Patent Publication Number: US-2022232474-A1

Title: Ue idle and inactive mode enhancement with sidelink

Description:
FIELD OF TECHNOLOGY 
     The following relates to wireless communication, including UE idle and inactive mode enhancement with sidelink. 
     BACKGROUND 
     Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). 
     A UE may operate in a low power mode, such as an idle or inactive mode. An inactive or idle mode UE may be configured to periodically wake up to receive a reference signal (e.g., a synchronization signal block (SSB)) to be used for tracking, synchronization, channel estimation, or other operations. However, the reference signal may be transmitted with a low periodicity and/or in a limited bandwidth. The UE may therefore wake up repeatedly to receive a number of reference signals during reference signal occasions, which may increase power consumption and reduce efficiency at the UE. 
     SUMMARY 
     The described techniques relate to improved methods, systems, devices, and apparatuses that support UE idle and inactive mode enhancement with sidelink. Generally, the described techniques enable a UE operating in an idle mode or an inactive mode to be provided with additional reference signal configurations using sidelink communications. A connected mode UE may determine to share a reference signal configuration with the idle/inactive mode UE via a sidelink transmission. In some examples, the idle/inactive mode UE may transmit a request for a reference signal configuration. The reference signal configuration may include reference signal resources that correspond to one or more beams that are tracked by the connected mode UE, such as an active downlink beam or beams adjacent to an active downlink beam. The idle/inactive mode UE may use the reference signal configuration to monitor for and receive one or more reference signals from the base station. In some examples, the connected mode UE may determine to transmit the sidelink transmission based on satisfaction of a trigger condition, such as a proximity of the idle/inactive mode UE to the connected mode UE. Additionally, or alternatively, the idle/inactive mode UE may prioritize received reference signal configurations or resources based on the proximity. 
     A method for wireless communication at a first UE is described. The method may include receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station, monitoring for the one or more reference signals based on the reference signal configuration received from the second UE, and receiving at least one reference signal from the base station based on the monitoring. 
     An apparatus for wireless communication at a first UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station, monitor for the one or more reference signals based on the reference signal configuration received from the second UE, and receive at least one reference signal from the base station based on the monitoring. 
     Another apparatus for wireless communication at a first UE is described. The apparatus may include means for receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station, means for monitoring for the one or more reference signals based on the reference signal configuration received from the second UE, and means for receiving at least one reference signal from the base station based on the monitoring. 
     A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor to receive, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station, monitor for the one or more reference signals based on the reference signal configuration received from the second UE, and receive at least one reference signal from the base station based on the monitoring. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving reference signal resources that correspond with an active downlink beam tracked by the second UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving reference signal resources that correspond with an active downlink beam tracked by the second UE and with one or more beams adjacent to the active downlink beam. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving all reference signal resources configured to the second UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving a set of multiple reference signal resources configured to the second UE in an ordered list in accordance with an order, where individual reference signal resources of the set of multiple reference signal resources each correspond to a beam tracked by the second UE, and where the order may be based on proximity of respective beams to an active downlink beam tracked by the second UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving, as part of the sidelink transmission, an indication of a transmit power used by the second UE for transmitting the sidelink transmission, physical positioning information of the second UE, zone information of the second UE, or some combination thereof. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a proximity of the first UE to the second UE based on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof and using the reference signal configuration for monitoring for the one or more reference signals based on the proximity of the first UE to the second UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving a set of multiple sidelink transmissions from the set of multiple UEs, each of the set of multiple sidelink transmissions including respective reference signal configurations for receiving the one or more reference signals from the base station. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for selecting the reference signal configuration from the set of multiple sidelink transmissions based on a proximity of the first UE with each of the set of multiple UEs. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a reference signal configuration request message, where the sidelink transmission may be received based on the reference signal configuration request message. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration request message may include operations, features, means, or instructions for transmitting, as part of the reference signal configuration request message, an indication of a transmit power of the reference signal configuration request message, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration request message may include operations, features, means, or instructions for transmitting the reference signal configuration request message as one of a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the at least one reference signal includes a channel state information reference signal (CSI-RS) and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for using the channel state information (CSI)-RS for one or more of downlink channel estimation, timing and frequency tracking updating, automatic gain control (AGC) loop updating, or serving cell radio resource management (RRM) measurement. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the at least one reference signal includes a positioning reference signal (PRS) and the method, apparatuses, and non-transitory computer-readable medium may include further operations, features, means, or instructions for using the PRS for downlink-based positioning. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the sidelink transmission that includes the reference signal configuration may include operations, features, means, or instructions for receiving the sidelink transmission over the sidelink channel via one of a unicast transmission, a groupcast transmission, or a broadcast transmission. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first UE may be in a radio resource control (RRC) idle mode or an inactive mode. 
     A method for wireless communication at a first UE is described. The method may include identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station, determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition, and transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     An apparatus for wireless communication at a first UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to identify a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station, determine to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition, and transmit the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     Another apparatus for wireless communication at a first UE is described. The apparatus may include means for identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station, means for determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition, and means for transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor to identify a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station, determine to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition, and transmit the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration may include operations, features, means, or instructions for transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration may include operations, features, means, or instructions for transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE and with one or more beams adjacent to the active downlink beam. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration may include operations, features, means, or instructions for transmitting all reference signal resources configured to the first UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the reference signal configuration may include operations, features, means, or instructions for transmitting a set of multiple reference signal resources configured to the first UE in an ordered list in accordance with an order, where individual reference signal resources of the set of multiple reference signal resources each correspond to a beam tracked by the first UE, and where the order may be based on proximity of respective beams to an active downlink beam tracked by the first UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the sidelink transmission includes an indication of a transmit power of the sidelink transmission, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the second UE, a reference signal configuration request message, where the sidelink transmission may be transmitted based on the reference signal configuration request message. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, as part of the reference signal configuration request message, an indication of a transmit power used by the second UE to transmit the reference signal configuration request message, physical positioning information of the second UE, zone information of the second UE, or some combination thereof, determining a proximity of the first UE to the second UE based on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof, and determining whether the trigger condition may be satisfied based on the proximity. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for selecting between a narrow beam reference signal configuration and a wide beam reference signal configuration based on the proximity. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the one or more reference signals include a CSI-RS or a PRS. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the sidelink transmission may be transmitted as a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first UE may be in a connected mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a wireless communications system that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIG. 2  illustrates an example of a wireless communications system that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIG. 3  illustrates an example of a transmission diagram that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIG. 4  illustrates an example of a process flow that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIGS. 5 and 6  show block diagrams of devices that support UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIG. 7  shows a block diagram of a communications manager that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIG. 8  shows a diagram of a system including a device that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
         FIGS. 9 through 12  show flowcharts illustrating methods that support UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Some wireless communications systems may support an inactive mode and/or an idle mode for user equipment (UE). A UE may operate in an idle or inactive mode, for example, to conserve battery and reduce power consumption. While in idle or inactive mode, the UE may spend less time monitoring for signaling from a base station and may spend a majority of time in sleep, but may periodically wake up to monitor for a paging message. Additionally, the UE may periodically wake up to monitor for and receive a reference signal, such as a synchronization signal block (SSB), and may use the SSB to measure one or more channel parameters for receiving the paging message. For instance, the UE may perform tracking, synchronization, or other operations. However, SSBs may be transmitted with a relatively low periodicity, a low transmit power, or a narrow bandwidth. Accordingly, the idle/inactive mode UE may not be able to perform such reference signal operations without receiving several SSBs, and other factors (e.g., poor channel conditions) may further increase the number of SSBs received by the UE before the UE is able to receive the paging message. The UE may therefore suffer increased power consumption as the number of SSBs increases, as the UE must be awake for each SSB occasion. Further, the UE may experience decreased efficiency and may be unable to receive paging messages quickly, as increasing the number of SSBs increases the duration spent to obtain sufficient information. 
     In some examples, the idle/inactive mode UE may obtain other reference signals (e.g., different from an SSB) to use in determining channel parameters, but the other reference signals may not be configured for the idle/inactive mode UE. For instance, the reference signal may be configured for a connected mode UE and may correspond to a relatively narrow beam. The idle/inactive mode UE may therefore consume additional power tracking the narrow beam. Additionally, the narrow beam may not be accessible to the idle/inactive mode UE, e.g., if the idle/inactive mode UE is geographically far from the connected mode UE. 
     Providing idle/inactive mode UEs with additional reference signal configurations may reduce power consumption and inefficiency associated with performing tracking and synchronization while in idle/inactive modes. While a UE operating in an idle/inactive mode may not have an active connection with a base station, the UE may still maintain one or more sidelink connections with other UEs. Thus, a UE with an active connection to a base station (e.g., a UE operating in a connected mode) may share an active reference signal configuration with a nearby idle/inactive mode UE via a sidelink transmission. In some cases, the idle/inactive mode UE may transmit a message requesting that the connected mode UE share a reference signal configuration. The idle/inactive mode UE may use the reference signal configuration to monitor for and receive one or more reference signals (e.g., channel state information reference signals (CSI-RSs), positioning reference signals (PRSs), tracking reference signals (TRSs), etc.) from a base station. The reference signal configuration may include resources for one or more beams tracked by the connected mode UE. For instance, the reference signal configuration may include reference signal resources that correspond with an active downlink beam, as well as reference signal resources that correspond with one or more beams adjacent to the active downlink beam. The idle/inactive mode UE may therefore reduce an overall wake-up time by receiving reference signals more frequently (as compared to only receiving SSBs), which may in turn reduce power consumption at the idle/inactive mode UE. Additionally, receiving reference signals more frequently may reduce the duration needed by the idle/inactive mode UE to obtain the channel parameters for receiving a paging message. 
