Congestion control for power savings in user equipment for direct link communications

Example implementations include a method, apparatus and computer-readable medium of wireless communication over a sidelink between a first user equipment (UE) and a second UE. The first UE may identify a configuration for discontinuous reception (DRX) for direct link communications with a second UE. The first UE may determine a channel busy ratio (CBR) based on a plurality of CBR measurement occasions within a time window prior to a direct link transmission based on the configuration for DRX. The first UE may determine whether to perform a congestion control on the direct link transmission based on the CBR. The first UE may perform a direct link transmission subject to a channel occupancy ratio limit.

BACKGROUND

Technical Field

The present disclosure relates generally to communication systems, and more particularly, to apparatuses and methods of congestion control for power saving user equipment in direct link communications between two devices.

Introduction

SUMMARY

In an aspect, the disclosure provides a method of wireless communication for a first user equipment (UE). The method may include identifying a configuration for discontinuous reception (DRX) over sidelink communications. The method may include determining a plurality of channel busy ratio (CBR) measurement occasions based on the configuration for DRX. The method may include determining a CBR based on measurements of the plurality of CBR measurement occasions.

The disclosure also provides an apparatus (e.g., a user equipment) including a memory storing computer-executable instructions and at least one processor configured to execute the computer-executable instructions to perform the above method, an apparatus including means for performing the above method, and a computer-readable medium storing computer-executable instructions for performing the above method.

In an aspect, the disclosure provides a method of wireless communication for a first UE. The method may include identifying a configuration of frequency domain resources for sidelink communications. The configuration may include a first frequency domain resource and a second frequency domain resource. The method may include measuring a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of CBR occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active. The method may include determining a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions.

The disclosure also provides an apparatus (e.g., a user equipment) including a memory storing computer-executable instructions and at least one processor configured to execute the computer-executable instructions to perform the above method, an apparatus including means for performing the above method, and a computer-readable medium storing computer-executable instructions for performing the above method.

DETAILED DESCRIPTION

The described features generally relate to congestion control and power saving for direct link communications of device-to-device (D2D) communication technologies. As used herein, a direct link refers to a direct wireless communications path from a first wireless device to a second wireless device. For example, in fifth generation (5G) new radio (NR) communication technologies a direct link between two user equipment (UEs) may be referred to as a sidelink (SL), as opposed to communications over the Uu interface (e.g., from gNB to user equipment (UE). Direct links may be utilized in D2D communication technologies that can include vehicle-to-vehicle (V2V) communications, vehicle-to-infrastructure (V2I) communications (e.g., from a vehicle-based communication device to road infrastructure nodes), vehicle-to-network (V2N) communications (e.g., from a vehicle-based communication device to one or more network nodes, such as a base station), a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. In V2X communications, vehicle-based communication devices can communicate with one another and/or with infrastructure devices over a direct link channel.

One concern with D2D communications is the possibility of congestion if multiple devices are attempting to communicate directly. D2D communications technologies may allow a user equipment (UE) to schedule transmissions subject to congestion control. For example, a channel busy ratio (CBR) may be used as a metric for congestion control. A sidelink or direct link received signal strength indicator (RSSI) may be used for CBR estimation. For example, the CBR may be measured for all subchannels for the direct link transmission over a window prior to the transmission. The UE may then limit a channel occupancy ratio (CR) to be smaller than a configured threshold, based on the measured CBR.

D2D communication technologies intended for use within a vehicle or infrastructure may not be concerned with power consumption due to availability of power from the vehicle or other supply. D2D communication technologies, however, may also be applied to portable devices such as mobile devices that have a limited power supply such as a battery. Accordingly, power saving techniques for D2D communication technologies may desirable.

A UE in communication with another device (e.g., a base station or another UE) may actively monitor a control channel (e.g., a physical downlink control channel (PDCCH) or a physical sidelink control channel (PSCCH)) for a grant scheduling a transmission. When the UE is not actively receiving data, the UE may conserve power by entering a discontinuous reception (DRX) mode in which the UE monitors the control channel during an active time and an on duration of a DRX cycle and may sleep during an off portion of the DRX cycle. That is, the UE may not monitor the control channel during the off portion of the DRX cycle and a base station may avoid transmitting the control channel to the UE during the off portion of the DRX cycle. Another example power saving technique is frequency domain resource adaptation, where the UE may switch to a smaller frequency domain resource to monitor when the UE is not actively transmitting or receiving data.

Power saving techniques have a potential to interfere with congestion control techniques. In particular, because power saving techniques such as DRX and frequency domain resource adaptation limit the resources that the UE monitors, the UE may not be able to measure the RSSI on all resources for a transmission during the window prior to the transmission.

In an aspect, the present disclosure provides techniques for determining a CBR for congestion control when one or more power saving techniques that limit monitored resources are configured. The present disclosure provides for a plurality of CBR measurement occasions that the UE may measure to determine a channel quality metric (e.g., RSSI) for CBR calculations. Some of the CBR measurement occasions may be configured on resources that the UE is not configured to monitor due to the power savings techniques. Accordingly, the UE may be able to determine a CBR for resources on which the UE may perform a direct link transmission. When the UE has data to transmit, the UE may immediately schedule the direct link transmission and determine the CR limits for congestion control without performing additional measurements. Accordingly, the UE may not incur additional latency for performing congestion control when configured with power saving techniques. In an aspect, the RSSI measurement may be less complex than monitoring a control channel and occur less often than constant monitoring without power saving techniques. Accordingly, determining the CBR based on the CBR measurement occasions while still implementing the power savings techniques may also reduce power consumption compared to not using power savings techniques.

In an aspect, one or more of the UEs104may include a sidelink CBR component140that performs congestion control for sidelink communications configured with power savings techniques such as DRX or frequency domain resource adaptation. The sidelink CBR component140may include a configuration component142that identifies a configuration for DRX for direct link communications with a second UE. In an aspect, the configuration component142may identify configuration of a first frequency domain resource and a second frequency domain resource for direct link communications with a second UE. The sidelink CBR component140may include a measurement component144that determines a CBR based on a plurality of CBR measurement occasions within a time window prior to a direct link transmission based on the configuration for DRX. In an aspect, the measurement component144may measure a RSSI on the second frequency domain resource during a plurality of CBR measurement occasions within a time window prior to a direct link transmission on the second frequency domain resource when the second frequency domain resource is not active. The measurement component144may determine a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions. The sidelink CBR component140may include a congestion controller146that determines whether to perform a congestion control on the direct link transmission based on the CBR. The sidelink CBR component140may include a transmission component148that performs a direct link transmission subject to a channel occupancy ratio limit.

