Patent Description:
These systems may be capable of supporting communication with multiple users by sharing the available system resources (such as time, frequency, and power).

<CIT> discloses methods and apparatus for power saving in a wireless network. A Wireless Transmit/Receive Unit (WTRU) may comprise a transmitter, a receiver, and a processor. The processor may determine a processing state pertaining to behavior of the WTRU and determine a minimum amount of resources to be processed for one or more sets of physical resources based on the determined processing state. Each set of physical resources may comprise resources in time, and any of frequency or space. For each respective set of physical resources, the time may comprise a frame structure associated with a numerology applicable to the respective set of physical resources, the frequency may comprise any of a frequency location, a bandwidth, or the numerology, and the space may comprise one or more beams. The processor may process the determined minimum amount of resources of the one of more sets of physical resources.

Technical document 3GPP TS <NUM> v15. <NUM> discloses the medium access control (MAC) protocol specification.

The systems, methods and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosure may be implemented in an apparatus for wireless communications. The apparatus includes a first interface and a processing system. The first interface is configured to obtain monitoring information for a downlink control channel while operating in an active state of a discontinuous reception (DRX) mode and obtain a downlink control information (DCI) message scheduling a downlink data message based on the monitoring information, where the DCI message indicates a feedback transmission opportunity (TxOP) for the downlink data message. The processing system is configured to activate a first timer subsequent to the feedback TxOP for the downlink data message and based on an end of the feedback TxOP and activate a second timer upon expiration of the first timer, where the processing system remains in the active state of the DRX mode while the second timer is running.

The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device, system or network that is capable of transmitting and receiving radio frequency signals according to any of the Institute of Electrical and Electronics Engineers (IEEE) <NUM> standards, or any of the IEEE <NUM> standards, the Bluetooth® standard, code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), <NUM>×EV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless, cellular or internet of things (IoT) network, such as a system utilizing <NUM>, <NUM> or <NUM>, or further implementations thereof, technology.

In some systems, a user equipment (UE) may support hybrid automatic repeat request (HARQ) processes while operating in a discontinuous reception (DRX) mode. In the DRX mode, the UE may switch between an active state (for example, during which the UE monitors a downlink control channel for downlink control information (DCI) messages) and an inactive state. The UE may continue operating in the active state based on one or more timers. For example, a set of timers may maintain the active state for the UE while at least one timer of the set of timers is running. Each timer may correspond to a specific activation trigger, a specific deactivation trigger, and a specific active duration. Examples of timers that maintain the active state at the UE may include an ON duration timer, an inactivity timer, and a retransmission timer. In some implementations, the UE may support other timers that may not maintain the active state, but may trigger activation of other timers or operations, such as a round-trip time (RTT) timer. If no timer maintaining the active state is currently running at the UE, the UE may operate in a sleep mode (for example, during which the UE may refrain from monitoring the downlink control channel).

In some implementations, during an active state, a UE may receive a DCI message from a base station in a control channel (such as a physical downlink control channel (PDCCH)). The DCI message may indicate a scheduled downlink transmission on a channel (such as a physical downlink shared channel (PDSCH)) as well as a feedback transmission opportunity (TxOP) for the data in the downlink transmission. The UE may receive the scheduled transmission and may transmit a HARQ positive acknowledgment (ACK) or negative acknowledgment (NACK) during the configured feedback TxOP, which may be referred to as a HARQ ACK/NACK opportunity. If the UE determines to transmit a NACK for the downlink data, the UE may trigger an RTT timer and a retransmission timer to keep the UE in the active state and monitoring for retransmission information for the data.

In some networks (such as a New Radio (NR) unlicensed network), the UE may communicate with the base station in an unlicensed spectrum. For the UE to transmit on an unlicensed channel, the UE may perform a channel access procedure, such as a listen-before-talk or listen-before-transmit (LBT) procedure, to gain access to the channel. In this way, the UE may transmit on the unlicensed channel when the channel is not being utilized by another device. In some implementations, LBT failure may occur such that the UE may not gain access to the channel during the HARQ feedback TxOP, and the UE may refrain from transmitting the HARQ feedback in the TxOP. When the UE has a NACK to transmit and LBT failure occurs (or the UE otherwise drops a feedback transmission), the UE may implement timer rules to keep the UE active and monitoring the downlink control channel.

In some implementations, the UE may activate a timer, such as an RTT timer, based on the end of a feedback TxOP (for example, as opposed to after transmitting feedback information). Activating the RTT timer based on a scheduled feedback TxOP, whether or not the UE transmits a HARQ-ACK message in the feedback TxOP, may keep the UE from returning to an inactive mode when the UE has a NACK to transmit. For example, the RTT timer may trigger a retransmission timer, and the retransmission timer may maintain the UE in the active state. Additionally, or alternatively, a base station may schedule multiple opportunities for HARQ feedback for a single downlink data message. In some implementations, the UE may start the RTT timer after the first scheduled HARQ feedback TxOP and may refrain from starting the RTT timer after subsequent scheduled HARQ feedback TxOPs for the same HARQ process. In some other implementations, the UE may start and restart the RTT timer after each scheduled HARQ feedback TxOP for the same HARQ process.

Restarting the RTT timer may trigger reactivation of the corresponding retransmission timer. In some implementations, a retransmission timer for a HARQ process may still be running when the RTT timer for the HARQ process is reactivated (for example, based on multiple feedback TxOPs). In some such implementations, the UE may continue running the retransmission timer until expiry of the RTT timer and may restart the retransmission timer upon the RTT timer expiration. In some other such implementations, the UE may stop the retransmission timer upon reactivation of the RTT timer and may restart the retransmission timer upon the RTT timer expiration.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some implementations, activating an RTT timer based on the end of a HARQ feedback TxOP may extend an active state for a UE (for example, even if the UE does not transmit the HARQ feedback in the TxOP). Extending the active state for the UE may significantly reduce the latency associated with HARQ feedback. For example, if the UE determines to transmit a NACK but returns to an inactive state prior to receiving an additional DCI message scheduling an additional feedback TxOP or a data retransmission, the UE may not transmit the NACK in a feedback message or receive a downlink data retransmission until a next DRX cycle. This may introduce significant latency into the HARQ operation and data reception, especially for relatively long DRX cycles. By activating a timer based on the end of a feedback TxOP to maintain an active state and continue monitoring the downlink control channel, the UE may receive a DCI message scheduling an additional feedback opportunity or downlink data retransmission in the current DRX cycle, supporting a faster turnaround of feedback information, data retransmission, or both. Additionally, or alternatively, managing timers for multiple feedback TxOPs for a same downlink data message may increase the likelihood that the UE remains active and transmits feedback information in the current DRX cycle.

<FIG> shows an example of a wireless communications system <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The wireless communications system <NUM> may include base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some implementations, the wireless communications system <NUM> may be an LTE network, an LTE-A network, an LTE-A Pro network, or a New Radio (NR) network. In some implementations, the wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (such as mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

Base stations <NUM> may be dispersed throughout a geographic area to form the wireless communications system <NUM> and may be devices in different forms or having different capabilities. Base stations <NUM> and UEs <NUM> may wirelessly communicate via one or more communication links <NUM>. Each base station <NUM> may provide a coverage area <NUM> over which UEs <NUM> and the base station <NUM> may establish communication links <NUM>. The coverage area <NUM> may be an example of a geographic area over which a base station <NUM> and a UE <NUM> support the communication of signals according to one or more radio access technologies.

UEs <NUM> may be dispersed throughout a coverage area <NUM> of the wireless communications system <NUM>, and each UE <NUM> may be stationary, or mobile, or both at different times. UEs <NUM> may be devices in different forms or having different capabilities. The UEs <NUM> described herein may be able to communicate with various types of devices, such as other UEs <NUM>, base stations <NUM>, or network equipment (such as core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), or a combination thereof, as shown in <FIG>.