     In some examples, the connected mode UE may transmit the reference signal configuration to multiple other idle/inactive mode UEs. Similarly, the idle/inactive mode UE may receive reference signal configurations from multiple other connected mode UEs. The idle/inactive mode UE and the connected mode UE may therefore also share location information and/or transmit power information (e.g., for the sidelink transmission transmitted by the connected mode UE and/or the request message transmitted by the idle/inactive mode UE) such that each UE may determine their proximity to one another. The connected mode UE may use the proximity to determine whether to transmit a reference signal configuration to the idle/inactive mode UE. For example, the connected mode UE may refrain from sharing a reference signal configuration for a narrow beam reference signal if the idle/inactive mode UE is too far away (e.g., if the narrow beam would be inaccessible to the idle/inactive mode UE). The idle/inactive mode UE may prioritize reference signal configurations received from connected mode UEs that are closer in proximity. 
     Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are then described with reference to a transmission diagram and a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to UE idle and inactive mode enhancement with sidelink. 
       FIG. 1  illustrates an example of a wireless communications system  100  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The wireless communications system  100  may include one or more base stations  105 , one or more UEs  115 , and a core network  130 . In some examples, the wireless communications system  100  may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system  100  may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof. 
     The base stations  105  may be dispersed throughout a geographic area to form the wireless communications system  100  and may be devices in different forms or having different capabilities. The base stations  105  and the UEs  115  may wirelessly communicate via one or more communication links  125 . Each base station  105  may provide a coverage area  110  over which the UEs  115  and the base station  105  may establish one or more communication links  125 . The coverage area  110  may be an example of a geographic area over which a base station  105  and a UE  115  may support the communication of signals according to one or more radio access technologies. 
     The UEs  115  may be dispersed throughout a coverage area  110  of the wireless communications system  100 , and each UE  115  may be stationary, or mobile, or both at different times. The UEs  115  may be devices in different forms or having different capabilities. Some example UEs  115  are illustrated in  FIG. 1 . The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115 , the base stations  105 , or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in  FIG. 1 . 
     The base stations  105  may communicate with the core network  130 , or with one another, or both. For example, the base stations  105  may interface with the core network  130  through one or more backhaul links  120  (e.g., via an S1, N2, N3, or other interface). The base stations  105  may communicate with one another over the backhaul links  120  (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations  105 ), or indirectly (e.g., via core network  130 ), or both. In some examples, the backhaul links  120  may be or include one or more wireless links. 
     One or more of the base stations  105  described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology. 
     A UE  115  may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE  115  may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE  115  may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples. 
     The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115  that may sometimes act as relays as well as the base stations  105  and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in  FIG. 1 . 
     The UEs  115  and the base stations  105  may wirelessly communicate with one another via one or more communication links  125  over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links  125 . For example, a carrier used for a communication link  125  may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP)) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system  100  may support communication with a UE  115  using carrier aggregation or multi-carrier operation. A UE  115  may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. 
     In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by the UEs  115 . A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs  115  via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology). 
     The communication links  125  shown in the wireless communications system  100  may include uplink transmissions from a UE  115  to a base station  105 , or downlink transmissions from a base station  105  to a UE  115 . Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode). 
     A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system  100 . For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)). 
     Devices of the wireless communications system  100  (e.g., the base stations  105 , the UEs  115 , or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system  100  may include base stations  105  or UEs  115  that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE  115  may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth. 
     Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements that a UE  115  receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE  115 . A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE  115 . 
     The time intervals for the base stations  105  or the UEs  115  may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T s =1/(Δf max ·N f ) seconds, where Δf max  may represent the maximum supported subcarrier spacing, and N f  may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023). 
     Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems  100 , a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N f ) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation. 
     A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system  100  and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system  100  may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)). 
     Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs  115 . For example, one or more of the UEs  115  may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs  115  and UE-specific search space sets for sending control information to a specific UE  115 . 
     Each base station  105  may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used for communication with a base station  105  (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or others). In some examples, a cell may also refer to a geographic coverage area  110  or a portion of a geographic coverage area  110  (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station  105 . For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas  110 , among other examples. 
     A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs  115  with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station  105 , as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs  115  with service subscriptions with the network provider or may provide restricted access to the UEs  115  having an association with the small cell (e.g., the UEs  115  in a closed subscriber group (CSG), the UEs  115  associated with users in a home or office). A base station  105  may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers. 
     In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that may provide access for different types of devices. 
     In some examples, a base station  105  may be movable and therefore provide communication coverage for a moving geographic coverage area  110 . In some examples, different geographic coverage areas  110  associated with different technologies may overlap, but the different geographic coverage areas  110  may be supported by the same base station  105 . In other examples, the overlapping geographic coverage areas  110  associated with different technologies may be supported by different base stations  105 . The wireless communications system  100  may include, for example, a heterogeneous network in which different types of the base stations  105  provide coverage for various geographic coverage areas  110  using the same or different radio access technologies. 
     The wireless communications system  100  may support synchronous or asynchronous operation. For synchronous operation, the base stations  105  may have similar frame timings, and transmissions from different base stations  105  may be approximately aligned in time. For asynchronous operation, the base stations  105  may have different frame timings, and transmissions from different base stations  105  may, in some examples, not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations. 
     Some UEs  115 , such as MTC or IoT devices, may be low cost or low complexity devices and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication). M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station  105  without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans interacting with the application program. Some UEs  115  may be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging. 
     Some UEs  115  may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously). In some examples, half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for the UEs  115  include entering a power saving deep sleep mode when not engaging in active communications, operating over a limited bandwidth (e.g., according to narrowband communications), or a combination of these techniques. For example, some UEs  115  may be configured for operation using a narrowband protocol type that is associated with a defined portion or range (e.g., set of subcarriers or resource blocks (RBs)) within a carrier, within a guard-band of a carrier, or outside of a carrier. 
     The wireless communications system  100  may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system  100  may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs  115  may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions). Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT), mission critical video (MCVideo), or mission critical data (MCData). Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein. 
     In some examples, a UE  115  may also be able to communicate directly with other UEs  115  over a device-to-device (D2D) communication link  135  (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs  115  utilizing D2D communications may be within the geographic coverage area  110  of a base station  105 . Other UEs  115  in such a group may be outside the geographic coverage area  110  of a base station  105  or be otherwise unable to receive transmissions from a base station  105 . In some examples, groups of the UEs  115  communicating via D2D communications may utilize a one-to-many (1:M) system in which each UE  115  transmits to every other UE  115  in the group. In some examples, a base station  105  facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs  115  without the involvement of a base station  105 . 
     In some systems, the D2D communication link  135  may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs  115 ). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations  105 ) using vehicle-to-network (V2N) communications, or with both. 
     The core network  130  may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network  130  may be an evolved packet core (EPC) or 5G core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs  115  served by the base stations  105  associated with the core network  130 . User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to IP services  150  for one or more network operators. The IP services  150  may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service. 
     Some of the network devices, such as a base station  105 , may include subcomponents such as an access network entity  140 , which may be an example of an access node controller (ANC). Each access network entity  140  may communicate with the UEs  115  through one or more other access network transmission entities  145 , which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). Each access network transmission entity  145  may include one or more antenna panels. In some configurations, various functions of each access network entity  140  or base station  105  may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station  105 ). 
     The wireless communications system  100  may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs  115  located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz. 
     The wireless communications system  100  may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz), also known as the millimeter band. In some examples, the wireless communications system  100  may support millimeter wave (mmW) communications between the UEs  115  and the base stations  105 , and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body. 
     The wireless communications system  100  may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system  100  may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations  105  and the UEs  115  may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples. 
     A base station  105  or a UE  115  may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station  105  or a UE  115  may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station  105  may be located in diverse geographic locations. A base station  105  may have an antenna array with a number of rows and columns of antenna ports that the base station  105  may use to support beamforming of communications with a UE  115 . Likewise, a UE  115  may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port. 
     The base stations  105  or the UEs  115  may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices. 
     Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station  105 , a UE  115 ) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation). 
     A base station  105  or a UE  115  may use beam sweeping techniques as part of beam forming operations. For example, a base station  105  may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE  115 . Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station  105  multiple times in different directions. For example, the base station  105  may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station  105 , or by a receiving device, such as a UE  115 ) a beam direction for later transmission or reception by the base station  105 . 
     Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station  105  in a single beam direction (e.g., a direction associated with the receiving device, such as a UE  115 ). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE  115  may receive one or more of the signals transmitted by the base station  105  in different directions and may report to the base station  105  an indication of the signal that the UE  115  received with a highest signal quality or an otherwise acceptable signal quality. 
     In some examples, transmissions by a device (e.g., by a base station  105  or a UE  115 ) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station  105  to a UE  115 ). The UE  115  may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station  105  may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)), which may be precoded or unprecoded. The UE  115  may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by a base station  105 , a UE  115  may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE  115 ) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device). 
     A receiving device (e.g., a UE  115 ) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station  105 , such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening according to multiple beam directions). 
     The wireless communications system  100  may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE  115  and a base station  105  or a core network  130  supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels. 
     The UEs  115  and the base stations  105  may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood that data is received correctly over a communication link  125 . HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions). In some examples, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval. 
     The wireless communications system  100  may support a UE  115  operating in an idle or inactive mode. For example, when a UE  115  does not have much traffic from serving cells, the UE  115  may enter an inactive or idle mode to conserve battery and improve power savings. When the UE  115  is in the inactive mode, the last-serving base station  105  may maintain access-stratum context for the UE  115 , which may have been established by an RRC connection. When the UE  115  is in the idle mode, the network may discard the UE context. 
