Short transmission time interval for sidelink feedback

Abstract

Methods, systems, and apparatus for wireless communications are described. A sidelink message may be scheduled for a UE during a first short transmission time interval (TTI). A first short TTI and a second short TTI for sending a sidelink feedback message corresponding to the sidelink message may be shorter in duration than another, longer type of TTI. The UE may send automatic gain control information in a first symbol period of the second TTI, send the sidelink feedback message in a second symbol period of the second TTI (after the first symbol period of the second TTI), and switch from operating in a transmit mode to operating in a receive mode during a third symbol period of the second TTI (after the second symbol period of the second TTI).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of U.S. patent application No. 17 / 458,223, filed by Liu et al. on August 26, 2021, entitled “SHORT TRANSMISSIONTIME INTERVALS FOR SIDELINK FEEDBACK,” which is assigned to the assignee of this application. Technical Field

[0003] The following relates to wireless communications, including short transmission time intervals for sidelink feedback. Background Art

[0004] Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcasting, etc. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth generation (4G) systems (such as long term evolution (LTE) systems, improved LTE (LTE-A) systems, or LTE-aPro systems) and fifth generation (5G) systems that may be referred to as new radio (NR) systems. These systems may employ techniques such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include one or more base stations or one or more network access nodes, each of which simultaneously supports communication for multiple communication devices (which may be referred to as user equipment (UE)). Some wireless systems may support sidelink communication, which may be a direct communication between two or more UEs. Summary of the Invention

[0005] The described technology relates to improved methods, systems, devices and apparatus for supporting short transmission time intervals (TTIs) for sidelink feedback. A longer TTI (e.g., a time slot) can be divided into multiple short TTIs (e.g., mini-slots). Some or all short TTIs within a longer TTI can be configured to carry sidelink feedback, and such short TTIs can be time-division multiplexed or frequency-division multiplexed with other short TTIs (e.g., short TTIs carrying sidelink data or control information). In some cases, a UE can send automatic gain control information in the first (e.g., initial) symbol period of a short TTI, send a sidelink feedback message in the second (e.g., middle) symbol period of the short TTI that occurs after the first symbol period of the short TTI, and have a switching gap in the third (e.g., last) symbol period of the short TTI, the third symbol period occurring in chronological order after the second symbol period. By using a short TTI for sidelink feedback, the latency associated with the sidelink feedback message can be reduced, and thus the overall latency and reliability of the sidelink communication can be improved, among other possible benefits.

[0006] A method for wireless communication at a user equipment (UE) is described. The method may include: for a sidelink message scheduled for a first transmission time interval, identifying a second transmission time interval for sending a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval; sending automatic gain control information in a first symbol period of the second transmission time interval; sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0007] An apparatus for wireless communication at a UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to: for a sidelink message scheduled for a first transmission time interval, identify a second transmission time interval for sending a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval; send automatic gain control information in a first symbol period of the second transmission time interval; send the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and switch from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0008] Another apparatus for wireless communication at a UE is described. The apparatus may include: means for identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for sending a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval; means for sending automatic gain control information in a first symbol period of the second transmission time interval; means for sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and means for switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0009] A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to: for a sidelink message scheduled for a first transmission time interval, identify a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval; transmit automatic gain control information in a first symbol period of the second transmission time interval; transmit the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and switch operating the UE from a transmit mode to a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0010] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for performing the following operations: receiving configuration signaling, wherein the configuration signaling indicates, for a set of multiple consecutive transmission time intervals including the second transmission time interval, that a first subchannel can be allocated to a sidelink feedback message, and a second subchannel different from the first subchannel can be allocated to sidelink data or control information.

[0011] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for performing the following operations: receiving a bitmap indicating a set of physical resource blocks within a sidelink bandwidth portion for carrying a sidelink feedback message; and the sidelink feedback message may be sent via one or more physical resource blocks in the set of physical resource blocks.

[0012] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the third transmission time interval comprises a set of multiple transmission time intervals, the second transmission time interval and the fourth transmission time interval are included in the set of multiple transmission time intervals; and the sidelink feedback message can be sent within a subchannel allocated for sidelink data or control information during the fourth transmission time interval.

[0013] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for receiving an indication of a periodicity of a resource pool comprising a set of the plurality of transmission time intervals, wherein a subset of one or more transmission time intervals may be allocated for sidelink feedback messages within the set of the plurality of transmission time intervals based on the periodicity.

[0014] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for receiving a bitmap indicating a set of physical resource blocks for carrying the sidelink feedback message in the second symbol period, wherein the sidelink feedback message may be sent via one or more physical resource blocks in the set of physical resource blocks.

[0015] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for receiving a subset of sidelink feedback resource indices from a set of multiple sidelink feedback resource indices, wherein the set of multiple sidelink feedback resource indices can be mapped to a set of multiple cyclic shift pairs and a set of multiple physical resource blocks, and wherein the sidelink feedback message can be sent via one or more physical resource blocks and using a cyclic shift pair corresponding to one of the sidelink feedback resource indices in the subset of sidelink feedback resource indices.

[0016] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, means, or instructions for receiving a feedback delay value indicating a position of the second transmission time interval within the third transmission time interval.

[0017] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for sending a power reservation signal in an initial symbol of the third transmission time interval based on the first transmission time interval, wherein in the first transmission time interval, the sidelink message may be scheduled to precede the third transmission time interval including the second transmission time interval.

[0018] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the power reservation signal can be based on a reference signal.

[0019] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the reference signal comprises a comb-based reference signal, and a comb value for the reference signal may be based on a position of the second transmission time interval within the third transmission time interval.

[0020] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the power reservation signal may be sent in the same resource block location in the frequency domain as the sidelink feedback message.

[0021] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, a sidelink feedback resource partition comprises a set of physical resource blocks, and the number of physical resource blocks within the set of physical resource blocks may be based on a second number of physical resource blocks allocated for sidelink feedback messages within the second transmission time interval, a number of transmission time intervals allocated to sidelink messages and corresponding to the second transmission time interval, a number of subchannels included in the sidelink feedback resource partition, or any combination thereof.

[0022] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for performing the following operations: selecting a physical resource block in the set of physical resource blocks for sending the sidelink feedback message based on a time-then-frequency mapping between the resources allocated to the sidelink message and the set of physical resource blocks.

[0023] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, when the format of the sidelink feedback message may be based on a physical uplink control channel format 0 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition may be based on the number of physical resource blocks in the set of physical resource blocks and the number of cyclic shift pairs per physical resource block.

[0024] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, when the format of the sidelink feedback message may be based on a physical uplink control channel format 1 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition may be based on the number of physical resource blocks in the set of physical resource blocks, an orthogonal code spreading factor, and a number of cyclic shift pairs per physical resource block.

[0025] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for selecting a sidelink feedback resource within the sidelink feedback resource partition based on a first value modulo a second value, wherein the first value may be based on a sum of a layer 1 source identifier and a group member identifier associated with the sidelink message, wherein the second value may be based on a product of a number of the physical resource blocks in the set of physical resource blocks and a number of cyclic shift pairs per physical resource block, and wherein the sidelink feedback message may be sent via the selected sidelink feedback resource.

[0026] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the sidelink feedback message may be sent based at least in part on physical control channel format 0 based on the second symbol period including three or fewer symbols.

[0027] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the sidelink feedback message may be sent based at least in part on physical control channel format 1 based on the second symbol period including at least four symbols.

[0028] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, sending the sidelink feedback message in the second symbol period may include operations, features, units, or instructions for performing the following operations: sending the sidelink feedback message in the second symbol period includes: sending a waveform on an initial symbol of the second symbol period; and sending a corresponding repetition of the waveform in each additional symbol of the second symbol period.

[0029] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, units, or instructions for performing the following operations: selecting the second transmission time interval to send the sidelink feedback message based on a feedback timing configuration and a timing of the second transmission time interval relative to the first transmission time interval.

[0030] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the feedback timing configuration can be based on a fixed feedback timeline, a feedback delay value indicated in sidelink control information received by the UE, or both.

[0031] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first symbol period includes an initial symbol of the second transmission time interval; the third symbol period includes a last symbol of the second transmission time interval; and the second symbol period includes one or more symbols, the one or more symbols including each symbol of the second transmission time interval between the initial symbol and the last symbol. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1

[0014] An example of a wireless communication system supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0033] Figure 2 An example of an environment supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0034] Figure 3 An example of an environment supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0035] Figure 4 An example of an environment supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0036] Figure 5 An example of an environment supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0037] Figure 6 An example of an environment supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0038] Figure 7 and 8 A block diagram of an apparatus supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0039] Figure 9 A block diagram of a communications manager supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0040] Figure 10 A diagram illustrating a system including devices supporting short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure is shown.

[0041] Figure 11 and 12 A flow chart illustrating a method of supporting short transmission time intervals for sidelink feedback according to aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0042] Sidelink communications in some wireless communication systems may have relatively high latency, resulting in communication delays or other disadvantages. The relatively high latency may be at least partially related to sidelink feedback messages, such as acknowledgement / negative acknowledgement feedback (ACK / NACK feedback), being assigned to the end of a slot in a slot-based configuration (e.g., to the last symbol of a 14-symbol slot).

[0043] However, as described herein, sidelink feedback messages can be sent using a short TTI (e.g., a mini-slot) rather than a full TTI (e.g., a slot), which can reduce the latency of the sidelink feedback and thereby provide improved latency and reliability of the sidelink communication as a whole, among other possible benefits. For example, a sidelink UE can receive control signaling from a base station or from another sidelink UE that instructs the sidelink UE to implement scheduling based on a short TTI (such as a mini-slot). Multiple mini-slots can occur within a full slot (e.g., multiple short TTIs within a full TTI). In some cases, a full slot (e.g., a full TTI) can include 14 symbols (e.g., a 14-symbol slot), while a mini-slot (e.g., a short TTI) can include fewer symbols (e.g., a subset of the 14 symbols).

[0044] Some or all short TTIs (e.g., mini-slots) within a full TTI (e.g., time slot) may be configured to carry sidelink feedback. In addition, a short TTI used for sidelink feedback may be time-division multiplexed or frequency-division multiplexed with one or more other short TTIs (e.g., multiplexed with a short TTI carrying sidelink data or control information). In some cases, within a short TTI configured to carry sidelink feedback, the first symbol period may include automatic gain control (AGC) information, the subsequent second symbol period may include sidelink feedback information, and the subsequent third symbol period may include a switching gap to provide a time during which the UE can switch operating modes (e.g., from transmit mode to receive mode, or vice versa).

[0045] Based on the use of a short TTI for sidelink feedback as described herein, a sidelink UE can send sidelink feedback earlier than such feedback would otherwise occur (e.g., before the end symbol of a slot that would otherwise include a mini-slot). Thus, the techniques described herein can reduce the latency of feedback associated with sidelink communications (e.g., ACK / NACK feedback), which in turn can reduce latency or otherwise improve the performance of sidelink communications overall. For example, additionally or alternatively, the use of a short TTI for sidelink feedback as described herein can help avoid at least some failed transmissions and associated retransmissions, can increase the throughput of sidelink communications, can increase the reliability of sidelink communications, or any combination thereof, among other possible benefits.

[0046] Aspects of the present disclosure are initially described in the context of wireless communication systems. Aspects of the present disclosure are further illustrated and described in the context of slot and mini-slot configurations related to a sidelink feedback channel for a transmission time interval. Aspects of the present disclosure are further illustrated and described by apparatus diagrams, system diagrams, and flow charts related to a sidelink feedback channel for a transmission time interval. Although certain aspects of the present disclosure may be described with reference to slots and mini-slots, the teachings herein may also be applied to other types of full TTIs (e.g., long TTIs) as well as short TTIs.

[0047] Figure 1 An example of a wireless communication system 100 supporting short transmission time intervals for sidelink feedback according to aspects of the present disclosure is shown. The wireless communication system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communication system 100 may support enhanced broadband communication, ultra-reliable communication, low-latency communication, or communication with low-cost and low-complexity devices, or any combination thereof.