Base stations <NUM> may communicate with the core network <NUM>, or with one another, or both. For example, base stations <NUM> may interface with the core network <NUM> through backhaul links <NUM> (such as via an S1, N2, N3, or another interface). Base stations <NUM> may communicate with one another over backhaul links <NUM> (such as via an X2, Xn, or another interface) either directly (such as directly between base stations <NUM>), or indirectly (such as via core network <NUM>), or both. In some implementations, backhaul links <NUM> may be or include one or more wireless links.

One or more of base stations <NUM> described herein may include or may be referred to by a person of ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology.

A UE <NUM> 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 suitable terminology, where the "device" also may be referred to as a unit, a station, a terminal, or a client, among other examples. A UE <NUM> also may 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 implementations, a UE <NUM> may include or be referred to as a wireless local loop (WLL) station, an IoT device, an Internet of Everything (IoE) device, a machine type communications (MTC) device, or the like, which may be implemented in various objects such as appliances, vehicles, meters, or the like.

The UEs <NUM> described herein may be able to communicate with various types of devices, such as other UEs <NUM> that may sometimes act as relays as well as base stations <NUM> and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, relay base stations, and the like, as shown in <FIG>.

UEs <NUM> and base stations <NUM> may wirelessly communicate with one another via one or more communication links <NUM> over one or more carriers. The term "carrier" may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communication links <NUM>. For example, a carrier used for a communication link <NUM> may include a portion of a radio frequency spectrum band (such as a bandwidth part (BWP)) that is operated according to physical layer channels for a given radio access technology (such as LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (such as synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling.

In some implementations (such as in a carrier aggregation configuration), a carrier also may have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (such as an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by UEs <NUM>. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by UEs <NUM> via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (such as of the same or a different radio access technology).

Communication links <NUM> shown in the wireless communications system <NUM> may include uplink transmissions from a UE <NUM> to a base station <NUM>, or downlink transmissions from a base station <NUM> to a UE <NUM>. Carriers may carry downlink or uplink communications (such as in an FDD mode) or may be configured to carry downlink and uplink communications (such as in a TDD mode).

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some implementations, the carrier bandwidth may be referred to as a "system bandwidth" of the carrier or the wireless communications system <NUM>. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> megahertz (MHz)). Devices of the wireless communications system <NUM> (such as base stations <NUM>, UEs <NUM>, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some implementations, the wireless communications system <NUM> may include base stations <NUM>, or UEs <NUM>, or a combination thereof that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some implementations, each served UE <NUM> may be configured for operating over portions (such as a sub-band, a BWP) or all of a carrier bandwidth.

Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (such as using multi-carrier modulation (MCM) techniques 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 consist of one symbol period (such as a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (such as the order of the modulation scheme, the coding rate of the modulation scheme, or both). A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (such as spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE <NUM>.

Time intervals for base stations <NUM> or UEs <NUM> may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of seconds, where may represent the maximum supported subcarrier spacing, and may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (such as <NUM> milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (such as ranging from <NUM> to <NUM>).

In some implementations, a frame may be divided (such as in the time domain) into subframes, and each subframe may be further divided into a number of slots. Each slot may include a number of symbol periods (such as depending on the length of the cyclic prefix prepended to each symbol period). Excluding the cyclic prefix, each symbol period may contain one or more (such as) sampling periods.

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (such as in the time domain) of the wireless communications system <NUM> and may be referred to as a transmission time interval (TTI). In some implementations, the TTI duration (such as the number of symbol periods in a TTI) may be variable. Additionally, or alternatively, the smallest scheduling unit of the wireless communications system <NUM> may be dynamically selected (such as in bursts of shortened TTIs (sTTIs)).

A control region (such as 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 or a subset of the system bandwidth of the carrier. One or more control regions (such as CORESETs) may be configured for a set of UEs <NUM>. For example, UEs <NUM> may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (such as control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size.

UEs <NUM> may be designed to support ultra-reliable, low-latency, or critical functions (such as mission critical functions).

In some implementations, a UE <NUM> also may be able to communicate directly with other UEs <NUM> over a device-to-device (D2D) communication link <NUM> (such as using a peer-to-peer (P2P) or D2D protocol). In some implementations, groups of UEs <NUM> communicating via D2D communications may utilize a one-to-many (<NUM>:M) system in which each UE <NUM> transmits to every other UE <NUM> in the group. In some implementations, a base station <NUM> facilitates the scheduling of resources for D2D communications. In some other examples, D2D communications are carried out between UEs <NUM> without the involvement of a base station <NUM>.

The core network <NUM> may be an evolved packet core (EPC) or <NUM> core (5GC), which may include at least one control plane entity that manages access and mobility (such as a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (such as a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for UEs <NUM> served by base stations <NUM> associated with the core network <NUM>. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services <NUM>. The operators IP services <NUM> may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service.

Each access network entity <NUM> may communicate with UEs <NUM> through a number of other access network transmission entities <NUM>, which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). In some configurations, various functions of each access network entity <NUM> or base station <NUM> may be distributed across various network devices (such as radio heads and ANCs) or consolidated into a single network device (such as a base station <NUM>).

The wireless communications system <NUM> may operate using one or more frequency bands, typically in the range of <NUM> megahertz (MHz) to <NUM> gigahertz (GHz). UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to UEs <NUM> located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter ranges (such as less than <NUM> kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below <NUM>.

When operating in unlicensed radio frequency spectrum bands, devices such as base stations <NUM> and UEs <NUM> may employ carrier sensing for collision detection and avoidance. In some implementations, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (such as LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, D2D transmissions, or the like.

A base station <NUM> or UE <NUM> may be equipped with multiple antennas, which 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 <NUM> or UE <NUM> may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. In some implementations, antennas or antenna arrays associated with a base station <NUM> may be located in diverse geographic locations. Additionally, or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

Beamforming, which also may be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (such as a base station <NUM> or a UE <NUM>) to shape or steer an antenna beam (such as a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (such as with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation).

UEs <NUM> and base stations <NUM> may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique for increasing the likelihood that data is received correctly over a communication link <NUM>. HARQ may include a combination of error detection (such as using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (such as automatic repeat request (ARQ)). HARQ may improve throughput at the medium access control (MAC) layer in poor radio conditions (such as low signal-to-noise conditions). In some implementations, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In some other implementations, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

In some implementations, a UE <NUM> may operate in DRX mode in a wireless communications system <NUM> (such as in an unlicensed spectrum or a licensed spectrum). To transmit in an unlicensed spectrum, the UE <NUM> may perform a channel access procedure, such as an LBT procedure, such that the UE <NUM> may monitor a channel prior to transmitting on the channel. The UE <NUM> may transmit on the channel if the channel is free from transmissions by other devices. In some implementations, LBT failure may occur such that the channel the UE <NUM> is monitoring may be busy during a TxOP for the UE <NUM>. The UE <NUM> may refrain from transmitting a message (such as HARQ feedback) in the configured opportunity because of the LBT failure. In some implementations, to maintain the UE <NUM> in an active DRX state despite the LBT failure, the UE <NUM> may activate a timer based on the end of a feedback TxOP. Additionally, or alternatively, the UE <NUM> may support multiple TxOPs for a same downlink data transmission.

