Patent Description:
The present disclosure relates generally to wireless communication systems, and more particularly, to techniques and apparatus for enhancing uplink grant-free transmissions and/or downlink semi-persistent scheduling (SPS) transmissions, e.g., for ultra-reliable low latency communications (URLLC).

Examples of such multiple-access technologies include Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In LTE or LTE-A network, a set of one or more base stations may define an evolved Node B (eNB). In other examples (e.g., in a next generation or <NUM> network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more distributed units, in communication with a central unit, may define an access node (e.g., a new radio base station (NR BS), a new radio BS (NR NB), a network node, <NUM> NB, eNB, a Next Generation NB (gNB), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

An example of the background art is provided in <CIT>, disclosing a UE receiving, for transmission resources allocated by Semi-Persistent Scheduling (SPS), a set of modulation and coding schemes (MCSs) from a base station, and then determining an MCS from the set. The MCS for a next SPS allocation may be changed e.g. if several HARQ retransmissions are needed to convey the data.

Certain aspects provide a method for wireless communication by a user equipment (UE). The method generally includes receiving a first configuration for a first grant-free communication. The method also includes receiving a second configuration for at least one second grant-free communication. The method further includes performing grant-free communications with a base station (BS) based on the first configuration and the second configuration respectively.

Certain aspects provide an apparatus for wireless communication. The apparatus includes means for receiving a first configuration for a first grant-free communication. The apparatus also includes means for receiving a second configuration for at least one second grant-free communication. The apparatus further includes means for performing grant-free communications with a base station (BS) based on the first configuration and the second configuration respectively.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a receiver, at least one processor, and a memory coupled to the at least one processor. The receiver is configured to receive a first configuration for a first grant-free communication. The receiver is also configured to receive a second configuration for at least one second grant-free communication. The at least one processor is configured to perform grant-free communications with a base station (BS) based on the first configuration and the second configuration respectively.

Certain aspects provide a method for wireless communication by a base station (BS). The method generally includes determining a first configuration for a first grant-free communication. The method also includes determining a second configuration for at least one second grant-free communication. The method further includes sending the first configuration and the second configuration to at least one user equipment (UE).

Certain aspects provide an apparatus for wireless communication. The apparatus includes means for determining a first configuration for a first grant-free communication. The apparatus also includes means for determining a second configuration for at least one second grant-free communication. The apparatus further includes means for sending the first configuration and the second configuration to at least one user equipment (UE).

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a transmitter, at least one processor, and a memory coupled to the at least one processor. The at least one processor is configured to determine a first configuration for a first grant-free communication. The at least one processor is also configured to determine a second configuration for at least one second grant-free communication. The transmitter is configured to send the first configuration and the second configuration to at least one user equipment (UE).

Any embodiments/examples/ aspects in which the second configuration is used for purposes other than retransmission do not fall within the scope of the claims.

NR access (e.g., <NUM> technology) may support various wireless communication services, such as Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. <NUM> beyond), millimeter wave (mmW) targeting high carrier frequency (e.g. <NUM> or beyond), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low latency communications (URLLC).

NR introduces the concept of network slicing. For example, a network may have multiple slices, which may support different services, for example, internet of everything (IoE), URLLC, eMBB, vehicle-to-vehicle (V2V) communications, etc. A slice may be defined as a complete logical network that comprises of a set of network functions and corresponding resources necessary to provide certain network capabilities and network characteristics.

One focus of the development of <NUM> NR systems has been on supporting URLLC. URLLC applications may have mission critical traffic and, in general, may be associated with strict latency-reliability requirements. Using factory automation deployments as a reference example, there may be two types of URLLC applications: (<NUM>) Type <NUM> URLLC applications and (<NUM>) Type <NUM> URLLC applications. Type <NUM> URLLC applications may have a latency requirement of less than <NUM> milliseconds (ms) and a target reliability of <NUM>-<NUM>-<NUM>. Type <NUM> URLLC applications may have a latency requirement between <NUM> to <NUM> and a target reliability between <NUM>-<NUM>-<NUM> to <NUM>-<NUM>-<NUM>.

In some cases, <NUM> systems may support semi-persistent scheduling (SPS) and/or grant-free transmissions to reduce latency and/or meet target reliability of applications. However, current designs for SPS/grant-free transmissions may not be sufficient for meeting the latency and/or target reliability of URLLC applications. For example, current designs generally support SPS/grant-free transmission on the initial (e.g., first) transmission, but may not support SPS/grant-free transmission on subsequent (e.g., second, third, etc.) re-transmission(s). In these cases, the subsequent retransmission(s) may be associated with additional control signaling (e.g., physical downlink control channel (PDCCH)). Using additional control signaling, however, can increase overhead (e.g., reducing amount of resources for URLLC data), increase latency (e.g., additional time associated with decoding grant for URLLC data), degrade reliability (e.g., increases likelihood of a decoding failure of the grant), etc., for URLLC applications.

Accordingly, aspects of the present disclosure provide enhanced techniques for SPS and/or grant-free transmissions that can be used to meet latency and/or reliability requirements for particular applications, e.g., URLLC applications.

In some aspects, a UE may receive, from a gNB, multiple configurations for at least one grant-free communication. Each configuration may be associated with a different latency condition (or threshold) for the grant-free communication, a different modulation and coding scheme (MCS) for the grant-free communication, a different service type for the grant-free communication, etc. In some aspects, the UE may receive multiple configurations for a single (e.g., initial) grant-free communication. The UE may select one of the multiple configurations for the single grant-free communication based at least in part on one or more criteria, and perform the grant-free communication based on the selected configuration. The criteria may include, for example, a target MCS, a service type, a target latency, etc. Grant-free communications may include at least one of downlink SPS transmissions (e.g., from the gNB to the UE) or uplink grant-free transmissions (e.g., from the UE to the gNB).

