RESOURCE RESERVATION FORWARDING PROCEDURE IN NEW RADIO SIDELINK

A first user equipment (UE) receives, via first sidelink resources from a second UE, a reservation message that includes an indication of second sidelink resources via which the first UE will subsequently receive a data packet. The first UE may at least one of: determine if the first UE is an intended recipient of the data packet, or compare a reference signal received power (RSRP) value of the reservation message to a threshold value. The first UE may transmit a first reservation forwarding message, via one or more third sidelink resources, including at least the indication of the second sidelink resources to at least a third UE in response to at least one of: determining that the first UE is the intended recipient of the data packet, or determining that the RSRP value is less than the threshold value. The first UE subsequently receives the data packet.

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication networks, and more particularly, to resource reservation forwarding procedures in New Radio sidelink.

BACKGROUND

In sidelink communication networks, a user equipment (UE) may autonomously select one or more resources and then transmit a sidelink transmission on those resources. In some examples, the UE may monitor a control portion of other sidelink transmissions to identify available resources on which the UE may schedule the sidelink transmission. In some examples, the control portion may include a resource reservation message including an indication of an initial resource selected for an initial sidelink transmission and one or more retransmission resources selected for one or more retransmissions of the sidelink transmission. The resource reservation message may thus indicate to other UEs the resources to be utilized by the transmitting UE for the one or more retransmissions. Usage of the resource reservation message may allow other UEs to avoid using the selected one or more retransmission resources and thereby reduce interference during the retransmission. Usage of the resource reservation message may improve the likelihood of success of the retransmission.

BRIEF SUMMARY OF SOME EXAMPLES

A first user equipment (UE) is described. The first UE includes a transceiver for wireless communication, a memory, and a processor coupled to the transceiver and the memory. The processor and the memory are configured to: receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message includes a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The processor and the memory are further configured to transmit a first reservation forwarding message including at least the first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources, and receive a transmission of the first data packet from the second UE via the one or more second sidelink resources.

A method of wireless communication at a first user equipment (UE) is described. The method includes receiving a first reservation message from a second UE via one or more first sidelink resources. The first reservation message includes a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The method further includes transmitting a first reservation forwarding message including at least the first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources, and receiving a transmission of the first data packet from the second UE via the one or more second sidelink resources.

These and other aspects will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and examples will become apparent to those of ordinary skill in the art upon reviewing the following description of specific exemplary aspects in conjunction with the accompanying figures. While features may be discussed relative to certain examples and figures below, all examples can include one or more of the advantageous features discussed herein. In other words, while one or more examples may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various examples discussed herein. Similarly, while examples may be discussed below as device, system, or method examples, it should be understood that such examples can be implemented in various devices, systems, and methods.

DETAILED DESCRIPTION

In some examples, a transmitting UE may transmit a sidelink transmission including a reservation message. The reservation message may include an indication of one or more resources selected and reserved for an initial sidelink transmission of a data packet and one or more retransmission resources selected and reserved for one or more retransmissions of the data packet.

In various aspects of the disclosure, when a receiving UE receives a reservation message the receiving UE may forward the reservation message from the transmitting UE to other UEs, thereby extending the reservation range. For example, the receiving UE may transmit a reservation forwarding message including the reservation message to one or more other UEs (remote UEs). The reservation forwarding message may be transmitted via, for example, a radio resource control (RRC) message or a medium access control (MAC) control element (MAC-CE). A remote UE receiving the reservation forwarding message may abstain from using the resources indicated in the reservation forwarding message for other sidelink transmissions.

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now toFIG. 1, as an illustrative example without limitation, a schematic illustration of a radio access network100is provided. The RAN100may implement any suitable wireless communication technology or technologies to provide radio access. As one example, the RAN100may operate according to 3rd Generation Partnership Project (3GPP) New Radio (NR) specifications, often referred to as 5G. As another example, the RAN100may operate under a hybrid of 5G NR and Evolved Universal Terrestrial Radio Access Network (eUTRAN) standards, often referred to as LTE. The 3GPP refers to this hybrid RAN as a next-generation RAN, or NG-RAN. Of course, many other examples may be utilized within the scope of the present disclosure.

In general, a respective base station (BS) serves each cell. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. A BS may also be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB), a transmission and reception point (TRP), or some other suitable terminology. In some examples, a base station may include two or more TRPs that may be collocated or non-collocated. Each TRP may communicate on the same or different carrier frequency within the same or different frequency band. In examples where the RAN100operates according to both the LTE and 5G NR standards, one of the base stations may be an LTE base station, while another base station may be a 5G NR base station.

Various base station arrangements can be utilized. For example, inFIG. 1, two base stations110and112are shown in cells102and104; and a third base station114is shown controlling a remote radio head (RRH)116in cell106. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the cells102,104, and106may be referred to as macrocells, as the base stations110,112, and114support cells having a large size. Further, a base station118is shown in the cell108which may overlap with one or more macrocells. In this example, the cell108may be referred to as a small cell (e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc.), as the base station118supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints.

It is to be understood that the radio access network100may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The base stations110,112,114,118provide wireless access points to a core network for any number of mobile apparatuses.

FIG. 1further includes an unmanned aerial vehicle (UAV)120, which may be a drone or quadcopter. The UAV120may be configured to function as a base station, or more specifically as a mobile base station. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station such as the UAV120.

In general, base stations may include a backhaul interface for communication with a backhaul portion (not shown) of the network. The backhaul may provide a link between a base station and a core network (not shown), and in some examples, the backhaul may provide interconnection between the respective base stations. The core network may be a part of a wireless communication system and may be independent of the radio access technology used in the radio access network. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

The RAN100is illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the 3rd Generation Partnership Project (3GPP), but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus that provides a user with access to network services.

Within the RAN100, the cells may include UEs that may be in communication with one or more sectors of each cell. For example, UEs122and124may be in communication with base station110; UEs126and128may be in communication with base station112; UEs130and132may be in communication with base station114by way of RRH116; UE134may be in communication with base station118; and UE136may be in communication with mobile base station120. Here, each base station110,112,114,118, and120may be configured to provide an access point to a core network (not shown) for all the UEs in the respective cells. In some examples, the UAV120(e.g., the quadcopter) can be a mobile network node and may be configured to function as a UE. For example, the UAV120may operate within cell102by communicating with base station110.

Wireless communication between a RAN100and a UE (e.g., UE122or124) may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., base station110) to one or more UEs (e.g., UE122and124) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity (described further below; e.g., base station110). Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE122) to a base station (e.g., base station110) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE122).

For example, DL transmissions may include unicast or broadcast transmissions of control information and/or traffic information (e.g., user data traffic) from a base station (e.g., base station110) to one or more UEs (e.g., UEs122and124), while UL transmissions may include transmissions of control information and/or traffic information originating at a UE (e.g., UE122). In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. A slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1 ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Within the present disclosure, a frame may refer to a predetermined duration (e.g., 10 ms) for wireless transmissions, with each frame consisting of, for example, 10 subframes of 1 ms each. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources (e.g., time-frequency resources) for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs or scheduled entities utilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs). For example, two or more UEs (e.g., UEs138,140, and142) may communicate with each other using sidelink signals137without relaying that communication through a base station. In some examples, the UEs138,140, and142may each function as a scheduling entity or transmitting sidelink device and/or a scheduled entity or a receiving sidelink device to schedule resources and communicate sidelink signals137therebetween without relying on scheduling or control information from a base station. In other examples, two or more UEs (e.g., UEs126and128) within the coverage area of a base station (e.g., base station112) may also communicate sidelink signals127over a direct link (sidelink) without conveying that communication through the base station112. In this example, the base station112may allocate resources to the UEs126and128for the sidelink communication. In either case, such sidelink signaling127and137may be implemented in a peer-to-peer (P2P) network, a device-to-device (D2D) network, a vehicle-to-vehicle (V2V) network, a vehicle-to-everything (V2X) network, a mesh network, or other suitable direct link network.

In some examples, a D2D relay framework may be included within a cellular network to facilitate relaying of communication to/from the base station112via D2D links (e.g., sidelinks127or137). For example, one or more UEs (e.g., UE128) within the coverage area of the base station112may operate as relaying UEs to extend the coverage of the base station112, improve the transmission reliability to one or more UEs (e.g., UE126), and/or to allow the base station to recover from a failed UE link due to, for example, blockage or fading.

Two primary technologies that may be used by V2X networks include dedicated short range communication (DSRC) based on IEEE 802.11p standards and cellular V2X based on LTE and/or 5G (New Radio) standards. Various aspects of the present disclosure may relate to New Radio (NR) cellular V2X networks, referred to herein as V2X networks, for simplicity. However, it should be understood that the concepts disclosed herein may not be limited to a particular V2X standard or may be directed to sidelink networks other than V2X networks.

Data coding may be implemented in multiple manners. In early 5G NR specifications, user data is coded using quasi-cyclic low-density parity check (LDPC) with two different base graphs: one base graph is used for large code blocks and/or high code rates, while the other base graph is used otherwise. Control information and the physical broadcast channel (PBCH) are coded using Polar coding, based on nested sequences. For these channels, puncturing, shortening, and repetition are used for rate matching.

Aspects of the present disclosure may be implemented utilizing any suitable channel code. Various implementations of base stations and UEs may include suitable hardware and capabilities (e.g., an encoder, a decoder, and/or a CODEC) to utilize one or more of these channel codes for wireless communication.

In the RAN100, the ability for a UE to communicate while moving, independent of their location, is referred to as mobility. The various physical channels between the UE and the RAN are generally set up, maintained, and released under the control of an access and mobility management function (AMF). In some scenarios, the AMF may include a security context management function (SCMF) and a security anchor function (SEAF) that performs authentication. The SCMF can manage, in whole or in part, the security context for both the control plane and the user plane functionality.

In some examples, a RAN100may enable mobility and handovers (i.e., the transfer of a UE's connection from one radio channel to another). For example, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE124may move from the geographic area corresponding to its serving cell102to the geographic area corresponding to a neighbor cell106. When the signal strength or quality from the neighbor cell106exceeds that of its serving cell102for a given amount of time, the UE124may transmit a reporting message to its serving base station110indicating this condition. In response, the UE124may receive a handover command, and the UE may undergo a handover to the cell106.

The air interface in the RAN100may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, 5G NR specifications provide multiple access for UL or reverse link transmissions from UEs122and124to base station110, and for multiplexing DL or forward link transmissions from the base station110to UEs122and124utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP). In addition, for UL transmissions, 5G NR specifications provide support for discrete Fourier transform-spread-OFDM (DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA (SC-FDMA)). However, within the scope of the present disclosure, multiplexing and multiple access are not limited to the above schemes, and may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing DL transmissions from the base station110to UEs122and124may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), or other suitable multiplexing schemes.

A set of continuous or discontinuous resource blocks may be referred to herein as a Resource Block Group (RBG), sub-band, or bandwidth part (BWP). A set of sub-bands or BWPs may span the entire bandwidth. Scheduling of UEs or sidelink devices (hereinafter collectively referred to as UEs) for downlink, uplink, or sidelink transmissions typically involves scheduling one or more resource elements206within one or more sub-bands or bandwidth parts (BWPs). Thus, a UE generally utilizes only a subset of the resource grid204. In some examples, an RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more RBs scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE. The RBs may be scheduled by a base station (e.g., gNB, eNB, etc.) or may be self-scheduled by a UE/sidelink device implementing D2D sidelink communication.

In this illustration, the RB208is shown as occupying less than the entire bandwidth of the subframe202, with some subcarriers illustrated above and below the RB208. In a given implementation, the subframe202may have a bandwidth corresponding to any number of one or more RBs208. Further, in this illustration, the RB208is shown as occupying less than the entire duration of the subframe202, although this is merely one possible example.

An expanded view of one of the slots210illustrates the slot210including a control region212and a data region214. In general, the control region212may carry control channels, and the data region214may carry data channels. Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL portion. The structure illustrated inFIG. 2is merely exemplary in nature, and different slot structures may be utilized, and may include one or more of each of the control region(s) and data region(s).

Although not illustrated inFIG. 2, the various REs206within a RB208may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs206within the RB208may also carry pilots or reference signals. These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB208.

In some examples, the slot210may be utilized for broadcast, multicast, groupcast, or unicast communication. For example, a broadcast, multicast, or groupcast communication may refer to a point-to-multipoint transmission by one device (e.g., a base station, UE, or other similar device) to other devices. Here, a broadcast communication is delivered to all devices, whereas a multicast or groupcast communication is delivered to multiple intended recipient devices. A unicast communication may refer to a point-to-point transmission by a one device to a single other device.

The PBCH in the SSB may further include a master information block (MIB) that includes various system information, along with parameters for decoding a system information block (SIB). The SIB may be, for example, a SystemInformationType 1 (SIB1) that may include various additional system information. The MIB and SIB1 together provide the minimum system information (SI) for initial access. Examples of system information transmitted in the MIB may include, but are not limited to, a subcarrier spacing (e.g., default downlink numerology), system frame number, a configuration of a PDCCH control resource set (CORESET) (e.g., PDCCH CORESET0), a cell barred indicator, a cell reselection indicator, a raster offset, and a search space for SIB1. Examples of remaining minimum system information (RMSI) transmitted in the SIB1 may include, but are not limited to, a random access search space, a paging search space, downlink configuration information, and uplink configuration information.

In an UL transmission, the scheduled entity (e.g., UE) may utilize one or more REs206to carry UL control information (UCI) including one or more UL control channels, such as a physical uplink control channel (PUCCH), to the scheduling entity. UCI may include a variety of packet types and categories, including pilots, reference signals, and information configured to enable or assist in decoding uplink data transmissions. Examples of uplink reference signals may include a sounding reference signal (SRS) and an uplink DMRS. In some examples, the UCI may include a scheduling request (SR), i.e., request for the scheduling entity to schedule uplink transmissions. Here, in response to the SR transmitted on the UCI, the scheduling entity may transmit downlink control information (DCI) that may schedule resources for uplink packet transmissions. UCI may also include HARQ feedback, channel state feedback (CSF), such as a CSI report, or any other suitable UCI.

In addition to control information, one or more REs206(e.g., within the data region214) may be allocated for data traffic. Such data traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for an UL transmission, a physical uplink shared channel (PUSCH). In some examples, one or more REs206within the data region214may be configured to carry other signals, such as one or more SIBs and DMRSs.

In an example of sidelink communication over a sidelink carrier via a PC5 interface, the control region212of the slot210may include a physical sidelink control channel (PSCCH) including sidelink control information (SCI) transmitted by an initiating (transmitting) sidelink device (e.g., Tx V2X device or other Tx UE) towards a set of one or more other receiving sidelink devices (e.g., Rx V2X device or other Rx UE). The data region214of the slot210may include a physical sidelink shared channel (PSSCH) including sidelink data traffic transmitted by the initiating (transmitting) sidelink device within resources reserved over the sidelink carrier by the transmitting sidelink device via the SCI. Other information may further be transmitted over various REs206within slot210. For example, HARQ feedback information may be transmitted in a physical sidelink feedback channel (PSFCH) within the slot210from the receiving sidelink device to the transmitting sidelink device. In addition, one or more reference signals, such as a sidelink SSB, a sidelink CSI-RS, a sidelink SRS, and/or a sidelink positioning reference signal (PRS) may be transmitted within the slot210.

The channels or carriers illustrated inFIG. 2are not necessarily all of the channels or carriers that may be utilized between devices, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels.

FIG. 3illustrates an example of a wireless communication network300configured to support D2D or sidelink communication. In some examples, sidelink communication may include V2X communication. V2X communication involves the wireless exchange of information directly between not only vehicles (e.g., vehicles302and304) themselves, but also directly between vehicles302/304and infrastructure (e.g., roadside units (RSUs)306), such as streetlights, buildings, traffic cameras, tollbooths or other stationary objects, vehicles302/304and pedestrians308, and vehicles302/304and wireless communication networks (e.g., base station310). In some examples, V2X communication may be implemented in accordance with the New Radio (NR) cellular V2X standard defined by 3GPP, Release 16, or other suitable standard.

V2X communication enables vehicles302and304to obtain information related to the weather, nearby accidents, road conditions, activities of nearby vehicles and pedestrians, objects nearby the vehicle, and other pertinent information that may be utilized to improve the vehicle driving experience and increase vehicle safety. For example, such V2X data may enable autonomous driving and improve road safety and traffic efficiency. For example, the exchanged V2X data may be utilized by a V2X connected vehicle302and304to provide in-vehicle collision warnings, road hazard warnings, approaching emergency vehicle warnings, pre-/post-crash warnings and information, emergency brake warnings, traffic jam ahead warnings, lane change warnings, intelligent navigation services, and other similar information. In addition, V2X data received by a V2X connected mobile device of a pedestrian/cyclist308may be utilized to trigger a warning sound, vibration, flashing light, etc., in case of imminent danger.

The sidelink communication between vehicle-UEs (V-UEs)302and304or between a V-UE302or304and either an RSU306or a pedestrian-UE (P-UE)308may occur over a sidelink312utilizing a proximity service (ProSe) PC5 interface. In various aspects of the disclosure, the PC5 interface may further be utilized to support D2D sidelink312communication in other proximity use cases (e.g., other than V2X). Examples of other proximity use cases may include smart wearables, public safety, or commercial (e.g., entertainment, education, office, medical, and/or interactive) based proximity services. In the example shown inFIG. 3, ProSe communication may further occur between UEs314and316.

ProSe communication may support different operational scenarios, such as in-coverage, out-of-coverage, and partial coverage. Out-of-coverage refers to a scenario in which UEs (e.g., UEs314and316) are outside of the coverage area of a base station (e.g., base station310), but each are still configured for ProSe communication. Partial coverage refers to a scenario in which some of the UEs (e.g., V-UE304) are outside of the coverage area of the base station310, while other UEs (e.g., V-UE302and P-UE308) are in communication with the base station310. In-coverage refers to a scenario in which UEs (e.g., V-UE302and P-UE308) are in communication with the base station310(e.g., gNB) via a Uu (e.g., cellular interface) connection to receive ProSe service authorization and provisioning information to support ProSe operations.

To facilitate D2D sidelink communication between, for example, UEs314and316over the sidelink312, the UEs314and316may transmit discovery signals therebetween. In some examples, each discovery signal may include a synchronization signal, such as a primary synchronization signal (PSS) and/or a secondary synchronization signal (SSS) that facilitates device discovery and enables synchronization of communication on the sidelink312. For example, the discovery signal may be utilized by the UE316to measure the signal strength and channel status of a potential sidelink (e.g., sidelink312) with another UE (e.g., UE314). The UE316may utilize the measurement results to select a UE (e.g., UE314) for sidelink communication or relay communication.

