Patent Description:
Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for user equipment (UE) autonomous resource selection for physical sidelink control channels (PSCCHs).

Document <CIT> discloses various aspects that would allow for Vehicle to Everything (V2X) or peer-to-peer (P2P) or sidelink (SL) communications. In an embodiment, a communication device may include: a memory for storing computer-readable instructions; and processing circuitry, configured to process the instructions stored in the memory to: obtain a first path loss between the communication device and a base station, wherein the communication device is coupled to the base station; calculate a second path loss based on one or more sidelink reference signal received power (S-RSRP) indicators received by the communication device, wherein the S-RSRP indicators are received from one or more communication devices within a communication range of the communication device; and determine a transmit (Tx) power of the communication device based on the first path loss and the second path loss.

The invention is defined in independent claims. Dependent claims concern particular embodiments of the invention.

After considering this discussion, and particularly after reading the section entitled "Detailed Description" one will understand how the features of this disclosure provide advantages that include improved user equipment (UE) autonomous resource selection for physical sidelink control channels (PSCCHs).

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a UE. The method generally includes performing autonomous sidelink resource selection. The autonomous sidelink resource selection includes excluding one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. The autonomous sidelink resource selection includes determining an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set. The autonomous sidelink resource selection includes excluding, from the second resource set, one or more resources associated with one or more PSCCHs without excluding one or more resources associated with one or more physical sidelink shared channels (PSSCHs) associated with the one or more PSCCHs to form a third resource set comprising the non-excluded resources from the second resource set. The autonomous sidelink resource selection includes randomly selecting one or more resources for a PSCCH transmission from the third resource set. The method generally includes sending the PSCCH transmission using the randomly selected one or more resources.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus generally includes at least one processor; and a memory coupled to the at least one processor. The memory generally includes code executable by the at least one processor to cause the apparatus to perform autonomous sidelink resource selection. The autonomous sidelink resource selection includes excluding one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. The autonomous sidelink resource selection includes determining an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set. The autonomous sidelink resource selection includes excluding, from the second resource set, one or more resources associated with one or more PSCCHs without excluding one or more resources associated with one or more PSSCHs associated with the one or more PSCCHs to form a third resource set. The autonomous sidelink resource selection includes randomly selecting one or more resources for a PSCCH transmission from the third resource set. The memory generally includes code executable by the at least one processor to cause the apparatus to send the PSCCH transmission using the randomly selected one or more resources.

Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus generally includes means for performing autonomous sidelink resource selection. The means for performing autonomous sidelink resource selection includes means for excluding one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. The means for performing autonomous sidelink resource selection includes means for determining an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set. The means for performing autonomous sidelink resource selection includes means for excluding, from the second resource set, one or more resources associated with one or more PSCCHs without excluding one or more resources associated with one or more PSSCHs associated with the one or more PSCCHs to form a third resource set. The means for performing autonomous sidelink resource selection includes means for randomly selecting one or more resources for a PSCCH transmission from the third resource set. The apparatus generally includes means for sending the PSCCH transmission using the randomly selected one or more resources.

Certain aspects of the subject matter described in this disclosure can be implemented in a computer readable medium storing computer executable code thereon for wireless communications. The computer readable medium generally includes code for performing autonomous sidelink resource selection. The code for performing an autonomous sidelink resource selection includes code for excluding one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. The code for performing autonomous sidelink resource selection includes code for determining an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set. The code for performing autonomous sidelink resource selection includes code for excluding, from the second resource set, one or more resources associated with one or more PSCCHs without excluding one or more resources associated with one or more PSSCHs associated with the one or more PSCCHs to form a third resource set. The code for performing autonomous sidelink resource selection includes code for randomly selecting one or more resources for a PSCCH transmission from the third resource set. The computer readable medium generally includes code for sending the PSCCH transmission using the randomly selected one or more resources.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for abstaining from selecting physical sidelink control channel (PSCCH) resources in user equipment (UE) autonomous resource selection.

In cellular vehicle-to-anything (C-V2X) systems, user equipment (UE), such as vehicular UEs, may directly communicate with each other using time-frequency resources autonomously selected by the UE. However, the autonomous selection of resources can cause problems when two UEs select the same resources, thereby causing packet collisions or packet overlaps.

Aspects of the present disclosure may help with the autonomous resource selection process. In some examples, a UE may exclude additional PSCCH resources during autonomous resource selection, and can reduce the likelihood of its PSCCH transmission from colliding with another transmission. In some aspects, the UE may adjust a modulation and coding scheme (MCS) and/or a number of resources selected for transmission to further reduce collisions and overlaps with another transmission.

