Patent Publication Number: US-2023156628-A1

Title: Reporting power headroom information

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to co-pending U.S. patent application Ser. No. 17/461,790 entitled “REPORTING POWER HEADROOM INFORMATION” and filed on Aug. 30, 2021 for Joachim Loehr, Alexander Johann Maria Golitschek Edler von Elbwart, Hossein Bagheri, Prateek Basu Mallick, Ravi Kuchibhotla, and Vijay Nangia, which is incorporated herein by reference. U.S. application Ser. No. 17/461,790 claims priority to U.S. patent application Ser. No. 16/271,685—now issued as U.S. Pat. No. 11,109,326—entitled “REPORTING POWER HEADROOM INFORMATION” and filed on Feb. 8, 2019 for Joachim Loehr, Alexander Johann Maria Golitschek Edler von Elbwart, Hossein Bagheri, Prateek Basu Mallick, Ravi Kuchibhotla, and Vijay Nangia, which is incorporated herein by reference. U.S. application Ser. No. 16/271,685 claims priority to U.S. Provisional Patent Application No. 62/628,241 entitled “PHR PROCEDURE WHEN AGGREGATING CARRIERS CONFIGURED WITH DIFFERENT TTI LENGTHS” and filed on Feb. 8, 2018 for Joachim Loehr, Alexander Johann Maria Golitschek Edler von Elbwart, Hossein Bagheri, Prateek Basu Mallick, Ravi Kuchibhotla, and Vijay Nangia, which is incorporated herein by reference. 
    
    
     FIELD 
     The subject matter disclosed herein relates generally to wireless communications and more particularly relates to reporting power headroom information. 
     BACKGROUND 
     In certain wireless communications networks, such as Long Term Evolution (“LTE”), a User Equipment (“UE”) reports extended power headroom report (“PHR”) or carrier aggregation, i.e., it reports power headroom (“PH”) info for each activated serving cell together with P C MAX, the total maximum UE transmit power. Because the subframe/TTI length is in LTE same for all carriers the PHR reporting subframes, the subframes to which the power headroom information refers are aligned. However, some wireless communication networks, such as the Third Generation Partnership Project (“3GPP”) Fifth Generation (“5G”) New Radio (“NR”), support carriers with different Orthogonal Frequency Division Multiplexing (“OFDM”) numerologies and/or different Transmission Time Intervals (“TTIs”). 
     BRIEF SUMMARY 
     Methods for reporting power headroom information are disclosed. Apparatuses and systems also perform the functions of the methods. The methods may also be embodied in one or more computer program products comprising executable code. 
     One method of a UE for reporting power headroom information includes being configured with a first serving cell having a first TTI length and a second serving cell having a second TTI length, wherein the second TTI length is smaller than the first TTI length and having an uplink resource allocation for a first TTI on the first serving cell, wherein the first TTI overlaps in time with multiple second TTIs on the second serving cell. The third method includes calculating PH information for the second serving cell for a third TTI associated with a third TTI length that contains the first TTI on the first serving cell and transmitting the PH information in an uplink transmission on the first TTI on the first serving cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only some embodiments and are not therefore to be considered to be limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
         FIG.  1    is a schematic block diagram illustrating one embodiment of a wireless communication system for reporting power headroom information; 
         FIG.  2    is a block diagram illustrating one embodiment of a Radio Access Network (“RAN”) for reporting power headroom information; 
         FIG.  3    is a block diagram illustrating another embodiment of a RAN for reporting power headroom information; 
         FIG.  4    is a schematic block diagram illustrating one embodiment of an apparatus that may be used for reporting power headroom information; 
         FIG.  5    is a block diagram illustrating a first embodiment of a scenario where a UE aggregates carriers configured with different transmission duration unit (“TDU”) lengths; 
         FIG.  6    is a block diagram illustrating a second embodiment of a scenario where a UE aggregates carriers configured with different TDU lengths; 
         FIG.  7    is a block diagram illustrating a third embodiment of a scenario where a UE aggregates carriers configured with different TDU lengths; 
         FIG.  8    is a block diagram illustrating a fourth embodiment of a scenario where a UE aggregates carriers configured with different TDU lengths; 
         FIG.  9    is a block diagram illustrating a fifth embodiment of a scenario where a UE aggregates carriers configured with different TDU lengths; 
         FIG.  10    is a block diagram illustrating a sixth embodiment of a scenario where a UE aggregates carriers configured with different TDU lengths; 
         FIG.  11    is a flow chart diagram illustrating a first method of reporting power headroom information; 
         FIG.  12    is a flow chart diagram illustrating a second method of reporting power headroom information; and 
         FIG.  13    is a flow chart diagram illustrating a third method of reporting power headroom information. 
     
    
    
     DETAILED DESCRIPTION 
     As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine readable code, computer readable code, and/or program code, referred hereafter as code. The storage devices may be tangible, non-transitory, and/or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code. 
     Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing the code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. 
     More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (“RAM”), a read-only memory (“ROM”), an erasable programmable read-only memory (“EPROM” or Flash memory), a portable compact disc read-only memory (“CD-ROM”), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an object-oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the “C” programming language, or the like, and/or machine languages such as assembly languages. The code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (“LAN”) or a wide area network (“WAN”), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. 
     Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment. 
     Aspects of the embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by code. The code may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. 
     The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. 
     The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods, and program products according to various embodiments. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function(s). 
     It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated Figures. 
     Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and code. 
     The description of elements in each figure may refer to elements of proceeding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements. 
     Generally, the present disclosure describes systems, methods, and apparatus for reporting power headroom information when UE is configured with multiple uplink carriers, e.g., in a carrier aggregation deployment, respectively serving cells, for example by a UE communicating with a radio network using a first uplink (“UL”) carrier and a second UL carrier concurrently. 
     In various embodiments, the UE receives an UL resource allocation for a first transmission duration unit on the first UL carrier. Here, the first transmission duration unit overlaps in time with at least two second transmission duration units on the second UL carrier. The UE identifies a third transmission duration unit on the second UL carrier. Here, the third transmission duration unit comprises at least one of the second transmission duration units. The UE calculates PH information for the second UL carrier associated with the third transmission duration unit and reports the PH information in an UL transmission on the first transmission duration unit. 