In an aspect, one or more of the base stations102may include a sidelink configuration component198that is configured to configure the first UE with the DRX configuration, the frequency domain resource configuration, and/or a CBR occasion configuration.

With the above aspects in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, or may be within the EHF band. Communications using the mmW radio frequency band have extremely high path loss and a short range. The mmW base station180may utilize beamforming182with the UE104to compensate for the path loss and short range.

At least one of the TX processor368, the RX processor356, and the controller/processor359may be configured to perform aspects in connection with the sidelink CBR component140ofFIG.1.

At least one of the TX processor316, the RX processor370, and the controller/processor375may be configured to perform aspects in connection with the sidelink configuration component198ofFIG.1.

FIG.4is a diagram400illustrating an example of DRX operation for a direct link between a first device404(e.g., a UE104) and a second device406(e.g., another UE such as an IoT device). As illustrated, the direct link may provide, for example, unicast communications (i.e., direct communication between UE1and UE2). Direct link communications may also be applied to other cast types (e.g., group cast and broadcast). For instance, in the broadcast case, UE1may transmit to all UEs in a vicinity without knowing the identity of each UE. In the frequency domain, the direct link may be over a resource pool410. In the time domain, a DRX configuration may define a DRX cycle including a DRX on duration422and a DRX off duration424. The DRX configuration may provide for power savings by allowing the UE104to sleep during the DRX off duration. In other words, the UE104may not monitor direct link control or data channels during the DRX off duration424.

In an aspect, a wake-up signal (WUS) operation for a direct link between a first device (e.g., UE104) and a second device may be configured in addition to the DRX operation. A WUS configuration may define a WUS monitoring period430, which may be the same as the DRX cycle420. At the start of the WUS period430, the UE104may monitor the resource pool410for a WUS432. If the WUS432is detected, the UE104may stay awake for the remainder of the DRX on duration422, then sleep during the DRX off duration424as discussed above. If the WUS432is not detected, the UE104may sleep for the remainder of the WUS monitoring period430. That is, the UE104may not enter the DRX on duration422if the WUS432is not detected.

FIG.5is a diagram500illustrating an example of frequency domain resource switching. A “frequency domain resource” may refer to any identification of an allocation of resources in the frequency domain such as a bandwidth part (BWP), resource pool, or component carrier. Frequency domain resource switching may provide power savings by switching the UE to a smaller frequency domain resource based on transmission/reception load. For example, the UE104may be configured with a first frequency domain resource510and a second frequency domain resource512. The second frequency domain resource512may be larger than the first frequency domain resource510. In some implementations, the first frequency domain resource510may be a subset of the second frequency domain resource512. In an aspect, the UE104may be configured with direct link carrier aggregation in which the UE104is configured with a plurality of component carriers. Each component carrier may be configured with one or more frequency domain resources.

The first frequency domain resource510may be active, for example, in a slot520. The UE104may receive a small amount of data522from higher layers and transmit the small amount of data522via the first frequency domain resource510. For example, the small amount of data522may be less than a maximum transport block size for the first frequency domain resource510. If a large amount of data532(e.g., greater than the maximum transport block size for the first frequency domain resource510) arrives from higher layers in a slot530, the UE104may switch to the second frequency domain resource512. After a switching time534, which may be zero or more slots, the UE104may transmit the large amount of data532in one or more slots540over the second frequency domain resource512. If the UE104receives no data or a small amount of data from the higher layers during a time duration550, the UE104may switch to the first frequency domain resource510after a switching time552(e.g., zero or more slots) for use in a subsequent slot560.

FIG.6is a diagram600illustrating another example of frequency domain resource switching by receiving an activation of a second frequency domain resource. In this example, the UE104may be configured with a first frequency domain resource610and a second frequency domain resource612. The UE104may receive a sidelink control information (SCI)620on the first frequency domain resource610that schedules a physical sidelink shared channel (PSSCH)622. The SCI620and/or the PSSCH622may activate the second frequency domain resource612. For example, the PSSCH may include a media access control (MAC) control element (MAC-CE) that activates the second frequency domain resource612. The UE104may then receive a second SCI630that schedules a PSSCH632on the first frequency domain resource610and/or a PSSCH634on the second frequency domain resource612. The second SCI630, the PSSCH632, and/or the PSSCH634may deactivate the second frequency domain resource612. Accordingly, the second frequency domain resource612may be dynamically activated and deactivated as needed. The UE104may save power by not monitoring the deactivated second frequency domain resource612.

In an aspect, with any of a DRX configuration, a WUS configuration, or frequency domain resource switching, a UE may spend a significant amount of time in a sleep mode for at least some resources in order to save power. Direct link communications may include congestion control. For example, a channel busy ratio (CBR) may be used as a metric for congestion control. A UE104may measure the CBR to determine whether the medium is busy, and the UE104may limit resource utilization of the UE104by limiting a channel occupancy ratio (CR) to be smaller than a configured threshold, based on the measured CBR. Conventional definitions of CBR may be based on a received signal strength indicator (RSSI) for all subchannels during a time period of [n−100, n−1] slots prior to a transmission starting at slot n. In an aspect, because the UE104may schedule direct link transmissions as data becomes available, a CBR measurement according to a conventional definition may imply that the UE104is to constantly measure the CBR in order to have a valid CBR measurement at slot n. A UE may not be able to utilize power saving techniques such as DRX and WUS if the UE is constantly measuring RSSI in order to determine CBR. Similarly, for frequency domain power savings, conventional CBR measurement may prevent the UE from switching to a smaller bandwidth frequency domain resource due to monitoring of all frequency domain resources for CBR.

FIG.7is a diagram700of a CBR measurement based on a DRX configuration of a UE104. The UE104may be configured with the DRX cycle420including the DRX on duration422and the DRX off duration424. A plurality of CBR measurement occasions712may be defined based on the DRX cycle420. For example, the CBR may be defined as the channel busy ratio (i.e., SL-RSSI>threshold) measured on CBR measurement occasions712during the DRX on duration422within a measurement window710before a transmission slot720(e.g., slot n). The measurement window710may be the time period of [n−100, n−1] or may be extended. For example, the measurement window710may include a number of slots within the DRX on duration equal to the duration of the time period [n−100, n−1] (i.e., 100 slots). If the UE104is configured to monitor a WUS, the UE104may only measure CBR during the DRX on durations in which the UE is awake. In other words, the CBR may be defined using the slots in which the UE is in an awake state (determined by both the DRX and WUS). In an aspect, this definition of CBR may be more effective when the DRX configuration of multiple UEs are aligned. For example, for two pairs of communicating UEs, the DRX on duration422may either fully overlap or be fully orthogonal. In the case of overlapping DRX on durations, the CBR measurement within the DRX on duration may accurately indicate congestion that may be experienced during a transmission. In the case of orthogonal DRX on durations, although the CBR measurement may not include transmissions of the other pair of UEs, such transmissions may not contribute to congestion during the DRX on duration.