The following description provides examples of abstaining from selecting PSCCH resources during UE autonomous resource selection in communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims.

The techniques described herein may be used for various wireless networks and radio technologies. While aspects may be described herein using terminology commonly associated with <NUM>, <NUM>, and/or new radio (e.g., <NUM> NR) wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

NR access may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth, millimeter wave mmW, massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC).

NR supports beamforming and beam direction may be dynamically configured.

As shown in <FIG>, the wireless communication network <NUM> may be in communication with a core network <NUM>. The core network <NUM> may in communication with one or more base station (BSs) 110a-z (each also individually referred to herein as BS <NUM> or collectively as BSs <NUM>) and/or user equipment (UE) 120a-y (each also individually referred to herein as UE <NUM> or collectively as UEs <NUM>) in the wireless communication network <NUM> via one or more interfaces.

According to certain aspects, the UEs <NUM> may be configured for abstaining from selecting PSCCH resources in UE autonomous resource selection. As shown in <FIG>, the UE 120a includes a sidelink manager <NUM>. The sidelink manager <NUM> may be configured to perform an autonomous sidelink resource selection. When performing the autonomous sidelink resource selection, the sidelink manager <NUM> may be configured to exclude one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. When performing the autonomous sidelink resource selection, the sidelink manager <NUM> may be configured to determine an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set. When performing the autonomous sidelink resource selection, the sidelink manager <NUM> may be configured to exclude, from the second resource set, one or more resources associated with one or more physical sidelink control channels (PSCCHs) without excluding one or more resources associated with one or more physical sidelink shared channels (PSSCHs) associated with the one or more PSCCHs to form a third resource set. When performing the autonomous sidelink resource selection, the sidelink manager <NUM> may be configured to randomly select one or more resources for a PSCCH transmission from the third resource set. The sidelink manager <NUM> may be configured to send the PSCCH transmission using the randomly selected one or more resources, in accordance with aspects of the present disclosure. A UE 120b may include a sidelink manager <NUM> that may be configured to perform the corresponding operations as sidelink manager <NUM>.

The BSs <NUM> communicate with UEs <NUM> in the wireless communication network <NUM>.

A network controller <NUM> may be in communication with a set of BSs <NUM> and provide coordination and control for these BSs <NUM> (e.g., via a backhaul). In aspects, the network controller <NUM> may be in communication with a core network <NUM> (e.g., a <NUM> Core Network (5GC)), which provides various network functions such as Access and Mobility Management, Session Management, User Plane Function, Policy Control Function, Authentication Server Function, Unified Data Management, Application Function, Network Exposure Function, Network Repository Function, Network Slice Selection Function, etc..

<FIG> illustrates example components of BS 110a and UE 120a (e.g., the wireless communication network <NUM> of <FIG>), which may be used to implement aspects of the present disclosure.

At the BS 110a, a transmit processor <NUM> may receive data from a data source <NUM> and control information from a controller/processor <NUM>. The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. A medium access control (MAC)-control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel (PSSCH).

The processor <NUM> may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor <NUM> may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), PBCH demodulation reference signal (DMRS), and channel state information reference signal (CSI-RS). A transmit (TX) multiple-input multiple-output (MIMO) processor <NUM> may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) in transceivers 232a-232t. Each modulator in transceivers 232a-232t may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Downlink signals from the modulators in transceivers 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120a, the antennas 252a-252r may receive the downlink signals from the BS 110a and/or sidelink signals from the UE 120b and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator in transceivers 254a-254r may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. A MIMO detector <NUM> may obtain received symbols from all the demodulators in transceivers 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor <NUM> may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink <NUM>, and provide decoded control information to a controller/processor <NUM>.

On the uplink and/or sidelink, at UE 120a, a transmit processor <NUM> may receive and process data (e.g., for the physical uplink shared channel (PUSCH) and/or physical sidelink shared channel (PSSCH)) from a data source <NUM> and control information (e.g., for the physical uplink control channel (PUCCH) and/or physical sidelink control channel (PSCCH)) from the controller/processor <NUM>. The symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the modulators in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the BS 110a and/or UE 120b. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas <NUM>, processed by the demodulators in transceivers 232a-232t, detected by a MIMO detector <NUM> if applicable, and further processed by a receive processor <NUM> to obtain decoded data and control information sent by the UE 120a.

Antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE 120a may be used to perform the various techniques and methods described herein. For example, as shown in <FIG>, the controller/processor <NUM> of the UE 120a has a sidelink manager <NUM> that may be configured to abstain from selecting PSCCH resources in UE autonomous resource selection, according to aspects described herein. Although shown at the controller/processor, other components of the UE 120a and BS 110a may be used to perform the operations described herein.

