Abstract: Methods, systems, and devices for wireless communications are described. The described techniques generally support downlink transmissions. For example, a user equipment (UE) may receive a resource configuration for reception of a downlink transmission within a repetition window, the resource configuration including an indicator of a repetition window size for the downlink transmission. The UE may monitor, according to the resource configuration, one or more transmission time intervals (TTIs) of the repetition window for reception of the downlink transmission. In some cases, the downlink transmission may be a grant-free downlink transmission. Here, the UE may attempt to decode the grant-free downlink transmission during the one or more TTIs based at least in part on the repetition window size.

Abstract: Methods, systems, and devices for wireless communication are described. In one example, an indication in a first control message in a control region of a first transmission time interval (TTI) identifies a data region of the first TTI. A data region of the second TTI may be identified based on a grant of resources received in a second control message of a second TTI, where the data region of the first TTI and the control region of the second TTI are frequency division multiplexed with the data region of the second TTI. Other examples include a downlink grant at the beginning of a control region and uplink grants at the end of the control region. In other examples, a downlink grant for a user equipment (UE) may include an indication of resources allocated to the UE in that resource block and a second resource block.

Abstract: Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a receiving device may determine an uplink-downlink time division duplex (TDD) shortened transmission time interval (sTTI) configuration; determine an initial sTTI, within the uplink-downlink TDD sTTI configuration, for reception of an initial communication; and monitor one or more sTTIs, subsequent to the initial sTTI, for reception of at least one repetition or retransmission of the initial communication, wherein the one or more sTTIs are determined based at least in part on a pattern associated with the uplink-downlink TDD sTTI configuration. Numerous other aspects are provided.

Abstract: Methods, systems, and devices for wireless communication are described that provide for reduced timing between certain downlink communications and responsive uplink communications relative to certain legacy systems (e.g., legacy LTE systems). A user equipment (UE) or base station may be capable of operating using two or more timing configurations that each include an associated time period between receipt of a downlink communication (e.g., a grant of uplink resources or shared channel data) and a responsive uplink communication (e.g., an uplink transmission using the granted uplink resources or feedback of successful reception of the shared channel data). In cases where a UE or base station are capable of two or more timing configurations, a timing configuration for a transmission may be determined and the responsive uplink communication transmitted according to the determined timing configuration.

Abstract: An example data structure for managing user equipment communications in a wireless communications system is presented, as well as methods and apparatuses configured to implement the data structure. For instance, the data structure may include a downlink subframe comprising two slots and including one or more quick downlink channels having a single-slot transmission time interval. In addition, the example data structure may include one or more resource element blocks each comprising one or more resource elements into which a frequency bandwidth is divided within one or both of the two slots, wherein each of the one or more resource element blocks comprises a control channel region or a data channel region. Furthermore, the example data structure may include one or more resource grants, located within one or more control channel regions, for one or more user equipment served by the one or more quick downlink channels.

Abstract: Techniques are described for wireless communication at a user equipment (UE). One method includes receiving a downlink grant for a downlink transmission; transmitting channel quality feedback at a first time triggered by receipt of the downlink grant, the first time occurring during a first transmission time interval (TTI); and transmitting acknowledgement/negative-acknowledgement (ACK/NACK) feedback for the downlink transmission at a second time triggered by receipt of the downlink grant, the second time occurring during a second TTI, and the second TTI occurring later in time than the first TTI.

Abstract: Various aspects described herein relate to receiving wireless communications from an access point, determining resources of the wireless communications associated with a search space for control information in the received wireless communications, and performing one or more of a set of blind decodes over the search space to decode at least low latency control information associated with a low latency communication technology, wherein the low latency communication technology utilizes a transmission time interval (TTI) having a duration that is less than a subframe of a legacy communication technology.

Abstract: Various aspects described herein relate to managing ultra low latency (ULL) communications over a plurality of component carriers (CC). A configuration for aggregating a set of CCs can be received, wherein the set of CCs includes at least a primary cell and a secondary cell. Based on the received configuration, at least the primary cell can be communicated with for legacy communications, wherein the legacy communications are based on a first transmission time interval (TTI) having a first duration. Based on the received configuration, the primary cell and the secondary cell can be communicated with for ULL communications, wherein the ULL communications are based on a second TTI having a second duration that is less than the first duration.