FIG.8is a diagram800of a CBR measurement over a plurality of CBR measurement occasions810. The UE104may be configured with the DRX cycle420including the DRX on duration422and the DRX off duration424. The UE104may be configured with a plurality of CBR measurement occasions810. The configuration of the CBR measurement occasions810may be received from a base station or another UE. In some implementations, the CBR measurement occasions810may be configured by the UE104to meet a minimum monitoring requirement. For example, the UE104may determine a configuration of CBR measurement occasions810that guarantees that at least a minimum number of slots are measured within a time window820of a given length (e.g., 100 ms/slots). The minimum number may be expressed as a percentage (e.g., X %). For example, for any slot n, the UE104may be configured to measure at least X slots between [n−100, n−1]. Accordingly, when the UE104determines to perform a transmission830, the UE104may satisfy a CBR measurement requirement. In an aspect, the UE104may independently select the slots for the configuration of CBR measurement occasions810that meet the X % requirement. Because each UE selects the CBR measurement occasions810independently (e.g., randomly), the probability that the UE104is able to measure the activity of another UE may be maximized. Thus, the CBR calculation based on the measurements may be more accurate than preconfigured CBR measurement occasions. In contrast, if all UEs use the same CBR measurement occasions, then all of the UEs may effectively “receive” during these slots, and none of the UEs may be transmitting. Therefore, one or more UEs may erroneously determine that the medium is free or uncongested.

In an aspect, the CBR measurement occasions810can be periodic (e.g., every Y slots). If the periodic measurements correspond to periodic transmissions, the periodic CBR measurement occasions may provide an accurate measurement of congestion that may be experienced during a periodic transmission. In another aspect, the CBR measurement occasions810may follow a pseudo-random pattern. Pseudo-random selection of the CBR measurement occasions810may avoid measuring or missing a periodic transmission. As such, pseudo-random selection of the CBR measurement occasions810may provide a more accurate CBR for arbitrary transmissions.

As illustrated, some of the CBR measurement occasions810may occur outside of the DRX on duration422(i.e., during the DRX off duration424). For these CBR measurement occasions810, the UE104may wake up to measure RSSI. In an aspect, an RSSI measurement may consume less power than a full reception and decoding procedure for monitoring a control channel.

The CBR measurement occasions810may be spread out over a longer period of time than conventional CBR measurements. More recent CBR measurements may more accurately reflect congestion at the time of a transmission. In an aspect, instead of determining a mean CBR measurement over the window820, the CBR value may be determined by filtering a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value. For example, in some implementations, the filter may be expressed by the equation:
CBR(n)=α*CBR(n−1)+(1−α)*CBRins(n−1)  (1)

where CBR(n) is the CBR value at slot n, CBR_ins(n−1) is the instantaneous CBR measured on slot n−1, and a is a filter coefficient with a value between 0 and 1. If the UE performs a channel measurement during slot n−1, CBR_ins(n−1) is given by the ratio of subchannels in slot n−1 where the SL-RSSI is greater than a configured threshold. Otherwise, if the UE does not perform channel measurement during slot n−1, CBR_ins(n−1) is equal to CBR(n−1). Therefore CBR(n) is equal to CBR(n−1) when no measurement is performed in slot n−1. The use of a filter to determine the CBR for a slot may allow the UE104to increase the number of measurements used in the CBR calculation compared to an average over a fixed time window. If the window is kept fixed (e.g., 100 slots), but the UE104only measures X % of the slots, then the CBR may be determined based on measurement of only X slots. In contrast, the filter based approach allows the UE104to use more measurement information, and also emphasizes the most recent measurements.

FIG.9is a diagram900illustrating an example of CBR measurements with frequency domain resource switching. For example, the UE104may be configured with a first frequency domain resource910(e.g., BWP1or resource pool1) and a second frequency domain resource912(e.g. BWP2or resource pool2). The second bandwidth resource912may be larger than the first frequency domain resource910. In some implementations, the first frequency domain resource910may be a subset of the second frequency domain resource912. The UE104may be configured with CBR measurement occasions920outside of the active frequency domain resource for the UE to measure CBR. For example, when the first frequency domain resource910is active, the UE104may measure RSSI on the second frequency domain resource912on the CBR measurement occasions920during a time window922. That is, the UE104may receive a signal over the second frequency domain resource912and determine the RSSI. When the UE104has a large amount of data to transmit or the UE104receives a switching signal from another UE, the UE104may switch to the second frequency domain resource912. The UE104may transmit a transmission932on the second frequency domain resource912after a switching time930. The UE104may also measure RSSI on the second frequency domain resource912when the second frequency domain resource912is active. In an aspect, a switching time for measuring RSSI during CBR measurement occasions920may be less than the switching time930due to the simplicity of RSSI measurement. The switching time for measuring RSSI during CBR measurement occasions920may be planned based on the configuration of the CBR measurement occasions920and may occur when the first frequency domain resource910is active.

Similar to the DRX case, the CBR measurement occasions920may be configured by a base station (e.g., gNB), by another UE (e.g., a host device or a relay), or by the UE104itself. The CBR measurement occasions920may be configured to meet a minimum monitoring requirement. For example, the UE104may determine a configuration of CBR measurement occasions920that guarantees that at least the minimum number of slots are measured within a time window820of a given length (e.g., 100 ms/slots). For example, for any slot n, the UE104may be configured to measure at least X slots between [n−100, n−1]. Accordingly, when the UE104determines to perform a transmission932on the second frequency domain resource912, the UE104may satisfy a CBR measurement requirement.

In an aspect, the CBR measurement occasions920can be periodic (e.g., every Y slots). If the periodic measurements correspond to periodic transmissions, the periodic CBR measurement occasions may provide an accurate measurement of congestion that may be experienced during a periodic transmission. In another aspect, the CBR measurement occasions920may follow a pseudo-random pattern. Pseudo-random selection of the CBR measurement occasions920may avoid measuring or missing a periodic transmission. As such, pseudo-random selection of the CBR measurement occasions920may provide a more accurate CBR for arbitrary transmissions.

The filter-based calculation of the CBR value described above may also be used with the CBR measurement occasions920. Similar the CBR measurement occasions810, the CBR measurement occasions920may be spread out over a longer period of time than a fixed window. The use of a filter to determine the CBR for a slot may allow the UE104to increase the number of measurements used in the CBR calculation compared to an average over the fixed time window. If the window is kept fixed (e.g., 100 slots), but the UE104only measures X % of the slots during CBR measurement occasions920, then the CBR may be determined based on measurement of only X slots. In contrast, the filter based approach allows the UE104to use more measurement information, and also emphasizes the most recent measurements.