     When the UE  115  is operating in the inactive mode or the idle mode, the UE  115  may spend less time monitoring for signaling, thereby reducing power consumption. While operating in the inactive mode or idle mode, the UE  115  may sleep for most of a discontinuous reception (DRX) cycle and periodically wake up to monitor for a paging message. In some cases, the UE  115  may monitor for one paging occasion per DRX cycle. Each paging occasion may include a set of physical downlink control channel (PDCCH) monitoring occasions and may include multiple time slots (e.g., multiple subframes or multiple OFDM symbols) where paging downlink control information (DCI) may be sent. The UE  115  may attempt to decode signals using a paging radio network temporary identifier (P-RNTI) to check for messages indicating pending data. If the UE  115  does not detect a paging message indicating presence of data or a call, the UE  115  may go back to sleep until the next paging occasion. 
     The techniques described herein support providing a UE  115  in an inactive mode or an idle mode with additional reference signals such as TRSs, PRSs, and CSI-RSs. A UE  115  in idle/inactive mode may receive, from a UE  115  in connected mode, a sidelink transmission including a reference signal configuration. The sidelink transmission may be transmitted by the connected mode UE  115  and received by the idle/inactive mode UE  115  over a sidelink channel as a unicast transmission, a groupcast transmission, or a broadcast transmission. The reference signal configuration may include resources for one or more beams tracked by the connected mode UE  115 . The idle/inactive mode UE  115  may monitor for and receive one or more reference signals from a base station  105  based on the reference signal configuration. In some examples, the idle/inactive mode UE  115  may use the received reference signal(s) to perform one or more operations. For instance, if the received reference signal is a CSI-RS, the idle/inactive mode UE  115  may perform downlink channel estimation, timing and frequency tracking loop updating, automatic gain control (AGC) loop updating, serving cell radio resource management (RRM) measurement, or some combination thereof. If the received reference signal is a PRS, the idle/inactive mode UE  115  may use the PRS for downlink-based positioning. 
     In some examples, the idle/inactive mode UE  115  may receive sidelink transmissions including reference signal configurations from multiple connected mode UEs  115 . Thus, in such examples, each connected mode UE  115  may include, as part of the sidelink transmission, information that may enable the idle/inactive mode UE  115  to derive a proximity to the corresponding connected mode UE  115 . The idle/inactive mode UE  115  may prioritize reference signal configurations received from connected mode UEs  115  that are closer in proximity to the idle/inactive mode UE  115 . 
     In some cases, the idle/inactive mode UE  115  may transmit a request for a reference signal configuration, for example, as a unicast transmission, a broadcast transmission, or a groupcast transmission. The idle/inactive mode UE  115  may include, as part of the request, information that may enable a receiving connected mode UE  115  to derive a proximity to the idle/inactive mode UE  115 . Based on the proximity, the connected mode UE  115  may selectively transmit, to the idle/inactive mode UE  115  in response to the request message, a sidelink transmission including a reference signal configuration. For example, if the connected mode UE  115  is too far away from the idle/inactive mode UE  115 , the connected mode UE  115  may determine to refrain from transmitting a reference signal configuration or may determine to transmit a wide beam reference signal configuration (e.g., instead of a narrow beam reference signal configuration, which may not be accessible or useful to the idle/inactive mode UE  115 ). 
       FIG. 2  illustrates an example of a wireless communications system  200  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. In some examples, the wireless communications system  200  may implement aspects of wireless communication system  100 . The wireless communications system  200  may include UEs  215 - a ,  215 - b , and  215 - c , and a base station  205 , which may be respective examples of a UE  115  and a base station  105  described with reference to  FIG. 1 . UEs  215 - a  and  215 - b  may communicate with  215 - c  via sidelinks  210 - a  and  210 - b , respectively. 
     UEs  215  operating in wireless communications system  200  may operate in one of a connected mode, an idle mode, or an inactive mode. For instance, if a UE  215 , such as UE  215 - c , has limited traffic from serving cells, UE  215 - c  may enter a low power mode to conserve battery and improve power savings. For example, UE  215 - c  may enter an inactive mode or an idle mode. When UE  215 - c  is in the inactive mode, base station  205  may maintain the UE context established by an RRC connection. When UE  215 - c  is in the idle mode, base station  205  may discard the UE context. In some examples, UE  215 - c  may be in an idle/inactive mode based on a UE type. For instance, UE  215 - c  may be a sensing device or a reduced capability (REDCAP) UE and may not be configured to transmit or receive, and may therefore operate in idle/inactive mode for extensive periods of time. Alternatively, UEs  215 - a  and  215 - b  may operate in a connected mode, where UE  215 - a  and UE  215 - b  each have an active RRC connection with base station  205 . 
     When UEs  215 - a  and  215 - b  are operating in an active or connected mode, base station  205  may manage some radio resource management operations for UEs  215 - a  and  215 - b  based on UE mobility, radio channel quality, or both. In some cases, base station  205  may configure UEs  215 - a  and  215 - b  with one or more reference signal configurations so that UEs  215 - a  and  215 - b  may receive reference signals (e.g., reference signals  220 - a  and  220 - b , respectively) from base station  205 . For example, a reference signal configuration may include time resources, frequency resources, spatial resources, or some combination thereof, that may be used by UEs  215 - a  and  215 - b  to receive a reference signal  220 . Reference signals  220  may be a TRS, a CSI-RS, or a PRS, among other examples. For instance, base station  205  may transmit a TRS to UEs  215 - a  and  215 - b , which may be used to track the downlink trimming and frequency of UEs  215 - a  and  215 - b  within the wireless communications system  200 . To measure channel conditions for UEs  215 - a  and  215 - b , base station  205  may transmit a CSI-RS. UEs  215 - a  and  215 - b  may measure the CSI-RS and provide a CSI report to the base station  205  indicating various radio channel quality measurements. Additionally or alternatively, base station  205  may transmit a PRS to UEs  215 - a  and  215 - b  to determine positioning of the UEs  215 - a  and  215 - b.    
     When UE  215 - c  is operating in the inactive mode or the idle mode, UE  215 - c  may spend less time monitoring for signaling from base station  205 , thereby reducing power consumption. While operating in the inactive mode or idle mode, UE  215 - c  may sleep for most of a DRX cycle and periodically wake up to monitor for a paging message or an SSB  225 . For example, UE  215 - c  may wake up for an SSB occasion to receive an SSB  225 , which UE  215 - c  may use to perform tracking and/or synchronization (e.g., to find a downlink channel). However, SSB occasions may have a relatively low periodicity (e.g., 20 milliseconds (ms)) and may be transmitted on a relatively narrow bandwidth and with a low transmit power. Thus, UE  215 - c  may not be able to perform tracking and synchronization by receiving one SSB occasion. That is, the UE  215 - c  may need to receive multiple SSB occasions to obtain enough signal energy to perform tracking and synchronization. Due to the low periodicity of the SSB occasions, UE  215 - c  may therefore not be able to perform tracking and synchronization in a short time frame. For instance, in the example of  FIG. 2 , UE  215 - c  may be far from base station  205  and SSB  225  may be transmitted with a relatively low transmit power. UE  215 - c  may therefore wake up for multiple SSB occasions. If, for example, each SSB occasion is transmitted with a periodicity of 20 ms and UE  215 - c  wakes up for three SSB occasions, the UE  215 - c  may not perform tracking and synchronization until 60 ms have passed. Additionally, poor channel conditions (e.g., a low signal-to-interference-plus-noise ratio (SINR), a low signal-to-noise ratio (SNR), etc.) may further increase the number of SSB occasions needed by UE  215 - c  and, consequentially, the number of wake-up instances. As each wake-up instance consumes power, increasing the number of wake-up instances also increases the power consumption of the UE  215 - c.    
     To reduce the number of wake-up instances, and therefore the power consumption of the UE  215 - c , base station  205  may share a reference signal configuration for a connected mode UE  215  (e.g., UE  215 - a , UE  215 - b ) with an idle/inactive mode UE  215  (e.g., UE  215 - c ), so that the idle/inactive mode UE  215  may receive one or more additional reference signals (e.g., other than an SSB). However, because the reference signal configuration shared by base station  205  is not dedicated for the UE  215 - c , UE  215 - c  may not be able to efficiently detect the additional reference signal. For example, the transmitted reference signal may be narrow or may be transmitted with a relatively low power, and the UE  215 - c  may consume additional power attempting to track the reference signal. In some cases, the UE  215 - c  may not be able to access the reference signal at all; in the example of  FIG. 2 , for instance, the reference signal configuration may be for reference signal  220 - a , which may be inaccessible to UE  215 - c . Further, in some examples, the reference signal configuration may not be recent (e.g., may have been updated since UE  215 - c  received the configuration, and because UE  215 - c  is in idle/inactive mode, UE  215 - c  may be unaware of the update) and UE  215 - c  may not be able to receive the reference signal. Thus, a base station  205  sharing a reference signal configuration with UE  215 - c  may not yield significant power savings (e.g., as compared to UE  215 - c  only receiving SSBs) and, in some cases, may worsen power consumption. Additionally, base station  205  may selectively choose to share the reference signal configuration with UE  215 - c  (e.g., may choose to refrain from sharing the reference signal configuration), in which case UE  215 - c  may continue to receive only SSB  225  and may continue to suffer the associated increased power consumption. 
     While a UE  215  (e.g., UE  215 - c ) operating in idle/inactive mode may not have an active connection with a base station  205 , the UE  215  may be able to communicate with other UEs  215  in the wireless communication system  200  via sidelinks  210  (e.g., by performing a sidelink discovery procedure to establish sidelink communications). Thus, as described herein, to reduce wake-up instances and corresponding power consumption, a UE  215  (e.g., UE  215 - c ) operating in idle/inactive mode may receive a reference signal configuration from a connected mode UE (e.g., UEs  215 - a  and  215 - b ) via a sidelink transmission over a sidelink channel. If the idle/inactive mode UE  215  and the connected mode UE  215  are geographically close to each other, the reference signal configuration may enable the idle/inactive mode UE  215  to receive a reference signal from a base station. For example, UE  215 - b  may be configured with a reference signal configuration used to receive one or more reference signals, including reference signal  220 - b , from base station  205 . UE  215 - b  may transmit, via sidelink  210 - b , a sidelink transmission including the reference signal configuration to UE  215 - c . The reference signal configuration may include resources (e.g., time resources, frequency resources, spatial resources, etc.) corresponding with one or more downlink beams tracked by UE  215 - b . Because UE  215 - c  is in close proximity to UE  215 - b , the downlink beams tracked by UE  215 - b  may be accessible to UE  215 - c . That is, UE  215 - c  may use the reference signal configuration to monitor for and receive one or more reference signals (e.g., reference signal  220 - b ) from the base station  205 . 