Each subframe may include a variable number of slots (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,. slots) depending on the SCS. Each slot may include a variable number of symbol periods (e.g., <NUM>, <NUM>, or <NUM> symbols) depending on the SCS. A sub-slot structure may refer to a transmit time interval having a duration less than a slot (e.g., <NUM>, <NUM>, or <NUM> symbols). Each symbol in a slot may be configured for a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched.

In NR, a synchronization signal block (SSB) is transmitted. In certain aspects, SSBs may be transmitted in a burst where each SSB in the burst corresponds to a different beam direction for UE-side beam management (e.g., including beam selection and/or beam refinement). The SSB includes a PSS, a SSS, and a two symbol PBCH. The SSB can be transmitted in a fixed slot location, such as the symbols <NUM>-<NUM> as shown in <FIG>. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SSBs may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), other system information (OSI) can be transmitted on a PDSCH in certain subframes. The SSB can be transmitted up to sixty-four times, for example, with up to sixty-four different beam directions for mmWave. The multiple transmissions of the SSB are referred to as a SS burst set. SSBs in an SS burst set may be transmitted in the same frequency region, while SSBs in different SS bursts sets can be transmitted at different frequency regions.

In some examples, the communication between the UEs <NUM> and BSs <NUM> is referred to as the access link. The access link may be provided via a Uu interface. Communication between devices may be referred as the sidelink. Sidelink communications may be provided via a PC5 interface.

In some examples, two or more subordinate entities (e.g., UEs <NUM>) may communicate with each other using sidelink signals. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE 120a) to another subordinate entity (e.g., another UE <NUM>) without relaying that communication through the scheduling entity (e.g., UE <NUM> or BS <NUM>), even though the scheduling entity may be utilized for scheduling and/or control purposes. One example of sidelink communication is PC5, for example, as used in V2V, LTE, and/or NR.

Various sidelink channels may be used for sidelink communications, including a physical sidelink discovery channel (PSDCH), a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH). The PSDCH may carry discovery expressions that enable proximal devices to discover each other. The PSCCH may carry control signaling such as sidelink resource configurations and other parameters used for data transmissions, and the PSSCH may carry the data transmissions. The PSFCH may carry feedback such as CSI related to a sidelink channel quality.

<FIG> and <FIG> show diagrammatic representations of example vehicle-to-everything (V2X) systems, in accordance with some aspects of the present disclosure. For example, the vehicles shown in <FIG> and <FIG> may communicate via sidelink channels and may relay sidelink transmissions as described herein.

The V2X systems, provided in <FIG> and <FIG> provide two complementary transmission modes. A first transmission mode (also referred to as mode <NUM>), shown by way of example in <FIG>, involves direct communications (for example, also referred to as side link communications) between participants in proximity to one another in a local area. A second transmission mode (also referred to as mode <NUM>), shown by way of example in <FIG>, involves network communications through a network, which may be implemented over a Uu interface (for example, a wireless communication interface between a radio access network (RAN) and a UE).

Referring to <FIG>, a V2X system <NUM> (for example, including vehicle to vehicle (V2V) communications) is illustrated with two vehicles <NUM>, <NUM>. The first transmission mode allows for direct communication between different participants in a given geographic location. As illustrated, a vehicle can have a wireless communication link <NUM> with an individual (vehicle-to-person (V2P)) (for example, via a UE) through a PC5 interface. Communications between the vehicles <NUM> and <NUM> may also occur through a PC5 interface <NUM>. In a like manner, communication may occur from a vehicle <NUM> to other highway components (for example, highway component <NUM>), such as a traffic signal or sign (vehicle-to-infrastructure (V2I)) through a PC5 interface <NUM>. With respect to each communication link illustrated in <FIG>, two-way communication may take place between elements, therefore each element may be a transmitter and a receiver of information. The V2X system <NUM> may be a self-managed system implemented without assistance from a network entity. A self-managed system may enable improved spectral efficiency, reduced cost, and increased reliability as network service interruptions do not occur during handover operations for moving vehicles. The V2X system may be configured to operate in a licensed or unlicensed spectrum, thus any vehicle with an equipped system may access a common frequency and share information. Such harmonized/common spectrum operations allow for safe and reliable operation.

<FIG> shows a V2X system <NUM> for communication between a vehicle <NUM> and a vehicle <NUM> through a network entity <NUM>. These network communications may occur through discrete nodes, such as a BS (e.g., the BS 110a), that sends and receives information to and from (for example, relays information between) vehicles <NUM>, <NUM>. The network communications through vehicle to network (V2N) links <NUM> and <NUM> may be used, for example, for long range communications between vehicles, such as for communicating the presence of a car accident a distance ahead along a road or highway. Other types of communications may be sent by the wireless node to vehicles, such as traffic flow conditions, road hazard warnings, environmental/weather reports, and service station availability, among other examples. Such data can be obtained from cloud-based sharing services.