In some aspects, the UE may receive multiple configurations for multiple grant-free communications. For example, a UE may receive a first configuration for a first (e.g., initial) grant-free communication and a second configuration for one or more second (e.g., subsequent) grant-free communications. The UE may perform grant-free communications with the gNB based on at least one of the first configuration or the second configuration. For example, the UE may receive an initial downlink SPS transmission(s) (e.g., based on the first configuration) and one or more subsequent downlink SPS transmissions (e.g., based on the second configuration). In another example, the UE may send an initial uplink grant-free transmission(s) (e.g., based on the first configuration) and one or more subsequent uplink grant-free transmissions (e.g., based on the second configuration). In this manner, <NUM> systems can reduce control signaling associated with (re)transmissions of SPS/grant-free transmissions, which in turn, can achieve better system utilization, enhanced reliability and lower latency (typically associated with URLLC applications).

Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.

The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies, such as a <NUM> nextgen/NR network.

<FIG> illustrates an example wireless communication network <NUM>, such as a new radio (NR) or <NUM> network, in which aspects of the present disclosure may be performed, for example, for configuring (and/or sending) transmissions and/or retransmission(s) of downlink SPS/uplink grant-free traffic for URLLC. In some cases, the network <NUM> may be a multi-slice network, where each slice defines as a composition of adequately configured network functions, network applications, and underlying cloud infrastructures that are bundled together to meet the requirement of a specific use case or business model.

As illustrated in <FIG>, the wireless communication network <NUM> may include a number of base stations (BSs) <NUM> and other network entities. A BS may be a station that communicates with UEs. Each BS <NUM> may provide communication coverage for a particular geographic area. In NR systems, the term "cell" and evolved NB (eNB), NB, <NUM> NB, Next Generation NB (gNB), access point (AP), BS, NR BS, <NUM> BS, or transmission reception point (TRP) may be interchangeable. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless communication network <NUM> through various types of backhaul interfaces such as a direct physical connection, a virtual network, or the like using any suitable transport network.

A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.

A network controller <NUM> may be coupled to a set of BSs and provide coordination and control for these BSs.

A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered evolved or machine-type communication (MTC) devices or evolved MTC (eMTC) devices. Some UEs may be considered Internet-of Things (IoT) or narrowband IoT (NB-IoT) devices.

OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, subbands, etc. Each subcarrier may be modulated with data. Consequently, the nominal FFT size may be equal to <NUM>, <NUM>, <NUM>, <NUM> or <NUM> for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM> megahertz (MHz), respectively. For example, a subband may cover <NUM> (i.e., <NUM> RBs), and there may be <NUM>, <NUM>, <NUM>, <NUM> or <NUM> subbands for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, respectively.

NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using time division duplex (TDD). Alternatively, NR may support a different air interface, other than an OFDM-based. NR networks may include entities such CUs and/or DUs.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. BSs are not the only entities that may function as a scheduling entity. In a mesh network example, UEs may communicate directly with one another in addition to communicating with the scheduling entity.

<FIG> illustrates an example architecture of a distributed radio access network (RAN) <NUM>, which may be implemented in the wireless communication network <NUM> illustrated in <FIG>. As shown in <FIG>, the distributed RAN includes Core Network (CN) <NUM> and Access Node <NUM>.

The CN <NUM> may host core network functions. CN <NUM> may be centrally deployed. CN <NUM> functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity. The CN <NUM> may include the Access and Mobility Management Function (AMF) <NUM> and User Plane Function (UPF) <NUM>. The AMF <NUM> and UPF <NUM> may perform one or more of the core network functions.

The AN <NUM> may communicate with the CN <NUM> (e.g., via a backhaul interface). The AN <NUM> may communicate with the AMF <NUM> via an N2 (e.g., NG-C) interface. The AN <NUM> may communicate with the UPF <NUM> via an N3 (e.g., NG-U) interface. The AN <NUM> may include a central unit-control plane (CU-CP) <NUM>, one or more central unit-user plane (CU-UPs) <NUM>, one or more distributed units (DUs) <NUM>-<NUM>, and one or more Antenna/Remote Radio Units (AU/RRUs) <NUM>-<NUM>. The CUs and DUs may also be referred to as gNB-CU and gNB-DU, respectively. One or more components of the AN <NUM> may be implemented in a gNB <NUM>. The AN <NUM> may communicate with one or more neighboring gNBs.

The CU-CP <NUM> may be connected to one or more of the DUs <NUM>-<NUM>. The CU-CP <NUM> and DUs <NUM>-<NUM> may be connected via a F1-C interface. As shown in <FIG>, the CU-CP <NUM> may be connected to multiple DUs, but the DUs may be connected to only one CU-CP. Although <FIG> only illustrates one CU-UP <NUM>, the AN <NUM> may include multiple CU-UPs. The CU-CP <NUM> selects the appropriate CU-UP(s) for requested services (e.g., for a UE).

The CU-UP(s) <NUM> may be connected to the CU-CP <NUM>. For example, the DU-UP(s) <NUM> and the CU-CP <NUM> may be connected via an E1 interface. The CU-CP(s) <NUM> may connected to one or more of the DUs <NUM>-<NUM>. The CU-UP(s) <NUM> and DUs <NUM>-<NUM> may be connected via a F1-U interface. As shown in <FIG>, the CU-CP <NUM> may be connected to multiple CU-UPs, but the CU-UPs may be connected to only one CU-CP.

A DU, such as DUs <NUM>, <NUM>, and/or <NUM>, may host one or more TRP(s) (transmit/receive points, which may include an Edge Node (EN), an Edge Unit (EU), a Radio Head (RH), a Smart Radio Head (SRH), or the like). A DU may be located at edges of the network with radio frequency (RF) functionality. A DU may be connected to multiple CU-UPs that are connected to (e.g., under the control of) the same CU-CP (e.g., for RAN sharing, radio as a service (RaaS), and service specific deployments). DUs may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE. Each DU <NUM>-<NUM> may be connected with one of AU/RRUs <NUM>-<NUM>. The DU may be connected to an AU/RRU via each of the F1-C and F1-U interfaces.

The CU-CP <NUM> may be connected to multiple DU(s) that are connected to (e.g., under control of) the same CU-UP <NUM>. Connectivity between a CU-UP <NUM> and a DU may be established by the CU-CP <NUM>. For example, the connectivity between the CU-UP <NUM> and a DU may be established using Bearer Context Management functions. Data forwarding between CU-UP(s) <NUM> may be via a Xn-U interface.