Abstract: Techniques are described for wireless communication. A first method includes winning a contention for access to an unlicensed radio frequency spectrum band, and transmitting at least a portion of a channel usage beacon signal (CUBS) over the unlicensed radio frequency spectrum band. The at least portion of the CUBS is transmitted in a number of frequency interlaces of the unlicensed radio frequency spectrum band. A second method includes winning a contention for access to an unlicensed radio frequency spectrum band; determining whether the contention is won within a threshold time before a next symbol period boundary; and transmitting at least a portion of a CUBS over the unlicensed radio frequency spectrum band. The at least portion of the CUBS is transmitted during a preamble including a fractional period of a first symbol period. The at least portion of the CUBS may be based at least in part on the determining.

Abstract: Methods, systems, and devices for wireless communications are described. To satisfy a (block error rate) BLER target for a transmission of a transport block while limiting latency (e.g., keeping latency within a latency budget), base stations and user equipments (UEs) may support techniques for utilizing repetition-based transmissions of the transport block in combination with hybrid automatic repeat request (HARQ) retransmissions of the transport block. That is, base stations and UEs may support techniques for transmitting multiple repetitions (i.e., copies) of the transport block without first receiving HARQ feedback, in addition to retransmitting one or more copies of the transport block when a receiving device fails to successfully decode at least one of the originally transmitted copies of the transport block (as indicated through HARQ feedback).

Abstract: Methods, systems, and devices for wireless communication are described. In one example, an indication in a first control message in a control region of a first transmission time interval (TTI) identifies a data region of the first TTI. A data region of the second TTI may be identified based on a grant of resources received in a second control message of a second TTI, where the data region of the first TTI and the control region of the second TTI are frequency division multiplexed with the data region of the second TTI. Other examples include a downlink grant at the beginning of a control region and uplink grants at the end of the control region. In other examples, a downlink grant for a user equipment (UE) may include an indication of resources allocated to the UE in that resource block and a second resource block.

Abstract: Certain aspects of the present disclosure provide techniques that may be used for low latency communications. For example, aspects allow a single group acknowledgement to be used to acknowledge a plurality of low latency transmissions. An exemplary method generally includes receiving, from a base station, a plurality of downlink channel transmissions, wherein each of the downlink channel transmissions is sent using a first transmission time interval (TTI) that is reduced relative to a legacy TTI and providing, in a single uplink channel transmission sent using a second TTI that is larger than the first TTI, a group acknowledgement indicating whether or not the downlink channel transmissions were successfully received by a UE.

Abstract: Methods, systems, and devices for wireless communication are described. A user equipment (UE) and a base station may use low latency communications to improve the throughput of a wireless link. To facilitate efficient low latency communication, the UE may send UE-initiated CSI reports in addition to periodic and base station-initiated reports. For example, the UE may, in various examples, send UE-initiated CSI reports using contention based spectrum, using a request-to-transmit, or using a CSI differential (i.e., an indicator of a change in channel conditions). The base station may schedule different UEs for uplink low latency communication by providing resources to each UE for CSI and scheduling requests (SRs) using coherent or non-coherent uplink transmissions. The CSI and SR may also be combined with uplink feedback.

Abstract: Methods, systems, and devices are described for wireless communication. One method may include receiving, at a first base station, at least one clear channel assessment (CCA)-exempt transmission (CET) indicating timing information of at least a second base station over a shared spectrum. A timing of the first base station may be adjusted based on the received timing information of the second base station. Another method of wireless communication may include identifying a CCA slot assigned to a first base station for a frame, which may be associated with time synchronization, of a shared spectrum. A CCA may be performed at the identified CCA slot for the frame. When the CCA is successful, a first timing information of the first base station may be selectively transmitted during the frame. When the CCA is unsuccessful, a second timing information of a second base station may be listened for during the frame.

