Patent Description:
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 eNodeB (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 node-B (NR NB), a network node, <NUM> NB, gNB, etc.). A base station or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station or to a UE) and uplink channels (e.g., for transmissions from a UE to a base station or distributed unit).

<NPL> provides a summary of agreements made regarding PUCCH resource allocation, namely:
A set of PUCCH resources at least for HARQ-ACK which is configured to a UE by high layer signaling is defined as one of followings (to be down-selected).

The invention is described herein with reference to the appended claims. Certain aspects provide a method for wireless communication in accordance with claim <NUM>.

Certain aspects provide a wireless device according to claim <NUM>.

New radio (NR) or <NUM> technology may support various wireless communication services, such as Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. <NUM> or 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). In LTE, the basic transmission time interval (TTI) or packet duration is <NUM> subframe. In NR, a subframe may still be <NUM>, but the basic TTI may be referred to as a slot. A subframe may contain a variable number of slots (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,. slots) depending on the tone-spacing (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Aspects of the present disclosure relate to determining UL resources to use for transmitting acknowledgement messages (ACKs) implicitly based on DL resources used for communicating a DL grant.

For example, the wireless network may be a new radio (NR) or <NUM> network. NR wireless communication systems may employ short uplink bursts. As described herein, for example, UE <NUM> may receive a DL grant for receiving data on a DL channel from BS <NUM>. UE <NUM> may determine, implicitly, which resources on the UL to use to transmit an ACK to BS <NUM> for the data received on the DL channel based on the resources over which the DL grant is received, and transmit the ACK. BS <NUM> may also determine, implicitly, which resources include the ACK on the UL, and receive the ACK from UE <NUM>.

As illustrated in <FIG>, the wireless network <NUM> may include a number of 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 3GPP, the term "cell" can refer to a coverage area of a Node B and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term "cell" and gNB, Node B, <NUM> NB, AP, NR BS, NR BS, or TRP may be interchangeable. In some examples, the base stations 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.

The wireless communication network <NUM> may also include relay stations.

The wireless communication network <NUM> may support synchronous or asynchronous operation.

The BSs <NUM> may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

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) devices.

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> resource blocks), 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 cyclic prefix (CP) on the uplink and downlink and include support for half-duplex operation using time division duplexing (TDD). A single component carrier (CC) bandwidth of <NUM> may be supported. NR resource blocks may span <NUM> subcarriers with a subcarrier bandwidth of <NUM> over a <NUM> duration. Each radio frame may consist of <NUM> half frames, each half frame consisting of <NUM> subframes, with a length of <NUM>. Consequently, each subframe may have a length of <NUM>. Each subframe may indicate a link direction (i.e., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. UL and DL subframes for NR may be as described in more detail below with respect to <FIG>. Alternatively, NR may support a different air interface, other than an OFDM-based. NR networks may include entities such central units (CUs) and/or distributed units (DUs).

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., gNB, <NUM> Node B, Node B, transmission reception point (TRP), access point (AP)) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells). For example, the RAN (e.g., a CU or DU) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals (SS), but in some cases DCells may transmit SS. NR BSs may transmit downlink signals to UEs indicating the cell type. Based on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based on the indicated cell type.

The logical architecture <NUM> may be used to illustrate fronthaul definition. The logical architecture <NUM> may support fronthauling solutions across different deployment types. For example, the logical architecture <NUM> may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The logical architecture <NUM> may share features and/or components with LTE. The next generation AN (NG-AN) <NUM> may support dual connectivity with NR. The NG-AN <NUM> may share a common fronthaul for LTE and NR.

The logical architecture <NUM> may enable cooperation between and among TRPs <NUM>. There may be no inter-TRP interface.

Logical architecture <NUM> may have a dynamic configuration of split logical functions.

<FIG> illustrates an example physical architecture <NUM> of a distributed RAN, according to aspects of the present disclosure. The C-CU <NUM> may be centrally deployed.

