POWER SAVING TECHNIQUE FOR UE TRANSMITTING PERIODIC TRAFFIC

To provide more power efficient SPS transmission for sidelink UEs, methods, apparatuses, and computer-readable medium are provided. An example method may include selecting a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication, the first sidelink transmission resource being associated with one or more subchannels within one or more slots. The example method may further include initiating a timer based on a timer range, the timer range being based on one or more of a battery level or a mobility associated with the UE. The example method may further include reselecting a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon an expiration of the timer.

TECHNICAL FIELD

The present disclosure relates generally to communication systems, and more particularly, to wireless communication systems with semi-persistent scheduling (SPS).

INTRODUCTION

BRIEF SUMMARY

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus at a user equipment (UE) are provided. The apparatus may include a memory and at least one processor coupled to the memory. The memory and the at least one processor coupled to the memory may be configured to select a first sidelink transmission resource for semi-persistent scheduling (SPS) based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots. The memory and the at least one processor coupled to the memory may be further configured to initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. The memory and the at least one processor coupled to the memory may be further configured to initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE.

In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus at a user equipment (UE) are provided. The apparatus may include a memory and at least one processor coupled to the memory. The memory and the at least one processor coupled to the memory may be configured to select randomly a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. The memory and the at least one processor coupled to the memory may be further configured to transmit a sidelink transmission in the resource.

In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus at a UE are provided. The apparatus may include a memory and at least one processor coupled to the memory. The memory and the at least one processor coupled to the memory may be configured to measure reference signal received power (RSRP) associated with a set of resources within a sidelink resource pool. The memory and the at least one processor coupled to the memory may be further configured to select a first subset of resources associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources. The first subset of resources may be outside a random selection resource set available for one or more random selection UEs, the second subset of resources may be within the random selection resource set. The memory and the at least one processor coupled to the memory may be further configured to transmit a sidelink transmission using the first subset of resources or the second subset of resources.

DETAILED DESCRIPTION

Some examples of sidelink communication may include vehicle-based communication devices that can communicate from vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) (e.g., from the vehicle-based communication device to road infrastructure nodes such as a Road Side Unit (RSU)), vehicle-to-network (V2N) (e.g., from the vehicle-based communication device to one or more network nodes, such as a base station), vehicle-to-pedestrian (V2P), cellular vehicle-to-everything (C-V2X), and/or a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. Sidelink communication may be based on V2X or other D2D communication, such as Proximity Services (ProSe), etc. In addition to UEs, sidelink communication may also be transmitted and received by other transmitting and receiving devices, such as Road Side Unit (RSU)107, etc. Sidelink communication may be exchanged using a PC5 interface, such as described in connection with the example inFIG.2. Although the following description, including the example slot structure ofFIG.2, may provide examples for sidelink communication in connection with 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

InFIG.1, the UE104may include an SPS component198. The SPS component198may be configured to select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots. The SPS component198may be further configured to initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. The mobility may be a speed or a velocity associated with the UE. The SPS component198may be further configured to reselect to a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer.

FIG.2includes diagrams200and210illustrating example aspects of slot structures that may be used for sidelink communication (e.g., between UEs104, RSU107, etc.). The slot structure may be within a 5G/NR frame structure in some examples. In other examples, the slot structure may be within an LTE frame structure. Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies. The example slot structure inFIG.2is merely one example, and other sidelink communication may have a different frame structure and/or different channels for sidelink communication. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 7 or 14 symbols, depending on the slot configuration. For slot configuration 0, each slot may include 14 symbols, and for slot configuration 1, each slot may include 7 symbols. Diagram200illustrates a single resource block of a single slot transmission, e.g., which may correspond to a 0.5 ms transmission time interval (TTI). A physical sidelink control channel may be configured to occupy multiple physical resource blocks (PRBs), e.g., 10, 12, 15, 20, or 25 PRBs. The physical sidelink shared channel (PSSCH) may be limited to a single sub-channel. A PSCCH duration may be configured to be 2 symbols or 3 symbols, for example. A sub-channel may comprise 10, 15, 20, 25, 50, 75, or 100 PRBs, for example. The resources for a sidelink transmission may be selected from a resource pool including one or more subchannels. As a non-limiting example, the resource pool may include between 1-27 subchannels. A PSCCH size may be established for a resource pool, e.g., as between 10-100% of one subchannel for a duration of 2 symbols or 3 symbols. The diagram210inFIG.2illustrates an example in which the PSCCH occupies about 50% of a subchannel, as one example to illustrate the concept of PSCCH occupying a portion of a subchannel. The PSSCH occupies at least one subchannel. The PSCCH may include a first portion of sidelink control information (SCI), and the PSSCH may include a second portion of SCI in some examples.

A resource grid may be used to represent the frame structure. Each time slot may include a resource block (RB) (also referred to as physical RBs (PRBs)) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme. As illustrated inFIG.2, some of the REs may include control information in PSCCH and some REs may include demodulation RS (DMRS). At least one symbol may be used for feedback.FIG.2illustrates examples with two symbols for a physical sidelink feedback channel (PSFCH) with adjacent gap symbols. A symbol prior to and/or after the feedback may be used for turnaround between reception of data and transmission of the feedback. The gap enables a device to switch from operating as a transmitting device to prepare to operate as a receiving device, e.g., in the following slot. Data may be transmitted in the remaining REs, as illustrated. The data may comprise the data message described herein. The position of any of the data, DMRS, SCI, feedback, gap symbols, and/or LBT symbols may be different than the example illustrated inFIG.2. Multiple slots may be aggregated together in some aspects.

FIG.3is a block diagram of a first wireless communication device310in communication with a second wireless communication device350based on sidelink. In some examples, the devices310and350may communicate based on V2X or other D2D communication. The communication may be based on sidelink using a PC5 interface. The devices310and the350may comprise a UE, an RSU, a base station, etc. Packets may be provided to a controller/processor375that implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer.

The controller/processor359can be associated with a memory360that stores program codes and data. The memory360may be referred to as a computer-readable medium. The controller/processor359may provide demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing. The controller/processor359is also responsible for error detection using an acknowledgment (ACK) and/or negative ACK (NACK) protocol to support hybrid automatic repeat request (HARQ) operations.

The controller/processor375can be associated with a memory376that stores program codes and data. The memory376may be referred to as a computer-readable medium. The controller/processor375provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing. The controller/processor375is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

At least one of the TX processor368/316, the RX processor356/370, and the controller/processor359/375may be configured to perform aspects in connection with the SPS component198ofFIG.1.

FIG.4illustrates an example400of sidelink communication between devices. The communication may be based on a slot structure including aspects described in connection withFIG.2. For example, the UE402may transmit a sidelink transmission414, e.g., including a control channel (e.g., PSCCH) and/or a corresponding data channel (e.g., PSSCH), that may be received by UEs404,406,408. A control channel may include information (e.g., sidelink control information (SCI)) such as information about time and/or frequency resources that are reserved for the data channel transmission. In one example, other UEs may measure reference signal received power (RSRP) and may avoid transmitting in the resources based on the measured RSRP. For example, the SCI may indicate a number of TTIs, as well as the RBs that will be occupied by the data transmission. The SCI may also be used by receiving devices to avoid interference by refraining from transmitting on the reserved resources. The UEs402,404,406,408may each be capable of sidelink transmission in addition to sidelink reception. Thus, UEs404,406,408are illustrated as transmitting sidelink transmissions413,415,416,420. The sidelink transmissions413,414,415,416,420may be unicast, broadcast or multicast to nearby devices. For example, UE404may transmit transmission413,415intended for receipt by other UEs within a range401of UE404, and UE406may transmit transmission416. Additionally/alternatively, RSU407may receive communication from and/or transmit transmission418to UEs402,404,406,408. One or more of the UEs402,404,406,408, or the RSU407may include an SPS component198.

Sidelink communication may be based on different types or modes of resource allocation mechanisms. In a first resource allocation mode (which may be referred to herein as “Mode 1”), centralized resource allocation may be provided by a network entity. For example, a base station102or180may determine resources for sidelink communication and may allocate resources to different UEs104to use for sidelink transmissions. In this first mode, a UE receives the allocation of sidelink resources from the base station102or180. In a second resource allocation mode (which may be referred to herein as “Mode 2”), distributed resource allocation may be provided. In Mode 2, each UE may autonomously determine resources to use for sidelink transmission. In order to coordinate the selection of sidelink resources by individual UEs, each UE may use a sensing technique to monitor for resource reservations by other sidelink UEs and may select resources for sidelink transmissions from unreserved resources. Devices communicating based on sidelink, may determine one or more radio resources in the time and frequency domain that are used by other devices in order to select transmission resources that avoid collisions with other devices. The sidelink transmission and/or the resource reservation may be periodic or aperiodic, where a UE may reserve resources for transmission in a current slot and up to two future slots (discussed below).

Thus, in the second mode (e.g., Mode 2), individual UEs may autonomously select resources for sidelink transmission, e.g., without a central entity such as a base station indicating the resources for the device. A first UE may reserve the selected resources in order to inform other UEs about the resources that the first UE intends to use for sidelink transmission(s).

