub-carrier spacing (SCS). There are multiple candidate SSB positions within each of the timeslots. In other words, the single SSB shown in Figure 5 can be at one of these candidate SSB positions shown in Figure 6.

In NR deployments, a cell is identified using one or more SSB beams (up to 64 in frequency range FR2). Only one SSB beam is transmitted in each slot. Assuming that slot m and m+1 in Figure 6 carry two different SSB beams, Figure 7 shows how these two SSB beams are repeated across multiple slots for various combinations of SCS and number of SSB beams per cell (L).

Thus, a RAN node that provides the UE’s cell group typically activates one or more of the SCells only when there is data traffic that can utilize the additional capacity provided by the SCell(s). When the traffic reduces to a level that can be handled by fewer SCells, the RAN node deactivates one or more of the UE’s SCells. For example, SCell activation, deactivation, and reactivation may be performed via PCell signaling (e.g., MAC control elements, such as SCell activation or SCell deactivation MAC CEs).

In NR Rel-15, SCell activation/reactivation time is quite long (e.g., at least 100 ms) due to time reserved for the UE to synchronize with and perform measurements on SSBs transmitted on the newly activated SCell. Figure 8 shows an example of SCell activation and UE energy consumed during that process. Initially, the UE’s receiver is in light sleep operating mode, in which the UE consumes a relatively small amount of energy (referred to as “low-energy state”). After the UE receives the SCell activation command (e.g., via the UE’s PCell), it switches the receiver to normal operating mode, in which the UE consumes a relatively large amount of energy.

The UE remains in normal operating mode until it receives the first SSB transmitted on the SCell then switches to micro-sleep operating mode, in which the UE consumes an intermediate amount of energy. The UE remains in micro-sleep until switching back to normal operating mode just before receiving the next-scheduled SSB, after which it switches briefly back to micro-sleep before receiving the scheduling PDCCH and scheduled DL data on PDSCH. Subsequently, the UE switches back to light sleep until a next event.

There are two primary observations from Figure 8. First, the UE consumes a significant amount of energy during the SCell activation process, before receiving PDCCH/PDSCH. Second, there is a significant latency period between the activation command and receiving PDCCH/PDSCH. Since the UE cannot utilize the SCell during this latency period, SCell deactivation/reactivation has been conventionally used as a longer-term solution to deal with trends in data traffic - rather than to address dynamic UE data traffic requirements.

However, the NR Rel-17 Fast SCell Activation feature is not part of baseline CA operation and, as such, is not guaranteed to be supported by UE and RAN vendors. Moreover, the NR Rel-17 Fast SCell Activation feature still introduces a significant, undesirable SCell activation latency. In order to use dynamic SCell activation to address dynamic UE data traffic requirements, there is a need for a better solution with less latency.

Embodiments of the present disclosure address these and other problems, issues, and/or difficulties by providing a rapid SCell reactivation for a UE in RRC CONNECTED state whose SCell connection is deactivated (incl. dormant) but the PCell connection remains active. The UE may receive an SCell activation or reactivation command via DCI or MAC-CE on the PCell or another active SCell. A UE whose deactivation duration is relatively short and whose environment is relatively static (e.g., automatic gain control (AGC) and preferred beam settings remain relatively stable) may re-acquire SCell synchronization without having to wait for transmission of one or more synchronization signals (e.g., SSB and/or TRS) in the SCell as in conventional SCell activation. As such, data transmission in the SCell may commence shortly after the activation command.

Embodiments include techniques whereby, upon detecting the activation command on the PCell, the UE wakes up its SCell receiver shortly before the expected scheduling PDCCH on SCell and uses first received SCell PDCCH symbol(s) for fine frequency synchronization without receiving any synchronization signals (e.g., SSB and/or TRS) transmitted in the SCell. For example, the UE performs fine synchronization using PDCCH DMRS, and uses the sync result for SCell PDCCH/PDSCH reception and decoding.

These operations are facilitated by the UE remaining synchronized with the PCell while the SCell is deactivated and by a worst-case PCell-SCell frequency offset of 0.4 parts per million (ppm). In other words, based on remaining synchronized with the PCell, the UE may perform direct SCell frequency estimation directly using PDCCH DMRS, received and regenerated PDCCH, PDSCH DMRS, PTRS, etc. without having to wait for SSB or TRS transmitted in the SCell.

In some embodiments, the UE’s serving RAN node (e.g., gNB) can obtain information about UE capability for rapid SCell activation, including the UE’s minimum required delay between an SCell activation command and the UE being ready to receive PDCCH/PDSCH in the SCell. The RAN node may perform the first PDCCH transmission to the UE in the SCell, before the RAN node’s next- scheduled transmission of a synchronization signal (e.g., SSB and/or TRS) in the SCell transmissions.

Embodiments of the present disclosure can provide various benefits, advantages, and/or solutions to various problems. For example, embodiments can beneficially reduce SCell activation latency by removing dependence on RAN node synchronization signal transmission schedules. Instead, SCell activation latency will now be dependent only on UE receiver state change latency, which for example requires -3-5 ms when exiting light sleep or -20 ms when exiting deep sleep. Accordingly, embodiments advantageously increase utility of dynamic SCell deactivation for UE energy consumption management and dynamic utilization of SCells for dynamic UE data capacity.

Although embodiments are described in the context of the UE receiving an SCell activation on the PCell (e.g., for a Master Cell Group or equivalently the PSCell for a Secondary Cell Group), embodiments are equally applicable to the case where the UE receives an SCell activation command on an active SCell. For example, the UE may be configured with a first SCell and a second SCell, and the UE receives an activation command for the deactivated first SCell via the activated second SCell.

Similarly, embodiments are also applicable to the case of returning to PDCCH monitoring from a dormant SCell state. For a deactivated SCell, a UE is not expected to monitor anything on the SCell or be ready for scheduling on the SCell. In contrast, a dormant SCell is still activated but the active BWP doesn't include any PDDCH monitoring occasions. This can also be referred to as a “dormant BWP”, and activation DCI on PCell tells the UE to switch to a different BWP for monitoring, which takes less time than SCell reactivation. Nevertheless, the UE’s receiver operational logic is similar in dormancy and deactivation conditions.

Figure 9 shows an exemplary SCell activation procedure and UE energy consumed during that procedure, according to some embodiments of the present disclosure. Initially, the UE’s receiver is in light sleep operating mode, in which the UE consumes a relatively small amount of energy (referred to as “low-energy state”). After the UE receives the SCell activation command (e.g., via the UE’s PCell), it switches the receiver to normal operating mode, in which the UE consumes a relatively large amount of energy.

In contrast to the conventional approach shown in Figure 8, the UE receives a scheduling PDCCH in the SCell shortly after switching the receiver to normal operating mode. The UE remains in normal operating mode until after receiving all scheduled DL data on PDSCH, after which it switches back to light sleep until a next event.