     A UE  215  (e.g., UEs  215 - a  and  215 - b ) operating in a connected mode may determine whether to share a reference signal configuration with a UE  215  (e.g., UE  215 - c ) operating in idle/inactive mode based on a trigger condition being satisfied. The trigger condition may include, but is not limited to, a proximity of the idle/inactive mode UE  215  with the connected mode UE  215 . For example, UE  215 - a  may identify an active reference signal configuration for receiving reference signal  220 - a  from base station  205 . If the trigger condition is satisfied, UE  215 - a  may transmit the reference signal configuration as part of a sidelink transmission to UE  215 - c  via sidelink  210 - a . If the trigger condition is not satisfied—for instance, if UE  215 - c  is not in close proximity to UE  215 - a —UE  215 - a  may refrain from transmitting the sidelink transmission that includes the reference signal configuration. As illustrated in  FIG. 2 , reference signal  220 - a  may not be accessible to UE  215 - c , e.g., due to the location of UE  215 - c . UE  215 - a  may thus refrain from sharing a reference signal resource configuration for reference signal  220 - a  with UE  215 - c.    
     In some examples, the connected mode UE  215  (e.g., UE  215 - b ) may be configured with multiple resources for reference signals, where individual reference signal resources each correspond to a downlink beam tracked by the UE  215 . For instance, UE  215 - b  may be configured with resources for an active downlink beam for reference signal  220 - b , as well as resources for one or more additional beams (e.g., beams adjacent to the active downlink beam). UE  215 - b  may selectively transmit the reference signal configuration for some or all of the configured resources. As an example, UE  215 - b  may transmit, and UE  215 - c  may receive, a configuration of reference signal resources corresponding to the active downlink beam. Alternatively, UE  215 - b  may transmit, and UE  215 - c  may receive, a configuration of a subset of reference signal resources, such as resources for the active downlink beam and one or more beams adjacent to the active downlink beam. This may be especially useful to UE  215 - c  if UE  215 - c  and UE  215 - b  are separated by some distance. For example, a beam adjacent to the active downlink beam may provide better performance for the UE  215 - c  than the active downlink beam (e.g., due to the distance between the UEs  215 , a beam direction, etc.). In some other cases, UE  215 - b  may transmit, and UE  215 - c  may receive, a configuration of all reference signal resources configured to UE  215 - b.    
     In some examples, if UE  215 - b  transmits multiple configurations of multiple reference signal resources for multiple beams, UE  215 - b  may assign an order to the resources and transmit the configurations of resources in the assigned order (e.g., in an ordered list). For instance, the reference signal resources may be ordered in the list based on a proximity of respective beams to the active downlink beam. That is, a configuration of reference signal resources for the active downlink beam may be transmitted first, followed by a configuration of reference signal resources for adjacent beams in closest proximity to the active downlink beam, further followed by reference signal resources for adjacent beams in next closest proximity to the active downlink beam, and so on for any additional reference signal resources. UE  215 - c  may thus prioritize using reference signal resources for beams according to the order, e.g., by first using the resources for the active downlink beam to monitor for reference signal  220 - b . If the active downlink beam provides poor performance for UE  215 - c  (e.g., if the active downlink beam is narrow and has a beam direction that is not optimal for UE  215 - c ), UE  215 - c  may use the next reference signal resources in the list to monitor for reference signal  220 - b , and so on. It should be noted that the order described herein is an example for illustrative purposes only, and other orders or assignations may be used. 
     In some aspects, UE  215 - c  may transmit a resource configuration request message to indicate that UE  215 - c  is requesting a resource configuration. UE  215 - c  may transmit the resource configuration request message to one or more other UEs  215  in the wireless communications system  200 . For instance, UE  215 - c  may transmit a resource configuration request message directly (e.g., as a unicast transmission) to UE  215 - b  via sidelink  210 - b . Alternatively, UE  215 - c  may transmit a resource configuration request message to multiple other UEs  215 , such as UEs  215 - a  and  215 - b , e.g., via a groupcast or broadcast transmission. A UE  215  receiving the resource configuration request message, such as UE  215 - a  or UE  215 - b , may determine (e.g., according to satisfaction of a trigger condition) whether to share a resource configuration as described herein with UE  215 - c , and may transmit (or refrain from transmitting) a sidelink transmission including the resource configuration to the UE  215 - c  accordingly. 
     UE  215 - c  may include information in the resource configuration request message for a receiving UE  215  to use in determining the proximity. For instance, UE  215 - c  may transmit a resource configuration request message to UE  215 - a  via sidelink  210 - a . The resource configuration request message may include an indication of a transmit power of the resource configuration request message, physical positioning information of the UE  215 - c , zone information of the UE  215 - c , or other location information of the UE  215 - c , or some combination thereof. UE  215 - a  may determine a path loss based on the transmit power indication and may use the path loss to derive a proximity of the UE  215 - c  to the UE  215 - a . Similarly, UE  215 - a  may use the physical positioning information and/or the zone information to determine the proximity. UE  215 - a  may determine whether a trigger condition is satisfied based on the proximity. If the trigger condition is satisfied, e.g., if UE  215 - c  is in close proximity to UE  215 - a , UE  215 - a  may determine to transmit the reference signal configuration to the UE  215 - c . If the trigger condition is not satisfied, e.g., if UE  215 - c  is not in close proximity to UE  215 - a , UE  215 - a  may refrain from transmitting the reference signal configuration. In the example of  FIG. 2 , UE  215 - a  is configured to receive reference signal  220 - a . UE  215 - a  may determine that UE  215 - c  is not in close proximity and may therefore refrain from sharing the reference signal configuration for reference signal  220 - a.    
     Additionally, or alternatively, UE  215 - a  may select between different resource configurations to transmit to UE  215 - c , e.g., based on the proximity. Continuing the example of  FIG. 2 , UE  215 - a  may select a wide beam reference signal resource configuration (e.g., instead of a narrow beam reference signal resource configuration) to share with UE  215 - c . In contrast, as UE  215 - b  and UE  215 - c  are in close proximity to one another, UE  215 - b  may select a narrow beam resource configuration to share with UE  215 - c.    
     In some cases, UE  215 - c  may receive multiple sidelink transmissions including respective reference signal configurations from multiple connected mode UEs  215 . UE  215 - c  may receive, for example, a reference signal configuration for reference signal  220 - a  from UE  215 - a  and a reference signal configuration for reference signal  220 - b  from UE  215 - b . In such cases, UE  215 - c  may determine a proximity of the UE  215 - c  with each of the UEs  215 - a  and  215 - b . UEs  215 - a  and  215 - b  may include information in the sidelink transmission that UE  215 - c  may use to determine the proximities, such as location information, zone information, or a transmission power of the sidelink transmission (e.g., where UE  215 - c  derives a path loss from the transmit power and determines the proximity based on the path loss). UE  215 - c  may prioritize or select a reference signal configuration from the multiple reference signal configurations based on the proximity. In the example of  FIG. 2 , UE  215 - c  may select the reference signal configuration corresponding to reference signal  220 - b  rather than the reference signal configuration corresponding to reference signal  220 - a , as UE  215 - b  is closer in proximity to UE  215 - c  tha UE  215 - a . That is, a reference signal configuration configured for a UE  215  that is closer in proximity to UE  215 - c  may be more likely to provide optimal performance than a reference signal configuration configured for a UE  215  that is farther from UE  215 - c.    
     An idle/inactive mode UE  215  receiving reference signal configurations may use the reference signal configurations to monitor for and receive at least one reference signal from a base station  205 . The UE  215  may use the at least one reference signal to perform one or more operations based on the type of reference signal. For instance, UE  215 - c  may receive a CSI-RS and may use the CSI-RS for downlink channel estimation, timing and frequency tracking loop updating, AGC loop updating, or serving cell RRM measurement(s). Additionally, or alternatively, UE  215 - c  may receive a PRS, and may use the PRS for downlink-based positioning. 
       FIG. 3  illustrates an example of a transmission diagram  300  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. Transmission diagram  300  may implement aspects of wireless communications systems  100  or  200 . For example, transmission diagram  300  may be an example of transmission occasions for a UE in an idle or inactive mode, such as UE  215 - c  described with reference to  FIG. 2 . The UE may be configured to monitor for transmissions from a base station in each corresponding occasion, where each occasion has a given periodicity. For example, as illustrated in  FIG. 3 , SSBs  310  and reference signals (RSs)  315  may have a 20 ms periodicity with a 10 ms offset between SSBs  310  and RSs  315 . The UE may also monitor for and receive a paging message over a downlink channel during a paging occasion (PO)  320 . 
     A UE in idle/inactive mode may be configured to periodically wake up to monitor for and receive SSBs  310  according to the configured periodicity (e.g., every 20 ms, as illustrated in  FIG. 3 ). The UE may not be configured to receive other RSs  315 , such as CSI-RSs, PRSs, or TRSs, as such RSs  315  may only be available to connected mode UEs. In comparison to other RSs  315 , SSBs  310  may be transmitted with a low transmit power, a low periodicity, or in a limited bandwidth. The UE may use the SSBs  310  to perform tracking, synchronization, or other measurements or operations, for example, to obtain parameters for a downlink channel used to receive a paging message during PO  320 . 