In 5G NR sidelink, sidelink communication may utilize transmission or reception resource pools. For example, the minimum resource allocation unit in frequency may be a sub-channel (e.g., which may include, for example, 10, 15, 20, 25, 50, 75, or 100 consecutive resource blocks) and the minimum resource allocation unit in time may be one slot. The number of sub-channels in a resource pool may include between one and twenty-seven sub-channels. A radio resource control (RRC) configuration of the resource pools may be either pre-configured (e.g., a factory setting on the UE determined, for example, by sidelink standards or specifications) or configured by a base station (e.g., base station310).

In addition, there may be two main resource allocation modes of operation for sidelink (e.g., PC5) communications. In a first mode, Mode 1, a base station (e.g., gNB)310may allocate resources to sidelink devices (e.g., V2X devices or other sidelink devices) for sidelink communication between the sidelink devices in various manners. For example, the base station310may allocate sidelink resources dynamically (e.g., a dynamic grant) to sidelink devices, in response to requests for sidelink resources from the sidelink devices. For example, the base station310may schedule the sidelink communication via DCI 3_0. In some examples, the base station310may schedule the PSCCH/PSSCH within uplink resources indicated in DCI 3_0. The base station310may further activate preconfigured sidelink grants (e.g., configured grants) for sidelink communication among the sidelink devices. In some examples, the base station310may activate a configured grant (CG) via RRC signaling. In Mode 1, sidelink feedback may be reported back to the base station310by a transmitting sidelink device.

In a second mode, Mode 2, the sidelink devices may autonomously select sidelink resources for sidelink communication therebetween. In some examples, a transmitting sidelink device may perform resource/channel sensing to select resources (e.g., sub-channels) on the sidelink channel that are unoccupied. Signaling on the sidelink is the same between the two modes. Therefore, from a receiver's point of view, there is no difference between the modes.

In some examples, sidelink (e.g., PC5) communication may be scheduled by use of sidelink control information (SCI). SCI may include two SCI stages. Stage 1 sidelink control information (first stage SCI) may be referred to herein as SCI-1. Stage 2 sidelink control information (second stage SCI) may be referred to herein as SCI-2.

SCI-1 may be transmitted on a physical sidelink control channel (PSCCH). SCI-1 may include information for resource allocation of a sidelink resource and for decoding of the second stage of sidelink control information (i.e., SCI-2). SCI-1 may further identify a priority level (e.g., Quality of Service (QoS)) of a PSSCH. For example, ultra-reliable-low-latency communication (URLLC) traffic may have a higher priority than text message traffic (e.g., short message service (SMS) traffic). SCI-1 may also include a physical sidelink shared channel (PSSCH) resource assignment and a resource reservation period (if enabled). Additionally, SCI-1 may include a PSSCH demodulation reference signal (DMRS) pattern (if more than one pattern is configured). The DMRS may be used by a receiver for radio channel estimation for demodulation of the associated physical channel. As indicated, SCI-1 may also include information about the SCI-2, for example, SCI-1 may disclose the format of the SCI-2. Here, the format indicates the resource siz of SCI-2 (e.g., a number of REs that are allotted for SCI-2), a number of a PSSCH DMRS port(s), and a modulation and coding scheme (MCS) index. In some examples, SCI-1 may use two bits to indicate the SCI-2 format. Thus, in this example, four different SCI-2 formats may be supported. SCI-1 may include other information that is useful for establishing and decoding a PSSCH resource.

SCI-2 may be transmitted on the PSSCH and may contain information for decoding the PSSCH. According to some aspects. SCI-2 includes a 16-bit layer 1 (L1) destination identifier (ID), an 8-bit L1 source ID, a hybrid automatic repeat request (HARQ) process ID, a new data indicator (NDI), and a redundancy version (RV). For unicast communications, SCI-2 may further include a CSI report trigger. For groupcast communications, SCI-2 may further include a zone identifier and a maximum communication range for NACK. SCI-2 may include other information that is useful for establishing and decoding a PSSCH resource.

FIGS. 4A and 4Bare diagrams illustrating examples of sidelink slot structures according to some aspects. The sidelink slot structures may be utilized, for example, in a V2X or other D2D network implementing sidelink. In the examples shown inFIGS. 4A and 4B, time is in the horizontal direction with units of symbols402(e.g., OFDM symbols); and frequency is in the vertical direction. Here, a carrier bandwidth404allocated for sidelink wireless communication is illustrated along the frequency axis. The carrier bandwidth404may include a plurality of sub-channels, where each sub-channel may include a configurable number of PRBs (e.g., 10, 14, 20, 24, 40, 44, or 100 PRBs).

Each ofFIGS. 4A and 4Billustrate an example of a respective slot400aor400bincluding fourteen symbols402that may be used for sidelink communication. However, it should be understood that sidelink communication can be configured to occupy fewer than fourteen symbols in a slot400aor400b, and the disclosure is not limited to any particular number of symbols402. Each sidelink slot400aand400bincludes a physical sidelink control channel (PSCCH)406occupying a control region418of the slot400aand400band a physical sidelink shared channel (PSSCH)408occupying a data region420of the slot400aand400b. The PSCCH406and PSSCH408are each transmitted on one or more symbols402of the slot400a. The PSCCH406includes, for example, SCI-1 that schedules transmission of data traffic on time-frequency resources of the corresponding PSSCH408. As shown inFIGS. 4A and 4B, the PSCCH406and corresponding PSSCH408are transmitted in the same slot400aand400b. In other examples, the PSCCH406may schedule a PSSCH in a subsequent slot.

In some examples, the PSCCH406duration is configured to be two or three symbols. In addition, the PSCCH406may be configured to span a configurable number of PRBs, limited to a single sub-channel. The PSCCH resource size may be fixed for a resource pool (e.g., 10% to 100% of one sub-channel in the first two or three symbols). For example, the PSCCH406may occupy 10, 12, 15, 20, or 25 RBs of a single sub-channel. A DMRS may further be present in every PSCCH symbol. In some examples, the DMRS may be placed on every fourth RE of the PSCCH406. A frequency domain orthogonal cover code (FD-OCC) may further be applied to the PSCCH DMRS to reduce the impact of colliding PSCCH transmissions on the sidelink channel. For example, a transmitting UE may randomly select the FD-OCC from a set of pre-defined FD-OCCs. In each of the examples shown inFIGS. 4A and 4B, the starting symbol for the PSCCH406is the second symbol of the corresponding slot400aor400band the PSCCH406spans three symbols402.

The PSSCH408may be time-division multiplexed (TDMed) with the PSCCH406and/or frequency-division multiplexed (FDMed) with the PSCCH406. In the example shown inFIG. 4A, the PSSCH408includes a first portion408athat is TDMed with the PSCCH406and a second portion408bthat is FDMed with the PSCCH406. In the example shown inFIG. 4B, the PSSCH408is TDMed with the PSCCH406.

One and two layer transmissions of the PSSCH408may be supported with various modulation orders (e.g., quadrature phase shift keying (QPSK), 16-QAM, 64-QAM and 256-QAM). In addition, the PSSCH408may include DMRSs414configured in a two, three, or four symbol DMRS pattern. For example, slot400ashown inFIG. 4Aillustrates a two symbol DMRS pattern, while slot400bshown inFIG. 4Billustrates a three symbol DMRS pattern. In some examples, the transmitting UE can select the DMRS pattern and indicate the selected DMRS pattern in SCI-1, according to channel conditions. The DMRS pattern may be selected, for example, based on the number of PSSCH408symbols in the slot400aor400b. In addition, a gap symbol416is present after the PSSCH408in each slot400aand400b.

Each slot400aand400bfurther includes SCI-2412mapped to contiguous RBs in the PSSCH408starting from the first symbol containing a PSSCH DMRS. In the example shown inFIG. 4A, the first symbol containing a PSSCH DMRS is the fifth symbol occurring immediately after the last symbol carrying the PSCCH406. Therefore, the SCI-2412is mapped to RBs within the fifth symbol. In the example shown inFIG. 4B, the first symbol containing a PSSCH DMRS is the second symbol, which also includes the PSCCH406. In addition, the SCI-2/PSSCH DMRS412are shown spanning symbols two through five. As a result, the SCI-2/PSSCH DMRS412may be FDMed with the PSCCH406in symbols two through four and TDMed with the PSCCH406in symbol five.

The SCI-2 may be scrambled separately from the sidelink shared channel. In addition, the SCI-2 may utilize QPSK. When the PSSCH transmission spans two layers, the SCI-2 modulation symbols may be copied on (e.g., repeated on) both layers. The SCI-1 in the PSCCH406may be blind decoded at the receiving wireless communication device. However, since the format, starting location, and number of REs of the SCI-2412may be derived from the SCI-1, blind decoding of SCI-2 is not needed at the receiver (receiving UE).

In each ofFIGS. 4A and 4B, the second symbol of each slot400aand400bis copied onto (repeated on) a first symbol410thereof for automatic gain control (AGC) settling. For example, inFIG. 4A, the second symbol containing the PSCCH406FDMed with the PSSCH408may be transmitted on both the first symbol and the second symbol. In the example shown inFIG. 4B, the second symbol containing the PSCCH406FDMed with the SCI-2/PSSCH DMRS412may be transmitted on both the first symbol and the second symbol.

FIG. 5is a diagram illustrating an example of a sidelink slot structure with feedback resources according to some aspects. The sidelink slot structure may be utilized, for example, in a V2X or other D2D network implementing sidelink. In the example shown inFIG. 5, time is in the horizontal direction with units of symbols502(e.g., OFDM symbols); and frequency is in the vertical direction. Here, a carrier bandwidth504allocated for sidelink wireless communication is illustrated along the frequency axis. A slot500having the slot structure shown inFIG. 5includes fourteen symbols502that may be used for sidelink communication. However, it should be understood that sidelink communication can be configured to occupy fewer than fourteen symbols in a slot500, and the disclosure is not limited to any particular number of symbols502.

As in the examples shown inFIGS. 4A and 4B, the sidelink slot500includes a PSCCH506occupying a control region of the slot500and a PSSCH508occupying a data region520of the slot500. The PSCCH506and PSSCH508are each transmitted on one or more symbols502of the slot500a. The PSCCH506includes, for example, SCI-1 that schedules transmission of data traffic on time-frequency resources of the corresponding PSSCH508. As shown inFIG. 5, the starting symbol for the PSCCH506is the second symbol of the slot500and the PSCCH506spans three symbols502. The PSSCH508may be time-division multiplexed (TDMed) with the PSCCH506and/or frequency-division multiplexed (FDMed) with the PSCCH506. In the example shown inFIG. 5, the PSSCH508includes a first portion508athat is TDMed with the PSCCH506and a second portion508bthat is FDMed with the PSCCH506.

The PSSCH508may further include a DMRSs514configured in a two, three, or four symbol DMRS pattern. For example, slot500shown inFIG. 5illustrates a two symbol DMRS pattern. In some examples, the transmitting UE can select the DMRS pattern and indicate the selected DMRS pattern in SCI-1, according to channel conditions. The DMRS pattern may be selected, for example, based on the number of PSSCH508symbols in the slot500. In addition, a gap symbol516is present after the PSSCH508in the slot500.

The slot500further includes SCI-2512mapped to contiguous RBs in the PSSCH508starting from the first symbol containing a PSSCH DMRS. In the example shown inFIG. 5, the first symbol containing a PSSCH DMRS is the fifth symbol occurring immediately after the last symbol carrying the PSCCH506. Therefore, the SCI-2512is mapped to RBs within the fifth symbol.

In addition, as shown inFIG. 5, the second symbol of the slot500is copied onto (repeated on) a first symbol510thereof for automatic gain control (AGC) settling. For example, inFIG. 5, the second symbol containing the PSCCH506FDMed with the PSSCH508may be transmitted on both the first symbol and the second symbol.

HARQ feedback may further be transmitted on a physical sidelink feedback channel (PSFCH)518in a configurable resource period of 0, 1, 2, or 4 slots. In sidelink slots (e.g., slot500) containing the PSFCH518, one symbol502may be allocated to the PSFCH518, and the PSFCH518may be copied onto (repeated on) a previous symbol for AGC settling. In the example shown inFIG. 5, the PSFCH518is transmitted on the thirteenth symbol and copied onto the twelfth symbol in the slot500c. A gap symbol516may further be placed after the PSFCH518symbols.

In some examples, there is a mapping between the PSSCH508and the corresponding PSFCH resource. The mapping may be based on, for example, the starting sub-channel of the PSSCH508, the slot containing the PSSCH508, the source ID and the destination ID. In addition, the PSFCH can be enabled for unicast and groupcast communication. For unicast, the PSFCH may include one ACK/NACK bit. For groupcast, there may be two feedback modes for the PSFCH. In a first groupcast PSFCH mode, the receiving UE transmits only NACK, whereas in a second groupcast PSFCH mode, the receiving UE may transmit either ACK or NACK. The number of available PSFCH resources may be equal to or greater than the number of UEs in the second groupcast PSFCH mode.

In some examples, the SCI (e.g., SCI-1 and/or SCI-2) may further identify one or more additional resources (e.g., retransmission resources) reserved for one or more retransmissions of the sidelink transmission (sidelink data). Thus, the SCI may include a respective PSSCH resource reservation and assignment for one or more retransmissions of the PSSCH. For example, the SCI may include a reservation message indicating the PSSCH resource reservation for the initial sidelink transmission (initial PSSCH) and one or more additional PSSCH resource reservations for one or more retransmissions of the PSSCH.

In some examples, instead of transmitting the reservation message for a sidelink transmission together with the sidelink transmission, a UE may schedule resources ahead of time for a subsequent sidelink transmission and transmit the reservation message prior to the sidelink transmission. For example, a UE may schedule resources in slot N for a sidelink transmission and transmit the reservation message reserving the resources for the sidelink transmission in slot N-K (where N>K). By reserving resources for a subsequent sidelink transmission, interference between the sidelink transmission and other sidelink transmissions may be reduced or avoided.

For example, if the packet to be transmitted in sidelink utilizes a bandwidth of 10 MHz, and there is a collision between the sidelink transmission and another transmission, the 10 MHz bandwidth may be wasted. To avoid this, the transmitting UE may transmit the reservation message with robust coding and fewer resources than the sidelink transmission (e.g., 1 MHz or 2 MHz for the reservation message vs. 10 MHz for the sidelink transmission) to reserve the resource for the 10 MHz transmission. Thus, if there is a collision during the transmission of the reservation message, only 1 MHz of bandwidth is lost. Further, even if there is a collision between the reservation message and another message, the robust coding of the reservation message may increase the likelihood that the reservation message could still be received and decoded by a recipient UE.

However, another UE more distant from the transmitting UE than the recipient UE may not receive any reservation message from the transmitting UE. Thus, the other UE may schedule its sidelink transmission on the same resources indicated in the reservation message, which may cause interference during the sidelink transmission (e.g., initial transmission and/or retransmission) from the transmitting UE.

Therefore, in various aspects of the disclosure, a receiving UE may forward a reservation message from the transmitting UE to other UEs, thereby extending the range of the reservation message. In some examples, the receiving UE may transmit a reservation forwarding message, which may include the reservation message or an indication of reserved resources in the reservation message, to one or more other UEs (remote UEs relative to the receiving UE). The reservation forwarding message may be transmitted via, for example, a sidelink radio resource control (RRC) message or a sidelink medium access control (MAC) control element (MAC-CE). A remote UE receiving the reservation forwarding message may abstain from using the resources indicated in the reservation forwarding message for its sidelink transmission(s).

FIG. 6is a schematic diagram illustrating an example600of a transmission of a first reservation forwarding message according to some aspects. In the example shown inFIG. 6, a first user equipment (UE)602(e.g., a first wireless communication device) may be in wireless communication with a second UE604(e.g., a second wireless communication device) via sidelink. Also, in the example shown inFIG. 6, the first UE602may be in wireless communication with a third UE606(e.g., a third wireless communication device) via sidelink. In some aspects, the first UE602may still further be in wireless communication with a fourth UE608(e.g., a fourth wireless communication device) via sidelink. Each of the first UE602, the second UE604, the third UE606, and the fourth UE608may correspond to any UE (e.g., wireless communication devices) as shown and described in connection withFIGS. 1 and/or 3, for example.

The second UE604may schedule an initial transmission of a first data packet on one or more second sidelink resources. The second UE604may generate a first reservation message, including an indication of the one or more second sidelink resources reserved for the initial transmission of the first data packet. As exemplified inFIG. 6, at610, the second UE604may transmit, and the first UE602may receive the first reservation message on the one or more first sidelink resources. A sidelink transmission may include a SCI-1 and/or SCI-2 (e.g., carried in the control portion) and a data portion or payload (e.g., carried in the PSSCH). The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some examples, the first reservation message may not include any data. In this example, the one or more first sidelink resources may include the control portion (e.g., SCI-1 and/or SCI-2) and/or the data portion (or payload) in a PSSCH utilized for the reservation message. It is noted that a control portion may include SCI-1 and SCI-2, but SCI-2 is carried in the PSSCH. For example, the one or more first sidelink resources may include a small number of resources (e.g., one or two subchannels).

In some aspects, the first reservation message may indicate the reservation of the one or more second sidelink resources for the initial transmission of the first data packet by the second UE604but may also include other reservation information. For example, the first reservation message may also include an indication of the one or more other sidelink resources for retransmission(s) of the first data packet and/or other reservations of still other sidelink resources made by other UEs (e.g., the fourth UE608) for transmissions and/or retransmissions of their own. The selection of the one or more first sidelink resources, one or more second sidelink resources, and/or one or more other sidelink resources may be based on, for example, availability of sidelink resources, a signal strength of the one or more sidelink resources, a signal quality of the one or more sidelink resources, a combination thereof, or the like.

The first reservation message may be transmitted from the second UE604to the third UE606; however, the third UE606may not be within the reception range of the transmission of the first reservation message transmitted by the second UE604. Accordingly, at612, in response to receiving the first reservation message directly from the second UE604, the first UE602may broadcast (e.g., to all UEs in the system, including the second UE604, the third UE606, and the fourth UE608) a first reservation forwarding message on one or more third sidelink resources. The first reservation forwarding message may include multiple reservation messages from multiple UEs (including the first reservation message from the second UE604, the second reservation message from the fourth UE, and/or a second reservation forwarding message(s) (not shown) from any UE). In some examples, the first reservation forwarding message may include indications of the sidelink resources reserved in multiple sidelink resource reservations made by multiple UEs (including the one or more second sidelink resources reserved in the first reservation message of the second UE604). In other words, the second UE604may have obtained other reservation messages from other UEs and may include those other reservation messages, or indications of the sidelink resources reserved in the other reservation messages, in the first reservation message (at610) from the second UE604to at least the first UE602.