FIG.10is a diagram illustrating resource switching based on CBR measurements. In an aspect, a UE104may be configured with multiple frequency domain resources (e.g., first frequency domain resource1010, second frequency domain resource1012, and third frequency domain resource1014). The UE104may be configured with CBR measurement occasions for each inactive frequency domain resource as discussed above regardingFIG.9. The UE104may select a new frequency domain resource to activate based on the CBR measurement for an inactive frequency domain resource. For example, the UE104may select the new frequency domain resource to activate if the measured CBR value for the new frequency domain resource is less than a threshold. Conversely, the UE104may deactivate an active frequency domain resource if the measured CBR value for the active frequency domain resource is greater than a second threshold. In an aspect, the UE104may transmit an activation signal1020or an activation/deactivation signal1022when switching frequency domain resources. The activation signal1020or an activation/deactivation signal1022may inform another UE which frequency domain resource to use for subsequent transmissions.

The UE104may maintain at least one active frequency domain resource. For example, the UE104may be configured with a primary frequency domain resource (e.g., the first frequency domain resource1010) that remains active while other frequency domain resources (e.g., the second frequency domain resource1012and the third frequency domain resource1014) are dynamically activated or deactivated. In another implementation, the UE104may switch from an active frequency domain resource (e.g., the second frequency domain resource1012) to an inactive frequency domain resource (e.g., the third frequency domain resource1014) by deactivating the active frequency domain resource and activating the inactive frequency domain resource during a switching time1030.

FIG.11is a diagram1100illustrating example communications and components of a base station102, a first UE104-a, and a second UE104-b. The UEs104-aand104-bmay each include a sidelink CBR component140. The first UE104-amay be a sidelink transmitting UE and the second UE104-bmay be a sidelink receiving UE. As discussed above regardingFIG.1, the first UE104-amay include the configuration component142, the measurement component144, the congestion controller146, and the transmission component148. The UE104may also include a receiver component1110and a transmitter component1112. The receiver component1110may include, for example, a RF receiver for receiving the signals described herein. The transmitter component1112may include, for example, an RF transmitter for transmitting the signals described herein. In an aspect, the receiver component1110and the transmitter component1112may be implemented as a transceiver.

The base station102may include the sidelink configuration component198. The base station102may transmit a SL configuration1120to the first UE104-aand transmit a sidelink configuration1122to the second UE104-b. For example, the sidelink configurations1120,1122may be radio resource control (RRC) messages, media access control (MAC) control elements (CE), or downlink control information (DCI) carried on a PDCCH. The configuration component142at each of the first UE104-aand the second UE104-bmay receive the respective sidelink configuration1120,1122.

The first UE104-aand the second UE104-bmay communicate via the communication link158, which may be referred to as a direct link or the sidelink. In an aspect, the first UE104-amay monitor the communication link158by performing CBR measurements1132to determine a CBR value. The first UE104-amay optionally transmit a switching signal1134indicating a change in frequency domain resources or receive the switching signal1134indicating that the second UE104-bhas changed the frequency domain resources. The first UE104-amay perform congestion control1136by limiting the CR (channel occupancy ratio) of a transmission1138to be smaller than a configured threshold, based on the measured CBR value. In an aspect, the SL configuration1120may include a power saving configuration such as a DRX configuration, a WUS configuration, or a frequency domain resource configuration including multiple frequency domain resources (e.g., bandwidth parts or resource pools).

The configuration component142of the first UE104-amay identify a configuration for direct link communications. For example, the first UE104-amay receive the SL configuration1120from the base station102. In another aspect, the first UE104-amay identify a configuration (e.g., a default configuration) based on a standards document or regulation. In another aspect, the first UE104-amay receive a sidelink configuration from another UE (e.g., UE104-b), which may forward the sidelink configuration from a base station. In an aspect, the configuration component142may identify a configuration for DRX (e.g., DRX configuration1140) for direct link communications with the second UE104-b. For example, the DRX configuration1140may define the DRX cycle420, DRX on duration422, and/or DRX off duration424. The DRX configuration1140may also include a WUS monitoring period430. In an aspect, the configuration component142may identify a frequency domain resource configuration1142. The frequency domain resource configuration1142may include a configuration of a first frequency domain resource and a second frequency domain resource for direct link communications with the second UE104-b. For example, the configuration may define a first frequency domain resource510,610,910, or1010and a second frequency domain resource512,612,912, or1012. The frequency domain resource configuration1142may also define a third frequency domain resource1014. The frequency domain resource configuration1142may indicate whether each configured frequency domain resource is activated or deactivated.

The configuration component142may also identify a CBR occasion configuration1130. For example, the CBR occasion configuration1130may be received within the SL configuration1120or in other signaling from the base station102. As another example, the configuration component142may receive the CBR occasion configuration1130from another UE such as the second UE104-b. As another example, the UE104-aand/or the configuration component142may determine the CBR occasion configuration1130according to rules defined in a standards document or regulation. In an aspect, some parameters of the rule (e.g., a value of X) may be signaled by the base station102and/or the second UE104-b. The CBR occasion configuration1130may define the CBR measurement occasions810or920.

The measurement component144may perform the CBR measurements1132based on the CBR occasion configuration1130. In particular, the measurement component144may measure an RSSI during the CBR measurement occasions810or920. The measurement component144may perform the CBR measurements on time domain resources and/or frequency domain resources where the UE104-ais not configured to receive a transmission. For example, the measurement component144may perform CBR measurements on CBR measurement occasions810during a DRX off duration424or perform CBR measurements on CBR measurement occasions920on an inactive frequency domain resource.

The congestion controller146may determine whether to perform a congestion control on the direct link transmission1138based on the CBR. For example, the congestion controller146may determine a CR limit1160based on the CBR. The congestion controller146may limit parameters of the transmission1138to ensure that a CR of the transmission1138is less than the CR limit1160. For instance, the CR limit1160may be defined as a fraction of sub-channels used for transmission in [n−a, n−1] and granted/reserved in [n, n+b], where a is positive and b is a non-negative integer; a+b+1=1000; and a>=500. The value n+b should not exceed the last transmission opportunity of the grant for the transmission1138. For example, the congestion controller146may limit one or more of modulation and coding scheme (MCS) tables or indices, a number of sub-channels, a number of retransmissions, or a transmission power in order to satisfy the CR limit1160.

The transmission component148may transmit the transmission1138based on the congestion control determined by the congestion controller146. For instance, the transmission component148may select the MCS, the number of sub-channels, the number of retransmissions, and the transmission power based on the congestion control. The transmission component148may transmit the transmission1138via the transmitter component1112.