In some examples, the resource selection for sidelink communication may be based on a sensing-based mechanism (which may also be referred to as a “sensing procedure”, “sidelink sensing procedure”, “sensing-based resource selection”, or the like). For instance, before selecting a resource for a data transmission, a UE may first determine whether resources have been reserved by other UEs.

For example, as part of a sensing mechanism for resource allocation mode 2, the UE may determine (e.g., sense) whether the selected sidelink resource has been reserved by other UE(s) before selecting a sidelink resource for a data transmission. If the UE determines that the sidelink resource has not been reserved by other UEs, the UE may use the selected sidelink resource for transmitting the data, e.g., in a PSSCH transmission. The UE may estimate or determine which radio resources (e.g., sidelink resources) may be in-use and/or reserved by others by detecting and decoding sidelink control information (SCI) transmitted by other UEs. The UE may use a sensing-based resource selection algorithm to estimate or determine which radio resources are in-use and/or reserved by others. The UE may receive SCI from another UE that includes reservation information based on a resource reservation field included in the SCI. The UE may continuously monitor for (e.g., sense) and decode SCI from peer UEs. The SCI may include reservation information, e.g., indicating slots and RBs that a particular UE has selected for a future transmission. The UE may exclude resources that are used and/or reserved by other UEs from a set of candidate resources for sidelink transmission by the UE, and the UE may select/reserve resources for a sidelink transmission from the resources that are unused and therefore form the set of candidate resources. The UE may continuously perform sensing for SCI with resource reservations in order to maintain a set of candidate resources from which the UE may select one or more resources for a sidelink transmission. Once the UE selects a candidate resource, the UE may transmit SCI indicating its own reservation of the resource for a sidelink transmission. The number of resources (e.g., sub-channels per subframe) reserved by the UE may depend on the size of data to be transmitted by the UE. Although the example is described for a UE receiving reservations from another UE, the reservations may also be received from an RSU or other device communicating based on sidelink.

Sidelink resource reservations may be periodic or aperiodic.FIG.5Aillustrates an example500of time and frequency resources showing aperiodic reservations for sidelink transmissions.FIG.5Billustrates an example525of periodic reservations for sidelink transmissions. The resources may be included in a sidelink resource pool, for example. The resource allocation for each UE may be in units of one or more sub-channels in the frequency domain (e.g., sub-channels SC 1 to SC 4), and may be based on one slot in the time domain. The UE may also use resources in the current slot to perform an initial transmission, and may reserve resources in future slots for retransmissions. In this example, two different future slots may be reserved by UE1 and UE2 for retransmissions. The resource reservation may be limited to a window of time or slots. The initial candidate set of potential resources for a sidelink transmission may include 8 slots by 4 sub-channels, which provides 32 available resource blocks in total. This window may also be referred to as a resource selection window.

A first UE (“UE1) may reserve a sub-channel (e.g., SC 1) in a current slot (e.g., slot 1) for its initial data transmission502, and may reserve additional future slots within the window for data retransmissions (e.g.,504and506). For example, UE1 may reserve sub-channels SC 3 at slots 3 and SC 2 at slot 4 for future retransmissions as shown byFIG.4. UE1 then transmits information regarding which resources are being used and/or reserved by it to other UE(s). UE1 may transmit the information by including the reservation information in the reservation resource field of the SCI, e.g., a first stage SCI.

FIG.5Aillustrates that a second UE (“UE2”) reserves resources in sub-channels SC 3 and SC 4 at time slot 1 for its current data transmission508, and reserve first data retransmission510at time slot 4 using sub-channels SC 3 and SC 4, and reserve second data retransmission512at time slot 7 using sub-channels SC 1 and SC 2 as shown byFIG.5A. Similarly, UE2 may transmit the resource usage and reservation information to other UE(s), such as using the reservation resource field in SCI.

A third UE may consider resources reserved by other UEs within the resource selection window to select resources to transmit its data. The third UE may first decode SCIs within a time period to identify which resources are available (e.g., candidate resources). For example, the third UE may exclude the resources reserved by UE1 and UE2 and may select other available sub-channels and time slots from the candidate resources for its transmission and retransmissions, which may be based on a number of adjacent sub-channels in which the data (e.g., packet) to be transmitted can fit.

WhileFIG.5Aillustrates resources being reserved for an initial transmission and two retransmissions, the reservation may be for an initial transmission and subsequent transmissions or for an initial transmission but not subsequent transmissions.

FIG.5Billustrates an example525of a periodic resource reservation. Periodic resource reservation and signaling may be disabled by configuration. A period with configurable values may be signaled in SCI. As an example, a period may have a value between 0 ms and 1000 ms. Sidelink resources may be reserved periodically, such as for SPS resources. In SPS, initial transmissions of a subsequent period in an SPS flow may be protected by an earlier SPS transmission.FIG.5Billustrates an initial transmission may indication a resource reservation, e.g., at526, for the SPS resources.

The UE may determine an associated signal measurement (such as RSRP) for each resource reservation received by another UE. The UE may consider resources reserved in a transmission for which the UE measures an RSRP below a threshold to be available for use by the UE. A UE may perform signal/channel measurement for a sidelink resource that has been reserved and/or used by other UE(s), such as by measuring the RSRP of the message (e.g., the SCI) that reserves the sidelink resource. Based at least in part on the signal/channel measurement, the UE may consider using/reusing the sidelink resource that has been reserved by other UE(s). For example, the UE may exclude the reserved resources from a candidate resource set if the measured RSRP meets or exceeds the threshold, and the UE may consider a reserved resource to be available if the measured RSRP for the message reserving the resource is below the threshold. The UE may include the resources in the candidate resources set and may use/reuse such reserved resources when the message reserving the resources has an RSRP below the threshold, because the low RSRP indicates that the other UE is potentially distant and a reuse of the resources is less likely to cause interference to that UE. A higher RSRP indicates that the transmitting UE that reserved the resources is potentially closer to the UE and may experience higher levels of interference if the UE selected the same resources.

For example, in a first step, the UE may determine a set of candidate resources (e.g., by monitoring SCI from other UEs and removing resources from the set of candidate resources that are reserved by other UEs in a signal for which the UE measures an RSRP above a threshold value). In a second step, the UE may select N resources for transmissions and/or retransmissions of a TB. As an example, the UE may randomly select the N resources from the set of candidate resources determined in the first step. In a third step, for each transmission, the UE may reserve future time and frequency resources for an initial transmission and up to two retransmissions. The UE may reserve the resources by transmitting SCI indicating the resource reservation. For example, in the example inFIG.5A, the UE may transmit SCI reserving resources for current data transmission508, first data retransmission510, and second data retransmission512.

There may be a timeline for a sensing-based resource selection. For example, the UE may sense and decode the SCI received from other UEs during a sensing window, e.g., a time duration prior to resource selection. Based on the sensing history during the sensing window, the UE may be able to maintain a set of available candidate resources by excluding resources that are reserved by other UEs from the set of candidate resources. A UE may select resources from its set of available candidate resources and transmits SCI reserving the selected resources for sidelink transmission (e.g., a PSSCH transmission) by the UE. There may be a time gap between the UE's selection of the resources and the UE transmitting SCI reserving the resources.

FIG.6illustrates an example timeline600for sidelink resource selection based on sensing. InFIG.6, the UE may receive sidelink transmission610and sidelink transmission612during the sensing window602.FIG.6illustrates an example sensing window including 8 consecutive time slots and 4 consecutive sub-channels, which spans 32 resource blocks. The sidelink transmission610indicates a resource reservation for resource618, and sidelink transmission612indicates a resource reservation for resources614and622. For example, the sidelink transmissions610and612may each include SCI that indicates the corresponding resource reservation. Resource reservations may be periodic or aperiodic. Different reservations of resources may have different priority levels, e.g., with the priority level indicated in the SCI.

A UE receiving the transmissions610and612may exclude the resources614,616, and618as candidate resources in a candidate resource set based on the resource selection window606. In some examples, the sidelink device may exclude the resources614,616, or618based on whether a measured RSRP for the received SCI (e.g., in610or612) meets a threshold. When a resource selection trigger occurs at604, such as the sidelink device having a packet for sidelink transmission, the sidelink device may select resources for the sidelink transmission (e.g., including PSCCH and/or PSSCH) from the remaining resources of the resource pool within the resource selection window606after the exclusion of the reserved resources (e.g.,614,616, and618).FIG.6illustrates an example in which the sidelink device selects the resource620for sidelink transmission. The sidelink device may also select resources622and/or624for a retransmission. After selecting the resources for transmission, the sidelink device may transmit SCI indicating a reservation of the selected resources. Thus, each sidelink device may use the sensing/reservation procedure to select resources for sidelink transmissions from the available candidate resources that have not been reserved by other sidelink devices.