In some examples, the first reservation message may include an indication of one or more sidelink resources that are to be used for a retransmission of the first data packet if a collision occurs when initially transmitting the first data packet at614, or other conditions (e.g., interference) preventing the first UE602from receiving and decoding the first data packet at614. The one or more sidelink resources indicated for retransmission may include one or more different sidelink resources (e.g., different from one or more second sidelink resources used for initially transmitting the first data packet at614).

The first reservation message may have a transmission bandwidth (e.g., 1 MHz to 2 MHz) that is smaller than the transmission bandwidth (e.g., 10 MHz) that may be used to transmit the data packet. In addition, the second UE604may transmit the first reservation message with robust coding. A relatively larger transmission bandwidth (of the first data packet) than a relatively smaller transmission bandwidth (of the first reservation message) may have a higher modulation order and higher coding rate, thereby decreasing transmission reliability. The relatively smaller transmission bandwidth of the first reservation message, in combination with the robust coding of the first reservation message, may increase the likelihood of the first UE602receiving and decoding the first reservation message while minimizing the potential for wasting relatively larger amounts of bandwidth during an occurrence of a collision. For example, the one or more first sidelink resources used to transmit the first reservation message from the second UE604to the first UE602may include fewer resources than the one or more second sidelink resources used to transmit the first data packet from the second UE604to the first UE602.

In some aspects, in response to the first UE602receiving the first reservation message (at610), the first UE602may measure a reference signal received power (RSRP) of the first reservation message (i.e., measure an RSRP associated with the first reservation message). In some aspects, the first UE602may include the RSRP of the first reservation message in the first reservation forwarding message (at612). In some aspects, the first UE602may further include an identification (identifier) of the first UE602and/or the second UE604in the first reservation forwarding message. The identification (identifier) of the first UE602and/or the second UE604may be obtained from the SCI (e.g., SCI-2) or a sidelink MAC header if data is also received with the first reservation message, from a sidelink MAC-CE, or a sidelink RRC messaging, for example.

The first UE602may generate the first reservation forwarding message. The first reservation forwarding message may include an indication of the one or more second sidelink resources reserved by the first reservation message or include a copy of the first reservation message. The first UE602may transmit the first reservation forwarding message to at least the third UE606(or may broadcast the first reservation forwarding message to all UEs in a system, including the second UE604, the third UE606, and the fourth UE608) to inform at least the third UE606(or, if broadcast, to inform all UEs in the system) of the reservation of the one or more second sidelink resources. The third UE606may then utilize the first reservation forwarding message to determine whether to abstain from using the one or more second sidelink resources indicated in the first reservation message for a sidelink transmission.

In some aspects, the first reservation forwarding message may be included a data portion and/or a control portion of a sidelink transmission. In some aspects, the first reservation forwarding message may be included in a sidelink medium access control (MAC) control element (MAC-CE) and included in the data portion of the sidelink transmission. In some aspects, the first reservation forwarding message may be included in a sidelink radio resource control (RRC) message and included in the data portion of the sidelink transmission. In some aspects, the first reservation forwarding message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink transmission.

In some aspects, the first UE602may include a single bit in the first reservation forwarding message indicating to the third UE606that the first UE602is the intended recipient of the first data packet on the one or more second sidelink resources. The single bit (Rx bit) may provide an indication to the third UE606that the third UE606is to abstain from transmitting (or more broadly, communicating) using the one or more second sidelink resources to not interfere with the reception of the first data packet at the first UE602. By the third UE606abstaining from transmitting on the one or more second sidelink resources, the first UE602may receive the first data packet on the one or more second sidelink resources from the second UE604while minimizing interference (and/or other conditions) and the potential for a collision with a transmission from the third UE606.

In some aspects, the first UE602may identify a prospective collision associated with transmitting the first data packet from the second UE604and transmitting a second data packet by a fourth UE. According to such aspects, the first UE602may include an indication of the prospective collision in the first reservation forwarding message. The first reservation forwarding message may then be broadcast to all UEs in the system, including, for example, the second UE604, the third UE606, and the fourth UE608. In response to receiving the indication, the second UE604and the third UE606may either negotiate to avoid the collision or follow a predetermined course of action to avoid the collision.

In some examples, a single bit may indicate the prospective collision. Including the indication of the prospective collision may entail including the single bit in the second stage sidelink control information (SCI-2) or in a payload of the first reservation forwarding message in a physical sidelink shared channel (PSSCH).

In some aspects, the first UE602may detect a collision of the first reservation message with the second reservation message by comparing a first RSRP value of the received first reservation message with a second RSRP value of the received second reservation message. For example, in a state where the first RSRP value exceeds the second RSRP value by a predetermined amount (e.g., the first RSRP value is relatively larger than the second RSRP value), the first UE602may determine that a collision may have occurred. However, the first UE602would still be able to decode the first reservation message. Therefore, the first UE602may determine to forward the first reservation message (or an indication of its contents) in the first reservation forwarding message (even if the first data packet is not intended for the first UE602). For example, the first UE602may determine to transmit the first reservation forwarding message, including the first reservation message, in response to detecting the first collision to ensure other UEs can receive and decode the first reservation message.

Similarly, in some aspects, the first UE602may identify a prospective collision between the first data packet to be transmitted by the second UE604and a second data packet to be transmitted by the fourth UE608. For example, at616, the first UE602may receive a second reservation message on one or more fourth sidelink resources from the fourth UE608. The second reservation message may indicate that the one or more second sidelink resources, or some portion thereof, are reserved by the fourth UE for an initial transmission or retransmission of the second data packet. For example, the first UE602may determine that the one or more second sidelink resources reserved by the second UE604for transmission of the first data packet overlap in time and/or frequency with the one or more other sidelink resources reserved by the fourth UE608for transmission of the second data packet.

As stated, the first UE602may include an indication of an actual or prospective collision in the first reservation forwarding message. In some aspects, the indication of the actual or prospective collision may be a single bit included in an SCI-2 or the PSSCH of the first reservation forwarding message. In some aspects, the second UE604may transmit the first reservation forwarding message as a broadcast message reaching a plurality of UEs, including the second UE604, the third UE606, and the fourth UE608. In this example, the first reservation forwarding message may further include an identifier (ID) of at least one of the second UE604or the fourth UE608(e.g., the UE's involved in the prospective collision), requesting that at least one of the second UE604or the fourth UE608avoid the potential second collision (e.g., by changing the one or more sidelink resources associated with the subsequent transmission of their respective data packets).

In addition to the first reservation message, as described herein, the first UE602may receive the second reservation message from the fourth UE608. As indicated above, the second reservation message may include an indication of the one or more second sidelink resources for a subsequent transmission of a second data packet from the fourth UE608. In response to receiving the second reservation message, the first UE602may include an indication of the second reservation message in the first reservation forwarding message. In some examples, the first UE602may include the indication of the second reservation message in the first reservation forwarding message in response to detecting a collision, as described above. In some aspects, in response to receiving the first reservation message from the second UE604and the second reservation message from the fourth UE608, the first UE602may include in the first reservation forwarding message at least one bit indicating that the first UE602is an intended recipient of the transmission of the first data packet and that the first UE602is not the intended recipient of the transmission of the second data packet.

The first UE602may broadcast the first reservation forwarding message to the second UE604, the third UE606, and/or the fourth UE608using one or more third sidelink resources. For example, the first UE602may broadcast the first reservation forwarding message to inform the second UE604, the third UE606, and/or the fourth UE608that the second UE604is the intended recipient of the first data packet on the one or more second sidelink resources reserved by the second UE604. In some aspects, the first UE602may broadcast the first reservation forwarding message in a sidelink MAC-CE via a PSSCH. In some aspects, the first UE602may transmit the first reservation forwarding message to only the third UE606in a sidelink RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE602may transmit the first reservation forwarding message to at least the third UE606in an SCI-2 on a physical sidelink control channel (PSCCH).

In some aspects, the first UE602may broadcast the first reservation forwarding message using a first transmission bandwidth (e.g., 1 MHz to 2 MHz) smaller than a second transmission bandwidth (e.g., 10 MHz) of the first data packet. The first reservation forwarding message may be transmitted with robust coding. A relatively larger transmission bandwidth compared to a relatively smaller transmission bandwidth may have a higher modulation order and higher coding and decoding rates, thereby decreasing transmission reliability. The smaller transmission bandwidth of the first reservation message and the first reservation forwarding message, in combination with robust coding, may increase the likelihood of UE receiving and decoding the first reservation message and the first reservation forwarding message while minimizing the potential for wasting relatively larger amounts of the bandwidth during the occurrence of a collision. For example, the one or more third sidelink resources used to broadcast the first reservation forwarding message from the first UE602may include fewer resources than the one or more second sidelink resources sued for transmitting the first data packet from the second UE604to the first UE602.

As described herein, in some examples, in response to the first UE602receiving the first reservation message, the first UE602may determine if the first UE602is an intended recipient of the first data packet. In some examples, in response to the first UE602receiving the first reservation message, the first UE602may obtain an RSRP value of the first reservation message. In other examples, the first UE602may determine if the first UE602is the intended recipient of the first data packet and obtain the RSRP value of the first reservation message. In some aspects, the first UE602may obtain the RSRP value by measurement. For example, the first UE602may measure the RSRP value of the first reservation message. In some aspects, the first UE602may include the RSRP of the first reservation message in the first reservation forwarding message. According to some aspects, in response to obtaining an RSRP value of the first reservation message, the first UE602may compare the RSRP value of the first reservation message received on the one or more first sidelink resources to a threshold value. In one example, the threshold value of the RSRP may be obtained or determined by a priority value indicated by an SCI associated with the first UE602. Other ways of determining the threshold RSRP value are within the scope of the disclosure. According to some examples, the first UE602may transmit the first reservation forwarding message, including the indication of the first reservation message, to the third UE606in response to at least one of: determining that the first UE602is the intended recipient of the first data packet, or determining that the RSRP value is less than the threshold value. Conversely, in response to at least one of: a determination that the first UE602is not the intended recipient of the first data packet or determining that the RSRP value is greater than a threshold value, the first UE602may abstain from transmitting the first reservation forwarding message, including the indication of the first reservation message to the third UE606.

In some aspects, the first UE602may transmit the first reservation forwarding message to at least the third UE606based on whether the first UE602receives a second reservation message or a second reservation forwarding message. For example, the second UE604may have transmitted the first reservation message to a plurality of UEs, including the first UE602. In response to receiving the first reservation message from the second UE604, the first UE602may monitor for a second reservation message or a reservation forwarding message from any UE. In response to receiving the first reservation message from the second UE604, the first UE602may initiate a timer. If the first UE602fails to receive the second reservation message or the reservation forwarding message from any UE before the expiry of the timer, the first UE602may determine to transmit the first reservation forwarding message to the third UE606(e.g., broadcast the first reservation forwarding message to all UEs in the system including the third UE606). Conversely, if the first UE602receives the second reservation message or the reservation forwarding message from any UE before the expiry of the timer, the first UE602may determine not to transmit the first reservation forwarding message to the third UE606.

In some aspects, the first UE602may insert the indication of the first reservation message into a bit map and transmit the bit map in the first reservation forwarding message to at least the third UE606. In some aspects, the bit map may include a plurality of locations, each corresponding to a respective subchannel in a respective slot. The first UE602may insert the indication of the first reservation message into the bit map by inserting the indication of the first reservation message in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. Subsequently, the first UE602may transmit the bit map to at least the third UE606via the one or more forwarding sidelink resources. In some aspects, a bit of “0” in a location of the plurality of locations of the bit map may indicate that no resource reservation is allocated to the respective subchannel of the respective slot and a bit of “1” in the location of the bit map may indicate that at least one resource reservation is allocated to the respective subchannel in the respective slot. In some aspects, a size of the bit map may be preconfigured so that the bit map and/or the size of the bit map does not have to be signaled each time.

In some aspects, each location of the plurality of locations of the bit map may include a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The resource reservation occupation level may be determined based on a reference signal received power (RSRP) associated with zero or more resource reservations of the respective subchannel in the respective slot. In some aspects, the zero or more resource reservations may include a plurality of resource reservations from a plurality of UEs. The resource reservation occupation level of the respective subchannel in the respective slot may be determined, for example, to be given by at least one of: a sum of each RSRP for each resource reservation of the plurality of resource reservations, or a maximum RSRP among the plurality of resource reservations from the plurality of UEs. For example, in response to receiving overlapping forwarded resources from two UEs, the third UE606may avoid using the reserved resources in response to a maximum RSRP associated with the received overlapped forwarded resources being greater an RSRP threshold value (e.g., greater than a maximum RSRP threshold value). In some aspects, the bit map may include a width corresponding to a number of subchannels and a length corresponding to a number of slots.

In response to receiving the first reservation forwarding message, the third UE606may abstain from using the one or more sidelink resources identified in the first reservation forwarding message for communication thereon. For example, the third UE606may receive the first reservation forwarding message from the first UE602. Based on the indication of the one or more sidelink resources reserved by the second UE604any other UEs, the third UE606may determine to abstain from transmitting (or more broadly, communicating) using the one or more sidelink resources. In some aspects, the third UE606may abstain from using the one or more sidelink resources based on the first reservation forwarding message, including an indication of a collision or prospective collision between reservation messages and/or data packets. With the third UE606abstaining from transmitting (or more broadly, communicating) on the one or more sidelink resources indicated in the first reservation forwarding message, the second UE604may transmit the first data packet to the first UE602with a reduced risk of a collision between transmissions.

In some aspects, the third UE606may mark the one or more sidelink resources as reserved with the corresponding priority of the first data packet in response to receiving the first reservation forwarding message. In response to receiving the first reservation forwarding message from the first UE602and abstaining from transmitting (or, more broadly, communication) using the one or more sidelink resources, the third UE606may select one or more different sidelink resources for transmitting data packets. For example, the third UE606may select one or more different sidelink resources for communication with the first UE602.

In some aspects, the third UE606may obtain a reference signal received power (RSRP) value of the first reservation forwarding message. In examples in which the first reservation forwarding message indicates that the first UE602is the intended recipient of the first data packet scheduled by the first reservation message (e.g., Rx bit=true), the third UE606may either abstain from using the one or more sidelink resources regardless of the RSRP value or in response to the RSRP value being greater than a threshold. In some aspects, the third UE606may receive the first reservation forwarding message that includes an identifier (ID) of the second UE604. In response to receiving the first reservation forwarding message that includes the ID of the second UE604, the third UE606may identify a stored reference signal received power (RSRP) value obtained from a previous transmission from the second UE604and may abstain from transmitting on the one or more sidelink resources in response to the RSRP value being greater than a threshold value.

In some aspects, the third UE606may receive the first reservation forwarding message from the first UE602, including a first RSRP value associated with the first reservation message from the second UE604. In some examples, the third UE606may normalize the first RSRP value based on a difference between a first number of subchannels utilized for the first reservation message and a second number of subchannels associated with the one or more sidelink resources to produce a normalized RSRP value. In addition, the third UE606may further obtain a second RSRP value of the first reservation forwarding message. In examples in which the first reservation forwarding message does not indicate that the first UE602is the intended recipient of the first data packet scheduled by the first reservation message, the third UE606may abstain from using the one or more sidelink resources based on determining that the first UE602is a potential recipient of the first data packet to be transmitted by the second UE604and abstaining from using the one or more sidelink resources regardless of the first RSRP value or the second RSRP value or in response to the second RSRP value being greater than a threshold value. In some aspects, the third UE606may further abstain from using the one or more sidelink resources in response to a minimum RSRP value between the first RSRP value (or normalized RSRP value) and the second RSRP value being greater than the threshold regardless of whether the first UE602is a potential receiver. In some aspects, the third UE606may receive the first reservation forwarding message from the first UE602, including an identifier (ID) of the second UE604. The third UE606may identify a stored RSRP value obtained from the first UE602from a previous transmission from the second UE604and abstain from using the one or more sidelink resources in response to the stored RSRP value being greater than a threshold value.

In some aspects, the first reservation forwarding message may include a bit map having a plurality of locations, each corresponding to a respective subchannel in a respective slot. The indication of the first reservation message may be included in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. In some aspects, the indication of the first reservation message may include a respective single bit in each of the at least one location in the bit map. In some aspects, each location of the plurality of locations may include a respective multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The third UE606may convert a multi-bit value of the multi-bit values in the at least one location to a corresponding RSRP value and abstain from using the one or more sidelink resources based on the corresponding RSRP value. For example, the third UE606may abstain from using the one or more sidelink resources when the corresponding multi-bit RSRP value is greater than a threshold value or based on the minimum of the multi-bit RSRP value and the RSRP value of the first reservation forwarding message being above a threshold value.

In some aspects, the third UE606may receive at least one additional reservation forwarding message that includes the first reservation message (or includes the indication of the reserved resources in the first reservation message) from at least one additional UE via one or more additional forwarding sidelink resources. In this example, the third UE606may abstain from using the one or more sidelink resources based on whether a respective measured reference signal received power (RSRP) value associated with a respective one of the first reservation forwarding message and the at least one additional reservation forwarding message is greater than a given RSRP value (e.g., a maximum RSRP threshold value). In one example, the third UE606may avoid using the resource identified in the first reservation forwarding message and the at least one additional reservation forwarding message if the measured RSRP associated with any one of the first reservation forwarding message or any one of the at least one additional reservation forwarding message exceeded the given RSRP value. In another example, the third UE606may abstain from using the reserved resources regardless of a measured RSRP value or values.

In some aspects, the second UE604may transmit the first data packet to at least the first UE602using the one or more second sidelink resources. For example, the second UE604may transmit the first data packet to the first UE602using the one or more second sidelink resources, while the third UE606abstains from communication using the one or more second sidelink resources. In some aspects, the second UE604may transmit the first data packet to the first UE602and the third UE606using the one or more second sidelink resources.

FIG. 7is a signaling diagram700illustrating an example of forwarding a resource reservation according to some aspects. In the example shown inFIG. 7, a first user equipment (UE)702(e.g., a wireless communication device) may be in wireless communication with a second UE704(e.g., another wireless communication device) over a sidelink. Also, in the example shown inFIG. 7, the first UE702may be in wireless communication with a third UE706(e.g., another wireless communication device) over a sidelink. The first UE702, the second UE704, and the third UE706may correspond to any of the UEs as shown and described in connection withFIGS. 1, 3, and/or6. In particular, the first UE702may correspond to the first UE602as shown and described in connection withFIG. 6. The second UE704may correspond to the second UE604as shown and described in connection withFIGS. 6, and 6. The third UE706may correspond to the third UE606, as shown and described in connection withFIG. 6.