Abstract: Methods, systems, and devices are described for wireless communication at a device. Demodulation reference signals (DMRS) may be used to facilitate demodulation of low latency control or data channels, or both. A wireless communication device may, for example, identify a carrier configuration with transmission time intervals (TTIs) of different durations. A carrier may be configured with TTIs that support low latency operations. A DMRS pattern for resources of a low latency TTI may be determined, and that first DMRS pattern may be based on a DMRS pattern for resources of another, longer-duration TTI. Devices may thus communicate using resources of a low latency TTI based on the first DMRS pattern. For example, a user equipment (UE) may demodulate resources of a low latency channel using the first DMRS pattern, and the first DMRS pattern may be consistent with DMRS patterns supporting non-low latency within a common wireless system.

Abstract: Methods, systems, and devices for wireless communication are described. A receiving device may detect a signal associated with low latency transmissions and decode a non-low latency communication accordingly. The receiving device may receive an indicator from a transmitting device that indicates where and when low latency communications occur. The indication may specify frequency resources or symbols used by the low latency communication. The indicator may be transmitted during the same subframe as the low latency communication, at the end of a subframe, or during a subsequent subframe. The receiving device may use the indicator to mitigate low latency interference, generate channel estimates, and reliably decode the non-low latency communication. In some cases, the interfering low latency communication may occur within the serving cell of the receiving device; or the interfering low latency communication may occur in a neighboring cell.

Abstract: Methods, systems, and devices for wireless communication are described. A user equipment (UE) may determine separate uplink (UL) power limitations for multiple transmission time interval (TTI) durations based on distinct power control parameters. In some cases, an adjustment factor or a power backoff may be applied to communications using one TTI duration to ensure that total transmit power does not exceed a threshold. The UE and the serving base station may also identify one or more demodulation reference signal (DMRS) windows. UL data transmissions may be demodulated based on a DMRS sent during the same window. Transmit power control (TPC) commands may be applied at the beginning of each window. However, if an UL transmission is scheduled at the beginning of the window, the UE may wait until a DMRS transmission or until no more transmissions are scheduled for the window before applying the TPC adjustment.

Abstract: Methods, systems, and devices for wireless communication are described. A user equipment (UE) and a base station may use low latency communications to improve the throughput of a wireless link. To facilitate efficient low latency communication, the UE may send UE-initiated CSI reports in addition to periodic and base station-initiated reports. For example, the UE may, in various examples, send UE-initiated CSI reports using contention based spectrum, using a request-to-transmit, or using a CSI differential (i.e., an indicator of a change in channel conditions). The base station may schedule different UEs for uplink low latency communication by providing resources to each UE for CSI and scheduling requests (SRs) using coherent or non-coherent uplink transmissions. The CSI and SR may also be combined with uplink feedback.

Abstract: Methods, systems, and devices for wireless communication are described. A wireless device such as a user equipment (UE) or a base station may identify a set of resource element groups (REGs) for low latency communication, and each REG may include a portion of a different resource block (RB) of a set of RBs (e.g., a set of non-contiguous RBs). The device may then map an uplink control channel to the selected REGs and communicate on the uplink control channel accordingly. Reference signals may also be transmitted in the same RBs, and the REGs may be mapped around the resources used for reference signals. In some cases, multiple UEs may transmit uplink control data using the same resources using code division multiplexing (CDM) (e.g., if the control payload is relatively small). In other cases, multiple UEs may be frequency division multiplexed (FDM).

Abstract: Techniques are described for wireless communication. One method includes winning a contention for access to an unlicensed radio frequency spectrum band, transmitting a request message upon winning the contention for access to the unlicensed radio frequency spectrum band, and receiving a response message over the unlicensed radio frequency spectrum band. The request message is transmitted by a user equipment (UE) on an enhanced physical random access channel (ePRACH) or shortened ePRACH (SePRACH), to access a cell that operates in the unlicensed radio frequency spectrum band. The response message is received in response to transmitting the request message, and the request message may be transmitted irrespective of whether a base station has gained access to the unlicensed radio frequency spectrum band.