In contrast to the conventional approach shown in Figure 8, the UE performs these operations before receiving the next-scheduled SSB in the SCell, which occurs after the PDCCH/PDSCH transmissions. At that time, the UE has already switched back to light sleep where it consumes a relatively low amount of energy. In this example, the UE does not enter the intermediate micro-sleep operating mode at all. A comparison of the shaded regions in Figures 8-9 illustrates the improvements in UE energy consumption that embodiments of the present disclosure can provide. Moreover, the UE receives PDCCH/PDSCH much sooner after SCell activation than in the conventional approach, which improves the utility of dynamic SCell activation.

In some embodiments, the UE may determine a rapid activation delay based on implementation constraints. For example, the delay may be based on the wake-up delay to exit an SCell sleep state invoked during the deactivated phase, e.g., 3-5 ms to exit light sleep, ~20 ms to exit deep sleep, etc.

In some embodiments, the UE may enter SCell deep sleep upon SCell deactivation if the current traffic type is of a first category (non-latency-sensitive traffic) and enter SCell light sleep for a second traffic category (latency-sensitive traffic). The reactivation delay may then be determined already at SCell deactivation based on the planned sleep type, the traffic category, etc. For example, the UE enters deep sleep for a deactivated SCell assuming a default RAN node implementation, such as the RAN node deactivates the SCell when the minimum time to reactivate is more than 20 ms. The UE may observe RAN node behavior to determine the appropriate receiver operating (sleep) state during SCell deactivation.

In some variants, the UE may enter deep sleep state when the SCell is deactivated, unless it observes that the RAN node reactivates the SCell less than 20 ms after deactivation. If the UE does observe this RAN node behavior, the UE may enter light sleep during subsequent SCell deactivations.

In some embodiments, the UE may indicate the UE’s activation delay to the RAN node. This allows the RAN node to know whether the UE can handle a short activation-to-scheduling delay (or offset) when commencing data transmission on the SCell. In different variants, the signaling used to carry this indication may be standardized or proprietary UE capability signaling via RRC. In some embodiments, the UE can indicate the activation delay per SCell, per band, per numerology (e.g., sub- carrier spacing), per UE sleep state, for different ranges of deactivation duration, etc. or any combination thereof.

The activation delay values indicated by the UE may also depend on UE receiver architecture and whether the SCells (e.g., intra-band) utilize the same receiver hardware as other activated cells (e.g., PCell). In some embodiments, the activation delay values may also depend on UE type (which may be known to the RAN node from the UE capability signaling). For example, a first UE type may have a predetermined activation delay value of D 1 while a second UE type may have a predetermined activation delay value of D2.

In some embodiments, the UE’s rapid SCell activation capability may be limited to a specified maximum deactivation duration and/or a maximum vehicular movement speed (or Doppler frequency shift). For example, the UE may refrain from rapid SCell activation when the deactivated duration exceeds a threshold, since the receiver AGC and preferred beams are more likely to have changed over this duration.

In some embodiments, the indication activation delay values may be associated with validity timers that are started after a SCell is deactivated. For example, the activation delay may be relatively short if the SCell was very recently deactivated (e.g., 1 second or less) and the previous time and frequency (T/F) offsets for the SCell (which may be stored by the UE upon deactivation) would still be valid if the SCell is reactivated. In contrast, the delay may be longer if a longer duration has passed since SCell deactivation.

In some embodiments, the indication of the UE’s SCell activation delay capabilities may be signaled dynamically via DCI or MAC CE on the PCell during SCell deactivation. The signaling may indicate the currently valid rapid SCell activation delay for the UE, based on the planned or actual sleep state, environment changes, vehicular speed, etc.

In some embodiments, the RAN node can also detect that the UE can apply rapid SCell activation. For example, the RAN node can transmit a PDCCH relatively soon after the SCell activation command (e.g., 20 or 40ms), and the RAN node detects whether the UE has activated the SCell successfully when one or more of the following occurs:

• the UE acknowledges that the PDCCH-scheduled PDSCH transmission was successfully received, e.g., by HARQ feedback; and

• the UE responded to a command in PDCCH, e.g., with a CSI report.

In complementary operation, the UE anticipates receiving a scheduling PDCCH relatively soon after the SCell activation command (e.g., 20 or 40ms), and decides to perform rapid SCell activation accordingly. In some embodiments, based on exploratory PDCCH transmissions, the RAN node may learn that the UE requires different SCell reactivation delays depending on SCell deactivation duration, carrier and/or band used for the SCell, etc.

While the SCell is deactivated, the UE is configured by the RAN node to monitor DCI and/or MAC CE signaling on the PCell. These may carry SCell (re-)activation commands, among other information relevant to the UE. A detected SCell activation command indicates that the UE should be resuming PDCCH monitoring on the SCell. The UE wakes up the SCell receiver hardware, using an appropriate procedure for returning from the configured low-energy state (e.g., light sleep or deep sleep).

When the SCell receiver hardware is in normal operating mode (e.g., as shown in Figure 9), the UE commences PDCCH monitoring on the SCell according to the configured search space/CORESET. In some embodiments, the UE starts PDCCH monitoring after a minimum activation signal-to- monitoring offset that has been predetermined, previously configured by the RAN node, that the UE has signaled to the RAN node, or that the UE has autonomously considered and implemented without informing the RAN node.

The UE initially monitors the SCell for PDCCH using T/F references associated with the PCell. If the PCell and SCell transmitters have separate and/or independent frequency references (e.g., local oscillators), the worst-case frequency offset between PCell and SCell is 0.4 ppm (based ±0.2 ppm per RAN node). As such, T/F references associated with the PCell may be used for the SCell signal, which the UE samples at expected PDCCH monitoring occasions (MOs). The UE may also sample and store the rest of the slot following the PDCCH to obtain PDSCH samples for subsequent demodulation.

In another example, the UE can use reference and/or synchronization signals (e.g., SSB, CSI- RS, TRS) transmitted on other carriers (e.g., PCell, SpCell, another SCell) to facilitate fine synchronization .

In various embodiments, the UE may perform fine synchronization at SCell PDCCH occasions using PDCCH DMRS, employing a variety of baseband processing options. Some examples are given below but other variants and/or combinations of these examples may also be used.

In some embodiments, the UE may utilize the DMRS resource elements (REs) with known contents for correlation-based T/F hypothesis testing in the time-domain. In such case, the UE tests different T/F hypotheses based on corresponding reference sequences. In other embodiments, the UE may utilize the DMRS REs with known contents for correlation- based T/F hypothesis testing in the frequency-domain. In such case, the UE tests different T/F hypotheses based on inter-carrier leakage and phase rotation hypotheses after an FFT. For example, if the frequency offset is incorrect, there will be leakage into adjacent subcarriers.

In some embodiments, the UE may utilize DMRS REs in two PDCCH symbols after the FFT to directly estimate phase rotation between the symbols and derive the frequency error. In other embodiments, the UE may utilize DMRS REs in a single PDCCH symbol in the time domain to directly estimate phase rotation between the first and second halves of the symbol and derive the frequency error.