At708, the second UE704may generate a reservation message, including a first indication of one or more second sidelink resources reserved for transmission of a data packet (e.g., an initial transmission and/or retransmission of the first data packet). For example, the second UE704may select the one or more sidelink resources to transmit the data packet. The selection of the one or more sidelink resources for transmission of the data packet may be based on, for example, availability of sidelink resources, a signal strength of the one or more sidelink resource, a signal quality of the one or more resources, a combination thereof, or the like. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may have a portion transmitted using SCI-2 and another portion transmitted using a MAC-CE.

At710, the second UE704may transmit the first reservation message to the first UE702on one or more first sidelink resources. In some examples, the first reservation message may inform the first UE702that it is the intended recipient of the data packet on the one or more second sidelink resources. As described herein, the first reservation message or an indication of the one or more second sidelink resources identified in the first reservation message may be transmitted from the first UE702to the third UE706to, for example, inform the third UE706to abstain from using (e.g., transmitting) on the one or more second sidelink resources to, for example, reduce the probability of a packet collision when the second UE704transmits the data packet to the first UE702on the one or more second sidelink resources.

In some examples, the first reservation message may include a retransmission resource message. A retransmission resource message may include an indication of one or more other sidelink resources that may be used for a retransmission of the data packet. The one or more other sidelink resources indicated in the retransmission resource message may be different from the one or more second sidelink resources reserved for an initial transmission of the data packet.

In some examples, the sidelink transmission of the first reservation message may not include any data. In such an example, the one or more first sidelink resources may include the control portion (SCI-1 and/or SCI-2) and an empty or nearly empty data portion utilized for the reservation message on the one or more first sidelink resources. For example, the one or more first sidelink resources may include a small number of resources (e.g., one or two subchannels). Thus, the first reservation message may have a transmission bandwidth (e.g., 1 MHz to 2 MHz) that is smaller than the transmission bandwidth (e.g., 10 MHz) that may be used to transmit the data packet. In addition, the second UE704may transmit the first reservation message with robust coding.

At712, the first UE702may generate a reservation forwarding message including the first reservation message, or including an indication of the reserved resources identified in the first reservation message. In some aspects, in response to the first UE702receiving the first reservation message, the first UE702may measure a reference signal received power (RSRP) of the first reservation message. In some aspects, the first UE702may include the RSRP of the first reservation message in a reservation forwarding message. In some aspects, the first UE702may include an identification (identifier) of the second UE704in the first reservation forwarding message. The identification of the second UE704may be obtained from the SCI (e.g., SCI-2) or a MAC header if data is also transmitted with the first reservation message.

In some aspects, the first UE702may include a single bit in the first reservation forwarding message indicating to the third UE706that the first UE702is the intended recipient of the data packet (that may be transmitted on the one or more second sidelink resources). The single bit (Rx bit) may provide an indication to the third UE706that the third UE706is to abstain from transmitting (or more broadly, communicating) using the one or more second sidelink resources so that the first UE702may receive the data packet on the one or more second sidelink resources from the second UE704. Abstaining from transmission on the one or more second sidelink resources by the third UE706may aid in minimizing adverse conditions (e.g., interference) with reception of the data packet at the first UE702and may reduce the potential for a collision between transmissions of the second UE704and the third UE706. In some aspect, the first reservation message or the indication of the reserved resources in the first reservation message may be expressed as a single bit (e.g., in a bit map). Thus, a reservation forwarding message may include many reservation messages or many indications of the reserved resources in the many reservation messages, representing the reservations of many UEs.

In some aspects, the first UE702may identify a first collision associated with transmitting the first reservation message. For example, the first UE702may detect a collision when attempting to receive the first reservation message from the second UE704on the one or more first sidelink resources. The first UE702may detect a collision by comparing the RSRP value of the transmission of the first reservation message from the second UE704on the one or more first sidelink resources with a reference signal received quality (RSRQ) value of the transmission of the first reservation message from the second UE704on the one or more first sidelink resources. When the RSRP value is relatively high while the RSRQ value is relatively low, the first UE702may determine that a collision occurred during the transmission of the first reservation message from the second UE704to the first UE702on the one or more first sidelink resources. In this example, if the second UE704can still decode the first reservation message, the second UE704may determine to forward the first reservation message in a reservation forwarding message even when the data packet is not intended for the second UE704. For example, the second UE704may determine to transmit the first reservation forwarding message, including the first reservation message in response to detecting the first collision to ensure other UEs can receive and decode the first reservation message.

Similarly, in some aspects, the first UE702may identify a potential second collision associated with a second reservation message. For example, the first UE702may receive a second reservation message on one or more second sidelink resources from a fourth UE (e.g., a fourth UE608) indicating one or more second sidelink resources for transmitting a second data packet. In response to receiving the second reservation message from the fourth UE, the first UE702may detect a potential second collision between subsequent transmissions of the data packet and the second data packet. For example, the first UE702may determine that the one or more sidelink resources to be utilized for transmission of the data packet overlap in time and/or frequency with the one or more second sidelink resources to be utilized for transmission of the second data packet. In some examples, the first UE702may detect whether the potential second collision may occur at the first UE702by comparing the RSRP value of the second reservation message with the RSRP value of the first reservation message. In examples where the difference in RSRP values is high (e.g., above a threshold), the first UE702may determine that even if a collision occurs, the first UE702will still be able to decode the data packet from the second UE704. Therefore, the first UE702may not consider the potential second collision when forwarding the first reservation message.

In response to identifying the potential second collision, the first UE702may include an indication of the second collision in the first reservation forwarding message for reception by at least the third UE706. In some aspects, the indication of the second collision may be a single bit included in an SCI-2 or the PSSCH of the first reservation forwarding message. In some aspects, the first UE702may transmit the first reservation forwarding message as a broadcast message reaching a plurality of UEs including the second UE704, the third UE706, and the fourth UE. In this example, the first reservation forwarding message may further include an identifier (ID) of at least one of the second UE704or the fourth UE708, requesting that at least one of the second UE704or the fourth UE avoid the potential second collision (e.g., by changing the one or more sidelink resources for transmitting their respective data packets).

In addition to the first reservation message, as described herein, the first UE702may receive the second reservation message from the fourth UE708. As indicated above, the second reservation message may include an indication of the one or more second sidelink resources for a subsequent transmission of a second data packet from the fourth UE708. In the example, the first UE702may not be the intended recipient of the second data packet. In response to receiving the second reservation message, the first UE702may include an indication of the second reservation message in the first reservation forwarding message. In some examples, the first UE702may include the indication of the second reservation message in the first reservation forwarding message in response to detecting a collision, as described above. In other examples, the first UE702may include the indication of the second reservation message in the first reservation forwarding message for reception by at least the third UE706. In the example, in response to receiving the first reservation message from the second UE704and the second reservation message from the fourth UE708, the first UE702may include in the first reservation forwarding message a first at least one bit indicating that the first UE702is an intended recipient of the first data packet and a second at least one bit indicating that the first UE702is not the intended recipient of the second data packet.

The first reservation forwarding message may inform the third UE706of the reservation of the one or more second sidelink resources. The third UE706may utilize the first reservation forwarding message to determine, for example, whether to abstain from using the one or more second sidelink resources indicated in the first reservation message for a sidelink transmission. In some aspects, the first reservation forwarding message may be included in a data portion and/or a control portion of a sidelink transmission. In some aspects, the first reservation forwarding message may be included in a sidelink medium access control (MAC) control element (MAC-CE) and included in the data portion of the sidelink transmission. In some aspects, the first reservation forwarding message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink transmission. In some aspects, the first reservation forwarding message may be included in a sidelink radio resource control (RRC) message and included in the data portion of the sidelink transmission.

At714, the first UE702may transmit the first reservation forwarding message to the third UE706(or broadcast the first reservation forwarding message to all UEs in the system including the second UE704and the third UE706). The first reservation forwarding message transmission may occur on one or more third sidelink resources. The first reservation forwarding message may inform the third UE706(and any other UEs receiving the first reservation forwarding message) that the first UE702is the intended recipient of the data packet on one or more second sidelink resources (transmitted by the second UE704). In some aspects, the first UE702may transmit the first reservation forwarding message in a sidelink MAC-CE through a broadcast transmission on a physical sidelink shared channel (PSSCH). In some aspects, the first UE702may transmit the first reservation forwarding message to only the third UE706in a sidelink RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE702may transmit the first reservation forwarding message to at least the third UE706in SCI-2 on a physical sidelink control channel (PSCCH).

In some aspects, the first UE702may transmit the first reservation forwarding message to at least the third UE706using a relatively small transmission bandwidth (e.g., 1 MHz to 2 MHz) compared to the relatively larger transmission bandwidth of the data packet (e.g., about 10 MHz). In addition, the first UE702may transmit the first reservation forwarding message with robust coding.

As described herein, in response to the first UE702receiving the first reservation message, the first UE702may determine if the first UE702is an intended recipient of the first data packet. In some examples, in response to the first UE702receiving the first reservation message, the first UE702may obtain an RSRP value of the first reservation message. In other examples, the first UE702may determine if the first UE702is the intended recipient of the first data packet and obtain the RSRP value of the first reservation message. In some aspects, the first UE702may obtain the RSRP value by measurement. For example, the first UE702may measure a reference signal received power (RSRP) of the first reservation message. According to some examples, the first UE702may transmit the first reservation forwarding message, including the indication of the first reservation message, to the third UE706in response to at least one of: determining that the first UE702is the intended recipient of the first data packet, or determining that the RSRP value is less than the threshold value. Conversely, in response to at least one of: a determination that the first UE702is not the intended recipient of the first data packet or determining that the RSRP value is greater than a threshold value, the first UE702may abstain from transmitting the first reservation forwarding message, including the indication of the first reservation message to the third UE706.

In some aspects, the first UE702may transmit the first reservation forwarding message to at least the third UE706based on whether the first UE702receives a second reservation message or a second reservation forwarding message. For example, the second UE704may have transmitted the first reservation message to a plurality of UEs including the first UE702. In response to receiving the first reservation message from the second UE704, the first UE702may monitor for a second reservation message and/or a second reservation forwarding message from another UE. In response to receiving the first reservation message from the second UE704, the first UE702may initiate a timer. If the first UE702fails to receive the second reservation message and/or the second reservation forwarding message from another UE before the expiry of the timer, the first UE702may determine to transmit the first reservation forwarding message to at least the third UE706. Conversely, if the first UE702receives the second reservation message and/or the second reservation forwarding message from another UE before the expiry of the timer, the first UE702may determine not to transmit the first reservation forwarding message to the third UE706.

In some aspects, the first UE702may insert the indication of the first reservation message into a bit map and transmit the bit map in the first reservation forwarding message to at least the third UE706. In some aspects, the bit map may include a plurality of locations, each corresponding to a respective subchannel in a respective slot. The first UE702may insert the indication of the first reservation message into the bit map by inserting the indication of the first reservation message in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. Subsequently, the first UE702may transmit the bit map to at least the third UE706via the one or more forwarding sidelink resources. In some aspects, a bit of “0” in a location of the plurality of locations of the bit map may indicate that no resource reservation is allocated to the respective subchannel of the respective slot and a bit of “1” in the location of the bit map may indicate that at least one resource reservation is allocated to the respective subchannel in the respective slot.

In some aspects, each location of the plurality of locations of the bit map may include a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The resource reservation occupation level may be determined based on a reference signal received power (RSRP) associated with zero or more resource reservations of the respective subchannel in the respective slot. In some aspects, the zero or more resource reservations may include a plurality of resource reservations. The resource reservation occupation level of the respective subchannel in the respective slot may be determined, for example, to be given by at least one of: a sum of each RSRP for each resource reservation of the plurality of resource reservations or a maximum RSRP among the plurality of resource reservations. In some aspects, the bit map may include a width corresponding to a number of subchannels and a length corresponding to a number of slots.

At716, in response to receiving the first reservation forwarding message, the third UE706may abstain from using the one or more second sidelink resources. For example, the third UE706may receive the first reservation forwarding message from the first UE702and, based on the indication of the one or more second sidelink resources in the first reservation forwarding message, determine to abstain from transmitting (or more broadly, communicating) using the one or more second sidelink resources. In some aspects, the third UE706may abstain from using the one or more second sidelink resources based on the first reservation forwarding message including an indication of a collision between the transmission of the first reservation message and a transmission of a second reservation message. With the third UE706abstain from transmitting (or more broadly, communicating) on the one or more second sidelink resources indicated in the first reservation forwarding message, the second UE704may transmit the data packet to the first UE702with a reduced risk of a collision between transmissions.

In some aspects, the third UE706may mark the one or more sidelink resources as reserved with the corresponding priority of the data packet in response to receiving the first reservation forwarding message. In response to receiving the first reservation forwarding message from the first UE702and abstaining from transmitting using the one or more sidelink resources, the third UE706may select one or more different sidelink resources for transmitting data packets. For example, the third UE706may select one or more different sidelink resources for communication with the first UE702.

In some aspects, the third UE706may obtain a reference signal received power (RSRP) value of the first reservation forwarding message. In examples in which the first reservation forwarding message indicates that the first UE702intends to receive the data packet scheduled by the first reservation message (e.g., Rx bit=true), the third UE706may either abstain from using the one or more sidelink resources regardless of the RSRP value or in response to the RSRP value being greater than a threshold. In some aspects, the third UE706may receive the first reservation forwarding message that includes an identifier (ID) of the second UE704. In response to receiving the first reservation forwarding message that includes the ID of the second UE704, the third UE706may identify a stored reference signal received power (RSRP) value obtained for the second UE704from a previous transmission by the second UE704. The third UE706may abstain from transmitting on the one or more sidelink resources in response to the RSRP value being greater than a threshold value.

In some aspects, the third UE706may receive the first reservation forwarding message from the first UE702including a first RSRP value associated with the first reservation message from the second UE704. The third UE706may normalize the first RSRP value based on a difference between a first number of subchannels utilized for the first reservation message and a second number of subchannels associated with the one or more sidelink resources to produce a normalized RSRP value. In addition, the third UE706may further obtain a second RSRP value of the first reservation forwarding message. In examples in which the first reservation forwarding message does not indicate that the first UE702is the intended recipient of the data packet scheduled by the first reservation message, the third UE706may abstain from using the one or more sidelink resources based on determining that the second UE is a potential receiver of the first UE and abstaining from using the one or more sidelink resources regardless of the first RSRP value or the second RSRP value or in response to the second RSRP value being greater than a threshold. In some aspects, the third UE706may further abstain from using the one or more sidelink resources in response to a minimum RSRP value between the first RSRP value (or normalized RSRP value) and the second RSRP value being greater than the threshold regardless of whether the second UE is a potential receiver. In some aspects, the third UE706may receive the first reservation forwarding message from the first UE702including an identifier (ID) of the first UE. The third UE706may identify a stored RSRP value obtained for the second UE704from a previous transmission by the second UE704. The third UE706may abstain from transmitting on the one or more sidelink resources in response to the stored RSRP value being greater than a threshold value.

In some aspects, the first reservation forwarding message may include a bit map having a plurality of locations, each corresponding to a respective subchannel in a respective slot. The indication of the first reservation message may be included in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. In some aspects, the indication of the first reservation message may include a respective single bit in each of the at least one location in the bit map. In some aspects, each location of the plurality of locations may include a respective multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The third UE706may convert a multi-bit value of the multi-bit values in the at least one location to a corresponding RSRP value and may abstain from transmitting on the one or more sidelink resources based on the corresponding RSRP value. For example, the third UE706may abstain from using the one or more sidelink resources when the corresponding multi-bit RSRP value is greater than a threshold value or based on the minimum of the multi-bit RSRP value and the RSRP value of the first reservation forwarding message being above a threshold value.

In some aspects, the third UE706may receive at least one additional reservation forwarding message including the first reservation message, or the indication of the reserved resources in the first reservation message, from at least one additional UE via one or more additional forwarding sidelink resources. In this example, the third UE706may abstain from using the one or more sidelink resources based on a maximum reference signal received power (RSRP) value from a respective RSRP value associated with each of the first reservation forwarding message and the at least one additional reservation forwarding message. In one example, the third UE706may avoid using the resource identified in the first reservation forwarding message and the at least one additional reservation forwarding message if a given RSRP associated with any one of the first reservation forwarding message or any one of the at least one additional reservation forwarding message exceeded the minimum RSRP value.

At718, the second UE704may transmit the data packet to at least the first UE702using the one or more second sidelink resources. For example, the second UE704may transmit the data packet to the first UE702using the one or more second sidelink resources, while the third UE706abstains from communication using the one or more second sidelink resources. In some aspects, the second UE704may transmit the data packet to the first UE702and the third UE706using the one or more second sidelink resources.

FIG. 8is a block diagram illustrating an example of a hardware implementation of a first user equipment (UE)800(e.g., a first wireless communication device) employing a processing system814according to some aspects. For example, the first UE800may be any UE illustrated in any one or more ofFIGS. 1, 3, 6, and/or7. More particularly, the first UE800may be exemplified by the first UE602as shown and described in connection withFIG. 6, or the first UE702as shown and described in connection withFIG. 7.

In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system814that includes one or more processors, such as processor804. Examples of processor804include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the first UE800may be configured to perform any one or more of the functions described herein. That is, the processor804, as utilized in the first UE800, may be used to implement any one or more of the methods or processes described and illustrated, for example, inFIGS. 6, 7, and/or9-13.

The processor804may in some instances be implemented via a baseband or modem chip and in other implementations, the processor804may include a number of devices distinct and different from a baseband or modem chip (e.g., in such scenarios as may work in concert to achieve examples discussed herein). And as mentioned above, various hardware arrangements and components outside of a baseband modem processor can be used in implementations, including RF-chains, power amplifiers, modulators, buffers, interleavers, adders/summers, etc.

In this example, the processing system814may be implemented with a bus architecture, represented generally by the bus802. The bus802may include any number of interconnecting buses and bridges depending on the specific application of the processing system814and the overall design constraints. The bus802communicatively couples together various circuits including one or more processors (represented generally by the processor804) and computer-readable media (represented generally by the computer-readable medium806). The bus802may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, are not described any further.