[0048] Base stations 105 may be dispersed throughout a geographic area to form wireless communication system 100 and may be devices of different forms or with different capabilities. Base stations 105 and UEs 115 may communicate wirelessly via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which UEs 115 and base stations 105 may establish one or more communication links 125. Coverage areas 110 may be examples of geographic areas over which base stations 105 and UEs 115 may support signal communication according to one or more radio access technologies.

[0049] The UEs 115 may be dispersed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be stationary or mobile, or both, at different times. The UEs 115 may be devices in different forms or with different capabilities. Figure 1 Some example UEs 115 are shown in FIG. 1 . The UEs 115 described herein may be capable of communicating with various types of devices, such as other UEs 115, base stations 105, or network devices (e.g., core network nodes, relays, integrated access and backhaul (IAB) nodes, or other network devices), such as Figure 1 shown.

[0050] The base stations 105 can communicate with the core network 130, or communicate with each other, or both. For example, the base stations 105 can interface with the core network 130 via one or more backhaul links 120 (e.g., via S1, N2, N3, or other interfaces). The base stations 105 can communicate with each other directly (e.g., directly between base stations 105) or indirectly (e.g., via the core network 130) over the backhaul links 120 (e.g., via X2, Xn, or other interfaces), or both. In some examples, the backhaul links 120 can be one or more radio links, or can include one or more radio links.

[0051] One or more of the base stations 105 described herein may include or may be referred to by a person of ordinary skill in the art as a base station transceiver, a radio base station, an access point, a radio transceiver, a NodeB, an evolved NodeB (eNB), a next generation NodeB or a giga NodeB (any of which may be referred to as a gNB), a home nodeB, a home evolved nodeB, or other appropriate terminology.

[0052] UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other appropriate terminology, where a "device" may also be referred to as a unit, a station, a terminal, or a client, among other examples. UE 115 may also include or may be referred to as a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communication (MTC) device, etc., which may be implemented in various items such as appliances, vehicles, meters, etc.

[0053] The UE 115 described herein may be capable of communicating with various types of devices, such as other UEs 115, which may sometimes act as relays, as well as base stations 105 and network devices, including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, such as Figure 1 shown.

[0054] The UE 115 and the base station 105 can communicate wirelessly with each other via one or more communication links 125 on one or more carriers. The term "carrier" can refer to a collection of radio frequency spectrum resources with a defined physical layer structure for supporting the communication link 125. For example, the carrier used for the communication link 125 can include a portion of a radio frequency spectrum band (e.g., a bandwidth portion (BWP)) that operates according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel can carry acquisition signaling (e.g., synchronization signals, system information), control signaling to coordinate operation for the carrier, user data, or other signaling. The wireless communication system 100 can support communication with the UE 115 using carrier aggregation or multi-carrier operation. Depending on the carrier aggregation configuration, the UE 115 can be configured with multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation can be used with both frequency division duplex (FDD) component carriers and time division duplex (TDD) component carriers.

[0055] The signal waveform transmitted on the carrier may be composed of multiple subcarriers (e.g., using a multicarrier modulation (MCM) technique such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing MCM techniques, a resource element may include one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely correlated. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Therefore, the more resource elements received by the UE 115 and the higher the order of the modulation scheme, the higher the data rate for the UE 115 may be. Wireless communication resources may refer to a combination of radio frequency spectrum resources, time resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial layers may also increase the data rate or data integrity for communications with the UE 115.

[0056] One or more numerologies for a carrier may be supported, where the numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time, and communications for a UE 115 may be limited to the one or more active BWPs.

[0057] The time interval for the base station 105 or the UE 115 can be expressed as a multiple of a basic time unit. For example, the basic time unit can be referred to as T s =1 / (Δf max ·N f ) seconds sampling period, where Δf max It can indicate the maximum subcarrier spacing supported, and N f The maximum supported discrete Fourier transform (DFT) size may be indicated. Time intervals for communication resources may be organized according to radio frames, each radio frame having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0058] Each frame may include a plurality of consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include a plurality of symbol periods (e.g., depending on the length of a cyclic prefix added in front of each symbol period). In some wireless communication systems 100, a time slot may be further divided into a plurality of mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N f ) sampling period. The duration of a symbol period may depend on the subcarrier spacing or the operating frequency band.

[0059] A subframe, slot, mini-slot, or symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communication system 100, which may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communication system 100 may be dynamically selected (e.g., in a burst of a shortened TTI (sTTI)).

[0060] Physical channels may be multiplexed on a carrier according to various techniques. Physical control channels and physical data channels may be multiplexed on a downlink carrier, for example, using one or more of a time division multiplexing (TDM) technique, a frequency division multiplexing (FDM) technique, or a hybrid TDM-FDM technique. A control region (e.g., a control resource set (CORESET)) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth of a carrier or a subset of the system bandwidth. One or more control regions (e.g., CORESETs) may be configured for a group of UEs 115. For example, one or more of UEs 115 may monitor or search a control region for control information according to one or more search space sets, and each search space set may include one or more control channel candidates having one or more aggregation levels arranged in a cascaded manner. The aggregation level for a control channel candidate may refer to the number of control channel resources (e.g., control channel elements (CCEs)) associated with the encoded information for a control information format having a given payload size. The search space sets may include a common search space set configured for transmitting control information to multiple UEs 115 and a UE-specific search space set for transmitting control information to a specific UE 115 .

[0061] In some examples, base stations 105 can be mobile and, therefore, provide communication coverage for mobile geographic coverage areas 110. In some examples, different geographic coverage areas 110 associated with different technologies can overlap, but the different geographic coverage areas 110 can be supported by the same base station 105. In other examples, overlapping geographic coverage areas 110 associated with different technologies can be supported by different base stations 105. The wireless communication system 100 can include, for example, a heterogeneous network in which different types of base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

[0062] The wireless communication system 100 can be configured to support ultra-reliable communication or low-latency communication or various combinations thereof. For example, the wireless communication system 100 can be configured to support ultra-reliable low-latency communication (URLLC). The UE 115 can be designed to support ultra-reliable, low-latency or critical functions. Ultra-reliable communication can include private communication or group communication and can be supported by one or more services (such as push-to-talk, video or data). Support for ultra-reliable, low-latency can include prioritization of services, and such services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency and ultra-reliable low-latency can be used interchangeably in this article.

[0063] In some examples, UE 115 can also communicate directly with other UEs 115 via device-to-device (D2D) communication links 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115 utilizing D2D communication may be within the geographic coverage area 110 of base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of base station 105 or otherwise unable to receive transmissions from base station 105. In some examples, groups of UEs 115 communicating via D2D communication may utilize a one-to-many (1:M) system in which each UE 115 transmits to each other UE 115 in the group. In some examples, base station 105 facilitates scheduling of resources for D2D communication. In other cases, D2D communication is performed between UEs 115 without involving base station 105.

[0064] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or a 5G core (5GC), which may include at least one control plane entity (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) that manages access and mobility, and at least one user plane entity (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)) that routes packets to or interconnects with an external network. The control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the core network 130. User IP packets may be transmitted via the user plane entity, which may provide IP address allocation and other functions. The user plane entity may be connected to an IP service 150 for one or more network operators. These IP services 150 may include access to the Internet, an intranet, an IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0065] Some of the network devices (e.g., base station 105) may include subcomponents such as an access network entity 140, which may be an example of an access node controller (ANC). Each access network entity 140 may communicate with the UE 115 through one or more other access network transport entities 145 (which may be referred to as radio heads, smart radio heads, or transmit / receive points (TRPs)). Each access network transport entity 145 may include one or more antenna panels. In some configurations, the various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., base station 105).

[0066] The wireless communication system 100 can operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). The region from 300 MHz to 3 GHz is often referred to as the very high frequency (UHF) region or decimeter band, as its wavelengths range from approximately 1 decimeter to 1 meter in length. UHF waves can be blocked or redirected by buildings and environmental features, but these waves can penetrate buildings sufficiently for macrocells to provide service to UEs 115 located indoors. Transmissions using UHF waves can be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmissions using the lower frequencies and longer wavelengths of the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz.

[0067] The wireless communication system 100 can utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communication system 100 can employ license assisted access (LAA), LTE-unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band, such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in an unlicensed radio frequency spectrum band, devices (such as base stations 105 and UEs 115) can employ carrier sensing for conflict detection and avoidance. In some examples, operations in an unlicensed band can be based on a carrier aggregation configuration in combination with component carriers operating in a licensed band (e.g., LAA). Operations in the unlicensed spectrum can include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

[0068] A base station 105 or a UE 115 may be equipped with multiple antennas that may be used to employ techniques such as transmit diversity, receive diversity, multiple-input, multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays or antenna panels that may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, the antennas or antenna arrays associated with a base station 105 may be located at various geographic locations. The base station 105 may have an antenna array having a number of rows and columns of antenna ports that the base station 105 may use to support beamforming for communications with the UE 115. Similarly, the UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, the antenna panels may support radio frequency beamforming for signals transmitted via the antenna ports.

[0069] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that can be used at a transmitting device or a receiving device (e.g., a base station 105, a UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming can be achieved by combining signals transmitted via antenna elements of an antenna array so that signals propagating in a particular direction relative to the antenna array experience constructive interference, while other signals experience destructive interference. Adjustments to signals transmitted via antenna elements can include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to signals carried via antenna elements associated with the device. The adjustments associated with each of these antenna elements can be defined by a set of beamforming weights associated with a particular orientation (e.g., relative to the antenna array of the transmitting device or the receiving device or relative to some other orientation).

[0070] The wireless communication system 100 can be a packet-based network operating according to a layered protocol stack. In the user plane, communications at the bearer or packet data convergence protocol (PDCP) layer can be IP-based. The radio link control (RLC) layer can perform packet segmentation and reassembly to communicate over logical channels. The medium access control (MAC) layer can perform priority handling and multiplexing of logical channels to transport channels. The MAC layer can also use error detection technology, error correction technology, or both to support retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer can provide the establishment, configuration, and maintenance of an RRC connection between the UE 115 and the base station 105 or the core network 130 to support radio bearers for user plane data. At the physical layer, transport channels can be mapped to physical channels.

[0071] UE 115 and base station 105 can support retransmission of data to increase the likelihood that the data is successfully received. Hybrid automatic repeat request (HARQ) feedback is a technique for increasing the likelihood that data is correctly received on communication link 125. Hybrid automatic repeat request (HARQ) can include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve throughput at the MAC layer under poor radio conditions (e.g., low signal to noise conditions). In some examples, a device can support same-slot HARQ feedback, in which the device can provide HARQ feedback in a particular time slot for data received in the previous symbol in the time slot. In other cases, the device can provide HARQ feedback in a subsequent time slot or according to some other time interval.

[0072] In some examples, UE 115 may identify a short TTI (e.g., a mini-slot) for sending a sidelink feedback message (e.g., via the PSFCH). In some cases, the short TTI may be associated with a sidelink message scheduled (e.g., via the PSSCH) for a previous short TTI (e.g., a short TTI received or scheduled to be received during a previous mini-slot during the same slot or a previous slot). The short TTI used to send the sidelink feedback message and the previous short TTI may be shorter than a full TTI (e.g., shorter than a slot). In some cases, within the short TTI used to transmit the sidelink feedback message, UE 115 may send automatic gain control information in a first (e.g., initial) symbol period, and UE 115 may send the sidelink feedback message in a second (e.g., middle) symbol period that occurs after the first symbol period. And in some cases, the third (e.g., last) symbol period of the short TTI used to send the sidelink feedback message may include a switching gap, where the third symbol period occurs after the second symbol period. UE 115 may switch operating modes (e.g., from transmit mode to receive mode, or vice versa) during the third symbol period. The short TTI used to send the sidelink feedback message may be time division multiplexed or frequency division multiplexed with one or more other short TTIs (e.g., one or more other short TTIs carrying sidelink data or control information).