<FIG> illustrates example components of the BS <NUM> and UE <NUM> illustrated in <FIG>, which may be used to implement aspects of the present disclosure. The BS may include a TRP and may be referred to as a Master eNB (MeNB) (e.g., Master BS, primary BS). Master BS and the Secondary BS may be geographically co-located.

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>, Tx/Rx <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 <NUM> described herein and illustrated with reference to <FIG> and complementary operations.

For a restricted association scenario, the BS <NUM> may be the macro BS 110c in <FIG>, and the UE <NUM> may be the UE 120y. The BS <NUM> may also be a BS of some other type. The BS <NUM> may be equipped with antennas 434a through 434t, and the UE <NUM> may be equipped with antennas 452a through 452r.

The control information may be for the Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel (PDCCH), etc. The data may be for the Physical Downlink Shared Channel (PDSCH), etc. The processor <NUM> may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor <NUM> may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal (CRS).

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 complementary 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.

The illustrated communications protocol stacks may be implemented by devices operating in a <NUM> system.

<FIG> is a diagram showing an example of a DL-centric subframe <NUM>. The DL-centric subframe <NUM> may include a control portion <NUM>. The control portion <NUM> may exist in the initial or beginning portion of the DL-centric subframe <NUM>. The DL-centric subframe600 may also include a DL data portion <NUM>. The DL data portion <NUM> may be referred to as the payload of the DL-centric subframe <NUM>.

The DL-centric subframe <NUM> may also include a common UL portion <NUM>. The common UL portion <NUM> may sometimes be referred to as an UL burst, a common UL burst, and/or various other suitable terms. The common UL portion <NUM> may include feedback information corresponding to various other portions of the DL-centric subframe. For example, the common UL portion <NUM> may include feedback information corresponding to the control portion <NUM>. Non-limiting examples of feedback information may include an ACK signal, a NACK signal, a HARQ indicator, and/or various other suitable types of information. The common UL portion <NUM> may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests (SRs), and various other suitable types of information. As illustrated in <FIG>, the end of the DL data portion <NUM> may be separated in time from the beginning of the common UL portion <NUM>. One of ordinary skill in the art will understand that the foregoing is merely one example of a DL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

<FIG> is a diagram showing an example of an UL-centric subframe <NUM>. The UL-centric subframe <NUM> may include a control portion <NUM>. The control portion <NUM> may exist in the initial or beginning portion of the UL-centric subframe. The control portion <NUM> in <FIG> may be similar to the control portion described above with reference to <FIG>. The UL-centric subframe <NUM> may also include an UL data portion <NUM>. The UL data portion <NUM> may sometimes be referred to as the payload of the UL-centric subframe <NUM>. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS). In some configurations, the control portion <NUM> may be a physical UL control channel (PUCCH).

As illustrated in <FIG>, the end of the control portion <NUM> may be separated in time from the beginning of the UL data portion <NUM>. The UL-centric subframe <NUM> may also include a common UL portion <NUM>. The common UL portion <NUM> in <FIG> may be similar to the common UL portion <NUM> described above with reference to <FIG>. The common UL portion <NUM> may additionally or alternatively include information pertaining to channel quality indicator (CQI), sounding reference signals (SRSs), and various other suitable types of information. One of ordinary skill in the art will understand that the foregoing is merely one example of an UL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

In certain aspects, a first device (e.g., UE <NUM>) may be configured to acknowledge receipt of data received from a second device (e.g., BS <NUM>). For example, UE <NUM> may receive data from BS <NUM> on a DL channel (e.g., PDSCH). If the UE <NUM> is able to successfully decode the received data, UE <NUM> may send an acknowledgement message (ACK) to the BS <NUM> on an UL channel (e.g., PUCCH). The BS <NUM> receiving the ACK from the UE <NUM> may determine that the UE <NUM> has successfully received the data and determine that it does not need to retransmit the data to the UE <NUM> (e.g., as part of a hybrid automatic repeat request (HARQ) procedure). If the BS <NUM> does not receive the ACK from the UE <NUM>, or receives a negative ACK (NACK) it may retransmit the data to the UE <NUM>.