A bus interface808provides an interface between the bus802and a transceiver810. The transceiver810may be, for example, a wireless transceiver. The transceiver810may provide a means for communicating with various other apparatus over a transmission medium (e.g., air interface). The transceiver810may further be coupled to one or more antennas/antenna arrays (not shown). The bus interface808further provides an interface between the bus802and a user interface812(e.g., keypad, display, touch screen, speaker, microphone, control features, etc.). Of course, such a user interface812may be omitted in some examples. In addition, the bus interface808further provides an interface between the bus802and a power source (not shown).

One or more processors, such as processor804, may be responsible for managing the bus802and general processing, including the execution of software stored on the computer-readable medium806. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures/processes, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on the computer-readable medium806. The software, when executed by the processor804, causes the processing system814to perform the various processes and functions described herein for any particular apparatus.

The computer-readable medium806may be a non-transitory computer-readable medium and may be referred to as a computer-readable storage medium or a non-transitory computer-readable medium herein. The non-transitory computer-readable medium may store computer-executable code (e.g., processor-executable code). The computer executable code may include code for causing a computer (e.g., a processor) to implement one or more of the functions described herein. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium806may reside in the processing system814, external to the processing system814, or distributed across multiple entities, including the processing system814. The computer-readable medium806may be embodied in a computer program product or article of manufacture. By way of example, a computer program product or article of manufacture may include a computer-readable medium in packaging materials. In some examples, the computer-readable medium806may be part of the memory805. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system. The computer-readable medium806and/or the memory805may also be used for storing data that may be manipulated by the processor804when executing software.

In some aspects of the disclosure, the processor804may include communication and processing circuitry840configured for various functions, including, for example, communicating with a network core (e.g., a 5G core network), one or more scheduling entities, scheduled entities, one or more TRPs (such as the first TRP821, the second TRP822, and/or the third TRP823through nth TRP824), and/or any other entity, such as, for example, local infrastructure or an entity communicating with the first UE800via the Internet, such as a network provider. According to some aspects, the various functions of the communication and processing circuitry840may be utilized to implement beam-specific timing precompensation as described herein.

In some examples, the communication and processing circuitry840may include one or more hardware components that provide the physical structure that performs processes related to wireless communication (e.g., signal reception and/or signal transmission) and signal processing (e.g., processing a received signal and/or processing a signal for transmission), as well as performs processes related to beam-specific timing precompensation processes as described herein. In addition, the communication and processing circuitry840may be configured to receive and process sidelink traffic and sidelink control. The communication and processing circuitry840may further be configured to execute communication and processing software850stored on the computer-readable medium806to implement one or more functions described herein.

The processor804may also include receiving circuitry841configured to receive a first reservation message from a second UE (e.g., second UE604ofFIG. 6, second UE704ofFIG. 7) via one or more first sidelink resources, the first reservation message may include a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The receiving circuitry841may further be configured to receive a transmission of the first data packet from the second UE via the one or more second sidelink resources. In some examples, the first reservation message may include at least one reservation of one or more other sidelink resources (different from the one or more first sidelink resources and the one or more second sidelink resources) for at least one retransmission of the first data packet, where the receiving the first data packet further includes receiving the at least one retransmission of the first data packet via the one or more other sidelink resources. In some examples, the receiving circuitry841may further be configured to receive a second reservation message from a fourth UE (e.g., the fourth UE608ofFIG. 6), where the second reservation message includes an indication of one or more fifth sidelink resources reserved by the fourth UE for receiving a second data packet from the fourth UE, and including the second reservation message or an indication of the one or more fifth sidelink resources reserved in the second reservation message in the first reservation forwarding message.

The first UE800may identify or determine that it is an intended recipient of the transmission of the first data packet, and may compare the RSRP associated with the first reservation message to a threshold value to determine if the first reservation message, or the resources indicated in the first reservation message, should be included in the first reservation forwarding message. If the first UE800is the intended recipient, the first UE may, according to some aspects, set a first at least one bit in the first reservation forwarding message to indicate that the first UE800is the intended recipient of the transmission of the first data packet.

The first reservation forwarding message may also include a second reservation message reserving resources for transmission of a second packet from another UE (or include an indication of the resources indicated in the second reservation message). The first UE800may set a second at least one bit in the first reservation forwarding message to indicate that the first UE800is also the intended recipient of second packet. For example, the second at least one bit may be set high if the second packet is intended for the first UE800or may be set low if the second packet is not intended for the first UE800. In some examples, the first at least one bit and the second at least one bit may not be included with the first reservation forwarding message. For example, the first at least one bit and the second at least one bit may not be included in the first reservation forwarding message if a network entity configures the first UE800to only transmit a reservation forwarding message if the first UE800is the intended recipient of a given data packet to be sent to the first UE800from any other UE (e.g., from the second UE). Additional parameters that may or may not be configured by the network entity to facilitate a decision, made at the first UE800, regarding whether to transmit the reservation forwarding message may include, for example, an RSRP value threshold.

According to some aspects, the first UE800may receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message may include a first indication of one or more second sidelink resources over which the first UE800may subsequently receive a first data packet from the second UE. In some examples, the first UE800may transmit a first reservation forwarding message including at least the first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources if the first reservation forwarding message is transmitted in response to the first UE being an intended recipient of the first data packet. In some examples, the first UE800may transmit the first reservation forwarding message including at least the first indication of the one or more second sidelink resources to at least the third UE via one or more third sidelink resources if the first reservation forwarding message is transmitted in response to an RSRP value being less than the threshold value. In still other examples, the first UE800may transmit the first reservation forwarding message including at least the first indication of the one or more second sidelink resources to at least the third UE via one or more third sidelink resources if both the first UE800is the intended recipient of the packet and the RSRP value is less than the threshold value. The receiving circuitry841may be configured to execute receiving instructions851stored in the computer-readable medium806to implement any of the one or more of the functions described herein.

The processor804may also include transmitting circuitry842configured to transmit a first reservation forwarding message comprising at least a first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources. In some examples, the one or more first sidelink resources and the one or more third sidelink resources may be fewer than the one or more second sidelink resources. According to some examples, the transmitting circuitry842may also be configured to transmit the first reservation forwarding message in response to the first UE800being an intended recipient of the first data packet. In some examples, the first reservation forwarding message may include a single bit having a value indicating that the first UE is an intended recipient of the first data packet. The transmitting circuitry842may further be configured to transmit the first reservation message via a sidelink control information (SCI) (e.g., an SCI-1 or SCI-2), sidelink medium access control (MAC) control element (MAC-CE), or a sidelink radio resource control (RRC) message. According to some examples, the transmitting circuitry842may be further configured to monitor, for a predetermined period of time following the receiving of the first reservation message, for at least one of: a second reservation message or a second reservation forwarding message including an indication of a reservation by another UE different from the second UE, of at least the one or more second sidelink resources, and configured to transmit the first reservation forwarding message in response to the expiry of the predetermined period of time in the absence of receiving the at least one of: the second reservation message or the second reservation forwarding message.

According to some aspects, transmitting the first reservation forwarding message to the at least the third UE (e.g., third UE606ofFIG. 6, third UE706ofFIG. 7) via the one or more third sidelink resources further include representing the indication of the one or more second sidelink resources in a bit map and transmitting the bit map to the at least the third UE via the one or more third sidelink resources. In some examples, the bit map may include a plurality of locations, each corresponding to a respective subchannel in a respective slot, and the representing the indication of the one or more second sidelink resources in the bit map may further include representing the indication of the one or more second sidelink resources in at least one location of the plurality of locations corresponding to the one or more second sidelink resources. In some examples, each location of the plurality of locations may include a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. In some aspects, the resource reservation occupation level of the respective subchannel in the respective slot may be determined based on a reference signal received power (RSRP) obtained from the respective subchannel in the respective slot. In some aspects, the bit map may include a width corresponding to a quantity of subchannels and a length corresponding to a quantity of slots.

According to some aspects, the transmitting the first reservation forwarding message to at least the third UE via the one or more third sidelink resources may further include transmitting the first reservation forwarding message via a second stage sidelink control information (SCI-2) to at least the third UE via the one or more third sidelink resources. The transmitting circuitry842may be configured to execute transmitting instructions852stored in the computer-readable medium806to implement any of the one or more of the functions described herein.

The processor804may further include identifying circuitry844configured to identify a collision associated with the transmitting of the first data packet from the second UE and a transmission of a second data packet by another UE (e.g., by the fourth UE, such as the fourth UE608ofFIG. 6). The identifying circuitry844may also be configured to execute identifying instructions854stored in the computer-readable medium806to implement any of the one or more of the functions described herein.

In addition, the processor804may include including circuitry846configured to include an indication of a prospective collision, or of an actual collision, in the first reservation forwarding message. The including circuitry846may also be configured to include in the reservation forwarding message identification (e.g., an identifier, an ID) of at least one of a second UE or a third UE to request the at least one of the second UE or the third UE to avoid the collision or to enable the at least one of the second UE or the third UE to avoid the collision by negotiation or by activation of a predetermined process for avoiding the collision. The including circuitry846may further be configured to include an indication of the second reservation message in the first reservation forwarding message. In addition, the including circuitry846may be configured to include the RSRP value(s) of the first reservation message and/or the second reservation message in the first reservation forwarding message. The including circuitry846may be configured to execute including instructions856stored in the computer-readable medium806to implement any of the one or more of the functions described herein.

The processor804may also include obtaining circuitry848configured to obtain a first RSRP value of the first reservation message received on the one or more first sidelink resources and/or a second RSRP value of the second reservation message received on the one or more fourth sidelink resources. The obtaining circuitry848may be configured to execute obtaining instructions858stored in the computer-readable medium806to implement any of the one or more of the functions described herein.

FIG. 9is a flow chart900of a method for forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the first UE800, as shown and described in connection withFIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block902, the first UE may receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message may include a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. For example, the receiving circuitry841, as shown and described in connection withFIG. 8, may provide a means for receiving a first reservation message from a second UE via one or more first sidelink resources, the first reservation message including a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink signal.

In some aspects, the first reservation message may indicate the one or more second sidelink resources that may have been selected by the second UE to transmit the first data packet. Therefore, the first reservation message may indicate to the first UE of the one or more second sidelink resources on which the first UE may receive the first data packet. For example, the indication may be expressed as a time and frequency location. For example, the time location may be expressed as a slot identifier (e.g., a slot ID) and the frequency location may be expressed as a resource block identifier (e.g., a resource block ID). Other ways to indicate (e.g., locate in the time and frequency domains) the one or more or more second sidelink resources are within the scope of the disclosure.

At block904, the first UE may transmit a first reservation forwarding message comprising at least a first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources. For example, the transmitting circuitry842, as shown and described in connection withFIG. 8, may provide a means for transmitting a first reservation forwarding message comprising at least an indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources. As described herein, the first reservation message or an indication of the resources reserved in the first reservation message may be included in a first sidelink resource forwarding message transmitted from the first UE to the third UE to inform the third UE to abstain from transmitting (or more broadly, communicating) on the one or more second sidelink resources indicated in the first reservation message to reduce the probability of a collision when the second UE transmits the first data packet to the first UE.

In some examples, the first reservation message may include a retransmission resource message. A retransmission resource message may include an indication of one or more sidelink resources that are to be used for a retransmission of the data packet if a collision occurs when initially transmitting the data packet or other conditions (e.g., interference) preventing the second UE from receiving and decoding the data packet. The one or more sidelink resources indicated in the retransmission resource message may include one or more different sidelink resources that are different from one or more sidelink resources used for initially transmitting the data packet.

The first UE may transmit the first reservation message to the second UE using one or more first sidelink resources. For example, the first UE may transmit the first reservation message to the second UE using one or more first sidelink resources to inform the second UE that the second UE is to receive a data packet on one or more sidelink resources from the first UE. In some examples, the first reservation message may be transmitted in SCI (e.g., SCI-1 and/or SCI-2) of a sidelink transmission. The one or more first sidelink resources may include a small number of resources (e.g., one or two subchannels).

At block906, the first UE may receive a transmission of the first data packet from the second UE via the one or more second sidelink resources. The first UE may decode the first data packet. For example, the receiving circuitry841may provide a means for receiving a transmission of the first data packet from the second UE via the one or more second sidelink resources.

FIG. 10is a flow chart1000of a method for forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the first UE, as shown and described in connection withFIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1002, the first UE may receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message may include a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving a first reservation message from a second UE via one or more first sidelink resources, the first reservation message including a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The second UE may generate a first reservation message including a first indication of one or more second sidelink resources for subsequently transmitting a first data packet (e.g., retransmission or a subsequent transmission). For example, the second UE may select one or more second sidelink resources to transmit the first packet. The selection of the one or more second sidelink resources for transmitting the first data packet may be based on, for example, availability of sidelink resources, a signal strength of the one or more sidelink resource, a signal quality of the one or more resources, a combination thereof, or the like. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal.

In some aspects, the first reservation message may indicate one or more second sidelink resources that are reserved by the second UE for subsequently transmitting the first data packet to one or more other UEs. For example, the second UE may transmit a first reservation message to the first UE to inform the first UE that the first UE is to receive a data packet in a subsequent transmission on one or more second sidelink resources. As described herein, the one or more second sidelink resources may be transmitted from the first UE to the third UE in a first reservation forwarding message to inform the third UE to abstain from transmitting (or more broadly, communicating) on the one or more second sidelink resources indicated in the reservation message to reduce the probability of a collision when the second UE transmits the first data packet to the first UE.

In some examples, the first reservation message may indicate a retransmission resource message. A retransmission resource message may include an indication of one or more sidelink resources that are to be used for a retransmission of the first data packet if a collision occurs when initially transmitting the first data packet or other conditions (e.g., interference) preventing the first UE from receiving and decoding the first data packet. The one or more sidelink resources indicated in the retransmission resource message may include one or more different sidelink resources that are different from one or more second sidelink resources used for initially transmitting the first data packet.

The second UE may transmit the first reservation message to the first UE using one or more first sidelink resources. For example, the second UE may transmit the first reservation message to the first UE using one or more first sidelink resources to inform the first UE that the first UE is to receive a data packet on one or more second sidelink resources from the second UE. In some examples, the first reservation message may be transmitted in an SCI (e.g., SCI-1 and/or SCI-2) of a sidelink transmission. The sidelink transmission may be, for example, the initial transmission of the first data packet when the first reservation message is a retransmission resource message. In this example, the one or more first sidelink resources may include the control portion (SCI-1 and/or SCI-2) and the data portion (PSSCH) utilized for the initial transmission. In this example, the one or more sidelink resources include the resources reserved and allocated to the one or more retransmissions. In some examples, the one or more first sidelink resources may include the control portion (SCI-1 and/or SCI-2) and the empty data portion utilized for the reservation message. For example, the one or more first sidelink resources may include a small number of resources (e.g., one or two subchannels).

At block1004, the first UE may identify a collision associated with transmitting the first data packet and an additional data packet by a fourth UE. For example, the identifying circuitry843may provide a means for identifying a collision associated with transmitting the first data packet and transmitting an additional data packet by a fourth UE. For example, the first UE may detect a collision when attempting to receive the first reservation message from the second UE on the one or more first sidelink resources. The first UE may detect a collision by comparing the RSRP value of the transmission of the first reservation message from the second UE on the one or more first sidelink resources with a reference signal received quality (RSRQ) value of the transmission of the first reservation message from the second UE on the one or more first sidelink resources. When the RSRP value is relatively high while the RSRQ value is relatively low, the first UE may determine that a collision occurred during the transmission of the first reservation message from the second UE to the first UE on the one or more first sidelink resources. In this example, if the second UE can still decode the first reservation message, the second UE may determine to forward the first reservation message in a reservation forwarding message even when the data packet is not intended for the second UE. For example, the second UE may determine to transmit the reservation forwarding message including the first reservation message in response to detecting the first collision to ensure other UEs can receive and decode the first reservation message.

Similarly, in some aspects, the first UE may identify a potential second collision associated with a second reservation message. For example, the first UE may receive a second reservation message on one or more second sidelink resources from a fourth UE indicating one or more second sidelink resources for transmitting a second data packet. In response to the first UE receiving the second reservation message from the fourth UE, the first UE may detect a potential second collision between subsequent transmissions of the data packet and the second data packet. For example, the first UE may determine that the one or more sidelink resources to be utilized for transmission of the data packet overlap in time and/or frequency with the one or more second sidelink resources to be utilized for transmission of the second data packet. In some examples, the first UE may detect whether the potential second collision may occur at the first UE by comparing the RSRP value of the second reservation message with the RSRP value of the first reservation message. In examples where the difference in RSRP values is high (e.g., above a threshold), the first UE may determine that even if a collision occurs, the first UE will still be able to decode the data packet from the second UE. Therefore, the first UE may not consider the potential second collision when forwarding the first reservation message.

At block1006, the first UE may include an indication of the collision in a reservation forwarding message that includes the first reservation message. For example, the including circuitry844may provide a means for including an indication of the collision in a reservation forwarding message that includes the first reservation message. For example, in response to identifying the potential second collision, the first UE may include an indication of the second collision in the reservation forwarding message for reception by at least the third UE. In some aspects, the indication of the second collision may be a single bit included in an (SCI-2) or the PSSCH of the reservation forwarding message. In some aspects, the first UE may transmit the reservation forwarding message as a broadcast message reaching a plurality of UEs including the second UE, the third UE, and the fourth UE. In this example, the reservation forwarding message may further include an identifier (ID) of at least one of the second UE or the fourth UE, requesting that at least one of the second UE or the fourth UE avoid the potential second collision (e.g., by changing the one or more sidelink resources for transmitting their respective data packets).

In addition to the first reservation message, as described herein, the first UE may receive the second reservation message from the fourth UE. As indicated above, the second reservation message may include an indication of the one or more second sidelink resources for a subsequent transmission of a second data packet from the fourth UE. In response to receiving the second reservation message, the first UE may include an indication of the second reservation message in the reservation forwarding message. In some examples, the first UE may include the indication of the second reservation message in the reservation forwarding message in response to detecting a collision, as described above. In other examples, the first UE may include the indication of the second reservation message in the reservation forwarding message for reception by at least the third UE. In some aspects, in response to receiving the first reservation message from the second UE and the second reservation message from the fourth UE, the first UE may include in the reservation forwarding message a first bit indicating that the first UE intends to receive the first data packet and that the first UE does not intend to receive the second data packet.