FIG.7is an example diagram700illustrating sidelink resource selection including random selection, partial sensing, and full sensing. As illustrated inFIG.7, random selection, partial sensing, and full sensing may be configured for the same resource pool. A sensing procedure based on a sensing window may be referred to as “full sensing,” whereas a sensing procedure based on a shorter sensing window that may be a subsection of the sensing window may be referred to as “partial sensing.” “Random selection” may be used to refer to a procedure where a UE randomly selects a resource within the resource pool without a sensing procedure. In some aspects, for the resource pool inFIG.7that may be configured with partial sensing, if a UE performs periodic-based partial sensing, at least when the reservation for another TB (when carried in SCI) is enabled for the resource pool and resource selection/reselection is triggered at slot n, the UE may determine a set of Y candidate slots within a resource selection window. In some aspects, the UE may be subject to conditions for determining the Y candidate slots, and the conditions may be associated with discontinuous reception (DRX) that may be enabled for the UE.

As illustrated inFIG.7, a resource selection window may be [n+T1, n+T2], where T1≥0 (may be subject to processing time constraint TProc,0), T2≤remaining packet delay budget (PDB), and T2−T1≤a configured threshold. A UE, such as the UE402, may be configured to monitor SCI according to one or more sidelink resource reserve periods (which may be represented in a list indicated, for example, by a parameter sl-ResourceReservePeriodList that may include P1 and P2). The UE may also be configured to monitor SCI-based on a configurable subset indicated by a bitmap. The UE may monitor SCI in a most recent (k=1) sensing occasion or a second most recent (k=2) sensing occasion.

A UE, such as the UE402, may support semi-persistent scheduling (SPS) reservation. For example, the UE may select a resource R at a time r (such as select a resource R based on the sensing procedure). The UE may repeatedly use the resource on r+P, r+2P, . . . , where P is the packet arrival/transmission periodicity. The resource R may be selected relative to a window. At time r and upon the selection, the UE may generate a timer based on a timer range. For example, the timer may be T=N1and the timer range may be [5 15], where the number may indicate total times of packet transmission. In some aspects, to generate the timer, the UE may randomly select a value within the timer range. Each value within the timer range may be associated with an equal probability to be selected. After each packet transmission using the resource R, the UE may decrease the timer T by 1. For example, at time r, the timer may be T. At time r+P after another packet transmission using the resource R, the timer may be T−1. At time r+2P after yet another packet transmission using the resource R, the timer may be T−2.

After the timer reaches a threshold, such as 1, the UE may determine whether to keep using the same resource R or reselect a different resource. For example, the UE may randomly generate a probability between 0 to 1. If the randomly generated probability is lower than or equal to a threshold, the UE may maintain (i.e., keep using) the same resource R. If the randomly generated probability is greater than the threshold, the UE may reselect a resource R2and may initiate a second timer (e.g., T=N2based on the timer range). The UE may then decrease the timer based on packet transmission using the resource R2. In some aspects, to generate the probability, the UE may randomly select a value between 0 and 1. Each value between 0 and 1 may be associated with an equal probability to be generated.

FIG.8is an example diagram illustrating sidelink SPS resource selection and reselection. As illustrated in example800ofFIG.8, a UE (such as the UE402) may select a set of resources R, including a resource810A and a resource810B. The UE may accordingly initiate a timer T upon selecting the set of resource R. For example, the UE may initiate a first timer of value 13 based on a timer range of [5 15]. The UE may keep using the same set of resource R, which may include resources812A and812B, in a subsequent packet transmission period. The timer may be decreased to 12 in the subsequent packet transmission period. After another ten packet transmission periods, the timer may be decreased to 2. After yet another packet transmission period, the UE may still keep using the same set of resource R, which may now include resources814A and814B; and the timer may be accordingly decreased to 1. When the timer is decreased to 1, a resource selection trigger may be triggered, and the UE may accordingly generate a probability. If the UE reselects a resource based on the generated probability, the resource selection trigger may be referred to as “active.” If the UE maintains the same resource based on the generated probability, the resource selection trigger may be referred to as “inactive.” As illustrated inFIG.8, the UE may reselect a different set of resources which may include resources816A and816B. The UE may initiate a second timer based on the timer range [5 15]. The UE may use the same set of resources which may include resources818A and818B in a subsequent packet transmission period. The UE may maintain the same resource until the next active resource selection trigger.

If the UE maintains the same resource based on the generated probability, the resource selection trigger may be inactive. The UE may use the same set of resources which may include resources820A and820B. The UE may maintain the same resource until the next active resource selection trigger.

Example aspects provided herein may save power for a sidelink UE by reducing the number of sensing occasions where an SPS resource reselection is triggered. If a UE maintains the previously selected resource, it may avoid reselecting the resource. The UE may be able to save power by avoiding a power-consuming sensing procedure for reselecting the resource.

In some aspects, the timer range may be adjusted to save power for a UE. For example, the timer range may be changed from [5 15] to a timer range with a larger maximum/minimum value, [T1T2], where T1>5 or T2>15. For example, the new timer range may be [5 150], [10 15], [50 150], or the like. The changed timer range may be based on a network configuration or UE implementation. In some aspects, the timer range may be based on a battery level or a level of power-saving. For example, if the battery level is below a threshold, such as 10%, the UE may change the timer range to a larger value to save power. In another example, if the UE is a vulnerable road user (VRU) that may use sidelink transmission to periodically report safety-related information for a long time, the level of power-saving may be defined to be high, and the UE may be using a timer range with a larger maximum/minimum value, such as [50 150].

In some aspects, the timer range may be based on mobility associated with the UE. The mobility may be a speed or a velocity associated with the UE. For example, if the mobility of the UE402is low (i.e., the UE402is moving at a speed or velocity lower than a threshold), the timer range may be larger so that the UE402is more likely to reselect resources less often. If the mobility of the UE402is high (i.e., the UE402is moving at a speed or velocity higher than a threshold), the timer range may be smaller so that the UE402is more likely to reselect resources more often.

In some aspects, the timer range may be based on mobility associated with one or more other UEs that may be nearby (such as the UE404and the UE406). For example, if the mobility of the UE404and the UE406is low (i.e., the UE404and the UE406are moving at a speed or velocity lower than a threshold), the timer range may be larger so that the UE402is more likely to reselect resources less often. If the mobility of the UE404and the UE406is high (i.e., the UE404and the UE406are moving at a speed or velocity higher than a threshold), the timer range may be smaller so that the UE402is more likely to reselect resources more often. In some aspects, the UE402may receive an indication of the mobility of the UE404and the UE406via basic safety message (BSM), sensor sharing message, inter-UE coordination message, SCI, or other sidelink messages. The indication of the mobility may indicate speed or velocity of of the UE404and the UE406.

FIG.9is an example diagram illustrating modifying timer range or probability range for sidelink SPS resource selection based on battery level or mobility. As illustrated in example900ofFIG.9, a UE (such as the UE402) may select a set of resources R, including a resource910A and a resource910B. The UE may accordingly initiate a timer T upon selecting the set of resource R. Based on the battery level, the mobility of the UE, or the mobility of the other UEs, the UE may initiate a timer based on a timer range.

By way of example, the UE may initiate a timer of value103based on a timer range of [5 150]. The UE may keep using the same set of resource R, which may include resources912A and912B, in a subsequent packet transmission period. The timer may be decreased to102in the subsequent packet transmission period. After another one hundred packet transmission periods, the timer may be decreased to 2. After yet another packet transmission period, the UE may maintain the same set of resource R, which may now include resources914A and914B; and the timer may be accordingly decreased to 1. When the timer is decreased to 1, a resource selection trigger may be triggered, and the UE may accordingly generate a probability. As illustrated inFIG.9, based on the generated probability being within a probability range (i.e., lower than or equal to a threshold), the UE may reselect a different set of resources which may include resources916A and916B. The UE may initiate a second timer based on the timer range [50 150]. The UE may use the same set of resources which may include resources918A and918B in a subsequent packet transmission period. The UE may maintain the same resource until the next active resource selection trigger. In some aspects, if the battery level, mobility, or other conditions have changed, the UE may initiate the second timer based on a different timer range. For example, if the UE is moving faster upon initiating the second timer, the UE may initiate the second timer based on the timer range [5 15].

In some aspects, the probability threshold (which may correspond to a probability range of 0 to the threshold) may be adjusted to save power for a UE. For example, the probability range may be changed from [0, P1], P1equal to one of 0.02, 0.04, 0.06, or 0.08, to [0, P2] with a larger maximum value, P2>0.8. For example, P2may be one of 0.9, 0.95, 0.99, 0.995, or the like.

The changed probability range may be based on a network configuration or UE implementation. In some aspects, the probability range may be based on a battery level or a level of power-saving. For example, if the battery level is below a threshold, such as 10%, the UE may change the probability range to be associated with a larger maximum value to save power. In another example, if the UE is a vulnerable road user (VRU) that may use sidelink transmission to periodically report safety-related information to an OBU or RSU for a long time, the level of power-saving may be defined to be high, and the UE may be using a probability range with a larger maximum value, such as [0 0.95].

In some aspects, the probability range may be based on mobility associated with the UE. For example, if the mobility of the UE402is low (i.e., the UE402is moving at a speed or velocity lower than a threshold), the probability range may be larger so that the UE402is less likely to reselect resources. If the mobility of the UE402is high (i.e., the UE402is moving at a speed or velocity higher than a threshold), the probability range may be smaller so that the UE402is more likely to reselect resources.