     However, due to the low transmit power, limited bandwidth, and/or low periodicity, the UE may not be able to perform enough measurements to find the downlink channel using a single SSB  310 . That is, a UE configured only for SSBs  310  (and not RSs  315 ) may need to wake up and monitor for multiple SSBs  310  to obtain sufficient signal energy to monitor for a paging message during PO  320 . Poor channel conditions, such as a low SNR, may increase the number of SSBs  310 . A UE with limited capabilities (e.g., a REDCAP UE) may suffer further decreased performance if conditions are poor. 
     In the example illustrated in  FIG. 3 , the UE may receive an SSB  310  every 20 ms (e.g., SSBs  310  are received with a 20 ms periodicity). The UE may receive a first SSB  310  and may use the SSB  310  to perform one or more reference signal operations, such as channel measurements, used to monitor for and receive a paging message during PO  320 . If the UE is unable to obtain sufficient signal energy using only the first SSB  310 , the UE may wait 20 ms to receive a second SSB  310 . The UE may use the second SSB  310  to continue making measurements or performing operations. If the UE is still unable to obtain sufficient signal energy after the second SSB  310 , the UE may wait another 20 ms to receive a third SSB  310 , and so on. Thus, the UE may take a relatively long time (e.g., as compared to a connected mode UE receiving other reference signals) to obtain channel energy and receive a paging message, which may in turn increase system overhead and decrease efficiency. In the example of  FIG. 3 , the UE may receive three SSBs  310 , and may therefore take 60 ms to perform sufficient measurements to monitor for PO  320 . Additionally, the UE wakes up to receive each SSB  310 . As waking up consumes considerable power at the UE, increasing the number of SSBs  310  needed (and, thus, the number of wake up instances) may increase the power consumption. The number of SSBs  310  needed may further increase due to poor channel conditions, low transmit power, or other examples. 
     As described herein, to mitigate such inefficiencies and increased power consumption, the UE may receive one or more reference signal configurations from one or more connected mode UEs. The UE may use the reference signal configurations to monitor for and receive RSs  315  (e.g., in addition to receiving SSBs  310 ) from a base station according to a configured periodicity. Configuring the UE with additional RSs  315  may reduce the number of wakeup instances and/or a total wakeup duration. For example, the UE may wake up once to receive both an SSB  310  and an RS  315 , and may be able to perform sufficient measurements to find the downlink channel within the wakeup duration. In the example of  FIG. 3 , the UE may receive an SSB  310  and an RS  315  every 20 ms with a 10 ms offset. Thus, the UE may perform sufficient measurements to monitor for and receive the PO  320  in 10 ms, as compared to 60 ms in the example described above. Reducing the number of wakeup instances and wakeup duration may save power at the UE and increase efficiency, as the UE may perform operations to find the downlink channel more quickly (e.g., as compared to a UE only receiving SSBs). 
     While poor channel conditions may increase the number of wakeup instances needed by a UE configured with both SSBs  310  and RSs  315 , the total number of wakeup instances may still be fewer when compared to a UE configured with only SSBs  310 . In the example of  FIG. 3 , if channel conditions are favorable (e.g., SINR is high), the UE may only need to receive one SSB  310  before receiving PO  320 . If channel conditions decrease (e.g., SINR is relatively medium), the UE may receive three SSBs  310  and/or RSs  315  to receive PO  320 . Due to the offset between the periodicities of the SSBs  310  and RSs  315 , however, the total time elapsed to receive three SSBs  310  and/or RSs  315  may be reduced (e.g., from 60 ms in the example described above) to 30 ms. At low channel conditions (e.g., low SINR), the UE may receive five SSBs  310  and/or RSs  315  for a total time elapsed of 50 ms. Reducing the periodicity of RSs  315  may further reduce the total time elapsed. 
       FIG. 4  illustrates an example of a process flow  400  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. In some examples, the process flow  400  may implement aspects of wireless communication systems  100  or  200 . For example, process flow  400  may include a base station  405  and UEs  415 , which may be examples of corresponding wireless devices as described herein. In the following description of the process flow  400 , the operations between the UEs  415  and the base station  405  may be transmitted in a different order than the exemplary order shown, or the operations performed by the UEs  415  and the base station  405  may be performed in different orders or at different times. Certain operations may also be left out of the process flow  400 , or other operations may be added to the process flow  400 . It is to be understood that while the UEs  415  and the base station  405  are shown performing operations of process flow  400 , any wireless device may perform the operations shown. 
     In the process flow  400 , UE  415 - a  may be operating in an active or connected mode and may have an active connection (e.g., an RRC connection) with base station  405 . UE  415 - b  may be operating in an idle or inactive mode (e.g., may not have an active connection with base station  405 ). UE  415 - a  and UE  415 - b  may communicate with one another via a sidelink connection. In some examples, UE  415 - a  and/or UE  415 - b  may communicate, via sidelink transmissions, with one or more additional UEs  415  (not shown). UE  415 - a  may be configured with one or more reference signal configurations to receive one or more reference signals from base station  405 . The one or more reference signals may include, but are not limited to, a CSI-RS, a TRS, and/or a PRS. 
     At  420 , UE  415 - a  may identify one or more reference signal configurations that are active at the UE  415 - a . For example, UE  415 - a  may be configured with multiple reference signal configurations, and a subset of the reference signal configurations may be active (e.g., such that UE  415 - a  tracks a downlink beam used to receive the associated reference signals from base station  405 ). 
     At  425 , UE  415 - b  may optionally transmit a reference signal configuration request message. UE  415 - b  may transmit the reference signal configuration request message as a sidelink transmission over a sidelink channel, for instance, as a unicast transmission, a broadcast transmission, or a groupcast transmission. UE  415 - a  may receive the reference signal configuration request message. In some examples, UE  415 - b  may transmit, as part of the reference signal configuration request message, physical positioning information of the UE  415 - b , zone information of the UE  415 - b , or some combination thereof. Additionally or alternatively, UE  415 - b  may transmit, as part of the reference signal configuration request message, an indication of a transmit power of the reference signal configuration request message. 
     At  430 , UE  415 - a  may determine a proximity of the UE  415 - a  to UE  415 - b . In some examples, UE  415 - a  may use the zone information, location information, or transmit power indication transmitted as part of the reference signal configuration request message at  425 . For instance, UE  415 - a  may use the transmit power indication to derive a path loss and may determine the proximity based on the path loss. 
     At  435 , UE  415 - a  may determine whether to transmit a reference signal configuration (e.g., of the one or more reference signal configurations identified at  420 ) to UE  415 - b  over a sidelink channel. The determining may be based on whether a trigger condition is satisfied. As an example, at  430 , UE  415 - a  may determine the proximity, and at  435 , UE  415 - a  may determine whether the trigger condition is satisfied based on the proximity. In some cases, the trigger condition may be satisfied if UE  415 - b  is close in proximity to UE  415 - a  and/or not satisfied if UE  415 - b  is far from UE  415 - a . If, for example, UE  415 - b  is far from UE  415 - a  (e.g., the trigger condition is not satisfied), a reference signal configuration for UE  415 - a  may not be useful for UE  415 - b  (e.g., UE  415 - b  may not be able to access a reference signal associated with the reference signal configuration). Thus, UE  415 - a  may determine to refrain from transmitting the reference signal configuration to UE  415 - b . Alternatively, if UE  415 - b  is close in proximity to UE  415 - a  (e.g., the trigger condition is satisfied), a reference signal configuration for UE  415 - a  may be used by UE  415 - b  to receive an associated reference signal; as such, UE  415 - a  may determine to transmit the reference signal configuration to UE  415 - b.    
     In some cases, at  435 , UE  415 - a  may also select between two or more of the reference signal configurations identified at  420 . In some examples, UE  415 - a  may select the reference signal configuration to transmit based on the proximity determined at  430 . For instance, UE  415 - a  may identify (e.g., at  420 ) a narrow beam reference signal configuration and a wide beam reference signal configuration. If, at  430 , UE  415 - a  determines that UE  415 - b  is close in proximity to UE  415 - a , UE  415 - a  may select the narrow beam reference signal configuration. Alternatively, if UE  415 - a  determines that UE  415 - b  is far from UE  415 - a , UE  415 - a  may select the wide beam reference signal configuration (e.g., such that an associated reference signal may be received by UE  415 - b  despite UE  415 - b  being far from UE  415 - a ). 
     At  440 , UE  415 - a  may transmit the reference signal configuration (e.g., determined at  435 ) to UE  415 - b  via a sidelink transmission over a sidelink channel. In some examples, UE  415 - a  may transmit the sidelink transmission including the reference signal configuration based on the trigger condition being satisfied. The sidelink transmission may be transmitted as a unicast transmission, a groupcast transmission, or a broadcast transmission. In some cases, UE  415 - b  may receive the sidelink transmission based on the reference signal configuration request message transmitted at  425 . 
     The sidelink transmission that includes the reference signal configuration may include reference signal resources that UE  415 - b  may use to monitor for and receive a reference signal from base station  405 . The reference signal resources may correspond with an active downlink beam tracked by UE  415 - a . In some examples, the reference signal resources may correspond with an active downlink beam tracked by UE  415 - a  and with one or more beams adjacent to the active downlink beam. In some cases, the reference signal resources may be all reference signal resources that are configured to UE  415 - a . The reference signal resources may be ordered based on a proximity of respective beams to the active downlink beam. For instance, UE  415 - a  may transmit, and UE  415 - b  may receive, reference signal resources in an ordered list in accordance with an order. Individual reference signal resources in the list may each correspond to a beam tracked by UE  415 - a , and the order may be based on the proximity of each respective beam to the active downlink beam. 
     In some examples, UE  415 - a  may include, in the sidelink transmission, an indication of a transmit power of the sidelink transmission, physical positioning information of the UE  415 - a , zone information of the UE  415 - a , or some combination thereof. 