At block1008, the first UE may transmit the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources. For example, the transmitting circuitry842, as shown and described in connection withFIG. 8, may provide a means for transmitting the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources. For example, the first UE may transmit the reservation forwarding message to the third UE and/or the fourth UE using one or more forwarding sidelink resources. For example, the first UE may transmit the reservation forwarding message to the third UE and/or the fourth UE using one or more forwarding sidelink resources to inform the third UE and/or the fourth UE that the first UE is to receive a data packet on one or more sidelink resources from the second UE. In some aspects, the first UE may transmit the reservation forwarding message to the third UE and one or more other UEs (e.g., the fourth UE) in a MAC-CE through a broadcast transmission on a physical sidelink shared channel (PSSCH). In some aspects, the first UE may transmit the reservation forwarding message to only the third UE in an RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE in SCI-2 on a physical sidelink control channel (PSCCH).

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE based on whether the first UE receives a reservation forwarding message. For example, the second UE may have transmitted the first reservation message to a plurality of UEs including the first UE. In response to receiving the first reservation message from the second UE, the first UE may monitor for another reservation forwarding message from another UE of the plurality of UEs including the indication of the first reservation message. The first UE may initiate a timer in response to receiving the first reservation message from the second UE. If the first UE fails to receive the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine to transmit the reservation forwarding message to the third UE. Conversely, if the first UE receives the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine not to transmit the reservation forwarding message to the third UE.

In some aspects, the first UE may insert the indication of the first reservation message into a bit map and transmit the bit map in the reservation forwarding message to at least the third UE. In some aspects, the bit map may include a plurality of locations, each corresponding to a respective subchannel in a respective slot. The first UE may insert the indication of the first reservation message into the bit map by inserting the indication of the first reservation message in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. Subsequently, the first UE may transmit the bit map to at least the third UE via the one or more forwarding sidelink resources. In some aspects, a bit of “0” in a location of the plurality of locations of the bit map may indicate that no resource reservation is allocated to the respective subchannel of the respective slot and a bit of “1” in the location of the bit map may indicate that at least one resource reservation is allocated to the respective subchannel in the respective slot.

In some aspects, each location of the plurality of locations of the bit map may include a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The resource reservation occupation level may be determined based on a reference signal received power (RSRP) associated with zero or more resource reservations of the respective subchannel in the respective slot. In some aspects, the zero or more resource reservations may include a plurality of resource reservations. The resource reservation occupation level of the respective subchannel in the respective slot may be determined, for example, to be given by at least one of: a sum of each RSRP for each resource reservation of the plurality of resource reservations or a maximum RSRP among the plurality of resource reservations. In some aspects, the bit map may include a width corresponding to a number of subchannels and a length corresponding to a number of slots.

In response to receiving the reservation forwarding message, the third UE may abstain from using the one or more sidelink resources for communication thereon. For example, the third UE may receive the reservation forwarding message from the first UE and, based on the indication of the one or more sidelink resources in the first reservation message contained in the reservation forwarding message, the third UE may determine to abstain from transmitting (or more broadly, communicating) using the one or more sidelink resources. In some aspects, the third UE may abstain from using the one or more sidelink resources based on the reservation forwarding message including an indication of a collision between the transmission of the first reservation message and a transmission of a second reservation message. With the third UE abstaining from transmitting (or more broadly, communicating) of the one or more sidelink resources indicated in the reservation forwarding message, the second UE may transmit the data packet to the first UE with a reduced risk of a collision between transmissions.

In some aspects, the third UE may mark the one or more sidelink resources as reserved with the corresponding priority of the data packet in response to receiving the reservation forwarding message. In response to receiving the reservation forwarding message from the first UE and abstaining from communication using the one or more sidelink resources, the third UE may select one or more different sidelink resources for transmitting data packets. For example, the third UE may select one or more different sidelink resources for communication with the first UE.

In some aspects, the third UE may obtain a reference signal received power (RSRP) value of the reservation forwarding message. In examples in which the reservation forwarding message indicates that the first UE intends to receive the data packet scheduled by the first reservation message (e.g., Rx bit=true), the third UE may either abstain from using the one or more sidelink resources regardless of the RSRP value or in response to the RSRP value being greater than a threshold. In some aspects, the third UE may receive the reservation forwarding message that includes an identifier (ID) of the second UE. In response to receiving the reservation forwarding message that includes the ID of the second UE, the third UE may identify a stored reference signal received power (RSRP) value obtained for the second UE from a previous transmission from the second UE, and abstain from using the one or more sidelink resources in response to the RSRP value being greater than a threshold.

In some aspects, the third UE may receive the reservation forwarding message from the first UE including a first RSRP value associated with the first reservation message from the second UE. The third UE may normalize the first RSRP value based on a difference between a first number of subchannels utilized for the first reservation message and a second number of subchannels associated with the one or more sidelink resources to produce a normalized RSRP value. In addition, the third UE may further obtain a second RSRP value of the reservation forwarding message. In examples in which the reservation forwarding message does not indicate that the first UE intends to receive (e.g., is the intended recipient of) the data packet scheduled by the first reservation message, the third UE may abstain from using the one or more sidelink resources based on determining that the first UE is a potential receiver of the second UE and abstaining from using the one or more sidelink resources regardless of the first RSRP value or the second RSRP value or in response to the second RSRP value being greater than a threshold. In some aspects, the third UE may further abstain from using the one or more sidelink resources in response to a minimum RSRP value between the first RSRP value (or normalized RSRP value) and the second RSRP value being greater than the threshold regardless of whether the first UE is a potential receiver. In some aspects, the third UE may receive the reservation forwarding message from the first UE including an identifier (ID) of the second UE. The third UE may identify a stored RSRP value obtained from a previous transmission from the second UE and may abstain from transmitting on one or more sidelink resources in response to the stored RSRP value being greater than a threshold value.

In some aspects, the reservation forwarding message may include a bit map having a plurality of locations, each corresponding to a respective subchannel in a respective slot. The indication of the first reservation message may be included in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. In some aspects, the indication of the first reservation message may include a respective single bit in each of the at least one location in the bit map. In some aspects, each location of the plurality of locations may include a respective multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The third UE may convert a multi-bit value of the multi-bit values in the at least one location to a corresponding RSRP value and abstain from transmitting on the one or more sidelink resources based on the corresponding RSRP value. For example, the third UE may abstain from using the one or more sidelink resources when the corresponding multi-bit RSRP value is greater than a threshold value or based on the minimum of the multi-bit RSRP value and the RSRP value of the reservation forwarding message being above a threshold value.

In some aspects, the third UE may receive at least one additional reservation forwarding message including the first reservation message, or an indication of the resources reserved by the first reservation message, from at least one additional UE via one or more additional forwarding sidelink resources. In this example, the third UE may abstain from using the one or more sidelink resources based on a maximum reference signal received power (RSRP) value in the same or similar way that the third UE606ofFIG. 6abstained from using the one or more sidelink resources.

At block1010, the first UE may receive the first data packet from the second UE via the one or more second sidelink resources. For example, the receiving circuitry841as shown and described in connection withFIG. 8, may provide a means for receiving the first data packet from the second UE via the one or more second sidelink resources. For example, the second UE may transmit the data packet to the first UE using the one or more sidelink resources, while the third UE abstains from transmitting on the one or more sidelink resources. In some aspects, the second UE may transmit the data packet to the first UE and the third UE using the one or more second sidelink resources.

FIG. 11is a flow chart1100of a method for forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the first UE, as described above, and illustrated inFIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1102, the first UE may receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message may include an indication of one or more sidelink resources for subsequently receiving a data packet from the second UE. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving a first reservation message from a first user equipment (UE) via one or more first sidelink resources, the first reservation message including an indication of one or more sidelink resources for subsequently receiving a data packet from the first UE. For example, the second UE may select one or more sidelink resources for transmitting the data packet. The selection of the one or more sidelink resources for transmitting the data packet may be based on, for example, availability of sidelink resources, a signal strength of the one or more sidelink resource, a signal quality of the one or more resources, a combination thereof, or the like. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal.

The first reservation message may include a retransmission resource message. A retransmission resource message may include an indication of one or more sidelink resources that are to be used for a retransmission of the data packet if a collision occurs when initially transmitting the data packet or other conditions (e.g., interference) occur that prevent the first UE from receiving and decoding the data packet. The one or more sidelink resources indicated in the retransmission resource message may include one or more different sidelink resources that are different from one or more sidelink resources used for initially transmitting the data packet.

The first UE may generate a reservation forwarding message including the first reservation message, or an indication of the resources reserved by the first reservation message. For example, the first UE may generate a reservation forwarding message including the first reservation message, or an indication of the resources indicated in the first reservation message, for transmission to the third UE to inform the third UE of the subsequent sidelink transmission. The third UE may then utilize the reservation forwarding message to determine whether to abstain from using the one or more sidelink resources indicated in the first reservation message for a sidelink transmission. In some aspects, the reservation forwarding message may be included a data portion and/or a control portion of a sidelink transmission. In some aspects, the reservation forwarding message may be included in a medium access control (MAC) control element (MAC-CE) and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a radio resource control (RRC) message and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink transmission.

In some aspects, the first UE may include a single bit in the reservation forwarding message indicating to the third UE that the first UE intends to receive the data packet using the one or more sidelink resources. The single bit (Rx bit) may provide an indication to the third UE that the third UE is to abstain from transmitting (or more broadly, communicating) using the one or more sidelink resources so that the first UE may receive the data packet on the one or more sidelink resources from the second UE while minimizing interference and the potential for a collision from a transmission conducted by the third UE.

At block1104, the first UE may identify a collision associated with the transmitting of the data packet and a transmission of an additional data packet by a fourth UE. For example, the identifying circuitry843may provide a means for identifying a collision associated with the transmitting of the data packet and a transmission of an additional data packet by a fourth UE. For example, the first UE may detect a collision when attempting to receive the first reservation message from the second UE on the one or more first sidelink resources. The first UE may detect a collision by comparing the RSRP value of the transmission of the first reservation message from the second UE on the one or more first sidelink resources with a reference signal received quality (RSRQ) value of the transmission of the first reservation message from the second UE on the one or more first sidelink resources. When the RSRP value is relatively high while the RSRQ value is relatively low, the first UE may determine that a collision occurred during the transmission of the first reservation message from the second UE to the first UE on the one or more first sidelink resources. In this example, if the second UE can still decode the first reservation message, the second UE may determine to forward the first reservation message in a reservation forwarding message even when the data packet is not intended for the second UE. For example, the second UE may determine to transmit the reservation forwarding message including the first reservation message in response to detecting the first collision to ensure other UEs can receive and decode the first reservation message.

Similarly, in some aspects, the first UE may identify a potential second collision associated with a second reservation message. For example, the first UE may receive a second reservation message on one or more second sidelink resources from a fourth UE indicating one or more second sidelink resources for transmitting a second data packet. In response to receiving the second reservation message from the fourth UE, the first UE may detect a potential second collision between subsequent transmissions of the data packet and the second data packet. For example, the first UE may determine that the one or more sidelink resources to be utilized for transmission of the data packet overlap in time and/or frequency with the one or more second sidelink resources to be utilized for transmission of the second data packet. In some examples, the first UE may detect whether the potential second collision may occur at the first UE by comparing the RSRP value of the second reservation message with the RSRP value of the first reservation message. In examples where the difference in RSRP values is high (e.g., above a threshold), the first UE may determine that even if a collision occurs, the first UE will still be able to decode the data packet from the second UE. Therefore, the first UE may not consider the potential second collision when forwarding the first reservation message.

At block1106, the first UE may include an indication of the collision in a reservation forwarding message that includes the first reservation message, and, at block1108, the first UE may include an identifier (ID) of at least one of the second UE or the fourth UE to request that at least one of the second UE or the fourth UE avoid the collision. For example, the including circuitry844as shown and described in connection withFIG. 8may provide a means for including an indication of the collision in a reservation forwarding message that includes the first reservation message and including an identifier (ID) of at least one of the second UE or the fourth UE to request that at least one of the second UE or the fourth UE avoid the collision. For example, in response to identifying the potential second collision, the first UE may include an indication of the second collision in the reservation forwarding message for reception by at least the third UE. In some aspects, the indication of the second collision may be a single bit included in an SCI-2 or the PSSCH of the reservation forwarding message. In some aspects, the first UE may transmit the reservation forwarding message as a broadcast message reaching a plurality of UEs, including the second UE, the third UE, and the fourth UE. In this example, the reservation forwarding message may further include an identifier (ID) of at least one of the second JE or the fourth UE, requesting that at least one of the second UE or the fourth UE avoid the potential second collision (e.g., by changing the one or more sidelink resources for transmitting their respective data packets).

In addition to the first reservation message, as described herein, the first UE may receive the second reservation message from the fourth UE. As indicated above, the second reservation message may include an indication of the one or more second sidelink resources for a subsequent transmission of a second data packet from the fourth UE. In response to receiving the second reservation message, the first UE may include an indication of the second reservation message in the reservation forwarding message. In some examples, the first UE may include the indication of the second reservation message in the reservation forwarding message in response to detecting a collision, as described above. In other examples, the first UE may include the indication of the second reservation message in the reservation forwarding message for reception by at least the third UE. In some aspects, in response to receiving the first reservation message from the second UE and the second reservation message from the fourth UE, the first UE may include in the reservation forwarding message a first bit indicating that the first UE intends to receive the first data packet and that the first UE does not intend to receive the second data packet.

At block1110, the first UE may transmit the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources. For example, the transmit circuitry842as shown and described in connection withFIG. 8may provide a means for transmitting the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources. For example, the first UE may transmit the reservation forwarding message to the third UE and/or the fourth UE using one or more forwarding sidelink resources to inform the third UE and/or the fourth UE that the first UE is to receive a data packet on one or more sidelink resources from the second UE. In some aspects, the first UE may transmit the reservation forwarding message to the third UE and one or more other UEs (e.g., the fourth UE) in a MAC-CE through a broadcast transmission on a physical sidelink shared channel (PSSCH). In some aspects, the first UE may transmit the reservation forwarding message to only the third UE in an RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE in SCI-2 on a physical sidelink control channel (PSCCH).

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE using a smaller transmission bandwidth (e.g., 1 MHz to 2 MHz) than the transmission bandwidth (e.g., 10 MHz) that may be used to transmit the data packet. In addition, the first UE may transmit the reservation forwarding message with robust coding. A relatively larger transmission compared to a relatively smaller transmission has a higher modulation order and higher coding and decoding rates, thereby decreasing transmission reliability. In combination with the robust coding, the smaller transmission bandwidth may increase the likelihood of at least the third UE receiving and decoding the reservation forwarding message while minimizing the potential for wasting relatively larger amounts of the bandwidth during the occurrence of a collision. For example, the one or more forwarding sidelink resources used to transmit the reservation forwarding message from the first UE to at least the third UE may include fewer resources than the one or more sidelink resources for transmitting the data packet from the second UE to at least the first UE.

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE based on whether the first UE receives a reservation forwarding message. For example, the second UE may have transmitted the first reservation message to a plurality of UEs, including the first UE. In response to receiving the first reservation message from the second UE, the first UE may monitor for another reservation forwarding message from another UE of the plurality of UEs, including the indication of the first reservation message. The first UE may initiate a timer in response to receiving the first reservation message from the second UE. If the first UE fails to receive the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine to transmit the reservation forwarding message to the third UE. Conversely, if the first UE receives the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine not to transmit the reservation forwarding message to the third UE.

At block1112, the first UE may receive the data packet from the second UE via the one or more sidelink resources. For example, the receiving circuitry841, as shown and described in connection withFIG. 8, may provide a means for receiving the data packet from the second UE via the one or more sidelink resources. For example, the second UE may transmit the data packet to the first UE using the one or more sidelink resources, while the third UE abstains from transmitting on the one or more sidelink resources. In some aspects, the second UE may transmit the data packet to the first UE and the third UE using the one or more sidelink resources.

FIG. 12is a flow chart1200of a method for forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the first UE, as described above, and illustrated inFIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1202, the first UE may receive a first reservation message from a second UE via one or more first sidelink resources. The first reservation message may include a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving a first reservation message from a second user equipment (UE) via one or more first sidelink resources, the first reservation message including the first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal.

At block1204, the first UE may receive a second reservation message from a fourth UE via one or more fourth sidelink resources. The second reservation message may include a second indication of one or more fifth sidelink resources for subsequently receiving a second data packet from the fourth UE. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving a second reservation message from a fourth UE via one or more fourth sidelink resources, the second reservation message including an indication of one or more fifth sidelink resources for subsequently receiving a second data packet from the fourth UE.

At block1206, the first UE may include the first indication of the one or more second sidelink resources and the second indication of the one or more fifth sidelink resources in a reservation forwarding message. For example, the including circuitry844as shown and described in connection withFIG. 8may provide a means for including the indication of the one or more second sidelink resources and the one or more fifth sidelink resources in a reservation forwarding message.

As indicated above, in response to receiving the second reservation message, the first UE may include an indication of the second reservation message in the reservation forwarding message. In some examples, the first UE may include the indication of the second reservation message in the reservation forwarding message in response to detecting a collision, as described above. In other examples, the first UE may include the indication of the second reservation message in the reservation forwarding message for reception by at least the third UE. In some aspects, in response to receiving the first reservation message from the second UE and the second reservation message from the fourth UE, the first UE may include in the reservation forwarding message a first bit indicating that the first UE is an intended recipient of the first data packet and not an intended recipient of the second data packet.

At block1208, the first UE may transmit the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources (e.g., via one or more third sidelink resources). For example, the first UE may transmit the reservation forwarding message to at least the third UE using a relatively small transmission bandwidth (e.g., 1 MHz to 2 MHz) compared to the relatively larger transmission bandwidth (e.g., 10 MHz) utilized for transmission of the first data packet. In addition, the first UE may transmit the reservation forwarding message with robust coding. A relatively larger transmission bandwidth of the transmission of the data packet (compared to a relatively smaller transmission bandwidth of the reservation message) has a higher modulation order and higher coding and decoding rates, thereby decreasing transmission reliability. In combination with the robust coding, the smaller transmission bandwidth may increase the likelihood of at least the third UE receiving and decoding the reservation forwarding message while minimizing the potential for wasting relatively larger amounts of the bandwidth during the occurrence of a collision. For example, the one or more forwarding sidelink resources used to transmit the reservation forwarding message from the first UE to at least the third UE may include fewer resources than the one or more sidelink resources used to transmit the data packet from the second UE to at least the first UE.

