EP4649629A2 - Ssb-less mobility for network energy saving - Google Patents

Abstract

Disclosed are methods, systems, apparatuses, and computer programs to execute method for performing a RRM operation using an SSB-less SCell. In one aspect, the method can include determining, by a UE, that a target SCell is an SSB-less SCell, determining, by the UE, a reference serving cell for the target SCell, and performing, by the UE, a RRM operation in the target SCell based on a reference signal of the reference serving cell.

Description

SSB-LESS MOBILITY FOR NETWORK ENERGY SAVING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Prov. App. No. 63/446,410, filed on February 17, 2023, entitled “SSB-LESS MOBILITY FOR NETWORK ENERGY SAVING”, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Wireless communication networks provide integrated communication platforms and telecommunication services to wireless user devices. Example telecommunication services include telephony, data (e.g., voice, audio, and/or video data), messaging, and/or other services. The wireless communication networks have wireless access nodes that exchange wireless signals with the wireless user devices using wireless network protocols, such as protocols described in various telecommunication standards promulgated by the Third Generation Partnership Project (3GPP). Example wireless communication networks include time division multiple access (TDMA) networks, frequency -division multiple access (FDMA) networks, orthogonal frequency-division multiple access (OFDMA) networks, Long Term Evolution (LTE), and Fifth Generation New Radio (5G NR). The wireless communication networks facilitate mobile broadband service using technologies such as OFDM, multiple input multiple output (MIMO), advanced channel coding, massive MIMO, beamforming, and/or other features.

SUMMARY

[0003] In accordance with one aspect of the present disclosure, a method for performing a radio resource management (RRM) operation using an SSB-less SCell is disclosed. In one aspect, the method can include determining, by a UE, that a target SCell is an SSB-less SCell, determining, by the UE, a reference serving cell for the target SCell, and performing, by the UE, a RRM operation in the target SCell based on a reference signal of the reference serving cell. Generally, RRM operations can rely on reference signals for various purposes, including power control, scheduling, cell search, cell reselection, handover, radio link or connection monitoring, and connection establishment and re-establishment. The RRM operations are particularly important for carrier aggregation (CA) use-cases, where component carriers (CC) from different frequency bands and from different serving cells. This disclosure describes activation of an inter-band SSB-less SCell based on alternatives to the SCell’s SSB for RRM operations.

[0004] Other aspects includes apparatuses, systems, and computer programs for performing the actions of the aforementioned method.

[0005] The innovative method can include other optional features. For example, in some implementations, determining a reference serving cell for the target SSB-less SCell can include selecting, by the UE, a reference serving cell on the closest band or carrier relative to the band or carrier of the SSB-less SCell.

[0006] In some implementations, the closest band relative to the band or carrier of the SSB- less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

[0007] In some implementations, the method further includes receiving, by the UE, signaling from an access node, that configures a reference serving cell indexes to SSB-less SCell when adding an SSB-less SCell to the UE. In such implementations, determining a reference serving cell for the target SSB-less SCell can include selecting, by the UE, a reference serving cell based on the reference service cell index.

[0008] In some implementations, the method can further include determining, by the UE, a type of the reference signal used by the reference serving cell.

[0009] In some implementations, the method can further include based on a determination, by the UE, that the reference signal used by the reference serving cell is an SSB reference signal, selecting, by the UE, the SSB reference signal as a reference signal for use in the performance of the RRM operation in the SSB-less SCell.

[0010] In some implementations, the method can further include receiving, by the UE, signaling from an access node, that configures one or multiple SSB indexes of a reference serving cell for use with the SSB-less SCell when adding the SSB-less SCell to the UE. In such implementations, determining a reference serving cell for the target SSB-less SCell can include selecting, by the UE, the one or more multiple SSB of the reference serving cell indicated by the SSB index as a reference signal, for use in the performance of the RRM operation in the SSB-less SCell.

[0011] In some implementations, the method can further include based on a determination, by the UE, that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CSI-RS), selecting, by the UE, the TRS or CSI-RS as the reference signal for use in the performance of the RRM operation in the SSB- less SCell.

[0012] In some implementations, the selected TRS is active TRS and the selected CSI-RS is semi-persistent (SP) or periodic CSI-RS.

[0013] In some implementations, the method can further include receiving, by the UE, signaling from an access node, that configures one or multiple CSI-RS indexes of a reference service cell for the SSB-less SCell when adding an SSB-less SCell to the UE. In such implementations, determining a reference serving cell for the target SSB-less SCell can include selecting, by the UE, the CSI-RS as a reference signal, based on the CSI-RS index, for use in the performance of the RRM operation in the SSB-less SCell.

[0014] In some implementations, the selected CSI-RS is semi-persistent (SP) or periodic CSI- RS

[0015] In some implementations, the RRM operation can include (i) L3 measurement for the target SSB-less SCell, (ii) activation of the target SSB-less SCell, (iii) time and frequency tracking (T/F tracking), or (iv) (AGC) estimation.

[0016] In accordance with another innovative aspect of the present disclosure, a method for performing a RRM operation using an SSB-less SCell is disclosed. In one aspect, the method can include receiving, by a UE, a channel state information reference signal (CSI-RS) from an access node of a target SSB-less SCell, and performing, by the UE, a RRM operation in the target SSB-less SCell using the received CSI-RS.

[0017] Other aspects includes apparatuses, systems, and computer programs for performing the actions of the aforementioned method.

[0018] The innovative method can include other optional features. For example, in some implementations, where the CSI-RS is within the active bandwidth of the target SSB-less SCell.

[0019] In some implementations, receiving, by the UE, CSI-RS from the access node of the target SSB-less SCell can include receiving, by the UE and from the access node of an active serving cell, CSI-RS time offset, periodicity, and signal bandwidth.

[0020] In some implementations, the CSI-RS is associated with an SSB from a reference serving cell.

[0021] In some implementations, the CSI-RS is associated with a reference serving cell.

[0022] In some implementations, the reference serving cell is determined by the UE selecting a reference serving cell on the closest band or carrier relative to the band or carrier of the SSB- less SCell.

[0023] In some implementations, the closest band relative to the band or carrier of the SSB- less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

[0024] In some implementations, the reference serving cell is determined by the UE receiving signaling, from an access node, that configures a reference serving cell index to SSB-less SCell when adding an SSB-less SCell to the UE.

[0025] In some implementations, the RRM operation comprises (i) L3 measurement for the target SSB-less SCell or (ii) activation of the target SSB-less SCell.

[0026] In some implementations, the CSI-RS is Quasi Collocated (QCLed) with another reference signal from the reference serving cell.

[0027] In some implementations, the QCLed is QCLed type A.