In certain aspects, the BS <NUM> may explicitly signal to the UE <NUM> the resources (e.g., time resources, frequency resources, etc.) of the PUCCH to use for transmitting an ACK for particular data (e.g., a transmission such as transport block (TB), etc.) sent by the BS <NUM> to the UE <NUM> on the PDSCH. The BS <NUM> may include the explicit signaling in the PDCCH. Accordingly, if the BS <NUM> transmits data transmissions to multiple UEs <NUM> and/or transmits multiple different data transmissions to a UE <NUM>, the ACKs for the different transmissions may be scheduled on different resources of the PUCCH. Therefore, the BS <NUM> can determine which ACK corresponds to which data transmission based on the resource the ACK is received on the PUCCH, and determine whether or not to retransmit that particular data transmission.

However, explicitly signaling in the PDCCH the resources on the PUCCH to use for transmitting each ACK may utilize network bandwidth for the signaling, and therefore increase network overhead in the network, thereby reducing overall data throughput. For example, the ACK may only be <NUM> or <NUM> bits, and therefore adding additional explicit signaling to grant resources to transmit <NUM> or <NUM> bits may create a lot of overhead. Accordingly, certain aspects herein relate to implicitly mapping the resources on which a DL grant for the PDSCH is received in the PDCCH to UL resources on the PUCCH to utilize for communicating the ACK for the data on the PUCCH. Both a UE and BS may perform the implicit mapping, the UE to determine which PUCCH resources to use to transmit the ACK and actually transmit the ACK, and the BS to receive the ACK and determine which data transmission the ACK is for based on the PUCCH resources on which it is received.

In certain aspects, BS <NUM> may transmit DL grants to one or more UEs <NUM> in the PDCCH. Each DL grant indicates to a UE <NUM> resources on a PDSCH allocated to the UE <NUM> for the BS <NUM> to send data to the UE <NUM>. Based on the DL grant received in the PDCCH, the UE <NUM> receives data on the granted resources indicated in the DL grant on the PDSCH. The UE <NUM> then transmits an ACK to the BS <NUM> on the PUCCH for the data received on the PDSCH from the BS <NUM>. The techniques herein, in certain aspects, allow the UE <NUM> (and BS <NUM>) to determine which resources of the PUCCH to utilize to communicate the ACK.

In certain aspects, the PDCCH carries control information, and in particular, carries UE-specific scheduling assignments for DL resource allocation, UL grants, PRACH responses, UL power control commands, and/or common scheduling assignments for signaling messages (e.g., system information, paging, etc.). The PDCCH may span a number of subcarriers in the frequency domain and a number of OFDM symbols in the time domain. The minimum resource element of a PDCCH may be referred to as a resource element (RE) and correspond to one OFDM symbol and one subcarrier. REs may be grouped into resource element groups (REGs). Each REG may include a number of (e.g., <NUM> consecutive) REs within the same OFDM symbol and the same resource block (RB). REGs may be grouped into control channel elements (CCEs). Each CCE may include a number of (e.g., <NUM> contiguous) REGs. The CCEs in the PDCCH may be indexed and each CCE referenced by index number corresponding to the position of the CCE in the PDCCH.

In certain aspects, an ACK resource index is derived based on the CCE index (e.g., starting/lowest CCE index) of the CCE (e.g., starting/lowest CCE) in which a DL grant is communicated in the PDCCH. In certain aspects, an ACK resource index is derived based on the ending/highest CCE index of the CCE (e.g., ending/highest CCE) in which a DL grant is communicated in the PDCCH. For example, the BS <NUM> may communicate a DL grant for resources in the PDSCH in a CCE in the PDCCH to a UE <NUM>. The UE <NUM> may receive the DL grant on the PDCCH and determine based on the DL grant the resources in the PDSCH to receive data from the BS <NUM>. The UE <NUM> may receive the data in the PDSCH from the BS <NUM> on the resources indicated in the DL grant. The UE <NUM> may further determine the resources to utilize to transmit an ACK for the received data in the PDSCH to the BS <NUM> based on the CCE index of the CCE in which the DL grant was received.

