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>th generation (<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, eNB, 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).

However, as the demand for mobile broadband access continues to increase, there exists a desire for further improvements in NR technology.

<CIT> describes a method for reducing latency in a LTE network by scheduling short TTI resources. PHR is transmitted periodically or may be triggered.

Certain aspects provide a method for wireless communications by a User Equipment (UE) according to claim <NUM>, and an apparatus according to claim <NUM>.

Certain aspects provide a method for wireless communications by a network entity according to claim <NUM> and an apparatus according to claim <NUM>.

Further aspects are provided according to the dependent claims.

3GPP wireless communication standards (e.g., RAN <NUM> specification) have proposed TTIs with shorter durations (e.g., shortened TTIs (sTTI) for low latency communication.

A base station may transmit to one or more UEs using a transmission time interval (TTI) that is reduced in length. Such a TTI may be referred to as a shortened TTI (sTTI) and a user receiving a sTTI may be a low latency user. A sTTI may be divided into a number of resource blocks across a system bandwidth, and each of the resource blocks may be allocated to a UE by a base station. The base station may transmit control information or a control message in a first portion (e.g., control region) of a resource block to provide resource allocations. A low latency user may attempt to decode the control information in the resource block to determine a data region allocated within the same sTTI.

In certain aspects, shortened transmission time intervals (sTTIs) of <NUM> symbol duration may be needed in order to support Ultra-Reliable and Low-Latency Communications (URLLC). URLLC requires sending a <NUM> byte packet with less than <NUM>-<NUM> transmission error rate and with less than <NUM> delay. A one-symbol sTTI may meet this requirement as it may allow for up to three transmission attempts within <NUM> assuming a HARQ turnaround time of <NUM> symbols and assuming immediate, back to back transmission attempts.

However, current standards (e.g., RAN <NUM> specification) proposals are for sTTI of <NUM> symbols duration and <NUM> slot, which supports ULLC requirements. In certain aspects, standardizing one symbol sTTI as a standalone mode may require considerable design effort and changes and may further increase complexity of the base station scheduler and UE receiver. Thus, there is a need to modify current sPDCCH channel proposal such that it enables one-symbol sTTI transmissions with minimal changes to the current sTTI configuration and signaling overhead.

Certain aspects of the present disclosure discuss various techniques to enable <NUM>- symbol sTTI operation within the current <NUM>-symbol and <NUM> slot sTTI design by using, at least in part, <NUM>-symbol sTTI configuration. In certain aspects, the modified <NUM>-symbol sTTI design for enabling <NUM>-symbol sTTI operation meets most of the design and performance goals discussed later in this specification.

NR 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>), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low latency communications (URLLC).

<FIG> illustrates an example wireless network <NUM>, such as a new radio (NR) or <NUM> network, in which aspects of the present disclosure may be performed.

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 eNB, Node B, <NUM> NB, AP, NR BS, NR BS, or TRP may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in the wireless 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 network controller <NUM> may be coupled to a set of BSs and provide coordination and control for these BSs. 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.

OFDM and SC-FDM partition the system bandwidth (e.g., system frequency band) into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. For example, the spacing of the subcarriers may be <NUM> and the minimum resource allocation (called a 'resource block') may be <NUM> subcarriers (or <NUM>). 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 CP on the uplink and downlink and include support for half-duplex operation using time division duplex (TDD). A single component carrier bandwidth of <NUM> may be supported. NR resource blocks may span <NUM> sub-carriers with a sub-carrier bandwidth of <NUM> over a <NUM> duration. Each radio frame may consist 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 CUs and/or DUs.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., eNB, <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 cell (ACells) or data only cells (DCells). For example, the RAN (e.g., a central unit or distributed unit) 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-in some case 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.

<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. 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>, 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 described herein and illustrated with reference to FIGs. <NUM>-<NUM>.