In some embodiments, the time offset may be further refined using the PDCCH symbol(s) by estimating the inter-carrier phase rotation after the FFT.

In some embodiments, the UE may perform fine synchronization using PDCCH DMRS only if the probability of DMRS being present exceeds a threshold. For example, the UE can determine and/or estimate this probability based on correlation results for hypothesis testing (or other signal quality metric) exceeds a threshold.

In some embodiments, the SCell PDCCH may be detected based on PCell synchronization (e.g., PCell T/F offsets), and the regenerated SCell PDCCH REs may be used for SCell fine synchronization procedures, using techniques like the ones discussed above. Alternatively, PDSCH DMRS or PTRS may be used for the same purpose. For example, based on receiving PDCCH in a timeslot, the UE is aware of the PDSCH/DMRS structure for that timeslot. In general, PDSCH can be used in addition or as an alternative to PDCCH for fine synchronization.

In general, the UE performs fine synchronization for a short duration until the first SCell PDCCH transmission is detected. The risk that the SCell carries no PDCCH intended for the UE is relatively low, since the SCell is typically activated only when (i.e., shortly before) the UE is to be scheduled for data communication with the RAN node via the SCell.

In various embodiments, the SCell fine synchronization obtained by the UE according to various embodiments described above is then used by the UE to receive (e.g., demodulate and decode) SCell PDCCH and PDSCH transmissions intended for the UE.

In some embodiments, the UE can compensate PDCCH (and optionally PDSCH) samples used for fine synchronization with updated T/F offset estimates (i.e., obtained via the fine synchronization) before demodulation and decoding. In other embodiments, the SCell fine synchronization results (T/F offsets) are applied to the SCell receiver RF stage prior to PDSCH sampling. In such case, there is then no need for PDSCH sample compensation.

In some embodiments, the UE may determine PCell/SCell T/F offset statistics from previous transmissions and adapt the synchronization process. If the expected offset below some threshold, this may indicate that the RAN node uses a common frequency reference for PCell and SCell. In such case, the UE may omit the SCell fine synchronization procedure and proceed with SCell PDCCH/PDSCH reception based on the PCell T/F offsets. Although Figure 9 shows the UE receiving PDCCH/PDSCH after an SCell activation command without first receiving SSB, in some cases the UE may receive an SSB (or other synchronization signal) before receiving PDCCH/PDSCH on the SCell. This may be done based on UE convenience and/or necessity, as well as the timing of a next-scheduled synchronization signal. For example, in Figure 9, the UE may receive the first SSB after the activation command for receiver automatic gain control (AGC) and measurements. Even so, these embodiments can provide reduced latency compared to the conventional approach illustrated by Figure 8, since fewer SSBs (e.g., one SSB instead of three SSBs) are needed when combined with PDCCH/PDSCH DMRS fine synchronization according to embodiments of the present disclosure.

In some embodiments, the UE may condition performing rapid SCell activation, according to embodiments described above, based on the number of DMRS REs available for fine SCell synchronization being above a threshold. For example, when the number of DMRS REs is less than a threshold, the UE and RAN node may then determine not to implement the rapid SCell activation and instead perform conventional SCell activation based on receiving synchronization signals transmitted in the SCell. In contrast, the number of DMRS REs is equal to or larger than the threshold, the UE may perform (and RAN node facilitate) rapid SCell activation without the UE receiving synchronization signals transmitted in the SCell. In some embodiments, the UE may obtain the number of available DMRS REs based on RRC configurations for the SCell, provided to the UE by the RAN node.

Since the UE performs fine synchronization on REs that are also used for PDCCH (and possibly also PDSCH) reception, the UE may require additional time in decoding the PDCCH and PDSCH compared to when the already-synchronized UE receives PDCCH and PDSCH. In some embodiments, the UE can require a minimum gap (Y) between receiving PDCCH or PDSCH and the sending responsive HARQ feedback to the RAN node.

In some variants, this minimum gap (Y) may be applicable to only the initial X PDCCH or PDSCH received after SCell activation, after which the UE can be assumed to be fully synchronized. The values of X and Y can be any integers (e.g., 1, 2, etc.). In one example, the minimum gap (Y) can be counted from the slot of PDCCH reception to the slot of HARQ feedback. In another example, the minimum gap can be counted from the slot of PDSCH reception to the slot of HARQ feedback. In some variants, the minimum gap may be in terms of symbols, e.g., for an intra-slot delay. In some variants, the minimum gap (Y) may depend on UE type, UE category, etc.

In general, the UE’s serving RAN node can perform complementary operations to facilitate the UE’s operations according to various embodiments described above.

In some embodiments, the RAN node may receive from the UE an indication of the UE’s rapid SCell activation capability. In other embodiments, the RAN node may test the UE’s capability for rapid SCell activation. For example, the RAN node can transmit PDCCH at different delays after the activation command and observe whether the UE can receive the PDCCH at the respective delays. From this, the RAN node can determine a minimum scheduling offset the UE requires after the SCell activation command. In some embodiments, the RAN node may perform such tests dynamically and store the results while the UE’s SCell is deactivated. Alternatively, a RAN node vendor can test different UE chipset versions offline and apply a UE chipset-dependent scheduling offset in deployment based on chipset version for each UE being served by the RAN node.

In general, the RAN node determines (e.g., using legacy methods) that a UE’s deactivated SCell should be reactivated to support data transmission that cannot be properly supported by the UE’s PCell and/or other UE SCells. The RAN node transmits an activation command via DCI or MAC CE via the PCell or another activated SCell, as the case may be. After transmitting the SCell activation command, the RAN node waits at least the scheduling offset before transmitting PDCCH/PDSCH intended for the UE.

In some embodiments, the RAN node can initially transmit PDCCH/PDSCH to the UE using wide beams to improve robustness, at least until an updated beam report is available from the UE. In some embodiments, if the RAN node observes that one or more SCell transmissions based on rapid SCell activation schedule offset fail (e.g., no UE HARQ feedback), the RAN node may revert to using the legacy activation delay.

The embodiments described above can be further illustrated with reference to Figures 10-11, which show exemplary methods (e.g., procedures) for a UE and a RAN node, respectively. In other words, various features of operations described below correspond to various embodiments described above. These exemplary methods can be used cooperatively to provide various exemplary benefits and/or advantages. Although Figures 10-11 show specific blocks in a particular order, the operations of the respective methods can be performed in different orders than shown and can be combined and/or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

In particular, Figure 10 (which includes Figures 10A-B) shows a flow diagram of an exemplary method (e.g., procedure) for a UE configured to communicate with a RAN via a PCell and at least a first SCell, according to various embodiments of the present disclosure. The exemplary method can be performed by a UE (e.g., wireless device) such as described elsewhere herein.

The exemplary method can include the operations of block 1030, where while the first SCell is activated, the UE can deactivate the first SCell in response to receiving from a RAN node a first command to deactivate the first SCell. The exemplary method can also include the operations of block 1050, where the UE can subsequently receive a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated. The exemplary method can also include the operations of block 1070, where the UE can synchronize to the first SCell in response to the second command and without receiving any synchronization signals (e.g., SSB or TRS) transmitted in the first SCell.