The distributed RAN <NUM> may support fronthauling solutions across different deployment types. For example, the RAN <NUM> architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter). The distributed RAN <NUM> may share features and/or components with LTE. For example, AN <NUM> may support dual connectivity with NR and may share a common fronthaul for LTE and NR. The distributed RAN <NUM> may enable cooperation between and among DUs <NUM>-<NUM>, for example, via the CU-CP <NUM>. An inter-DU interface may not be used.

Logical functions may be dynamically distributed in the distributed RAN <NUM>. As will be described in more detail with reference to <FIG>, the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, Physical (PHY) layers, and/or Radio Frequency (RF) layers may be adaptably placed, in the N AN and/or UE.

<FIG> illustrates a diagram showing examples for implementing a communications protocol stack <NUM> in a RAN (e.g., such as the RAN <NUM>), according to aspects of the present disclosure. The illustrated communications protocol stack <NUM> may be implemented by devices operating in a wireless communication system, such as a <NUM> NR system (e.g., the wireless communication network <NUM>). In various examples, the layers of the protocol stack <NUM> may be implemented as separate modules of software, portions of a processor or ASIC, portions of non-collocated devices connected by a communications link, or various combinations thereof. Collocated and non-collocated implementations may be used, for example, in a protocol stack for a network access device or a UE. As shown in <FIG>, the system may support various services over one or more protocols. One or more protocol layers of the protocol stack <NUM> may be implemented by the AN and/or the UE.

As shown in <FIG>, the protocol stack <NUM> is split in the AN (e.g., AN <NUM> in <FIG>). The RRC layer <NUM>, PDCP layer <NUM>, RLC layer <NUM>, MAC layer <NUM>, PHY layer <NUM>, and RF layer <NUM> may be implemented by the AN. For example, the CU-CP (e.g., CU-CP <NUM> in <FIG>) and the CU-UP e.g., CU-UP <NUM> in <FIG>) each may implement the RRC layer <NUM> and the PDCP layer <NUM>. A DU (e.g., DUs <NUM>-<NUM> in <FIG>) may implement the RLC layer <NUM> and MAC layer <NUM>. The AU/RRU (e.g., AU/RRUs <NUM>-<NUM> in <FIG>) may implement the PHY layer(s) <NUM> and the RF layer(s) <NUM>. The PHY layers <NUM> may include a high PHY layer and a low PHY layer.

The UE may implement the entire protocol stack <NUM> (e.g., the RRC layer <NUM>, the PDCP layer <NUM>, the RLC layer <NUM>, the MAC layer <NUM>, the PHY layer(s) <NUM>, and the RF layer(s) <NUM>).

<FIG> illustrates example components of the BS <NUM> and UE <NUM> (as depicted in <FIG>, which may be used to implement aspects of the present disclosure. As described above, the BS may include a TRP. One or more components of the BS <NUM> and UE <NUM> may be used to practice aspects of the present disclosure. For example, antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM> and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> may be used to perform the operations described herein and illustrated with reference to <FIG>.

The controllers/processors <NUM> and <NUM> may direct the operation at the BS <NUM> and the UE <NUM>, respectively. The processor <NUM> and/or other processors and modules at the BS <NUM> may perform or direct, e.g., the execution of the functional blocks illustrated in <FIG> and/or other processes for the techniques described herein. The processor <NUM> and/or other processors and modules at the UE <NUM> may also perform or direct, e.g., the execution of the functional blocks illustrated in <FIG> and/or other processes for the techniques described herein. The memories <NUM> and <NUM> may store data and program codes for the BS <NUM> and the UE <NUM>, respectively.

<FIG> illustrates an example system architecture <NUM> for interworking between 5GS (e.g., such as the distributed RAN <NUM>) and E-UTRAN-EPC, in accordance with certain aspects of the present disclosure. As shown in <FIG>, the UE <NUM> may be served by separate RANs 504A and 504B controlled by separate core networks 506A and 506B, where the RAN 504A provides E-UTRA services and RAN 504B provides <NUM> NR services. The UE may operate under only one RAN/CN or both RANs/CNs at a time.

As noted, URLLC applications may have latency-reliability standards that are stricter compared to other types of traffic. As an example, in some URLLC (e.g., Type <NUM>) applications, latency may not exceed <NUM> and the target reliability may be <NUM>-<NUM>-<NUM>. In other URLLC (e.g., Type <NUM>) applications, latency may be in the range of <NUM> to <NUM> and the target reliability may be in between <NUM>-<NUM>-<NUM> to <NUM>-<NUM>-<NUM>. To meet such standards, the individual channels including UL/DL control channels may also have similar target reliability.

In some cases, reducing latency and/or increasing reliability can be achieved by minimizing dynamic control signaling (e.g., using semi-static allocation patterns). For example, certain systems (e.g., LTE, NR, etc.) may support grant-free transmissions and/or SPS scheduling. In LTE, SPS was introduced to support applications with (semi) periodic traffic by eliminating (or reducing) PDCCH overhead where data inter-arrival times are constant. When a UE is configured with SPS, certain parameters, such as the number of HARQ processes, periodicity, etc., can be indicated via RRC. The UE can then be explicitly activated to use such parameters (e.g., via PDCCH) for multiple additional SPS transmissions (e.g., without monitoring/decoding additional PDCCH). The PDCCH that activates the SPS transmissions may have a cyclic redundancy check (CRC) scrambled by a SPS radio network temporary identifier (RNTI) configured for the UE.

NR may also support semi-static allocation patterns. For example, NR may support uplink grant-free transmissions and/or downlink SPS transmissions. As used herein, grant-free transmission generally refers to data transmission with grant-free resource(s) (e.g., no resources dedicated/allocated in an uplink grant). There may be two types of UL data transmission without a grant: Type <NUM> and Type <NUM>. For Type <NUM>, the UL data transmission without grant may be only based on RRC (re)configuration without any L1 signaling. That is, parameters for the UL data transmission such as MCS/TBS table, time/frequency resources, etc. may be UE specific and RRC configured. For Type <NUM>, the UL data transmission without grant may be based on both RRC configuration and L1 signaling for activation/deactivation for UL data transmission without grant. UL grant-free Type <NUM>, thus, may be similar to SPS where dynamic signaling (DCI) is used for activation/deactivation of RRC configured resources.