Roadside units (RSUs) may be utilized. An RSU may be used for V2I communications. In some examples, an RSU may act as a forwarding node to extend coverage for a UE. In some examples, an RSU may be co-located with a BS or may be standalone. RSUs can have different classifications. For example, RSUs can be classified into UE-type RSUs and Micro NodeB-type RSUs. Micro NB-type RSUs have similar functionality as the Macro eNB/gNB. The Micro NB-type RSUs can utilize the Uu interface. UE-type RSUs can be used for meeting tight quality-of-service (QoS) requirements by minimizing collisions and improving reliability. UE-type RSUs may use centralized resource allocation mechanisms to allow for efficient resource utilization. Critical information (e.g., such as traffic conditions, weather conditions, congestion statistics, sensor data, etc.) can be broadcast to UEs in the coverage area. Relays can rebroadcasts critical information received from some UEs. UE-type RSUs may be a reliable synchronization source.

Sidelink communications can include cellular V2X (C-V2X) communications. A C-V2X system may operate in various modes. <FIG> is an example table <NUM> of PSCCH transmission parameters (e.g., as defined in TS <NUM> Table <NUM>-<NUM>) for various sidelink modes.

An example C-V2X mode, referred to as Mode <NUM>, may be used when the UE is in an in-coverage area. In the C-V2X Mode <NUM>, the network may control allocation of resources for the sidelink UEs. In another example C-V2X mode, referred to as Mode <NUM>, the sidelink UEs may autonomously select resources (e.g., resource blocks (RBs)) used for transmissions. The resources may be semi-persistent scheduling (SPS) resources. In some examples, the sidelink UEs can autonomously select resources based on an SPS algorithm. The SPS algorithm may be configured, hardcoded, or preconfigured at the UE. For example, the SPS algorithm may be based on an SPS algorithm defined in the 3GPP technical standards.

In some systems, a UE may select resources to transmit using a sensing mechanism. By sensing available and unavailable resources, the UE can select and transmit on vacant resources, which may reduce or prevent collisions. The sensing may involve power estimation (e.g., resource signal strength indicator (RSSI) measurements). The power estimation may exclude unmeasured subframes (e.g. due to previous transmissions). The resource selection may exclude resources based on expected conflict with other UE's transmissions. Hidden UEs; however, may be unaware of each other and, therefore, unable to exclude each other resources. Thus, transmissions by these UEs may collide on neighboring UEs.

In some cases, a "hidden terminal" scenario may occur due to the dynamically changing environment. For example, when the sidelink UE selects resources for transmissions (e.g., in the Mode <NUM>), some other UEs (e.g., vehicles) may be hidden (e.g., undetected), such as when a channel sensing is performed. Thus, two (or more) UEs may (e.g., autonomously) select the same resources. Hidden terminal scenarios (leading to packet collision) may occur when UEs have overlapping coverage area while assigning RBs for transmission.

<FIG> illustrates an example congestion scenario. The UE A and UE C cannot sense each other's presence, for example, because these UEs are outside the coverage range of each other. As shown in <FIG>, the physical distance, d, between UE A and UE C is at least rA + rC, where rA is the radius of UEs A's coverage and rC is the radius of UE C's coverage. UE A does not know about the existence of UE C (the "hidden node"), and similarly, UE C does not know about the existence of UE A. Because UE A and UE C do not know about the other, both UEs may allocate/select the same time-frequency resources (some or all) (e.g., overlapping RBs) for transmission. In this case, UEs in the common area of UE A and UE C (A ∩ C), such as UE B shown in <FIG>) cannot decode the data transmitted from either UE A or UE C using the allocated resources, due to the packet collision.

Collisions and overlaps may be seen in congested scenarios. As used herein, overlap occurs when two or more UEs transmit control (e.g., PSCCH) and data channels (e.g., PSSCH) on the same resources and collision occurs when two or more UEs transmit control channels (e.g., PSCCHs) on the same resources.

<FIG> illustrates an example collision scenario and <FIG> illustrates an example overlapping scenario. During a collision, as shown in <FIG>, the PSCCH transmissions from UE1 and UE2 are transmitted on the same resources. During an overlap, as shown in <FIG>, the PSSCH and PSCCH transmissions from UE <NUM> and UE2, respectively, are transmitted using the same resources.