[0073] Figure 2 An example of an environment 200 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0074] As shown, environment 200 may include UE 115-a, UE 115-b, UE 115-c, and base station 105-a, any of which may be as described herein. Figure 1Examples of UE 115 or base station 105 are described. Wireless communication system 200 may also include direct link 205 between base station 105-a and UE 115-a, direct link 210 between base station 105-a and UE 115-b, and direct link 215 between base station 105-a and UE 115-c. In some examples, direct link 205, direct link 210, and direct link 215 may each include a downlink and an uplink. In some examples, base station 105-a may use the downlink of direct link 205 to transmit control and / or data information to UE 115-a. And UE 115-a may use the uplink of direct link 205 to transmit control and / or data information to base station 105-a. In some cases, the downlink of direct link 205 may use different time and / or frequency resources than the uplink of direct link 205. In some cases, UE 115-a may use sidelink 220 to transmit control and / or data information (e.g., sidelink messages) to UE 115-b, and UE 115-b may use sidelink 220 to transmit control and / or data information to UE 115-a. In some cases, UE 115-a may use sidelink 225 to transmit control and / or data information to UE 115-c, and UE 115-c may use sidelink 225 to transmit control and / or data information to UE 115-a. In some cases, UE 115-a may use sidelink 220 to transmit sidelink feedback information (e.g., ACK / NACK) to UE 115-b, and UE 115-b may use sidelink 220 to transmit sidelink feedback information to UE 115-a. In some cases, UE 115-a may use sidelink 225 to transmit sidelink feedback information to UE 115-c, and UE 115-c may use sidelink 225 to transmit sidelink feedback information to UE 115-a.

[0075] In some examples, UE 115-a (e.g., UE 115-a, UE 115-ab, UE 115-ac) may receive (e.g., via the PSSCH) a sidelink message scheduled at a first mini-slot of a first time slot. In some cases, the first time slot may include one or more mini-slots including the first mini-slot. In some cases, UE 115-a may identify a second mini-slot of a second time slot following the first time slot for sending a sidelink feedback message associated with the received sidelink message (e.g., via the PSFCH). In some cases, the second time slot includes one or more mini-slots, including the second mini-slot. In some cases, the first mini-slot is shorter in time than the first time slot, and the second mini-slot is shorter in time than the second time slot.

[0076] In some examples, UE 115-a may send automatic gain control information in a first symbol period (e.g., an initial symbol period) of the second mini-slot. In some cases, UE 115-a may send automatic gain control information to implement automatic gain control at a legacy UE or a non-legacy UE. In some cases, the first symbol period occurs first in time sequence among the symbol periods of the second mini-slot. In some cases, UE 115-a may send a sidelink feedback message in a second symbol period (e.g., a middle symbol period) of the second mini-slot. In some cases, the second symbol period occurs in time sequence after the first symbol period of the second mini-slot. In some cases, UE 115-a may have a switching gap in a third symbol period (e.g., a last symbol period) of the second mini-slot, the third symbol period occurring in time sequence after the second symbol period of the second mini-slot. In some cases, the first symbol period includes one symbol, the second symbol period includes one or more symbols, and the third symbol period includes one symbol. In some cases, the one or more symbols of the second symbol period can include every symbol of the second mini-slot between the first symbol period and the third symbol period.

[0077] In some examples, the second symbol period may include multiple symbols (e.g., two or more symbols of a 14-symbol slot). In some cases, UE 115-a may transmit the waveform in an initial symbol of the second symbol period. In some cases, UE 115-a may transmit a corresponding repetition of the waveform in each additional symbol of the second symbol period.

[0078] In some examples, UE 115-a may select a second mini-slot to send the sidelink feedback message based on the feedback timing configuration and the timing of the second mini-slot relative to the first mini-slot including the corresponding sidelink message. In some cases, the feedback timing configuration may be based on a fixed feedback timeline or based on a feedback delay value (e.g., K1) indicated in the sidelink control information received by UE 115-a, or both.

[0079] In some examples, when the mid-symbol period includes 3 or fewer symbols (i.e., the mini-slot includes 5 or fewer symbols), the UE 115-a may send the sidelink feedback message based on a PUCCH format 0 waveform. In some cases, when the mid-symbol period includes 4 or more symbols (i.e., the mini-slot includes more than 5 symbols), the UE 115-a may send the sidelink feedback message based on a PUCCH format 1 waveform. Within the mini-slot, the UE 115-a may repeat the transmission in the first sidelink feedback symbol in one or more subsequent sidelink feedback symbols (e.g., when the mid-symbol period includes 3 or fewer symbols). For a four-symbol sidelink feedback mini-slot, the UE 115-a may repeat the first symbol of the sidelink feedback mini-slot in the second symbol of the sidelink feedback mini-slot, similar to PUCCH format 0, except without frequency mirror hopping (e.g., frequency hopping across slot boundaries or mini-slot boundaries within a subframe).

[0080] In some examples, UE 115-a may receive configuration signaling from base station 105-a (e.g., via direct link 205) or via sidelink communication (e.g., from UE 115-b via sidelink 220, from UE 115-c via sidelink 225). In some cases, the configuration signaling may indicate that, within a set of consecutive mini-slots of a given timeslot, one or more subchannels are allocated for transmitting sidelink feedback information, in addition to allocations for sidelink data or sidelink control information.

[0081] In some examples, UE 115-a may receive a bitmap (e.g., rbSetPSFCH bitmap) from base station 105-a or from another UE 115 via sidelink communication. In some cases, the bitmap may indicate a set of physical resource blocks in the sidelink bandwidth portion used to carry sidelink feedback information. In some cases, multiple mini-slots may occur within a given timeslot. In some cases, a mini-slot that includes sidelink feedback may be in the same subchannel as a mini-slot that includes sidelink data or sidelink control information.

[0082] In some examples, UE 115-a may receive an indication of the periodicity from base station 105-a or from another UE 115. In some cases, the periodicity may specify which mini-slots of a given timeslot are used for sidelink feedback. In some cases, UE 115-a may receive a bitmap (rbSet PSFCH bitmap) indicating a set of physical resource blocks used to carry sidelink feedback information in mid-symbol periods.

[0083] In some examples, UE 115-a may receive a subset of a set of indices for sidelink feedback resources from base station 105-a or via sidelink communication from another UE 115, where the indices are mapped to cyclic shift pairs and physical resource blocks. In some cases, UE 115-a may receive a feedback delay value (e.g., K1) that indicates or enables UE 115-a to determine the location of a PSFCH mini-slot within a slot.

[0084] In some examples, UE 115-a may receive a sidelink message in a first time slot (e.g., in a first short physical shared channel (sPSSCH) mini-slot). In some cases, UE 115-a may send a power reservation signal in a first symbol of a second time slot following the first time slot (e.g., in symbol 0, in at least a portion of symbol 0). In some cases, UE 115-a may send a power reservation signal in a first symbol (e.g., the first symbol of a mini-slot) in the first time slot based on the corresponding sidelink message. In some cases, the power reservation signal may be based on a reference signal. In some cases, the reference signal may be a comb-based reference signal. In some cases, the comb value of the reference signal may be based on the position of the sidelink feedback mini-slot within the time slot (e.g., based on the index of the sidelink feedback mini-slot). In some cases, UE 115-a may send the power reservation signal in the same resource block position in the frequency domain as the sidelink feedback message.

[0085] Various aspects of the subject matter described herein can be implemented to achieve one or more advantages. The described techniques can support improvements in system efficiency, allowing devices to reduce latency associated with sidelink feedback channels (e.g., ACK / NACK feedback). Additionally, the described techniques can avoid multiple retransmissions and failed transmissions, reduce system latency, increase throughput, increase reliability of sidelink feedback, and improve user experience.

[0086] Figure 3 An example of an environment 300 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0087] In the illustrated example, environment 300 can include time slots 305. As shown, time slots 305 can include mini-slots 310 (e.g., 310-a, 310-b, 310-c, 310-d). As shown, each mini-slot 310 can include a first symbol period 315 (e.g., 315-a, 315-b, 315-c, 315-d), a second symbol period 320 (e.g., 320-a, 320-b, 320-c, 320-d), and a third symbol period 325 (e.g., 325-a, 325-b, 325-c, 325-d). As shown, each second symbol period 320 of time slots 305 can include one or more symbols that can immediately follow each first symbol period 315 of time slot 305 and immediately precede each third symbol period 325 of time slot 305.

[0088] In the illustrated example, the first symbol period 315 of each mini-slot 310 may include a single symbol that occurs sequentially in time within the symbol periods of each mini-slot 310 and is configured to transmit automatic gain control (AGC) information. As shown, the zeroth symbol of slot 305 (e.g., the first symbol sequentially in time, the initial first symbol period 315) may include AGC information. In some cases, the AGC information for the first symbol period 315 may be or may be based on a duplicate of the PSFCH symbol for the second symbol period 320. In some cases, the AGC information for the first symbol period 315 may be or may be based on a reference signal. In some cases, the first symbol period 315-a of mini-slot 310-a may carry an AGC power reservation signal for subsequent mini-slots (e.g., 310-b, 310-c, 310-d).

[0089] In the example shown, the second symbol period 320 of each mini-slot 310 occurs chronologically after the first symbol period of each mini-slot 310 and may be configured to transmit a sidelink feedback message (e.g., via a physical sidelink feedback channel (PSFCH)). As shown, the third symbol period 325 of each mini-slot 310 occurs chronologically after the second symbol period of each mini-slot 310 and may include a switching gap to enable the UE to switch between transmit and receive modes.

[0090] In some examples, when the sidelink data receiving UE determines that it will send a mini-slot PSFCH in a time slot, the sidelink data receiving UE may send a reservation signal at the first symbol of the mini-slot. In some cases, a PSFCH waveform may be included in each mini-slot 310. In some cases, the PSFCH waveform may be multiplexed with the corresponding sPSSCH mini-slot (e.g., a data mini-slot) in the time domain. In some cases, the PSFCH waveform may be multiplexed with the corresponding sPSSCH mini-slot in the frequency domain. In some cases, the mini-slot 310 may occupy one or more pre-configured subchannels or physical resource blocks. In some cases, the sidelink data receiving UE may adapt the PSFCH format based on the mini-slot duration in which sidelink feedback (e.g., ACK / NACK) is sent by the sidelink data receiving UE to the sidelink data transmitting UE.

[0091] In some cases, the position of a mini-slot within a time slot may correspond to a mini-slot index (e.g., the first mini-slot of a time slot maps to the first mini-slot index, the second mini-slot of a time slot maps to the second mini-slot index, etc.). For example, each mini-slot included in the time period of a time slot may have a unique mini-slot index (e.g., mini-slot 0, mini-slot 1, etc. within the first time slot), where the index value restarts at the beginning of the next time slot (e.g., mini-slot 0, mini-slot 1, etc. within the second time slot after the first time slot).

[0092] In some cases, the PSFCH resources used for sPSSCH sidelink feedback may be based on a mini-slot index and one or more subchannels of the associated sPSSCH, where each PSFCH resource is located within a mini-slot index in the time domain and at least one subchannel in the frequency domain. In some cases, the location of the sidelink feedback resources may be based on a mini-slot index and a corresponding subchannel, where each PSFCH resource is located within a mini-slot index in the time domain and one subchannel in the frequency domain. In some cases, the PSFCH resources used for sPSSCH sidelink feedback may be based on an explicit resource index and a feedback delay value (e.g., K1) indicated in sidelink control information received by a sidelink data receiving UE, where the explicit resource index corresponds to a PSFCH resource and the PSFCH resource is in a mini-slot whose location is related to the location of the sidelink control information in the time domain and the feedback delay value from the location of the sidelink control information.

[0093] In the example shown, a given mini-slot 310 may include X=3 or more symbols, depending on the mini-slot configuration (e.g., as received from a base station or a sidelink UE). In addition to the AGC symbol of the first symbol period 315 and the gap symbol of the third symbol period 325, there may be X-2 sidelink feedback symbols (e.g., PSFCH symbols) in a given mini-slot 310.