Additionally, in some cases, grant-free/SPS designs may use transport block (TB) repetitions (with the same or different redundancy version (RV) index) to increase reliability. That is, the initial grant-free/SPS transmission can have a number of repetitions (e.g., up to <NUM> retransmissions), and each repetition can have its own RV index. Using UL grant-free transmission as a reference example, each HARQ identifier (ID) can have up to K repetitions, where K E {<NUM>, <NUM>, <NUM>, <NUM>}. The HARQ ID associated with the K repetitions of a TB may be determined from the following equation (<NUM>): <MAT> where X refers to the symbol index of the first transmission occasion of the repetition bundle that takes place. For example, X = (SFN * SlotPerFrame * SymbolPerSlot + Slot_index_in_SF * SymbolPerSlot + Symbol_Index_In-Slot). UL-TWG-periodicity represents the periodicity of UL grant-free, and UL-TWG-numbHARQproc represents the number of HARQs supported in UL grant-free. The n-th transmission occasion of K repetitions may be associated with the (mod(n-<NUM>,<NUM>)+<NUM>)-th value in the configured RV sequence {RV1, RV2, RV3, RV4}, where n=<NUM>,<NUM>,.

RV sequences may be configured by UE-specific RRC signaling to be one of the following: Sequence <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>}, Sequence <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>}, Sequence <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>}. For any RV sequence, repetition may end at the last transmission occasion within the period P. P is not more than GF/SPS periodicity. The transmission occasion (TO) may refer to the time domain resource allocation of one repetition in an aggregation with factor K, where the aggregated transmission occasions start in resources configured by the offset and the period. In NR, retransmissions (except for repetition(s)) of GP/SPS may use dynamic grant.

In some situations, the current design for grant-free/SPS communications may not be sufficient for meeting the latency/reliability standards associated with URLLC applications. In the current design, for example, the UE may be configured with a single (active) configuration for a grant-free communication. In many cases, however, this single configuration (including the configured parameters, such as number of repetitions, frequency resources, transmit power, etc.) may not be suitable for meeting one or more predetermined conditions (e.g., based on a MCS, service type, and/or latency).

Additionally, while grant-free transmissions may be associated with a predefined number of (K) repetitions, such a design may have some drawbacks. There may be cases (e.g., when channel conditions are above a threshold) in which a given UE may not have to always go through all K number of repetitions. If the TB is successfully decoded at one or more first repetitions, the rest of the repetitions aggregated with K may cause unnecessary interference to other UEs that share the same resource(s), which in turn can reduce system utilization and degrade reliability.

In some cases, a transmitter with GF/SPS resource(s) may stop TB repetition in case of early ACK reception, but such ACK signaling may also have some drawbacks. For example, ACK signaling to end the repetitions may increase control overhead, which in turn can degrade system efficiency (e.g., in cases with (semi) periodic traffic with small data packets). ACK signaling may also impact the control channel design, which may have its own reliability issues/considerations. Additionally, in some cases, ACK signaling may not always be possible (e.g., in unlicensed band(s), the UE may not be clear to transmit) and/or the UE may have to wait a significant amount of time before sending such signaling (e.g., in unlicensed band(s), ACK signaling may need clear channel assessment (CCA) to obtain the channel, increasing latency). In addition, the ACK signaling, itself, may bring additional latency in TDD for a given slot format related information (SFI).

Further, in some cases, using PDCCH for retransmission (as in current grant-free/SPS designs) can significantly increase the amount of time-frequency resources used for grant-free/SPS. Accordingly, it may be desirable to remove the overhead associated with PDCCH and additional control signaling for URLLC.

According to certain aspects, techniques presented herein enable devices (e.g., in <NUM> systems) to send grant-free/SPS not only for the initial transmission, but also for the re-transmission(s) (e.g., assuming re-transmission(s) are needed). Doing so may reduce control overhead (e.g., permitting retransmission for more devices), reduce latency, improve reliability, etc..

<FIG> illustrates example operations <NUM> for wireless communications, in accordance with aspects of the present disclosure. Operations <NUM> may be performed, for example, by a user equipment (e.g., URLLC UE), such as UE <NUM> shown in <FIG>. Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., processor <NUM>) obtaining and/or outputting signals.

Operations <NUM> begin, at <NUM>, where the UE receives a first configuration for a first grant-free communication. At <NUM>, the UE receives a second configuration for at least one second grant-free communication. At <NUM>, the UE performs grant-free communications based on at least one of the first configuration or the second configuration.

<FIG> illustrates example operations <NUM> for wireless communications, in accordance with aspects of the present disclosure. Operations <NUM> may be performed, for example, by a base station that supports URLLC (e.g., a gNB), such as BS <NUM> shown in <FIG>. Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., processor <NUM> of <FIG>). Further, the transmission and reception of signals by the BS in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the BS may be implemented via a bus interface of one or more processors (e.g., processor <NUM>) obtaining and/or outputting signals.

Operations <NUM> begin, at <NUM>, where the base station determines a first configuration for a first grant-free communication. At <NUM>, the base station determines a second configuration for at least one second grant-free communication. At <NUM>, the base station sends the first configuration and the second configuration to at least one UE.

As used herein, grant-free communication may refer to at least one of uplink grant-free transmission or downlink SPS transmission. For example, the UE may receive initial downlink SPS transmissions (e.g., based on the first configuration) and one or more subsequent downlink SPS transmissions (e.g., based on the second configuration) from the gNB. In another example, the UE may send initial uplink grant-free transmissions (e.g., based on the first configuration) and one or more subsequent uplink grant-free transmissions (e.g., based on the second configuration) to the gNB.

In some aspects, a URLLC UE can be configured with grant-free/SPS resources for the initial transmission and also one or more retransmissions. In some cases, the UE can be configured with different grant-free/SPS configurations. For example, the first configuration (e.g., in operations <NUM>, <NUM>) may be for an initial TB transmission and the second configuration (e.g., in operations <NUM>, <NUM>) may be for the initial TB transmission. In this case, the UE may receive multiple active configured grant-free configurations for a given bandwidth part (BWP) of a serving cell. Each grant-free configuration may support a different service type, traffic type, MCS target, etc. The UE can select the particular grant-free configuration to use, based in part, on the expected traffic or service type, MCS target, latency target, etc. for the grant-free communications.