In particular, the UE <NUM> may be configured to map the CCE index of the DL grant to an ACK resource index. The ACK resource index may further be mapped to an RB index, cyclic shift index, and/or an orthogonal cover code index. The RB index may indicate an RB to utilize in the PUCCH for transmitting the ACK. The cyclic shift index may indicate a cyclic shift to apply to the ACK. The orthogonal cover code index may indicate an orthogonal cover code to apply to the ACK. The RB used, cyclic shift used, and orthogonal cover code used may correspond to a PUCCH resource as discussed herein. For example, each unique combination of RB, cyclic shift, and orthogonal cover code may correspond to a different PUCCH resource that is distinct from other PUCCH resources. It should be noted that in certain aspects a PUCCH resource may be defined by other parameters that make it distinct from other PUCCH resources. For example, the UE <NUM> may then utilize the PUCCH resource determined by the CCE index and some explicit signaling (e.g., utilizing the ACK resource index (ARI)) to transmit the ACK in the PUCCH to the BS <NUM> for the received data in the PDSCH.

<FIG> illustrates an example mapping of PDCCH <NUM> resources to PUCCH <NUM> resources. As shown in <FIG>, PDCCH <NUM> includes a first DL grant <NUM> transmitted in one or more CCEs having a first starting CCE index. PDCCH <NUM> further includes a second DL grant <NUM> transmitted in one or more CCEs having a second starting CCE index. The first starting CCE index corresponding to the first DL grant <NUM> maps to a first PUCCH resource <NUM> on PUCCH <NUM>. The second starting CCE index corresponding to the second DL grant <NUM> maps to a second PUCCH resource <NUM> on PUCCH <NUM>.

In certain aspects, where carrier aggregation (CA) is used, BS <NUM> may transmit different PDCCH on multiple carriers (e.g., different frequency bandwidths). Each of the different PDCCHs may include DL grants for different carriers. However, the CCE indexes in which DL grants are transmitted on different carriers may be the same. For example, BS <NUM> may transmit a first DL grant on a first carrier starting at CCE index <NUM>. The BS <NUM> may further transmit a second DL grant on a second carrier also starting at CCE index <NUM>. Further, the number of carriers used for the DL and UL may not be the same. For example, the DL may use <NUM> carriers, and the UL only <NUM> carrier. Accordingly, the UE for which the first DL grant is directed may, based on the CCE index of the first DL grant, map the ACK to the same PUCCH resource on the <NUM> UL carrier as the UE for which the second DL grant is directed due to the CCE index being the same. In order to resolve such conflicts/collisions, explicit signaling (e.g., an ARI in the downlink control information(DCI)) may be included in the PDCCH. The explicit signaling may indicate a different resource or offset for one of the UEs to utilize (e.g., associated with the first DL grant or the second DL grant).

In certain aspects, such as in NR systems, the PDCCH may be divided into multiple CORESETs. In particular, each UE <NUM> may only monitor (e.g., receive) a subset of the entire PDCCH region referred to as a CORESET of the UE <NUM>. The CCE index, however, may be relative within a CORESET. Therefore, a DL grant for a first UE in a first CORESET may have the same CCE index as a DL grant for a second UE in a second CORESET, and therefore both the first UE and second UE may map the CCE index to the same PUCCH resource for ACK transmission leading to a collision.