[0094] In some examples, the mini-slot configuration may include a PSFCH waveform based on PUCCH format 0 that supports one or two sidelink feedback symbols. When using a PSFCH waveform based on PUCCH format 0 (e.g., without frequency mirror hopping), a given mini-slot 310 may include three symbols (e.g., one AGC symbol, one PSFCH symbol, and one gap symbol) or four symbols (e.g., one AGC symbol, two PSFCH symbols, and one gap symbol). In the case of four symbols in a given mini-slot 310 with a PSFCH waveform based on PUCCH format 0, the UE may repeat the first PSFCH symbol in the second PSFCH symbol (one of the two PSFCH symbols being a copy of the other).

[0095] In some examples, a given mini-slot 310 may include 5 symbols (e.g., 1 AGC symbol, 3 PSFCH symbols, and 1 gap symbol). For the 5 symbols in a given mini-slot 310, the UE may repeat the first PSFCH symbol (e.g., format 0 symbol) in the second PSFCH symbol and in the third PSFCH symbol (two of the three PSFCH symbols are copies of the other).

[0096] In some examples, the mini-slot configuration may include a PSFCH waveform based on PUCCH format 1 that supports mini-slots with 4 to 14 symbols (e.g., 2 to 12 sidelink feedback symbols, plus AGC symbols and gap symbols). In some cases, the UE may apply a time-domain orthogonal cover code to one or more symbols of a given mini-slot 310 with a PSFCH waveform based on PUCCH format 1. Together with cyclic shifts, a mini-slot 310 with a PSFCH waveform based on PUCCH format 1 may provide more UE multiplexing capacity than a PUCCH format 0 mini-slot.

[0097] In some examples, a given mini-slot 310 with a PSFCH waveform based on PUCCH format 1 may include 6 symbols (e.g., 1 AGC symbol, 4 PSFCH symbols, and 1 gap symbol). In the case of 6 symbols in a given mini-slot 310, the UE may fill four PSFCH symbols based on the PUCCH format 1 waveform, where two of the four PSFCH symbols each include a reference signal (e.g., a demodulation reference signal), and the other two of the four PSFCH symbols each include an ACK / NACK modulation sequence. In some cases, the UE may apply an orthogonal cover code of length 2 on the two ACK / NACK carrying symbols. In some cases, some mini-slot configurations may be based on other PUCCH formats (e.g., PUCCH format 3, PUCCH format 4) to increase the number of available ACK / NACK bits.

[0098] In the example shown, different mini-slots 310 within the same slot 305 may have different durations. For example, as shown, first symbol period 315 and third symbol period 325 may each include one symbol, while second symbol periods 320-a and 320-c may each include two symbols, and second symbol periods 320-b and 320-d may each include one symbol. Thus, mini-slots 310-a and 310-a may each include four symbols in total, while mini-slots 310-b and 310-d may each include three symbols in total.

[0099] In some examples, the PSFCH waveform can be extended to the entire given mini-slot 310 in order to maintain constant power for the associated mini-slot UE receiver (e.g., a sidelink data receiving UE). In some cases, the sidelink data receiving UE can adjust the PSFCH duration (e.g., 1 PSFCH symbol, 2 PSFCH symbols, etc.) or format (e.g., PUCCH format 0, PUCCH format 1) based on the duration of the mini-slot in which the sidelink feedback is scheduled to be transmitted (e.g., based on sidelink control information).

[0100] In some examples, a sidelink data receiving UE may select a mini-slot in which to send sidelink feedback based on a sidelink ACK / NACK timeline. In some cases, the sidelink ACK / NACK timeline may be indicated in the sidelink control information. In some cases, the sidelink ACK / NACK timeline may be based on a fixed feedback timeline or a feedback delay value (e.g., K1) received by the UE, or both.

[0101] In some examples, a UE receiving sidelink data may send sidelink feedback in different mini-slots 310 for different PSSCH / sPSSCHs, where different mini-slots may have different durations (e.g., 3 symbols, 4 symbols, etc.). In some cases, the mini-slot duration may dynamically depend on which mini-slot 310 of time slot 305 is scheduled to carry sidelink feedback. In some cases, a sidelink data receiving UE may adjust the PFSCH duration or PFSCH format, or both, based on the dynamically dependent mini-slot duration.

[0102] Figure 4 An example of an environment 400 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0103] In the illustrated example, environment 400 may include time slots 405. As shown, time slots 405 may include mini-slots 410 (e.g., 410-a, 410-b, 410-c, 410-d). As shown, mini-slots 410-a and mini-slots 410-c (e.g., data mini-slots) may each include one or more control data blocks 440. As shown, each control data block 440 may include first sidelink control information 425, second sidelink control information 430, and sidelink data 435. As shown, mini-slots 410-b and mini-slots 410-d may each include a sidelink feedback mini-slot (e.g., a PSFCH mini-slot). In some cases, time slots 405 may precede (e.g., immediately precede) power reservation signals 420 (e.g., 420-a, 420-b, 420-c, 420-d). Thus, environment 400 may be an example in which mini-slots 410 including PSFCH signaling are time-division multiplexed with mini-slots 410 including SCI signaling, data signaling, or both.

[0104] In the illustrated example, the position of mini-slot 410-b or mini-slot 410-d within time slot 405 may be based on feedback delay 445, which is based on a feedback timing configuration. In some cases, the feedback timing configuration may be based on a fixed feedback timeline, a feedback delay value (e.g., K1) indicated in sidelink control information received by the UE (e.g., control data block 440 of the time slot preceding time slot 405), or both. In some cases, feedback delay 445 may be based on a mini-slot index indicating the position of mini-slot 410-b or mini-slot 410-d within time slot 405. In some cases, the resources of mini-slot 410-b or mini-slot 410-d may be based on the mini-slot index and one or more subchannels 415. In some cases, the resources of mini-slot 410-b or mini-slot 410-d may be based on the feedback delay value (e.g., K1) and a PSFCH resource index.

[0105] In some examples, the resources of mini-slot 410-b or mini-slot 410-d may be based on a mini-slot resource pool. In the mini-slot resource pool, a device (e.g., a sidelink UE, a base station) may specify which mini-slots 410 of time slot 405 carry PSFCH sidelink feedback (e.g., the first mini-slot 410 of time slot 405 carries PSFCH sidelink feedback and the second mini-slot 410 of time slot 405 carries PSFCH sidelink feedback). In the example shown, the second mini-slot of time slot 405 (mini-slot 410-b) and the fourth mini-slot of time slot 405 (mini-slot 410-d) are designated to carry PSFCH sidelink feedback.

[0106] Additionally or alternatively, a device may specify a periodicity for PSFCH minislots per minislot 410 of slot 405. In some cases, the specified periodicity may indicate how many other minislots occur between PSFCH minislots (e.g., every other minislot 410 of slot 405 is a PSFCH minislot, every third minislot 410 of slot 405 is a PSFCH minislot, etc.). In the example shown, slot 405 is configured with a periodicity of two PSFCH minislots (e.g., every other minislot on even-indexed minislots).

[0107] In some examples, the sidelink control information may schedule resources of a resource pool (e.g., a sidelink feedback resource pool) for use in sidelink feedback mini-slots (e.g., mini-slot 410-b and mini-slot 410-d) of time slot 405. In some cases, a set of physical resource blocks may be defined for mini-slot 410-b and mini-slot 410-d. In some cases, a bitmap (e.g., rbSetPSFCH bitmap, ) can define a set of physical resource blocks for the sidelink feedback mini-slot of time slot 405. In some cases, the set of physical resource blocks used for the sidelink feedback mini-slot of time slot 405 can overlap with a subchannel 415 in the resource pool. In some cases, one or more mini-slots 410 of time slot 405 can be time-domain multiplexed based on the physical resource blocks that overlap with the subchannel 415. In some cases, the feedback delay 445 can depend on the PSFCH mini-slot periodicity. For example, the UE processing time N1 (e.g., the time used for PSSCH decoding and feedback preparation) can be less than the number of symbols in a given mini-slot 410 (e.g., the time span of the symbol), and thus the UE can provide feedback as soon as the next mini-slot 410 includes the PSFCH.

[0108] Figure 5 An example of an environment 500 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0109] In the illustrated example, environment 500 may include time slot 505. In some cases, time slot 505 may precede (e.g., immediately precede) a power reservation signal 520 (e.g., 520-a, 520-b, 520-c, 520-d, 520-e). As shown, time slot 505 may include mini-slots 510 (e.g., 510-a, 510-b, 510-c, 510-d). As shown, each mini-slot 510 of time slot 505 may include a sidelink feedback mini-slot 535 (e.g., 535-a, 535-b, 535-c, 535-d). In the illustrated example, the position of the mini-slots 535 within time slot 505 may be based on a feedback delay 530, which is based on a feedback timing configuration. As shown, mini-slot 510-a and mini-slot 510-c may each include one or more control data blocks (e.g., control data block 540). In the example shown, each control data block 540 may include first sidelink control information 545, second sidelink control information 550, and sidelink data 555. As shown, mini-slots 510-a and 510-c may each include two control data blocks 540. Thus, environment 400 may be an example in which mini-slots 410 including PSFCH signaling are frequency-division multiplexed with mini-slots 410 including SCI signaling, data signaling, or both.

[0110] In some examples, the sidelink control information may schedule resources of a resource pool (e.g., a sidelink feedback resource pool) for a sidelink feedback mini-slot 535 of the time slot 505. In some cases, a set of physical resource blocks 525 may be defined for the mini-slot 535. In some cases, a bitmap (e.g., rbSetPSFCH bitmap, ) A set of physical resource blocks 525 for a sidelink feedback mini-slot 535 of time slot 505 may be defined in the sidelink bandwidth portion. In some cases, one or more mini-slots 510 of time slot 505 may be frequency-domain multiplexed based on one or more control data blocks 540 of a given mini-slot 510 that overlap with the given sidelink feedback mini-slot 535 of the given mini-slot 510. In some cases, non-overlapping physical resource blocks of set of physical resource blocks 525 may be defined relative to a subchannel 515 of a resource pool. As shown, a PSFCH sidelink feedback mini-slot 535 may occur in every mini-slot 510 because the sidelink feedback mini-slots 535 occupy non-overlapping physical resource blocks relative to the subchannels 515 of the resource pool. In some cases, feedback delay 530 may be minimized because the PSFCH sidelink feedback mini-slot 535 may occur in every mini-slot 510. In some cases, feedback delay 530 may depend on the PSFCH mini-slot periodicity. In some cases, the minislot configuration may configure the PSFCH minislot periodicity in terms of minislots (eg, a periodicity of 1 / 2 / 4 or X minislots).

[0111] In some examples, the sidelink feedback resource partitioning can include one or more physical resource blocks (e.g., a set of physical resource blocks). In some cases, each PSSCH in a given time slot and at a given starting subchannel can be mapped to a sidelink feedback channel physical resource block (e.g., a PSFCH PRB). In some cases, a first PSSCH in a first time slot at a first subchannel can be mapped to a first sidelink feedback channel physical resource block, and a second PSSCH in a second time slot at a second subchannel can be mapped to a second sidelink feedback channel physical resource block.

[0112] In some examples, a given time slot may be assigned a sidelink feedback channel physical resource block set (e.g., a PSFCH PRB set). In some cases, the sidelink feedback configuration maps each subchannel of a given time slot to Z physical resource blocks, where In some cases, the transmitting sidelink UE may not be allowed to dynamically control the PSFCH resource allocation, and instead the PSSCH to PSFCH resource mapping may be based on a formula (e.g., defined by the sidelink feedback configuration). In some cases, the sidelink feedback configuration maps each subchannel in a given timeslot to a physical resource block in a PSFCH PRB set. physical resource blocks, where is the number of physical resource blocks in the PSFCH PRB set, is the number of PSSCH slots corresponding to the PSFCH slot, and N subch is the number of subchannels in a given time slot. In some cases, in the mapping from PSSCH resources to PSFCH PRBs, the sidelink feedback configuration may first map the time domain resources and then map the frequency domain resources.