FIG.12is a conceptual data flow diagram1200illustrating the data flow between different means/components in an example UE1204, which may be an example of the UE104including the sidelink CBR component140.

The receiver component1110may receive downlink signals such as the SL configuration1120and/or the CBR occasion configuration1130. The receiver component1110may pass configuration messages to the configuration component142. The receiver component1110may receive sidelink signals such as PSCCH, PSSCH, and PSFCH, which may be intended for the UE1204or another UE. The receiver component1110may pass the sidelink signals to the measurement component144.

The configuration component142may receive the SL configuration1120and/or the CBR occasion configuration1130from the receiver component1110. The configuration component142may decode a received configuration and provide configuration information (e.g., CBR measurement occasions) to the measurement component144.

The measurement component144may receive the CBR measurement occasions from the configuration component142. The measurement component144may receive the sidelink signals from the receiver component1110. The measurement component may perform an RSSI measurement on the sidelink signals during the CBR measurement occasions. The measurement component144may further determine a CBR value based on the RSSI measurements. For example, the measurement component144may determine an average number of sub-channels occupied during a measurement window710. As another example, the measurement component144may determine a weighted CBR by filtering a plurality of CBR measurements based on a filter coefficient (a) applied to a previous CBR value.

The congestion controller146may receive the CBR value from the measurement component144and determine a CR limit1160. The CR limit1160may limit values for one or more of a MCS table or indices, a number of sub-channels, a number of retransmissions, or a transmission power. The congestion controller146may provide the CR limit1160to the transmission component148.

The transmission component148may determine transmission parameters based on the CR limit1160, an amount of data, and channel conditions. For example, the transmission component148may select an MCS, a number of sub-channels, a number of retransmissions, and a transmission power that satisfies the CR limit1160. The transmission component148. The transmission component148may provide the sidelink signals for transmission and the transmission parameters to the transmitter component1112for transmission.

FIG.13is a flowchart of an example method1300for operating a UE104(e.g., the first UE104-a) for sidelink transmission according to a DRX configuration with congestion control. The method1300may be performed by a UE (such as the UE104, which may include the memory360and which may be the entire UE104or a component of the UE104such as the sidelink CBR component140, the TX processor368, the RX processor356, or the controller/processor359). The method1300may be performed by the sidelink CBR component140in communication with the sidelink configuration component198of the base station102and the sidelink CBR component140of another UE104.

At block1310, the method1300may include identifying a configuration for DRX over sidelink communications. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140, the receiver component1110, and/or the configuration component142to identify the configuration for DRX (e.g., DRX configuration1140) for sidelink communications. For example, the sidelink communications may include direct communications with at least a second UE104-b. The sidelink communications may include groupcast communications with a group of UEs or broadcast communications where one or more receiving UEs are unknown. In an aspect, the receiver component1110and/or the configuration component142may receive the DRX configuration1140from the base station102(e.g., within SL configuration1120). In another aspect, the DRX configuration1140may be a default configuration defined by a standards document or regulation. Accordingly, the UE104, the RX processor356, and/or the controller/processor359executing the sidelink CBR component140, the receiver component1110, and/or the configuration component142may provide means for identifying a configuration for DRX over sidelink communications.

At block1320, the method1300may include determining a plurality of CBR measurement occasions based on the configuration for DRX. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the configuration component142to determine a plurality of CBR measurement occasions810based on the configuration for DRX. For example, at sub-block1322, the configuration component142may determine the plurality of CBR measurement occasions that occur during an on duration of the configuration for DRX. That is, the configuration component142may select CBR measurement occasions810that occur during the DRX on duration422. Additionally, when the UE104is configured with WUS, the configuration component142may select CBR measurement occasions810that occur when the UE104is awake. As another example, at sub-block1324, the configuration component142may determine at least one CBR measurement occasion outside of an on duration of the configuration for DRX. For example, the configuration component142may select at least one CBR measurement occasion810during the DRX off duration424. Accordingly, the UE104, the RX processor356, and/or the controller/processor359executing the sidelink CBR component140and/or the configuration component142may provide means for determining a plurality of CBR measurement occasions based on the configuration for DRX.

At block1330, the method1300may include determining a CBR based on measurements of the plurality of CBR measurement occasions. In an aspect, for example, the UE104, the RX processor356and/or the controller/processor359may execute the sidelink CBR component140and/or the measurement component144to determine the CBR based on measurements (e.g., CBR measurements1132) of the plurality of CBR measurement occasions810. For example, the measurement component144may measure the plurality of CBR measurement occasions810within a time window820prior to a sidelink transmission830based on the configuration for DRX. CBR measurement occasions. For example, the measurement component144may measure received signals during each of the CBR measurement occasions810to determine an RSSI for each CBR occasion. In an aspect, the plurality of CBR measurement occasions is periodic. In another aspect, the plurality of CBR measurement occasions is pseudo-random. The plurality of CBR measurement occasions may be configured by the first UE to include at least a minimum number of slots within the time window (e.g., time window710or820). In an aspect, the UE104may be configured with sidelink carrier aggregation for a plurality of component carriers. The CBR measurement occasions712or810may be configured separately for each component carrier of the plurality of component carriers. Alternatively, the CBR measurement occasions may be configured jointly for the plurality of component carriers.

In an aspect, in sub-block1332, the block1330may include waking up to measure a RSSI during the at least one CBR measurement occasion outside of the on duration of the configuration for DRX. For example, the sub-block1332may be performed in response to the sub-block1324. For example, the measurement component144may wake up the receiver component1110to measure the sidelink signals on a CBR measurement occasion810that occurs during a DRX off duration424. In an aspect, in sub-block1334, the block1330may include filtering a plurality of CBR measurements based on a filter coefficient (a) applied to a previous CBR value. For example, the measurement component144may filter the plurality of CBR measurements according to equation (1) above. In another aspect, where the UE104is configured with sidelink carrier aggregation, at sub-block1336, the block1330may include determining the CBR based on only activated component carriers. Alternatively, in sub-block1338, the block1330may include measuring RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions810. In view of the foregoing, the UE104, the RX processor356, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the measurement component144may provide means for determining a CBR based on measurements of the plurality of CBR measurement occasions.

At block1340, the method1300may optionally include determining whether to perform a congestion control on the sidelink transmission based on the CBR. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the congestion controller146to determine whether to perform a congestion control on the sidelink transmission1138based on the CBR1150. Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the congestion controller146may provide means for determining whether to perform a congestion control on the sidelink transmission based on the CBR.