In some embodiments, the exemplary method can also include the operations of block 1040, where the UE can maintain synchronization with the PCell while the first SCell is deactivated. In such case, synchronizing to the first SCell without receiving any synchronization signals transmitted in the first SCell in block 1050 can include the operations of sub-block 1051, where the UE can perform fine synchronization with the first SCell based on the synchronization maintained with the PCell while the first SCell was deactivated.

In some of these embodiments, the exemplary method can also include the operations of block 1055, where in response to the second command (e.g., in block 1050), the UE can collect samples corresponding to one or more OFDM symbols transmitted by the RAN node via the first SCell. In particular, the samples are collected based on the synchronization maintained with the PCell and without receiving a synchronization signal broadcast in the first SCell. In some of these embodiments, performing fine synchronization with the first SCell (e.g.., in block 1071) is based on the collected samples.

In some of these embodiments, the exemplary method can also include the operations of block 1060, where in response to the second command (e.g., in block 1050), the UE can collect further samples corresponding to one or more OFDM symbols transmitted by the RAN node via the PCell or via the second SCell. In these embodiments, synchronizing to the first SCell in block 1070 is based on the collected further samples.

In some of these embodiments, the one or more OFDM symbols include one or more of the following: a physical control channel (e.g., PDCCH) and associated first demodulation reference signals (DMRS), and a physical data channel (e.g., PDSCH) and associated second DMRS. In such embodiments, performing fine synchronization with the first SCell in sub-block 1071 is based on collected samples corresponding to at least one of the first DMRS and the second DMRS. In some variants, performing fine synchronization with the first SCell in sub-block 1071 comprises determining the UE’s timing and frequency offsets with respect to the first SCell based on one or more of the following:

• time-domain hypothesis testing of collected samples corresponding to the first DMRS;

• frequency-domain hypothesis testing of collected samples corresponding to the first DMRS;

• time-domain hypothesis testing of collected samples corresponding to the second DMRS; and

• frequency-domain hypothesis testing of collected samples corresponding to the second DMRS.

In some further variants, performing fine synchronization with the first SCell in sub-block 1071 is further conditioned on one or more of the following:

• a received signal strength or quality, associated with the collected samples, exceeds a corresponding threshold;

• a quantity of first DMRS and/or second DMRS that are expected to be included in the collected samples exceeds a corresponding threshold; and

• each of the one or more hypothesis testing exceeds a corresponding threshold.

In some further variants, the exemplary method can also include the operations of block 1015, where while the first SCell is activated before receiving the first command, the UE can receive from the RAN node a first configuration for the physical control channel and associated first DMRS. In such case, the hypothesis testing of collected samples corresponding to the first DMRS is based on the first configuration. In some further variants, the exemplary method can also include the operations of block 1005, where the UE can receive from the RAN node an SCell configuration for the first SCell. The SCell configuration includes a second configuration of the physical data channel and the associated second DMRS, and the hypothesis testing of collected samples corresponding to the second DMRS is based on the second configuration.

In some of these embodiments, the exemplary method can also include the operations of block 1080, where the UE can demodulate at least a portion of the collected samples after synchronizing to the first SCell, including one or more of the following operations labelled with corresponding sub-block numbers:

• (1082) demodulating the collected samples that correspond to the physical control channel to obtain downlink control information intended for the UE; and

• (1083) demodulating the collected samples that correspond to the physical data channel to obtain data intended for the UE.

In some variants, demodulating at least a portion of the collected samples in block 1080 also includes the operations of sub-block 1081, where the UE can apply timing and frequency offsets of the UE with respect to the first SCell (which were determined based on the first DMRS and/or the second DMRS) to the collected samples prior to demodulation (e.g., in sub-blocks 1082-1083).

In some variants, the obtained downlink control information (e.g., in sub-block 1082) includes a scheduling message intended for the UE. In such variants, the exemplary method also includes the operations of block 1090, where the UE can send an uplink message to the RAN node in response to the scheduling message. Specifically, a duration between the uplink message and one of the following is based on the synchronization maintained with the PCell while the first SCell was deactivated: the scheduling message; or the data intended for the UE, which is scheduled by the scheduling message.

In some embodiments, the exemplary method can also include the operations of block 1010, where while the first SCell is activated before receiving the first command, the UE can estimate time and frequency offsets between the PCell and the first SCell. In such embodiments, synchronizing to the first SCell in response to the second command in block 1070 includes the following operations, labelled with corresponding sub-block numbers:

• (1071) performing the fine synchronization with the first SCell when the estimated time and frequency offsets are greater than a threshold; and

• (1072) refraining from performing the fine synchronization with the first SCell when the estimated time and frequency offsets are not greater the threshold.

In some embodiments, deactivating the first SCell in block 1030 includes the operations of sub- block 1031, where the UE can select one of a plurality of available low-energy modes and operating in the selected low-energy mode. In some of these embodiments, selecting one of the plurality of available low-energy modes is based on one or more of the following:

• one or more types or classes of data traffic recently received from the RAN node;

• an indication from the RAN mode of a minimum duration until reactivation of the first SCell; • historical information about durations between RAN node deactivation and reactivation of

SCells;

• a schedule for UE low-energy operation;

• UE receiver architecture; and

• carrier frequencies of the PCell and SCells configured for the UE, including the first SCell.

In some of these embodiments, the exemplary method can also include the operations of block 1020, where the UE can send to the RAN node an indication of a minimum required delay between the UE receiving a command to activate an SCell and the UE initiating synchronization to the SCell being activated. The indicated minimum required delay is based on the selected low-energy mode (e.g., from sub-block 1031), and a duration between receiving the second command (e.g., in block 1050) and initiating synchronizing to the first SCell (e.g., in block 1070) is at least the indicated minimum required delay. In some variants, the indication is sent (e.g., in block 1020) via the PCell after receiving the first command (e.g., in 1030).

In other of these embodiments, the exemplary method can also include the operations of block 1025, where the UE can receive from the RAN node an indication of a minimum delay between sending a command to activate an SCell and transmitting information to the UE via the SCell being activated. The low-energy mode is selected (e.g., in sub-block 1031) based on the indicated minimum delay, and a duration between receiving the second command (e.g., in block 1050) and initiating synchronizing to the first SCell (e.g., in block 1070) is at least the indicated minimum delay.

In addition, Figure 11 shows a flow diagram of an exemplary method (e.g., procedure) for a RAN node configured to provide a PCell and at least a first SCell to a UE, according to various embodiments of the present disclosure. The exemplary method can be performed by a RAN node (e.g., base station, eNB, gNB, ng-eNB, en-gNB, etc., or components thereof) such as described elsewhere herein.