For both collisions and overlaps, if the UE1 and UE2 transmit PSCCH and PSSCH transmissions, other UEs may not detect the PSCCH (e.g., with sidelink control SCI). Although transmissions from two UEs are shown in <FIG>, the system may involve sidelink transmissions from any number of UEs.

SCI may be carried on the PSCCH and provide information regarding sidelink transmission, such as a scheduled PSSCH transmission. Thus, a UE can determine information about potential overlap or collisions from the information carried in the SCI. With SPS transmissions, an SPS transmission may be for a transmission period (e.g., <NUM>, <NUM>, <NUM>, <NUM>,. , <NUM> subframes). Thus, a UE can determine information about potential overlap or collisions from the periodicity of the SPS transmissions. Hybrid automatic repeat request (HARQ) transmissions may point to each other. For example, redundancy versions (e.g., RV<NUM>, RV<NUM>) may be associated (e.g., there may be a <NUM>, <NUM>,. <NUM> subframe gaps between redundancy versions). Thus, information regarding one RV may be determined from information about another RV. <FIG> illustrates an example SCI RV pair.

In C-V2X Mode <NUM>, vehicles autonomously select their resources without the assistance of the cellular infrastructure. Vehicles may use a sensing-based SPS scheduling scheme. A vehicle may reserve the selected resource(s) for a random number of consecutive packets. The number of packet may depend on the number of packets transmitted per second, or inversely on the packet transmission interval. When a vehicle reserves new resources, the vehicle may randomly selects a reselection counter. After each transmission, the reselection counter is decremented by one. When the reselection counter is equal to zero, new resources are selected and reserved. The new resources may be selected and reserved according to a probability. Each vehicle may include its packet transmission interval and the value of its reselection counter in its SCI. Vehicles can use this information to estimate which resources are free when making their own reservation to reduce packet collisions.

The vehicle may reserve resources from within a selection window. The selection window may be the time window between the time the packet has been generated and a defined maximum latency. Within the selection window, the vehicle may create a list of available resources it could reserve. This list can include all the resources excluding resources that meet certain conditions. For example, the list may exclude resources for which the vehicle has received an SCI from another vehicle in the last N (e.g., a preconfigured number) subframes indicating that the other vehicle will utilize this resource in the selection window or any of its next reselection counter packets. The list may exclude resources for which the vehicle measures an average signal strength (e.g., such as reference signal received power (RSRP) or received signal strength indicator (RSSI)) that is higher than a given threshold. After excluding resources to create the list, the vehicle may determine whether the list contains a threshold amount (e.g., <NUM>%) of all the resources initially identified in the selection window. If the list does not contain the threshold percentage of resources, then the vehicle iterates the list creation until the threshold is met. In each iteration, the vehicle increases the signal strength threshold (e.g., by 3dB). The vehicle then randomly chooses one of the candidate resources in the list of candidate resources, and reserves the randomly selected resource for the next reselection counter transmissions.

The number of resources for the transmission may be derived from any of the following: a number specified by the congestion level (Nlimit), the message size (e.g., protocol data unit (PDU) packet size), and the allowed modulation and coding schemes (MCSs) and physical resource blocks (PRBs). A scheduler (e.g., at the vehicle) may start from a default MCS and/or default subchannel(s) values and search the correct "working point" of resources. For example, a scheduler may adjust the default MCS and/or subchannel values to find either a more robust MCS and a larger number of PRBs or a more efficient MCS and smaller number of PRBs that is suitable for the transmission.

In some cases, when the UE autonomously selects resources, the UE excludes detected resources having a signal strength higher than a given threshold and will not exclude the resources (e.g., subchannels) of detected resources (e.g., detected PSCCH transmissions) having a signal strength and will not exclude the non-detected PSCCH transmissions (e.g., an undetected PSCCH that is indicated by a missed HARQ RVo or by SPS and/or an undetected PSCCH with no indication). Not excluding resources of non-detected PSCCH transmission may lead to congestion (e.g., collisions and/or overlaps. Collisions and/or overlap may also cause measurements assisting link management (e.g. sync-time offset and/or frequency offset) to be missed. In some cases, because of misdetection of the PSCCH, the UEs may misdetect PSSCH transmissions because the sidelink control information points to the corresponding sidelink data transmission.

Congestion can be detrimental to C-V2X communications and can lead to competition (e.g. dedicated short range communication (DSRC)) promotion. Congestion may impact packet error rate (PER) and/or information age (IA).

Accordingly, what is needed are techniques and apparatus for UE autonomous resource selection to may reduce or avoid collisions and/or overlaps.