     In some embodiments, each of the first and second UL carriers is associated with a different serving cell. In some embodiments, the UE may receive an UL resource allocation for at least one of the overlapping second transmission duration units on the second UL carrier. 
     In some embodiments, the first transmission duration unit corresponds to a slot on the first UL carrier and the second transmission duration unit corresponds to a slot on the second UL carrier. For example, the base unit may be a Next Generation (e.g., 5G) Node-B (“gNB”) in a 5G RAN, where the first UL carrier is configured with a first subcarrier spacing (“SCS”) and the second UL carrier is configured with a second SCS, the first SCS being smaller than the second SCS. Accordingly, the first UL carrier will have slots with longer time-duration than the second UL carrier, such that multiple second slots on the second UL carrier fully overlap with the first slot. 
     In such embodiments, the UE calculates PH information for a first physical uplink shared channel (“PUSCH”) scheduled on the first of the multiple second slots that fully overlaps with the first slot on the first UL carrier. Here, reporting PH information for the second UL carrier in an UL transmission on the first slot may include the UE transmitting on a PUSCH transmission a PHR that contains the PH information for the first PUSCH. In certain embodiments, 
     In some embodiments, the first transmission duration unit corresponds to a transmit time interval (“TTI”) of the first UL carrier and the second transmission duration unit corresponds to a TTI of the second UL carrier. In certain embodiments, the first UL carrier is configured with a first TTI length and the second UL carrier is configured with a second TTI length, wherein the first TTI length is larger than the second TTI length. For example, the base unit may be an LTE Evolved Node B (“eNB”), wherein the second TTI length corresponds to a shortened TTI (“sTTI”) length. Moreover, the first TTI length may also correspond to a sTTI. 
     In such embodiments, calculating PH information for the second UL carrier associated with the third transmission duration unit comprises the UE calculating PH for a TTI duration longer than the second TTI length. In certain embodiments, the length of the third transmission duration unit (e.g., third TTI) is greater than the length of the first TTI. In certain embodiments, the third transmission duration unit (e.g., third TTI) is equal to a subframe. In certain embodiments, calculating PH information for the second UL carrier associated with the third transmission duration unit comprises calculating PH information for a subframe containing the first TTI. In certain embodiments, the third transmission duration unit contains multiple TTIs of the second UL carrier (e.g., the third TTI overlaps multiple sTTIs on the second UL carrier). 
     In some embodiments, the UE calculates the PH information according to a predefined reference format. In certain embodiments, the processor calculates the PH information assuming the apparatus is not scheduled to transmit a PUSCH transmission in the third transmission duration unit. 
     In various embodiments, the reported PH information comprises a power headroom level computed based on the UL resource allocation. In some embodiments, TTIs of the second UL carrier are configured with a smaller TTI length than TTIs of the first UL carrier, wherein the at least one second TTI on the second UL carrier has a shortened TTI length that is less than 1 millisecond. In some embodiments, the PH information is calculated based on an uplink resource allocation received for the third transmission duration unit. In such embodiments, the uplink transmission on the third transmission duration may be either stopped or dropped. 
       FIG.  1    depicts a wireless communication system  100  for receiving system information at a UE, according to embodiments of the disclosure. In one embodiment, the wireless communication system  100  includes at least one remote unit  105 , a radio access network (“RAN”)  120 , and a mobile core network  140 . The RAN  120  and the mobile core network  140  form a mobile communication network. The RAN  120  may be composed of a base unit  110  with which the remote unit  105  communicates using wireless communication links  115 . Even though a specific number of remote units  105 , base units  110 , wireless communication links  115 , RANs  120 , and mobile core networks  140  are depicted in  FIG.  1   , one of skill in the art will recognize that any number of remote units  105 , base units  110 , wireless communication links  115 , RANs  120 , and mobile core networks  140  may be included in the wireless communication system  100 . 
     In one implementation, the wireless communication system  100  is compliant with the 5G system specified in the 3GPP specifications. More generally, however, the wireless communication system  100  may implement some other open or proprietary communication network, for example, LTE or Worldwide Interoperability for Microwave Access (“WiMAX”), among other networks. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. 
     In one embodiment, the remote units  105  may include computing devices, such as desktop computers, laptop computers, personal digital assistants (“PDAs”), tablet computers, smart phones, smart televisions (e.g., televisions connected to the Internet), smart appliances (e.g., appliances connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, modems), or the like. In some embodiments, the remote units  105  include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, the remote units  105  may be referred to as the UEs, subscriber units, mobiles, mobile stations, users, terminals, mobile terminals, fixed terminals, subscriber stations, user terminals, wireless transmit/receive unit (“WTRU”), a device, or by other terminology used in the art. 
     The remote units  105  may communicate directly with one or more of the base units  110  in the RAN  120  via UL and downlink (“DL”) communication signals. Furthermore, the UL and DL communication signals may be carried over the wireless communication links  115 . Here, the RAN  120  is an intermediate network that provides the remote units  105  with access to the mobile core network  140 . 
     In some embodiments, the remote units  105  communicate with an application server  151  via a network connection with the mobile core network  140 . For example, an application  107  (e.g., web browser, media client, telephone/VoIP application) in a remote unit  105  may trigger the remote unit  105  to establish a Protocol Data Unit (“PDU”) session (or other data connection) with the mobile core network  140  via the RAN  120 . The mobile core network  140  then relays traffic between the remote unit  105  and the application server  151  in the packet data network  150  using the PDU session. Note that the remote unit  105  may establish one or more PDU sessions (or other data connections) with the mobile core network  140 . As such, the remote unit  105  may concurrently have at least one PDU session for communicating with the packet data network  150  and at least one PDU session for communicating with another data network (not shown). 
     The base units  110  may be distributed over a geographic region. In certain embodiments, a base unit  110  may also be referred to as an access terminal, an access point, a base, a base station, a Node-B, an eNB, a gNB, a Home Node-B, a relay node, or by any other terminology used in the art. The base units  110  are generally part of a radio access network (“RAN”), such as the RAN  120 , that may include one or more controllers communicably coupled to one or more corresponding base units  110 . These and other elements of radio access network are not illustrated but are well known generally by those having ordinary skill in the art. The base units  110  connect to the mobile core network  140  via the RAN  120 . 