The exemplary method can include operations of block 1110, where the RAN node can send, to a UE, a configuration for measurement and reporting by the UE. The configuration identifies the following: radio resources on which RS are or will be transmitted by the RAN node, and a mapping of the identified radio resources to a plurality of RAN node antenna ports used to transmit the RS. For example, the RS can be CSI-RS and the RAN node antenna ports can be CSI-RS ports.

The exemplary method can also include the operations of block 1140, where while the first SCell is activated, the RAN node can send to the UE a first command to deactivate the first SCell. The exemplary method can also include the operations of block 1150, where the RAN node can subsequently send a second command to activate the first SCell to the UE via the PCell or via a second SCell that is activated. The exemplary method can also include the operations of block 1170, where after sending the second command but before a next-scheduled transmission of a synchronization signal in the first SCell, the RAN node can transmit one or more of the following information via the first SCell:

• a physical control channel (e.g., PDCCH) carrying downlink control information intended for the UE; and

• a physical data channel (e.g., PDSCH) carrying data intended for the UE. In some embodiments, the exemplary method can also include the operations of block 1145, where the RAN node can maintain synchronization with the UE via PCell while the first SCell is deactivated. In such embodiments, transmitting the information in block 1170 before the next-scheduled transmission of the synchronization signal is based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated.

In some of these embodiments, the transmitted information is arranged into one or more OFDM symbols, which include one or more of the following: the physical control channel and associated first DMRS, and the physical data channel and associated second DMRS. In some of these embodiments, at least one of the first DMRS and the second DMRS facilitates fine synchronization of the UE with the first SCell, based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated.

In some variants, the exemplary method can also include the operations of block 1110, where the RAN node can send to the UE a first configuration for the physical control channel and associated first DMRS. In such case, fine synchronization of the UE with the first SCell is further based on the first configuration.

In some variants, the exemplary method can also include the operations of block 1105, where the RAN node can send to the UE an SCell configuration for the first SCell. The SCell configuration includes a second configuration of the physical data channel and the associated second DMRS, and fine synchronization of the UE with the first SCell is further based on the second configuration.

In some embodiments, the downlink control information includes a scheduling message intended for the UE and the exemplary method can also include the operations of block 1180, where the RAN node can receive an uplink message from the UE in response to the scheduling message. In such case, a duration between the uplink message and one of the following is based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated: the scheduling message; or the data intended for the UE, which is scheduled by the scheduling message.

In some embodiments, the exemplary method can also include the operations of block 1120, where the RAN node can receive from the UE an indication of a minimum required delay between the UE receiving a command to activate an SCell and the UE initiating synchronization to the SCell being activated. In some of these embodiments, the indication is received from the UE via the PCell after sending the first command (e.g., in block 1140). In other embodiments, the exemplary method can also include the operations of block 1130, where the RAN node can send to the UE an indication of a minimum delay between sending a command to activate an SCell and transmitting information to the UE via the SCell being activated.

In some of these embodiments, the duration between sending the second command (e.g., in block 1150) and transmitting the information to the UE via the SCell (e.g., in block 1170) is greater than or equal to the minimum delay indicated by the RAN node (e.g., in block 1130) or the minimum required delay indicated by the UE (e.g., in block 1120).

In some embodiments, the exemplary method can also include the operations of block 1125, where the RAN node can select the minimum delay indicated to the UE (e.g., in block 1130) based on one or more of the following:

• one or more types or classes of data traffic recently transmitted to the UE;

• one or more low-energy operating modes available for the UE;

• historical information about durations between RAN node deactivation and reactivation of SCells;

• historical information about observed UE minimum required delay;

• one or more of the following UE characteristics: manufacturer, model, chipset supplier, chipset model, and software version;

• carrier frequencies of the PCell and SCells configured for the UE, including the first SCell; and

• observed UE Doppler frequency shift.

In some embodiments, the physical control channel including the downlink control information is transmitted a first duration after sending the second command, and the downlink control information includes a scheduling message for the data carried on the physical data channel. In such embodiments, the exemplary method can also include the operations of block 1190, where based on receiving no uplink message indicating that the UE received the data carried on the physical data channel, the RAN node can determine that the UE’s minimum required delay is greater than the first duration and retransmit the physical control channel including the downlink control information a second duration (e.g., greater than the first duration) after sending the second command.

In some of these embodiments, the exemplary method can also include the operations of block 1160, where the RAN node can select the first duration based on one or more of the following:

• one or more low-energy operating modes available for the UE;

• historical information about observed UE minimum required delay;

• observed UE Doppler frequency shift.

Although various embodiments are described herein above in terms of methods, apparatus, devices, computer-readable medium and receivers, the person of ordinary skill will readily comprehend that such methods can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, etc.

Figure 12 shows an example of a communication system 1200 in accordance with some embodiments. In this example, the communication system 1200 includes a telecommunication network 1202 that includes an access network 1204, such as a RAN, and a core network 1206, which includes one or more core network nodes 1208. The access network 1204 includes one or more access network nodes, such as network nodes 1210a and 1210b (one or more of which may be generally referred to as network nodes 1210), or any other similar 3GPP access node or non-3GPP access point. The network nodes 1210 facilitate direct or indirect connection of UEs, such as by connecting UEs 1212a, 1212b, 1212c, and 1212d (one or more of which may be generally referred to as UEs 1212) to the core network 1206 over one or more wireless connections.

Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1200 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 1200 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

The UEs 1212 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 1210 and other communication devices. Similarly, the network nodes 1210 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 1212 and/or with other network nodes or equipment in the telecommunication network 1202 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 1202.

In the depicted example, the core network 1206 connects the network nodes 1210 to one or more hosts, such as host 1216. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1206 includes one more core network nodes (e.g., core network node 1208) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1208. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

The host 1216 may be under the ownership or control of a service provider other than an operator or provider of the access network 1204 and/or the telecommunication network 1202, and may be operated by the service provider or on behalf of the service provider. The host 1216 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

As a whole, the communication system 1200 of Figure 12 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

In some examples, the telecommunication network 1202 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1202 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1202. For example, the telecommunications network 1202 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)ZMassive loT services to yet further UEs.

In some examples, the UEs 1212 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1204 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1204. Additionally, a UE may be configured for operating in single- or multi -RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

In the example, the hub 1214 communicates with the access network 1204 to facilitate indirect communication between one or more UEs (e.g., UE 1212c and/or 1212d) and network nodes (e.g., network node 1210b). In some examples, the hub 1214 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 1214 may be a broadband router enabling access to the core network 1206 for the UEs. As another example, the hub 1214 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1210, or by executable code, script, process, or other instructions in the hub 1214. As another example, the hub 1214 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1214 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1214 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1214 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub 1214 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

The hub 1214 may have a constant/persistent or intermittent connection to the network node 1210b. The hub 1214 may also allow for a different communication scheme and/or schedule between the hub 1214 and UEs (e.g., UE 1212c and/or 1212d), and between the hub 1214 and the core network 1206. In other examples, the hub 1214 is connected to the core network 1206 and/or one or more UEs via a wired connection. Moreover, the hub 1214 may be configured to connect to an M2M service provider over the access network 1204 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1210 while still connected via the hub 1214 via a wired or wireless connection. In some embodiments, the hub 1214 may be a dedicated hub - that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 1210b. In other embodiments, the hub 1214 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1210b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.