     In some examples, at  440 , UE  415 - b  may receive, from one or more additional UEs  415  (not shown), one or more additional sidelink transmissions. Each additional sidelink transmission may include respective reference signal configurations for receiving reference signals from base station  405 . 
     At  445 , UE  415 - b  may determine a proximity of UE  415 - a  to UE  415 - b . In some examples, UE  415 - b  may use the zone information, location information, or transmit power indication that was included as part of the sidelink transmission received at  440 . For instance, UE  415 - b  may use the transmit power indication to derive a path loss and may determine the proximity based on the path loss. If UE  415 - b  received (e.g., at  440 ) additional sidelink transmissions from additional UEs  415 , UE  415 - b  may similarly determine a proximity of UE  415 - b  with each of the additional UEs  415 . 
     If, at  440 , UE  415 - b  receives any additional sidelink transmissions from other UEs  415 , UE  415 - b  may select, at  450 , a reference signal configuration from the received reference signal configurations. In some examples, UE  415 - b  may select a reference signal configuration based on a proximity of UE  415 - b  with each UE  415  that transmitted a reference signal configuration. For instance, a UE  415  in closer proximity to UE  415 - b  may have a reference signal configuration for a reference signal that is more likely to be accessible to UE  415 - b  as compared to a UE  415  that is farther from UE  415 - b . UE  415 - b  may thus select a reference signal configuration that was transmitted by a UE  415  that is closer in proximity to UE  415 - b.    
     At  455 , UE  415 - b  may use the received and/or selected reference signal configuration to monitor for one or more reference signals. In some cases, UE  415 - b  may use the reference signal configuration for monitoring for the one or more reference signals based on the proximity of the UE  415 - b  to the UE  415  that transmitted the reference signal configuration. 
     At  460 , UE  415 - b  may receive at least one reference signal from base station  405  based on the monitoring performed at  455 . The reference signal may include, but is not limited to, a CSI-RS, a TRS, or a PRS. 
     At  465 , UE  415 - b  may optionally use the received reference signal(s) to perform one or more operations, e.g., based on the received reference signal. For example, if the received reference signal is a CSI-RS, UE  415 - b  may use the CSI-RS for downlink channel estimation, timing and frequency tracking loop updating, AGC loop updating, or serving cell RRM measurement, or some combination thereof. If the received reference signal is a PRS, UE  415 - b  may use the PRS for downlink-based positioning. 
       FIG. 5  shows a block diagram  500  of a device  505  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The device  505  may be an example of aspects of a UE  115  as described herein. The device  505  may include a receiver  510 , a transmitter  515 , and a communications manager  520 . The device  505  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  510  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to UE idle and inactive mode enhancement with sidelink). Information may be passed on to other components of the device  505 . The receiver  510  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  515  may provide a means for transmitting signals generated by other components of the device  505 . For example, the transmitter  515  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to UE idle and inactive mode enhancement with sidelink). In some examples, the transmitter  515  may be co-located with a receiver  510  in a transceiver module. The transmitter  515  may utilize a single antenna or a set of multiple antennas. 
     The communications manager  520 , the receiver  510 , the transmitter  515 , or various combinations thereof or various components thereof may be examples of means for performing various aspects of UE idle and inactive mode enhancement with sidelink as described herein. For example, the communications manager  520 , the receiver  510 , the transmitter  515 , or various combinations or components thereof may support a method for performing one or more of the functions described herein. 
     In some examples, the communications manager  520 , the receiver  510 , the transmitter  515 , or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some examples, a processor and memory coupled with the processor may be configured to perform one or more of the functions described herein (e.g., by executing, by the processor, instructions stored in the memory). 
     Additionally or alternatively, in some examples, the communications manager  520 , the receiver  510 , the transmitter  515 , or various combinations or components thereof may be implemented in code (e.g., as communications management software or firmware) executed by a processor. If implemented in code executed by a processor, the functions of the communications manager  520 , the receiver  510 , the transmitter  515 , or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a central processing unit (CPU), an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in the present disclosure). 
     In some examples, the communications manager  520  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  510 , the transmitter  515 , or both. For example, the communications manager  520  may receive information from the receiver  510 , send information to the transmitter  515 , or be integrated in combination with the receiver  510 , the transmitter  515 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  520  may support wireless communication at a first UE in accordance with examples as disclosed herein. For example, the communications manager  520  may be configured as or otherwise support a means for receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The communications manager  520  may be configured as or otherwise support a means for monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The communications manager  520  may be configured as or otherwise support a means for receiving at least one reference signal from the base station based on the monitoring. 
     Additionally or alternatively, the communications manager  520  may support wireless communication at a first UE in accordance with examples as disclosed herein. For example, the communications manager  520  may be configured as or otherwise support a means for identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The communications manager  520  may be configured as or otherwise support a means for determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The communications manager  520  may be configured as or otherwise support a means for transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     By including or configuring the communications manager  520  in accordance with examples as described herein, the device  505  (e.g., a processor controlling or otherwise coupled to the receiver  510 , the transmitter  515 , the communications manager  520 , or a combination thereof) may support techniques for a connected mode UE sharing reference signal configurations with an idle/inactive mode UE via sidelink transmissions. A device  505  (e.g., an idle/inactive mode UE) may therefore receive additional reference signals from a base station without having an active connection with the base station. The device  505  may thus reduce an overall wakeup time and reduce the time elapsed before being able to receive a paging message from the base station, which may in turn reduce power consumption and conserve battery power at the device  505 . 
     receiving, while in an idle/inactive mode, one or more reference signal configurations via sidelink transmissions from a connected mode UE. The device  505  may use the reference signal configuration(s) to receive, from a base station one or more reference signals that are configured for the connected mode UE without the device  505  having an active connection with the base station. The device  505  may therefore receive reference signals more frequently, which may in turn decrease the elapsed time the device  505  takes before being able to receive a paging message. Further, receiving reference signals more frequently may decrease a total wakeup time at the device  505 , thereby decreasing power consumption at the device  505 . 
       FIG. 6  shows a block diagram  600  of a device  605  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The device  605  may be an example of aspects of a device  505  or a UE  115  as described herein. The device  605  may include a receiver  610 , a transmitter  615 , and a communications manager  620 . The device  605  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  610  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to UE idle and inactive mode enhancement with sidelink). Information may be passed on to other components of the device  605 . The receiver  610  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  615  may provide a means for transmitting signals generated by other components of the device  605 . For example, the transmitter  615  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to UE idle and inactive mode enhancement with sidelink). In some examples, the transmitter  615  may be co-located with a receiver  610  in a transceiver module. The transmitter  615  may utilize a single antenna or a set of multiple antennas. 
     The device  605 , or various components thereof, may be an example of means for performing various aspects of UE idle and inactive mode enhancement with sidelink as described herein. For example, the communications manager  620  may include a sidelink transmission receiver  625 , a reference signal monitoring component  630 , a reference signal receiver  635 , an RS configuration identifying component  640 , a trigger condition component  645 , an RS configuration transmitter  650 , or any combination thereof. The communications manager  620  may be an example of aspects of a communications manager  520  as described herein. In some examples, the communications manager  620 , or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  610 , the transmitter  615 , or both. For example, the communications manager  620  may receive information from the receiver  610 , send information to the transmitter  615 , or be integrated in combination with the receiver  610 , the transmitter  615 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  620  may support wireless communication at a first UE in accordance with examples as disclosed herein. The sidelink transmission receiver  625  may be configured as or otherwise support a means for receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The reference signal monitoring component  630  may be configured as or otherwise support a means for monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The reference signal receiver  635  may be configured as or otherwise support a means for receiving at least one reference signal from the base station based on the monitoring. 
     Additionally or alternatively, the communications manager  620  may support wireless communication at a first UE in accordance with examples as disclosed herein. The RS configuration identifying component  640  may be configured as or otherwise support a means for identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The trigger condition component  645  may be configured as or otherwise support a means for determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The RS configuration transmitter  650  may be configured as or otherwise support a means for transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
       FIG. 7  shows a block diagram  700  of a communications manager  720  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The communications manager  720  may be an example of aspects of a communications manager  520 , a communications manager  620 , or both, as described herein. The communications manager  720 , or various components thereof, may be an example of means for performing various aspects of UE idle and inactive mode enhancement with sidelink as described herein. For example, the communications manager  720  may include a sidelink transmission receiver  725 , a reference signal monitoring component  730 , a reference signal receiver  735 , an RS configuration identifying component  740 , a trigger condition component  745 , an RS configuration transmitter  750 , an RS configuration request transmitter  755 , a CSI-RS component  760 , an PRS component  765 , an RS configuration request receiver  770 , a proximity determining component  775 , an RS configuration component  780 , or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The communications manager  720  may support wireless communication at a first UE in accordance with examples as disclosed herein. The sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The reference signal monitoring component  730  may be configured as or otherwise support a means for monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The reference signal receiver  735  may be configured as or otherwise support a means for receiving at least one reference signal from the base station based on the monitoring. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving reference signal resources that correspond with an active downlink beam tracked by the second UE. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving reference signal resources that correspond with an active downlink beam tracked by the second UE and with one or more beams adjacent to the active downlink beam. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving all reference signal resources configured to the second UE. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving a set of multiple reference signal resources configured to the second UE in an ordered list in accordance with an order, where individual reference signal resources of the set of multiple reference signal resources each correspond to a beam tracked by the second UE, and where the order is based on proximity of respective beams to an active downlink beam tracked by the second UE. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving, as part of the sidelink transmission, an indication of a transmit power used by the second UE for transmitting the sidelink transmission, physical positioning information of the second UE, zone information of the second UE, or some combination thereof. 