[0113] In some examples, a timeslot (e.g., a 14-symbol timeslot) may include multiple data mini-slots (e.g., mini-slot 510-a, mini-slot 510-c) on which UE 115-a may receive data or control information, or both. In some cases, each data mini-slot may include one or more short physical sidelink shared channels (sPSSCHs). In some cases, UE 115-a may send sidelink feedback in response to data received by UE 115-a via one or more data mini-slots. In some cases, the physical resource blocks of the mini-slot sidelink feedback channel may be divided based on the number of corresponding data mini-slots. In some cases, a given data mini-slot may be mapped to a given sidelink feedback mini-slot.

[0114] In some examples, a sidelink feedback mini-slot can be scheduled for data received in a data mini-slot, where feedback for the received data (e.g., sidelink ACK / NACK) can be sent based on the resources of the scheduled sidelink feedback mini-slot. In some cases, a mini-slot sidelink feedback channel physical resource block can be partitioned based on the number of subchannels, the number of associated data mini-slots, or both. In some cases, a mini-slot sidelink feedback channel physical resource block can be partitioned based on the product of the number of subchannels and the number of associated data mini-slots.

[0115] In some examples, a mini-slot may include a time resource block and a frequency resource span for sidelink feedback scheduling. In some cases, a mini-slot may include a number of symbols of a given slot in the time domain (e.g., a portion of a symbol of a 14-symbol slot) and one or more subchannels in the frequency domain. In some cases, each mini-slot may be mapped to a separate sidelink feedback resource partition (e.g., a PSFCH partition). In some cases, a first mini-slot may be mapped to a first sidelink feedback resource partition, a second mini-slot may be mapped to a second sidelink feedback resource partition, and so on.

[0116] In some examples, each mini-slot may be mapped to Z physical resource blocks in a set of physical resource blocks. In some cases, each mini-slot may be mapped to Z physical resource blocks in a set of physical resource blocks. physical resource blocks, where is the number of physical resource blocks in a given sidelink feedback mini-slot. In some cases, each mini-slot is mapped to a set of physical resource blocks of physical resource blocks, where is the number of physical resource blocks in the physical resource block set, is the number of sPSSCH data minislots (eg, the number of data minislots corresponding to the number of PSFCH minislots), and N subch is the number of subchannels allocated for sidelink communications. In some cases, UE 115-a may map from PSSCH to PSFCH resources in a time-first, frequency-second manner (eg, first mapping time-domain resources, then mapping frequency-domain resources).

[0117] In some examples, UE 115-a may select a PSFCH resource (e.g., determine an index value corresponding to the PSFCH resource) for transmission on one of the Z-PRB partitions corresponding to a leading subchannel of the sPSSCH (e.g., a corresponding data mini-slot) based on (K+M) mod(Z*Y), where K is a layer 1 source identifier (e.g., an 8-bit source identifier), M is a group member identifier, Z is the number of physical resource blocks in the sidelink feedback resource partition, and Y is the number of cyclic shift pairs per physical resource block. In some cases, M=0 for unicast transmissions, but is equal to the corresponding group member identifier in other cases.

[0118] In some examples, when the format of the sidelink feedback information is based on a PUCCH format 0 waveform, the number of PSFCH resources in the sidelink feedback resource partition can be based on the product of the number of physical resource blocks (Z) and the number of cyclic shift pairs per physical resource block (Y). When the format of the sidelink feedback information is based on a PUCCH format 1 waveform, the number of PSFCH resources in the sidelink feedback resource partition can be based on the product of the number of physical resource blocks (Z), the orthogonal cover code spreading factor, and the number of cyclic shift pairs per physical resource block (Y).

[0119] In some examples, the sidelink feedback configuration may be a preconfigured cyclic pair of PSFCH PRB sets and physical resource blocks. Mapped to PSFCH resource indices, and one or more sidelink UE receivers are configured with a subset of the PSFCH resource indices. In some cases, to avoid potential conflicts, the base station can configure different PSFCH PRB sets for different sidelink UE transmitters (e.g., a first PSFCH PRB set for a first sidelink UE transmitter, a second PSFCH PRB set for a second sidelink UE transmitter, etc.). In some cases, one or more sidelink UE receivers can be configured with a subset of the PSFCH resource indices associated with the sidelink UE transmitter within the PSFCH PRB set via radio resource control (RRC) (e.g., to save code points for resource indication in sidelink control information). In some cases, the sidelink UE transmitter may signal a feedback delay value (e.g., K1) to the corresponding sidelink UE receiver in the sidelink control information in the form of a mini-slot and a mini-slot PSFCH resource index (e.g., mini-slot M and PSFCH resource index L) so that the sidelink UE receiver can determine where to send and what to send in the indicated PSFCH mini-slot.

[0120] Figure 6 An example of an environment 600 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure.

[0121] In the illustrated example, environment 600 may include a time slot 605 and a control data block 680 (e.g., an sPSSCH mini-slot). As shown, control data block 680 may include first sidelink control information 665, second sidelink control information 670, and sidelink data 675. As shown, control data block 680 may be sent before a feedback delay 685 (e.g., K1). As shown, time slot 605 may include a time slot-based resource pool 625 for time slot-based UEs and a mini-slot-based resource pool 630 for mini-slot-based UEs. Environment 600 illustrates an example of a hybrid time slot / mini-slot configuration with a mini-slot-based resource pool and a time slot-based resource pool 625 that overlap in time in time slot 605. As shown, time slot 605 may include mini-slots 610 (e.g., 610-a, 610-b, 610-c).

[0122] In a hybrid deployment configuration, a conventional slot-based sidelink UE receiver may be configured to adjust automatic gain control (AGC) to account for subsequent mini-slots (e.g., after the first mini-slot). In some cases, the subsequent mini-slot may be from a different sidelink UE transmitter than the sidelink UE transmitter of the first mini-slot. In such a case, when the subsequent mini-slot does not transmit an AGC signal at the initial symbol (e.g., the 0th symbol, symbol #0) of slot 605, the slot-based sidelink UE receiver may be unable to determine the received power for the subsequent mini-slot.

[0123] In the example shown, an AGC power reservation signal may be sent at mini-slot 610-a (e.g., the 0th symbol, symbol #0, of slot 605) for an sPSSCH / PSCCH mini-slot occurring after mini-slot 610-a. In some cases, a sidelink UE transmitter intended to transmit an sPSSCH / PSCCH in a later mini-slot (e.g., after the 0th mini-slot) may send a reference signal-based (RS-based) power reservation signal (e.g., PRS 640-a, PRS 640-b) at mini-slot 610-a of slot 605. In some cases, a slot-based sidelink UE receiver may estimate the received power from a nearby sidelink UE transmitter transmitting in a later slot. In some cases, a sidelink UE transmitter intended to transmit a PSFCH mini-slot after mini-slot 610-a may also send a power reservation signal.

[0124] In some examples, when an ACK / NACK (e.g., feedback 645, feedback 650) is sent via a PSFCH mini-slot in the first mini-slot, AGC symbol 635 (sent during mini-slot 610-a) can be used as AGC training for a slot-based sidelink UE receiver. In some cases, when the sidelink UE receiver receives sPSSCH / PSCCH (e.g., via control data block 680) before mini-slot 610-a (e.g., symbol #0) and the sidelink UE receiver intends to send an ACK / NACK (e.g., feedback 645, feedback 650) via a PSFCH mini-slot (e.g., mini-slot 610-b, mini-slot 610-c) after mini-slot 610-a, the sidelink UE receiver can send a power reservation signal (e.g., PRS 640-a, PRS 640-b) during mini-slot 610-a. When an ACK / NACK occurs during the mini-slot 610 - a , the sidelink UE receiver may bypass transmitting the power reservation signal 640 .

[0125] In some examples, the power reservation signal can be an RS-based signal or a comb-based RS signal. For a comb-based RS signal, the comb values of the comb-based RS signal can be based on the position of the sidelink feedback mini-slot within the time slot (e.g., based on the index of the sidelink feedback mini-slot). In some cases, each power reservation signal (e.g., PRS 640-a, PRS 640-b) can use a different comb-based RS signal based on the position of the corresponding sidelink feedback mini-slot within time slot 605 in which the PSFCH sidelink feedback is to be transmitted. As shown, PRS 640-a transmitted in mini-slot 610-a can use comb 655 corresponding to feedback 645, while PRS 640-b transmitted in mini-slot 610-a can use comb 660 corresponding to feedback 650.

[0126] In some examples, the power reservation signal (e.g., PRS 640-a, PRS 640-b) can occupy the same location in the frequency domain as the associated PSFCH sidelink feedback or at least partially overlap in the frequency domain with the associated PSFCH sidelink feedback (e.g., feedback 645, feedback 650). As shown, PRS 650-a and feedback 645 can overlap in the frequency domain based on both being transmitted on resource block 620-a, and PRS 650-b and feedback 650 can overlap in the frequency domain based on both being transmitted on resource block 620-b. As shown, AGC symbol 635 can be sent in the same subchannel 615 as sidelink feedback message 690 in slot-based resource pool 625. In some cases, when an sPSSCH mini-slot (e.g., control data block 680) and a corresponding PSFCH mini-slot (e.g., mini-slot 610-b, mini-slot 610-c) both occur within the same time slot (e.g., time slot 605), an AGC power reservation signal (e.g., PRS 640-a, PRS 640-b) may not be sent (e.g., at mini-slot 610-a) because the corresponding sidelink UE receiver will not expect to send PSFCH sidelink feedback later in time slot 605 when the sidelink UE receiver is receiving control / data at symbol #0 of time slot 605.

[0127] Figure 7 A block diagram 700 illustrates a device 705 that supports short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure. The device 705 may be an example of aspects of the UE 115 described herein. The device 705 may include a receiver 710, a transmitter 715, and a communication manager 720. The device 705 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0128] The receiver 710 may provide a means for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., a control channel, a data channel, an information channel related to a short transmission time interval for sidelink feedback). The information may be passed to other components of the device 705. The receiver 710 may utilize a single antenna or a collection of multiple antennas.

[0129] The transmitter 715 may provide a means for transmitting signals generated by other components of the device 705. For example, the transmitter 715 may transmit information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., a control channel, a data channel, an information channel related to a short transmission time interval for sidelink feedback). In some examples, the transmitter 715 may be co-located with the receiver 710 in a transceiver module. The transmitter 715 may utilize a single antenna or a collection of multiple antennas.

[0130] The communication manager 720, the receiver 710, the transmitter 715, or various combinations thereof, or various components thereof, may be examples of means for performing various aspects of the short transmission time interval for sidelink feedback as described herein. For example, the communication manager 720, the receiver 710, the transmitter 715, or various combinations thereof, or components thereof, may support methods for performing one or more functions described herein.

[0131] In some examples, the communication manager 720, the receiver 710, the transmitter 715, or various combinations or components thereof can be implemented in hardware (e.g., using communication management circuitry). The hardware can include a processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof that is configured as or otherwise supports means for performing the functions described in this disclosure. In some examples, a processor and a memory coupled to the processor can be configured to perform one or more functions described herein (e.g., by executing instructions stored in the memory by the processor).

[0132] Additionally or alternatively, in some examples, the communication manager 720, the receiver 710, the transmitter 715, or various combinations or components thereof may be implemented using code executed by a processor (e.g., such as communication management software or firmware). If implemented using code executed by a processor, the functionality of the communication manager 720, the receiver 710, the transmitter 715, or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a central processing unit (CPU), an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., a unit configured or otherwise supporting the functions described in the present disclosure).