Figure 13 shows a UE 1300 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.

A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to- vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). The UE 1300 includes processing circuitry 1302 that is operatively coupled via a bus 1304 to an input/output interface 1306, a power source 1308, a memory 1310, a communication interface 1312, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 13. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

The processing circuitry 1302 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1310. The processing circuitry 1302 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1302 may include multiple central processing units (CPUs).

In the example, the input/output interface 1306 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1300. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

In some embodiments, the power source 1308 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1308 may further include power circuitry for delivering power from the power source 1308 itself, and/or an external power source, to the various parts of the UE 1300 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1308. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1308 to make the power suitable for the respective components of the UE 1300 to which power is supplied.

The memory 1310 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1310 includes one or more application programs 1314, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1316. The memory 1310 may store, for use by the UE 1300, any of a variety of various operating systems or combinations of operating systems.

The memory 1310 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory 1310 may allow the UE 1300 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1310, which may be or comprise a device-readable storage medium.

The processing circuitry 1302 may be configured to communicate with an access network or other network using the communication interface 1312. The communication interface 1312 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1322. The communication interface 1312 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1318 and/or a receiver 1320 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1318 and receiver 1320 may be coupled to one or more antennas (e.g., antenna 1322) and may share circuit components, software or firmware, or alternatively be implemented separately.

In the illustrated embodiment, communication functions of the communication interface 1312 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/intemet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1312, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., an alert is sent when moisture is detected), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and/or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE 1300 shown in Figure 13.

As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g., by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

Figure 14 shows a network node 1400 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)).

Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

The network node 1400 includes a processing circuitry 1402, a memory 1404, a communication interface 1406, and a power source 1408. The network node 1400 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1400 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1400 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1404 for different RATs) and some components may be reused (e.g., a same antenna 1410 may be shared by different RATs). The network node 1400 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1400, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1400.

The processing circuitry 1402 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 1400 components, such as the memory 1404, to provide network node 1400 functionality.

In some embodiments, the processing circuitry 1402 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1402 includes one or more of radio frequency (RF) transceiver circuitry 1412 and baseband processing circuitry 1414. In some embodiments, the radio frequency (RF) transceiver circuitry 1412 and the baseband processing circuitry 1414 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1412 and baseband processing circuitry 1414 may be on the same chip or set of chips, boards, or units.

The memory 1404 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device- readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 1402. The memory 1404 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions (collectively denoted computer program product 1404a) capable of being executed by the processing circuitry 1402 and utilized by the network node 1400. The memory 1404 may be used to store any calculations made by the processing circuitry 1402 and/or any data received via the communication interface 1406. In some embodiments, the processing circuitry 1402 and memory 1404 is integrated.

The communication interface 1406 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 1406 comprises port(s)/terminal(s) 1416 to send and receive data, for example to and from a network over a wired connection. The communication interface 1406 also includes radio front-end circuitry 1418 that may be coupled to, or in certain embodiments a part of, the antenna 1410. Radio front- end circuitry 1418 comprises filters 1420 and amplifiers 1422. The radio front-end circuitry 1418 may be connected to an antenna 1410 and processing circuitry 1402. The radio front-end circuitry may be configured to condition signals communicated between antenna 1410 and processing circuitry 1402. The radio front-end circuitry 1418 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1418 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1420 and/or amplifiers 1422. The radio signal may then be transmitted via the antenna 1410. Similarly, when receiving data, the antenna 1410 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1418. The digital data may be passed to the processing circuitry 1402. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

In certain alternative embodiments, the network node 1400 does not include separate radio front- end circuitry 1418, instead, the processing circuitry 1402 includes radio front-end circuitry and is connected to the antenna 1410. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1412 is part of the communication interface 1406. In still other embodiments, the communication interface 1406 includes one or more ports or terminals 1416, the radio front-end circuitry 1418, and the RF transceiver circuitry 1412, as part of a radio unit (not shown), and the communication interface 1406 communicates with the baseband processing circuitry 1414, which is part of a digital unit (not shown).

The antenna 1410 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 1410 may be coupled to the radio front-end circuitry 1418 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 1410 is separate from the network node 1400 and connectable to the network node 1400 through an interface or port.

The antenna 1410, communication interface 1406, and/or the processing circuitry 1402 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 1410, the communication interface 1406, and/or the processing circuitry 1402 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

The power source 1408 provides power to the various components of network node 1400 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1408 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1400 with power for performing the functionality described herein. For example, the network node 1400 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1408. As a further example, the power source 1408 may comprise a source of power in the form of a batery or batery pack which is connected to, or integrated in, power circuitry. The batery may provide backup power should the external power source fail.

Embodiments of the network node 1400 may include additional components beyond those shown in Figure 14 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject mater described herein. For example, the network node 1400 may include user interface equipment to allow input of information into the network node 1400 and to allow output of information from the network node 1400. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1400.

Figure 15 is a block diagram illustrating a virtualization environment 1500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized.

Applications 1502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1500 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

Hardware 1504 includes processing circuitry, memory that stores software and/or instructions (collectively denoted computer program product 1504a) executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1508a and 1508b (one or more of which may be generally referred to as VMs 1508), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer 1506 may present a virtual operating platform that appears like networking hardware to the VMs 1508.

The VMs 1508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1506. Different embodiments of the instance of a virtual appliance 1502 may be implemented on one or more of VMs 1508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, a VM 1508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 1508, and that part of hardware 1504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1508 on top of the hardware 1504 and corresponds to the application 1502.

Hardware 1504 may be implemented in a standalone network node with generic or specific components. Hardware 1504 may implement some functions via virtualization. Alternatively, hardware 1504 may be part of a larger cluster of hardware (e.g., such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1510, which, among others, oversees lifecycle management of applications 1502. In some embodiments, hardware 1504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1512 which may alternatively be used for communication between hardware nodes and radio units.

The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various exemplary embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and/or electronic devices and can include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special -purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

As described herein, device and/or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and/or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and/or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

Claims

1. A method performed by a user equipment, UE, configured to communicate with a radio access network, RAN, via a primary serving cell, PCell, and at least a first secondary cell, SCell, the method comprising: while the first SCell is activated, deactivating (1030) the first SCell in response to receiving from a RAN node a first command to deactivate the first SCell; subsequently receiving (1050) a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated; and synchronizing (1070) to the first SCell in response to the second command and without receiving any synchronization signals transmitted in the first SCell.

2. The method of claim 1, wherein: the method further comprising maintaining (1040) synchronization with the PCell while the first SCell is deactivated; and synchronizing (1070) to the first SCell without receiving any synchronization signals transmitted in the first SCell comprises performing (1071) fine synchronization with the first SCell based on the synchronization maintained with the PCell while the first SCell was deactivated.