<FIG> shows an example of a wireless communications system <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The wireless communications system <NUM> may include a base station <NUM>-a and a UE <NUM>-a, which may be examples of a base station <NUM> and a UE <NUM> as described with reference to <FIG>. The base station <NUM>-a may serve a geographic coverage area <NUM>-a. In some implementations, the base station <NUM>-a and the UE <NUM>-a may implement HARQ procedures while the UE <NUM>-a operates in a DRX mode. For example, the UE <NUM>-a may receive a DCI message <NUM> and a subsequent scheduled downlink data transmission <NUM> (for example, via one or more downlink channels <NUM>-a) and may transmit HARQ feedback <NUM> (for example, via an uplink channel <NUM>-b) based on whether the UE <NUM>-a successfully decodes the downlink data transmission <NUM>. The base station <NUM>-a may determine whether to retransmit information based on received HARQ feedback <NUM>.

A UE <NUM> may operate in a DRX mode to conserve battery power. In a DRX mode, the UE <NUM> may have an inactive mode or state (such as a low power state) and an active mode or state. In the active mode, the UE <NUM> may monitor a downlink control channel (for example, a downlink channel <NUM>-a) for DCI messages <NUM>. In the inactive mode, the UE <NUM> may be "asleep" and may not monitor the downlink control channel to reduce power consumption at the UE <NUM>. The UE <NUM> may remain active depending on the activity of one or more timers. Timers may activate at the occurrence of certain events and remain running for a preconfigured duration. The activation of some timers may cause the UE <NUM> to activate (for example, wake up and begin monitoring the downlink control channel) or remain active while the activation of other timers may not impact the DRX state of the UE <NUM>. Upon the expiry of some timers (such as at the end of a timer's runtime), the UE <NUM> may become inactive (for example, enter a sleep state to conserve processing power). While the UE <NUM> is inactive, the UE <NUM> may not transmit messages, receive messages, monitor a channel (such as a PDCCH), or a combination thereof.

Some examples of timers that may control the active time of a UE <NUM> include an ON duration timer, an inactivity timer, a retransmission timer, or some combination thereof. Additional examples of timers may include an RTT timer. For example, the UE <NUM> may periodically start an ON duration timer to wake up from an inactive mode. The UE <NUM> may start an inactivity timer (for example, a drx-InactivityTimer) after receiving a DCI message <NUM> scheduling a new transmission, such as a downlink data transmission <NUM> or an uplink transmission. The UE <NUM> may start an RTT timer (for example, a drx-HARQ-RTT-TimerDL) based on HARQ process for a downlink data transmission <NUM>. The UE <NUM> may start a retransmission timer (for example, a drx-RetransmissionTimerDL) after the expiry of a corresponding RTT timer for a HARQ process if the UE <NUM> did not successfully receive data for the corresponding HARQ process. Each of these timers may have a corresponding maximum timer length. When a timer is activated, the timer may run for the maximum timer length before stopping. If all timers controlling the active time of the UE <NUM> are inactive (for example, after expiration of the last timer controlling the active time), the UE <NUM> may return to the inactive mode.

In some implementations, while in an active state, a UE <NUM> may receive a DCI message <NUM> from a base station <NUM> via a control channel (such as the PDCCH). The DCI message <NUM> may indicate a scheduled transmission on another channel (such as the PDSCH). For example, the DCI message <NUM> may include a downlink grant granting resources for a downlink data transmission <NUM>. The UE <NUM> may receive the scheduled transmission and may transmit a HARQ ACK/NACK in a HARQ-ACK message (for example, the HARQ feedback <NUM>) during a configured HARQ feedback TxOP. In some implementations, the UE <NUM> may activate one or more timers after the reception of the DCI message <NUM>, after the transmission of the HARQ feedback <NUM> during a HARQ feedback TxOP, after the expiry of a previous timer, or based on any combination of these or other timer triggers. In some implementations, the base station <NUM>-a may transmit one or more DCI messages <NUM> to the UE <NUM>-a on a PDCCH. The one or more DCI messages <NUM> may schedule one or more future transmissions, such as a downlink data transmission <NUM>. Additionally, or alternatively, the one or more DCI messages <NUM> may schedule one or more future feedback TxOPs for the HARQ feedback <NUM>. The UE <NUM>-a may receive the downlink data transmission <NUM> and may perform a HARQ process to determine feedback information for the downlink data transmission <NUM>. The UE <NUM>-a may transmit an ACK as a confirmation of successful receipt of the data in the downlink data transmission <NUM> or the UE <NUM>-a may transmit a NACK if the UE <NUM>-a does not successfully receive and decode the data in downlink data transmission <NUM>.

In some implementations, prior to transmitting the HARQ feedback <NUM> (including one or more ACKs, NACKs, or both according to a HARQ codebook), the UE <NUM>-a may perform a channel access procedure, such as an LBT procedure or another channel access procedure, to gain access to the uplink channel <NUM>-b for the HARQ feedback <NUM> transmission. For example, if the uplink channel <NUM>-b is an unlicensed channel (for example, the uplink channel <NUM>-b supports one or more unlicensed radio frequency spectrum bands), the UE <NUM>-a may monitor the uplink channel <NUM>-b prior to transmitting on the uplink channel <NUM>-b. The UE <NUM>-a may transmit on the channel when the channel is not being utilized by another device. In some implementations, LBT failure may occur if the UE <NUM>-a determines that the channel remains busy during the HARQ feedback TxOP (for example, for at least a portion of the TxOP). The UE <NUM>-a may refrain from transmitting the HARQ feedback <NUM> in the HARQ feedback TxOP in some such implementations when LBT fails. In some implementations, the UE <NUM>-a may have a NACK to transmit when LBT failure occurs. For example, the UE <NUM>-a may fail to successfully decode the downlink data transmission <NUM> and also may fail to gain access to the uplink channel <NUM>-b to transmit the corresponding HARQ feedback <NUM>. If the UE <NUM>-a activates a timer based on transmitting a NACK in the HARQ feedback <NUM>, failing LBT may cause the timer to remain inactive when the timer otherwise would have activated at the successful transmission of the HARQ feedback <NUM>. The UE <NUM>-a may switch to an inactive mode due to the timer remaining inactive and may not transmit the NACK feedback to the base station <NUM> during the current ON duration for the UE <NUM>-a. As such, the UE <NUM>-a may not receive a retransmission of the downlink data transmission <NUM> missed by the UE <NUM>-a until a subsequent ON duration, introducing significant latency into the feedback and retransmission process.

To improve the likelihood that the UE <NUM>-a gains access to the uplink channel <NUM>-b to transmit the HARQ feedback <NUM>, the base station <NUM>-a may support multiple opportunities for HARQ ACK/NACK transmission, cross-channel occupancy time (COT) HARQ-ACK feedback, or both. Additionally, or alternatively, this may improve the likelihood that the base station <NUM>-a successfully receives the HARQ feedback <NUM> (for example, if reception at the base station <NUM>-a experiences potential interference). The base station <NUM>-a may request or trigger feedback for the downlink data transmission <NUM> (for example, a PDSCH message) from earlier COTs or additional reporting of earlier HARQ feedback <NUM>. The base station <NUM>-a may provide additional HARQ feedback timing and resources to the UE <NUM>-a in additional DCI messages <NUM> (such as in the same or a different COT as a first DCI message <NUM> scheduling a first feedback TxOP). Accordingly, the base station <NUM>-a may transmit more than one DCI message <NUM> indicating multiple HARQ feedback TxOPs for the same downlink data transmission <NUM>. The UE <NUM>-a may identify the more than one scheduled HARQ feedback TxOP supporting the UE <NUM>-a transmitting the HARQ feedback <NUM> for the downlink data transmission <NUM>. If the UE <NUM>-a fails to gain access to the uplink channel <NUM>-b in one HARQ feedback TxOP, the UE <NUM>-a may perform a successful LBT procedure in another HARQ feedback TxOP and transmit the HARQ feedback <NUM> to the base station <NUM>-a via the uplink channel <NUM>-b.