In some aspects, the timer range may be based on mobility associated with one or more other UEs that may be nearby (such as the UE404and the UE406). For example, if the mobility of the UE404and the UE406is low (i.e., the UE404and the UE406are moving at a speed or velocity lower than a threshold), the timer range may be larger so that the UE402is less likely to reselect resources. If the mobility of the UE404and the UE406is high (i.e., the UE404and the UE406are moving at a speed or velocity higher than a threshold), the timer range may be smaller so that the UE402is more likely to reselect resources more often. In some aspects, the UE402may receive an indication of mobility of the UE404and the UE406via basic safety message (BSM), sensor sharing message, inter-UE coordination message, SCI, or other sidelink messages. The indication of the mobility may indicate speed or velocity of of the UE404and the UE406.

FIG.10is an example diagram illustrating modifying timer range or probability range for sidelink SPS resource selection based on battery level or mobility. As illustrated in example1000ofFIG.10, a UE (such as the UE402) may select a set of resources R, including a resource1010A and a resource1010B. The UE may accordingly initiate a timer T upon selecting the set of resource R. Based on the battery level, the mobility of the UE, or the mobility of the other UEs, the UE may initiate a timer based on a timer range.

By way of example, the UE may initiate a timer of value103based on a timer range of [5 150]. The UE may maintain the same set of resource R, which may include resources1012A and1012B, in a subsequent packet transmission period. The timer may be decreased to102in the subsequent packet transmission period. After another one hundred packet transmission periods, the timer may be decreased to 2. After yet another packet transmission period, the UE may still maintain the same set of resource R, which may include resources1014A and1014B; and the timer may be accordingly decreased to 1. When the timer is decreased to 1, a resource selection trigger may be triggered, and the UE may accordingly generate a probability based on the probability range. For example, the UE may generate a probability based on a random number between 0 and 1. As one example, the UE may generate a probability of value 0.91.

As illustrated inFIG.10, based on the generated probability being within a probability range of [00.95] (which may be equivalent to lower than or equal to a threshold 0.95), the UE may maintain the same set of resources which may include resources1016A and1016B. The UE may initiate a second timer based on the timer range [50 150]. The UE may use the same set of resources which may include resources1018A and1018B in a subsequent packet transmission period. The UE may maintain the same resource until the next active resource selection trigger. In some aspects, if the battery level, mobility, or other conditions have changed, the UE may initiate the second timer based on a different timer range. For example, if the UE is moving faster upon initiating the second timer, the UE may initiate the second timer based on the timer range [5 15].

FIG.11is a communication flow1100between a base station1104and UEs1102,1106, and1108that includes sidelink SPS resource selection and reselection. As illustrated inFIG.11, the base station1104may transmit a configuration of timer range or probability range1110to the UEs1102,1106, and1108. At1112, The UE1102may select a set of SPS resources by performing sensing described in connection withFIGS.5A,5B, and6. The UE1102may also initiate a first timer based on a timer range described in connection withFIGS.8-10. The UE1102may use the set of SPS resources to periodically transmit packets1114and a number of packets1114N to the UE1106or the UE1108. Upon transmitting a packet1114using the set of SPS resources, the UE1102may decrease the first timer by one. At1118, the UE1102may change a timer range or a probability range based on a mobility of the UE1102, a mobility1116of the UE1106or the UE1108, or a battery level of the UE1102. The UE may perform1118at any point, such as before or after receiving the configuration of timer range or probability range1110, before or after selecting SPS resource at1112, or the like. In some aspects, the UE1102, the UE1106, or the UE1108may transmit the mobility1116to the base station1104. The base station may transmit a new configuration of timer range or probability range1110to the UE1102based on the mobility1116. In some aspects, the base station1104may transmit the new configuration of timer range or probability range1110via RRC signaling. As one example, the UE1102may change the timer range or the probability range at1118after initiating a timer at1112and before the first timer expires (e.g., decrease to 1). In some aspects, the UE may change the timer range or the probability range as described in connection withFIGS.8-10.

At1120, the first timer may expire, and the UE1102may initiate a second timer and generate a probability. If the generated probability is within the probability range, the UE1102may maintain the same SPS resource. If the generated probability is outside the probability range, the UE1102may reselect the SPS resource based on a sidelink sensing procedure. The UE1102may use the reselected SPS resource or the same SPS resource to periodically transmit packets1124and a number of packets1124N to the UE1106or the UE1108. Upon transmitting a packet1124using the set of SPS resources, the UE1102may decrease the second timer by one. At1126, upon expiration (e.g., decrease to 1) of the second timer, the UE may initiate a third timer and generate a probability. The probability may be randomly generated number between zero and one.

Because a UE's mobility (i.e., speed, velocity, or the like) may affect channel interference pattern, the UE's mobility may serve as a basis for determining resource reselection frequency (e.g., based on the timer range or the probability range). For example, a lower speed UE may be associated with a slow channel interference pattern, and maintaining the same periodically resource may be sufficient for the UE's transmission.

Other than a UE's mobility, battery level, or level of power-saving, the timer range or the probability range may be further based on a system channel loading congestion level, a priority of an application associated with a transmission on the selected SPS resource, a total number of resources associated with the selected SPS resource, or the like. For example, with higher system loading, the UE1102may be configured with a timer range with a larger maximum/minimum value or a probability range with a larger maximum value so that the UE1102may be more likely to maintain the selected resource. The UE1102may determine the system loading based on a channel busy ratio (CBR) measurement report. In some aspects, if the priority of the application associated with the transmission on the selected SPS resource is low, the UE1102may be configured with a timer range with a larger maximum/minimum value or a probability range with a larger maximum value so that the UE1102may be more likely to maintain the selected resource. In some aspects, when the total number of initially selected resources is large, the UE may be configured with a timer range with a smaller maximum/minimum value or a probability range with a smaller maximum value so that the UE1102may be more likely to reselect the resources. As one example, if the UE1102selected a large number of resources and the system channel loading is high, the UE1102may be configured with a smaller maximum/minimum value or a probability range with a smaller maximum value so that the UE1102may be more likely to reselect the resources.

FIG.12is an example diagram1200illustrating sidelink resource selection including random selection, partial sensing, and full sensing. As illustrated inFIG.12, random selection, partial sensing, and full sensing may be configured for the same resource set. A sensing procedure based on a sensing window may be referred to as “full sensing,” whereas a sensing procedure based on a shorter sensing window that may be a subsection of the sensing window may be referred to as “partial sensing.” “Random selection” may be used to refer to a procedure where a UE randomly selects a resource within the resource set without a sensing procedure. For example, as illustrated inFIG.12, a UE may perform sensing between time n+TAand time n+TB. A partial sensing UE may configure TAand TBto adjust the sensing window. TAand TBmay be positive, negative, or zero (relative to a set of candidate slots). If n+TAis equal to n+TB, the UE may be performing random selection. Some UEs may be configured to perform random selection in a power-saving mode and perform sensing in a normal operating mode. Some UEs, such as reduced capability UEs, may be configured to perform random selection without performing sensing.

In some aspects, for the resource set inFIG.12that may be configured with partial sensing, if a UE performs periodic-based partial sensing, at least when the reservation for another TB (when carried in SCI) is enabled for the resource set and resource selection/reselection is triggered at slot n, the UE may determine a set of Y candidate slots within a resource selection window. In some aspects, the UE may be subject to conditions for determining the Y candidate slots, and the conditions may be associated with discontinuous reception (DRX) that may be enabled for the UE. A UE, such as the UE402, may be configured to monitor SCI according to one or more sidelink resource reserve periods (which may be represented in a list indicated, by way of example, by a parameter sl-ResourceReservePeriodList that may include P1 and P2). The UE may also be configured to monitor SCI based on a configurable subset indicated by a bitmap. The UE may monitor SCI in a most recent (k=1) sensing occasion or a second most recent (k=2) sensing occasion.

Because UEs that perform random selection, partial sensing, and full sensing (which may also be referred to as “random selection UEs,” “partial sensing UEs,” and “full sensing UEs”) may be configured with the same resource set, transmissions from random selection UEs may collide with transmissions from partial sensing or full sensing UEs. The collisions may cause system performance degradation. In addition, a sensing UE's transmission may be wasted because of interference from a nonsensing UE (e.g., a random selection UE) that may not be aware of the sensing UE's reservation. Some wireless communication systems may configure a separate resource set for random selection UEs in order to avoid resource collision between random selection and partial/full sensing UEs. However, such a configuration may be wasteful of resources when there may be no or few random selection UEs in an area. The separate resource set may not be able to adapt even if there is no random selection UEs in the area.

Example aspects provided herein may facilitate avoiding resource collision between random selection and partial/full sensing UEs. By configuring a random selection resource set that may be available for random selection UEs, the random selection UEs may avoid transmitting outside the random selection resource set that may collide with transmissions from partial/full sensing UEs. By configuring the random selection resource set to be also available for the sensing UEs, waste of resources may be avoided when there are no or few random selection UEs in an area.