[0133] In some examples, the communication manager 720 can be configured to perform various operations (e.g., receive, monitor, transmit) using the receiver 710, the transmitter 715, or both, or otherwise cooperate with the receiver 510, the transmitter 515, or both. For example, the communication manager 720 can receive information from the receiver 710, send information to the transmitter 715, or be integrated with the receiver 710, the transmitter 715, or both in combination to receive information, send information, or perform various other operations as described herein.

[0134] According to examples disclosed herein, the communication manager 720 can support wireless communications at a UE. For example, the communication manager 720 can be configured to or otherwise support means for identifying, for a sidelink message scheduled for a first transmission time interval (e.g., a first mini-slot carrying data / control in a first 14-symbol time slot), a second transmission time interval (e.g., a second mini-slot in a second 14-symbol time slot occurring chronologically after the first time slot) for transmitting a sidelink feedback message corresponding to the sidelink message transmitted in the first transmission time interval, wherein both the first transmission time interval and the second transmission time interval are shorter in transmission time than a third transmission time interval (e.g., a second time slot) that includes the second transmission time interval. The communication manager 720 can be configured to or otherwise support means for transmitting automatic gain control information in a first symbol period of the second transmission time interval. The communication manager 720 can be configured to or otherwise support means for transmitting the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. The communication manager 720 may be configured or otherwise support means for switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0135] By including or configuring the communication manager 720 according to the examples described herein, the device 705 (e.g., a processor controlling or otherwise coupled to the receiver 710, the transmitter 715, the communication manager 720, or a combination thereof) can support techniques for improving system efficiency, such that the device can reduce the latency associated with sidelink feedback channels (e.g., ACK / NACK feedback). In addition, the described techniques can result in reduced processing, reduced power consumption, and more efficient use of communication resources.

[0136] Figure 8 A block diagram 800 is shown of a device 805 that supports short transmission time intervals for sidelink feedback in accordance with aspects of the present disclosure. The device 805 can be an example of aspects of the device 705 or UE 115 as described herein. The device 805 can include a receiver 810, a transmitter 815, and a communication manager 820. The device 805 can also include a processor. Each of these components can communicate with each other (e.g., via one or more buses).

[0137] The receiver 810 may provide a means for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., a control channel, a data channel, an information channel related to a short transmission time interval for sidelink feedback). The information may be passed to other components of the device 805. The receiver 810 may utilize a single antenna or a collection of multiple antennas.

[0138] The transmitter 815 may provide a means for transmitting signals generated by other components of the device 805. For example, the transmitter 815 may transmit information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., a control channel, a data channel, an information channel related to a short transmission time interval for sidelink feedback). In some examples, the transmitter 815 may be co-located with the receiver 810 in a transceiver module. The transmitter 815 may utilize a single antenna or a collection of multiple antennas.

[0139] Device 805 or its various components may be examples of means for performing various aspects of short transmission time intervals for sidelink feedback as described herein. For example, communication manager 820 may include sidelink manager 825, power manager 830, feedback manager 835, handover manager 840, or any combination thereof. Communication manager 820 may be an example of various aspects of communication manager 720 described herein. In some examples, communication manager 820 or its various components may be configured to perform various operations (e.g., receive, monitor, transmit) using, or otherwise cooperating with, receiver 810, transmitter 815, or both. For example, communication manager 820 may receive information from receiver 810, send information to transmitter 815, or be integrated with receiver 810, transmitter 815, or a combination thereof to receive information, send information, or perform various other operations described herein.

[0140] According to examples as disclosed herein, a communication manager 820 can support wireless communications at a UE. A sidelink manager 825 can be configured to or otherwise support means for identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval. A power manager 830 can be configured to or otherwise support means for transmitting automatic gain control information in a first symbol period of the second transmission time interval. A feedback manager 835 can be configured to or otherwise support means for transmitting the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. A switching manager 840 can be configured to or otherwise support means for switching the UE from operating in a transmit mode to operating in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0141] Figure 9A block diagram 900 of a communication manager 920 supporting short transmission time intervals for sidelink feedback is shown in accordance with aspects of the present disclosure. The communication manager 920 may be an example of aspects of the communication manager 720, the communication manager 820, or both, as described herein. The communication manager 920 or its various components may be examples of means for performing various aspects of the short transmission time intervals for sidelink feedback as described herein. For example, the communication manager 920 may include a sidelink manager 925, a power manager 930, a feedback manager 935, a handover manager 940, a configuration manager 945, or any combination thereof. Each of these components may communicate with each other, directly or indirectly (e.g., via one or more buses).

[0142] According to examples as disclosed herein, a communication manager 920 can support wireless communications at a UE. A sidelink manager 925 can be configured to or otherwise support means for identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval. A power manager 930 can be configured to or otherwise support means for transmitting automatic gain control information in a first symbol period of the second transmission time interval. A feedback manager 935 can be configured to or otherwise support means for transmitting the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. A switching manager 940 can be configured to or otherwise support means for switching the UE from operating in a transmit mode to operating in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0143] In some examples, the first symbol period includes an initial symbol of a second transmission time interval. In some examples, the third symbol period includes a last symbol of the second transmission time interval. In some examples, the second symbol period includes one or more symbols, the one or more symbols including every symbol between the initial symbol and the last symbol of the second transmission time interval.

[0144] In some examples, the configuration manager 945 can be configured as or otherwise support a unit for receiving configuration signaling that indicates, for a set of multiple consecutive transmission time intervals including a second transmission time interval, that a first subchannel is allocated to a sidelink feedback message and that a second subchannel, different from the first subchannel, is allocated to sidelink data or control information.

[0145] In some examples, the feedback manager 935 can be configured to or otherwise support means for receiving a bitmap indicating a set of physical resource blocks within the sidelink bandwidth portion for carrying a sidelink feedback message, wherein the sidelink feedback message is transmitted via one or more physical resource blocks in the set of physical resource blocks. In some examples, based on the second symbol period including three or fewer symbols, the sidelink feedback message is transmitted based on physical control channel format 0. In some examples, based on the second symbol period including at least four symbols, the sidelink feedback message is transmitted based on physical control channel format 1.

[0146] In some examples, when the format of the sidelink feedback message is based on a physical uplink control channel format 0 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is based on the number of physical resource blocks in the physical resource block set and the number of cyclic shift pairs per physical resource block. In some examples, when the format of the sidelink feedback message is based on a physical uplink control channel format 1 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is based on the number of physical resource blocks in the physical resource block set, the orthogonal code spreading factor, and the number of cyclic shift pairs per physical resource block.

[0147] In some examples, the third transmission time interval includes a set of multiple transmission time intervals, and the second transmission time interval and the fourth transmission time interval are included in the set of multiple transmission time intervals. In some examples, the sidelink feedback message is transmitted within a subchannel allocated for sidelink data or control information during the fourth transmission time interval.

[0148] In some examples, the feedback manager 935 can be configured as or otherwise support a unit for receiving an indication of a periodicity of a resource pool comprising a set of multiple transmission time intervals, wherein a subset of one or more transmission time intervals are allocated for sidelink feedback messages within the set of multiple transmission time intervals based on the periodicity.

[0149] In some examples, the feedback manager 935 can be configured to or otherwise support a unit for receiving a bitmap that indicates a set of physical resource blocks used to carry a sidelink feedback message during a second symbol period, where the sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

[0150] In some examples, the feedback manager 935 can be configured as or otherwise support a unit for receiving a subset of sidelink feedback resource indices from a set of multiple sidelink feedback resource indices, wherein the set of multiple sidelink feedback resource indices is mapped to a set of multiple cyclic shift pairs and a set of multiple physical resource blocks, and wherein the sidelink feedback message is sent via one or more physical resource blocks and using a cyclic shift pair corresponding to one of the sidelink feedback resource indices in the subset of sidelink feedback resource indices.

[0151] In some examples, feedback manager 935 may be configured or otherwise support means for receiving a feedback delay value indicating a position of the second transmission time interval within the third transmission time interval.

[0152] In some examples, the power manager 930 can be configured as or otherwise support a unit for sending a power reservation signal in an initial symbol of a third transmission time interval based on a first transmission time interval, in which the sidelink message is scheduled to precede the third transmission time interval including the second transmission time interval.

[0153] In some examples, the power reservation signal is based on a reference signal. In some examples, the reference signal comprises a comb-based reference signal. In some examples, the comb value of the reference signal is based on the position of the second transmission time interval within the third transmission time interval. In some examples, the power reservation signal is sent in the same resource block location in the frequency domain as the sidelink feedback message.

[0154] In some examples, the feedback manager 935 can be configured as or otherwise support a unit for selecting physical resource blocks in a physical resource block set for sending a sidelink feedback message based on a time-then-frequency mapping between the resources allocated to the sidelink message and the physical resource block set.

[0155] In some examples, the feedback manager 935 can be configured to or otherwise support a unit for selecting a sidelink feedback resource within a sidelink feedback resource partition based on a first value modulo a second value, wherein the first value is based on the sum of a layer 1 source identifier and a group member identifier associated with the sidelink message, wherein the second value is based on the product of the number of physical resource blocks in the set of physical resource blocks and the number of cyclic shift pairs per physical resource block, and wherein the sidelink feedback message is sent via the selected sidelink feedback resource.

[0156] In some examples, the sidelink feedback resource partition includes a set of physical resource blocks. In some examples, the number of physical resource blocks within the set of physical resource blocks is based on the second number of physical resource blocks allocated for sidelink feedback messages in the second transmission time interval, the number of transmission time intervals allocated for sidelink messages and corresponding to the second transmission time interval, the number of subchannels included in the sidelink feedback resource partition, or any combination thereof.

[0157] In some examples, to support sending the sidelink feedback message in the second symbol period, feedback manager 935 can be configured or otherwise support means for sending a waveform in an initial symbol of the second symbol period. In some examples, to support sending the sidelink feedback message in the second symbol period, feedback manager 935 can be configured or otherwise support means for sending a corresponding repetition of the waveform in each additional symbol of the second symbol period.

[0158] In some examples, the feedback manager 935 can be configured to or otherwise support means for selecting a second transmission time interval for transmitting the sidelink feedback message based on a feedback timing configuration and a timing of the second transmission time interval relative to the first transmission time interval. In some examples, the feedback timing configuration is based on a fixed feedback timeline, a feedback delay value indicated in sidelink control information received by the UE, or both.

[0159] Figure 10 A diagram of a system 1000 including a device 1005 supporting short transmission time intervals for sidelink feedback, in accordance with various aspects of the present disclosure, is shown. Device 1005 may be an example of, or include components of, device 705, device 805, or UE 115 as described herein. Device 1005 may wirelessly communicate with one or more base stations 105, UE 115, or any combination thereof. Device 1005 may include components for two-way voice and data communication, including components for sending and receiving communications, such as a communications manager 1020, an input / output (I / O) controller 1010, a transceiver 1015, an antenna 1025, a memory 1030, code 1035, and a processor 1040. These components may be in electrical communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, and / or electrically) via one or more buses (e.g., bus 1045).

[0160] I / O controller 1010 can manage input and output signals for device 1005. I / O controller 1010 can also manage peripheral devices that are not integrated into device 1005. In some cases, I / O controller 1010 can represent a physical connection or port to an external peripheral device. In some cases, I / O controller 1010 can utilize an operating system, such as or another well-known operating system. Additionally or alternatively, I / O controller 1010 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, I / O controller 1010 may be implemented as part of a processor (e.g., processor 1040). In some cases, a user may interact with device 1005 via I / O controller 1010 or via hardware components controlled by I / O controller 1010.

[0161] In some cases, the device 1005 may include a single antenna 1025. However, in some other cases, the device 1005 may have more than one antenna 1025, which may be capable of sending or receiving multiple wireless transmissions simultaneously. The transceiver 1015 can communicate bidirectionally via one or more antennas 1025, wired or wireless links, as described herein. For example, the transceiver 1015 can represent a wireless transceiver and can communicate bidirectionally with another wireless transceiver. The transceiver 1015 can also include a modem to modulate packets, provide the modulated packets to one or more antennas 1025 for transmission, and demodulate packets received from one or more antennas 1025. The transceiver 1015, or the transceiver 1015 and one or more antennas 1025, can be examples of the transmitter 715, the transmitter 815, the receiver 710, the receiver 810, or any combination thereof, or components thereof, as described herein.