     The base units  110  may serve a number of remote units  105  within a serving area, for example, a cell or a cell sector, via a wireless communication link  115 . The base units  110  may communicate directly with one or more of the remote units  105  via communication signals. Generally, the base units  110  transmit DL communication signals to serve the remote units  105  in the time, frequency, and/or spatial domain. Furthermore, the DL communication signals may be carried over the wireless communication links  115 . The wireless communication links  115  may be any suitable carrier in licensed or unlicensed radio spectrum. The wireless communication links  115  facilitate communication between one or more of the remote units  105  and/or one or more of the base units  110 . 
     In one embodiment, the mobile core network  140  is a 5G core network (“5GC”) or the evolved packet core network (“EPC”), which may be coupled to a packet data network  150 , like the Internet and private data networks, among other data networks. A remote unit  105  may have a subscription or other account with the mobile core network  140 . Each mobile core network  140  belongs to a single public land mobile network (“PLMN”). The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. 
     The mobile core network  140  includes several network functions (“NFs”). As depicted, the mobile core network  140  includes multiple user plane functions (“UPFs”)  145 . The mobile core network  140  also includes multiple control plane functions including, but not limited to, an Access and Mobility Management Function (“AW”)  141  that serves the RAN  120 , a Session Management Function (“SMF”)  143 , and a Policy Control Function (“PCF”)  147 . In certain embodiments, the mobile core network  140  may also include an Authentication Server Function (“AUSF”), a Unified Data Management function (“UDM”)  149 , a Network Repository Function (“NRF”) (used by the various NFs to discover and communicate with each other over APIs), or other NFs defined for the 5GC. 
     Although specific numbers and types of network functions are depicted in  FIG.  1   , one of skill in the art will recognize that any number and type of network functions may be included in the mobile core network  140 . Moreover, where the mobile core network  140  is an EPC, the depicted network functions may be replaced with appropriate EPC entities, such as a Mobility Management Entity (“MIME”), Serving Gateway (“S-GW”), Packet Gateway (“P-GW”), Home Subscriber Server (“HSS”), and the like. In certain embodiments, the mobile core network  140  may include a AAA server. 
     In various embodiments, the mobile core network  140  supports different types of mobile data connections and different types of network slices, wherein each mobile data connection utilizes a specific network slice. Here, a “network slice” refers to a portion of the mobile core network  140  optimized for a certain traffic type or communication service. In certain embodiments, the various network slices may include separate instances of network functions, such as the SMF  143  and UPF  145 . In some embodiments, the different network slices may share some common network functions, such as the AMF  141 . The different network slices are not shown in  FIG.  1    for ease of illustration, but their support is assumed. 
     While  FIG.  1    depicts components of a 5G RAN and a 5G core network, the described embodiments for PHR reporting  125  in a wideband carrier apply to other types of communication networks, including IEEE 802.11 variants, Universal Mobile Telecommunications System (“UMTS”), LTE variants, CDMA2000, Bluetooth, and the like. For example, in an LTE/EPC variant, the AMF  141  may be mapped to an MME, the SMF  143  may be mapped to a control plane portion of a P-GW, the UPF  145  may be mapped to a S-GW and a user plane portion of the P-GW, etc. 
     To assist the base unit  110  to schedule uplink transmission resources to different remote units  105  in an appropriate way, each remote unit  105  reports its available PH to the base unit  110 , e.g., using a power headroom report (“PHR”)  125 . Using a received PHR, the base unit  110  may determine how much more uplink bandwidth per sub-frame a remote unit  105  is capable of using, i.e., how close to its transmission power limits the remote unit  105  is operating. The PH indicates the difference between the maximum UE uplink transmit power and the estimated power for UL-SCH transmission. In various embodiments, the remote unit  105  power headroom (PH) in dB valid for sub-frame “i” is defined by: 
       PH( i )= P   CMAX −{10 log 10 ( M   PUSCH ( i ))+ P   0_PUSCH ( j )+ a ( j )· PL+Δ   TF ( i )+ f ( i )}  Equation 1
 
     Here, P CMAX  is the total maximum UE transmit power and is a value chosen by the user equipment in the given range of P CMAX_L  and P CMAX_H  based on the following constraints: 
         P   CMAX_L   ≤P   CMAX   ≤P   CMAX_H    Equation 2
 
         P   CMAX_L =min( P   EMAX   −ΔT   C   ,P   PowerClass MPR−AMPR−Δ T   C )   Equation 3
 
         P   CMAX_H =min( P   EMAX   ,P   PowerClass )   Equation 4
 
     Here, P EMAX  is a value signaled by the network. The MPR is a power reduction value used to control the Adjacent Channel Leakage Ratio (“ACLR”) associated with the various modulation schemes and the transmission bandwidth. AMPR is the additional maximum power reduction. It is a band specific value and applied by the UE when configured by the network. One example of values for ΔT C , MPR and AMPR may be found in 3GPP TS36.101. 
     In various embodiments, the remote unit  105  sends the PHR  125  as a Medium Access Control (“MAC”) Control Element (“CE”). The base unit  110  may configure parameters to control various triggers for reporting power headroom depending on the system load and the requirements of its scheduling algorithm. 
     In various embodiments, the range of the power headroom report is from +40 to −23 dB. Note that negative part of the range enables the remote unit  105  to signal to the base unit  110  the extent to which it has received an UL grant which would require more transmission power than the remote unit  105  has available. The base unit  110  may then reduce the amount of uplink resources in a subsequent grant (dynamic or semi-static), thus freeing up transmission resources which could be then allocated to other remote units. 
     In various embodiments, the power headroom report  125 , e.g., PHR MAC CE, may only be sent in a sub-frame for which the remote unit  105  has a valid uplink resource, i.e., a PUSCH resource. In general, the PHR  125  relates to the sub-frame in which it is sent and is therefore an estimation or prediction rather than a direct measurement (because the remote unit  105  cannot directly measure its actual transmission power headroom for the subframe in which the report is to be transmitted). 