In another example, the first configuration (e.g., in operations <NUM>, <NUM>) may be for the initial TB transmission and the second configuration (e.g., in operations <NUM>, <NUM>) may be for TB retransmission(s). In some cases, the grant-free/SPS for the initial transmission may be configured with a less number of resources than the grant-free/SPS for the retransmission(s). Since the probability of using the retransmission resources may be low, more UEs can be multiplexed on the same resources, leading to better system utilization, enhanced reliability, and lower latency.

Each grant-free/SPS configuration can be UE-specific RRC configured. In one aspect, the gNB may jointly activate the (first and second) grant-free/SPS configurations (e.g., for the initial transmission and retransmission(s)) with a single message. In some aspects, the gNB may independently activate each of the first and second grant-free/SPS configurations. For example, the grant-free/SPS configuration for the first transmission or retransmission(s) may not be activated, in which case the UE may monitor PDCCH for the un-activated grant-free/SPS configuration. In some aspects, the first and/or second configurations may be activated upon receiving the first and second configurations. For example, the RRC configuration of the first and/or second configurations may activate the first and/or second configurations. That is, the RRC configuration by default may be associated with activation.

The gNB may activate the configurations via downlink control information (DCI) or MAC control element (MAC-CE) signaling. The initial transmission and/or retransmission(s) may be associated with multiple SPS configurations and DCI may activate one of the configurations. In some cases, the configuration for retransmission(s) may use a different (or larger) bandwidth part (BWP) compared to the configuration for the initial transmission.

For the grant-free/SPS configuration associated with the initial transmission (e.g., first configuration) and the grant-free/SPS configuration associated with retransmission(s) (e.g., second configuration), RNTIs (for the configurations) may be configured by UE-specific RRC signaling. For example, in some aspects, the same RNTI may be dedicated for the first configuration and the second configuration. In this aspect, one or more bits in the DCI may indicate whether the activation is for the first or the retransmission(s). In some aspects, RNTIs may be different between the first and second configurations (e.g., for the respective initial transmission and the retransmission(s)).

Each grant-free/SPS configuration can include several parameters for the (initial or retransmissions) grant-free/SPS transmissions. The parameters can include at least one of a number of time repetitions and/or (allocated) frequency resources, transmit power, waveform type, rank and precoding matrix, demodulation reference signal (DMRS) configuration, RV sequence, transport block size (TBS), etc. In some cases, the number of repetitions can be semi-statically updated (e.g., by RRC reconfiguration or MAC-CE signaling or activation DCI) as the link quality (e.g., as reported by the via CQI or RRM measurements) changes.

Some of the parameters (and/or a value of some parameters) in the first configuration may be the same or different than parameters (and/or value of parameters) in the second configuration. For example, in some cases, the TBS may be the same between the initial transmission and the retransmission(s). In some examples, the waveform type may be CP-OFDM for the initial transmission, and DFT-S-OFDM for the retransmission(s) (e.g., the UE may switch to DFT-S-OFDM to increase coverage enhancement). In general, however, any of the parameters above may be different or same between the initial transmission and retransmission(s). The parameter(s) may be configured/updated via MAC-CE or L1 signaling. In some aspects, a number of parameters in the second configuration may be smaller than a number of parameters in the first configuration. For example, the network/gNB may choose not to signal again the parameter(s) that are common between the initial transmission and retransmission(s).

In some aspects, performing the grant-free communications (e.g., at <NUM>) may include using a first RV index of the RV sequence in the first set of parameters for the first grant-free communication and using a second RV index of the RV sequence in the second set of parameters for the at least one second grant-free communication. In some aspects, performing the grant-free communications (e.g., at <NUM>) may include using a first RV index of the RV sequence in the first set of parameters for the first grant-free communication and using the first RV index of the RV sequence in the second set of parameters for the at least one second grant-free communication.

There may be different options for RV determination for different transmissions of the same TB(s). For example, assume the same RV sequence is configured for the first and second configurations (that is, the RV sequence in the first set of parameters is the same as the RV sequence in the second set of parameters). In such cases, there may be aspects in which the gNB/UE continues the RV index (e.g., in the retransmissions) from the initial transmission. Alternatively, in such cases, there may aspects in which the gNB/UE resets the RV index (e.g., in the retransmission(s)) from the initial transmission. <FIG> illustrates a reference example of how the RV index can be continued (e.g., Option <NUM>) and how the RV index can be reset (e.g., Option <NUM>) for different transmissions of the same TB(s), according to certain aspects of the present disclosure.

As shown for both Option <NUM> and Option <NUM> in <FIG>, the grant-free/SPS corresponding to the initial transmission supports K=<NUM> (e.g., no repetition), while the grant-free/SPS corresponding to the retransmission supports K=<NUM> (e.g., one repetition). In option <NUM>, the n-th transmission occasion may be associated with the (mod(n-<NUM>,<NUM>)+<NUM>)-th value in the configured RV sequence {RV0, RV1, RV2, RV3}, where n=<NUM>, <NUM>,. , K', and K' represents the total number of repetitions associated with both initial transmission and retransmission. As shown in Option <NUM> in <FIG>, after a NACK is received in the initial transmission (with RV0), the RV sequence continues for the retransmission (e.g., the first repetition of the first retransmission is associated with RV1, and the second repetition of the first retransmission is associated with RV2). As shown in Option <NUM> in <FIG>, after a NACK is received in the initial transmission (with RV0), the RV sequence resets for the retransmission (e.g., the first repetition of the first retransmission is associated with RV0, and the second repetition of the first retransmission is associated with RV1).