3. The method of claim 2, further comprising, in response to the second command, collecting (1055) samples corresponding to one or more OFDM symbols transmitted by the RAN node via the first SCell, wherein the samples are collected based on the synchronization maintained with the PCell and without receiving a synchronization signal broadcast in the first SCell.

4. The method of claim 3, wherein performing (1071) fine synchronization with the first SCell is based on the collected samples.

5. The method of any of claims 3-4, further comprising, in response to the second command, collecting (1060) further samples corresponding to one or more OFDM symbols transmitted by the RAN node via the PCell or via the second SCell, wherein synchronizing to the first SCell is based on the collected further samples.

6. The method of any of claims 3-5, wherein: the one or more OFDM symbols include one or more of the following: a physical control channel and associated first demodulation reference signals, DMRS; and a physical data channel and associated second DMRS; and performing (1071) fine synchronization with the first SCell is based on collected samples corresponding to at least one of the first DMRS and the second DMRS.

7. The method of claim 6, wherein performing (1071) fine synchronization with the first SCell comprises determining the UE’s timing and frequency offsets with respect to the first SCell based on one or more of the following: time-domain hypothesis testing of collected samples corresponding to the first DMRS; frequency-domain hypothesis testing of collected samples corresponding to the first DMRS; time-domain hypothesis testing of collected samples corresponding to the second DMRS; and frequency-domain hypothesis testing of collected samples corresponding to the second DMRS.

8. The method of claim 7, wherein performing (1071) fine synchronization with the first SCell is further conditioned on one or more of the following: a received signal strength or quality, associated with the collected samples, exceeds a corresponding threshold; a quantity of first DMRS and/or second DMRS that are expected to be included in the collected samples exceeds a corresponding threshold; and each of the one or more hypothesis testing exceeds a corresponding threshold.

9. The method of any of claims 7-8, further comprising, while the first SCell is activated before receiving the first command, receiving (1015) from the RAN node a first configuration for the physical control channel and associated first DMRS, wherein the hypothesis testing of collected samples corresponding to the first DMRS is based on the first configuration.

10. The method of any of claims 7-9, further comprising receiving (1005) from the RAN node an SCell configuration for the first SCell, wherein: the SCell configuration includes a second configuration of the physical data channel and the associated second DMRS; and the hypothesis testing of collected samples corresponding to the second DMRS is based on the second configuration.

11. The method of any of claims 6-10, further comprising demodulating (1080) at least a portion of the collected samples after synchronizing to the first SCell, including one or more of the following: demodulating (1082) the collected samples that correspond to the physical control channel to obtain downlink control information intended for the UE; and demodulating (1083) the collected samples that correspond to the physical data channel to obtain data intended for the UE.

12. The method of claim 11, wherein demodulating (1080) at least a portion of the collected samples further comprises applying (1081) timing and frequency offsets of the UE with respect to the first SCell, which were determined based on the first DMRS and/or the second DMRS, to the collected samples prior to demodulation.

13. The method of any of claims 11-12, wherein: the obtained downlink control information includes a scheduling message intended for the UE; the method further comprises sending (1090) an uplink message to the RAN node in response to the scheduling message; and a duration between the uplink message and one of the following is based on the synchronization maintained with the PCell while the first SCell was deactivated: the scheduling message; or the data intended for the UE, which is scheduled by the scheduling message.

14. The method of any of claims 2-13, wherein: the method further comprises, while the first SCell is activated before receiving the first command, estimating (1010) time and frequency offsets between the PCell and the first SCell; and synchronizing (1070) to the first SCell in response to the second command comprises: performing (1071) the fine synchronization with the first SCell when the estimated time and frequency offsets are greater than a threshold; and refraining (1072) from performing the fine synchronization with the first SCell when the estimated time and frequency offsets are not greater the threshold.

15. The method of any of claims 1-14, wherein deactivating (1030) the first SCell comprises selecting (1031) one of a plurality of available low-energy modes and operating in the selected low- energy mode.

16. The method of claim 15, wherein selecting (1031) one of the plurality of available low-energy modes is based on one or more of the following: one or more types or classes of data traffic recently received from the RAN node; an indication from the RAN mode of a minimum duration until reactivation of the first SCell; historical information about durations between RAN node deactivation and reactivation of SCells; a schedule for UE low-energy operation;

UE receiver architecture; and carrier frequencies of the PCell and SCells configured for the UE, including the first SCell.

17. The method of any of claims 15-16, wherein: the method further comprises sending (1020) to the RAN node an indication of a minimum required delay between the UE receiving a command to activate an SCell and the UE initiating synchronization to the SCell being activated, the indicated minimum required delay is based on the selected low-energy mode; and a duration between receiving (1050) the second command and initiating the synchronizing (1070) to the first SCell is at least the indicated minimum required delay.

18. The method of claim 17, wherein the indication is sent via the PCell after receiving the first command.

19. The method of claim 15, wherein: the method further comprises receiving (1025) from the RAN node an indication of a minimum delay between sending a command to activate an SCell and transmitting information to the UE via the SCell being activated; the low-energy mode is selected based on the indicated minimum delay; and a duration between receiving (1050) the second command and initiating the synchronizing (1070) to the first SCell is at least the indicated minimum delay.

20. A method performed by a radio access network, RAN, node configured to provide a primary serving cell, PCell, and at least a first secondary cell, SCell, to a user equipment, UE, the method comprising: while the first SCell is activated, sending (1140) to the UE a first command to deactivate the first SCell; subsequently sending (1150) a second command to activate the first SCell to the UE via the PCell or via a second SCell that is activated; and after sending (1150) the second command but before a next-scheduled transmission of a synchronization signal in the first SCell, transmitting (1170) one or more of the following information via the first SCell: a physical control channel carrying downlink control information intended for the UE, and a physical data channel carrying data intended for the UE.

21. The method of claim 20, wherein: the method further comprises maintaining (1145) synchronization with the UE via PCell while the first SCell is deactivated; and transmitting (1170) the information before the next-scheduled transmission of the synchronization signal is based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated.

22. The method of claim 21, wherein the transmitted information is arranged into one or more OFDM symbols, which include one or more of the following: the physical control channel and associated first demodulation reference signals, DMRS; and the physical data channel and associated second DMRS.

23. The method of claim 22, wherein at least one of the first DMRS and the second DMRS facilitates fine synchronization of the UE with the first SCell, based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated.

24. The method of claim 23, further comprising, while the first SCell is activated before sending the first command, sending (1110) to the UE a first configuration for the physical control channel and associated first DMRS, wherein fine synchronization of the UE with the first SCell is further based on the first configuration.

25. The method of any of claims 23-24, further comprising sending (1105) to the UE an SCell configuration for the first SCell, wherein: the SCell configuration includes a second configuration of the physical data channel and the associated second DMRS; and fine synchronization of the UE with the first SCell is further based on the second configuration.