At block1350, the method1300may optionally include performing a sidelink transmission subject to a channel occupancy ratio limit. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the transmission component148to perform the sidelink transmission1138subject to a channel occupancy ratio limit (e.g., CR limit1160). The CR limit1160may provide congestion control by limiting the resources used by the first UE104-a. Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the transmission component148may provide means for performing a sidelink transmission subject to a channel occupancy ratio limit.

FIG.14is a flowchart of an example method1400for operating a UE104(e.g., the first UE104-a) for sidelink transmission with congestion control according to a frequency domain configuration with multiple frequency domain resources. The method1400may be performed by a UE (such as the UE104, which may include the memory360and which may be the entire UE104or a component of the UE104such as the sidelink CBR component140, the TX processor368, the RX processor356, or the controller/processor359). The method1300may be performed by the sidelink CBR component140in communication with the sidelink configuration component198of the base station102and the sidelink CBR component140of another UE104.

At block1410, the method1400may include identifying a configuration of frequency domain resources for sidelink communications, the configuration including a first frequency domain resource and a second frequency domain resource. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the configuration component142to identifying the configuration of frequency domain resources (e.g., frequency domain resource configuration1142) for sidelink communications. For example, the sidelink communications may include unicast, groupcast, or broadcast communications with at least a second UE104-b. The frequency domain resource configuration1142may include a first frequency domain resource910or1010and a second frequency domain resource912or1012. For example, the configuration component142may receive the frequency domain resource configuration1142from the base station102(e.g., within SL configuration1120). Accordingly, the UE104, the RX processor356, and/or the controller/processor359executing the sidelink CBR component140and/or the configuration component142may provide means for identifying a configuration of frequency domain resources for sidelink communications with a second UE.

At block1420, the method1400may include measuring a RSSI on the second frequency domain resource during a plurality of CBR measurement occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active. In an aspect, for example, the UE104, the RX processor356and/or the controller/processor359may execute the sidelink CBR component140and/or the measurement component144to measure the RSSI1152on the second frequency domain resource912or1012during a plurality of CBR measurement occasions920within a time window922prior to a sidelink transmission932on the second frequency domain resource912when the second frequency domain resource is not active. For example, the measurement component144may measure received signals during each of the CBR measurement occasions to determine an RSSI1152for each CBR occasion. In an aspect, the plurality of CBR measurement occasions is periodic. In another aspect, the plurality of CBR measurement occasions is pseudo-random. The plurality of CBR measurement occasions may be configured by the first UE to include at least a minimum number of slots within the time window (e.g., time window922). In an aspect, the UE104may be configured with direct link carrier aggregation for a plurality of component carriers. The CBR measurement occasions712or810may be configured separately for each component carrier of the plurality of component carriers. Alternatively, the CBR measurement occasions may be configured jointly for the plurality of component carriers.

In view of the foregoing, the UE104, the RX processor356, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the measurement component144may provide means for measuring a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of CBR measurement occasions within a time window prior to a direct link transmission on the second frequency domain resource when the second frequency domain resource is not active.

At block1430, the method1400may include determining a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions. In an aspect, for example, the UE104, the RX processor356and/or the controller/processor359may execute the sidelink CBR component140and/or the measurement component144to determine the CBR1150for the second frequency domain resource based on the RSSI1152for the plurality of CBR measurement occasions. In an aspect, at sub-block1432, the block1430may include filtering a plurality of CBR measurements based on a filter coefficient (a) applied to a previous CBR value. For example, the measurement component144may filter the plurality of CBR measurements according to equation (1) above. In an aspect, where the UE104is configured with sidelink carrier aggregation, at sub-block1434, the block1430may include determining the CBR based on only activated component carriers. Alternatively, in sub-block1436, the block1430may include measuring RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions. In view of the foregoing, the UE104, the RX processor356, the Tx processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the measurement component144may provide means for measuring a RSSI on the second frequency domain resource during a plurality of CBR measurement occasions within a time window prior to a direct link transmission on the second frequency domain resource when the second frequency domain resource is not active.

At block1440, the method1400may optionally include activating the second frequency domain resource in response to the CBR satisfying a threshold. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the congestion controller146to activate the second frequency domain resource912,1012in response to the CBR satisfying a threshold. For example, the congestion controller146may determine to activate the second frequency domain resource912,1012in response to the measured CBR1150being less than the first threshold. The first threshold may be configured via the frequency domain resource configuration1142. Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the congestion controller146may provide means for activating the second frequency domain resource in response to the CBR satisfying a threshold.

At block1450, the method1400may optionally include deactivating the second frequency domain resource in response to the CBR being greater than a second threshold. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the congestion controller146to deactivate the second frequency domain resource912,1012in response to the CBR1150being greater than a second threshold. The second threshold may be configured via the frequency domain resource configuration1142. In an aspect, the congestion controller146may switch from the second frequency domain resource1012to a third frequency domain resource1014when deactivating the second frequency domain resource1012. Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the congestion controller146may provide means for activating the second frequency domain resource in response to the CBR satisfying a threshold.

At block1460, the method1400may optionally include determining whether to perform a congestion control on the direct link transmission based on the CBR. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the congestion controller146to determine whether to perform a congestion control on the direct link transmission1138based on the CBR1150. Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the congestion controller146may provide means for determining whether to perform a congestion control on the direct link transmission based on the CBR.

At block1470, the method1400may optionally include performing a direct link transmission subject to a channel occupancy ratio limit. In an aspect, for example, the UE104, the TX processor368and/or the controller/processor359may execute the sidelink CBR component140and/or the transmission component148to perform the direct link transmission1138subject to a channel occupancy ratio limit (e.g., CR limit1160). Accordingly, the UE104, the TX processor368, and/or the controller/processor359executing the sidelink CBR component140and/or the transmission component148may provide means for performing a direct link transmission subject to a channel occupancy ratio limit.

Some Further Example Clauses

1. A method of wireless communication, comprising, at a first user equipment (UE):identifying a configuration for discontinuous reception (DRX) over sidelink communications;determining a plurality of channel busy ratio (CBR) measurement occasions based on the configuration for DRX; anddetermining a CBR based on measurements of the plurality of CBR measurement occasions.

2. The method of clause 1, wherein determining the plurality of CBR measurement occasions comprises determining the plurality of CBR measurement occasions that occur during an on duration of the configuration for DRX.

3. The method of clause 1, wherein determining the plurality of CBR measurement occasions comprises determining at least one CBR measurement occasion outside of an on duration of the configuration for DRX, and wherein determining the CBR based on measurements of the plurality of CBR measurement occasions comprises waking up to measure a received signal strength indicator (RSSI) during the at least one CBR measurement occasion outside of the on duration of the configuration for DRX.