At the base station <NUM>, a transmit processor <NUM> may receive data from a data source <NUM> and control information from a controller/processor <NUM>. 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. For example, the TX MIMO processor <NUM> may perform certain aspects described herein for RS multiplexing.

For example, MIMO detector <NUM> may provide detected RS transmitted using techniques described herein. According to one or more cases, CoMP aspects can include providing the antennas, as well as some Tx/Rx functionalities, such that they reside in distributed units. For example, some Tx/Rx processings can be done in the central unit, while other processing can be done at the distributed units. For example, in accordance with one or more aspects as shown in the diagram, the BS mod/demod <NUM> may be in the distributed units.

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

The DL-centric subframe 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 <NUM> showing an example of an UL-centric subframe. The UL -centric subframe 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 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. The UL data 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 DL control channel (PDCCH).

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 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.

A control region may be located at the beginning of a resource block, and a UE may receive and decode the control information transmitted in the control region to determine that the data region of the resource block has been allocated for that UE. Mechanisms for efficient reception and decoding of this control information is desired. In addition, the mechanisms for reducing the size of the control region, and/or otherwise maximizing the size of the data region of the resource block relative to the control region, or even eliminating one or more of the control regions from one or more of the resource blocks of the sTTI to minimize the impact of control overhead are desired.

In certain aspects, a downlink grant may be transmitted at the beginning of a control message in a control region of a sTTI, and uplink grants may be transmitted at the end of the control region. A configuration that anchors the downlink grant at the beginning of the control region, and anchors the one or more uplink grants, if any, at the end of the downlink control message, may reduce the number of blind decodes that a receiving UE needs to perform, and/or allow for the processing of the downlink grant to begin prior to the UE completing searching for uplink grants. Thus, processing time and latency may be optimized. In addition, in some cases, one or more bits may be added (e.g., to an information field) to a downlink grant to indicate a position within the control region of a sTTI for the start of the uplink grants. This indication may allow for a number of different aggregation levels to be used, while allowing for unused portions of the control region to be reallocated as part of the data region.

In certain aspects, a sTTI may include a number of resource blocks, each of which may be assigned to a low latency user. In some cases, a downlink grant, which may be included in a control message in a control region at the beginning of a resource block, may be used to indicate the allocation of the data region of that resource block to a particular user. A number of bits corresponding to the number of other resource blocks (e.g., the total number of resource blocks of the sTTI minus one) may be added to the downlink grant to indicate whether the downlink grant may also be subsequent resource blocks in the sTTI. As such, control channel overhead may be reduced by reducing a total number of downlink grants, resulting in only a minor change in the total size of each downlink grant.

In certain aspects, a base station (e.g., base station <NUM> of <FIG>) may transmit resource allocations and other control information in one or more shortened PDCCH (sPDCCH) transmissions to the UE (e.g., UE <NUM> of <FIG>). The resource allocations may include one or both of downlink grants and uplink grants of resources for transmission of downlink data (e.g., in a shortened PDSCH, sPDSCH) and uplink data (e.g., in a shortened PUSCH, sPUSCH) respectively for the UE <NUM>.

A sTTI for low latency communications may have multiple resource blocks, which may span the whole system bandwidth or a portion of the system bandwidth. The resource blocks may have the same or different sizes in frequency domain. Each resource block may be allocated for a single user or multiple users. The users may access one, multiple, or all of the resource blocks of the sTTI, depending on their configuration. The resource block structure used may be defined by higher level signaling, for example, for a semi-static configuration.

A resource block in a sTTI may have a sPDCCH associated with the resource block. The sPDCCH may be embedded in the resource block. The sPDCCH may be at the beginning of the resource block (e.g., in the first one or more symbols of the resource block) to enable early decoding of the sPDCCH in the resource block. The sPDCCH may span the bandwidth of the resource block, or may occupy less than the full bandwidth of the resource block, with additional signaling included above (e.g., at a higher frequency) and/or below (e.g., at a lower frequency) the resource elements occupied by the sPDCCH in the resource block. In some cases, a sPDCCH may allocate a sPDSCH to a low latency user for a resource block.