For a HARQ codebook, such as a dynamic HARQ codebook, the base station <NUM>-a may indicate PDSCH grouping using a group index in a DCI message <NUM> scheduling a PDSCH message (for example, a downlink data transmission <NUM>). The base station <NUM>-a may request HARQ feedback <NUM> in the same HARQ feedback message and TxOP for all PDSCH messages in the same group. For example, if the base station <NUM>-a schedules three downlink data transmissions <NUM> to the UE <NUM>-a and indicates that all three of the downlink data transmissions <NUM> belong to the same PDSCH group, the base station <NUM>-a may schedule a HARQ feedback opportunity for the entire PDSCH group. The UE <NUM>-a may transmit ACK/NACK information for all three of the downlink data transmissions <NUM> in a single HARQ feedback <NUM> in the HARQ feedback opportunity based on a dynamic HARQ codebook.

In some implementations, the base station <NUM>-a may request or trigger one-shot group HARQ feedback for multiple or all configured HARQ processes (such as for non-code block group (CBG) HARQ) at the UE <NUM>-a. For example, the base station <NUM>-a may include a request for the one-shot group HARQ feedback in a DCI message <NUM>. In some implementations, the request may be carried in a UE-specific DCI message carrying a physical uplink shared channel (PUSCH) grant, a UE-specific DCI message carrying a PDSCH assignment, a UE-specific DCI message not scheduling PDSCH nor PUSCH, a UE-common DCI, or some combination thereof. A UE <NUM> configured with a dynamic HARQ codebook, a semi-static HARQ codebook, or both may support the one-shot group HARQ feedback request.

To reduce the likelihood that a UE <NUM> becomes inactive without transmitting the HARQ feedback <NUM>, the UE <NUM> may implement one or more timers to handle missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. For example, the UE <NUM>-a may activate an RTT timer based on a scheduled HARQ feedback TxOP, regardless of whether the UE <NUM>-a actually transmits the HARQ feedback <NUM> in the TxOP. In this way, if the UE <NUM>-a fails an LBT procedure or otherwise does not transmit the HARQ feedback <NUM>, the UE <NUM>-a may remain awake based on activating the RTT timer (and a corresponding retransmission timer based on the RTT timer). By remaining awake, the UE <NUM>-a may identify one or more additional opportunities to transmit the HARQ feedback <NUM>. Additionally, or alternatively, the UE <NUM>-a may implement techniques for handling multiple HARQ feedback TxOPs for a single downlink data transmission <NUM>. In some implementations, the UE <NUM>-a may restart the RTT timer after each HARQ feedback TxOP (or after each HARQ feedback transmission) for the same HARQ process. In some other implementations, the UE <NUM>-a may start the RTT timer after the first HARQ feedback TxOP (or after the first HARQ feedback transmission) and may not restart the RTT timer after the subsequent TxOPs or transmissions for the same HARQ process.

<FIG> shows an example of a HARQ feedback procedure <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The HARQ feedback procedure <NUM> may include various timer durations, where some timers may keep a UE <NUM> in an active state of a DRX mode for a duration <NUM>. While in the active state, the UE <NUM> may receive a DCI message <NUM>, receive a downlink data message <NUM> (for example, via a PDSCH), and identify a HARQ feedback TxOP <NUM> for transmitting HARQ ACK/NACK feedback. In some implementations, a UE <NUM> as described with reference to <FIG> and <FIG> may implement a HARQ feedback procedure while operating in a DRX mode as described with reference to <FIG>. For example, a UE <NUM> may transmit HARQ feedback following the reception of a DCI message <NUM> and downlink data message <NUM>. Additionally, or alternatively, other wireless devices may implement a HARQ feedback procedure.

In some operations, such as DRX operations, a UE <NUM> may use timers (such as a drx-InactivityTimer, a drx-HARQ-RTT-TimerDL, a drx-RetransmissionTimerDL, or some combination of these or other timers) to maintain an active state. In an active state, the UE <NUM> may monitor the PDCCH. The UE <NUM> may activate a timer based on a particular event, and the timer may remain active for a configured duration. A duration <NUM> may be the active duration of an "ON" timer. The duration of the "ON" timer may be configured by a base station <NUM> if DRX is configured at the UE <NUM>. This timer may be responsible for the UE <NUM> switching to an active state, and the UE <NUM> may remain in the active state at least for the duration <NUM> regardless of the activation of other timers. A duration <NUM> may indicate the total active duration of the UE (for example, based on a set of timers). A duration <NUM> may be the active duration of a timer (such as a drx-InactivityTimer) and may start after a DCI message <NUM> schedules a new transmission. For example, the DCI message <NUM> may include a downlink grant scheduling a downlink data message <NUM>, and the UE <NUM> may activate the inactivity timer in a first symbol after the DCI message <NUM> is received or processed based on the downlink grant. During the duration <NUM>, the UE <NUM> may remain in the active state. The duration <NUM> may end after a pre-configured duration. The duration <NUM> and the duration <NUM> may overlap, such that the UE <NUM> remains active from the start of the ON duration timer to the end of the inactivity timer. In some implementations, the duration <NUM> may end before the duration <NUM>, and the UE <NUM> may remain active because the duration <NUM> has not ended. In this way, the inactivity timer may extend an ON period for the UE <NUM> such that the UE <NUM> remains awake to handle a scheduled transmission. In some other implementations, the duration <NUM> may end before the duration <NUM>, and the UE <NUM> may remain active because the duration <NUM> has not ended.

A duration <NUM> may be the active duration (for example, the runtime) of another timer (such as a drx-HARQ-RTT-TimerDL). The duration <NUM> may be defined per HARQ process and may start after a HARQ feedback TxOP <NUM>. For example, the DCI message <NUM> may include an indication <NUM> scheduling the HARQ feedback TxOP <NUM> for the UE <NUM> to provide feedback information for the scheduled downlink data message <NUM>. The duration <NUM> may be a preconfigured duration based on the RTT for a feedback transmission (such as a HARQ feedback transmission). The RTT may include the time for the transmission to reach a base station <NUM>, for the base station <NUM> to process the feedback, for the base station <NUM> to prepare a message in response, for the base station <NUM> to transmit the message in response, and for the response message to reach the UE <NUM> (for example, taking into account over-the-air (OTA) delays). In some implementations, the timer associated with duration <NUM> may not impact the DRX state of the UE <NUM>. For example, a running RTT timer may not keep the UE <NUM> in the active state. A duration <NUM> may be the active duration of another timer (such as a drx-RetransmissionTimerDL). During the duration <NUM>, the UE <NUM> may maintain the active state of the DRX mode. The duration <NUM> may allow a base station <NUM> to transmit a retransmission to the UE <NUM> and may allow the UE <NUM> to remain awake and monitor for the retransmission. The duration <NUM> may be defined per HARQ process and may begin after the expiry of the RTT timer associated with the duration <NUM> (such as the drx-HARQ-RTT-TimerDL) if the data of the corresponding HARQ process was not successfully decoded. For example, the UE <NUM> may not successfully decode data transmitted by a base station <NUM> and may prepare a NACK to send as feedback for the data to the base station <NUM>. The duration <NUM> may start after the duration <NUM> ends (for example, after an expiration of the RTT timer) if the UE <NUM> determines to transmit a NACK for the downlink data message <NUM> in the HARQ feedback TxOP <NUM> (whether or not the UE <NUM> actually transmits the NACK). If the UE <NUM> successfully decodes the downlink data message <NUM>, the UE <NUM> may not activate the retransmission timer corresponding to the duration <NUM>, as the UE <NUM> may not monitor for a retransmission of data already successfully received.