FIG.13is an example diagram1300illustrating random selection resource set and sidelink resource pool. As illustrated inFIG.13, within a sidelink resource pool1302available for sensing UEs, a random selection resource set (which may be otherwise referred to as “a set of time-frequency resources,” “a set of restricted resources,” or the like)1304for random selection transmissions may be configured. In some aspects, the random selection resource set1304may be applicable to all random selection transmissions. In other words, a UE402may randomly select resources in the random selection resource set for random selection transmissions and may not randomly select resources outside the random selection resource set for the random selection transmissions. In some aspects, the random selection resource set1304may be applicable to random selection of resource for initial packets transmissions with no further restrictions on random selection of resource for retransmissions. In other words, a UE402may randomly select resources in the random selection resource set1304for initial random selection transmissions and may not randomly select resources outside the random selection resource set1304for the initial random selection transmissions. However, the UE402may randomly select resources outside the random selection resource set1304(and within the sidelink resource pool1302) for subsequent retransmissions of the same packet. A sensing UE may be able to detect a reservation associated with the initial transmission.

In some aspects, the random selection resource set1304may be applicable to initial random selection packets transmissions for a UE402that may perform the random selection and on-demand or partial sensing. In some aspects, the random selection resource set1304may be applicable to all random selection transmissions for a UE that may not perform sensing. In some aspects, the random selection resource set may be periodically dedicated for random selection transmission with a periodicity. For example, as illustrated inFIG.13, the random selection resource set1304may be associated with a period1306, and a second random selection resource set1308may be dedicated for random selection after a period1306. In some aspects, the periodicity may be (pre)configured to the UE402or configured by a base station in a network.

A UE may be configured with a pre-emption where the UE may signal the UE's selected resource while receiving a reservation (such as via SCI) on the same resource with a higher priority. The UE may be configured to reselect the resource because the received reservation pre-empts the UE's resource selection. In some aspects, for the UE1102operating with a timer range with a larger maximum/minimum value or a probability range with a larger maximum value for power-saving, pre-emption may be disabled.

In some aspects, random selection UEs may signal in first stage SCI to reserve the periodic resource occupation.FIG.14is an example diagram1400illustrating a UE's reservation in a random selection resource set. As illustrated inFIG.14, within a random sidelink resource pool1402available for sensing UEs, a random selection resource set1404for random selection transmissions may be configured. The random selection resource set1404may be associated with a period1406, and a second random selection resource1410may be dedicated for random selection after a period1406from the random selection resource pool1402. A third random selection resource1412may be configured for random selection for a time after a third period. As illustrated inFIG.14, a UE402may transmit a reservation1408reserving the periodic resources, including resources in the second random selection resource1410and the third random selection resource1412. In some aspects, the UE402may transmit the reservation1408via first stage SCI. A sensing UE may avoid using the reserved resource when the sensing UE decodes the first stage SCI. In some aspects, the UE402may transmit with resource at a first time, and signal in the first stage SCI, but does not transmit again with the reserved resource at a second time. For example, as illustrated inFIG.14, the UE402(which may be referred to as “UE 1”) may reserve the periodic resource by transmitting the reservation1408but may or may not use a resource in the second random selection resource1410. The reserved resource in the second random selection resource1410may be used by a second UE. In other words, a random selection UE may reserve resource on behalf of all random selection UEs. The UE may or may not transmit in the reserved resources.

In some aspects, to avoid potential resource collision among random selection UEs in the random selection resource set, an indication (which may be a one-bit indication) may be used to indicate whether the reserved resource at time is used by the random selection UE. For example, as illustrated inFIG.14, the UE402or another UE that uses the reserved resource in the second random selection resource1410may transmit an indication. By transmitting an indication, other random selection UEs that may perform on-demand sensing may avoid using the resource after one periodicity ( ).

In some aspects, a sensing UE may also be able to detect the indication. In some aspects, based on a lack of indication of transmission from a random selection UE, a sensing UE may be able to transmit in the reserved resources, making resource usage within the system more efficient. For example, as illustrated inFIG.14, a sensing UE may perform sensing within the sidelink resource pool. Based on the sensing (which may be based on a lack of indication of transmission from a random selection UE or based on an RSRP threshold) within the set, the sensing UE may select a resource within the third random selection resource1412or a resource1414outside the third random selection resource1412. The sensing UE may use the same or different RSRP thresholds for resources within the third random selection resource1412and resources outside the third random selection resource1412.

In some aspects, the size of the random selection resource set (which may be based on the period and the number of resources within a period) may be dynamically configured. For example, a base station may configure a small number of resources within the random selection resource set, then the base station or a UE may adapt the number of resources within the random selection resource set when there are more random selection UEs. In another example, one or more UEs may exchange measurements, such as a channel busy ratio (CBR) within the random selection resource set, and determine a periodicity. The one or more UEs may determine the periodicity based on a voting mechanism. In some aspects, one or more sensing UEs may perform CBR measurements, determine a periodicity and transmit the determined periodicity to the one or more random selection UEs. In another example, a random selection UE may receive a sequence to receive the periodicity. For example, a cyclic shift associated with the sequence may be indicating a periodicity, and different cyclic shifts may be indicating different periodicity. In some aspects, a random selection UE may receive more than one periodicity. Among the more than one periodicities, the random selection UE may pick a periodicity transmitted in a resource with a largest RSRP or the largest periodicity. In another example, based on the CBR, a UE or a base station may increase the number of resources within the random selection resource set by decreasing the period or by expanding the number of resources within each period. In one example, a UE may detect that a CBR within the random selection resource set may be higher than a CBR threshold and set a smaller period based on the CBR being higher than the CBR threshold. In some aspects, the sensing UEs may know the status of the random selection resource set by checking a range (e.g., the smallest value) signaled by all random selection UEs. When a random selection UE supports discontinuous reception (DRX), the random selection UE may tune the DRX cycle to multiple times to maximize power saving random.FIG.15is an example diagram1500illustrating the adjustment of a period associated with a random selection resource set. As illustrated inFIG.15, within a sidelink resource pool1502available for sensing UEs, a random selection resource set1504for random selection transmissions may be configured. The random selection resource set1504may be associated with a period1506. Based on a high CBR or a high number of random selection UEs within an area, the period1506may be changed (by a base station or a UE) to a smaller period1508. Therefore, within a timeframe, the amount of resources in a random selection resource set may be increased.

FIG.16is a communication flow1600between a base station1650and UEs that may perform the random selection and sensing, including a random selection UE1602, a random selection UE1604, and a sensing UE1606. The random selection UE1602and the random selection UE1604may be able to perform partial sensing. As illustrated inFIG.16, the base station1650, a sensing UE, a random selection UE, or one or more UEs (e.g., as previously described with the CBR measurements and the voting mechanism) may transmit a periodicity of a random selection resource set to each UEs in the area, including the random selection UE1602, the random selection UE1604, and the sensing UE1606. At1610, the UE1602may randomly select a resource in the random selection set. The UE1602may transmit a communication1612based on the select resource. In some aspects, the UE1602may transmit a reservation1614reserving a set of periodic resources, which includes the resource, e.g., as described in connection withFIG.9. Another random selection UE may use the reserved resource. For example, the random selection UE1604may transmit a communication1618in the reserved resource. In some aspects, prior to transmitting the communication1618, the random selection UE1604may transmit an indication1616to indicate that the random selection UE1604will use the reserved resource. In some aspects, based on a lack of indication, a sensing UE, such as the sensing UE1606or the random selection UE1602that may perform on-demand sensing, may select the reserved based on sensing at1620and may accordingly transmit a communication1622.

FIG.17is a flowchart1700of a method of wireless communication. The method may be performed by a UE (e.g., the UE104, the UE402, the UE1102, or other UEs; the apparatus1902). The method may be used for power-saving for a sidelink UE with SPS transmissions.

At1702, the UE may select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots. For example, the UE1102may select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots at1112. As one example, a UE402may select a first sidelink transmission resource, including the resource910A and the resource910B. In some aspects,1702may be performed by the SPS component1942ofFIG.19.

At1704, the UE may initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. For example, at1112, the UE1102may initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. As one example, as illustrated inFIG.9, a UE402may initiate a timer with a value of 103 based on a timer range of [50 150] based on the UE402's battery level, mobility, or the like. In some aspects,1704may be performed by the timer component1944ofFIG.19.

At1706, the UE may reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer. For example, at1120, the UE1102may reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer. As one example, as illustrated inFIGS.9-10, a UE402may reselect a second sidelink transmission resource including resource916A and resource916B or maintain the first sidelink transmission resource including resource1016A and resource1016B. In some aspects,1706may be performed by the reselect component1948ofFIG.19.

FIG.18is a flowchart1800of a method of wireless communication. The method may be performed by a UE (e.g., the UE104, the UE402, the UE1102, or other UEs; the apparatus1902). The method may be used for power-saving for a sidelink UE with SPS transmissions.

In some aspects, at1801, the UE may receive, from a base station via RRC, a configuration for the probability range or the timer range. For example, the UE1102may receive configuration of timer range or probability range1110from the base station1104via RRC. In some aspects,1801may be performed by the reception component1930ofFIG.19.