     In various embodiments, the remote unit  105  is configured for carrier aggregation, wherein the remote unit  105  used at least a first carrier and a second carrier concurrently. Each component carrier (e.g., the first and second carriers) may be associated with a different serving cell. Where the remote unit  105  is configured with multiple concurrent serving cells, the power headroom defined in Equation 1 is calculated and reported for each serving cell/component carrier. For the case of carrier aggregation, the remote unit  105  must consider both the total maximum UE transmit power P CMAX  and a component carrier-specific maximum transmit power P CMAX,c . 
     Because simultaneous PUSCH and Physical Uplink Control Channel (“PUCCH”) transmission is supported in carrier aggregation, two different types of PH types are supported for CA. PH type 1 indicates the difference between P CMAX,c  and estimated PUSCH power, while PH type 2 indicates the difference between P CMAX,c  and estimated power of PUSCH and PUCCH combined. Note that PH type 2 is only applicable for Primary Cell (“PCell”), whereas PH type 1 is applicable for both PCell and Secondary Cell (“SCell”). Because it is beneficial for the base unit  110  to always know the power situation for all activated uplink carrier/serving carrier for future uplink scheduling, the remote unit  105  may transmit an extended PH MAC CE on one of the serving cells (PCell and one or more SCells) which has a valid uplink resource for PUSCH. The extended PH MAC CE includes power headroom information (Type1/Type2) for each activated uplink component carrier. 
     While the following solutions are discussed in the context of carrier aggregation, the principles described herein are also applicable to Dual connectivity (DC) which allows a remote unit  105  to receive data simultaneously from different base units  110  in order to boost the performance in a heterogeneous network with dedicated carrier deployment. In Dual Connectivity when a PHR has been triggered, the UE sends power headroom information for all activated cells (including serving cells of both cell groups) to the eNB. When UE reports PH info of secondary cell group (“SCG”) cells to the main base unit  110  (e.g., main eNB (“MeNB”)) or PH info of main/master cell group (“MCG”) cells to the secondary base unit  110  (e.g., secondary eNB (“SeNB”)), Type2 PH information for the PUCCH cell (PUCCH for the SCG) is included. Power headroom info for the serving cells in the other CG may be calculated based on some reference format (e.g., virtual PHR) or based on actual PUSCH/PUCCH transmissions. 
     In various embodiments, the remote unit  105  may be configured with a Short Processing Time (SPT) and a shorter TTI length. Short Transmission Time Interval (Short TTI) provides support for TTI length shorter than 1 ms DL-SCH and UL-SCH. To support the short TTI, the associated control channels, shortened Physical Downlink Control Channel (“sPDCCH,” containing downlink control information for short TTI operation, referred to as “sDCI”) and shortened Physical Uplink Control Channel (“sPUCCH”) are also transmitted with duration shorter than 1 ms. Over the physical layer, DL and UL transmissions use either slots or subslots when short TTI is configured. Recall that in LTE there are 2 slots of 7 OFDM (or Single Carrier Frequency Division Multiple Access (“SC-FDMA”)) symbol duration in a subframe. As used herein, a “subslot” refers to a transmission duration unit of either 2 OFDM/SC-FDMA symbol or 3 OFDM/SC-FDMA symbol duration. As such, three “subslots” fit within a slot. To support the short TTI, the remote unit  105  transmits slot-based (or subslot-based) PUSCH (also referred to as shortened PUSCH or “sPUSCH”). 
     In various embodiments, the RAN  120  may support different OFDM numerologies, i.e., sub-carrier spacing (“SCS”), Cyclic Prefix (“CP”) length, in a single framework, e.g., to support use cases/deployment scenarios with diverse requirements in terms of data rates, latency, and coverage. For example, Enhanced Mobile Broadband (“eMBB”) is to support peak data rates (e.g., 20 Gbps for downlink and 10 Gbps for uplink) while Ultra-reliability and Low-latency Communications (“URLLC”) is to support ultra-low latency (0.5 ms for UL and DL each for user plane latency) and high reliability (1-10-5 within 1 ms). Therefore, the OFDM numerology that is suitable for one use case might not work well for another. Note that different OFDM numerologies have different subcarrier spacings, affecting OFDM symbol duration, CP duration, and number of symbols per scheduling interval. Different numerologies may occur across different carrier(s) for a given UE as well as different numerologies within the same carrier for a given UE, i.e., different OFDM numerologies are multiplexed in frequency-domain and/or time-domain within the same carrier or across different carriers. 
     When carrier aggregation is combined with different numerologies for NR (e.g., 5G radio access) or, for LTE, with shortened TTI, one TDU (e.g., NR slot or LTE TTI) of a carrier can overlap (coincide) with multiple TDUs of another carrier. In this case the base unit  110 , may not be aware which TDU the power headroom information refers to. For example, in a scenario where an extended PHR report is triggered and subsequently transmitted in a slot/TTI, which overlaps with multiple slots/TTIs on a different carrier, the base unit  110  does not know which of the overlapped slot/TTI from the multiple slots/TTIs is the reference for the PH calculation. Without knowledge of the reference TDU, the base unit  110  may establish its future scheduling decisions on wrong assumptions, i.e., how close the UE is operating on the power limit, which may lead to either power scaling or under-utilization of resources. Note that data transmissions may be scheduled to span one or multiple UL TDUs (e.g., slots/TTIs). Similarly, multiple data transmissions (e.g., PUSCH transmissions) also may be scheduled within one slot, which is also referred to as, e.g., sub-slot as outlined below. 
     In various embodiments, the remote unit  105  is configured with different UL TDU lengths for different serving cells, e.g., for a carrier aggregation. With possible simultaneous UL transmissions using different PUSCH durations across serving cells, a base unit  110 , e.g., gNB or eNB, needs to know which TDU a power headroom calculation is based on, so that it correctly interprets a received PHR and to enable the base unit  110  to schedule subsequent transmissions (e.g., sTTI/TTI/slot) properly. As discussed above, the PHR provides the base unit  110  with information on path loss, TPC status and the used MPR for the corresponding uplink transmission. 