Aspects of the present disclosure provide techniques for abstaining from (e.g., avoiding or reducing) selecting physical sidelink control channel (PSCCH) resources during user equipment (UE) autonomous sidelink resource selection. Abstaining from selecting PSCCH resources during UE autonomous sidelink resource selection may reduce collisions (e.g., PSCCH on PSCCH allocations) and overlaps (e.g., physical sidelink shared channel (PSSCH) on PSCCH allocations).

Abstaining from selecting PSCCH resources may involve using marked PSCCHs known from sidelink control information (SCI) of a detected redundancy version (RV) to determine which PSCCH resources to abstain from selecting. For example, a UE may receive an initial SCI transmission (e.g., RVo). The initial SCI may point to an SCI retransmission (e.g., RV<NUM>). The UE can also determine SCIs based on a semi-persistent scheduling (SPS) periodicity.

<FIG> is a decision tree diagram of the autonomous resource selection process, in accordance with certain aspects of the present disclosure. The autonomous resource selection process <NUM> may be performed, for example, by a UE (e.g., such as the UE 120a in the wireless communication network <NUM>). The autonomous resource selection process <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>).

In some examples, the UE follows the cellular vehicular to anything (C-V2X) mode <NUM> autonomous reselection described above. The autonomous resource selection process <NUM> may begin at <NUM> by starting with all available transmission resources in a window (e.g., a first resource set including all available transmission resources in the window).

As illustrated, when reducing collisions, the UE excludes resources (e.g., PSCCH resources used for SCI transmission) that above/below a signal strength threshold for the autonomous sidelink resource selection process. At <NUM>, the UE excludes resources above a signal strength threshold, which forms a second resource set of non-excluded resources. For example, the UE may set a signal strength threshold, such as a reference signal received power (RSRP) threshold, and compare signal strength of the resources against the signal strength threshold. Based on the comparison of the signal strength of the resources against the signal strength threshold, the UE may exclude the resources if the resources' signals strength is higher than the signal strength threshold.

The UE may perform the exclusion until the threshold amount (e.g., at least <NUM>%) of the PSCCHs remain. At <NUM>, the UE determines whether the amount of non-excluded resources (e.g., the amount of resources in the second resource set) is greater than a threshold percentage (e.g., <NUM>%) of the total available transmission resources in the window (e.g., the first resource set). If the amount of non-excluded resources is less than the threshold percentage of the amount of all available transmission resources in the window, then at <NUM>, the UE raises the signal strength threshold so that fewer resources are excluded and the amount of non-excluded resources is more likely to above the threshold percentage. Accordingly, the UE repeats the steps of excluding resources above the signal strength threshold (at <NUM>) and determining whether the amount of non-excluded resources is greater than the threshold percentage (at <NUM>). As illustrated, the UE may perform resource exclusion in the autonomous resource selection by adjusting (e.g., raising) the signal strength threshold and excluding both PSCCH and corresponding PSSCH resources (e.g., the PSSCH resources indicated by SCI in the PSCCH) until the amount of resources (e.g., non-excluded resources) in the list is equal to or greater than the threshold percentage (e.g., <NUM>%) of the initially identified resources in the transmission window.

If the amount of non-excluded resources (e.g., the amount of resources in the second resource set) is greater than the threshold percentage of the amount of total available transmission resources in the window (i.e., the first resource set), then at <NUM>, the UE may set a lower signal strength threshold. In some aspects, the UE can reset the signal strength threshold to an initial or default value if the UE had raised the threshold during the resource exclusion at <NUM>.

After setting the lower signal strength threshold, at <NUM>, the UE excludes only PSCCH resources above the signal strength threshold. This exclusion forms a third resource set, which includes non-excluded resources from the second resource set. In some aspects, the UE excludes only the PSCCH resources and not the corresponding PSSCH resources. Thus, the UE can exclude more PSCCHs and reduce the likelihood of collisions. The exclusion process may include non-physical parameters, such as priority or a corresponding RV to a missed initial transmission (e.g., an RV2 of a missed RVo).

At <NUM>, the UE determines whether the amount of non-excluded resources after the most recent round of exclusions (i.e., the amount of non-excluded resources in the third resource set) is greater than the threshold percentage (e.g., <NUM>%) of the amount of all available transmission resources in the window. If less than the threshold percentage of resources remain, then at <NUM>, the UE increases (e.g., raises) the signal strength threshold by a predefined amount (e.g., <NUM> dB) and repeats the exclusion (at <NUM>) using the increased signal strength threshold and re-determines (at <NUM>) whether the amount of non-excluded resources after exclusion is still less than the threshold percentage. The UE iterates this process until the amount of non-excluded resources reaches the threshold percentage.