4. The method of any of clauses 1-3, wherein the plurality of CBR measurement occasions is periodic.

5. The method of any of clauses 1-3, wherein the plurality of CBR measurement occasions is pseudo-random.

6. The method of any of clauses 1-5, wherein determining the CBR comprises filtering a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

7. The method of any of clauses 1-6, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured separately for each component carrier of the plurality of component carriers.

8. The method of any of clauses 1-6, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured jointly for the plurality of component carriers.

9. The method of any of clauses 1-8, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein determining the CBR comprises determining the CBR based on only activated component carriers.

10. The method of any of clauses 1-8, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein determining the CBR comprises measuring a RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

11. The method of any of clauses 1-10, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within a time window prior to a sidelink transmission.

12. The method of any of clauses 1-11, further comprising determining whether to perform a congestion control on a sidelink transmission based on the CBR.

13. An apparatus for wireless communication for a first user equipment (UE), comprising:a memory storing computer-executable instructions; andat least one processor coupled to the memory and configured to execute the computer-executable instructions to:identify a configuration for discontinuous reception (DRX) over sidelink communications;determine a plurality of channel busy ratio (CBR) measurement occasions based on the configuration for DRX; anddetermine a CBR based on measurements of the plurality of CBR measurement occasions.

14. The apparatus of clause 13, wherein the at least one processor is configured to determine the plurality of CBR measurement occasions to occur during an on duration of the configuration for DRX.

15. The apparatus of clause 13, wherein the at least one processor is configured to:determine at least one CBR measurement occasion outside of an on duration of the configuration for DRX; andwakeup to measure a received signal strength indicator (RSSI) during the at least one CBR measurement occasion outside of the on duration of the configuration for DRX.

16. The apparatus of any of clauses 13-15, wherein the plurality of CBR measurement occasions is periodic.

17. The apparatus of any of clauses 13-15, wherein the plurality of CBR measurement occasions is pseudo-random.

18. The apparatus of any of clauses 13-17, wherein the at least one processor is configured to filter a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

19. The apparatus of any of clauses 13-18, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured separately for each component carrier of the plurality of component carriers.

20. The apparatus of any of clauses 13-18, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured jointly for the plurality of component carriers.

21. The apparatus of any of clauses 13-20, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein the at least one processor is configured to determine the CBR based on only activated component carriers.

22. The apparatus of any of clauses 13-20, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the at least one processor is configured to determine measure a RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

23. The apparatus of any of clauses 13-22, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within a time window prior to a sidelink transmission.

24. The apparatus of any of clauses 13-23, wherein the at least one processor is configured to determine whether to perform a congestion control on a sidelink transmission based on the CBR.

25. An apparatus for wireless communication for a first user equipment (UE), comprising:means for identifying a configuration for discontinuous reception (DRX) over sidelink communications;means for determining a plurality of channel busy ratio (CBR) measurement occasions based on the configuration for DRX; andmeans for determining a CBR based on measurements of the plurality of CBR measurement occasions.

26. The apparatus of clause 25, wherein the means for determining the plurality of CBR measurement occasions is configured to determine the plurality of CBR measurement occasions that occur during an on duration of the configuration for DRX.

27. The apparatus of clause 25, wherein the means for determining the plurality of CBR measurement occasions is configured to determine at least one CBR measurement occasion outside of an on duration of the configuration for DRX, and wherein the means for determining the CBR based on measurements of the plurality of CBR measurement occasions is configured to wake up to measure a received signal strength indicator (RSSI) during the at least one CBR measurement occasion outside of the on duration of the configuration for DRX.

28. The apparatus of any of clauses 25-27, wherein the plurality of CBR measurement occasions is periodic.

29. The apparatus of any of clauses 25-27, wherein the plurality of CBR measurement occasions is pseudo-random.

30. The apparatus of any of clauses 25-29, wherein the means for determining the CBR is configured to filter a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

31. The apparatus of any of clauses 25-30, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured separately for each component carrier of the plurality of component carriers.

32. The apparatus of any of clauses 25-30, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured jointly for the plurality of component carriers.

33. The apparatus of any of clauses 25-32, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein the means for determining the CBR is configured to determine the CBR based on only activated component carriers.

34. The apparatus of any of clauses 25-32, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the means for determining the CBR is configured to measure a RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

35. The apparatus of any of clauses 25-34, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within a time window prior to a sidelink transmission.

36. The apparatus of any of clauses 25-35, further comprising means for determining whether to perform a congestion control on a sidelink transmission based on the CBR.

37. A non-transitory computer-readable medium storing computer-executable code that when executed by at least one processor causes the at least one processor to, at a first user equipment (UE):identify a configuration for discontinuous reception (DRX) over sidelink communications;determine a plurality of channel busy ratio (CBR) measurement occasions based on the configuration for DRX; anddetermine a CBR based on measurements of the plurality of CBR measurement occasions.

38. The non-transitory computer-readable medium of clause 37, wherein the code to determine the plurality of CBR measurement occasions comprises code to determine the plurality of CBR measurement occasions that occur during an on duration of the configuration for DRX.

39. The non-transitory computer-readable medium of clause 37, wherein the code to determine the plurality of CBR measurement occasions comprises code to determine at least one CBR measurement occasion outside of an on duration of the configuration for DRX, and wherein determining the CBR based on measurements of the plurality of CBR measurement occasions comprises waking up to measure a received signal strength indicator (RSSI) during the at least one CBR measurement occasion outside of the on duration of the configuration for DRX.

40. The non-transitory computer-readable medium of any of clauses 37-39, wherein the plurality of CBR measurement occasions is periodic.

41. The non-transitory computer-readable medium of any of clauses 37-39, wherein the plurality of CBR measurement occasions is pseudo-random.

42. The non-transitory computer-readable medium of any of clauses 37-41, wherein the code to determine the CBR comprises code to filter a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

43. The non-transitory computer-readable medium of any of clauses 37-42, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured separately for each component carrier of the plurality of component carriers.

44. The non-transitory computer-readable medium of any of clauses 37-42, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and the plurality of CBR measurement occasions is configured jointly for the plurality of component carriers.

45. The non-transitory computer-readable medium of any of clauses 37-44, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein the code to determine the CBR comprises code to determine the CBR based on only activated component carriers.

46. The non-transitory computer-readable medium of any of clauses 37-44, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the code to determine the CBR comprises code to measure a RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

47. The non-transitory computer-readable medium of any of clauses 37-46, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within a time window prior to a sidelink transmission.

48. The non-transitory computer-readable medium of any of clauses 37-47, further comprising code to determine whether to perform a congestion control on a sidelink transmission based on the CBR.