     In certain embodiments, the remote unit  105  may receive indications from the base unit  110  of sets of frequency domain resource blocks for possible PUSCH data transmission in uplink of a first TDU length on a first component carrier and a second TDU length on the second component carrier. In one embodiment, the remote unit  105 , having been allocated resources for PUSCH on the first carrier, then identifies a TDU on the second carrier computes a PHR for the second carrier based on the identified TDU. In certain embodiments, the remote unit  105  may derive (and indicate to the base unit  110 ) a reference TDU index (e.g., slot index or TTI index) associated with the PHR for the second carrier. The remote unit  105  transmits the PHR for the second carrier to the base unit  110 . 
       FIG.  2    depicts an access network  200  for reporting power headroom information, according to embodiments of the disclosure. The access network  200  include a UE  205  that uses two UL carriers concurrently, a first component carrier (“CC 1 ”)  220  and a second component carrier (“CC 2 ”)  230 . In various embodiments, each component carrier is associated with a different serving cell. In the depicted embodiment, the first component carrier  220  and the second component carrier  230  are associated with the same RAN node (“gNB- 1 ”)  210 , e.g., a Carrier Aggregation scenario. Here, the RAN node  210  may be gNB in a 5G-RAN. 
     The first component carrier  220  has transmission duration units of longer length than the second component carrier  230 . In various embodiments, these transmission duration units correspond to slots in NR with the first component carrier being configured with a smaller subcarrier spacing (“SCS”) than the second component carrier. As such, multiple slots on the second component carrier  230  fit within a single slot on the first component carrier  220 . In the depicted embodiment, one slot of the first component carrier  220  overlaps with two slots of the second component carrier  230 . 
     As depicted, the first component carrier  220  includes a first slot  221  (denoted “slot- 0 ”), a second slot  222  (denoted “slot- 1 ”), a third slot  223  (denoted “slot- 2 ”), and a fourth slot  224  (denoted “slot- 3 ”). At the same time, the second component carrier  230  includes a first slot  231  (denoted “slot- 0 ”), a second slot  232  (denoted “slot- 1 ”), a third slot  233  (denoted “slot- 2 ”), a fourth slot  234  (denoted “slot- 3 ”), a fifth slot  235  (denoted “slot- 4 ”), a sixth slot  236  (denoted “slot- 5 ”), a seventh slot  237  (denoted “slot- 6 ”), and an eighth slot  238  (denoted “slot- 7 ”). While the depicted embodiment shows alignment of the slot boundaries, in other embodiments the slot boundaries of the first component carrier  220  do not coincide with slot boundaries of the second component carrier  230 . 
     In the access network  200 , the UE  205  is allocated uplink resources in the slot  223 , denoted “slot- 2 ”, on the first component carrier  220 . Here, the allocated resources may correspond to an active bandwidth part on the first component carrier  220 . Note that the slot  223  overlaps with the slots  235  and  236  on the second component carrier  230 . Here, the UE  205  provides a type1 PHR for slot  223  of the first component carrier  220  in a PUSCH transmission on slot  223 . Moreover, the UE  205  provides a PHR for the first PUSCH, if any, on the first of the multiple slots on the second component carrier  230  (e.g., on an active bandwidth part of the second component carrier  230 ) that fully overlaps with the slot  223 . Here, the slot  235  is the first slot on the second component carrier  230  to fully overlap with the slot  223 . Thus, the UE  205  calculates a PHR (e.g., a type1 PHR) for the slot  235  and sends it to the network in the PUSCH transmission on slot  223  (e.g., sends the PHR  240  over the first component carrier  220 ). 
     In certain embodiments, the slot  235  and slot  236  are scheduled for uplink transmission (e.g., PUSCH). Here, the uplink grants for these slots may include dynamic grants and/or configured (e.g., semi-persistent) grants. In one embodiment, the slots  235  and  236  may be scheduled individually. In another embodiment, the slots  235  and  236  are scheduled via a multi-slot grant. In certain embodiments, the UE  205  computes an “actual” PHR for the second component carrier. As used herein, “actual” PH refers to a power headroom level calculates based on actual transmissions. In contrast, “virtual” PH refers to a power headroom level calculated based on a predefined reference format. 
       FIG.  3    depicts an access network  300  for reporting power headroom information, according to embodiments of the disclosure. The access network  300  includes the UE  205  that uses two UL carriers concurrently, a first component carrier (“CC 1 ”)  320  and a second component carrier (“CC 2 ”). In the depicted embodiment, the first component carrier  320  and the second component carrier  330  are associated with a first RAN node (“eNB- 1 ”)  310 . Here, the RAN node  310  may be eNB in an LTE-RAN. 
     The first component carrier  320  has transmission duration units of longer length than the second component carrier  330 . In various embodiments, these transmission duration units correspond to TTIs, for example short TTIs (sTTIs) in LTE as depicted, with the first component carrier being configured with a longer TTI length than the second component carrier. As such, multiple sTTIs on the second component carrier  330  fit within a single sTTI on the first component carrier  320 . In the depicted embodiment, one sTTI of the first component carrier  320  overlaps with three sTTIs of the second component carrier  330 . Here, the first component carrier is configured with a slot-length TTI (e.g., 7 OFDM symbols in duration) and the second component carrier  330  is configured with subslot-length TTI (e.g., 2 or 3 OFDM symbols in duration; here in a “2-2-3” pattern, such that every three sTTIs add up to 7 OFDM symbols). 
     As depicted, the first component carrier  320  includes a first sTTI  321  (denoted “sTTI- 1 ”), a second sTTI  322  (denoted “sTTI- 2 ”), a third sTTI  323  (denoted “sTTI- 3 ”), and a fourth sTTI  324  (denoted “sTTI- 4 ”). At the same time, the second component carrier  330  includes a first sTTI  331  (denoted “sTTI- 1 ”), a second sTTI  332  (denoted “sTTI- 2 ”), a third sTTI  333  (denoted “sTTI- 3 ”), a fourth sTTI  334  (denoted “sTTI- 4 ”), a fifth sTTI  335  (denoted “sTTI- 5 ”), a sixth sTTI  336  (denoted “sTTI- 6 ”), a seventh sTTI  337  (denoted “sTTI- 7 ”), an eighth sTTI  338  (denoted “sTTI- 8 ”), a ninth sTTI  339  (denoted “sTTI- 9 ”), a tenth sTTI  340  (denoted “sTTI- 10 ”), an eleventh sTTI  341  (denoted “sTTI- 11 ”), and a twelfth sTTI  342  (denoted “sTTI- 12 ”). While the depicted embodiment shows alignment of the sTTI boundaries, in other embodiments the sTTI boundaries of the first component carrier  320  do not coincide with sTTI boundaries of the second component carrier  330 . 