<FIG> illustrates an example mapping of PDCCH <NUM> resources to PUCCH <NUM> resources. As shown, PDCCH <NUM> includes a first DL grant <NUM> transmitted in a first CORESET in one or more CCEs having a first starting CCE index. PDCCH <NUM> further includes a second DL grant <NUM> transmitted in a second CORESET in one or more CCEs having the first starting CCE index. Since the first DL grant <NUM> and the second DL grant <NUM> have the same starting CCE index within the CORESET, they map to the same PUCCH resource <NUM> on PUCCH <NUM>, leading to a collision.

Accordingly, in certain aspects, the UE <NUM> (and BS <NUM>) may be configured to derive a PUCCH resource (e.g., an ARI) for ACK transmission based on both a CCE index and CORESET index (e.g., indicating the CORESET) in which the DL grant is included in the PUCCH. For example, the UE <NUM> (and BS <NUM>) may add a CORESET dependent offset to the PUCCH resource (e.g., one or more of the parameters of the PUCCH resource, to the ARI, etc.) indicated by the CCE index. <FIG> illustrates an example such mapping of PDCCH <NUM> resources to PUCCH <NUM> resources. As shown, PDCCH <NUM> includes a first DL grant <NUM> transmitted in a first CORESET in one or more CCEs having a first starting CCE index. PDCCH <NUM> further includes a second DL grant <NUM> transmitted in a second CORESET in one or more CCEs having the first starting CCE index. Since the first DL grant <NUM> and the second DL grant <NUM> have the same starting CCE index but a different CORESET index, they map to different PUCCH resources <NUM> and <NUM>, respectively, on PUCCH <NUM>.

In certain aspects, the number of PUCCH resources to be reserved when mapping based on CCE index and CORESET index depends on the total DL PDCCH bandwidth, meaning that utilizing CORESET dependent mapping does not require more PUCCH resources be reserved than UEs <NUM> receiving the PDSCH DL grant on the PDCCH. In certain aspects, a global CCE index across multiple CORESETs may be used so the mapping function based on CCE index works with multiple CORESETs.

In certain aspects, PDCCH may be transmitted in multiple slots (in the time domain) using cross slot scheduling. A UE <NUM> may determine which slot includes the PDSCH for which a DL grant is received in the PDCCH based on a time offset value (e.g., K0 value, which may be configured using RRC configuration) from the PDCCH time slot in which the DL grant is received to the PDSCH time slot the DL grant is for. The UE <NUM> may further determine which time slot to transmit ACK in the PUCCH based on a time offset value (e.g., K1 value, which may be configured using RRC configuration, in the DCI, as part of the DL grant, etc.) from the PDSCH time slot where data is received to the PUCCH time slot to use for the ACK. Therefore, in certain cases, though PDSCH may be transmitted in different slots for different UEs <NUM> (e.g., due to PDCCH being transmitted in different time slots and/or different K1 values used), they may utilize the same time slot in the PUCCH for transmitting ACK.

<FIG> illustrates an example mapping of PDCCH 1001a and 1001b resources to PUCCH <NUM> resources. As shown, PDCCH 1001a corresponds to PDCCH transmitted in a first time slot and includes a first DL grant <NUM> transmitted in one or more CCEs having a first starting CCE index. PDCCH 1001b corresponds to PDCCH transmitted in a second time slot and includes a second DL grant <NUM> transmitted in one or more CCEs having the first starting CCE index. Since the first DL grant <NUM> and the second DL grant <NUM> have the same starting CCE index, they map to the same PUCCH resource <NUM> on PUCCH <NUM>, leading to a collision. Further, if BS <NUM> wants to schedule a single UE <NUM> to transmit ACK for different slots/K1 values simultaneously, it has to use the same CCE index in the PDCCH, leading to scheduling constraints.