[0028] In some implementations, the QCLed type A comprises Doppler shift, Doppler spread, average delay, delay spread, and received absolute timing for inter-band CA.

[0029] In some implementations, the QCLed is QCLed type C. [0030] In some implementations, the QCLed type C comprises Doppler shift, average delay, and received absolute timing for inter-band CA.

[0031] In accordance with another innovative aspect of the present disclosure, a method for performing an RRM operation using an SSB-less SCell is disclosed. In one aspect, the method can include determining, by a UE, a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell and (ii) a reference signal strength indicator (RSSI) or interference measurement of a different serving cell than the reference serving cell, and performing, by the UE, a RRM operation in the target SSB-less SCell using the determined measurement of the reference signal of the target SSB-less SCell.

[0032] Other aspects includes apparatuses, systems, and computer programs for performing the actions of the aforementioned method.

[0033] The innovative method can include other optional features. For example, in some implementations, the measurement of the reference signal of the target SSB-less SCell is reference signal received quality (RSRQ) measurement or SINR measurement of the SSB-less SCell.

[0034] In some implementations, the different serving cell is the SSB-less SCell.

[0035] In some implementations, the method can further include determining, by the UE, a type of the reference signal used by the reference serving cell.

[0036] In some implementations, determining, by the UE, a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell can include based on a determination, by the UE, that the reference signal used by the reference serving cell is an SSB reference signal, determining, by the UE, the RSRP of the SSB reference signal in the reference serving cell.

[0037] In some implementations, determining, by the UE, a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell can include based on a determination, by the UE, that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CS1-RS), determining, by the UE, the RSRP measurement of the TRS reference signal in the reference serving cell or the CSI-RS reference signal in the reference serving cell. [0038] In some implementations, the method can further include receiving, by the UE, signaling from the access node that configured the UE with an interference measurement resource (IMR) or channel measurement resource (CMR) for the SSB-less SCell.

[0039] In some implementations, the IMR and CMR can be configured as reference signals on SSB-less SCell and other active serving cells.

[0040] In accordance with another innovative aspect of the present disclosure, a method for performing an RRM operation in an SSB-less SCell is disclosed. In one aspect, the method can include receiving, by the UE, signaling from an access node of an SSB-less SCell, wherein the received signaling preconfigures the UE with SSB periodicity and SSBinBurst for the SSB- less SCell, and receiving, by the UE, different signaling that triggers performance of the RRM operation in the SSB-less SCell.

[0041] Other aspects includes apparatuses, systems, and computer programs for performing the actions of the aforementioned method.

]0042| The innovative method can include other optional features. For example, in some implementations, the received signaling is SP-SSB and the received different signaling is a MAC-CE that activates or deactivates the SSB.

[0043] In some implementations, the received signaling is AP-SSB and the received different signaling is downlink control information (DO) that a-periodically indicates to the UE to perform the RRM operation.

[0044] In some implementations, the RRM operation is T/F tracking.

[0045] In some implementations, the RRM operation is AGC estimation.

[0046] In some implementations, the AGC is RSSI based AGC on the SSB-less SCell.

[0047] In some implementations, the RSSI is measured based on the total power within the initial bandwidth part of SSB-less SCell, the total power within the active bandwidth part of SSB-less SCell, or the total power within a first active bandwidth part of SSB-less SCell.

[0048] The details of one or more embodiments of these systems and methods are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of these systems and methods will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE FIGURES

[0049] FIG. 1 illustrates a wireless network, according to some implementations.

[0050] FIG. 2 illustrates a flowchart of an example of a process for performing radio resource management (RRM) operations in an SSB-less SCell, according to some implementations.

[0051] FIG. 3 illustrates an example of an information element that can be used to configure a reference serving cell index to SSB-less SCell, according to some implementations.

[0052] FIG. 4 illustrates a flowchart of an example of another process for performing RRM operations in an SSB-less SCell based on a channel state information reference signal (CSI- RS) associated with the SSB-less SCell, according to some implementations.

[0053] FIG. 5 illustrates a flowchart of an example of another process for performing RRM operations in an SSB-less SCell based on measuring an SSB-less SCell reference signal received quality (RSRQ) or signal to interference plus noise ratio (SINR) using a reference signal received power (RSRP) and reference signal strength indicator (RSSI) from different serving cells, according to some implementations.

[0054] FIG. 6 illustrates a flowchart of an example of another process for performing RRM operations in an SSB-less SCell using a UE that is (pre)configured by an access node of an SSB-less SCell with an SSB periodicity and SSB inBurst, according to some implementations.

[0055] FIG. 7 illustrates an example user equipment (UE), according to some implementations.

[0056] FIG. 8 illustrates an example access node, according to some implementations.

DETAILED DESCRIPTION

[0057] The present disclosure is directed towards SSB-less radio resource management (RRM) for network energy savings. In an SSB-less SCell, an access node is not broadcasting Synchronization Signal Blocks (SSB) that can be used by user equipment (UE) to perform measurements for mobility operations such as cell selection, cell reselection, power control calculations, mobility procedures, and beam management. Power savings are achieved in SSB- less serving cells, as less power is consumed when the access node is not broadcasting SSB blocks. The present disclosure provides systems, methods, devices, and computer programs for enabling performing of RRM operations, including mobility operations, by a UE in the absence of SSB transmissions in SSB-less SCells.

[0058] In some implementations, methods for L3 measurement on an SSB-less SCell are disclosed. Generally, when operating in an SSB-less SCell, a UE can use alternatives to SSB to at least partially determine measurements for mobility operations, including measurements pertaining to time or frequency synchronization, LI or L3 measurements, for automatic gain control. By using alternatives to SSB, the UE can perform inter-band carrier aggregation using an SSB-less SCell with at least some indication of channel quality and synchronization. These methods can include, for example, (i) using SSB for L3 or mobility measurement on another serving cell for the SSB-less SCell, (ii) using CSLRS for L3 or mobility measurement on SSB- less SCell, and (iii) using RSRQ with RSRP and RSSI on different cells, or using interference resource concept for L3 measurement. In some implementations, methods for timing and frequency (T/F) tracking on an SSB-less SCell is disclosed. These methods can include, for example, (i) using Tracking Reference Signal (TRS) or SSB or CSI-RS from other serving cell for T/F tracking in an SSB-less SCell or (ii) using aperiodic (AP)-SSB for SSB-less SCell or CSI-RS/TRS on SSB-less SCell. In some implementations, methods for automatic gain control (AGC) on an SSB-less SCell are disclosed. These methods can include, for example, (i) using an SSB or CSI-RS from another serving cell, (ii) using RSSI based AGC on SSB-less SCell, and (iii) using AP-SSB for SSB-less SCell or CSI-RS/TRS on SSB-less SCell.