In certain aspects, a sPDCCH for one resource block within a sTTI for a user may include a downlink grant for one or more additional resource blocks within the sTTI for the same user. For example, as described above, the sPDCCH may be in the first portion of the sTTI block (e.g., in the first symbol of the sTTI) at a predefined location within the resource block of the sTTI. A low latency user may monitor the control region (e.g., the sPDCCH) for each sTTI resource blocks to determine whether a downlink grant of resources has been sent (e.g., from a serving base station <NUM>) in the sPDCCH to the low latency user. A low latency user may search for both uplink and downlink grants in the sPDCCH.

As described above, a sPDCCH may be positioned at the beginning of a resource block of a sTTI. In addition, a downlink grant of the sPDCCH may be positioned at the beginning of the sPDCCH. By providing the downlink grant for a low latency user in a same position of each sPDCCH, a search space for the low latency user may be reduced. In some examples, if a low latency user searches for a control message (e.g., for a downlink grant of resources) for that user in a sPDCCH, and successfully identifies the presence of a downlink grant, the low latency user may infer that the associated sPDSCH of that resource block is allocated for that low latency user. Thus, the low latency user may efficiently identify the sPDSCH allocated to itself.

In certain aspects, the downlink grant may include one or more bits that point to other resource blocks of the sTTI comprising a sPDSCH, for that same low latency user. In some cases, the one or more bits may include resource assignment information. Each of the one or more bits may indicate whether or not a resource block is allocated for the same low latency user. For example, if a sTTI includes three resource blocks, two downlink grant bits in a sPDSCH of one resource block may be used to indicate whether the downlink grant is for any of the other three resource blocks for the low latency user.

In certain aspects, downlink grants in other resource blocks may be for one or more other low latency users, and may likewise indicate that the sPDSCH in the resource block containing the sPDCCH with the downlink grant is for one or more of the other low latency users, and one or more bits (e.g., two bits for three resource blocks) may be used to indicate whether any of the other resource blocks are for one or more of the other low latency users. The bits may be appropriately indexed and the resource block to which they relate may be based on a position of the resource block in which the one or more bits of the downlink grant appear. The above-described procedure may efficiently indicate downlink grants, at least in part, because a low latency user may only need to perform a blind decode in a fixed position of the sPDCCH within the resource block, and a number of blind decodes used to determine the downlink grant may be limited to a number of resource blocks configured by a base station in the sTTI.

The uplink grants of a sPDCCH RB set already containing a downlink grant may be separated from the downlink grants. For example, the downlink grants may be transmitted at the beginning of the sPDCCH control region, and the uplink grants may be sent at the end of the sPDCCH control region. As used herein, the sPDCCH control region may be a virtual control region, for example meaning that the resource elements of the sPDCCH may not all be adjacent in the time-frequency domain. The downlink and uplink grants of a sPDCCH may be separated at least in part so that the downlink and uplink grant search spaces do not overlap. Providing the downlink grant at a fixed position relative to a boundary of the sPDCCH control region, and uplink grants at a fixed position relative to another boundary of the sPDCCH control region may reduce the number of blind decode attempts for a low latency user. In addition, because a downlink grant may be received at a set or predetermined position that is separated from a search space for the one or more uplink grants, UE <NUM> may begin to decode the downlink grant prior to completing a blind decoding process for the uplink grants. In some cases, downlink grant processing and uplink grant blind decoding may proceed in parallel, thus increasing efficiency by decreasing the amount of time needed for the UE <NUM> to receive and process a sPDCCH.