     In the access network  300 , the UE  205  is allocated uplink resources in the sTTI  323 , denoted “sTTI- 3 ”, on the first component carrier  320 . Note that the sTTI  323  overlaps with the sTTIs  337 ,  338  and  339  on the second component carrier  330 . Here, the UE  205  provides a PHR for sTTI  323  of the first component carrier  320  in a PUSCH transmission on sTTI  323 . Moreover, the UE  205  provides a PHR  350  for time duration unit on the second component carrier  330  that is larger than the sTTI length(s) of the second component carrier  330 . In the depicted embodiment, the UE  205  calculates a PHR for a subframe-length TDU on the second component carrier  330 . Here, the UE  205  computes the Power headroom for the subframe  345  on the second component carrier  330  containing the sTTI  323  with the PUSCH allocation on the first component carrier  320 . In other embodiments, the UE  205  calculates a PHR for a slot-length TDU on the second component carrier  330 , denoted as “TTI- 3 ”  347 . 
     In certain embodiments, the sTTIs  337 - 339  are scheduled for uplink transmission (e.g., PUSCH). Here, the uplink grants for these sTTIs may include dynamic grants and/or configured (e.g., semi-persistent) grants. In one embodiment, the sTTIs  337 - 339  may be scheduled individually. In another embodiment, the sTTIs  337 - 339  are scheduled via a multi-sTTI grant. In certain embodiments, the UE  205  computes an “virtual” PHR for the second component carrier. As used herein, “virtual” PH refers to a power headroom level calculated based on a predefined reference format. In other embodiments, the UE  205  may compute an “actual” PHR for the second component carrier. 
       FIG.  4    depicts a user equipment apparatus  400  that may be used for reporting power headroom information, according to embodiments of the disclosure. The user equipment apparatus  400  may be one embodiment of the remote unit  105  and/or the UE  205 , described above. Furthermore, the user equipment apparatus  400  may include a processor  405 , a memory  410 , an input device  415 , an output device  420 , a transceiver  425  for communicating with one or more base units  110 . 
     As depicted, the transceiver  425  may include a transmitter  430  and a receiver  435 . The transceiver  425  may also support one or more network interfaces  440 , such as the Uu interface used to communicate with a gNB, or other suitable interface for communicating with the RAN  120 . In some embodiments, the input device  415  and the output device  420  are combined into a single device, such as a touchscreen. In certain embodiments, the user equipment apparatus  400  may not include any input device  415  and/or output device  420 . 
     In various embodiments, the processor  405  receives (i.e., via the transceiver  425 ) a service configuration for a first serving cell for PUSCH transmissions having a first SCS and a second serving cell for PUSCH transmissions having a second SCS, where the first SCS is smaller than the second SCS. The processor  405  receives (i.e., via the transceiver  425 ) an uplink resource allocation for a first slot on the first serving cell, where the first slot overlaps in time with multiple second slots on the second serving cell. Additionally, the processor receives (i.e., via the transceiver  425 ) an uplink resource allocation for at least one of the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. The processor  405  calculates PH information for the second serving cell for a first PUSCH scheduled on a first slot of the multiple second slots that fully overlaps with the first slot on the first serving cell and controls the transceiver  425  to transmit the PH information in an uplink transmission on the first slot on the first serving cell. 
     In some embodiments, the processor  405  further receives (via the transceiver  425 ) a second uplink resource allocation for at least one of the overlapping second slots on the second uplink carrier. In some embodiments, transmitting the PH information in an uplink transmission on the first slot on the first serving cell includes transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH scheduled on the first of the multiple second slots that is fully overlapped by the first slot. 
     In some embodiments, transmitting the PH information includes transmitting a Type 1 power headroom report. In some embodiments, transmitting the PH information includes transmitting a PHR MAC CE in the uplink transmission in an allocated uplink allocation on the first serving cell. 
     In some embodiments, the first slot corresponds to a TTI of the first serving cell and the second slots correspond to TTIs of the second serving cell. In certain embodiments, the PH information for the second serving cell is calculated for TTI duration that contains multiple TTIs of the second serving cell. 
     In some embodiments, the first serving cell is configured with a first TTI length and the second serving cell is configured with a second TTI length, where the first TTI length is larger than the second TTI length. In certain embodiments, calculating PH information for the second serving cell includes calculating PH information for a subframe that uses the first TTI length. 
     In certain embodiments, calculating PH information for the second serving cell includes calculating PH for a TTI duration longer than the second TTI length. In one embodiment, the PH for the second serving cell is calculated for TTI duration that is greater than the length of the first TTI. In another embodiment, the PH for the second serving cell is calculated for TTI duration that is equal to a subframe. 
     In some embodiments, the PH information is calculated according to a predefined reference format. In certain embodiments, the PH information is calculated assuming the UE is not scheduled to transmit a PUSCH in the at least two second slots that fully overlaps with the first slot. 
     In some embodiments, the at least one of the second slots on the second serving cell has a shortened TTI length that is less than 1 millisecond. In some embodiments, the reported PH information includes a power headroom level computed based on the uplink resource allocation. 
     In some embodiments, the PH information is calculated based on an uplink resource allocation received for a transmission duration corresponding to the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. In certain embodiments, an uplink transmission on the transmission duration is one of: stopped and dropped. 
     In various embodiments, the transceiver  425  communicates with a base unit using a first uplink carrier and a second uplink carrier concurrently. Here, each carrier has a different transmission duration unit length, wherein the first uplink carrier has a longer transmission duration unit length than the second uplink carrier. At some point in time, the processor  405  receives an uplink resource allocation for a first transmission duration unit on the first uplink carrier and determines a third transmission duration unit on the second uplink carrier. Here, the first transmission duration unit overlaps in time with at least two second transmission duration units on the second uplink carrier and the third transmission duration unit comprises at least one of the second transmission duration units. The processor  405  calculates PH information for the second uplink carrier associated with the third transmission duration unit and reports, via the transceiver  425 , the PH information in an uplink transmission on the first transmission duration unit. 