     In some examples, the proximity determining component  775  may be configured as or otherwise support a means for determining a proximity of the first UE to the second UE based on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof. In some examples, the reference signal monitoring component  730  may be configured as or otherwise support a means for using the reference signal configuration for monitoring for the one or more reference signals based on the proximity of the first UE to the second UE. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving a set of multiple sidelink transmissions from the set of multiple UEs, each of the set of multiple sidelink transmissions including respective reference signal configurations for receiving the one or more reference signals from the base station. 
     In some examples, the RS configuration component  780  may be configured as or otherwise support a means for selecting the reference signal configuration from the set of multiple sidelink transmissions based on a proximity of the first UE with each of the set of multiple UEs. 
     In some examples, the RS configuration request transmitter  755  may be configured as or otherwise support a means for transmitting a reference signal configuration request message, where the sidelink transmission is received based on the reference signal configuration request message. 
     In some examples, to support transmitting the reference signal configuration request message, the RS configuration request transmitter  755  may be configured as or otherwise support a means for transmitting, as part of the reference signal configuration request message, an indication of a transmit power of the reference signal configuration request message, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     In some examples, to support transmitting the reference signal configuration request message, the RS configuration request transmitter  755  may be configured as or otherwise support a means for transmitting the reference signal configuration request message as one of a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     In some examples, the at least one reference signal includes a CSI-RS, and the CSI-RS component  760  may be configured as or otherwise support a means for using the CSI-RS for one or more of downlink channel estimation, timing and frequency tracking updating, AGC loop updating, or serving cell RRM measurement. 
     In some examples, the at least one reference signal includes a PRS, and the PRS component  765  may be configured as or otherwise support a means for using the PRS for downlink-based positioning. 
     In some examples, to support receiving the sidelink transmission that includes the reference signal configuration, the sidelink transmission receiver  725  may be configured as or otherwise support a means for receiving the sidelink transmission over the sidelink channel via one of a unicast transmission, a groupcast transmission, or a broadcast transmission. 
     In some examples, the first UE is in an RRC idle mode or an inactive mode. 
     Additionally or alternatively, the communications manager  720  may support wireless communication at a first UE in accordance with examples as disclosed herein. The RS configuration identifying component  740  may be configured as or otherwise support a means for identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The trigger condition component  745  may be configured as or otherwise support a means for determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The RS configuration transmitter  750  may be configured as or otherwise support a means for transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     In some examples, to support transmitting the reference signal configuration, the RS configuration transmitter  750  may be configured as or otherwise support a means for transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE. 
     In some examples, to support transmitting the reference signal configuration, the RS configuration transmitter  750  may be configured as or otherwise support a means for transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE and with one or more beams adjacent to the active downlink beam. 
     In some examples, to support transmitting the reference signal configuration, the RS configuration transmitter  750  may be configured as or otherwise support a means for transmitting all reference signal resources configured to the first UE. 
     In some examples, to support transmitting the reference signal configuration, the RS configuration transmitter  750  may be configured as or otherwise support a means for transmitting a set of multiple reference signal resources configured to the first UE in an ordered list in accordance with an order, where individual reference signal resources of the set of multiple reference signal resources each correspond to a beam tracked by the first UE, and where the order is based on proximity of respective beams to an active downlink beam tracked by the first UE. 
     In some examples, the sidelink transmission includes an indication of a transmit power of the sidelink transmission, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     In some examples, the RS configuration request receiver  770  may be configured as or otherwise support a means for receiving, from the second UE, a reference signal configuration request message, where the sidelink transmission is transmitted based on the reference signal configuration request message. 
     In some examples, the RS configuration request receiver  770  may be configured as or otherwise support a means for receiving, as part of the reference signal configuration request message, an indication of a transmit power used by the second UE to transmit the reference signal configuration request message, physical positioning information of the second UE, zone information of the second UE, or some combination thereof. In some examples, the proximity determining component  775  may be configured as or otherwise support a means for determining a proximity of the first UE to the second UE based on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof. In some examples, the trigger condition component  745  may be configured as or otherwise support a means for determining whether the trigger condition is satisfied based on the proximity. 
     In some examples, the RS configuration component  780  may be configured as or otherwise support a means for selecting between a narrow beam reference signal configuration and a wide beam reference signal configuration based on the proximity. 
     In some examples, the one or more reference signals include a CSI-RS or a positioning reference signal PRS. 
     In some examples, the sidelink transmission is transmitted as a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     In some examples, the first UE is in a connected mode. 
       FIG. 8  shows a diagram of a system  800  including a device  805  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The device  805  may be an example of or include the components of a device  505 , a device  605 , or a UE  115  as described herein. The device  805  may communicate wirelessly with one or more base stations  105 , UEs  115 , or any combination thereof. The device  805  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager  820 , an input/output (I/O) controller  810 , a transceiver  815 , an antenna  825 , a memory  830 , code  835 , and a processor  840 . These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus  845 ). 
     The I/O controller  810  may manage input and output signals for the device  805 . The I/O controller  810  may also manage peripherals not integrated into the device  805 . In some cases, the I/O controller  810  may represent a physical connection or port to an external peripheral. In some cases, the I/O controller  810  may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. Additionally or alternatively, the I/O controller  810  may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller  810  may be implemented as part of a processor, such as the processor  840 . In some cases, a user may interact with the device  805  via the I/O controller  810  or via hardware components controlled by the I/O controller  810 . 
     In some cases, the device  805  may include a single antenna  825 . However, in some other cases, the device  805  may have more than one antenna  825 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver  815  may communicate bi-directionally, via the one or more antennas  825 , wired, or wireless links as described herein. For example, the transceiver  815  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  815  may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas  825  for transmission, and to demodulate packets received from the one or more antennas  825 . The transceiver  815 , or the transceiver  815  and one or more antennas  825 , may be an example of a transmitter  515 , a transmitter  615 , a receiver  510 , a receiver  610 , or any combination thereof or component thereof, as described herein. 
     The memory  830  may include random access memory (RAM) and read-only memory (ROM). The memory  830  may store computer-readable, computer-executable code  835  including instructions that, when executed by the processor  840 , cause the device  805  to perform various functions described herein. The code  835  may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code  835  may not be directly executable by the processor  840  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some cases, the memory  830  may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  840  may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor  840  may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor  840 . The processor  840  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  830 ) to cause the device  805  to perform various functions (e.g., functions or tasks supporting UE idle and inactive mode enhancement with sidelink). For example, the device  805  or a component of the device  805  may include a processor  840  and memory  830  coupled to the processor  840 , the processor  840  and memory  830  configured to perform various functions described herein. 
     The communications manager  820  may support wireless communication at a first UE in accordance with examples as disclosed herein. For example, the communications manager  820  may be configured as or otherwise support a means for receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The communications manager  820  may be configured as or otherwise support a means for monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The communications manager  820  may be configured as or otherwise support a means for receiving at least one reference signal from the base station based on the monitoring. 
     Additionally or alternatively, the communications manager  820  may support wireless communication at a first UE in accordance with examples as disclosed herein. For example, the communications manager  820  may be configured as or otherwise support a means for identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The communications manager  820  may be configured as or otherwise support a means for determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The communications manager  820  may be configured as or otherwise support a means for transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. 
     By including or configuring the communications manager  820  in accordance with examples as described herein, the device  805  may support techniques for a connected mode UE sharing reference signal configurations with an idle/inactive mode UE via sidelink transmissions. A device  805  (e.g., an idle/inactive mode UE) may therefore receive additional reference signals from a base station without having an active connection with the base station. The device  805  may thus reduce an overall wakeup time and reduce the time elapsed before being able to receive a paging message from the base station, thereby reducing system overhead and increasing system efficiency. 
     In some examples, the communications manager  820  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver  815 , the one or more antennas  825 , or any combination thereof. Although the communications manager  820  is illustrated as a separate component, in some examples, one or more functions described with reference to the communications manager  820  may be supported by or performed by the processor  840 , the memory  830 , the code  835 , or any combination thereof. For example, the code  835  may include instructions executable by the processor  840  to cause the device  805  to perform various aspects of UE idle and inactive mode enhancement with sidelink as described herein, or the processor  840  and the memory  830  may be otherwise configured to perform or support such operations. 
       FIG. 9  shows a flowchart illustrating a method  900  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The operations of the method  900  may be implemented by a UE or its components as described herein. For example, the operations of the method  900  may be performed by a UE  115  as described with reference to  FIGS. 1 through 8 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  905 , the method may include receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The operations of  905  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  905  may be performed by a sidelink transmission receiver  725  as described with reference to  FIG. 7 . 
     At  910 , the method may include monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The operations of  910  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  910  may be performed by a reference signal monitoring component  730  as described with reference to  FIG. 7 . 
     At  915 , the method may include receiving at least one reference signal from the base station based on the monitoring. The operations of  915  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  915  may be performed by a reference signal receiver  735  as described with reference to  FIG. 7 . 
       FIG. 10  shows a flowchart illustrating a method  1000  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The operations of the method  1000  may be implemented by a UE or its components as described herein. For example, the operations of the method  1000  may be performed by a UE  115  as described with reference to  FIGS. 1 through 8 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1005 , the method may include receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station. The operations of  1005  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1005  may be performed by a sidelink transmission receiver  725  as described with reference to  FIG. 7 . 
     At  1010 , the method may include receiving a set of multiple reference signal resources configured to the second UE in an ordered list in accordance with an order, where individual reference signal resources of the set of multiple reference signal resources each correspond to a beam tracked by the second UE, and where the order is based on proximity of respective beams to an active downlink beam tracked by the second UE. The operations of  1010  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1010  may be performed by a sidelink transmission receiver  725  as described with reference to  FIG. 7 . 
     At  1015 , the method may include monitoring for the one or more reference signals based on the reference signal configuration received from the second UE. The operations of  1015  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1015  may be performed by a reference signal monitoring component  730  as described with reference to  FIG. 7 . 