A position of each of the uplink grants to be transmitted in a sPDCCH may be determined by the base station <NUM> based at least in part on the uplink grant aggregation level. As described above, the base station <NUM> may transmit an indication of the uplink grant aggregation level to a low latency user in a prior grant message. The base station <NUM> may statically define uplink grant locations for each of multiple aggregation levels. In other examples, multiple uplink grant locations may be defined for a particular aggregation level. Multiple uplink grant locations may result in a greater number of blind decoding attempts by the UE <NUM>, since there are an increased number of potential uplink grant locations for the UE <NUM>.

In some examples, the size of the sPDCCH control region may be at least large enough to accommodate a nominal level of grants and aggregation levels without overlap of the downlink grants and uplink grants at the various aggregation levels. As such, a portion of the sPDCCH control region may be unused. The size of the unused portion of the sPDCCH control region may depend on a number of uplink grants and the aggregation level for a particular sPDCCH. This unused sPDCCH control region may be repurposed by including an indication in the downlink grant of the sPDCCH (e.g., a sPDCCH rate matching information field) that indicates the start of the uplink grants in the sPDCCH. The UE <NUM> that holds the downlink grant may rate match the sPDSCH data region around the downlink grant and uplink grants, if any, to use this otherwise unallocated portion of the sPDCCH as an additional portion of the sPDSCH. The size of this indicator may provide the number of available positions to start the uplink grants in the sPDCCH. For example, where the indictor includes three bits, one of eight possible positions for the start of the uplink grants may be indicated.

<FIG> illustrates an example of a resource allocation diagram <NUM> for low latency applications, in accordance with certain aspects of the present disclosure. Resource allocation diagram <NUM> may include sTTI <NUM> occupying a system bandwidth <NUM>. In some cases, the sTTI <NUM> may represent a sTTI within a legacy TTI, or a separate TTI. In some examples, and as may be the case with other sTTIs described here, sTTI <NUM> may be of different durations. For example, in some cases, sTTI <NUM> may be spread over a two symbol periods, or a single slot width associated with a legacy TTI, or another time period. In this example, sTTI <NUM> includes four resource blocks: resource block <NUM> and resource block <NUM> for UE A, and resource block <NUM> and resource block <NUM> for UE B.

A base station (e.g., base station <NUM> of <FIG>) may generate a downlink grant <NUM> to be included in a sPDCCH <NUM>, the control region of resource block <NUM>. In an aspect, for a two symbol sTTI, the control region of a resource block is allocated within the first symbol duration of the sTTI. Further, sPDCCH region within an sTTI resource block is communicated to UEs via RRC signaling. The downlink grant <NUM> may be for sPDSCH <NUM> of the resource block <NUM>. In some cases, the sPDSCH <NUM> may be in a first symbol period of the resource block <NUM>. In some cases, the downlink grant <NUM> may be in a data region of the resource block <NUM>. The downlink grant may also be for a second sPDSCH, sPDSCH <NUM>, in a data region of resource block <NUM> that are also for UE A, to be jointly used to receive data at UE A based on the control information of downlink grant <NUM>.

A base station may also generate a second downlink grant <NUM> to be included in a sPDCCH <NUM>, the control region of resource block <NUM>. The downlink grant <NUM> may be for the sPDSCH <NUM> of the resource block <NUM>, and may also be for the sPDSCH for resource block <NUM>.

For both downlink grants, one or more bits in each of downlink grant <NUM> and downlink grant <NUM> may be generated by a base station to indicate other resource blocks of the sTTI that include a sPDSCH for that same low latency user. In this example, sTTI <NUM> includes four resource blocks. Downlink grant <NUM> for the UE A may thus include three bits to indicate whether the downlink grant <NUM> is for any of the other three resource blocks for the UE A.