At1802, the UE may select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots. For example, the UE1102may select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The first sidelink transmission resource may be associated with one or more subchannels within one or more slots at1112. As one example, a UE402may select a first sidelink transmission resource, including the resource910A and the resource910B. In some aspects,1802may be performed by the SPS component1942ofFIG.19. In some aspects, an SCI-based pre-emption associated with the first sidelink transmission resource or the second sidelink transmission resource is disabled for the UE.

At1804, the UE may initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. For example, at1112, the UE1102may initiate a timer based on a timer range. The timer range may be based on one or more of a battery level or a mobility associated with the UE. As one example, as illustrated inFIG.9, a UE402may initiate a timer with a value of 103 based on a timer range of [50 150] based on the UE402's battery level, mobility, or the like. In some aspects,1804may be performed by the timer component1944ofFIG.19.

In some aspects, the timer range may be associated with a maximum value and a minimum value, the maximum value or the minimum value may be negatively correlated (which may be otherwise referred to as “inversely correlated”) with at least one of the mobility or the battery level associated with the UE. In some aspects, “negatively correlated” may refer to a relationship between two variables in which one variable increases as the other decreases, and vice versa. For example, if speed or velocity decreases, the the maximum value or the minimum value may increase. In another example, if battery level decreases, the the maximum value or the minimum value may increase. In some aspects, at1803, the UE may be configured to change the timer range, such as by changing the minimum value or the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold. For example, as illustrated inFIG.9, In some aspects,1803may be performed by the timer component1944ofFIG.19.

In some aspects, at1806, the UE may decrease the timer upon transmitting a packet using the first sidelink transmission resource. For example, as illustrated inFIG.11, the UE1102may decrease the timer upon transmitting a packet (such as the packet1114) using the first sidelink transmission resource. In some aspects,1806may be performed by the timer component1944ofFIG.19.

In some aspects, at1814, the UE may receive, from each of one or more UEs, an indication of a mobility associated with the UE (e.g., each of the one or more UEs). In some aspects,1814may be performed by the reception component1930ofFIG.19. In some aspects, the timer range may be further based on the mobility for each of the one or more UEs. In some aspects, the timer range may be associated with a maximum value and a minimum value, the maximum value or the minimum value may be negatively correlated with the one or more mobility associated with the one or more UEs. For example, as illustrated inFIG.9, the mobility associated with the UE406and the UE404may be negatively correlated with a maximum/minimum value of the timer range. For example, if the UE406or the UE404is moving fast, the timer range may be associated with a smaller maximum/minimum value.

In some aspects, at1808, the UE may determine, upon expiration of the timer, whether to reselect the second sidelink transmission resource or maintain the first sidelink transmission resource based on a probability being within a probability range. In some aspects, the probability may be randomly generated number between zero and one. For example, the UE1102may determine, upon expiration of the timer, whether to reselect the second sidelink transmission resource or maintain the first sidelink transmission resource based on a probability being within a probability range at1120. In some aspects,1808may be performed by the reselect component1948ofFIG.19. In some aspects, the probability range may be further based on the received indication of the mobility for each of the one or more UEs (received at1803). For example, as illustrated inFIG.9, the mobility associated with the UE406and the UE404may be negatively correlated with a maximum value of the probability range. For example, if the UE406or the UE404is moving fast, the probability range may be associated with a smaller maximum value. In some aspects, a maximum value associated with the probability range is negatively correlated with at least one of the mobility or the battery level associated with the UE.

In some aspects, at1810, the UE may change the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold. For example, as illustrated inFIG.9, the UE402may increase the maximum value from 0.8 to 0.95 based on a low battery level or low mobility (e.g., UE402not moving at a speed/velocity higher than a threshold). In some aspects,1810may be performed by the probability component1946ofFIG.19. In some aspects, the timer range or the probability range may be further based on one or more of: a system channel loading congestion level, a total number of resources associated with the first sidelink transmission resource, or a priority of the UE-to-UE communication. For example, a maximum value associated with the probability range may be positively correlated with the system channel loading congestion level. In another example, the timer range may be associated with a maximum value and a minimum value. The maximum value or the minimum value may be negatively correlated with the total number of resources. In some aspects, a maximum value associated with the probability range may be negatively correlated with the total number of resources.

At1812, the UE may reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer. For example, at1120, the UE1102may reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer. As one example, as illustrated inFIGS.9-10, a UE402may reselect a second sidelink transmission resource including resource916A and resource916B or maintain the first sidelink transmission resource including resource1016A and resource1016B. In some aspects,1812may be performed by the reselect component1948ofFIG.19.

FIG.19is a diagram1900illustrating an example of a hardware implementation for an apparatus1902. The apparatus1902may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus1902may include a cellular baseband processor1904(also referred to as a modem) coupled to a cellular RF transceiver1922. In some aspects, the apparatus1902may further include one or more subscriber identity modules (SIM) cards1920, an application processor1906coupled to a secure digital (SD) card1908and a screen1910, a Bluetooth module1912, a wireless local area network (WLAN) module1914, a Global Positioning System (GPS) module1916, or a power supply1918. The cellular baseband processor1904communicates through the cellular RF transceiver1922with the UE104and/or BS102/180. The cellular baseband processor1904may include a computer-readable medium/memory. The computer-readable medium/memory may be non-transitory. The cellular baseband processor1904is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor1904, causes the cellular baseband processor1904to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor1904when executing software. The cellular baseband processor1904further includes a reception component1930, a communication manager1932, and a transmission component1934. In some aspects, the reception component1930may be configured to receive, from a base station RRC, a configuration for the probability range or the timer range and receive, from each of one or more UEs, an indication of a mobility associated with the UE, e.g., as illustrated in connection with1801and1814. The communication manager1932includes the one or more illustrated components. The components within the communication manager1932may be stored in the computer-readable medium/memory and/or configured as hardware within the cellular baseband processor1904. The cellular baseband processor1904may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359. In one configuration, the apparatus1902may be a modem chip and include just the cellular baseband processor1904, and in another configuration, the apparatus1902may be the entire UE (e.g., sec350ofFIG.3) and include the additional modules of the apparatus1902.

The communication manager1932may include an SPS component1942that may be configured to select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication, e.g., as described in connection with1702ofFIG.17, or1802ofFIG.18. The communication manager1932may further include a timer component1944that may be configured to initiate a timer based on a timer range, decrease the timer upon transmitting a packet using the first sidelink transmission resource, or change the timer, e.g., as described in connection with1704ofFIG.17, or1803,1804, or1806ofFIG.18. The communication manager1932may further include a probability component1946that may be configured to change the maximum value associated with a probability range, e.g., as described in connection with1810ofFIG.18. The communication manager1932may further include a reselect component1948that may be configured to determine, upon expiration of the timer, whether to reselect the second sidelink transmission resource or maintain the first sidelink transmission resource based on a probability being within a probability range and reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer, e.g., as described in connection with1706ofFIG.17, or1812ofFIG.18.

As shown, the apparatus1902may include a variety of components configured for various functions. In one configuration, the apparatus1902, and in particular the cellular baseband processor1904, may include means for selecting a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication. The cellular baseband processor1904may further include means for initiating a timer based on a timer range. The cellular baseband processor1904may further include means for reselecting a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer. The cellular baseband processor1904may further include means for changing the minimum value or the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold. The cellular baseband processor1904may further include means for decreasing the timer upon transmitting a packet using the first sidelink transmission resource. The cellular baseband processor1904may further include means for receiving, from each of one or more UEs, an indication of a mobility associated with the UE. The cellular baseband processor1904may further include means for determining, upon expiration of the timer, whether to reselect the second sidelink transmission resource or maintain the first sidelink transmission resource based on a probability being within a probability range. The cellular baseband processor1904may further include means for receiving, from each of one or more UEs, an indication of a mobility associated with the UE. The cellular baseband processor1904may further include means for changing the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold. The cellular baseband processor1904may further include means for changing the maximum value to be greater than 0.8. The cellular baseband processor1904may further include means for receiving, from a base station via RRC, a configuration for the probability range or the timer range. The means may be one or more of the components of the apparatus1902configured to perform the functions recited by the means. As described supra, the apparatus1902may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the means.

Example aspects provided herein may be used by a sidelink UE for saving power. The UE may save power by reducing the number of sensing occasions where an SPS resource reselection is triggered. In some aspects, the UE may be able to save power by triggering the SPS resource reselection less frequently based on a battery level of the UE, mobility of the UE, mobility of other UEs, or the like. By triggering SPS resource reselection less frequently, the UE may reduce the number of power-consuming sensing. In some aspects, the UE may be able to trigger an SPS resource reselection less frequently by increasing the time between SPS resource reselection triggers. In some aspects, the UE may be able to trigger an SPS resource reselection less frequently by decreasing the probability of activating an SPS resource reselection trigger.

FIG.20is a flowchart2000of a method of wireless communication. The method may be performed by a UE (e.g., the UE104, the UE402, the UE1602, the UE1604, or other UEs; the apparatus2202).

At2002, the UE may select randomly a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. For example, the UE1602may select randomly, at1610, a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. As one example, a UE402may select randomly a resource in a random selection resource set1304. The random selection resource set1304may be within a sidelink resource pool1302for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. In some aspects,2002may be performed by the selection component2242ofFIG.22.