26. The method of any of claims 21-25, wherein: the downlink control information includes a scheduling message intended for the UE; the method further comprises receiving (1180) an uplink message from the UE in response to the scheduling message; and a duration between the uplink message and one of the following is based on the synchronization maintained with the UE via the PCell while the first SCell was deactivated: the scheduling message; or the data intended for the UE, which is scheduled by the scheduling message.

27. The method of any of claims 20-26, further comprising one of the following: sending (1130) to the UE an indication of a minimum delay between sending a command to activate an SCell and transmitting information to the UE via the SCell being activated; and receiving (1120) from the UE an indication of a minimum required delay between the UE receiving a command to activate an SCell and the UE initiating synchronization to the SCell being activated.

28. The method of claim 27, wherein the duration between sending (1150) the second command and transmitting (1170) the information to the UE via the SCell is greater than or equal to the minimum delay indicated by the RAN node or the minimum required delay indicated by the UE.

29. The method of any of claims 27-28, wherein the indication is received from the UE via the PCell after sending the first command.

30. The method of any of claims 27-28, further comprising selecting (1125) the minimum delay indicated to the UE based on one or more of the following: one or more types or classes of data traffic recently transmitted to the UE; one or more low-energy operating modes available for the UE; historical information about durations between RAN node deactivation and reactivation of SCells; historical information about observed UE minimum required delay; one or more of the following UE characteristics: manufacturer, model, chipset supplier, chipset model, and software version; carrier frequencies of the PCell and SCells configured for the UE, including the first SCell; and observed UE Doppler frequency shift.

31. The method of any of claims 20-26, wherein: the physical control channel including the downlink control information is transmitted a first duration after sending the second command; the downlink control information includes a scheduling message for the data carried on the physical data channel; and the method further comprises, based on receiving no uplink message indicating that the UE received the data carried on the physical data channel, determining (1190) that the UE’s minimum required delay is greater than the first duration and retransmitting the physical control channel including the downlink control information a second duration after sending the second command.

32. The method of claim 31, further comprising selecting (1160) the first duration based on one or more of the following: one or more types or classes of data traffic recently transmitted to the UE; one or more low-energy operating modes available for the UE; historical information about durations between RAN node deactivation and reactivation of SCells; historical information about observed UE minimum required delay; one or more of the following UE characteristics: manufacturer, model, chipset supplier, chipset model, and software version; carrier frequencies of the PCell and SCells configured for the UE, including the first SCell; and observed UE Doppler frequency shift.

33. A user equipment, UE (205, 310, 1212, 1300) configured to communicate with a radio access network, RAN (199, 299, 1204) via a primary serving cell, PCell, and at least a first secondary cell, SCell, the UE comprising: communication interface circuitry (1312) configured to communicate with a RAN node (100, 150, 210, 220, 310, 1210, 1400, 1502); and processing circuitry (1302) operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to: while the first SCell is activated, deactivate the first SCell in response to receiving from the RAN node a first command to deactivate the first SCell; subsequently receive a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated; and synchronize to the first SCell in response to the second command and without receiving any synchronization signals transmitted in the first SCell.

34. The UE of claim 33, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to any of the methods of claims 2-19.

35. A user equipment, UE (205, 310, 1212, 1300) configured to communicate with a radio access network, RAN (199, 299, 1204) via a primary serving cell, PCell, and at least a first secondary cell, SCell, the UE being further configured to: while the first SCell is activated, deactivate the first SCell in response to receiving from a RAN node (100, 150, 210, 220, 310, 1210, 1400, 1502) a first command to deactivate the first SCell; subsequently receive a second command to activate the first SCell from the RAN node via the PCell or via a second SCell that is activated; and synchronize to the first SCell in response to the second command and without receiving any synchronization signals transmitted in the first SCell.

36. The UE of claim 35, being further configured to perform operations corresponding to any of the methods of claims 2-19.

37. A non-transitory, computer-readable medium (1310) storing computer-executable instructions that, when executed by processing circuitry (1302) of a user equipment, UE (205, 310, 1212, 1300) configured to communicate with a radio access network, RAN (199, 299, 1204) via a primary serving cell, PCell, and at least a first secondary cell, SCell, the UE, configure the UE to perform operations corresponding to any of the methods of claims 1-19.

38. A computer program product (1314) comprising computer-executable instructions that, when executed by processing circuitry (1302) of a user equipment, UE (205, 310, 1212, 1300) configured to communicate with a radio access network, RAN (199, 299, 1204) via a primary serving cell, PCell, and at least a first secondary cell, SCell, the UE, configure the UE to perform operations corresponding to any of the methods of claims 1-19.

39. A radio access network, RAN, node (100, 150, 210, 220, 310, 1210, 1400, 1502) configured to provide a primary serving cell, PCell, and at least a first secondary cell, SCell, to a user equipment, UE (205, 310, 1212, 1300), the RAN node comprising: communication interface circuitry (1406, 1504) configured to communicate with the UEs; and processing circuitry (1402, 1504) operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to: while the first SCell is activated, send to the UE a first command to deactivate the first SCell; subsequently send a second command to activate the first SCell to the UE via the PCell or via a second SCell that is activated; and after sending the second command but before a next-scheduled transmission of a synchronization signal in the first SCell, transmit one or more of the following information: a physical control channel carrying downlink control information intended for the

UE, and a physical data channel carrying data intended for the UE.

40. The RAN node of claim 39, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to any of the methods of claims 21- 32.

41. A radio access network, RAN, node (100, 150, 210, 220, 310, 1210, 1400, 1502) configured to provide a primary serving cell, PCell, and at least a first secondary cell, SCell, to a user equipment, UE (205, 310, 1212, 1300), the RAN node being further configured to: while the first SCell is activated, send to the UE a first command to deactivate the first SCell; subsequently send a second command to activate the first SCell to the UE via the PCell or via a second SCell that is activated; and after sending the second command but before a next-scheduled transmission of a synchronization signal in the first SCell, transmit one or more of the following information: a physical control channel carrying downlink control information intended for the UE, and a physical data channel carrying data intended for the UE.

42. The RAN node of claim 41, being further configured to perform operations corresponding to any of the methods of claims 21-32.

43. A non-transitory, computer-readable medium (1404, 1504) storing computer-executable instructions that, when executed by processing circuitry (1402, 1504) of a radio access network, RAN, node (100, 150, 210, 220, 310, 1210, 1400, 1502) configured to provide a primary serving cell, PCell, and at least a first secondary cell, SCell, to a user equipment, UE (205, 310, 1212, 1300), configure the RAN node to perform operations corresponding to any of the methods of claims 20-32.

44. A computer program product (1404a, 1504a) comprising computer-executable instructions that, when executed by processing circuitry (1402, 1504) of a radio access network, RAN, node (100, 150, 210, 220, 310, 1210, 1400, 1502) configured to provide a primary serving cell, PCell, and at least a first secondary cell, SCell, to a user equipment, UE (205, 310, 1212, 1300), configure the RAN node to perform operations corresponding to any of the methods of claims 20-32.