[0059] For purposes of this disclosure, an SCell is a secondary cell in carrier aggregation (CA) or dual connectivity (DC). More generally, a serving cell such as reference serving cell can be a PCell, PSCell (in DC), or an SCell (in CA or DC).

[0060] FIG. 1 illustrates a wireless network 100, according to some implementations. The wireless network 100 includes a UE 102 and a base station 104 connected via one or more channels 106A, 106B across an air interface 108. The UE 102 and base station 104 communicate using a system that supports controls for managing the access of the UE 102 to a network via the base station 104.

[0061] In some implementations, the wireless network 100 may be a Non-Standalone (NSA) network that incorporates Long Term Evolution (LTE) and Fifth Generation (5G) New Radio (NR) communication standards as defined by the Third Generation Partnership Project (3GPP) technical specifications. For example, the wireless network 100 may be a E-UTRA (Evolved Universal Terrestrial Radio Access)-NR Dual Connectivity (EN-DC) network, or an NR- EUTRA Dual Connectivity (NE-DC) network. In some other implementations, the wireless network 100 may be a Standalone (SA) network that incorporates only 5G NR. Furthermore, other types of communication standards are possible, including future 3GPP systems (e.g., Sixth Generation (6G)), Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology (e.g., IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11- 2007; IEEE 802. l ln; IEEE 802.11-2012; IEEE 802.11ac; or other present or future developed IEEE 802.11 technologies), IEEE 802.16 protocols (e.g., WMAN, WiMAX, etc.), or the like. While aspects may be described herein using terminology commonly associated with 5G NR, aspects of the present disclosure can be applied to other systems, such as 3G, 4G, and/or systems subsequent to 5G (e.g., 6G).

[0062] In the wireless network 100, the UE 102 and any other UE in the system may be, for example, any of laptop computers, smartphones, tablet computers, machine-type devices such as smart meters or specialized devices for healthcare, intelligent transportation systems, or any other wireless device. In network 100, the base station 104 provides the UE 102 network connectivity to a broader network (not shown). This UE 102 connectivity is provided via the air interface 108 in a base station service area provided by the base station 104. In some implementations, such a broader network may be a wide area network operated by a cellular network provider, or may be the Internet. Each base station service area associated with the base station 104 is supported by one or more antennas integrated with the base station 104. The service areas can be divided into a number of sectors associated with one or more particular antennas. Such sectors may be physically associated with one or more fixed antennas or may be assigned to a physical area with one or more tunable antennas or antenna settings adjustable in a beamforming process used to direct a signal to a particular sector. [0063] The UE 102 includes control circuitry 110 coupled with transmit circuitry 112 and receive circuitry 114. The transmit circuitry 112 and receive circuitry 114 may each be coupled with one or more antennas. The control circuitry 110 may include various combinations of application-specific circuitry and baseband circuitry. The transmit circuitry 112 and receive circuitry 114 may be adapted to transmit and receive data, respectively, and may include radio frequency (RF) circuitry and/or front-end module (FEM) circuitry.

[0064] In various implementations, aspects of the transmit circuitry 112, receive circuitry 114, and control circuitry 110 may be integrated in various ways to implement the operations described herein. The control circuitry 110 may be adapted or configured to perform various operations, such as those described elsewhere in this disclosure related to a UE. For instance, the control circuitry 110 can include performance of operations such operations 210, 220, 230 of FIG. 2, operation 420 of FIG. 4, operations 510, 520 of FIG. 5, and operations 610, 620 of FIG. 6.

[0065] The transmit circuitry 112 can perform various operations described in this specification. Additionally, the transmit circuitry 112 may transmit using a plurality of multiplexed uplink physical channels. The plurality of uplink physical channels may be multiplexed, e.g., according to time division multiplexing (TDM) or frequency division multiplexing (FDM) along with carrier aggregation. The transmit circuitry 1 12 may be configured to receive block data from the control circuitry 110 for transmission across the air interface 108.

[0066] The receive circuitry 114 can perform various operations described in this specification. For instance, the receive circuitry 114 can perform receive operations such as operations 410 of FIG. 4 and receive operations 610, 620 of FIG. 6. Additionally, the receive circuitry 114 may receive a plurality of multiplexed downlink physical channels from the air interface 108 and relay the physical channels to the control circuitry 110. The plurality of downlink physical channels may be multiplexed, e.g., according to TDM or FDM along with carrier aggregation. The transmit circuitry 112 and the receive circuitry 114 may transmit and receive, respectively, both control data and content data (e.g., messages, images, video, etc.) structured within data blocks that are carried by the physical channels.

[0067] FIG. 1 also illustrates the base station 104. In some implementations, the base station 104 may be a 5G radio access network (RAN), a next generation RAN, a E-UTRAN, a nonterrestrial cell, or a legacy RAN, such as a UTRAN. As used herein, the term “5G RAN” or the like may refer to the base station 104 that operates in an NR or 5G wireless network 100, and the term “E-UTRAN” or the like may refer to a base station 104 that operates in an LTE or 4G wireless network 100. The UE 102 utilizes connections (or channels) 106 A, 106B, each of which includes a physical communications interface or layer.

[0068] The base station 104 circuitry may include control circuitry⁷ 116 coupled wi th transmit circuitry 118 and receive circuitry 120. The transmit circuitry 118 and receive circuitry⁷ 120 may each be coupled with one or more antennas that may be used to enable communications via the air interface 108. The transmit circuitry 118 and receive circuitry 120 may be adapted to transmit and receive data, respectively, to any UE connected to the base station 104. The receive circuitry 120 may receive a plurality of uplink physical channels from one or more UEs, including the UE 102.

[0069] In FIG. 1, the one or more channels 106 A, 106B are illustrated as an air interface to enable communicative coupling, and can be consistent with cellular communications protocols, such as a UMTS protocol, a 3GPP LTE protocol, an Advanced long term evolution (LTE-A) protocol, a LTE-based access to unlicensed spectrum (LTE-U), a 5G protocol, a NR protocol, an NR-based access to unlicensed spectrum (NR-U) protocol, and/or any other communications protocol(s). In implementations, the UE 102 may directly exchange communication data via a ProSe interface. The ProSe interface may alternatively be referred to as a sidelink (SL) interface and may include one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

Radio Resource Management (RRM) Operations for SSB-Less SCells

[0070] Systems, methods, devices, and computer programs for L3 measurement and SCell activation for inter-band SSB-less SCell is disclosed. This disclosure describes how L3 measurements can be taken when attempting to activate an SCell for carrier aggregation using inter-band component carriers in a situation where the SCell is an SSB-less SCell.