At2004, the UE may transmit a sidelink transmission in the resource. For example, the UE1602may transmit a sidelink transmission (e.g., the communication1612) in the resource. In some aspects,2004may be performed by the sidelink component2244ofFIG.22.

FIG.21is a flowchart2100of a method of wireless communication. The method may be performed by a UE (e.g., the UE104, the UE402, the UE1602, the UE1604, or other UEs; the apparatus2202).

In some aspects, at2101, the UE may receive, from a base station, a periodicity associated with the random selection resource set. For example, the UE1602may receive from a base station1650, a periodicity1608associated with the random selection resource set. In some aspects,2101may be performed by the periodicity component2248ofFIG.22.

At2102, the UE may select randomly a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. For example, the UE1602may select randomly, at1610, a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. As one example, a UE402may select randomly a resource in a random selection resource set1304. The random selection resource set1304may be within a sidelink resource pool1302for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. In some aspects,2102may be performed by the selection component2242ofFIG.22.

At2104, the UE may transmit a sidelink transmission in the resource. For example, the UE1602may transmit a sidelink transmission (e.g., the communication1612) in the resource. In some aspects,2104may be performed by the sidelink component2244ofFIG.22.

In some aspects, the random selection resource set is periodic and may be associated with a periodicity. In some aspects, at2106, the UE may reserve a set of periodic resources including the resource by transmitting a first stage SCI. For example, the UE402may reserve a set of periodic resources including the resource in904, the resource in910, and the resource in912. In some aspects,2106may be performed by the sidelink component2244ofFIG.22. In some aspects, the periodicity associated with the random selection resource set may be negatively correlated with a total number of random selection UEs within an area or a CBR associated with the random selection resource set. In some aspects, a number of resources associated with the random selection resource set may be positively correlated with a total number of random selection UEs within an area or a CBR associated with the random selection resource set. For example, as illustrated inFIG.10, the period1506may be changed to a smaller period1508based on a CBR or a total number of random selection UEs within an area.

In some aspects, at2108, the UE may transmit an indication indicating whether the UE will transmit in a second resource of the set of periodic resources. For example, the UE402may transmit an indication indicating whether the UE will transmit in a second resource in910of the set of periodic resources. In some aspects,2108may be performed by the sidelink component2244ofFIG.22.

In some aspects, at2110, the UE may transmit a sidelink transmission in the second resource. For example, the UE402may transmit a sidelink transmission in the second resource in910. In some aspects,2110may be performed by the sidelink component2244ofFIG.22.

In some aspects, the sidelink transmission at2104may be an initial transmission, and the UE may measure, at2112, RSRP associated with a set of resources within the sidelink resource pool within a sensing time window. For example, the UE1602may perform sensing and measure RSRP associated with a set of resources at1620. In some aspects,2112may be performed by the sensing component2246ofFIG.22.

In some aspects, at2114, the UE may select a subsequent resource from a subset of resources associated with an RSRP below a threshold within the set of resources for one or more subsequent sidelink retransmissions associated with the initial transmission. For example, the UE1602may perform sensing and select a subsequent resource from a subset of resources associated with an RSRP below a threshold within the set of resources for one or more subsequent sidelink retransmissions (e.g., communication1622) associated with the initial transmission.

In some aspects, at2116, the UE may select randomly a subsequent resource in the random selection resource set for one or more subsequent sidelink transmissions. For example, the UE402may select randomly a subsequent resource in the random selection resource set808for one or more subsequent sidelink transmissions. In some aspects,2116may be performed by the selection component2242ofFIG.22. In some aspects, the sidelink transmission may be an initial transmission, and the UE may select randomly, at2116, a subsequent resource in the random selection resource set for one or more subsequent sidelink transmissions associated with the initial transmission.

FIG.22is a diagram2200illustrating an example of a hardware implementation for an apparatus2202. The apparatus2202may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus2202may include a cellular baseband processor2204(also referred to as a modem) coupled to a cellular RF transceiver2222. In some aspects, the apparatus2202may further include one or more subscriber identity modules (SIM) cards2220, an application processor2206coupled to a secure digital (SD) card2208and a screen2210, a Bluetooth module2212, a wireless local area network (WLAN) module2214, a Global Positioning System (GPS) module2216, or a power supply2218. The cellular baseband processor2204communicates through the cellular RF transceiver2222with the UE104and/or BS102/180. The cellular baseband processor2204may include a computer-readable medium/memory. The computer-readable medium/memory may be non-transitory. The cellular baseband processor2204is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor2204, causes the cellular baseband processor2204to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor2204when executing software. The cellular baseband processor2204further includes a reception component2230, a communication manager2232, and a transmission component2234. In some aspects, the reception component2230may be configured to receive, from a base station RRC, a configuration for the probability range or the timer range and receive, from each of one or more UEs, an indication of a mobility associated with the UE, e.g., as illustrated in connection with2101and2114. The communication manager2232includes the one or more illustrated components. The components within the communication manager2232may be stored in the computer-readable medium/memory and/or configured as hardware within the cellular baseband processor2204. The cellular baseband processor2204may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359. In one configuration, the apparatus2202may be a modem chip and include just the cellular baseband processor2204, and in another configuration, the apparatus2202may be the entire UE (e.g., sec350ofFIG.3) and include the additional modules of the apparatus2202.

The communication manager2232may include a selection component2242that is configured to select randomly a resource in a random selection resource set including one or more subchannels within one or more slots or select randomly a subsequent resource in the random selection resource set for one or more subsequent sidelink transmissions, e.g., as described in connection with2002ofFIG.20,2102ofFIG.21, or2116ofFIG.21. The communication manager2232may further include a sidelink component2244that may be configured to transmit a sidelink transmission, reserve a set of periodic resources including the resource by transmitting a first stage SCI, or transmit an indication indicating whether the UE will transmit in a second resource of the set of periodic resources, e.g., as described in connection with2004ofFIG.20,2104ofFIG.21,2106ofFIG.21,2108ofFIG.21, or2110ofFIG.21. The communication manager2232may further include a sensing component2246that may be configured to measure RSRP associated with a set of resources within the sidelink resource pool within a sensing time window and select a subsequent resource from a subset of resources associated with an RSRP below a threshold within the set of resources for one or more subsequent sidelink retransmissions associated with the initial transmission, e.g., as described in connection with2112ofFIG.21, or2114ofFIG.21. The communication manager2232may further include a periodicity component2248that may be configured to receive, from a base station, a periodicity associated with the random selection resource set, e.g., as described in connection with2101ofFIG.21.

As shown, the apparatus2202may include a variety of components configured for various functions. In one configuration, the apparatus2202, and in particular the cellular baseband processor2204, may include means for selecting randomly a resource in a random selection resource set including one or more subchannels within one or more slots. The random selection resource set may be within a sidelink resource pool for UE-to-UE communication and may be available for a sidelink sensing procedure for the UE-to-UE communication. The cellular baseband processor2204may further include means for transmitting a sidelink transmission in the resource. The cellular baseband processor2204may further include means for selecting randomly a subsequent resource in the random selection resource set for one or more subsequent sidelink transmissions. The cellular baseband processor2204may further include means for selecting randomly a subsequent resource in the sidelink resource pool for one or more subsequent sidelink retransmissions associated with the initial transmission. The cellular baseband processor2204may further include means for measuring RSRP associated with a set of resources within the sidelink resource pool within a sensing time window. The cellular baseband processor2204may further include means for selecting a subsequent resource from a subset of resources associated with an RSRP below a threshold within the set of resources for one or more subsequent sidelink retransmissions associated with the initial transmission. The cellular baseband processor2204may further include means for reserving a set of periodic resources including the resource by transmitting a first stage SCI. The cellular baseband processor2204may further include means for transmitting an indication indicating whether the UE will transmit in a second resource of the set of periodic resources. The cellular baseband processor2204may further include means for receiving, from a base station, a periodicity associated with the random selection resource set. The means may be one or more of the components of the apparatus2202configured to perform the functions recited by the means. As described supra, the apparatus2202may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the means.

FIG.23is a flowchart2300of a method of wireless communication. The method may be performed by a UE (e.g., the UE104, the UE402, the UE1606, or other UEs; the apparatus2402).

At2302, the UE may measure RSRP associated with a set of resources within a sidelink resource pool. For example, the UE402may measure RSRP associated with a set of resources within a sidelink resource pool1302. In some aspects,2302may be performed by the sensing component2442ofFIG.24.

At2304, the UE may select a first subset of resources associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources. For example, the UE402may select a first subset of resources (e.g., including the resource1414) associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources (e.g., including the resource in912). The first subset of resources may be outside a random selection resource set available for one or more random selection UEs. The second subset of resources may be within the random selection resource set. In some aspects,2304may be performed by the sensing component2442ofFIG.24.

At2306, the UE may transmit a sidelink transmission using the first subset of resources or the second subset of resources. For example, the UE402may transmit a sidelink transmission using the first subset of resources (e.g., including the resource1414) or the second subset of resources (e.g., including the resource in912). In some aspects,2306may be performed by the sidelink component2444ofFIG.24.