If the UE determines that the amount of non-excluded resources after the most recent round of exclusions (i.e., the amount of non-excluded resources in the third resource set) is greater than the threshold percentage (e.g., <NUM>%) of the amount of all available transmission resources in the window, at <NUM> the UE randomly selects resources for PSCCH transmission from the non-excluded PSCCH resources (i.e., the third resource set). In some aspects, the UE may allocate the resources using a default number of resources (e.g., subchannels) and/or a default modulation and coding scheme (MCS) for the PSCCH transmission.

According to certain aspects, to reduce overlaps, the UE may adjust a default MCS and/or a default number of resources to avoid selecting a resource with a "marked" PSCCH transmission. By adjusting the default MCS and default number of resources, the UE can tailor the random resource selection so that when the UE randomly selects resources, the resources the UE selects avoid overlapping with shared channel transmissions.

When adjusting the default MCS and/or the default number of resources, the UE may increase the default MCS and correspondingly decrease the default number of subchannels or decrease the default MCS and correspondingly increase the default number of subchannels. In some examples, the UE may search for a more robust MCS with an increased number of subchannels by adding subchannels not containing marked PSCCHs. Increasing subchannels may involve reducing a PSCCH index or adding another PSSCH subchannel. In some aspects, the UE may search for a less robust MCS with decreased number of subchannels. In such aspects, the UE removes subchannels containing marked PSCCH, which may involve increasing PSCCH index or reducing the last PSCCH subchannel.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a UE (e.g., such as the UE 120a in the wireless communication network <NUM>). The operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> begins, at <NUM>, by performing autonomous sidelink resource selection. In the autonomous sidelink resource selection, at <NUM>, the UE excludes one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set. At <NUM>, the UE determines that an amount of resources in the second resource set are at or above a threshold percentage of an amount of resources in the first resource set. At <NUM>, the UE excludes, from the second resource set, one or more resources associated with one or more PSCCHs without excluding one or more resources associated with one or more PSSCHs associated with the one or more PSCCH to form a third resources set. At <NUM>, the UE randomly selects one or more resources for a PSCCH transmission from the third resource set.

In some aspects, excluding one or more resources associated with the one or more PSCCHs from the second resource set includes excluding one or more resources associated with one or more PSCCHs with the highest signal strength. In some aspects, excluding one or more resources associated with the one or more PSCCHs from the second resource set includes excluding, from the second resource set, one or more resources associated with one or more PSCCHs at a signal strength above a second signal strength threshold to form the third resource set, and determining whether an amount of resources in the third resource set are at or above the threshold percentage of the amount of resources in the first resource set. In further aspects, when the amount of resources in the third resource set is below the threshold percentage of the amount of resources in the first resource set, iteratively, performing until the resources in the third resource set are at or above the threshold percentage of the amount of resources in the first resource set, the UE may increase the second signal strength threshold to a third signal strength threshold. In such further aspects, the UE may further exclude, from the second resource set, one or more resources associated with one or more PSCCHs at a signal strength above the third signal strength threshold to form the third resource set; and re-determine whether the amount of resources in the third resource set are at or above the threshold percentage of the amount of resources in the first resource set.

In some aspects, randomly select the resources from the PSCCH transmission from the third resource set is based on the determining the amount of resources in the third resource set is at or above the threshold percentage of the amount of resources in the first resource set.

At <NUM>, the UE sends the PSCCH transmission using the randomly selected one or more resources.

In some aspects, at <NUM>, the UE may identify the one or more PSCCHs as one or more PSCCH retransmissions based on one or more sidelink control information (SCI) in one or more initial PSCCH transmissions. The UE may identify the one or more PSCCHs based on semi-persistent scheduling (SPS). The autonomous sidelink resource selection may comprise CV2X mode <NUM> autonomous resource selection. In some aspects, the first resource set may include resources within a selected transmission window. In some aspects, excluding resources from the first resource set, associated with transmissions at a signal strength above the first signal strength threshold to form the second resource set further includes excluding resources indicated in SCI within a previous number of subframes. In some aspects, the threshold percentage may be twenty percent.

In some aspects, the UE may adjust a default modulation and coding scheme (MCS) and a default number of resources for transmitting a message to avoid selecting a resource with a PSCCH transmission, and when the UE randomly selects resources for the PSCCH transmission from the third resource set, the UE randomly selects the adjust number of resources. In further aspects, When the UE adjusts the default MCS and the default number of resources for transmitting a message to avoid selecting a resource with a PSCCH transmission, the UE increases the default MCS and decreases a default number of subchannels to allow selection of subchannels from the second resource set that avoids a subchannel with a PSCCH transmission. In some aspects, when the UE adjusts the default MCS and the default number of resources for transmitting a message to avoid selecting resources with a PSCCH transmission, the UE decreases a default MCS and increases a default number of subchannels to allow selection of subchannels from the non-excluded resources from the second resource set that avoids a non-excluded subchannel with a PSCCH transmission.