[0071] In some implementations, a UE is configured to use a reference signal (RS) of another serving cell (e.g., a reference serving cell) for L3 or mobility measurement or SCell activation for SSB-less SCell, and the UE can determine which RS of which serving cell can be used for such purpose based on following methods. [0072] The UE can determine a ‘‘reference serving cell” for target SSB-less SCell in a number of different ways. In a first implementations, the UE can choose the reference serving cell on the closest or adjacent band/carrier compared with the band/carrier of SSB-less SCell.

[0073] Alternatively, in other implementations, the network (e.g., access node of SSB-less SCell) can configure the reference serving cell index for the SSB-less SCell when adding this SSB-less SCell to the UE. The reference serving cell index indicates which serving cell the UE can use as a reference serving cell. An example of an information element IE 300 that can be used to configure the reference serving cell index to SSB-less SCell is shown in FIG. 3. The IE 300 includes a parameter “refCelllndex” 310 that can be used to indicate the reference serving cell index to SSB-less SCell to the UE, e.g., when no SMTC and SSB is configured to this SCell.

[0074] A UE can determine a reference signal (RS) of the reference serving cell in a number of different ways. For example, in some implementations, if SSB is used for the RS, then the UE can choose the SSB of the reference serving cell - especially for L3 measurement. In such instances, the measurement configuration of SSB for the reference serving cell can be kept for target SSB-less SCell. That is, the measurement configuration of SSB for the identified or selected reference serving cell is used for the SSB-less SCell that the UE will connect to. Measurement configuration parameters of an SSB can include, for example, nrofSS- BlocksTo Av erage and measurement/report with/without SSB index.

[0075] In some implementations, if SSB of a reference serving cell is used for the RS, the network can indicate the one or multiple SSB indexes of the selected or identified reference serving cell when adding the SSB-less SCell to the UE. The UE uses these indicated SSBs of reference cell for L3 measurement and SCell activation for connecting to and using the target SSB-less SCell.

[0076] In some implementations, if TRS or CSI-RS is used for the reference signal (RS), then a UE chooses TRS of a selected or identified reference serving cell for target SSB-less SCell activation and/or operation if TRS is configured on that reference serving cell, and active TRS is always prioritized to be used.

[0077] In some implementations, if TRS or CSI-RS is used, then the network (e.g., access node of the reference cell) can indicate the one or multiple CSI-RS indexes of a reference serving cell when adding a target SSB-less SCell to UE. In such implementations, only semi -persistent (SP) and/or periodic CSI-RS may be used in this case. [0078] FIG. 2 illustrates a flowchart of an example of a process 200 for performing RRM operations in an SSB-less SCell, according to some implementations. For convenience, the process 200 will be described as being performed by a UE such as a UE 102 or UE 700.

[0079] A UE can begin execution of process 200 by determining that a target SCell is an SSB- less SCell (210).

[0080] The UE can continue execution of the process 200 by determining a reference serving cell for the target SSB-less SCell (220). In some implementations, determining a reference serving cell for the target SSB-less SCell at stage 220 can include the UE selecting a reference serving cell on the closest band or earner relative to the band or carrier of the SSB-less SCell. In some implementations, the closest band relative to the band or carrier of the SSB-less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

[0081] Alternatively, in some implementations, execution of the process 200 can include the UE receiving signaling from an access node, that configures a reference serving cell index identifying a reference serving cell that can be used for one or more RRM measurements with SSB-less SCell when adding an SSB-less SCell to the UE. In such implementations, determining a reference serving cell for the target SSB-less SCell at stage 220 can include the UE selecting a reference serving cell based on the reference service cell index.

[0082] The UE can continue execution of the process 200 by performing a RRM operation in the target SSB-less SCell based on a reference signal of the reference serving cell. In some implementations, the RRM operation can include (i) L3 measurement for the target SSB-less SCell, (ii) activation of the target SSB-less SCell, (iii) time and frequency tracking (T/F tracking), or (iv) (AGC) estimation.

[0083] In some implementations, the UE can continue execution of the process 200 by determining, by the UE, a type of the reference signal used by the reference serving cell. In some implementations, based on a determination, by the UE, that the reference signal used by the reference serving cell is an SSB reference signal, the UE can continue execution of the process 200 by selecting the SSB reference signal as a reference signal for use in the performance of the RRM operation in the SSB-less SCell.

[0084] In some implementations, the UE can receive signaling from an access node, that configures one or multiple SSB indexes of a reference serving cell for use by the UE when adding the SSB-less SCell to the UE. In such implementations, the determining of a reference serving cell for the target SSB-less SCell at stage 220 can include the UE selecting the one or more multiple SSB of the reference sendee indicated by the SSB index as a reference signal, based on the CSI-RS index, for use in the performance of the RRM operation in the SSB-less SCell.

[0085] In some implementations, based on a determination, by the UE, that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CSI-RS), the UE can continue execution of the process 200 by selecting the TRS or CSI-RS as the reference signal for use in the performance of the RRM operation in the SSB-less SCell. In some implementation, priority may be given to the selection of the TRS reference signal over the CSI-RS reference signal.

[0086] In some implementations, the selected TRS is active TRS and the selected CSI-RS is semi-persistent (SP) or periodic CSI-RS.

[0087] In some implementations, the UE can receive signaling from an access node, that configures one or multiple CSI-RS index of a reference service cell for the SSB-less SCL when adding an SSB-less SCell to the UE. In such implementations, determining a reference serving cell for the target SSB-less SCell at stage 220 can include the UE selecting the CSI-RS as a reference signal, based on the CSI-RS index, for use in the performance of the RRM operation in the SSB-less SCell. In such implementations, the selected CSI-RS is semi-persistent (SP) or periodic CSI-RS.

[0088] FIG. 3 illustrates an example of an information element 300 that can be used to configure a reference serving cell index to SSB-less SCell, according to some implementations. For convenience, the process 300 will be described as being performed by a UE such as a UE 102 or UE 700.

[0089] RRM Operations for SSB-Less SCells Using CSI-RS

[0090] Systems, methods, devices, and computer programs for L3 measurement and SCell activation for inter-band SSB-less SCell is disclosed.