49. A method of wireless communication, comprising, at a first user equipment (UE):identifying a configuration of frequency domain resources for sidelink communications, the configuration including a first frequency domain resource and a second frequency domain resource;measuring a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of channel busy ratio (CBR) occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active; anddetermining a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions.

50. The method of clause 49, further comprising determining to activate the second frequency domain resource in response to the CBR satisfying a first threshold.

51. The method of clause 50, further comprising determining to deactivate the second frequency domain resource in response to the CBR being greater than a second threshold.

52. The method of any of clauses 49-51, wherein the plurality of CBR measurement occasions is periodic.

53. The method of any of clauses 49-51, wherein the plurality of CBR measurement occasions is pseudo-random.

54. The method of any of clauses 49-53, wherein determining the CBR comprises filtering a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

55. The method of any of clauses 49-54, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within the time window.

56. The method of any of clauses 49-55, further comprising determining whether to perform a congestion control on the sidelink transmission based on the CBR.

57. The method of any of clauses 49-56, wherein the first frequency domain resource is a first component carrier, a first bandwidth part, or a first resource pool and the second frequency domain resource is a second component carrier, a second bandwidth part, or a second resource pool.

58. The method of any of clauses 49-57, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein determining the CBR comprises determining the CBR based on only activated component carriers.

59. The method of any of clauses 49-57, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein determining the CBR comprises measuring the RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

60. An apparatus for wireless communication for a first user equipment (UE), comprising:a memory storing computer-executable instructions; andat least one processor coupled to the memory and configured to execute the computer-executable instructions to:identify a configuration of frequency domain resources for sidelink communications, the configuration including a first frequency domain resource and a second frequency domain resource;measure a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of channel busy ratio (CBR) occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active; anddetermine a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions.

61. The apparatus of clause 60, wherein the at least one processor is configured to activate the second frequency domain resource in response to the CBR satisfying a first threshold.

62. The apparatus of clause 61, wherein the at least one processor is configured to deactivate the second frequency domain resource in response to the CBR being greater than a second threshold.

63. The apparatus of any of clauses 60-62, wherein the plurality of CBR measurement occasions is periodic.

64. The apparatus of any of clauses 60-62, wherein the plurality of CBR measurement occasions is pseudo-random.

65. The apparatus of any of clauses 60-64, wherein the at least one processor is configured to filter a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

66. The apparatus of any of clauses 60-65, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within the time window.

67. The apparatus of any of clauses 60-66, wherein the at least one processor is configured to determine whether to perform a congestion control on the sidelink transmission based on the CBR.

68. The apparatus of any of clauses 60-67, wherein the first frequency domain resource is a first component carrier, a first bandwidth part, or a first resource pool and the second frequency domain resource is a second component carrier, a second bandwidth part, or a second resource pool.

69. The apparatus of any of clauses 60-68, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the at least one processor is configured to determine the CBR based on only activated component carriers.

70. The apparatus of any of clauses 60-68, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the at least one processor is configured to measure the RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

71. An apparatus for wireless communication for a first user equipment (UE), comprising:means for identifying a configuration of frequency domain resources for sidelink communications, the configuration including a first frequency domain resource and a second frequency domain resource;means for measuring a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of channel busy ratio (CBR) occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active; andmeans for determining a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions.

72. The apparatus of clause 71, further comprising means for activating the second frequency domain resource in response to the CBR satisfying a first threshold.

73. The apparatus of clause 72, wherein the means for activating is configured to deactivate the second frequency domain resource in response to the CBR being greater than a second threshold.

74. The apparatus of any of clauses 71-73, wherein the plurality of CBR measurement occasions is periodic.

75. The apparatus of any of clauses 71-73, wherein the plurality of CBR measurement occasions is pseudo-random.

76. The apparatus of any of clauses 71-75, wherein the means for determining the CBR is configured to filter a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

77. The apparatus of any of clauses 71-77, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within the time window.

78. The apparatus of any of clauses 71-78, further comprising means for determining whether to perform a congestion control on the sidelink transmission based on the CBR.

79. The apparatus of any of clauses 71-79, wherein the first frequency domain resource is a first component carrier, a first bandwidth part, or a first resource pool and the second frequency domain resource is a second component carrier, a second bandwidth part, or a second resource pool.

80. The apparatus of any of clauses 71-80, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein the means for determining the CBR is configured to determine the CBR based on only activated component carriers.

81. The apparatus of any of clauses 71-80, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein the means for determining the CBR is configured to measure the RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.

82. A non-transitory computer-readable medium storing computer-executable code that when executed by at least one processor of a first user equipment (UE) causes the at least one processor to:identify a configuration of frequency domain resources for sidelink communications, the configuration including a first frequency domain resource and a second frequency domain resource;measure a received signal strength indicator (RSSI) on the second frequency domain resource during a plurality of channel busy ratio (CBR) occasions within a time window prior to a sidelink transmission on the second frequency domain resource when the second frequency domain resource is not active; anddetermine a CBR for the second frequency domain resource based on the RSSI for the plurality of CBR measurement occasions.

83. The non-transitory computer-readable medium of clause 82, further comprising determining to activate the second frequency domain resource in response to the CBR satisfying a first threshold.

84. The non-transitory computer-readable medium of clause 83, further comprising determining to deactivate the second frequency domain resource in response to the CBR being greater than a second threshold.

85. The non-transitory computer-readable medium of any of clauses 82-84, wherein the plurality of CBR measurement occasions is periodic.

86. The non-transitory computer-readable medium of any of clauses 82-84, wherein the plurality of CBR measurement occasions is pseudo-random.

87. The non-transitory computer-readable medium of any of clauses 82-86, wherein determining the CBR comprises filtering a plurality of CBR measurements based on a filter coefficient applied to a previous CBR value.

88. The non-transitory computer-readable medium of any of clauses 82-87, wherein the plurality of CBR measurement occasions is configured by the first UE to include at least a minimum number of slots within the time window.

89. The non-transitory computer-readable medium of any of clauses 82-88, further comprising determining whether to perform a congestion control on the sidelink transmission based on the CBR.

90. The non-transitory computer-readable medium of any of clauses 82-89, wherein the first frequency domain resource is a first component carrier, a first bandwidth part, or a first resource pool and the second frequency domain resource is a second component carrier, a second bandwidth part, or a second resource pool.

91. The non-transitory computer-readable medium of any of clauses 82-90, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers and wherein determining the CBR comprises determining the CBR based on only activated component carriers.

92. The non-transitory computer-readable medium of clause any of clauses 82-90, wherein the first UE is configured with sidelink carrier aggregation for a plurality of component carriers, and wherein determining the CBR comprises measuring the RSSI on one or more non-active component carriers of the plurality of component carriers during the plurality of CBR measurement occasions.