In unlicensed or licensed operations, a UE <NUM> may fail to transmit HARQ feedback in a scheduled HARQ feedback TxOP <NUM>. For example, if the feedback is scheduled for an unlicensed channel, the UE <NUM> may perform an LBT procedure to gain access to the unlicensed channel for the HARQ feedback TxOP <NUM>. If the LBT procedure fails, the UE <NUM> may not transmit the HARQ feedback message in the HARQ feedback TxOP <NUM> (for example, when operating according to an NR unlicensed operation). If the feedback is scheduled for a licensed channel, the UE <NUM> may drop the HARQ feedback transmission if another transmission preempts the HARQ feedback transmission. For example, a base station <NUM> may schedule a second transmission corresponding to a higher priority than the HARQ feedback transmission and overlapping at least partially in time with the HARQ feedback TxOP <NUM>, and the UE <NUM> may refrain from transmitting the HARQ feedback transmission in the HARQ feedback TxOP <NUM> based on the second transmission. In some implementations, a UE <NUM> supporting both enhanced mobile broadband (eMBB) and enhanced URLLC (eURLLC) traffic may drop eMBB HARQ ACK/NACK feedback when in conflict with an eURLLC transmission (for example, an eURLLC HARQ ACK/NACK feedback transmission). In some other examples, a UE <NUM> supporting downlink PDSCH reception from multiple TRPs may provide HARQ ACK/NACK feedback to each of the TRPs. The UE <NUM> may drop HARQ ACK/NACK to one TRP when in conflict with the transmission of HARQ ACK/NACK to another TRP. Additionally, or alternatively, the UE <NUM> may support multiple HARQ feedback TxOPs <NUM> in licensed operations due to the possibility of dropping HARQ feedback transmissions.

To account for a missed HARQ opportunity (for example, due to LBT failure, message preemption, potential interference at a base station <NUM>, etc.), the UE <NUM> may activate a timer based on the end of a HARQ feedback TxOP <NUM>. For example, the UE <NUM> may activate the RTT timer corresponding to the duration <NUM> in a first symbol after the HARQ feedback TxOP <NUM> whether or not the UE <NUM> transmits a feedback message in the HARQ feedback TxOP <NUM> (for example, based on the base station <NUM> scheduling and irrespective of an LBT outcome for the UE <NUM> in unlicensed operation). Such an implementation may extend the active time of the UE <NUM> regardless of an actual HARQ feedback transmission, allowing the UE <NUM> to continue monitoring the PDCCH. The UE <NUM> may start the RTT timer based on a scheduled physical uplink control channel (PUCCH) opportunity for HARQ feedback, a scheduled PUSCH opportunity for HARQ feedback, or both. For example, a UE <NUM> may start a drx-HARQ-RTT-TimerDL for the corresponding HARQ process in the first symbol after the end of the corresponding TxOP for the downlink HARQ feedback.

<FIG> shows an example of a HARQ feedback procedure <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The HARQ feedback procedure <NUM> may include various timer durations, where some timers may keep a UE <NUM> in an active state of a DRX mode for a duration <NUM>. While in the active state, the UE <NUM> may receive one or more DCI messages, receive a downlink data message <NUM> (for example, via a PDSCH), and identify one or more HARQ feedback TxOPs for transmitting HARQ ACK/NACK feedback. In some implementations, a UE <NUM> as described with reference to <FIG> and <FIG> may implement a HARQ feedback procedure <NUM> while operating in a DRX mode. For example, the UE <NUM> may transmit HARQ feedback following the reception of a DCI message and a downlink data message <NUM>. Additionally, or alternatively, other wireless devices may implement a HARQ feedback procedure.

As described herein, in some operations (such as DRX operations), a UE <NUM> may use timers (such as a drx-InactivityTimer, a drx-HARQ-RTT-TimerDL, a drx-RetransmissionTimerDL, or some combination of these or other timers) to maintain an active state. The durations <NUM>, <NUM>, <NUM>-a, <NUM>-a, <NUM>-b, and <NUM>-b may correspond to timer durations. Based on a set of timers, the UE <NUM> may remain active for a total duration <NUM>. A duration <NUM> may be the active duration of an "ON" timer. The "ON" timer may be responsible for the UE <NUM> switching to an active state, and the UE <NUM> may remain in the active state for at least the duration <NUM> regardless of the activation of other timers. A duration <NUM> may be the active duration of a timer (such as a drx-InactivityTimer) and may start after a DCI message <NUM>-a schedules a new transmission, such as the transmission of a downlink data message <NUM>. During the duration <NUM>, the UE <NUM> may remain in the active state (for example, continuing to monitor a downlink control channel).

A duration <NUM>-a may be the active duration of another timer (such as a drx-HARQ-RTT-TimerDL). The duration <NUM>-a may be defined per HARQ process and may start after a HARQ feedback TxOP <NUM>-a. For example, the DCI message <NUM>-a granting downlink resources for the downlink data message <NUM> also may include an indication <NUM>-a of scheduling information for a HARQ feedback TxOP <NUM>-a. The UE <NUM> may transmit feedback information (for example, a HARQ-ACK transmission) for the downlink data message <NUM> in the scheduled HARQ feedback TxOP <NUM>-a. The duration <NUM>-a may be a preconfigured duration based on the RTT for a transmission (such as a HARQ feedback transmission) to reach a base station <NUM>, for the base station <NUM> to transmit a message in response, and for the response transmission to reach the UE <NUM>. In some implementations, an RTT timer corresponding to the duration <NUM>-a may not maintain the active state of the UE <NUM>. A duration <NUM>-a may be the active duration of another timer (such as a drx-RetransmissionTimerDL) and may maintain the active state of the UE <NUM>. The duration <NUM>-a may keep the UE <NUM> awake and monitoring a downlink control channel, supporting reception of a retransmission from a base station <NUM>. A retransmission timer corresponding to the duration <NUM>-a may be defined per HARQ process and may begin after the expiry of an RTT timer associated with the duration <NUM>-a (such as a drx-HARQ-RTT-TimerDL) if the data of the corresponding HARQ process is not successfully decoded. In some implementations, a UE <NUM> may not successfully decode data from a base station <NUM> and the UE <NUM> may determine to transmit a NACK to the base station <NUM> for the data. The retransmission timer corresponding to the duration <NUM>-a may start after the duration <NUM>-a ends if the UE <NUM> determines a NACK for the downlink data message <NUM>.

To reduce the impact of LBT failure at a UE <NUM>, feedback reception failure at a base station <NUM>, or both on retransmission latency, a wireless communications system may support multiple HARQ TxOPs for a same downlink data message <NUM>. In some implementations, a UE <NUM> may start an RTT timer associated with the duration <NUM>-a (such as a drx-HARQ-RTT-TimerDL) after the first scheduled HARQ feedback TxOP <NUM>-a. After the RTT timer associated with the duration <NUM>-a expires, the UE <NUM> may start the retransmission timer associated with the duration <NUM>-a (such as a drx-RetransmissionTimerDL) if the downlink data message <NUM> of the corresponding HARQ process was not successfully decoded by the UE <NUM>. In some implementations, the base station <NUM> may schedule the UE <NUM> with another HARQ feedback TxOP <NUM>-b for the downlink data message <NUM>. In some implementations, the base station <NUM> may schedule the additional feedback opportunity based on the UE <NUM> failing to transmit HARQ feedback in the HARQ feedback TxOP <NUM>-a (for example, due to LBT failure) or the base station <NUM> failing to receive the HARQ feedback successfully (for example, due to interference). The base station <NUM> may schedule the additional HARQ feedback TxOP <NUM>-b using an indication <NUM>-b in an additional DCI message <NUM>-b. For example, the additional HARQ feedback triggering may be carried in a UE-specific DCI message carrying a PUSCH grant, a UE-specific DCI message carrying a PDSCH assignment, a UE-specific DCI message not scheduling a PDSCH or a PUSCH, a UE-common DCI message, or some combination thereof. As such, the UE <NUM> may receive more than one DCI message (such as DCI message <NUM>-a and DCI message <NUM>-b) indicating scheduled HARQ feedback opportunities for the same downlink data. For example, the DCI message <NUM>-b may indicate that the HARQ feedback TxOP <NUM>-b supports transmission of feedback information for the downlink data message <NUM>.