     At  1020 , the method may include receiving at least one reference signal from the base station based on the monitoring. The operations of  1020  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1020  may be performed by a reference signal receiver  735  as described with reference to  FIG. 7 . 
     At  1025 , the method may include using the CSI-RS for one or more of downlink channel estimation, timing and frequency tracking updating, automatic gain control (AGC) loop updating, or serving cell radio resource management (RRM) measurement. The operations of  1025  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1025  may be performed by a CSI-RS component  760  as described with reference to  FIG. 7 . 
       FIG. 11  shows a flowchart illustrating a method  1100  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The operations of the method  1100  may be implemented by a UE or its components as described herein. For example, the operations of the method  1100  may be performed by a UE  115  as described with reference to  FIGS. 1 through 8 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1105 , the method may include identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The operations of  1105  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1105  may be performed by an RS configuration identifying component  740  as described with reference to  FIG. 7 . 
     At  1110 , the method may include determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The operations of  1110  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1110  may be performed by a trigger condition component  745  as described with reference to  FIG. 7 . 
     At  1115 , the method may include transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. The operations of  1115  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1115  may be performed by an RS configuration transmitter  750  as described with reference to  FIG. 7 . 
       FIG. 12  shows a flowchart illustrating a method  1200  that supports UE idle and inactive mode enhancement with sidelink in accordance with aspects of the present disclosure. The operations of the method  1200  may be implemented by a UE or its components as described herein. For example, the operations of the method  1200  may be performed by a UE  115  as described with reference to  FIGS. 1 through 8 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1205 , the method may include identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station. The operations of  1205  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1205  may be performed by an RS configuration identifying component  740  as described with reference to  FIG. 7 . 
     At  1210 , the method may include receiving, from the second UE, a reference signal configuration request message, where the sidelink transmission is transmitted based on the reference signal configuration request message. The operations of  1210  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1210  may be performed by an RS configuration request receiver  770  as described with reference to  FIG. 7 . 
     At  1215 , the method may include receiving, as part of the reference signal configuration request message, an indication of a transmit power used by the second UE to transmit the reference signal configuration request message, physical positioning information of the second UE, zone information of the second UE, or some combination thereof. The operations of  1215  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1215  may be performed by an RS configuration request receiver  770  as described with reference to  FIG. 7 . 
     At  1220 , the method may include determining a proximity of the first UE to the second UE based on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof. The operations of  1220  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1220  may be performed by a proximity determining component  775  as described with reference to  FIG. 7 . 
     At  1225 , the method may include determining whether the trigger condition is satisfied based on the proximity. The operations of  1225  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1225  may be performed by a trigger condition component  745  as described with reference to  FIG. 7 . 
     At  1230 , the method may include determining to transmit the reference signal configuration over a sidelink channel based on satisfaction of a trigger condition. The operations of  1230  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1230  may be performed by a trigger condition component  745  as described with reference to  FIG. 7 . 
     At  1235 , the method may include transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based on the trigger condition being satisfied. The operations of  1235  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1235  may be performed by an RS configuration transmitter  750  as described with reference to  FIG. 7 . 
     The following provides an overview of aspects of the present disclosure: 
     Aspect 1: A method for wireless communication at a first UE, comprising: receiving, from a second UE and over a sidelink channel, a sidelink transmission that includes a reference signal configuration for receiving one or more reference signals from a base station; monitoring for the one or more reference signals based at least in part on the reference signal configuration received from the second UE; and receiving at least one reference signal from the base station based at least in part on the monitoring. 
     Aspect 2: The method of aspect 1, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving reference signal resources that correspond with an active downlink beam tracked by the second UE. 
     Aspect 3: The method of any of aspects 1 through 2, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving reference signal resources that correspond with an active downlink beam tracked by the second UE and with one or more beams adjacent to the active downlink beam. 
     Aspect 4: The method of any of aspects 1 through 3, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving all reference signal resources configured to the second UE. 
     Aspect 5: The method of any of aspects 1 through 4, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving a plurality of reference signal resources configured to the second UE in an ordered list in accordance with an order, wherein individual reference signal resources of the plurality of reference signal resources each correspond to a beam tracked by the second UE, and wherein the order is based at least in part on proximity of respective beams to an active downlink beam tracked by the second UE. 
     Aspect 6: The method of any of aspects 1 through 5, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving, as part of the sidelink transmission, an indication of a transmit power used by the second UE for transmitting the sidelink transmission, physical positioning information of the second UE, zone information of the second UE, or some combination thereof. 
     Aspect 7: The method of aspect 6, further comprising: determining a proximity of the first UE to the second UE based at least in part on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof; and using the reference signal configuration for monitoring for the one or more reference signals based at least in part on the proximity of the first UE to the second UE. 
     Aspect 8: The method of any of aspects 1 through 7, wherein the second UE is one of a plurality of UEs, and wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving a plurality of sidelink transmissions from the plurality of UEs, each of the plurality of sidelink transmissions comprising respective reference signal configurations for receiving the one or more reference signals from the base station. 
     Aspect 9: The method of aspect 8, further comprising: selecting the reference signal configuration from the plurality of sidelink transmissions based at least in part on a proximity of the first UE with each of the plurality of UEs. 
     Aspect 10: The method of any of aspects 1 through 9, further comprising: transmitting a reference signal configuration request message, wherein the sidelink transmission is received based at least in part on the reference signal configuration request message. 
     Aspect 11: The method of aspect 10, wherein transmitting the reference signal configuration request message comprises: transmitting, as part of the reference signal configuration request message, an indication of a transmit power of the reference signal configuration request message, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     Aspect 12: The method of any of aspects 10 through 11, wherein transmitting the reference signal configuration request message comprises: transmitting the reference signal configuration request message as one of a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     Aspect 13: The method of any of aspects 1 through 12, wherein the at least one reference signal comprises a CSI-RS, the method further comprising: using the CSI-RS for one or more of downlink channel estimation, timing and frequency tracking updating, AGC loop updating, or serving cell RRM measurement. 
     Aspect 14: The method of any of aspects 1 through 13, wherein the at least one reference signal comprises a PRS, the method further comprising: using the PRS for downlink-based positioning. 
     Aspect 15: The method of any of aspects 1 through 14, wherein receiving the sidelink transmission that includes the reference signal configuration comprises: receiving the sidelink transmission over the sidelink channel via one of a unicast transmission, a groupcast transmission, or a broadcast transmission. 
     Aspect 16: The method of any of aspects 1 through 15, wherein the first UE is in an RRC idle mode or an inactive mode. 
     Aspect 17: A method for wireless communication at a first UE, comprising: identifying a reference signal configuration that is active at the first UE for receiving one or more reference signals from a base station; determining to transmit the reference signal configuration over a sidelink channel based at least in part on satisfaction of a trigger condition; and transmitting the reference signal configuration via a sidelink transmission over the sidelink channel to a second UE based at least in part on the trigger condition being satisfied. 
     Aspect 18: The method of aspect 17, wherein transmitting the reference signal configuration comprises: transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE. 
     Aspect 19: The method of any of aspects 17 through 18, wherein transmitting the reference signal configuration comprises: transmitting reference signal resources that correspond with an active downlink beam tracked by the first UE and with one or more beams adjacent to the active downlink beam. 
     Aspect 20: The method of any of aspects 17 through 19, wherein transmitting the reference signal configuration comprises: transmitting all reference signal resources configured to the first UE. 
     Aspect 21: The method of any of aspects 17 through 20, wherein transmitting the reference signal configuration comprises: transmitting a plurality of reference signal resources configured to the first UE in an ordered list in accordance with an order, wherein individual reference signal resources of the plurality of reference signal resources each correspond to a beam tracked by the first UE, and wherein the order is based at least in part on proximity of respective beams to an active downlink beam tracked by the first UE. 
     Aspect 22: The method of any of aspects 17 through 21, wherein the sidelink transmission includes an indication of a transmit power of the sidelink transmission, physical positioning information of the first UE, zone information of the first UE, or some combination thereof. 
     Aspect 23: The method of any of aspects 17 through 22, further comprising: receiving, from the second UE, a reference signal configuration request message, wherein the sidelink transmission is transmitted based at least in part on the reference signal configuration request message. 
     Aspect 24: The method of aspect 23, further comprising: receiving, as part of the reference signal configuration request message, an indication of a transmit power used by the second UE to transmit the reference signal configuration request message, physical positioning information of the second UE, zone information of the second UE, or some combination thereof determining a proximity of the first UE to the second UE based at least in part on a determined path loss derived from the transmit power, the physical positioning information of the second UE, the zone information of the second UE, or some combination thereof and determining whether the trigger condition is satisfied based at least in part on the proximity. 
     Aspect 25: The method of aspect 24, further comprising: selecting between a narrow beam reference signal configuration and a wide beam reference signal configuration based at least in part on the proximity. 
     Aspect 26: The method of any of aspects 17 through 25, wherein the one or more reference signals comprise a CSI-RS or a PRS. 
     Aspect 27: The method of any of aspects 17 through 26, wherein the sidelink transmission is transmitted as a unicast transmission, a broadcast transmission, or a groupcast transmission. 
     Aspect 28: The method of any of aspects 17 through 27, wherein the first UE is in a connected mode. 
     Aspect 29: An apparatus for wireless communication at a first UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 1 through 16. 
     Aspect 30: An apparatus for wireless communication at a first UE, comprising at least one means for performing a method of any of aspects 1 through 16. 
     Aspect 31: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform a method of any of aspects 1 through 16. 
     Aspect 32: An apparatus for wireless communication at a first UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 17 through 28. 
     Aspect 33: An apparatus for wireless communication at a first UE, comprising at least one means for performing a method of any of aspects 17 through 28. 
     Aspect 34: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform a method of any of aspects 17 through 28. 
     It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. 
     Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein. 
     Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. 
     Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media. 
     As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of”) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.” 
     In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label. 
     The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.