[0091] In some implementations, for L3 or other RRM measurements only, aUE can use CSI- RS for L3 or mobility measurement of a reference serving cell for the SSB-less SCell. The CSI-RS is in the bandwidth (BW) of target SSB-less SCell and CSI-RS information is configured for the UE when adding this SSB-less SCell, e g., CSI-RS time offset, periodicity and signal BW. [0092] In some implementations, the CSI-RS may have an associated SSB on a reference serving cell; the reference serving cell selection can be based on a reference serving cell having the closest or adjacent band compared with the band of the SSB-less SCell, and the associated SSB index of reference serving cell is configured by network; or

[0093] In some implementations, the CSI-RS may associate with a reference serving cell directly; the reference serving cell selection can be based on a refCelllndex information element being configured to indicate the reference serving cell; or

[0094] In some implementations, the CSI-RS may QCLed with another RS on a reference serving cell, e g., QCLed type A or C. The legacy QCLed type A or C shall be enhanced in this case to reflect the absolute time difference.

[0095] For example, legacy 'typeA' can include: {Doppler shift, Doppler spread, average delay, delay spread} — > new typeA {Doppler shift, Doppler spread, average delay, delay spread, Received Absolute Timing for inter-band CA}; and legacy 'typeC can include : {Doppler shift, average delay} — > new typeC {Doppler shift, average delay. Received Absolute Timing for inter-band CA}.

[0096] FIG. 4 illustrates a flowchart of an example of another method 400 for performing RRM operations in an SSB-less SCell based on a channel state information reference signal (CSI- RS) associated with the SSB-less SCell, according to some implementations. For convenience, the process 400 will be described as being performed by a UE such as a UE 102 or UE 700.

[0097] A UE can begin execution of the process 400 by receiving a channel state information reference signal (CSI-RS) from an access node of a target SSB-less SCell (410). In some implementations, receiving at stage 410 the CSI-RS from the access node of the target SSB- less SCell can include the UE receiving, from the access node of an active serving cell . CSI- RS time offset, periodicity, and signal bandwidth.

[0098] The UE can continue execution of the process 400 by performing a RRM operation in the target SSB-less SCell using the received CSI-RS (420).

[0099] In some implementations, the CSI-RS is within the active bandwidth of the target SSB- less SCell.

[0100] In some implementations, the CSI-RS is associated with an SSB from a reference serving cell. In some implementations, the CSI-RS is associated with the SSB if the CSI-RS timing can be referred to SSB timing of the reference serving cell. Once a UE detects this association, the UE can directly use SSB timing to locate the symbols of CSI-RS and then perform measurement on CSI-RS.

[0101] In some implementations, the CSI-RS is associated with a reference serving cell. In some implementations, the CSI-RS is associated with a reference serving cell if the CSI-RS timing can be referred to the reference service cell’s timing.

[0102] In some implementations, the reference serving cell is determined by the UE selecting a reference serving cell on the closest band or carrier relative to the band or carrier of the SSB- less SCell.

[0103] In some implementations, the closest band relative to the band or carrier of the SSB- less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

[0104] In some implementations, the reference serving cell is determined by the UE receiving signaling, from an access node, that configures a reference serving cell index to SSB-less SCell when adding an SSB-less SCell to the UE.

[0105] In some implementations, the RRM operation comprises (i) L3 measurement for the target SSB-less SCell or (ii) activation of the target SSB-less SCell.

[0106] In some implementations, the CSI-RS is Quasi Collocated (QCLed) with another reference signal from the reference serving cell. In some implementations, the QCLed is QCLed type A. In such implementations, QCLed type A can include a Doppler shift, Doppler spread, average delay, delay spread, and received absolute timing for inter-band CA. In some implementations, the QCLed is QCLed type C. In such implementations, QCLed ty pe C can include Doppler shift, average delay, and received absolute timing for inter-band CA.

[0107] RRM Operations for SSB-Less SCells Based on Measurements of the SSB-Less SCells RSRP

[0108] In some implementations, for RSRQ or SINR measurement of target SSB-less SCell, the RSRP is measured based on a RS on a reference serving cell and RSSI/interference measurement is on this target SSB-less SCell without any specific RS. The RS and reference serving cell selection is based on option 1. [0109] In some implementations, for L3 RSRQ or SINR measurement, UE to measure target SSB-less SCell RSRQ or SINR with RSRP and RSSI on different serving cells, or use interference resource concept for L3.

[0110] In some implementations, the network configures CMR and IMR for SSB-less SCell RSRQ or SINR measurement. CMR is channel measurement resource and IMR is interference measurement resource. CMR and IMR can be configured on different serving cells and different RSs

[0111] FIG. 5 illustrates a flowchart of an example of another method 500 for performing RRM operations in an SSB-less SCell based on measuring an SSB-less SCell reference signal received quality (RSRQ) or signal to interference plus noise ratio (SINR) using a reference signal received power (RSRP) and reference signal strength indicator (RSSI) from different serving cells, according to some implementations. For convenience, the process 500 will be described as being performed by a UE such as a UE 102 or UE 700.

[0112] A UE can begin execution of the process 500 by determining a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell and (ii) a reference signal strength indicator (RSSI) or interference measurement of a different serving cell than the reference serving cell (510).

[0113] The UE can continue execution of the process s 500 by performing a RRM operation in the target SSB-less SCell using the determined measurement of the reference signal of the target SSB-less SCell.

[0114] In some implementations, the measurement of the reference signal of the target SSB- less SCell is RSRQ measurement or SINR measurement of the SSB-less SCell.

[0115] In some implementations, the different serving cell is the SSB-less SCell.

[0116] In some implementations, the UE can continue execution of the process 500 by determining a type of the reference signal used by the reference serving cell.

[0117] In some implementations, determining, by the UE, a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell can include based on a determination, by the UE, that the reference signal used by the reference serving cell is an SSB reference signal, determining, by the UE, the RSRP of the SSB reference signal in the reference serving cell.

[0118] In some implementations, determining, by the UE. a measurement of a reference signal of a target SSB-less SCell based on (i) a reference signal received power (RSRP) of a reference signal in a reference serving cell can include based on a determination, by the UE, that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CSI-RS), determining, by the UE, the RSRP measurement of the TRS reference signal in the reference serving cell or the CSI-RS reference signal in the reference serving cell. In some implementation, priority may be given to the selection of the TRS reference signal over the CSI-RS reference signal.

[0119] In some implementations, the UE can continue execution of the process 500 by receiving signaling from the access node that configured the UE with an interference measurement resource (IMR) or channel measurement resource (CMR) for the SSB-less SCell.

[0120] In some implementations, IMR and CMR can be configured as reference signals on SSB-less SCell and other active serving cells.

[0121] RRM Operations for SSB-Less SCells Using a UE (Pre)Configured With SSB periodicity and SSB inBurst

[0122] In some implementations, time and frequency (T/F) tracking for inter-band SSB-less SCell. In some implementations, the UE has no intra-band serving CC of target SSB-less SCell.