In some implementations, the UE <NUM> may start the RTT timer (such as a drx-HARQ-RTT-TimerDL) corresponding to the duration <NUM>-a based on the first scheduled HARQ feedback TxOP <NUM>-a for a HARQ process. For example, the UE <NUM> may activate the RTT timer based on the end of the HARQ feedback TxOP <NUM>-a or based on the end of a HARQ feedback transmission in the HARQ feedback TxOP <NUM>-a. In some implementations, the HARQ feedback TxOP <NUM>-b may be triggered by a UE-specific DCI message <NUM>-b carrying an additional PDSCH assignment. In some such implementations, the UE <NUM> may activate an additional RTT timer corresponding to the HARQ process for the additional PDSCH assignment, and the additional RTT timer (and a corresponding additional retransmission timer) may keep the UE <NUM> in the active state. In some other implementations, the HARQ feedback TxOP <NUM>-b may be triggered by a UE-specific DCI message <NUM>-b carrying a PUSCH grant, and the UE <NUM> may start uplink timers following the HARQ feedback TxOP <NUM>-b triggered by the DCI with the uplink grant (such as a drx-HARQ-RTT-TimerUL and a drx-RetransmissionTimerUL after expiration of the drx-HARQ-RTT-TimerUL). In some implementations, the uplink timers (such as the drx-HARQ-RTT-TimerUL, the drx-RetransmissionTimerUL, or both) may be configured differently than the downlink timers (such as the drx-HARQ-RTT-TimerDL, the drx-RetransmissionTimerDL, or both). In some implementations, the uplink timers may be shorter than the corresponding downlink timers, and the UE <NUM> may fail to be in an active state to monitor a potential PDCCH if an uplink RTT timer is activated based on the HARQ feedback TxOP <NUM>-b. In some such implementations, the UE <NUM> may activate a downlink RTT timer based on the HARQ feedback TxOP <NUM>-b to keep the UE <NUM> in the active state, even if the HARQ feedback TxOP <NUM>-b is scheduled in a DCI message <NUM>-b containing an uplink grant.

In some other implementations, the HARQ feedback TxOP <NUM>-b may be triggered by a UE-specific DCI message <NUM>-b that does not schedule PDSCH nor PUSCH, or the HARQ feedback TxOP <NUM>-b may be triggered by a UE-common DCI message <NUM>-b. In some such implementations, the DCI message <NUM>-b may not be associated with either an uplink grant or a downlink grant. In some implementations, the UE <NUM> may implement techniques to activate an RTT timer following the HARQ feedback TxOP <NUM>-b even if the DCI message <NUM>-b does not correspond to an uplink timer or a downlink timer, such that the UE <NUM> may remain in the active state following the HARQ feedback TxOP <NUM>-b.

In some implementations, the UE <NUM> may activate the downlink RTT timer corresponding to the duration <NUM>-a following the first HARQ feedback TxOP <NUM>-a and may not reactive the downlink RTT timer following additional HARQ feedback TxOPs (such as the HARQ feedback TxOP <NUM>-b) corresponding to the same HARQ process. In some other implementations, the UE <NUM> may start and restart the downlink RTT timer associated with the duration <NUM>-a and the duration <NUM>-b (such as a drx-HARQ-RTT-TimerDL) after each scheduled HARQ feedback TxOP for a HARQ process (for example, after the HARQ feedback TxOP <NUM>-a and after the HARQ feedback TxOP <NUM>-b). Based on reactivating the downlink RTT timer after the additional HARQ feedback TxOP <NUM>-b, the UE <NUM> may trigger reactivation of the corresponding retransmission timer corresponding to the duration <NUM>-b (for example, if the UE <NUM> determines a NACK for the corresponding downlink data message <NUM>), keeping the UE <NUM> active and monitoring the downlink control channel for an additional DCI message. In some such implementations, the UE <NUM> may activate and reactivate the RTT timer, the retransmission timer, or both after each scheduled HARQ feedback TxOP based on the end of the HARQ feedback TxOP or based on each actual HARQ feedback transmission in a HARQ feedback TxOP.

If the UE <NUM> is scheduled with multiple HARQ feedback TxOPs, the UE <NUM> may activate the RTT timer for a HARQ process when the retransmission timer for the same HARQ process is still running. For example, the duration <NUM>-a for the retransmission timer based on a first HARQ feedback TxOP <NUM>-a may still be active when the duration <NUM>-b for the RTT timer is activated based on the second HARQ feedback TxOP <NUM>-b. In some implementations, the UE <NUM> may keep the retransmission timer running when reactivating the RTT timer and may restart the retransmission timer when the reactivated RTT timer expires. Restarting the retransmission timer may involve resetting the retransmission timer to a maximum duration <NUM>-b for the retransmission timer upon the expiration of the reactivated RTT timer. In some other implementations, the UE <NUM> may stop the retransmission timer upon reactivating the RTT timer. In some such other implementations, the UE <NUM> may reactivate the retransmission timer with its full duration <NUM>-b upon expiry of the reactivated RTT timer. Based on stopping the retransmission timer, the UE <NUM> may not monitor for a retransmission or a DCI message scheduling a retransmission while the reactivated RTT timer is running.

<FIG> shows an example of a process flow <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The process flow <NUM> may illustrate an example HARQ process for DRX. For example, a UE <NUM>-b may perform a HARQ process for PDSCH data in order to transmit HARQ feedback to a base station <NUM>-b while operating timers in accordance with DRX operation. The base station <NUM>-b and the UE <NUM>-b may be examples of the corresponding wireless devices described with reference to <FIG>. Alternative examples of the following may be implemented, where some operations are performed in a different order than described or are not performed at all. In some implementations, operations may include additional features not mentioned below, or further operations may be added.

At <NUM>, the UE <NUM>-b may monitor a downlink control channel while operating in an active state of a DRX mode. The active state of the UE <NUM>-b may be turned on by a timer (such as an ON timer). At <NUM>, the base station <NUM>-b may transmit, to the UE <NUM>-b and via a downlink control channel (such as a PDCCH), a first DCI message scheduling a downlink data message and indicating a feedback TxOP for the downlink data message. The UE <NUM>-b may receive the downlink data message via a channel (such as a PDSCH). If the UE <NUM>-b correctly receives and decodes the downlink data message, the UE <NUM>-b may transmit an ACK during the feedback TxOP. If the UE <NUM>-b incorrectly receives or decodes the downlink data message, the UE <NUM>-b may transmit a NACK during the feedback TxOP. The feedback TxOP may be on an unlicensed channel. In some such implementations, the UE <NUM>-b may perform an LBT procedure for the feedback TxOP, where the UE <NUM>-b may refrain from transmitting a feedback message in the feedback TxOP based on the UE <NUM>-b failing the LBT procedure for the feedback TxOP. Additionally, or alternatively, the feedback TxOP may be on a licensed channel. In some such implementations, the UE <NUM>-b may refrain from transmitting the feedback message in the feedback TxOP based on another message with a higher priority preempting the feedback message transmission.