[0162] The memory 1030 may include random access memory (RAM) or read-only memory (ROM). The memory 1030 may include computer-readable, computer-executable code 1035 that stores instructions that, when executed by the processor 1040, cause the device 1005 to perform the various functions described herein. The code 1035 may be stored in a non-transitory computer-readable medium (such as system memory or another type of memory). In some cases, the code 1035 may not be directly executed by the processor 1040, but may cause the computer (e.g., when compiled and executed) to perform the functions described herein. In some cases, the memory 1030 may include a basic I / O system (BIOS), etc., which may control basic hardware or software operations (e.g., interaction with peripheral components or devices).

[0163] The processor 1040 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some examples, the processor 1040 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated into the processor 1040. The processor 1040 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 1030) to cause the device 1005 to perform various functions (e.g., functions or tasks supporting short transmission time intervals for sidelink feedback). For example, the device 1005 or a component of the device 1005 may include a processor 1040 and a memory 1030 coupled to the processor 1040, the processor 1040 and the processor 1030 being configured to perform the various functions described herein.

[0164] According to examples disclosed herein, the communication manager 1020 may support wireless communications at a UE. The communication manager 1020 may be configured to or otherwise support means for identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval that includes the second transmission time interval. The communication manager 1020 may be configured to or otherwise support means for transmitting automatic gain control information in a first symbol period of the second transmission time interval. The communication manager 1020 may be configured to or otherwise support means for transmitting the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. The communication manager 1020 may be configured to or otherwise support means for switching the UE from operating in a transmit mode to operating in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

[0165] By including or configuring the communication manager 1020 according to the examples described herein, the device 1005 can support techniques for improving system efficiency, such that the device can reduce the latency associated with sidelink feedback channels (e.g., ACK / NACK feedback). Furthermore, the described techniques can result in improved communication reliability, reduced latency, an improved user experience associated with reduced processing, reduced power consumption, more efficient use of communication resources, improved coordination between devices, longer battery life, and improved use of processing power.

[0166] In some examples, the communication manager 1020 can be configured to use or otherwise cooperate with the transceiver 1015, one or more antennas 1025, or any combination thereof to perform various operations (e.g., receive, monitor, transmit). Although the communication manager 1020 is shown as a separate component, in some examples, one or more functions described with reference to the communication manager 1020 can be supported or performed by the processor 1040, the memory 1030, the code 1035, or any combination thereof. For example, the code 1035 can include instructions executable by the processor 1040 to cause the device 1005 to perform various aspects of the short transmission time interval for sidelink feedback as described herein, or the processor 1040 and the memory 1030 can be otherwise configured to perform or support such operations.

[0167] Figure 11 A flow chart illustrating a method 1100 for supporting short transmission time intervals for sidelink feedback according to aspects of the present disclosure is shown. The operations of the method 1100 may be implemented by a UE or components thereof as described herein. For example, the operations of the method 1100 may be implemented by a UE or components thereof as described herein. Figures 1 to 10 The described functions may be performed by the UE 115. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0168] At 1105, the method may include, for a sidelink message scheduled for a first transmission time interval, identifying a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval. The operations of 1105 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1105 may be performed as described with reference to Figure 9 The sidelink manager 925 described is executed.

[0169] At 1110, the method may include sending automatic gain control information in a first symbol period of a second transmission time interval. The operations of 1110 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1110 may be performed by the power manager 930 as described with reference to 9.

[0170] At 1115, the method may include sending a sidelink feedback message in a second symbol period of a second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. The operations of 1115 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 1115 may be performed as described in reference to Figure 9 The described feedback manager 935 is executed.

[0171] At 1120, the method may include switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval. The operations of 1120 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1120 may be performed as described with reference to Figure 9 The described switching manager 940 is performed.

[0172] Figure 12 A flow chart illustrating a method 1200 for supporting short transmission time intervals for sidelink feedback according to aspects of the present disclosure is shown. The operations of the method 1200 may be implemented by a UE or components thereof as described herein. For example, the operations of the method 1200 may be implemented by a UE as described with reference to FIG. Figures 1 to 10 The described functions may be performed by the UE 115. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0173] At 1205, the method may include, for a sidelink message scheduled for a first transmission time interval, identifying a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval. The operations of 1205 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1205 may be performed as described with reference to Figure 9 The sidelink manager 925 described is executed.

[0174] At 1210, the method may include sending automatic gain control information in a first symbol period of a second transmission time interval. The operations of 1210 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1210 may be performed by the power manager 930 as described with reference to 9.

[0175] At 1215, the method may include sending a sidelink feedback message in a second symbol period of a second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval. The operations of 1215 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 1215 may be performed as described in reference to Figure 9 The described feedback manager 935 is executed.

[0176] At 1220, the method may include switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval. The operations of 1220 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1220 may be performed as described with reference to Figure 9 The described switching manager 940 is performed.

[0177] At 1225, the method may include receiving configuration signaling indicating, for a set of a plurality of consecutive transmission time intervals including a second transmission time interval, that a first subchannel is allocated to a sidelink feedback message and a second subchannel different from the first subchannel is allocated to sidelink data or control information. The operations of 1225 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1225 may be performed by, for example, Figure 9 The configuration manager 945 described is executed.

[0178] The following provides an overview of some aspects of the disclosure:

[0179] Aspect 1: A method for wireless communication at a UE, comprising: for a sidelink message scheduled for a first transmission time interval, identifying a second transmission time interval for sending a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval; sending automatic gain control information in a first symbol period of the second transmission time interval; sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring in time sequence after the first symbol period of the second transmission time interval; and switching from operating the UE in a transmitting mode to operating the UE in a receiving mode during a third symbol period of the second transmission time interval, the third symbol period occurring in time sequence after the second symbol period of the second transmission time interval.

[0180] Aspect 2: The method according to Aspect 1 further includes: receiving configuration signaling, wherein the configuration signaling indicates that a first subchannel is allocated to a sidelink feedback message for multiple consecutive transmission time intervals including the second transmission time interval, and a second subchannel different from the first subchannel is allocated to sidelink data or control information.

[0181] Aspect 3: The method according to any one of Aspects 1 to 2 further includes: receiving a bitmap indicating a set of physical resource blocks used to carry a sidelink feedback message within the sidelink bandwidth portion, wherein the sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

[0182] Aspect 4: A method according to any one of Aspects 1 to 3, wherein the third transmission time interval includes multiple transmission time intervals, the second transmission time interval and the fourth transmission time interval are included in the multiple transmission time intervals; and the sidelink feedback message is sent within a subchannel allocated for sidelink data or control information during the fourth transmission time interval.

[0183] Aspect 5: The method according to Aspect 4 further includes: receiving an indication of a periodicity of a resource pool including the multiple transmission time intervals, wherein a subset of one or more transmission time intervals is allocated for sidelink feedback messages within the multiple transmission time intervals at least in part based on the periodicity.

[0184] Aspect 6: The method according to any one of Aspects 1 to 5 further includes: receiving a bitmap indicating a set of physical resource blocks used to carry the sidelink feedback message in the second symbol period, wherein the sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

[0185] Aspect 7: The method according to any one of Aspects 1 to 6 further includes: receiving a subset of sidelink feedback resource indices from a plurality of sidelink feedback resource indices, wherein the plurality of sidelink feedback resource indices are mapped to a plurality of cyclic shift pairs and a plurality of physical resource blocks, and wherein the sidelink feedback message is sent via one or more physical resource blocks and using a cyclic shift pair corresponding to a sidelink feedback resource index in the subset of the sidelink feedback resource indices.

[0186] Aspect 8: The method according to any one of aspects 1 to 7 further includes: receiving a feedback delay value, wherein the feedback delay value indicates a position of the second transmission time interval within the third transmission time interval.

[0187] Aspect 9: The method according to any one of Aspects 1 to 8 further includes: sending a power reservation signal in an initial symbol of the third transmission time interval based at least in part on the first transmission time interval, wherein in the first transmission time interval, the sidelink message is scheduled to precede the third transmission time interval including the second transmission time interval.

[0188] Aspect 10: The method according to aspect 9, wherein the power reservation signal is based at least in part on a reference signal.

[0189] Aspect 11: The method according to aspect 10, wherein the reference signal comprises a comb-based reference signal, and the comb value for the reference signal is based at least in part on the position of the second transmission time interval within the third transmission time interval.

[0190] Aspect 12: The method according to any one of aspects 9 to 11, wherein the power reservation signal is sent in the same resource block position as the sidelink feedback message in the frequency domain.

[0191] Aspect 13: A method according to any one of Aspects 1 to 12, wherein the sidelink feedback resource partition includes a set of physical resource blocks, and the number of physical resource blocks within the set of physical resource blocks is at least partially based on the second number of physical resource blocks allocated for sidelink feedback messages within the second transmission time interval, the number of transmission time intervals allocated to sidelink messages and corresponding to the second transmission time interval, the number of subchannels included in the sidelink feedback resource partition, or any combination thereof.

[0192] Aspect 14: The method according to Aspect 13 also includes: selecting a physical resource block in the physical resource block set for sending the sidelink feedback message based at least in part on a time-then-frequency mapping between the resources allocated to the sidelink message and the physical resource block set.

[0193] Aspect 15: A method according to any one of Aspects 13 to 14, wherein, when the format of the sidelink feedback message is at least partially based on a physical uplink control channel format 0 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is at least partially based on the number of physical resource blocks in the physical resource block set and the number of cyclic shift pairs for each physical resource block.

[0194] Aspect 16: A method according to any one of Aspects 13 to 15, wherein, when the format of the sidelink feedback message is at least partially based on a physical uplink control channel format 1 waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is at least partially based on the number of physical resource blocks in the physical resource block set, the orthogonal code spreading factor and the number of cyclic shift pairs for each physical resource block.

[0195] Aspect 17: The method according to any one of Aspects 13 to 16 further includes: selecting a sidelink feedback resource within the sidelink feedback resource partition based at least in part on a first value modulo a second value, wherein the first value is based at least in part on the sum of a layer 1 source identifier and a group member identifier associated with the sidelink message, wherein the second value is based at least in part on the product of the number of physical resource blocks in the set of physical resource blocks and the number of cyclic shift pairs for each physical resource block, and wherein the sidelink feedback message is sent via the selected sidelink feedback resource.

[0196] Aspect 18: The method of any one of Aspects 1 to 17, wherein the sidelink feedback message is sent based at least in part on physical control channel format 0 based at least in part on the second symbol period comprising three or fewer symbols.

[0197] Aspect 19: The method of any one of Aspects 1 to 18, wherein the sidelink feedback message is sent based at least in part on Physical Control Channel Format 1 based at least in part on the second symbol period including at least four symbols.

[0198] Aspect 20: A method according to any one of Aspects 1 to 19, wherein sending the sidelink feedback message in the second symbol period includes: sending a waveform on an initial symbol of the second symbol period; and sending a corresponding repetition of the waveform in each additional symbol of the second symbol period.

[0199] Aspect 21: The method according to any one of Aspects 1 to 20 also includes: selecting the second transmission time interval to send the sidelink feedback message at least in part based on the feedback timing configuration and the timing of the second transmission time interval relative to the first transmission time interval.

[0200] Aspect 22: The method of aspect 21, wherein the feedback timing configuration is based at least in part on a fixed feedback timeline, a feedback delay value indicated in sidelink control information received by the UE, or both.

[0201] Aspect 23: A method according to any one of Aspects 1 to 22, wherein the first symbol period includes an initial symbol of the second transmission time interval; the third symbol period includes a last symbol of the second transmission time interval; and the second symbol period includes one or more symbols, the one or more symbols including each symbol between the initial symbol and the last symbol of the second transmission time interval.

[0202] Aspect 24: An apparatus for wireless communication at a UE, comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any one of aspects 1 to 23.