<FIG> is a call flow diagram illustrating example signaling <NUM> between a UE1 and a UE2, in accordance with certain aspects of the present disclosure. At <NUM>, the UE1 may receive from UE2 a RVo PSCCH transmission which may provide SCI and information about the corresponding PSSCH. At <NUM>, the UE may perform autonomous sidelink resource selection, in which the UE abstains from selecting PSCCH resources. Once the UE autonomously selects its resources, at <NUM>, the UE1 may send a PSCCH transmission using the autonomously selected resources.

In some aspects, when the UE excludes resources at <NUM>, the UE excludes resources associated with transmissions based on certain signal strength threshold (e.g., RSRP threshold). For example, the UE may excludes resources associated with transmissions at a signal strength above a first signal strength threshold from the total resources to form a first non-excluded resource set. The UE may then perform additional exclusions based on a threshold percentage of the total resources (e.g., <NUM>% of the total resources). For example, the UE may exclude resources associated with one or more control channels and leave the corresponding shared channels included in the resource set. By excluding resources associated with control channels at <NUM>, the UE decreases the likelihood of collisions when randomly selecting resources for the UE's PSCCH transmission.

When excluding resources associated with control channels at <NUM>, the UE may exclude control channels with the highest signal strength or above a second signal strength threshold. After each exclusion, if the non-excluded resources are below the threshold percentage (e.g., <NUM>% of the total resources), then the UE may increase the second signal threshold used for excluding control channels so that the non-excluded resources is at or above the threshold percentage. Accordingly, some resources that may have been excluded prior to increasing the second signal threshold would be re-included in the non-excluded resources from which the UE randomly selects.

The communications device <NUM> includes a processing system <NUM> coupled to a transceiver <NUM> (e.g., a transmitter and/or a receiver).

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein for abstaining from selecting PSCCH resources during UE autonomous resource selection. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for performing autonomous sidelink resource selection; and code <NUM> for sending the PSCCH transmission using the randomly selected one or more resources. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for identifying the one or more PSCCHs as one or more PSCCH retransmissions based on one or more SCI in the one or more initial PSCCH transmissions. In certain aspects, the processor <NUM> has circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>. The processor <NUM> includes circuitry <NUM> for performing autonomous sidelink resource selection; and circuitry <NUM> for sending the PSCCH transmission using the randomly selected one or more resources. In certain aspects, the processor <NUM> includes circuitry <NUM> for identifying the one or more PSCCHs as one or more PSCCH retransmissions based on one or more SCI in the one or more initial PSCCH transmissions.

For example, means for transmitting (or means for outputting for transmission) may include a transmitter unit <NUM> and/or antenna(s) <NUM> of the UE 120a illustrated in <FIG> and/or circuitry <NUM> of the communication device <NUM> in <FIG>. Means for receiving (or means for obtaining) may include a receiver and/or antenna(s) <NUM> of the UE 120a illustrated in <FIG>. Means for communicating may include a transmitter, a receiver or both. Means for generating, means for performing, means for determining, means for taking action, means for determining, means for coordinating may include a processing system, which may include one or more processors, such as the receive processor <NUM>, the transmit processor <NUM>, the TX MIMO processor <NUM>, and/or the controller/processor <NUM> of the UE 120a illustrated in <FIG> and/or the processing system <NUM> of the communication device <NUM> in <FIG>.

Implementation examples are described in the following numbered clauses:.

The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, a digital signal processor (DSP), an application specific integrated circuit (ASIC), or a processor (e.g., a general purpose or specifically programmed processor).

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a DSP, an ASIC, a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

Claim 1:
A method for wireless communications, comprising:
performing (<NUM>) autonomous sidelink resource selection including:
excluding (<NUM>) one or more resources, from a first resource set, associated with transmissions at a signal strength above a first signal strength threshold to form a second resource set;
determining (<NUM>) an amount of resources in the second resource set is at or above a threshold percentage of an amount of resources in the first resource set;
excluding (<NUM>), from the second resource set, one or more resources associated with one or more physical sidelink control channels, PSCCHs,
without excluding one or more resources associated with one or more physical sidelink shared channels, PSSCHs, associated with the one or more PSCCHs to form a third resource set; and
randomly selecting (<NUM>) one or more resources for a PSCCH transmission from the third resource set; and
sending (<NUM>) the PSCCH transmission using the randomly selected one or more resources.