In some aspects, different RV sequences may be configured for the initial transmission and retransmission(s) (that is, the RV sequence in the first set of parameters is different from the RV sequence in the second set of parameters). In such cases, the Option <NUM> or Option <NUM> (in <FIG>) may also be used for RV determination. For example, in Option <NUM>, a first RV index of the RV sequence in the first configuration may be used for the initial transmission, and a second RV index of the RV sequence in the second configuration may be used for the retransmission(s). In Option <NUM>, a first RV index of the RV sequence in the first configuration may be used for the initial transmission, and a first RV index of the RV sequence in the second configuration may be used for the retransmission(s). The grant-free/SPS associated with the retransmissions can indicate the same set of RV sequences as in NR (e.g., {<NUM>, <NUM>, <NUM>, <NUM>}, {<NUM>, <NUM>, <NUM>, <NUM>}, {<NUM>, <NUM>, <NUM>, <NUM>}), or new sequences.

Note for the sake of clarity, <FIG> assumes there is a single HARQ ID. However, those of ordinary skill in the art will recognize that the techniques described herein for RV determination may be used for multiple HARQ IDs. Further, as also shown, a larger amount of resources may be allocated for the retransmissions than the initial transmission.

<FIG> illustrates example operations <NUM> for wireless communications, in accordance with aspects of the present disclosure. Operations <NUM> may be performed, for example, by a user equipment (e.g., URLLC UE), such as UE <NUM> shown in <FIG>. Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., processor <NUM>) obtaining and/or outputting signals. In some aspects, operations <NUM> may be performed as part of operations <NUM> (e.g., at <NUM>) in <FIG>.

Operations <NUM> begin, at <NUM>, where the UE sends an initial grant-free transmission to the BS. At <NUM>, the UE receives feedback associated with the initial grant-free transmission from the BS. The feedback may be received via one or more resources dedicated to the UE or via a group DCI associated with a plurality of UEs including the UE. At <NUM>, the UE determines whether to send at least one subsequent grant-free transmission based on the feedback.

Operations <NUM> begin, at <NUM>, where the base station receives an initial grant-free transmission from at least one UE. At <NUM>, the base station sends feedback associated with the initial grant-free transmission to the at least one UE.

According to certain aspects, the gNB may trigger (e.g., at <NUM>/<NUM>) the use of retransmission resources with NACK signaling in the downlink. For example, the UE may (determine to) send the at least one subsequent grant-free transmission if the feedback comprises a NACK. This may enable a reduction in downlink signaling from the multiple bits associated with an uplink grant to one (or a few) bit(s) of NACK. The NACK can be UE-specific or in a group-common DCI shared by multiple UEs. Using NACK in this manner may result in a triggered UL transmission, but instead of triggering with an uplink grant, the retransmission(s) can be triggered by one (or few) bit(s) indicator using pre-configured resource(s). In some aspects, this may also achieve DCI size compression, in the sense that the DCI is pre-transmitted or pre-configured, but triggered by the NACK. In this case, the <NUM>nd grant-free resource may be a resource activated by L1 signaling (e.g., NACK from gNB).

In some cases, the retransmission resources used for the uplink grant-free transmissions may overlap between multiple UEs. For example, assume two UEs both need retransmission. In this case, if a single resource is shared by the two UEs, using a single NACK state to trigger retransmission from both UEs may not be sufficient, as the two NACKs (with the same state) may imply that the shared retransmission resource is for both UEs.

To reduce the likelihood of overlapping retransmission resources, the gNB in some aspects may use multiple bits for ACK/NACK (e.g., in HARQ feedback) to indicate one of multiple different resources for the retransmission. For example, the NACK may include multiple bits, and a value of the multiple bits may indicate resources for the UE to use for the at least one subsequent grant-free transmission. The UE may then send the subsequent grant-free transmission on the resources indicated by the value of the multiple bits. In one example, assuming there are two UEs, the gNB may use two bits for the ACK/NACK to indicate one out of three different resources. That is, each of three states (e.g., "<NUM>", "<NUM>" and "<NUM>") may map to NACK and indicate a different resource, whereas the fourth state (e.g., "<NUM>") may map to ACK, in which case, retransmission may not be needed. Note that while this example uses two bits as a reference example of a multiple state ACK/NACK, those of ordinary skill in the art will recognize that any number of bits may be used for the feedback (e.g., based on the number of UEs subject to using overlapping retransmission resources).

In some aspects, to reduce the likelihood of overlapping retransmission resources, the gNB may schedule one of the UEs with an uplink grant for the retransmission, and the other UE may use the grant-free resources triggered by the NACK bit in the group common DCI. For example, the UE, as part of operations <NUM>, may monitor for a grant for the at least one subsequent grant-free transmission if the feedback includes a NACK, and send the subsequent grant-free transmission (which may be a retransmission of the initial grant-free transmission) in accordance with the received grant.

In some aspects, performing the grant-free communications (e.g., at <NUM>) may include receiving an initial downlink SPS transmission from the BS and sending feedback associated with the initial downlink SPS transmission to the BS. In some aspects, preforming the grant-free communications (e.g., at <NUM>) may include monitoring for the subsequent downlink SPS transmission from the BS if the feedback includes a NACK. For downlink SPS transmissions, the <NUM>nd SPS resource(s) can be implicitly monitored when UE sends a NACK. In this aspect, the PDCCH grant for the retransmission can be completely saved (e.g., unused). The UE can transmit NACK if packet fails, and may monitor/receive retransmission on <NUM>nd SPS resources. The gNB, upon receiving the NACK, can use the <NUM>nd SPS for retransmission.

In some cases, for downlink SPS, when retransmission resources are shared across UEs, a single NACK state may not be enough to prevent an overlap of retransmission resources. For example, if two UEs both need retransmission, a single NACK (from each UE) may result in the two UEs expecting retransmission on the same shared <NUM>nd SPS resource. In some aspects, the reduce the likelihood of an overlap, each UE can use multiple bits (e.g., two bits or more) for ACK/NACK to indicate one out of multiple different SPS configurations/resources (e.g., one out of <NUM> different configurations, assuming <NUM> bits are used) to be monitored for that occasion. For example, the NACK can include multiple bits, a value of the multiple bits can indicate resources for the UE to use for monitoring for the subsequent downlink SPS transmission, and the resources indicated by the multiple bits can be monitored by the UE for the subsequent downlink SPS transmission. This multiple bit feedback scheme for downlink SPS may be similar to the multiple bit feedback scheme described above for uplink grant-free. Note, however, that in some cases, there may still be a collision (when receiving the 2nd downlink SPS transmission) among the set of resources selected by the different UEs, but the likelihood of collision may be less than the likelihood of collision associated with a semi-static partitioning and assignment of retransmission resources by the gNB.