[0203] Aspect 25: An apparatus for wireless communication at a UE, comprising at least one unit for performing the method of any one of aspects 1 to 23.

[0204] Aspect 26: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform the method of any one of aspects 1 to 23.

[0205] It should be noted that the methods described herein describe possible implementations, and that operations and steps may be rearranged or otherwise modified, and that other implementations are possible. Furthermore, aspects from two or more of the methods may be combined.

[0206] Although aspects of LTE, LTE-A, LTE-aPro, or NR systems may be described for purposes of example, and LTE, LTE-A, LTE-aPro, or NR terminology may be used throughout much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the techniques described may be applicable to various other wireless communication systems, such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16

[0207] (WiMAX), IEEE 802.20, Flash-OFDM, and other systems and radio technologies not explicitly mentioned herein.

[0208] The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the specification may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0209] The various illustrative blocks and components described in conjunction with the disclosure herein may be implemented or performed using a general purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration).

[0210] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or codes. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or a combination of any of these. Features that implement the functions may also be physically located at various locations, including being distributed such that portions of the functions are implemented at different physical locations.

[0211] Computer readable medium includes both non-transitory computer storage medium and communication medium, and communication medium includes any medium that promotes to transmit computer program from one place to another place.Non-transitory storage medium can be any available medium that can be accessed by general or special-purpose computer.By way of example and not limitation, non-transitory computer readable medium can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc (CD) ROM or other optical disc storage, disk storage or other magnetic storage device or can be used for carrying or storing desired program code unit in the form of instruction or data structure and any other non-transitory medium that can be accessed by general or special-purpose computer or general or special-purpose processor.In addition, any connection is suitably referred to as computer readable medium.For example, if software is to be sent from website, server or other remote source using coaxial cable, optical fiber cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio and microwave, then coaxial cable, optical fiber cable, twisted pair, DSL or wireless technology such as infrared, radio and microwave are included in the definition of computer readable medium. As used herein, disk and disc include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0212] As used herein (including in the claims), "or" as used in a list of items (e.g., a list of items ending with a phrase such as "at least one of" or "one or more of") indicates an inclusive list, so that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). In addition, as used herein, the phrase "based on" should not be interpreted as a reference to a closed set of conditions. For example, without departing from the scope of this disclosure, an example step described as "based on condition A" can be based on both condition A and condition B. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on". In addition, as used herein, the phrase "set" should be interpreted to include the possibility of a set having one member. That is, the phrase "set" should be interpreted in the same manner as "one or more".

[0213] The terms "determine" or "determining" encompass a wide variety of actions, and thus "determining" may include calculating, computing, processing, deriving, investigating, querying (e.g., via querying a table, database, or other data structure), ascertaining, etc. Furthermore, "determining" may also include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), etc. Furthermore, "determining" may also include resolving, selecting, choosing, establishing, and other similar actions.

[0214] In the drawings, similar components or features may have the same reference number. In addition, various components of the same type may be distinguished by following the reference number with a dash and a second reference number to distinguish between similar components. If only the first reference number is used in the specification, the description applies to any one of the similar components having the same first reference number, regardless of the second or subsequent reference numbers.

[0215] The description set forth herein in conjunction with the accompanying drawings describes exemplary configurations and does not represent all examples that can be implemented or within the scope of the claims. The term "example" as used herein means "serving as an example, instance, or illustration," rather than "preferred" or "having advantages over other examples." For the purpose of providing an understanding of the described techniques, the detailed description includes specific details. However, these techniques can be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form to avoid obscuring the concepts of the examples.

[0216] The description herein is provided to enable those skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is to be given the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for wireless communication at a user equipment (UE), comprising: at least one processor; at least one memory coupled to the at least one processor, The at least one memory stores instructions executable by the at least one processor to cause the apparatus to: identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval; transmitting a power reservation signal in an initial symbol of the third transmission time interval based at least in part on the first transmission time interval, wherein the sidelink message is scheduled in the first transmission time interval to precede the third transmission time interval including the second transmission time interval; sending automatic gain control information in a first symbol period of the second transmission time interval; sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; as well as and switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

2. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: Configuration signaling is received that indicates, for a plurality of consecutive transmission time intervals including the second transmission time interval, that a first subchannel is allocated to sidelink feedback messages and a second subchannel different from the first subchannel is allocated to sidelink data or control information.

3. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: receiving a bitmap indicating a set of physical resource blocks within the sidelink bandwidth portion for carrying a sidelink feedback message; and The sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

4. The device according to claim 1, wherein: The third transmission time interval includes a plurality of transmission time intervals, the second transmission time interval and the fourth transmission time interval being included in the plurality of transmission time intervals; as well as The sidelink feedback message is sent within a subchannel allocated for sidelink data or control information during the fourth transmission time interval.

5. The device according to claim 4, wherein The instructions are further executable by the at least one processor to cause the apparatus to: An indication of a periodicity of a resource pool comprising the plurality of transmission time intervals is received, wherein a subset of one or more transmission time intervals is allocated for sidelink feedback messages within the plurality of transmission time intervals based at least in part on the periodicity.

6. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: receiving a bitmap indicating a set of physical resource blocks used to carry the sidelink feedback message in the second symbol period; as well as The sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

7. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: receiving a subset of sidelink feedback resource indices from a plurality of sidelink feedback resource indices, wherein the plurality of sidelink feedback resource indices are mapped to a plurality of cyclic shift pairs and a plurality of physical resource blocks; and The sidelink feedback message is sent via one or more physical resource blocks and using a cyclic shift pair corresponding to one of the sidelink feedback resource indices in the subset of the sidelink feedback resource indices.

8. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: A feedback delay value is received, the feedback delay value indicating a position of the second transmission time interval within the third transmission time interval.

9. The device according to claim 1, wherein The power reservation signal is based at least in part on a reference signal.

10. The apparatus according to claim 9, wherein: The reference signal comprises a comb-based reference signal, and The comb value for the reference signal is based at least in part on a position of the second transmission time interval within the third transmission time interval.

11. The device according to claim 1, wherein The power reservation signal is sent in the same resource block position as the sidelink feedback message in the frequency domain.

12. The apparatus according to claim 1, wherein: The sidelink feedback resource partitioning comprises a set of physical resource blocks, and The number of physical resource blocks within the set of physical resource blocks is based at least in part on a second number of physical resource blocks allocated for sidelink feedback messages within the second transmission time interval, the number of transmission time intervals allocated to sidelink messages and corresponding to the second transmission time interval, the number of subchannels included in the sidelink feedback resource partition, or any combination thereof.

13. The device according to claim 12, wherein The instructions are further executable by the at least one processor to cause the apparatus to: A physical resource block in the set of physical resource blocks for transmitting the sidelink feedback message is selected based at least in part on a time-then-frequency mapping between resources allocated to the sidelink message and the set of physical resource blocks.

14. The device according to claim 12, wherein When the format of the sidelink feedback message is based at least in part on a physical uplink control channel format waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is based at least in part on the number of physical resource blocks in the set of physical resource blocks and the number of cyclic shift pairs for each physical resource block.

15. The device according to claim 12, wherein When the format of the sidelink feedback message is based at least in part on a physical uplink control channel format waveform, the number of sidelink feedback resources within the sidelink feedback resource partition is based at least in part on the number of physical resource blocks in the set of physical resource blocks, the orthogonal code spreading factor and the number of cyclic shift pairs per physical resource block.

16. The device according to claim 12, wherein The instructions are further executable by the at least one processor to cause the apparatus to: selecting a sidelink feedback resource within the sidelink feedback resource partition based at least in part on a first value modulo a second value, wherein the first value is based at least in part on a sum of a layer source identifier and a group member identifier associated with the sidelink message, and wherein the second value is based at least in part on a product of a number of physical resource blocks in the set of physical resource blocks and a number of cyclic shift pairs per physical resource block; and The sidelink feedback message is sent via the selected sidelink feedback resource.

17. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: The sidelink feedback message is sent based at least in part on physical control channel format 0 based at least in part on the second symbol period including three or fewer symbols.

18. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: The sidelink feedback message is sent based at least in part on physical control channel format 1 based at least in part on the second symbol period including at least four symbols.

19. The device according to claim 1, wherein To send the sidelink feedback message in the second symbol period, the instructions are executable by the at least one processor to cause the apparatus to: transmitting a waveform in an initial symbol of the second symbol period; as well as A corresponding repetition of the waveform is sent in each additional symbol of the second symbol period.

20. The device according to claim 1, wherein The instructions are further executable by the at least one processor to cause the apparatus to: The second transmission time interval is selected to send the sidelink feedback message based at least in part on a feedback timing configuration and a timing of the second transmission time interval relative to the first transmission time interval.

21. The device according to claim 20, wherein The feedback timing configuration is based at least in part on a fixed feedback timeline, a feedback delay value indicated in sidelink control information received by the UE, or both.

22. The apparatus of claim 1, wherein: The first symbol period includes an initial symbol of the second transmission time interval; The third symbol period includes a last symbol of the second transmission time interval; and The second symbol period includes one or more symbols including each symbol between the initial symbol and the last symbol of the second transmission time interval.

23. A method for wireless communication at a user equipment (UE), comprising: identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval; transmitting a power reservation signal in an initial symbol of the third transmission time interval based at least in part on the first transmission time interval, wherein the sidelink message is scheduled in the first transmission time interval to precede the third transmission time interval including the second transmission time interval; sending automatic gain control information in a first symbol period of the second transmission time interval; sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and and switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

24. The method according to claim 23, further comprising: Configuration signaling is received that indicates, for a plurality of consecutive transmission time intervals including the second transmission time interval, that a first subchannel is allocated to sidelink feedback messages and a second subchannel different from the first subchannel is allocated to sidelink data or control information.

25. The method of claim 23, further comprising: A bitmap is received that indicates a set of physical resource blocks within a sidelink bandwidth portion for carrying a sidelink feedback message, wherein the sidelink feedback message is sent via one or more physical resource blocks in the set of physical resource blocks.

26. The method of claim 23, wherein: The third transmission time interval includes a plurality of transmission time intervals, the second transmission time interval and the fourth transmission time interval being included in the plurality of transmission time intervals; as well as The sidelink feedback message is sent within a subchannel allocated for sidelink data or control information during the fourth transmission time interval.

27. The method according to claim 26, further comprising: An indication of a periodicity of a resource pool comprising the plurality of transmission time intervals is received, wherein a subset of one or more transmission time intervals is allocated for sidelink feedback messages within the plurality of transmission time intervals based at least in part on the periodicity.

28. An apparatus for wireless communication at a user equipment (UE), comprising: means for identifying, for a sidelink message scheduled for a first transmission time interval, a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval; means for transmitting a power reservation signal in an initial symbol of the third transmission time interval based at least in part on the first transmission time interval, wherein the sidelink message is scheduled to precede the third transmission time interval including the second transmission time interval in the first transmission time interval; means for sending automatic gain control information in a first symbol period of said second transmission time interval; means for sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; and Means for switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

29. A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE), the code comprising instructions executable by a processor to: For a sidelink message scheduled for a first transmission time interval, identifying a second transmission time interval for transmitting a sidelink feedback message corresponding to the sidelink message, wherein the first transmission time interval and the second transmission time interval are both shorter in duration than a third transmission time interval including the second transmission time interval; transmitting a power reservation signal in an initial symbol of the third transmission time interval based at least in part on the first transmission time interval, wherein the sidelink message is scheduled in the first transmission time interval to precede the third transmission time interval including the second transmission time interval; sending automatic gain control information in a first symbol period of the second transmission time interval; sending the sidelink feedback message in a second symbol period of the second transmission time interval, the second symbol period occurring chronologically after the first symbol period of the second transmission time interval; as well as and switching from operating the UE in a transmit mode to operating the UE in a receive mode during a third symbol period of the second transmission time interval, the third symbol period occurring chronologically after the second symbol period of the second transmission time interval.

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