Accordingly, in certain aspects, the UE <NUM> (and BS <NUM>) may be configured to derive a PUCCH resource (e.g., an ARI) for ACK transmission based on both a CCE index and slot index (e.g., of the PDCCH including the DL grant, or the PDSCH of the DL grant) and/or K1 value (for the DL grant). For example, the UE <NUM> (and BS <NUM>) may add a slot index/K1 dependent offset to the PUCCH resource (e.g., one or more of the parameters of the PUCCH resource, to the ARI, etc.) indicated by the CCE index. <FIG> illustrates an example such mapping of PDCCH 1001a and 1001b resources to PUCCH <NUM> resources. As shown, PDCCH 1001a corresponds to PDCCH transmitted in a first time slot and includes a first DL grant <NUM> transmitted in one or more CCEs having a first starting CCE index. PDCCH 1001b corresponds to PDCCH transmitted in a second time slot and includes a second DL grant <NUM> transmitted in one or more CCEs having the first starting CCE index. Since the first DL grant <NUM> and the second DL grant <NUM> have the same starting CCE index, but a different slot index and/or K1 value, they map to different PUCCH resources <NUM> and <NUM>, respectively, on PUCCH <NUM>.

In certain aspects, the number of PUCCH resources to be reserved when mapping based on CCE index and slot index and/or K1 value is greater than the number of UEs <NUM> receiving the PDSCH DL grant on the PDCCH. Therefore, certain PUCCH resources may go unutilized. In particular, if the number of possible K1 values for the DL grant for a UE <NUM> is Z, and there are Y UEs <NUM> receiving DL grant, then there are Y*Z possible PUCCH resources the DL grant could map to for transmitting ACK to avoid collisions. However, only Y of such PUCCH resources may actually be utilized for ACK. Accordingly, in certain aspects, unused PUCCH resources may be reassigned to other UEs or even channels to carry other information (e.g., explicit PUCCH resource mapping, other signaling, other control information, other data, etc.).

In certain aspects, where the PUCCH resource is mapped based on CCE index and slot index and/or K1 value, if a single UE <NUM> uses different K1 values for different DL grants, they may be mapped to different PUCCH resources. However, it may be more efficient for the UE <NUM> to use the same PUCCH resource to transmit ACK for multiple DL grants. Accordingly, in certain aspects, if a single UE uses different K1 values for different DL grants, a single PUCCH resource is used to transmit the ACK. The PUCCH resource may correspond to one (e.g., the latest or earliest) of the multiple PUCCH resources mapped to by the different slot index and/or K1 value. In certain aspects, a single PUCCH resource of the multiple PUCCH resources is selected when the total number of bits for the ACK payload is less than or equal to <NUM> (e.g., <NUM> PDSCH to ACK). In certain aspects, if the total number of bits for the ACK payload is greater than <NUM>, the PDCCH (e.g., as part of the DL grant, a new UL grant, etc.) may include explicit mapping/scheduling of one or more PUCCH resources for the UE <NUM> to use to transmit ACK.

In certain aspects, such as in NR, the PUCCH may be divided into multiple regions for the UL part, a long duration part and a short duration part. The long duration part may comprise some of the symbols (a greater number of symbols) of the PUCCH, and the short duration part may comprise some of the symbols (a lesser number of symbols) of the PUCCH. UEs <NUM> may transmit in either the long duration part or short duration part of the PUCCH. For UEs <NUM> with very good signal quality with the BS <NUM>, they may be able to utilize the short duration part to communicate (e.g., an ACK) with the BS <NUM> as the ACK can be successfully communicated even over the shorter duration. However, for UEs <NUM> with poorer signal quality with the BS <NUM>, they may only be able to utilize the long duration part to communicate (e.g., an ACK) with the BS <NUM> as the ACK may need to be coded across more bits or transmitted more times for successful communication. Therefore, UE <NUM> may utilize the long duration part or the short duration part depending on channel quality between UE <NUM> and BS <NUM>.

Therefore, in certain aspects, the DL grant in the PDCCH further indicates to UE <NUM> whether to transmit an ACK in the short duration part or the long duration part of the PUCCH. In certain aspects, a portion of the PDCCH (e.g., certain CCE indexes) is reserved for long duration PUCCH scheduling and a portion of the PDCCH (e.g., certain CCE indexes) is reserved for short duration PUCCH scheduling. Accordingly, the UE <NUM> (and BS <NUM>) determines whether to use a PUCCH resource in the long duration part or the short duration part to transmit ACK based on the CCE index and whether that index maps to the short duration part or long duration part.