[0123] In some implementations, the UE can perform T/F tracking on an SSB-less SCell using implementations of the process 200 described with reference to FIG. 2. In other implementations, the network configures semi-persistent (SP) or AP-SSB on the SSB-less SCell,. In such implementations, SP-SSB means network preconfigure SSB periodicity and SSBinBurst to UE for the SSB-less SCell and use MAC-CE to activate and de-activate the SSB for UE to do T/F tracking. Alternatively, AP-SSB means network preconfigures SSB periodicity⁷ and SSBinBurst to UE for the SSB-less SCell and use DCI to aperiodically indicate UE to do T/F tracking

[0124] UE will use the next available AP-SSB occasion for T/F tracking after DCI. If the time interval between DCI and next closest SSB occasion is smaller than a threshold, UE will use the SSB occasion after next closest SSB occasion, as AP-SSB. [0125] In some implementations, AGC estimation can be implemented on inter-band SSB-less SCell. In some implementations, the UE has no intra-band serving CC of target SSB-less SCell.

[0126] In some implementations, the UE can perform ACG estimation using a RS from another serving cell, like the implementation described with reference to process 200 of FIG. 2 above for L3 measurement.

[0127] In some implementations, a network can configure a UE using SP/AP-SSB of SSB-less SCell in the same manner described for T/F tracking above. In other implementations, a UE can use RSSI based AGC on SSB-less SCell. In some implementations, RSSI is measured based on the total power within the initial BWP or active BWP or first active BWP.

[0128] FIG. 6 illustrates a flowchart of an example of another method 600 for performing RRM operations in an SSB-less SCell using a UE that is (pre)configured by an access node of an SSB-less SCell with an SSB periodicity and SSB inBurst, according to some implementations. For convenience, the process 600 will be described as being performed by a UE such as a UE 102 or UE 700.

[0129] A UE can begin execution of the process 600 by receiving signaling from an access node of an SSB-less SCell, wherein the received signaling preconfigures the UE with SSB periodicity and SSB inBurst for the SSB-less SCell (610).

[0130] The UE can continue execution of the process 600 by receiving different signaling that triggers performance of the RRM operation in the SSB-less SCell (610).

[0131] In some implementations, the received signaling is SP-SSB and the received different signaling is a MAC-CE that activates or deactivates the SSB.

[0132] In some implementations, the received signaling is AP-SSB and the received different signaling is downlink control information (DCI) that aperiodically indicates to the UE to perform the RRM operation.

[0133] In some implementations, the RRM operation is T/F tracking. In some implementations, the RRM operation is AGC estimation. In such implementations, the AGC can be RSSI based AGC on the SSB-less SCell. [0134] In some implementations, the RSSI is measured based on the total power within the initial bandwidth part of SSB-less SCell, the total power within the active bandwidth part of SSB-less SCell, or the total power within a first active bandwidth part of SSB-less SCell.

[0135] FIG. 7 illustrates an example UE 700, according to some implementations. The UE 700 may be similar to and substantially interchangeable with UE 102 of FIG. 1.

[0136] The UE 700 may be any mobile or non-mobile computing device, such as, for example, mobile phones, computers, tablets, industrial wireless sensors (for example, microphones, pressure sensors, thermometers, motion sensors, accelerometers, inventory sensors, electric voltage/current meters, etc.), video devices (for example, cameras, video cameras, etc.), wearable devices (for example, a smart watch), relaxed-IoT devices.

[0137] The UE 700 may include processors 702, RF interface circuitry 704, memory/storage 706, user interface 708, sensors 710, driver circuitry 712, power management integrated circuit (PMIC) 714, one or more antenna(s) 716, and battery 718. The components of the UE 700 may be implemented as integrated circuits (ICs), portions thereof, discrete electronic devices, or other modules, logic, hardware, software, firmware, or a combination thereof. The block diagram of FIG. 7 is intended to show a high-level view of some of the components of the UE 700. However, some of the components shown may be omitted, additional components may be present, and different arrangement of the components shown may occur in other implementations.

[0138] The components of the UE 700 may be coupled with various other components over one or more interconnects 720, which may represent any type of interface, input/output, bus (local, system, or expansion), transmission line, trace, optical connection, etc. that allows various circuit components (on common or different chips or chipsets) to interact with one another.

[0139] The processors 702 may include processor circuitry such as, for example, baseband processor circuitry (BB) 722A, central processor unit circuitry (CPU) 722B, and graphics processor unit circuitry (GPU) 722C. The processors 702 may include any type of circuitry’ or processor circuitry that executes or otherwise operates computer-executable instructions, such as program code, software modules, or functional processes from memory /storage 706 to cause the UE 700 to perform operations as described herein. [0140] In some implementations, the baseband processor circuitry 722A may access a communication protocol stack 724 in the memory /storage 706 to communicate over a 3GPP compatible network. In general, the baseband processor circuitry 722A may access the communication protocol stack to: perform user plane functions at a physical (PHY) layer, medium access control (MAC) layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, service data adaptation protocol (SDAP) layer, and PDU layer; and perform control plane functions at a PHY layer, MAC layer, RLC layer, PDCP layer, RRC layer, and a non-access stratum layer. In some implementations, the PHY layer operations may additionally/altematively be performed by the components of the RF interface circuitry' 704. The baseband processor circuitry 722A may generate or process baseband signals or waveforms that carry information in 3 GPP-compatible networks. In some implementations, the waveforms for NR may be based cyclic prefix orthogonal frequency division multiplexing (OFDM) “CP-OFDM” in the uplink or downlink, and discrete Fourier transform spread OFDM “DFT-S-OFDM” in the uplink.

[0141] The memory /storage 706 may include one or more non-transitory, computer-readable media that includes instructions (for example, communication protocol stack 724) that may be executed by one or more of the processors 702 to cause the UE 700 to perform various operations described herein. The memory/storage 706 include any ty pe of volatile or nonvolatile memory that may be distributed throughout the UE 700. In some implementations, some of the memory/storage 706 may be located on the processors 702 themselves (for example. LI and L2 cache), while other memory/storage 706 is external to the processors 702 but accessible thereto via a memory interface. The memory/storage 706 may include any suitable volatile or non-volatile memory' such as, but not limited to, dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), Flash memory, solid-state memory', or any other type of memory device technology.

[0142] The RF interface circuitry 704 may include transceiver circuitry and radio frequency front module (RFEM) that allows the UE 700 to communicate with other devices over a radio access network. The RF interface circuitry 704 may include various elements arranged in transmit or receive paths. These elements may include, for example, switches, mixers, amplifiers, filters, synthesizer circuitry', control circuitry', etc. [0143] In the receive path, the RFEM may receive a radiated signal from an air interface via antenna(s) 716 and proceed to filter and amplify (with a low-noise amplifier) the signal. The signal may be provided to a receiver of the transceiver that downconverts the RF signal into a baseband signal that is provided to the baseband processor of the processors 702.