At <NUM>, the UE <NUM>-b may activate a first timer subsequent to the feedback TxOP for the downlink data message and based on the end of the feedback TxOP. The first timer may be an RTT timer (such as a DRX-HARQ-RTT-TimerDL) and may be activated in a first symbol in time after the feedback TxOP. The first timer may account for the amount of time for a HARQ feedback transmission to reach the base station <NUM>-b from the UE <NUM>-b, for the base station <NUM>-b to transmit a message in response, and for the response message to reach the UE <NUM>-b for reception. The first timer may not impact the activity of the UE <NUM>-b, such that the UE <NUM>-b may become inactive during the first timer's duration if all other DRX timers are inactive. At <NUM>, the UE <NUM>-b may activate a second timer upon expiration of the first timer, where the UE <NUM>-b may remain in the active state of the DRX mode while the second timer is running. The second timer may be a retransmission timer (such as a DRX-RetransmissionTimerDL) and may be activated in a first symbol in time after the expiration of the RTT timer.

At <NUM>, the base station <NUM>-b may determine an active time that the UE <NUM>-b is monitoring the downlink control channel based on an RTT timer and a retransmission timer, where the RTT timer may be activated based on the end of the feedback TxOP. In some implementations, the base station <NUM>-b may determine the active time for the UE <NUM>-b based on the RTT timer remaining deactivated subsequent to any additional, subsequent feedback TxOPs for the downlink data message. In some other implementations, the base station <NUM>-b may determine the active time for the UE <NUM>-b based on the RTT timer reactivating based on additional, subsequent feedback TxOPs for the downlink data message. At <NUM>, the base station <NUM>-b may transmit, to the UE <NUM>-b and via the downlink control channel, a second DCI message during the determined active time for the UE <NUM>-b.

At <NUM>, the UE <NUM>-b may reactivate the first timer (such as the RTT timer) corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on the end of the second feedback TxOP. Alternatively, the UE <NUM>-b may refrain from reactivating the first timer (such as the RTT timer) corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on the end of the second feedback TxOP being subsequent to the end of the first feedback TxOP.

<FIG> shows a block diagram <NUM> of an example device <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The device <NUM> may be an example of a UE <NUM>. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager <NUM>, an input/output (I/O) controller <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, a processor <NUM>, and a timer manager <NUM>. These components may be in electronic communication via one or more buses (such as a bus <NUM>).

The communications manager <NUM> may monitor a downlink control channel while operating in an active state of a DRX mode and may receive, via the downlink control channel, a DCI message scheduling a downlink data message, where the DCI message indicates a feedback TxOP for the downlink data message. The timer manager <NUM> may activate a first timer subsequent to the feedback TxOP for the downlink data message and based on the end of the feedback TxOP and may activate a second timer upon expiration of the first timer, where the device <NUM> (such as the UE <NUM>) remains in the active state of the DRX mode while the second timer is running.

In some implementations, the communications manager <NUM> may receive a first DCI message scheduling a downlink data message, where the first DCI message indicates a first feedback TxOP for a HARQ process for the downlink data message. The timer manager <NUM> may activate an RTT timer corresponding to the HARQ process subsequent to the first feedback TxOP for the downlink data message and based on the end of the first feedback TxOP. The communications manager <NUM> may additionally receive a second DCI message indicating a second feedback TxOP for the HARQ process for the downlink data message subsequent to the first feedback TxOP and the timer manager <NUM> may reactivate the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on the end of the second feedback TxOP.

In some other implementations, the communications manager <NUM> may receive a first DCI message scheduling a downlink data message, where the first DCI message indicates a first feedback TxOP for a HARQ process for the downlink data message. The timer manager <NUM> may activate an RTT timer corresponding to the HARQ process subsequent to the first feedback TxOP for the downlink data message and based on the end of the first feedback TxOP. The communications manager <NUM> may additionally receive a second DCI message indicating a second feedback TxOP for the HARQ process for the downlink data message subsequent to the first feedback TxOP and the timer manager <NUM> may refrain from reactivating the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on the end of the second feedback TxOP being subsequent to the end of the first feedback TxOP.

The I/O controller <NUM> also may manage peripherals not integrated into the device <NUM>. In some implementations, the I/O controller <NUM> may represent a physical connection or port to an external peripheral. In some implementations, the I/O controller <NUM> may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/<NUM>®, UNIX®, LINUX®, or another known operating system. In some other implementations, the I/O controller <NUM> may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some implementations, the I/O controller <NUM> may be implemented as part of a processor. In some implementations, a user may interact with the device <NUM> via the I/O controller <NUM> or via hardware components controlled by the I/O controller <NUM>.

The transceiver <NUM> also may include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. In some implementations, the communications manager <NUM> may be a component of or connected to the transceiver <NUM>.

In some implementations, the wireless device may include a single antenna <NUM>. However, in some other examples, the device may have more than one antenna <NUM>, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

In some implementations, the memory <NUM> may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor <NUM> may include an intelligent hardware device (for example, a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some implementations, the processor <NUM> may be configured to operate a memory array using a memory controller. In some other implementations, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (such as the memory <NUM>) to cause the device <NUM> to perform various functions (for example, functions or tasks supporting HARQ in a DRX mode).

In some implementations, the code <NUM> may not be directly executable by the processor <NUM> but may cause a computer (when compiled and executed) to perform functions described herein.

Additionally, or alternatively, the device <NUM> may include one or more interfaces and a processing system. The processing system may be in electronic communication with the one or more interfaces. In some implementations, the interfaces and processing system may be components of a chip or modem, which may be a component of the device <NUM>. The processing system and one or more interfaces may include aspects of the communications manager <NUM>, the timer manager <NUM>, the memory <NUM>, the processor <NUM>, or a combination thereof. The processing system and one or more interfaces also may be in electronic communication with the I/O controller <NUM>, the transceiver <NUM>, one or more antennas <NUM>, or a combination thereof (such as via the bus <NUM>).

For example, a first interface may be configured to obtain information from other components of the device <NUM>. A second interface may be configured to output information to other components of the device <NUM>. The information may be sent and received in the form of encoded or unencoded bits. The processing system may perform any number of processes to modify or determine the information output from the second interface.

Similarly, in some implementations, a first interface may be configured to output information to other components of the device <NUM>. A second interface may be configured to obtain information from other components of the device <NUM>. The information may be sent and received in the form of encoded or unencoded bits. The processing system may perform any number of processes to modify or determine the information output from the first interface.

The first interface may be configured to obtain monitoring information for a downlink control channel while operating in an active state of a DRX mode and obtain (for example, via the downlink control channel), a DCI message scheduling a downlink data message, where the DCI message indicates a feedback TxOP for the downlink data message. The processing system may be configured to activate a first timer subsequent to the feedback TxOP for the downlink data message and based on an end of the feedback TxOP and activate a second timer upon expiration of the first timer, where the processing system remains in the active state of the DRX mode while the second timer is running.

In some implementations, the first interface may be configured to obtain a first DCI message scheduling a downlink data message, where the first DCI message indicates a first feedback TxOP for a HARQ process for the downlink data message. The processing system may activate an RTT timer corresponding to the HARQ process subsequent to the first feedback TxOP for the downlink data message and based on an end of the first feedback TxOP. The first interface may be further configured to obtain a second DCI message indicating a second feedback TxOP for the HARQ process for the downlink data message subsequent to the first feedback TxOP, and the processing system may be further configured to reactivate the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on an end of the second feedback TxOP.

In some other implementations, the first interface may be configured to obtain a first DCI message scheduling a downlink data message, where the first DCI message indicates a first feedback TxOP for a HARQ process for the downlink data message. The processing system may be configured to activate an RTT timer corresponding to the HARQ process subsequent to the first feedback TxOP for the downlink data message and based on an end of the first feedback TxOP. The first interface may be further configured to obtain a second DCI message indicating a second feedback TxOP for the HARQ process for the downlink data message subsequent to the first feedback TxOP, and the processing system may be configured to refrain from reactivating the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on an end of the second feedback TxOP being subsequent to the end of the first feedback TxOP.