<FIG> illustrates an example mapping of PDCCH <NUM> resources to PUCCH long duration 1111a and PUCCH short duration 1111b resources. As shown, PDCCH <NUM> includes a first DL grant <NUM> transmitted in one or more CCEs having a first starting CCE index that is reserved for mapping to PUCCH long duration 1111a. PDCCH <NUM> includes a second DL grant <NUM> transmitted in one or more CCEs having a second starting CCE index that is reserved for mapping to PUCCH short duration 1111b. As shown, based on the first starting CCE index associated with the first DL grant <NUM>, a first PUCCH resource <NUM> in the PUCCH long duration 1111a is mapped. Based on the second starting CCE index associated with the second DL grant <NUM>, a second PUCCH resource <NUM> in the PUCCH short duration 1111b is mapped.

In certain aspects, based on the example of FIG. 11A, if a BS <NUM> wants to schedule a UE <NUM> to transmit ACK in a particular part (PUCCH long duration 1111a or PUCCH short duration 1111b), BS <NUM> must transmit the DL grant to UE <NUM> in a CCE in the PDCCH associated with the part. This may increase a PDCCH blocking rate, meaning that the BS <NUM> can only schedule so many UEs <NUM> in a particular part dependent on how many CCEs are reserved for that part.

Accordingly, in certain aspects, CCEs may not be reserved for a particular part (PUCCH long duration 1111a or PUCCH short duration 1111b). Instead, the UE <NUM> may be separately configured to utilize one of the parts for ACK transmission and the CCE index may just indicate a PUCCH resource in the configured part. Therefore, any CCE index can map to either part. In certain aspects, whether a UE <NUM> should use the long duration part or the short duration part is indicated (e.g., using <NUM> bit) in RRC configuration, DCI, or some other signaling (e.g., as part of the DL grant). Accordingly, first DL grant <NUM> for example, could map to either first PUCCH resource <NUM> or second PUCCH resource <NUM> based on the configuration of UE <NUM>.

In certain aspects, the number of PUCCH resources to be reserved when mapping based on CCE index and an indication of which part of PUCCH to use is greater than the number of UEs <NUM> receiving the PDSCH DL grant on the PDCCH. Therefore, certain PUCCH resources may go unutilized. In particular, if there are Y UEs <NUM> receiving DL grant, and they can be mapped to either long or short part, then there are Y*<NUM> possible PUCCH resources the DL grant could map to for transmitting ACK to avoid collisions. However, only Y of such PUCCH resources may actually be utilized for ACK. Accordingly, in certain aspects, unused PUCCH resources may be reassigned to other UEs or even channels to carry other information (e.g., explicit PUCCH resource mapping, other signaling, other control information, other data, etc.).

In certain aspects, a UE <NUM> may utilize slot aggregation. For example, a UE <NUM> with poor signal quality with BS <NUM> (e.g., at the cell edge) may need to utilize multiple slots to transmit an ACK (e.g., transmit multiple times) in order to successfully transmit the ACK to BS <NUM>.

<FIG> illustrates an example mapping of PDCCH 1201a and 1201b resources to PUCCH 1211a and PUCCH 1211b resources. As shown, PDCCH 1201a is transmitted at a first DL time slot and includes a first DL grant <NUM> transmitted in one or more CCEs having a first starting CCE index. PDCCH 1201b is transmitted at a second DL time slot and includes a second DL grant <NUM> transmitted in one or more CCEs having the first starting CCE index. As shown, based on the first starting CCE index associated with the first DL grant <NUM>, a first PUCCH resource 1212a in PUCCH 1211a of a first UL time slot is mapped by the UE <NUM> to transmit ACK. Since UE <NUM> may have poor signal quality, it may further use slot aggregation and based on the first starting CCE index associated with the first DL grant <NUM>, also map a second PUCCH resource 1212b in PUCCH 1211b of a second UL time slot to transmit ACK. However, based on the first starting CCE index associated with the second DL grant <NUM>, another UE <NUM> may map the second PUCCH resource 1212b in PUCCH 1211b of the second UL time slot to transmit ACK. Therefore, there may be a collision.