In some aspects, to reduce the likelihood of overlap for downlink SPS transmissions, one of the UEs can be scheduled with a dynamic grant for receiving a subsequent downlink transmission (e.g., a retransmission of the initial downlink SPS transmission), and another of the UEs can receive PDSCH on the <NUM>nd SPS resource(s). In some cases, the gNB may configure the UE (e.g., in the first and/or second configurations) to monitor PDCCH anyway in addition to the SPS resources.

In some aspects, to reduce the likelihood of overlap for downlink SPS transmissions, the gNB via common DCI can signal the retransmission resources for multiple UEs. This aspect may be similar to GC-DCI for uplink grant-free resource monitoring.

In some aspects, to reduce the likelihood of overlap for downlink SPS transmissions, the UE(s) may blindly decode the multiple PDSCH resources for the <NUM>nd SPS retransmission(s). This aspect may be efficient from a collision handling perspective, but may impact the UE processing timeline.

HARQ feedback may be transmitted for uplink-grant-free transmissions and downlink SPS transmissions. For example, the gNB may send HARQ feedback associated with uplink-grant-free transmissions, and the UE may send HARQ feedback associated with downlink SPS transmissions. In NR, the gNB may send HARQ feedback for UL data on PDCCH (e.g., there may not be a PHICH in NR). The UE may send HARQ feedback on PUCCH.

In some aspects, to reduce HARQ overhead for uplink grant-free transmissions, the gNB may send ACK/NACK feedback in group common DCI (GC-DCI) shared by multiple UEs. The HARQ feedback in the GC-DCI may be received by the UE (e.g., at <NUM>).

In some aspects, to reduce HARQ overhead for uplink grant-free transmissions, the gNB may perform ACK/NACK multiplexing for different HARQ-IDs. For example, HARQ feedback at DL symbol n may contain ACK/NACK for up to m possible previous HARQ-IDs (e.g., m = <NUM>, <NUM>, or <NUM>). In some cases, the HARQ feedback may include a bitmap for each UE, and the bitmap may include multiplexed (or bundled) ACK/NACKs. The value m may be fixed or may be UE-specific RRC signaled.

Similarly, in some aspects, to reduce HARQ overhead for downlink SPS transmissions, the UE may perform ACK/NACK multiplexing for different HARQ-IDs. In this aspect, the UE may use a larger PUCCH resource in frequency and/or time (compared to the PUCCH resource used for non-multiplexed ACK/NACK). The PUCCH resource(s) can be RRC configured and/or signaled within DCI activation.

In some cases, there may be one or more timing issues associated with HARQ feedback in GC-DCI. For example, HARQ feedback for uplink grant-free transmissions (in NR) is generally a synchronous transmission, meaning the HARQ ID is implicitly derived based on specific transmission time. However, a problem may arise when different UEs each with multiple HARQ processes have multiplexed ACK/NACKs in GC-DCI (e.g., it may be hard to have synchronous transmission for all UEs in GC-DCI). Thus, it may be desirable to provide UEs with techniques for determining which ACK/NACK field in GC-DCI corresponds to its HARQ-ID(s).

According to certain aspects, the UE may determine/identify the ACK/NACK field in the GC-DCI that corresponds to its HARQ-ID(s) based on a single HARQ ID.

According to certain aspects, the HARQ feedback may be associated with multiple HARQ IDs. For example, the ACK/NACK bit(s) (in the HARQ feedback) corresponding to each UE may represent multiplexed ACK/NACK for a window of I last HARQ IDs. In such cases, the UE may determine the number of its HARQ IDs multiplexed in GC-DCI based on the number of HARQ occasions within the window (no matter whether the UE has sent data in that occasion or not), the time instance of the GC-DCI transmission, and the time gap between its last possible HARQ ID and GC-DCI transmission. In some aspects, the UE may not expect to receive ACK/NACK for its last HARQ ID(s) if the time gap is less than u symbols, where u is UE-specific RRC configured or a fixed value. The value I can be semi-statically fixed for all UEs or UE specific RRC signaled. In some aspects, a fixed I may be used (e.g., which may make decoding easier). In some aspects, I may be associated/determined based on a semi-static HARQ window.

In some aspects, performing the grant-free communications (e.g., at <NUM>) may include determining at least one of the initial grant-free transmission or the at least one subsequent grant-free transmission is successful if feedback is not received within a time window after sending at least one of the initial grant-free transmission or the at least one subsequent grant-free transmission. In particular, to reduce HARQ overhead for uplink grant-free transmissions/downlink SPS transmissions, the gNB/UE may send selective NACK feedback. That is, the receiver (e.g., gNB, UE, etc.) may only transmit NACK when it fails to decode the packet, otherwise the receiver may refrain from sending feedback (from which the transmitter implies ACK). In some cases, the gNB may configure a timeline (or timeline window) for the DL/UL feedback. Within the window, the receiver (e.g., gNB, UE, etc.) may transmit NACK if the packet fails. The transmitter (e.g., UE, gNB, etc.) may assume ACK if it does not receive NACK within the window. In some cases, since BLER corresponding to the initial transmission may be small (e.g., <NUM>-<NUM>), the selective NACK can reduce the overall feedback overhead (e.g., especially for the initial transmission). The PUCCH resource(s) for selective NACK associated with downlink SPS can be RRC configured and/or signaled within DCI activation.

In some cases, there may be additional issues for selective NACK in an unlicensed environment. For example, in an unlicensed environment, there could be a listen before talk (LBT) failure. In this case, in some aspects, the receiver could perform selective NACK together with the TXOP (e.g., timeline window) indication. This may be beneficial for DL ACK/NACK feedback for UL packet(s). For example, if the configured feedback timeline window is within the DL slots of a TXOP and the gNB does not transmit NACK, the UE may assume the packet is successful. On the other hand, such a scheme may not work well in UL ACK/NACK feedback if the UE has to do additional CCA within the gNB indicated TXOP, in which case it may not be possible to skip an ACK from the UE. For example, if the gNB does not receive an NACK from the UE within the window, it may be because the UE was not clear to transmit (in the unlicensed band), and not that the UE successfully decoded the downlink packet.