<FIG> shows a block diagram <NUM> of an example device <NUM> that supports handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The device <NUM> may be an example of a base station <NUM>. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager <NUM>, a network communications manager <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, a processor <NUM>, and an inter-station communications manager <NUM>. These components may be in electronic communication via one or more buses (such as a bus <NUM>).

The communications manager <NUM> may transmit, to a UE and via a downlink control channel, a first DCI message scheduling a downlink data message and indicating a feedback TxOP for the downlink data message. The communications manager <NUM> may further determine an active time for the UE to monitor the downlink control channel based on an RTT timer and a retransmission timer, where the RTT timer is activated based on an end of the feedback TxOP. For example, the RTT timer may be activated subsequent to the feedback TxOP for the downlink data message and based on the end of the feedback TxOP, and the retransmission timer may be activated based on an expiration of the RTT timer. The UE may actively monitor the downlink control channel while the retransmission timer is running. The communications manager <NUM> may transmit, to the UE and via the downlink control channel, a second DCI message during the determined active time for the UE.

The network communications manager <NUM> may manage communications with the core network <NUM> (for example, via one or more wired backhaul links).

The memory <NUM> may store computer-readable code <NUM> including instructions that, when executed by a processor (such as the processor <NUM>) cause the device to perform various functions described herein. In some implementations, the memory <NUM> may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor <NUM> may include an intelligent hardware device (for example, 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 implementations, the processor <NUM> may be configured to operate a memory array using a memory controller. In some implementations, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (for example, the memory <NUM>) to cause the device <NUM> to perform various functions (such as functions or tasks supporting HARQ handling for DRX).

The inter-station communications manager <NUM> may manage communications with other base station <NUM> and may include a controller or scheduler for controlling communications with UEs <NUM> in cooperation with other base stations <NUM>. In some implementations, the inter-station communications manager <NUM> may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations <NUM>.

Additionally, or alternatively, the device <NUM> may include one or more interfaces and a processing system. The processing system may be in electronic communication with the one or more interfaces. In some implementations, the interfaces and processing system may be components of a chip or modem, which may be a component of the device <NUM>. The processing system and one or more interfaces may include aspects of the communications manager <NUM>, the memory <NUM>, the processor <NUM>, or a combination thereof. The processing system and one or more interfaces also may be in electronic communication with the network communications manager <NUM>, the inter-station communications manager <NUM>, the transceiver <NUM>, one or more antennas <NUM>, or a combination thereof (such as via the bus <NUM>).

For example, a first interface may be configured to output information to other components of the device <NUM>. A second interface may be configured to obtain information from other components of the device <NUM>. The information may be sent and received in the form of encoded or unencoded bits. The processing system may perform any number of processes to modify or determine the information output from the first interface.

Similarly, in some implementations, a first interface may be configured to obtain information from other components of the device <NUM>. A second interface may be configured to output information to other components of the device <NUM>. The information may be sent and received in the form of encoded or unencoded bits. The processing system may perform any number of processes to modify or determine the information output from the second interface.

In some implementations, the first interface may be configured to output (such as to a UE and via a downlink control channel based on the transceiver <NUM>) a first DCI message scheduling a downlink data message and indicating a feedback TxOP for the downlink data message. The processing system may be configured to determine an active time for the UE to monitor the downlink control channel based on an RTT timer and a retransmission timer, where the RTT timer is activated based on an end of the feedback TxOP. The first interface may be further configured to output (such as to the UE and via the downlink control channel) a second DCI message during the determined active time for the UE.

<FIG> shows a flowchart illustrating an example method <NUM> for handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The operations of the method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of the method <NUM> may be performed by a communications manager, a timer manager, or both as described with reference to <FIG>. In some implementations, a UE <NUM> may execute a set of instructions to control the functional elements of the UE <NUM> to perform the functions described below. Additionally, or alternatively, a UE <NUM> may perform aspects of the functions described below using special-purpose hardware.

At <NUM>, the UE <NUM> may monitor a downlink control channel while operating in an active state of a DRX mode. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may receive, via the downlink control channel, a DCI message scheduling a downlink data message, where the DCI message indicates a feedback TxOP for the downlink data message. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may activate a first timer subsequent to the feedback TxOP for the downlink data message and based on an end of the feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may activate a second timer upon expiration of the first timer, where the UE <NUM> remains in the active state of the DRX mode while the second timer is running. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may fail to successfully decode the downlink data message. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may determine feedback information for the downlink data message, where the feedback information includes a NACK for the downlink data message based on the UE <NUM> failing to successfully decode the downlink data message, and where a first timer, a second timer, or both are activated based on the feedback information including the NACK. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may activate the first timer subsequent to the feedback TxOP for the downlink data message and based on an end of the feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may activate the second timer upon expiration of the first timer, where the UE <NUM> remains in the active state of the DRX mode while the second timer is running. The operations of <NUM> may be performed according to the methods described herein.

<FIG> shows a flowchart illustrating an example method <NUM> for handling missed HARQ opportunities, multiple HARQ opportunities, or both for DRX. The operations of the method <NUM> may be implemented by a base station <NUM> or its components as described herein. For example, the operations of the method <NUM> may be performed by a communications manager as described with reference to <FIG>. In some implementations, a base station <NUM> may execute a set of instructions to control the functional elements of the base station <NUM> to perform the functions described below. Additionally, or alternatively, a base station <NUM> may perform aspects of the functions described below using special-purpose hardware.

At <NUM>, the base station <NUM> may transmit, to a UE <NUM> and via a downlink control channel, a first DCI message scheduling a downlink data message and indicating a feedback TxOP for the downlink data message. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the base station <NUM> may determine an active time for the UE <NUM> to monitor the downlink control channel based on an RTT timer and a retransmission timer, where the RTT timer is activated based on an end of the feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the base station <NUM> may transmit, to the UE <NUM> and via the downlink control channel, a second DCI message during the determined active time for the UE <NUM>. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may receive a first DCI message scheduling a downlink data message, where the first DCI message indicates a first feedback TxOP for a HARQ process for the downlink data message. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may activate an RTT timer corresponding to the HARQ process subsequent to the first feedback TxOP for the downlink data message and based on an end of the first feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may receive a second DCI message indicating a second feedback TxOP for the HARQ process for the downlink data message subsequent to the first feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may reactivate the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on an end of the second feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

At <NUM>, the UE <NUM> may refrain from reactivating the RTT timer corresponding to the HARQ process subsequent to the second feedback TxOP for the downlink data message and based on an end of the second feedback TxOP being subsequent to the end of the first feedback TxOP. The operations of <NUM> may be performed according to the methods described herein.

The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a DSP, an ASIC, 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, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a set of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes and methods may be performed by circuitry that is specific to a given function.

Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination.

Claim 1:
An apparatus for wireless communications, comprising:
a first interface configured to:
obtain (<NUM>) monitoring information for a downlink control channel while operating in an active state of a discontinuous reception, DRX, mode; and the apparatus is characterised in that the first interface configured to:
obtain (<NUM>) a downlink control information, DCI, message scheduling a downlink data message based at least in part on the monitoring information, wherein the DCI message indicates a feedback transmission opportunity, TxOP, for the downlink data message; and
a processing system configured to:
activate (<NUM>) a first timer subsequent to the feedback TxOP for the downlink data message and based at least in part on an end of the feedback TxOP; and
activate (<NUM>) a second timer upon expiration of the first timer, wherein the processing system remains in the active state of the DRX mode while the second timer is running.