Accordingly, in certain aspects, BS <NUM> may not utilize the same starting CCE index to transmit a DL grant for a second UE <NUM> in a second PDCCH slot (e.g., PDCCH 1201b) that is already used to transmit a DL grant for a first UE <NUM> in a first PDCCH slot (PDCCH 1201a) where the first UE <NUM> utilizes slot aggregation. The first and second PDCCH slots may be adjacent and ordered in time. For example, the BS <NUM> may assume a virtual PDCCH is present at the starting CCE index of the second PDCCH slot. Therefore, a different starting CCE index is utilized for the DL grant for the second UE <NUM> in the second PDCCH slot, which maps to a different PUCCH resource, thereby avoiding collision.

In certain aspects, avoiding certain CCE indexes in PDCCH for transmitting DL grant may increase a blocking rate for PDCCH, meaning those CCE resources cannot be used for transmitting DL grant, potentially underutilizing resources. Accordingly, in certain aspects, the CCE indexes not used may be used to carry other information and/or channels (e.g., UL grant for PUSCH and/or PUCCH, DL grant with explicit scheduling of ACK, etc.).

In certain aspects, any combination of the discussed mapping techniques may be used. In certain aspects, implicit mapping may only be used in some cases, and explicit scheduling of ACK may be used in other cases. For example, if only a single CORESET is used, there is not cross slot scheduling, only short duration or long duration is used for ACK, and/or only a single slot is used for transmission of ACK, then explicit scheduling may be used instead of implicit mapping.

<FIG> illustrates example operations that may be performed by a wireless device such as a node such as a base station (BS) (e.g., BS <NUM>) or UE (e.g., UE <NUM>) for mapping PDCCH resources to PUCCH resources for transmission of ACK, in accordance with aspects of the present disclosure.

Operations <NUM> begin, at <NUM>, by determining a resource on a physical uplink control channel (PUCCH) to utilize for communicating an acknowledgement (ACK) for a data transmission on a physical downlink shared channel (PDSCH) based on a control channel element (CCE) index of a first CCE in a physical downlink control channel (PDCCH) that includes a downlink grant for the data transmission on the PDSCH and at least one of: a CORESET index of a CORESET in which the first CCE is included, a slot index of the PUCCH, a slot index of the PDSCH, an offset value between communication of the ACK and the PDSCH, or a mapping of CCE indexes to either a long or short region of the PUCCH.

For example, instructions for perform the operations described herein.

Claim 1:
A method for wireless communication by a wireless device (<NUM>), the method comprising:
determining a number of bits to utilize for communicating an acknowledgement, ACK, for a data transmission on a plurality of physical downlink shared channels PDSCHs, between a base station and a user equipment;
determining a resource on a physical uplink control channel, PUCCH, to utilize for communicating the ACK based on the number of bits, wherein
determining the resource comprises for each PDSCH of the data transmission,
mapping a resource based on a control channel element, CCE index of a first CCE in a physical downlink control channel, PDCCH that includes a downlink, DL, grant for the PDSCH, and at least one of a slot index or time offset value associated with the DL grant,
wherein the slot index is a slot index of the PDCCH including the downlink grant or of the PDSCH of the DL grant and wherein the time offset value is a slot index dependent offset included in downlink control information as part of the downlink grant and indicates the time slot for the PUCCH for communicating the ACK; and
when the total number of bits corresponding to the plurality of PDSCHs is less than or equal to <NUM>, selecting a single resource from the plurality of mapped resources; and
communicating the ACK on the selected single resource.