[0144] In the transmit path, the transmitter of the transceiver up-converts the baseband signal received from the baseband processor and provides the RF signal to the RFEM. The RFEM may amplify the RF signal through a power amplifier prior to the signal being radiated across the air interface via the antenna(s) 716. In various implementations, the RF interface circuitry 704 may be configured to transmit/receive signals in a manner compatible with NR access technologies.

[0145] The antenna(s) 716 may include one or more antenna elements to convert electrical signals into radio waves to travel through the air and to convert received radio waves into electrical signals. The antenna elements may be arranged into one or more antenna panels. The antenna(s) 716 may have antenna panels that are omnidirectional, directional, or a combination thereof to enable beamforming and multiple input, multiple output communications. The antenna(s) 716 may include microstrip antennas, printed antennas fabricated on the surface of one or more printed circuit boards, patch antennas, phased array antennas, etc. The antenna(s) 716 may have one or more panels designed for specific frequency bands including bands in FR1 or FR2.

[0146] The user interface 708 includes various input/output (I/O) devices designed to enable user interaction with the UE 700. The user interface 708 includes input device circuitry and output device circuitry. Input device circuitry includes any physical or virtual means for accepting an input including, inter alia, one or more physical or virtual buttons (for example, a reset button), a physical keyboard, keypad, mouse, touchpad, touchscreen, microphones, scanner, headset, or the like. The output device circuitry includes any physical or virtual means for showing information or otherwise conveying information, such as sensor readings, actuator position(s), or other like information. Output device circuitry may include any number or combinations of audio or visual display, including, inter alia, one or more simple visual outputs/indicators (for example, binary' status indicators such as light emitting diodes “LEDs” and multi -character visual outputs), or more complex outputs such as display devices or touchscreens (for example, liquid crystal displays “LCDs,” LED displays, quantum dot displays, projectors, etc.), with the output of characters, graphics, multimedia objects, and the like being generated or produced from the operation of the UE 700.

[0147] The sensors 710 may include devices, modules, or subsystems whose purpose is to detect events or changes in its environment and send the information (sensor data) about the detected events to some other device, module, subsystem, etc. Examples of such sensors include, inter alia, inertia measurement units including accelerometers, gyroscopes, or magnetometers; microelectromechanical systems or nanoelectromechanical systems including 3-axis accelerometers, 3-axis gyroscopes, or magnetometers; level sensors; temperature sensors (for example, thermistors); pressure sensors; image capture devices (for example, cameras or lensless apertures); light detection and ranging sensors; proximity sensors (for example, infrared radiation detector and the like); depth sensors; ambient light sensors; ultrasonic transceivers; microphones or other like audio capture devices; etc.

[0148] The driver circuitry 712 may include software and hardware elements that operate to control particular devices that are embedded in the UE 700, attached to the UE 700, or otherwise communicatively coupled with the UE 700. The driver circuitry 712 may include individual drivers allowing other components to interact with or control various input/output (I/O) devices that may be present within, or connected to. the UE 700. For example, driver circuitry 712 may include a display driver to control and allow access to a display device, a touchscreen driver to control and allow access to a touchscreen interface, sensor drivers to obtain sensor readings of sensors 710 and control and allow access to sensors 710, drivers to obtain actuator positions of electro-mechanic components or control and allow access to the electro-mechanic components, a camera driver to control and allow access to an embedded image capture device, audio drivers to control and allow access to one or more audio devices.

[0149] The PMIC 714 may manage power provided to various components of the UE 700. In particular, with respect to the processors 702, the PMIC 714 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion.

[0150] In some implementations, the PMIC 714 may control, or otherwise be part of, various power saving mechanisms of the UE 700. A battery 718 may power the UE 700, although in some examples the UE 700 may be mounted deployed in a fixed location, and may have a power supply coupled to an electrical grid. The battery' 718 may be a lithium ion battery', a metal-air battery, such as a zinc-air battery’, an aluminum-air battery, a lithium-air battery’, and the like. In some implementations, such as in vehicle-based applications, the battery 718 may be a typical lead-acid automotive batten’.

[0151] FIG. 8 illustrates an example access node 800 (e.g.. a base station or gNB), according to some implementations. The access node 800 may be similar to and substantially interchangeable with base station 104. The access node 800 may include processors 802, RF interface circuitry' 804, core network (CN) interface circuitry' 806, memory /storage circuitry 808, and one or more antenna(s) 810.

[0152] The components of the access node 800 may be coupled with various other components over one or more interconnects 812. The processors 802, RF interface circuitry 804, memory/storage circuitry 808 (including communication protocol stack 814), antenna(s) 810, and interconnects 812 may be similar to like-named elements shown and described with respect to FIG. 7. For example, the processors 802 may include processor circuitry such as, for example, baseband processor circuitry (BB) 816A, central processor unit circuitry (CPU) 816B, and graphics processor unit circuitry (GPU) 816C.

[0153] The CN interface circuitry 806 may provide connectivity to a core network, for example, a 5th Generation Core network (5GC) using a 5GC-compatible network interface protocol such as carrier Ethernet protocols, or some other suitable protocol. Network connectivity may be provided to/from the access node 800 via a fiber optic or wireless backhaul. The CN interface circuitry 806 may include one or more dedicated processors or FPGAs to communicate using one or more of the aforementioned protocols. In some implementations, the CN interface circuitry 806 may include multiple controllers to provide connectivity to other networks using the same or different protocols.

[0154] As used herein, the terms “access node." “access point,” or the like may describe equipment that provides the radio baseband functions for data and/or voice connectivity between a network and one or more users. These access nodes can be referred to as BS, gNBs, RAN nodes, eNBs, NodeBs, RSUs, TRxPs or TRPs, and so forth, and can include ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). As used herein, the term “NG RAN node” or the like may refer to an access node 800 that operates in an NR or 5G system (for example, a gNB), and the term “E-UTRAN node” or the like may refer to an access node 800 that operates in an LTE or 4G system (e.g., an eNB). According to various implementations, the access node 800 may be implemented as one or more of a dedicated physical device such as a macrocell base station, and/or a low power (LP) base station for providing femtocells, picocells or other like cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells.