As described herein, in response to the first UE receiving the first reservation message, the first UE may obtain an RSRP value of the first reservation message. For example, the first UE may measure a reference signal received power (RSRP) of the first reservation message. In some aspects, the first UE may include the RSRP of the first reservation message in the reservation forwarding message. In some aspects, in response to obtaining an RSRP value of the first reservation message, the first UE may compare the RSRP value with a threshold value. When the RSRP value is less than a threshold value, the first UE may transmit the reservation forwarding message, including the indication of the first reservation message to the third UE. Conversely, when the RSRP value is greater than a threshold value, the first UE may abstain from transmitting the reservation forwarding message, including the indication of the first reservation message to the third UE.

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE based on whether the first UE receives a reservation forwarding message. For example, the second UE may have transmitted the first reservation message to a plurality of UEs, including the first UE. In response to receiving the first reservation message from the second UE, the first UE may monitor for another reservation forwarding message from another UE of the plurality of UEs, including the indication of the first reservation message. The first UE may initiate a timer in response to receiving the first reservation message from the second UE. If the first UE fails to receive the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine to transmit the reservation forwarding message to the third UE. Conversely, if the first UE receives the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine not to transmit the reservation forwarding message to the third UE.

In some aspects, the first UE may insert the indication of the first reservation message into a bit map and transmit the bit map in the reservation forwarding message to at least the third UE. In some aspects, the bit map may include a plurality of locations, each corresponding to a respective subchannel in a respective slot. The first UE may insert the indication of the first reservation message into the bit map by inserting the indication of the first reservation message in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. Subsequently, the first UE may transmit the bit map to at least the third UE via the one or more forwarding sidelink resources. In some aspects, a bit of “0” in a location of the plurality of locations of the bit map may indicate that no resource reservation is allocated to the respective subchannel of the respective slot and a bit of “1” in the location of the bit map may indicate that at least one resource reservation is allocated to the respective subchannel in the respective slot.

In some aspects, each location of the plurality of locations of the bit map may include a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The resource reservation occupation level may be determined based on a reference signal received power (RSRP) associated with zero or more resource reservations of the respective subchannel in the respective slot. In some aspects, the zero or more resource reservations may include a plurality of resource reservations. The resource reservation occupation level of the respective subchannel in the respective slot may be determined, for example, to be given by at least one of: a sum of each RSRP for each resource reservation of the plurality of resource reservations or a maximum RSRP among the plurality of resource reservations. In some aspects, the bit map may include a width corresponding to a number of subchannels and a length corresponding to a number of slots.

In some aspects, the reservation forwarding message may include a bit map having a plurality of locations, each corresponding to a respective subchannel in a respective slot. The indication of the first reservation message may be included in at least one location of the plurality of locations of the bit map corresponding to the one or more sidelink resources. In some aspects, the indication of the first reservation message may include a respective single bit in each of the at least one location in the bit map. In some aspects, each location of the plurality of locations may include a respective multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot. The third UE may convert a multi-bit value of the multi-bit values in the at least one location to a corresponding RSRP value and abstain from transmitting on the one or more sidelink resources based on the corresponding RSRP value. For example, the third UE may abstain from using the one or more sidelink resources when the corresponding multi-bit RSRP value is greater than a threshold value or based on the minimum of the multi-bit RSRP value and the RSRP value of the reservation forwarding message being above a threshold value.

At block1210, the first UE may receive the first data packet from the second UE via the one or more second sidelink resources and/or the second data packet from the fourth UE via the one or more fifth sidelink resources. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving the first data packet from the first UE via the one or more second sidelink resources and/or the second data packet from the fourth UE via the one or more fifth sidelink resources.

FIG. 13is a flow chart1300of a method for forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the first UE, as described above, and illustrated inFIG. 8, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1302, the first UE may receive a reservation message from a second UE via one or more first sidelink resources. The reservation message may include an indication of one or more sidelink resources for subsequently receiving a data packet from the second UE. For example, the receiving circuitry841as shown and described in connection withFIG. 8may provide a means for receiving a reservation message from a second user equipment (UE) via one or more first sidelink resources, the first reservation message including a first indication of one or more second sidelink resources for subsequently receiving a data packet from the second UE. For example, the second UE may select one or more second sidelink resources for transmitting the data packet. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal.

At block1304, the first UE may obtain a reference signal received power (RSRP) value of the reservation message received on the one or more first sidelink resources. For example, the obtaining circuitry845as shown and described in connection withFIG. 8may provide a means for obtaining a reference signal received power (RSRP) value of the reservation message received on the one or more first sidelink resources.

At block1306, the first UE may include the RSRP value in a reservation forwarding message that also includes the reservation message. For example, the including circuitry844as shown and described in connection withFIG. 8may provide a means for including the RSRP value in a reservation forwarding message, the reservation forwarding message also including the reservation message. In some aspects, in response to the first UE receiving the first reservation message, the first UE may measure a reference signal received power (RSRP) of the first reservation message. In some aspects, the first UE may include the RSRP of the first reservation message in a reservation forwarding message, described herein. In some aspects, the first UE may further include an identification (identifier) of the second UE in the reservation forwarding message, described herein. The identifier of the second UE may be obtained from SCI (e.g., SCI-2) or a MAC header if data is also received with the first reservation message.

At block1308, the first UE may transmit (e.g., broadcast) the reservation forwarding message to at least a third UE via one or more forwarding sidelink resources. For example, the transmitting circuitry842, as shown and described in connection withFIG. 8, may provide a means for transmitting the reservation forwarding message to at least a third UE via one or more forwarding resources. For example, the first UE may transmit the reservation forwarding message, including the indication of the first reservation message, to the third UE to inform the third UE of the subsequent sidelink transmission. In some aspects, the reservation forwarding message may be included a data portion and/or a control portion of a sidelink transmission. In some aspects, the reservation forwarding message may be included in a medium access control (MAC) control element (MAC-CE) and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a radio resource control (RRC) message and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink transmission. In some aspects, the reservation forwarding message may have a portion transmitted using SCI-2 and another portion transmitted using a MAC-CE.

The first UE may transmit the reservation forwarding message to the third UE and/or the fourth UE using one or more forwarding sidelink resources. For example, the first UE may transmit the reservation forwarding message to the third UE and/or the fourth UE using one or more forwarding sidelink resources to inform the third UE and/or the fourth UE that the first UE is to receive a data packet on one or more sidelink resources from the second UE. In some aspects, the first UE may transmit the reservation forwarding message to the third UE and one or more other UEs (e.g., the fourth UE) in a MAC-CE through a broadcast transmission on a physical sidelink shared channel (PSSCH). In some aspects, the first UE may transmit the reservation forwarding message to only the third UE in an RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE in SCI-2 on a physical sidelink control channel (PSCCH).

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE with a transmission bandwidth (e.g., 1 MHz to 2 MHz) that is less than the transmission bandwidth (e.g., 10 MHz) that may be used to transmit the data packet. In addition, the first UE may transmit the reservation forwarding message with robust coding. A relatively larger transmission compared to a relatively smaller transmission has a higher modulation order and higher coding and decoding rates, thereby decreasing transmission reliability. In combination with the robust coding, the smaller transmission bandwidth may increase the likelihood of at least the third UE receiving and decoding the reservation forwarding message while minimizing the potential for wasting relatively larger amounts of the bandwidth during the occurrence of a collision. For example, the one or more forwarding sidelink resources used to transmit the reservation forwarding message from the first UE to at least the third UE may include fewer resources than the one or more sidelink resources for transmitting the data packet from the second UE to at least the first UE.

In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE based on whether the first UE receives a reservation forwarding message. For example, the second UE may have transmitted the first reservation message to a plurality of UEs, including the first UE. In response to receiving the first reservation message from the second UE, the first UE may monitor for another reservation forwarding message from another UE of the plurality of UEs, including the indication of the first reservation message. The first UE may initiate a timer in response to receiving the first reservation message from the second UE. If the first UE fails to receive the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine to transmit the reservation forwarding message to the third UE. Conversely, if the first UE receives the other reservation forwarding message from another UE of the plurality of UEs before the timer expires, the first UE may determine not to transmit the reservation forwarding message to the third UE.

At block1310, the first UE may receive the first data packet from the second UE via the one or more second sidelink resources. For example, the receiving circuitry841, as shown and described in connection withFIG. 8, may provide a means for receiving the data packet from the second UE via the one or more second sidelink resources.

FIG. 14is a block diagram illustrating an example of a hardware implementation of a second user equipment (UE) (e.g., a second wireless communication device)1400employing a processing system1414. For example, the second UE1400may be any of the UEs as shown and described in connection with any ofFIGS. 1, 3, 6, and/or7. In particular, the second UE1400may be exemplified by the second UE604as shown and described in connection withFIG. 6and/or the second UE704as shown ad described in connection withFIG. 7.

In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system1414that includes one or more processors1404. The processing system1414may be substantially the same as the processing system814illustrated inFIG. 8, including a bus interface1408, a bus1402, a processor1404, and a computer-readable medium1406. Furthermore, the second UE1400may include a user interface1412and a transceiver1410substantially similar to those described herein inFIG. 8. That is, the processor1404, as utilized in the second UE1400, may be used to implement any one or more of the processes described herein.

In some aspects of the disclosure, the processor1404may include communication and processing circuitry1440configured for various functions, including, for example, communicating with a network core (e.g., a 5G core network), one or more scheduling entities, one or more other UEs via sidelink, and/or any other entity, such as, for example, local infrastructure or an entity communicating with the second UE1400via the Internet, such as a network provider. According to some aspects, the various functions of the communication and processing circuitry1440may implement resource reservation forwarding procedures as described herein.

In some examples, the communication and processing circuitry1440may include one or more hardware components that provide the physical structure that performs processes related to wireless communication (e.g., signal reception and/or signal transmission) and signal processing (e.g., processing a received signal and/or processing a signal for transmission), as well as performs processes related to beam-specific timing precompensation processes as described herein. In addition, the communication and processing circuitry1440may be configured to receive and process sidelink traffic and sidelink control. The communication and processing circuitry1440may further be configured to execute communication and processing software1450stored on the computer-readable medium1406to implement one or more functions described herein.

The processor1404may include circuitry configured for various functions in some aspects of the disclosure. For example, the processor1404may include selecting circuitry1441configured to select one or more sidelink resources for transmitting a data packet to at least a first UE. The selecting circuitry1441may be configured to execute selecting instructions1451stored in the computer-readable medium1406to implement any of the one or more of the functions described herein.

The processor1404may also include generating circuitry1442configured to generate a first reservation message, including the indication of the one or more second sidelink resources for transmitting the data packet. The generating circuitry1442may be configured to execute generating instructions1452stored in the computer-readable medium1406to implement any of the one or more of the functions described herein.

The processor1404may further include transmitting circuitry1443configured to transmit a first reservation message to the first UE (e.g., first UE602ofFIG. 6, first UE702oFIG. 7) via one or more first sidelink resources. The first reservation message may include an indication of the one or more second sidelink resources for subsequently transmitting a first data packet to a first UE. The transmitting circuitry1443may also be configured to transmit the first data packet to the first UE. The transmitting circuitry1443may be configured to execute transmitting instructions1453stored in the computer-readable medium1406to implement any of the one or more of the functions described herein.

FIG. 15is a flow chart of a method of wireless communication1500that may be utilized to forward a resource reservation according to some aspects. In some examples, the method of wireless communication may be employed by a UE, such as the second UE1400as shown and described in connection withFIG. 14. The method may be performed in a wireless communication network in some examples. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method of wireless communication1500may be performed by the second UE1400, as shown and described in connection withFIG. 14, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1502, the second UE may select one or more second sidelink resources for transmitting a data packet to a first user equipment (UE) (e.g., first UE602ofFIG. 6, first UE702ofFIG. 7). The second UE may also select one or more first sidelink resources for transmitting a first reservation message to the first UE. For example, the selecting circuitry1441as shown and described in connection withFIG. 14may provide a means for selecting one or more second sidelink resources for transmitting a data packet to a first user equipment (UE) and selecting one or more first sidelink resources for transmitting a first reservation message to the first UE.

At block1504, the second UE may generate the first reservation message, including an indication of the one or more second sidelink resources. For example, the generating circuitry1442as shown and described in connection withFIG. 14may provide a means for generating the first reservation message, including an indication of the one or more second sidelink resources.

At block1506, the second UE may transmit the first reservation message to the second UE using the one or more first sidelink resources. For example, the transmitting circuitry1443as shown and described in connection withFIG. 14may provide a means for transmitting the first reservation message to the second UE using the one or more first sidelink resources.

At block1508, the first UE may transmit the data packet to the first UE using the one or more second sidelink resources. For example, the transmitting circuitry1443, as shown and described in connection withFIG. 14, may provide a means for transmitting the data packet to the first UE using the one or more second sidelink resources.

FIG. 16is a block diagram illustrating an example of a hardware implementation of a third user equipment (UE) (e.g., a third wireless communication device)1600employing a processing system1614. For example, the third UE1600may be any of the UEs as shown and described in connection withFIGS. 1, 3, 6, and/or7. In particular, the third UE1600may be exemplified by the third UE606as shown and described in connection withFIG. 6and/or the third UE706as shown ad described in connection withFIG. 7.

In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system1614that includes one or more processors1604. The processing system1614may be substantially the same as the processing system814illustrated inFIG. 8, including a bus interface1608, a bus1602, a processor1604, and a computer-readable medium1606. Furthermore, the third UE1600may include a user interface1612and a transceiver1610substantially similar to those described herein inFIG. 8. That is, the processor1604, as utilized in the third UE1600, may be used to implement any one or more of the processes described herein.

In some aspects of the disclosure, the processor1604may include communication and processing circuitry1640configured for various functions, including, for example, communicating with a network core (e.g., a 5G core network), one or more scheduling entities, one or more other UEs via sidelink, and/or any other entity, such as, for example, local infrastructure or an entity communicating with the third UE1600via the Internet, such as a network provider. According to some aspects, the various functions of the communication and processing circuitry1640may implement resource reservation forwarding procedures as described herein.

In some aspects of the disclosure, the processor1604may include circuitry configured for various functions. For example, the processor1604may include receiving circuitry1641configured to receive a reservation forwarding message, including an indication of a first reservation message, from a first UE (e.g., first UE602ofFIG. 6, first UE702ofFIG. 7) via one or more forwarding sidelink resources. The first reservation message may have originated at a second UE (e.g., second UE604ofFIG. 6, second UE704ofFIG. 7) and may include an indication of one or more sidelink second resources on which the second UE may transmit a data packet (to at least the first UE). The receiving circuitry1641may also be configured to receive the data packet from the second UE via the one or more second sidelink resources. The receiving circuitry1641may further be configured to receive at least one additional reservation forwarding message, including the indication of the first reservation message (of another reservation message) from at least one additional UE via one or more additional forwarding sidelink resources. The receiving circuitry1641may be configured to execute receiving instructions1651stored in the computer-readable medium1606to implement any of the one or more of the functions described herein.

The processor1604may also include abstaining circuitry1642configured to cause the third UE1600to abstain from using the one or more second sidelink resources for communication thereon. The abstaining circuitry1642may be configured to execute abstaining instructions1652stored in the computer-readable medium1606to implement any of the one or more of the functions described herein.

The processor1604may further include selecting circuitry1643configured to select one or more different sidelink resources for communication with the first UE and/or one or more other UEs. The selecting circuitry1643may also be configured to execute selecting instructions1653stored in the computer-readable medium1606to implement any of the one or more of the functions described herein.

In addition, the processor1604may include transmitting circuitry1644configured to transmit a second data packet to at least the first UE via the one or more different sidelink resources. The transmitting circuitry1644may be configured to execute transmitting instructions1654stored in the computer-readable medium1606to implement any of the one or more of the functions described herein.

The processor1604may also include normalizing circuitry1645configured to normalize an RSRP value based on a difference between a first number of subchannels utilized for the first reservation message and a second number of subchannels associated with the one or more sidelink resources to produce a normalized RSRP value. The normalizing circuitry1645may be configured to execute normalizing instructions1655stored in the computer-readable medium1606to implement any of the one or more of the functions described herein.

FIG. 17is a flow chart1700of a method of forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the third UE1600, as described above, and illustrated inFIG. 16, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1702, the third UE may receive, via one or more forwarding sidelink resources, a reservation forwarding message from a first user equipment (UE), the reservation forwarding message may include a first reservation message originating from a second user equipment (UE) or an indication of one or more second sidelink resources indicated in the first reservation message. The one or more second sidelink resources being different from the one or more forwarding sidelink resources. The second UE may reserve the one or more second sidelink resources for transmission of a packet. In one example, the packet may be intended to be received by the first UE (i.e., the first UE may be the intended recipient of the packet). The second UE may be, for example, the second UE604ofFIG. 6, the second UE704ofFIG. 7, or the second UE1400ofFIG. 14. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving, via one or more forwarding sidelink resources, a reservation forwarding message from a first UE, the reservation forwarding message may include a first reservation message originating from a second UE or an indication of one or more second sidelink resources indicated in the first reservation message. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal.

In some aspects, the reservation forwarding message may be included in a sidelink medium access control (MAC) control element (MAC-CE) and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a sidelink radio resource control (RRC) message and included in the data portion of the sidelink transmission. In some aspects, the reservation forwarding message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the sidelink transmission. In some aspects, the first UE may transmit the reservation forwarding message to the third UE through a broadcast transmission on a physical sidelink shared channel (PSSCH). In some aspects, the first UE may transmit the reservation forwarding message to only the third UE in a sidelink RRC message through a unicast transmission on a PSSCH. In some aspects, the first UE may transmit the reservation forwarding message to at least the third UE in SCI-2 on a physical sidelink control channel (PSCCH).

At block1704, the third UE may abstain from using (e.g., transmitting on) the one or more second sidelink resources for communication thereon. For example, the abstaining circuitry1642as shown and described in connection withFIG. 16may provide a means for abstaining from using the one or more second sidelink resources for communication thereon. In some aspects, the third UE may abstain from using the one or more sidelink resources based on the reservation forwarding message including an indication of a collision between the transmission of the first reservation message and a transmission of a second reservation message. For example, with the third UE abstaining from using the one or more second sidelink resources, the second UE may transmit the data packet to the first UE with a reduced risk of a collision between transmissions from the third UE and the second UE.

In some aspects, the third UE may mark the one or more second sidelink resources as reserved with the corresponding priority of the data packet in response to receiving the reservation forwarding message. In response to receiving the reservation forwarding message from the first UE and abstaining from using the one or more second sidelink resources, the third UE may select one or more different sidelink resources (i.e., different from the one or more second sidelink resources) for transmitting data packets. For example, the third UE may select the one or more different sidelink resources for communication with the first UE and/or one or more other UEs.