     In some embodiments, each of the first and second uplink carriers is associated with a different serving cell. In some embodiments, the processor further receives an uplink resource allocation for at least one of the overlapping second transmission duration units on the second uplink carrier. 
     In some embodiments, the first transmission duration unit corresponds to a slot on the first uplink carrier and the second transmission duration unit corresponds to a slot on the second uplink carrier. In certain embodiments, multiple second slots on the second uplink carrier fully overlap with the first slot. In such embodiments, the processor  405  calculates PH information for a first physical uplink shared channel (“PUSCH”) scheduled on the first of the multiple second slots that fully overlaps with the first slot on the first uplink carrier, wherein reporting PH information for the second uplink carrier in an uplink transmission on the first slot comprises transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH. In certain embodiments, the first uplink carrier is configured with a first subcarrier spacing (“SCS”) and the second uplink carrier is configured with a second SCS, wherein the first SCS is smaller than the second SCS. 
     In some embodiments, the first transmission duration unit corresponds to a transmit time interval (“TTI”) of the first uplink carrier and the second transmission duration unit corresponds to a TTI of the second uplink carrier. In certain embodiments, the first uplink carrier is configured with a first TTI length and the second uplink carrier is configured with a second TTI length, wherein the first TTI length is larger than the second TTI length. In such embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH for a TTI duration longer than the second TTI length. 
     In certain embodiments, the length of the third transmission duration unit is greater than the length of the first TTI. In certain embodiments, the third transmission duration unit is equal to a subframe. In certain embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH information for a subframe containing the first TTI. In certain embodiments, the third transmission duration unit contains multiple TTIs of the second uplink carrier. 
     In some embodiments, the processor  420  calculates the PH information according to a predefined reference format. In certain embodiments, the processor  420  calculates the PH information assuming the apparatus is not scheduled to transmit a PUSCH in the third transmission duration unit. 
     In various embodiments, the reported PH information comprises a power headroom level computed based on the uplink resource allocation. In some embodiments, the at least one of the second transmission duration units on the second uplink carrier (e.g., second TTI on the second uplink carrier) has a shortened TTI length that is less than 1 millisecond. In some embodiments, the PH information is calculated based on an uplink resource allocation received for the third transmission duration unit. In such embodiments, the uplink transmission on the third transmission duration may be either stopped or dropped. 
     In some embodiments, the transceiver  425  receives a first indication (e.g., first UL resource grant) from a mobile communication network (e.g., from the base unit  110 ) indicating a first set of frequency domain resource blocks for possible PUSCH data transmission and at least one uplink transmission duration unit (“TDU”) of a first TDU length on a first component carrier. The transceiver  425  may also receive a second indication (e.g., second UL resource grant) from the mobile communication network indicating a second set of frequency domain resource blocks for possible PUSCH data transmission and at least one uplink TDU of a second TDU length on the second component carrier. Here, the first component carrier and the second component carrier are configured with different TDU lengths (e.g., different TTI/sTTI lengths in an LTE deployment or different slot lengths in an NR deployment). 
     The processor  405  computes a first PHR based on at least one of: transmissions of the first TDU length only being present in a first TDU on the first carrier, and a reference format. In certain embodiments, the processor  405  may also select at least one second TDU of the second TDU length on the second component carrier and compute a second PHR based on at least one of: transmissions of the second TDU length only being present in the selected second TDU on the second component carrier, and a reference format. Moreover, the processor  405  may derive a reference TDU index associated with the second PHR. 
     The processor  405  controls the transceiver  425  to transmit at least the first PHR and the second PHR to the base unit (e.g., gNB or eNB). Here, the second TDU length is shorter than the first TDU length, such that the first TDU encompasses one or more TDUs of the second TDU length. For example, an integer number of TDUs of the second TTI length may fit within the time duration of the first TDU. 
     In one embodiment, the second indication is a Radio Resource Control (“RRC”) configuration assigning the second set of frequency domain resource blocks for possible PUSCH data transmissions (e.g., a configured UL grant, such as semi-persistent scheduling). Additionally, the RRC configuration may further indicate at least one of the modulation and coding scheme (“MCS”) and a transport block size (“TBS”) index. In such embodiments, the second PHR may contain a power headroom value computed based on transmissions of the second TTI length only being present in the second TTI on the second component carrier. 
     Additionally, in the above embodiments computing the second PHR may be based on the allocation of the second set of frequency domain resource blocks, irrespective of the presence of transmissions in the second TTI on the second component carrier (e.g., the processor  405  calculates the second PHR assuming that PUSCH transmissions will occur on the one or more second TDUs, even if PUSCH is actually not transmitted on the one or more second TDUs). In such embodiments, a configured maximum transmit power value (e.g., P CMAX,c ) may be included in the second PHR. 
     In certain embodiments, the first PHR and at least the second PHR are transmitted via a single PHR MAC control element. In certain embodiments, the reference TDU index is derived based on at least the second TDU index within the first TDU. 
     In some embodiments, the processor  405  selects a second TDU from a set of TDUs of the second TDU length within the first TDU. Here, the processor  405  may select the earliest scheduled TDU of the second TDU length within the first TDU for uplink transmission. In another embodiment, the processor  405  may select the second TDU from the set of TDUs of the second TDU length within the first TDU based on the scheduled TDU of the second TDU length within the first TDU for uplink transmission having a smallest power headroom field value among the scheduled TDU of the second TDU length within the first TDU for uplink transmission. In a third embodiment, the second TDU selected from a set of TDUs of the second TDU length within the first TDU based on the earliest scheduled TDU of the second TDU length within the first TDU for uplink transmission if no PHR is due on any earlier TTI of the second TTI length within the first TDU, and otherwise based on the earliest TDU of the second TDU length within the first TDU for which a PHR is due. 