In one example, the bits of the indication may make up or be a part of a resource allocation field in the downlink grant <NUM>. In other examples, the bits of the indication may be included at another position in a sPDCCH, such as sPDCCH <NUM>, or elsewhere within the control region of a resource block, such as resource block <NUM>. The first bit of the indication may be associated with resource block <NUM>, the second bit may be associated with resource block <NUM>, and the third bit may be associated with resource block <NUM>. The receiving UEs, UE A and UE B may infer the relationship between the bits and the resource blocks. For example, the first bit may be associated with the first resource block of the sTTI <NUM> that does not contain the downlink grant having the bits of the indication, and so on. In the example shown in resource allocation diagram <NUM> with respect to sTTI <NUM>, in downlink grant <NUM>, the third bit of the indication may identify the fourth resource block <NUM> as for UE A. In downlink grant <NUM>, the second bit of the indication may identify the second resource block <NUM> as for UE B.

The above-described configuration may efficiently indicate downlink grants at least in part because a low latency user may only need to perform a blind decode in a fixed position of the sPDCCH within the resource block, and a number of blind decodes used to determine the downlink grant may be limited to a number of resource blocks configured by a base station (e.g., cell) in the sTTI. Furthermore, the maximum number of bits in the indication of the downlink grant may also be limited to the number of resource blocks of the sTTI minus one.

A Power Headroom (PHR) reporting procedure generally allows a UE to provide a serving eNB with information about the difference between a maximum transmit power and an estimated power needed for a scheduled transmission. For example, a PHR report may indicate a difference between a nominal UE maximum transmit power and the estimated power for an uplink shared channel (UL-SCH) transmission or sounding reference signal (SRS) transmission.

A UE may be configured to perform PHR reporting based on a number of different triggering events. For example, a UE may be triggered to report PHR upon expiration of a periodic timer or if a prohibit timer has expired (meaning PHR reporting is not prohibited) and certain conditions occur (e.g., a change in channel conditions that warrant an updated report).

As described above, shortened transmission time interval TTI (sTTI) lengths may be utilized in various types of deployments. Examples of sTTI lengths include <NUM>-symbol and <NUM>-slot sTTIs for FDD and <NUM>-slot sTTIs for TDD. In such cases, certain UEs may be configured to support both the "legacy" length (<NUM>) TTIs and one or more short TTIs concurrently.

Supporting two different types of TTIs (on the same or adjacent carriers) may present challenges for uplink PHR reporting. For example, because such a UE may be scheduled for uplink transmissions according to both types of TTIs (e.g., legacy and shortened), obtaining accurate PHR reporting for both types of TTIs may be important for a scheduling eNB. Unfortunately, in some cases, certain PHR transmissions may be blocked (cancelled). For example, if a PHR transmission for one type of TTI is scheduled to occur in a manner that collides with a transmission in another type of TTI, the PHR transmission may be dropped. Canceling a PHR transmission in this manner may have an adverse effect on scheduling by an eNB.

Aspects of the present disclosure, however, present various options that may help address challenges faced for PHR reporting for different types of TTIs. The various options may be employed by a UE for PHR reporting, in some cases based on a PHR reporting configuration signaled by a network entity (e.g., an eNB).

<FIG> illustrates example operations <NUM> for performing PHR reporting by a UE that supports different types of TTIs (e.g., <NUM>-symbol or <NUM> symbol sTTIs and <NUM> TTIs), in accordance with certain aspects of the present disclosure.

Operations <NUM> begin, at <NUM>, by receiving scheduling for one or more first uplink transmissions according to a first Transmission Time Interval (TTI) and one or more uplink transmissions according to a second TTI, wherein the second TTI has a shortened duration relative to the first TTI.

At <NUM>, the UE determines a configuration for performing power headroom (PHR) reporting for both the first and second TTIs. At <NUM>, the UE performs PHR reporting according to the determination.

<FIG> illustrates example operations <NUM> that may be performed by a network entity to configure a UE for PHR reporting, in accordance with aspects of the present disclosure. For example, operations <NUM> may be performed by an eNB to configure a UE to perform PHR reporting according to operations <NUM> described above.