FIG.24is a diagram2400illustrating an example of a hardware implementation for an apparatus2402. The apparatus2402may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus2402may include a cellular baseband processor2404(also referred to as a modem) coupled to a cellular RF transceiver2422. In some aspects, the apparatus2402may further include one or more subscriber identity modules (SIM) cards2420, an application processor2406coupled to a secure digital (SD) card2408and a screen2410, a Bluetooth module2412, a wireless local area network (WLAN) module2414, a Global Positioning System (GPS) module2416, or a power supply2418. The cellular baseband processor2404communicates through the cellular RF transceiver2422with the UE104and/or BS102/180. The cellular baseband processor2404may include a computer-readable medium/memory. The computer-readable medium/memory may be non-transitory. The cellular baseband processor2404is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor2404, causes the cellular baseband processor2404to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor2404when executing software. The cellular baseband processor2404further includes a reception component2430, a communication manager2432, and a transmission component2434. The communication manager2432includes the one or more illustrated components. The components within the communication manager2432may be stored in the computer-readable medium/memory and/or configured as hardware within the cellular baseband processor2404. The cellular baseband processor2404may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359. In one configuration, the apparatus2402may be a modem chip and include the cellular baseband processor2404, and in another configuration, the apparatus2402may be the entire UE (e.g., sec350ofFIG.3) and include the additional modules of the apparatus2402.

The communication manager2432may include a sensing component2442that is configured to measure RSRP associated with a set of resources within a sidelink resource pool and select a first subset of resources associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources, e.g., as described in connection with2302or2304ofFIG.23. The communication manager2432may further include a sidelink component2444that may be configured to transmit a sidelink transmission using the first subset of resources or the second subset of resources, e.g., as described in connection with2306ofFIG.23.

As shown, the apparatus2402may include a variety of components configured for various functions. In one configuration, the apparatus2402, and in particular the cellular baseband processor2404, may include means for measuring RSRP associated with a set of resources within a sidelink resource pool. The cellular baseband processor2404may further include means for selecting a first subset of resources associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources. The first subset of resources may be outside a random selection resource set available for one or more random selection UEs, the second subset of resources may be within the random selection resource set. The cellular baseband processor2404may further include means for transmitting a sidelink transmission using the first subset of resources or the second subset of resources. The means may be one or more of the components of the apparatus2402configured to perform the functions recited by the means. As described supra, the apparatus2402may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the means.

Example aspects provided herein may facilitate avoiding resource collision between random selection and partial/full sensing UEs. By configuring a random selection resource set that may be available for random selection UEs, the random selection UEs may avoid transmitting outside the random selection resource set that may collide with transmissions from partial/full sensing UEs. By configuring the random selection resource set to be also available for the sensing UEs, waste of resources may be avoided when there are no or few random selection UEs in an area.

The following aspects are illustrative only and may be combined with other aspects or teachings described herein, without limitation.Aspect 1 is an apparatus for wireless communication at a UE, including: a memory; and at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to :: select a first sidelink transmission resource for SPS based on a sidelink sensing procedure for UE-to-UE communication, the first sidelink transmission resource being associated with one or more subchannels within one or more slots; initiate a timer based on a timer range, the timer range being based on one or more of a battery level or a mobility associated with the UE; and reselect a second sidelink transmission resource or maintain the first sidelink transmission resource for the UE-to-UE communication upon expiration of the timer.Aspect 2 is the apparatus of aspect 1, where the timer range is associated with a maximum value and a minimum value, the maximum value or the minimum value being negatively correlated with at least one of the mobility or the battery level associated with the UE.Aspect 3 is the apparatus of any of aspects 1-2, where the at least one processor is further configured to: change the minimum value or the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold.Aspect 4 is the apparatus of any of aspects 1-3, where the at least one processor is further configured to decrease the timer upon transmitting a packet using the first sidelink transmission resource.Aspect 5 is the apparatus of any of aspects 1-4, where the at least one processor is further configured to: receive, from each of one or more UEs, an indication of a mobility associated with the UE, where the timer range is further based on the mobility for each of the one or more UEs, and where the timer range is associated with a maximum value and a minimum value, the maximum value or the minimum value being negatively correlated with the one or more mobility associated with the one or more UEs.Aspect 6 is the apparatus of any of aspects 1-5, where the at least one processor is further configured to: determine, upon expiration of the timer, whether to reselect the second sidelink transmission resource or maintain the first sidelink transmission resource based on a probability being within a probability range.Aspect 7 is the apparatus of any of aspects 1-6, where the at least one processor is further configured to: receive, from each of one or more UEs, an indication of a mobility associated with the UE, where the probability range is further based on the mobility for each of the one or more UEs.Aspect 8 is the apparatus of any of aspects 1-7, where a maximum value associated with the probability range is negatively correlated with at least one of the mobility or the battery level associated with the UE.Aspect 9 is the apparatus of any of aspects 1-8, where the at least one processor is further configured to: change the maximum value based on the mobility being less than a mobility threshold or the battery level being less than a battery threshold.Aspect 10 is the apparatus of any of aspects 1-9, where to change the maximum value, the at least one processor is further configured to: change the maximum value to be greater than 0.8.Aspect 11 is the apparatus of any of aspects 1-10, where the timer range or the probability range is further based on one or more of: a system channel loading congestion level, a total number of resource associated with the first sidelink transmission resource, or a priority of the UE-to-UE communication.Aspect 12 is the apparatus of any of aspects 1-11, where the at least one processor is further configured to: receive, from a base station via RRC, a configuration for the probability range or the timer range.Aspect 13 is the apparatus of any of aspects 1-12, where a SCI-based pre-emption associated with the first sidelink transmission resource or the second sidelink transmission resource is disabled for the UE.Aspect 14 is the apparatus of any of aspects 1-13, further including a transceiver or an antenna coupled to the at least one processor.Aspect 15 is a method of wireless communication for implementing any of aspects 1 to 14.Aspect 16 is an apparatus for wireless communication including means for implementing any of aspects 1 to 14.Aspect 17 is a non-transitory computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement any of aspects 1 to 14.Aspect 18 is an apparatus for wireless communication at a UE, including: a memory; and at least one processor coupled to the memory and configured to: select randomly a resource in a random selection resource set including one or more subchannels within one or more slots, the random selection resource set being within a sidelink resource pool for UE-to-UE communication and being available for a sidelink sensing procedure for the UE-to-UE communication; and transmit a sidelink transmission in the resource.Aspect 19 is the apparatus of aspect 18, where the at least one processor is further configured to: select randomly a subsequent resource in the random selection resource set for one or more subsequent sidelink transmissions.Aspect 20 is the apparatus of aspects 18-19, where the sidelink transmission is an initial transmission, and where the at least one processor is further configured to: select randomly a subsequent resource in the sidelink resource pool for one or more subsequent sidelink retransmissions associated with the initial transmission.Aspect 21 is the apparatus of any of aspects 18-20, where the sidelink transmission is an initial transmission, where the at least one processor is further configured to: measure RSRP associated with a set of resources within the sidelink resource pool within a sensing time window; and select a subsequent resource from a subset of resources associated with an RSRP below a threshold within the set of resources for one or more subsequent sidelink retransmissions associated with the initial transmission.Aspect 22 is the apparatus of any of aspects 18-21, where the random selection resource set is periodic, and where the at least one processor is further configured to: reserve a set of periodic resources including the resource by transmitting a first stage SCI.Aspect 23 is the apparatus of any of aspects 18-22, where the at least one processor is further configured to: transmit an indication indicating whether the UE will transmit in a second resource of the set of periodic resources.Aspect 24 is the apparatus of any of aspects 18-23, where the at least one processor is further configured to: receive, from a base station, a periodicity associated with the random selection resource set.Aspect 25 is the apparatus of any of aspects 18-24, where a periodicity associated with the random selection resource set is negatively correlated with a total number of random selection UEs within an area or a CBR associated with the random selection resource set.Aspect 26 is the apparatus of any of aspects 18-25, where a number of resources associated with the random selection resource set is positively correlated with a total number of random selection UEs within an area or a CBR associated with the random selection resource set.Aspect 27 is the apparatus of any of aspects 18-26, further including a transceiver or an antenna coupled to the at least one processor.Aspect 28 is an apparatus for wireless communication at a UE, including: a memory; and at least one processor coupled to the memory and configured to: measure RSRP associated with a set of resources within a sidelink resource pool; select a first subset of resources associated with a first RSRP above a first threshold within the set of resources or select a second subset of resources associated with a second RSRP above a second threshold within the set of resources, the first subset of resources being outside a random selection resource set available for one or more random selection UEs, the second subset of resources being within the random selection resource set; and transmit a sidelink transmission using the first subset of resources or the second subset of resources.Aspect 29 is the apparatus of aspect 28, further including a transceiver or an antenna coupled to the at least one processor.Aspect 30 is a method of wireless communication for implementing any of aspects 1 to 29.Aspect 31 is an apparatus for wireless communication including means for implementing any of aspects 1 to 29.Aspect 32 is a non-transitory computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement any of aspects 1 to 29.