[0155] In some implementations, all or parts of the access node 800 may be implemented as one or more software entities running on server computers as part of a virtual network, which may be referred to as a CRAN and/or a virtual baseband unit pool (vBBUP). In V2X scenarios, the access node 800 may be or act as a "‘Road Side Unit.” The term ‘"Road Side Unit” or “RSU” may refer to any transportation infrastructure entity used for V2X communications. An RSU may be implemented in or by a suitable RAN node or a stationary (or relatively stationary) UE, where an RSU implemented in or by a UE may be referred to as a "UE-type RSU,” an RSU implemented in or by an eNB may be referred to as an “eNB-type RSU,” an RSU implemented in or by a gNB may be referred to as a "gNB-type RSU,” and the like.

[0156] Various components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase "configured to.” Reciting a component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f) interpretation for that component.

[0157] For one or more embodiments, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, or methods as set forth in the example section below. For example, the baseband circuitry⁷ as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth below in the example section.

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

Claims

1. A method for performing a radio resource management (RRM) operation using a system synchronization block-less secondary cell (SSB-less SCell), the method comprising: determining, by a user equipment (UE), that a target SCell is an SSB-less SCell; determining, by the UE and based on the target SCell being an SSB-less SCell, a reference serving cell for the target SCell; and performing, by the UE, a RRM operation in the target SCell based on a reference signal of the reference serving cell.

2. The method of claim 1, wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting, by the UE, a reference serving cell on the closest band or carrier relative to the band or carrier of the SSB-less SCell.

3. The method of claim 2, wherein the closest band relative to the band or carrier of the SSB-less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

4. The method of claim 1, the method further comprising: receiving, by the UE, signaling from an access node, that configures a reference serv ing cell index to SSB-less SCell when adding an SSB-less SCell to the UE; and wherein determining a reference serv ing cell for the target SSB-less SCell comprises: selecting, by the UE, a reference serv ing cell based on the reference service cell index.

5. The method of claim 1, the method further comprising: determining, by the UE, a type of the reference signal used by the reference serving cell.

6. The method of claim 5, the method further comprising: based on a determination, by the UE, that the reference signal used by the reference serving cell is an SSB reference signal, selecting, by the UE, the SSB reference signal as a reference signal for use in the performance of the RRM operation in the SSB-less SCell.

7. The method of claim 1, the method further comprising: receiving, by the UE, signaling from an access node, that configures one or multiple SSB index of a reference serving cell for the SSB-less SCell when adding the SSB-less SCell to the UE; and wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting, by the UE, the one or more multiple SSB of the reference serving cell indicated by the SSB index as a reference signal, for use in the performance of the RRM operation in the SSB-less SCell.

8. The method of claim 5, the method further comprising: based on a determination, by the UE, that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CSI-RS), selecting, by the UE, the TRS or CSI-RS as the reference signal for use in the performance of the RRM operation in the SSB-less SCell.

9. The method of claim 8, wherein the selected TRS is active TRS and the selected CSI- RS is semi-persistent (SP) or periodic CSI-RS.

10. The method of claim 8, wherein selection of the TRS as the reference signal is prioritized over selection of the CSI-RS as the reference signal.

11. The method of claim 8, wherein the CSI-RS is Quasi Collocated (QCLed) w ith another reference signal from the reference serving cell.

12. The method of claim 1, the method further comprising: receiving, by the UE, signaling from an access node, that configures one or multiple CSI-RS index of a reference serv ice cell for the SSB-less SCell when adding an SSB-less SCell to the UE; and wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting, by the UE, the CSI-RS as a reference signal, based on the CSI-RS index, for use in the performance of the RRM operation in the SSB-less SCell.

13. The method of claim 1, wherein the RRM operation comprises (i) L3 measurement for the target SSB-less SCell, (ii) activation of the target SSB-less SCell, (iii) time and frequency tracking (T/F tracking), or (iv) (AGC) estimation.

14. One or more processors comprising circuitry to execute one or more instructions that, when executed, cause user equipment (UE) to perform operations comprising: determining that a target SCell is an SSB-less SCell; determining, based on the target SCell being an SSB-less SCell, a reference serving cell for the target SCell; and performing a RRM operation in the target SCell based on a reference signal of the reference serving cell.

15. The one or more processors of claim 14, wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting a reference serving cell on the closest band or carrier relative to the band or carrier of the SSB-less SCell.

16. The one or more processors of claim 15, wherein the closest band relative to the band or carrier of the SSB-less SCell is a reference serving cell on an adjacent band or carrier to the SSB-less SCell.

17. The one or more processors of claim 14, the operations further comprising: receiving signaling from an access node, that configures a reference serving cell index to SSB-less SCell when adding an SSB-less SCell to the UE; and wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting a reference serving cell based on the reference service cell index.

18. The one or more processors of claim 14. the operations further comprising: determining a type of the reference signal used by the reference serving cell.

19. The one or more processors of claim 18, the operations further comprising: based on a determination that the reference signal used by the reference serving cell is an SSB reference signal, selecting the SSB reference signal as a reference signal for use in the performance of the RRM operation in the SSB-less SCell.

20. The one or more processors of claim 14, the operations further comprising: receiving signaling from an access node, that configures one or multiple SSB index of a reference serving cell for the SSB-less SCell when adding the SSB-less SCell to the UE; and wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting the one or more multiple SSB of the reference serving cell indicated by the SSB index as a reference signal, for use in the performance of the RRM operation in the SSB-less SCell.

21. The one or more processors of claim 18, the operations further comprising: based on a determination that the reference signal used by the reference serving cell is a tracking reference signal (TRS) or channel state information reference signal (CSI-RS), selecting, by the UE, the TRS or CSI-RS as the reference signal for use in the performance of the RRM operation in the SSB-less SCell.

22. The one or more processors of claim 21. wherein the selected TRS is active TRS and the selected CSI-RS is semi -persistent (SP) or periodic CSI-RS.

23. The one or more processors of claim 21, wherein selection of the TRS as the reference signal is prioritized over selection of the CSI-RS as the reference signal.

24. The one or more processors of claim 21, wherein the CSI-RS is Quasi Collocated (QCLed) with another reference signal from the reference serving cell.

25. The one or more processors of claim 14, the operations further comprising: receiving signaling from an access node, that configures one or multiple CSI-RS index of a reference sendee cell for the SSB-less SCell when adding an SSB-less SCell to the UE; and wherein determining a reference serving cell for the target SSB-less SCell comprises: selecting the CSI-RS as a reference signal, based on the CSI-RS index, for use in the performance of the RRM operation in the SSB-less SCell.

26. The one or more processors of claim 25, wherein the selected CSI-RS is semi- persistent (SP) or periodic CSI-RS.

27. The one or more processors of claim 14. wherein the RRM operation comprises (i) L3 measurement for the target SSB-less SCell, (ii) activation of the target SSB-less SCell, (iii) time and frequency tracking (T/F tracking), or (iv) (AGC) estimation.