Operations <NUM> begin, at <NUM>, by configuring a user equipment (UE) for performing power headroom (PHR) reporting for uplink transmissions according to both first and second transmission time interval (TTIs), wherein the second TTI has a shortened duration relative to the first TTI. At <NUM>, the network entity receives, from the UE, a PHR report according to the configuration.

For illustrative purposes only, the following examples refer to a <NUM> TTI as an example of a "normal" or "legacy" TTI and refer to a <NUM>-symbol or <NUM>-symbol TTI as a shortened TTI. However, it should be understood, however, that the example techniques may be broadly applied to any type of different length TTIs.

The UE is configured to use separate periodic and prohibit timers for PHR reporting that involves different TTIs (e.g., <NUM> and sTTI). The use of separate timers allows for different periodic reporting and/or different triggering events to occur separately for the different types of TTIs.

In some cases, a UE may be configured to trigger sTTI PHR reporting upon RRC configuration of sTTI and activation of sTTI (e.g., activation of a primary or secondary cell that utilizes a shortened TTI). In some cases, a UE may be configured to trigger PHR reporting for a <NUM> TTI if an earlier PHR transmission is dropped due to collision with an sTTI transmission and that PHR report is not transmitted in sTTI. For example, the UE may be configured to wait until a next available transmit opportunity to send the PHR report for the <NUM> TTI.

The UE is configured to stop a prohibit timer for PHR for <NUM>, when an earlier PHR transmission is dropped due to sTTI collision and that PHR is not transmitted in sTTI. In other words, stopping the prohibit timer allows the PHR for the <NUM> (previously dropped) to be subsequently transmitted.

A UE may be configured to use a single or separate media access control (MAC) control elements (CEs) for reporting PHR for different TTIs. For example, a UE may be configured to use an extended PHR report to include power headroom for both <NUM> and sTTI a single MAC CE or separate MAC CEs for each.

Exactly how PHR is computed for a TTI when a PHR transmission for that TTI is dropped may vary. For example, when PHR transmission in <NUM> is cancelled due to collision with sTTI and resent in sTTI, at least two options (applicable to both type <NUM> and type <NUM> PHR) are available. According to a first option, <NUM> PHR is computed (prior to resending) by considering the dropped <NUM> transmission in the computation. According to a second option, the <NUM> PHR is instead computed based on the earlier allocation (as if the transmission was not dropped).

In some cases, PHR reporting for a dropped PHR transmission may be computed based on fixed parameters instead of parameters for the dropped PHR transmission.

In some cases, a UE may be configured to support PHR reporting by giving certain TTIs a higher priority, for example, by the placement of the corresponding MAC CE. For example, if PHR for both <NUM> and sTTI are reported in sTTI, a UE may be configured to give higher priority to the MAC CE which includes sTTI PHR. On the other hand, if PHR for <NUM> and sTTI are reported in <NUM> TTI, the UE may be configured to give higher priority to the MAC CE which includes the <NUM> TTI PHR.

Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more. §<NUM>, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for.

For example, means for transmitting 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 multiplexing, 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>.

Claim 1:
A method for wireless communication by a User Equipment, UE, comprising:
receiving (<NUM>) scheduling for at least one of first uplink transmissions according to a first Transmission Time Interval, TTI, or second uplink transmissions according to a second TTI, wherein the second TTI has a shortened duration relative to the first TTI;
determining (<NUM>) a configuration for performing power headroom, PHR, reporting for the first TTI and for performing PHR reporting for the second TTI, wherein the configuration involves separate periodic and prohibit timers for PHR reporting for the first and second TTIs; and
performing (<NUM>) PHR reporting according to the determination and based on a collision between transmissions scheduled for the first TTI and the second TTI, wherein performing PHR reporting according to the determination comprises:
dropping a PHR transmission for the first TTI due to the collision with transmission for the second TTI;
stopping a prohibit timer for PHR for the first TTI when an earlier PHR transmission for the first TTI is dropped due to the collision with transmission for the second TTI; and
sending the dropped PHR transmission in the second TTI.