In some aspects, the third UE may obtain a reference signal received power (RSRP) value of the reservation forwarding message. In examples in which the reservation forwarding message indicates that the first UE intends to receive the data packet scheduled by the first reservation message (e.g., Rx bit=true), the third UE may abstain from using the one or more second sidelink resources regardless of the RSRP value or abstain from using the one or more second sidelink resources in response to the RSRP value being greater than a predetermined RSRP threshold value. In one example, the third UE may avoid using the one or more second sidelink resources in response to a given RSRP value associated with any one of the reservation forwarding message or any one of at least one additional reservation forwarding message received at the third UE exceeding a RSRP value (e.g., exceeding the predetermined RSRP threshold value).

In some aspects, the third UE may receive the reservation forwarding message that includes an identifier (ID) of the second UE. In response to receiving the reservation forwarding message that includes the ID of the second UE, the third UE may identify a stored reference signal received power (RSRP) value obtained for the second UE from a previous transmission from the second UE and abstain from transmitting on the one or more second sidelink resources in response to the stored RSRP value being greater than a threshold value.

In some aspects, the third UE may receive the reservation forwarding message from the first UE, including a first RSRP value associated with the first reservation message from the second UE. The third UE may normalize the first RSRP value based on a difference between a first number of subchannels utilized for the first reservation message and a second number of subchannels associated with the one or more sidelink resources to produce a normalized RSRP value. In addition, the third UE may further obtain a second RSRP value associated with the reservation forwarding message. In examples in which the reservation forwarding message does not indicate that the first UE intends to receive (e.g., is the intended recipient of) the data packet scheduled by the first reservation message, the third UE may abstain from using the one or more second sidelink resources based on determining that the first UE is a potential receiver of the second UE and abstaining from using the one or more second sidelink resources regardless of the first RSRP value or the second RSRP value or in response to the second RSRP value being greater than the RSRP threshold value. In some aspects, the third UE may further abstain from using the one or more second sidelink resources in response to a maximum RSRP value among the first RSRP value (or normalized RSRP value) and the second RSRP value being greater than the RSRP threshold value regardless of whether the first UE is a potential recipient of the data packet.

In some aspects, the third UE may receive at least one additional reservation forwarding message, including the first reservation message, or the indication of the resources reserved by the first reservation message, from at least one additional UE via one or more additional forwarding sidelink resources. In this example, the third UE may abstain from using the one or more second sidelink resources based on a maximum reference signal received power (RSRP) value in the same or similar way that the third UE606ofFIG. 6abstained from using the one or more sidelink resources as described in connection withFIG. 6.

FIG. 18is a flow chart1800of a method of forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the third UE1600, as described above, and illustrated inFIG. 16, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1802, the third UE may receive, via one or more forwarding sidelink resources, a reservation forwarding message from a first user equipment (UE), the reservation forwarding message may include a first reservation message originating from a second user equipment (UE) or an indication of one or more second sidelink resources indicated in the first reservation message. The second UE may be, for example, the second UE604ofFIG. 6, the second UE704ofFIG. 7, or the second UE1400ofFIG. 14. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving, via one or more forwarding sidelink resources, a reservation forwarding message from a first UE, the reservation forwarding message may include a first reservation message originating from a second UE or an indication of one or more second sidelink resources indicated in the first reservation message. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal. The description of block1802corresponds to and is the same or similar to that of block1702as shown and described in connection withFIG. 17. Block1802may include one or more of the same or similar features as described herein with respect to block1702. To ensure conciseness of the application, the description will not be repeated.

At block1804, the third UE may abstain from using the one or more second sidelink resources for communication thereon. For example, the abstaining circuitry1642, as shown and described in connection withFIG. 16, may provide a means for abstaining from using the one or more second sidelink resources for communication thereon. The description of block1804corresponds to and is the same or similar to that of block1704as shown and described in connection withFIG. 17. Block1804may include one or more of the same or similar features as described herein with respect to block1704. To ensure conciseness of the application, the description will not be repeated.

At block1806, the third UE may receive the data packet intended for the first UE from the second UE via the one or more second sidelink resources. Because the data packet is intended for the first UE, the third UE may not decode the data packet. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving the data packet intended for the first UE from the second UE via the one or more second sidelink resources.

FIG. 19is a flow chart1900of a method of forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the third UE1600, as described above, and illustrated inFIG. 16, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block1902, the third UE may receive, via one or more forwarding sidelink resources, a reservation forwarding message from a first user equipment (UE), the reservation forwarding message may include a first reservation message originating from a second user equipment (UE) or an indication of one or more second sidelink resources indicated in the first reservation message. The second UE may be, for example, the second UE604ofFIG. 6, the second UE704ofFIG. 7, or the second UE1400ofFIG. 14. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving, via one or more forwarding sidelink resources, a reservation forwarding message from a first UE, the reservation forwarding message may include a first reservation message originating from a second UE or an indication of one or more second sidelink resources indicated in the first reservation message. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal. The description of block1902corresponds to and is the same or similar to that of block1702as shown and described in connection withFIG. 17. Block1902may include one or more of the same or similar features as described herein with respect to block1702. To ensure conciseness of the application, the description will not be repeated.

At block1904, the third UE may abstain from using the one or more second sidelink resources for communication thereon. For example, the abstaining circuitry1642, as shown and described in connection withFIG. 16, may provide a means for abstaining from using the one or more second sidelink resources for communication thereon. The description of block1904corresponds to and is the same or similar to that of block1704as shown and described in connection withFIG. 17. Block1904may include one or more of the same or similar features as described herein with respect to block1704. To ensure conciseness of the application, the description will not be repeated.

At block1906, the third UE may select one or more different sidelink resources (i.e., different from the one or more second sidelink resources) for communication with the first UE and/or one or more other UEs. For example, the selecting circuitry1643, as shown and described in connection withFIG. 16, may provide a means for selecting one or more different sidelink resources for communication with the first UE and/or one or more other UEs. For example, the third UE may mark the one or more second sidelink resources as reserved with the corresponding priority of the data packet in response to receiving the reservation forwarding message.

At block1908, the third UE may transmit a second data packet to the first UE and/or the one or more other UEs via the one or more different sidelink resources. For example, the transmitting circuitry1644, as shown and described in connection withFIG. 16, may provide a means for transmitting a second data packet to the first UE and/or the one or more other UEs via the one or more different sidelink resources.

FIG. 20is a flow chart2000of a method of forwarding a resource reservation according to some aspects. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all aspects. In some examples, the method may be performed by the third UE1600, as described above, and illustrated inFIG. 16, by a processor or processing system, or by any suitable means for carrying out the described functions.

At block2002, the third UE may receive, via one or more forwarding sidelink resources, a reservation forwarding message from a first user equipment (UE), the reservation forwarding message may include a first reservation message originating from a second user equipment (UE) or an indication of one or more second sidelink resources indicated in the first reservation message. The second UE may be, for example, the second UE604ofFIG. 6, the second UE704ofFIG. 7, or the second UE1400ofFIG. 14. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving, via one or more forwarding sidelink resources, a reservation forwarding message from a first UE, the reservation forwarding message may include a first reservation message originating from a second UE or an indication of one or more second sidelink resources indicated in the first reservation message. The first reservation message may be included, for example, in a control portion of a sidelink transmission. In some aspects, the first reservation message may be included in a second stage sidelink control information (SCI-2) and included in a control portion of the signal. The description of block2002corresponds to and is the same or similar to that of block1702as shown and described in connection withFIG. 17. Block2002may include one or more of the same or similar features as described herein with respect to block1702. To ensure conciseness of the application, the description will not be repeated.

At block2004, the third UE may receive an additional reservation forwarding message, including the first reservation message or an indication of the one or more second sidelink resources indicated in the first reservation message, from at least one additional UE, different from the first UE and the second UE, via one or more additional forwarding sidelink resources. For example, the receiving circuitry1641, as shown and described in connection withFIG. 16, may provide a means for receiving an additional reservation forwarding message, including the first reservation message, or an indication of the one or more second sidelink resources indicated in the first reservation message, from at least one additional UE, different from the first UE and the second UE, via one or more additional forwarding sidelink resources.

At block2006, the third UE may abstain from using the one or more second sidelink resources for communication thereon. For example, the abstaining circuitry1642, as shown and described in connection withFIG. 16, may provide a means for abstaining from using the one or more second sidelink resources for communication thereon. The description of block2006corresponds to and is the same or similar to that of block1704as shown and described in connection withFIG. 17. Block2006may include one or more of the same or similar features as described herein with respect to block1704. To ensure conciseness of the application, the description will not be repeated.

At block2008, the third UE may select one or more different sidelink resources, different from the one or more second sidelink resources, for communication with the first UE and/or one or more other UEs. For example, the selecting circuitry1643, as shown and described in connection withFIG. 16, may provide a means for selecting one or more different sidelink resources for communication with the first UE and/or one or more other UEs. The description of block2008corresponds to and is the same or similar to that of block1906as shown and described in connection withFIG. 19. Block2008may include one or more of the same or similar features as described herein with respect to block1906. To ensure conciseness of the application, the description will not be repeated.

At block2010, the third UE may transmit a second data packet to the first UE and/or the one or more other UEs via the one or more different sidelink resources. For example, the transmitting circuitry1644, as shown and described in connection withFIG. 16, may provide a means for transmitting a second data packet to the first UE and/or one or more other UEs via the one or more different sidelink resources. The description of block2010corresponds to and is the same or similar to that of block1908as shown and described in connection withFIG. 19. Block2010may include one or more of the same or similar features as described herein with respect to block1908. To ensure conciseness of the application, the description will not be repeated.

Of course, in the above examples, the circuitry included in the processors804,1404, and/or1604is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable medium806,1406, and/or1606, or any other suitable apparatus or means described in any one of theFIGS. 1, 3, 6, 7, 8, 14, and/or16, and utilizing, for example, the processes and/or algorithms described herein in relation toFIGS. 6, 7, 9-13, 15, and/or17-20.

Aspect 1: A first user equipment (UE), comprising: a transceiver for wireless communication, a memory, and a processor coupled to the transceiver and the memory, the processor and the memory being configured to: receive a first reservation message from a second UE via one or more first sidelink resources, the first reservation message comprising a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE, transmit a first reservation forwarding message comprising at least the first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources, and receive a transmission of the first data packet from the second UE via the one or more second sidelink resources.

Aspect 2: The first UE of aspect 1, wherein the processor and the memory are further configured to: transmit the first reservation forwarding message in response to the first UE being an intended recipient of the first data packet.

Aspect 3: The first UE of aspect 1 or 2, wherein the first reservation message comprises at least one reservation of one or more other sidelink resources for at least one retransmission of the first data packet, and the processor and the memory are further configured to: receive the at least one retransmission of the first data packet via the one or more other sidelink resources.

Aspect 4: The first UE of any of aspects 1 through 3, wherein the processor and the memory are further configured to: receive a second reservation message from a fourth UE, wherein the second reservation message comprises a second indication of one or more fifth sidelink resources reserved by the fourth UE for receiving a second data packet from the fourth UE, and include the second reservation message or the second indication of the one or more fifth sidelink resources reserved in the second reservation message in the first reservation forwarding message.

Aspect 5: The first UE of any of aspects 1 through 4, wherein the processor and the memory are further configured to: obtain a reference signal received power (RSRP) value of the first reservation message received on the one or more first sidelink resources, and include the RSRP value in the first reservation forwarding message.

Aspect 6: The first UE of any of aspects 1 through 5, wherein the processor and the memory are further configured to: monitor, for a predetermined period of time following the receiving of the first reservation message, for at least one of: a second reservation message or a second reservation forwarding message comprising a second indication of a reservation by another UE, different from the second UE, and transmit the first reservation forwarding message in response to expiry of the predetermined period of time in an absence of receiving the at least one of: the second reservation message or the second reservation forwarding message.

Aspect 7: The first UE of any of aspects 1 through 6, wherein to transmit the first reservation forwarding message to the at least the third UE via the one or more third sidelink resources, the processor and the memory are further configured to: represent the first indication of the one or more second sidelink resources in a bit map, and transmit the bit map to the at least the third UE via the one or more third sidelink resources.

Aspect 8: The first UE of any of aspects 1 through 7, wherein the bit map comprises a plurality of locations, each corresponding to a respective subchannel in a respective slot, and wherein the processor and the memory are further configured to: represent the first indication of the one or more second sidelink resources in at least one location of the plurality of locations corresponding to the one or more second sidelink resources.

Aspect 9: The first UE of any of aspects 1 through 8, wherein each location of the plurality of locations comprises a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot.

Aspect 10. The first UE of any of aspects 1 through 9, wherein the first reservation forwarding message comprises at least one bit indicating that the first UE is an intended recipient of the transmission of the first data packet.

Aspect 11. The first UE of any of aspects 1 through 10, wherein the processor and the memory are further configured to: obtain a reference signal received power (RSRP) value of the first reservation message received on the one or more first sidelink resources, and include the RSRP value in the first reservation forwarding message.

Aspect 12. The first UE of any of aspects 1 through 11, wherein the processor and the memory are further configured to at least one of: determine if the first UE is an intended recipient of the first data packet, or compare a reference signal received power (RSRP) value of the first reservation message received on the one or more first sidelink resources to a threshold value, and transmit the first reservation forwarding message in response to at least one of: determining that the first UE is the intended recipient of the first data packet, or determining that the RSRP value is less than the threshold value.

Aspect 13: The first UE of any of aspects 1 through 12, wherein to transmit the first reservation forwarding message to at least the third UE via the one or more third sidelink resources, the processor and the memory are further configured to: transmit the first reservation forwarding message via a second stage sidelink control information (SCI-2), sidelink medium access control-control element (MAC-CE), or sidelink radio resource control (RRC) message, to at least the third UE via the one or more third sidelink resources.

Aspect 14: A method of wireless communication at a first user equipment (UE), comprising: receiving a first reservation message from a second UE via one or more first sidelink resources, the first reservation message comprising a first indication of one or more second sidelink resources for subsequently receiving a first data packet from the second UE, transmitting a first reservation forwarding message comprising at least the first indication of the one or more second sidelink resources to at least a third UE via one or more third sidelink resources, and receiving a transmission of the first data packet from the second UE via the one or more second sidelink resources.

Aspect 15: The method of aspect 14, wherein the transmitting the first reservation forwarding message further comprises: transmitting the first reservation forwarding message in response to the first UE being an intended recipient of the first data packet.

Aspect 16: The method of aspect 14 or 15, wherein the first reservation forwarding message comprises a single bit having a value indicating that the first UE is an intended recipient of the first data packet.

Aspect 17: The method of any of aspects 14 through 16, wherein the one or more second sidelink resources are selected by the second UE, and the method further comprises: transmitting the first reservation message via sidelink control information (SCD).

Aspect 18: The method of any of aspects 14 through 17, wherein the one or more first sidelink resources and the one or more third sidelink resources are fewer than the one or more second sidelink resources.

Aspect 19: The method of any of aspects 14 through 18, wherein the first reservation message comprises at least one reservation of one or more other sidelink resources for at least one retransmission of the first data packet, wherein the receiving the first data packet further comprises: receiving the at least one retransmission of the first data packet via the one or more other sidelink resources.

Aspect 20: The method of any of aspects 14 through 19, further comprising: receiving a second reservation message from a fourth UE, wherein the second reservation message comprises a second indication of one or more fifth sidelink resources reserved by the fourth UE for receiving a second data packet from the fourth UE, and including the second reservation message or the second indication of the one or more fifth sidelink resources reserved in the second reservation message in the first reservation forwarding message.

Aspect 21: The method of any of aspects 14 through 20, wherein the first reservation forwarding message comprises at least one bit indicating that the first UE is an intended recipient of the transmission of the first data packet.

Aspect 22: The method of any of aspects 14 through 21, further comprising: obtaining a reference signal received power (RSRP) value of the first reservation message received on the one or more first sidelink resources, and including the RSRP value in the first reservation forwarding message.

Aspect 23: The method of any of aspects 14 through 22, wherein the transmitting the first reservation forwarding message further comprises: at least one of: determining if the first UE is an intended recipient of the first data packet, or comparing a reference signal received power (RSRP) value of the first reservation message received on the one or more first sidelink resources to a threshold value, and transmitting the first reservation forwarding message in response to at least one of: determining that the first UE is the intended recipient of the first data packet, or determining that the RSRP value is less than the threshold value.

Aspect 24: The method of any of aspects 14 through 23, wherein the transmitting the first reservation forwarding message further comprises: monitoring, for a predetermined period of time following the receiving of the first reservation message, for at least one of: a second reservation message or a second reservation forwarding message comprising a second indication of a reservation by another UE, different from the second UE, and transmitting the first reservation forwarding message in response to expiry of the predetermined period of time in an absence of receiving the at least one of: the second reservation message or the second reservation forwarding message.

Aspect 25: The method of any of aspects 14 through 24, wherein the transmitting the first reservation forwarding message to the at least the third UE via the one or more third sidelink resources further comprises: representing the first indication of the one or more second sidelink resources in a bit map, and transmitting the bit map to the at least the third UE via the one or more third sidelink resources.

Aspect 26: The method of any of aspects 14 through 25, wherein the bit map comprises a plurality of locations, each corresponding to a respective subchannel in a respective slot, and wherein the representing the first indication of the one or more second sidelink resources in the bit map further comprises: representing the first indication of the one or more second sidelink resources in at least one location of the plurality of locations corresponding to the one or more second sidelink resources.

Aspect 27: The method of any of aspects 14 through 26, wherein each location of the plurality of locations comprises a multi-bit value representing a resource reservation occupation level of the respective subchannel in the respective slot.

Aspect 28: The method of any of aspects 14 through 27, wherein the resource reservation occupation level of the respective subchannel in the respective slot is determined based on a reference signal received power (RSRP) obtained from the respective subchannel in the respective slot.

Aspect 29: The method of any of aspects 14 through 28, wherein the bit map comprises a width corresponding to a quantity of subchannels and a length corresponding to a quantity of slots.

Aspect 30: The method of any of aspects 14 through 29, wherein the transmitting the first reservation forwarding message to at least the third UE via the one or more third sidelink resources further comprises: transmitting the first reservation forwarding message via a second stage sidelink control information (SCI-2), sidelink medium access control-control element (MAC-CE), or sidelink radio resource control (RRC) message, to at least the third UE via the one or more third sidelink resources.

Aspect 31: An apparatus configured for wireless communication comprising at least one means for performing a method of any one of aspects 14 through 30.

Aspect 32: A non-transitory computer-readable medium storing computer-executable code, comprising code for causing an apparatus to perform a method of any one of aspects 14 through 30.

It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based on design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present stages of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.