NR may support advanced CSI (A-CSI) feedback. In such cases, for uplink grant-free/downlink SPS, an A-CSI report may be triggered by NACK. This triggering may happen, e.g., when the packet is not successfully delivered/decoded after an initial transmission. In some aspects, A-CSI reporting can be triggered when ACK is quickly received to increase MCS or to decrease the number of repetitions in order to enhance system utilization. The gNB may trigger an A-CSI report for the last m out of K (m ≤ K) receptions in current grant-free/SPS configuration. The triggering can be UE specific or for a group of UEs. MCS can be adjusted when configuring the next (re)-transmission.

For downlink SPS transmissions, the PUCCH resource(s) for A-CSI feedback may be semi-statically configured with SPS configuration. For example, a NACK reception (e.g., by the gNB) may trigger an A-CSI report (e.g., from the UE). The NACK and A-CSI can be multiplexed on the same resource or mapped to different resources.

For uplink grant-free transmissions, one the gNB transmits NACK, e.g., in GC-DCI, this may implicitly or explicitly trigger an A-CSI from the UE. Once A-CSI is triggered, it can be piggybacked on PUSCH or it can be transmitted on a separate resource (e.g., configured within SPS configuration or indicated within DCI). In cases where A-CSI is multiplexed with PUSCH, a small beta may be desirable to maintain a high reliability for PUSCH.

In some cases, there may timeline issues associated with reporting HARQ feedback. For example, the PDSCH to HARQ-ACK timeline (e.g., k<NUM>) is typically RRC configured or signaled with DCI activation. Upon detection of a DL SPS PDSCH in slot n, the UE may transmit HARQ-ACK in slot n+k<NUM>. However, there may be situations in which there is at least one semi-statically configured DL symbol that overlaps with the symbol(s) carrying HARQ-ACK in slot n+k<NUM>. Accordingly, it may be desirable to provide techniques for transmitting HARQ feedback in such cases.

In some aspects, the UE can rate-match around the overlap. For example, since the gNB has knowledge of the SFI, the UE can rate match around the semi-statically configured DL symbol(s). In some aspects, the UE can drop the ACK/NACK transmission, e.g., if the non-overlapping resources are insufficient (e.g., below a threshold) for reliable PUCCH transmission. In this aspect, the gNB may assume a NACK. In some cases, the UE may still transmit on remaining non-overlapping resources if the UE is sending an ACK. However, if it is a NACK, the UE may not transmit in order to prevent NACK to ACK error at the gNB. In some aspects, the UE may transmit HARQ-ACK feedback in slot n+k'<NUM>, where slot n+k'<NUM> is the first slot after n+k<NUM> in which none of the symbols carrying HARQ-ACK overlap with semi-statically configured DL symbols. In this case, the UE may perform HARQ-ACK multiplexing/bundling, e.g., in slot n+k'<NUM>.

In some cases, there may be situations when there is at least one semi-statically configured UL symbol that overlaps with DL SPS symbol(s) carrying PDSCH in slot n. In such situations, the gNB, in some aspects, can puncture or rate match around the UL symbols. In some aspects, the gNB can drop the PDSCH transmission, e.g., if non-overlapping resources are insufficient (e.g., below a threshold) for reliable PDSCH transmission.

In some cases, there may be situations when there is at least one semi-statically configured DL symbol that overlaps with UL grant-free symbol(s) carrying PUSCH in slot n. In such situations, since the gNB is aware of the SFI, the UE, in some aspects, can rate match around the DL symbol(s). In some aspects, the UE may drop the PUSCH transmission, e.g., if non-overlapping resources are insufficient (e.g., below a threshold) for reliable PUSCH transmission.

In some cases, rather than actually transmitting a frame, a device may have an interface to output a frame for transmission. For example, a processor may output a frame, via a bus interface, to an RF front end for transmission. Similarly, rather than actually receiving a frame, a device may have an interface to obtain a frame received from another device. For example, a processor may obtain (or receive) a frame, via a bus interface, from an RF front end for transmission.

For example, means for transmitting, means for sending, means for communicating, means for performing, means for signaling, means for configuring, means for monitoring, means for indicating, means for detecting, means for triggering and/or means for receiving may comprise one or more of a transmit processor <NUM>, a TX MIMO processor <NUM>, a receive processor <NUM>, or antenna(s) <NUM> of the base station <NUM> and/or the transmit processor <NUM>, a TX MIMO processor <NUM>, a receive processor <NUM>, or antenna(s) <NUM> of the user equipment <NUM>. Additionally, means for generating, means for scheduling, means for activating, means for multiplexing, means for detecting, means for decoding, means for triggering, means for dropping, means for reducing, means for allocating, means for monitoring, means for performing, means from refraining, means for identifying, means for puncturing, means for rate-matching, means for configuring, means for supporting, means for using, means for determining and/or means for applying may comprise one or more processors, such as the controller/processor <NUM> of the base station <NUM> and/or the controller/processor <NUM> of the user equipment <NUM>.

For example, the instructions may include the instructions for performing the operations described herein and illustrated in <FIG>.

Claim 1:
A method (<NUM>) for wireless communications by a user equipment, UE, comprising:
receiving (<NUM>) a first configuration for a first grant-free communication;
receiving (<NUM>) a second configuration for at least one second grant-free communication; and
performing (<NUM>) grant-free communications with a base station, BS, based on the first configuration and the second configuration respectively, wherein the first grant-free communication is an initial uplink grant-free transmission; and
the at least one second grant-free communication is at least one retransmission of the initial uplink grant-free transmission;
wherein the first configuration includes a first set of resources, and the second configuration includes a second set of resources, and
wherein the first set of resources has fewer resources than the second set of resources, wherein the UE and another UE are multiplexed on the second set of resources for the retransmission of the initial uplink grant-free transmission.