     In some embodiments, computing the second PHR is based on the reference format (e.g., a virtual PHR). In such embodiments, the second PHR may be computed according to a third TTI with a third TTI length. In one such embodiment, the third TTI length is equal to one subframe (e.g., 1 ms). In an alternate embodiment, the third TTI length is the same as the first TTI length. Also, in such embodiments, uplink transmissions of the third TTI length may not be configured for the second component carrier. Moreover, in these embodiments the transmit power control command value may be a fixed value. Further, the second PHR calculation may be associated with fixed resource block allocation and a transmit power control command value the fixed value of the transmit power control command may be selected based on the third TTI length. In certain embodiments, the first component carrier belongs to the first PUCCH group and the second component carrier belongs to a second PUCCH group. 
     The memory  410 , in one embodiment, is a computer readable storage medium. In some embodiments, the memory  410  includes volatile computer storage media. For example, the memory  410  may include a RAM, including dynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and/or static RAM (“SRAM”). In some embodiments, the memory  410  includes non-volatile computer storage media. For example, the memory  410  may include a hard disk drive, a flash memory, or any other suitable non-volatile computer storage device. In some embodiments, the memory  410  includes both volatile and non-volatile computer storage media. 
     In some embodiments, the memory  410  stores data related to reporting power headroom information. For example, the memory  410  may store one or more power headroom reports, e.g., of the first and second types described herein. Additionally, the memory  410  may store data for reporting power headroom information, such as PH values, resource allocations, TTI index, and the like. In certain embodiments, the memory  410  also stores program code and related data, such as an operating system or other controller algorithms operating on the remote unit  105 . 
     The input device  415 , in one embodiment, may include any known computer input device including a touch panel, a button, a keyboard, a stylus, a microphone, or the like. In some embodiments, the input device  415  may be integrated with the output device  420 , for example, as a touchscreen or similar touch-sensitive display. In some embodiments, the input device  415  includes a touchscreen such that text may be input using a virtual keyboard displayed on the touchscreen and/or by handwriting on the touchscreen. In some embodiments, the input device  415  includes two or more different devices, such as a keyboard and a touch panel. 
     The output device  420 , in one embodiment, is designed to output visual, audible, and/or haptic signals. In some embodiments, the output device  420  includes an electronically controllable display or display device capable of outputting visual data to a user. For example, the output device  420  may include, but is not limited to, an LCD display, an LED display, an OLED display, a projector, or similar display device capable of outputting images, text, or the like to a user. As another, non-limiting, example, the output device  420  may include a wearable display separate from, but communicatively coupled to, the rest of the user equipment apparatus  400 , such as a smart watch, smart glasses, a heads-up display, or the like. Further, the output device  420  may be a component of a smart phone, a personal digital assistant, a television, a table computer, a notebook (laptop) computer, a personal computer, a vehicle dashboard, or the like. 
     In certain embodiments, the output device  420  includes one or more speakers for producing sound. For example, the output device  420  may produce an audible alert or notification (e.g., a beep or chime). In some embodiments, the output device  420  includes one or more haptic devices for producing vibrations, motion, or other haptic feedback. In some embodiments, all or portions of the output device  420  may be integrated with the input device  415 . For example, the input device  415  and output device  420  may form a touchscreen or similar touch-sensitive display. In other embodiments, the output device  420  may be located near the input device  415 . 
     As discussed above, the transceiver  425  communicates with one or more network functions of a mobile communication network via one or more access networks. The transceiver  425  operates under the control of the processor  405  to transmit messages, data, and other signals and also to receive messages, data, and other signals. For example, the processor  405  may selectively activate the transceiver  425  (or portions thereof) at particular times in order to send and receive messages. 
     In various embodiments, the transceiver  425  includes at least one transmitter  430  and at least one receiver  435 . One or more transmitters  430  may be used to provide UL communication signals to a base unit  110 , such as the PUSCH transmissions containing PHR described herein. Similarly, one or more receivers  435  may be used to receive DL communication signals from the base unit  110 , as described herein. Although only one transmitter  430  and one receiver  435  are illustrated, the user equipment apparatus  400  may have any suitable number of transmitters  430  and receivers  435 . Further, the transmitter(s)  425  and the receiver(s)  430  may be any suitable type of transmitters and receivers. In one embodiment, the transceiver  425  includes a first transmitter/receiver pair used to communicate with a mobile communication network over licensed radio spectrum and a second transmitter/receiver pair used to communicate with a mobile communication network over unlicensed radio spectrum. 
     In certain embodiments, the first transmitter/receiver pair used to communicate with a mobile communication network over licensed radio spectrum and the second transmitter/receiver pair used to communicate with a mobile communication network over unlicensed radio spectrum may be combined into a single transceiver unit, for example a single chip performing functions for use with both licensed and unlicensed radio spectrum. In some embodiments, the first transmitter/receiver pair and the second transmitter/receiver pair may share one or more hardware components. For example, certain transceivers  425 , transmitters  430 , and receivers  435  may be implemented as physically separate components that access a shared hardware resource and/or software resource, such as for example, the network interface  440 . 
     In various embodiments, one or more transmitters  430  and/or one or more receivers  435  may be implemented and/or integrated into a single hardware component, such as a multi-transceiver chip, a system-on-a-chip, an application specific integrated circuit (“ASIC”), or other type of hardware component. In certain embodiments, one or more transmitters  430  and/or one or more receivers  435  may be implemented and/or integrated into a multi-chip module. In some embodiments, other components such as the network interface  440  or other hardware components/circuits may be integrated with any number of transmitters  430  and/or receivers  435  into a single chip. In such embodiment, the transmitters  430  and receivers  435  may be logically configured as a transceiver  425  that uses one more common control signals or as modular transmitters  430  and receivers  435  implemented in the same hardware chip or in a multi-chip module. 
       FIG.  5    depicts a first scenario  500  where the UE  205  aggregates serving cells (e.g., in a carrier aggregation deployment) with different TDU lengths, according to various embodiments of the disclosure. Here, the UE aggregates a first component carrier (e.g., “CC 1 ”)  505  and second component carrier (e.g., “CC 2 ”)  510 . In certain embodiments, both CC 1   505  and CC 2   510  are LTE carriers configured with a short TTI of different lengths, i.e., both TTI lengths are shorter than 1 ms. As depicted, one TTI of CC 1   505  overlaps with 3 TTIs of CC 2   510 . As an example, one TTI on CC 1   505  may correspond to an LTE slot (7 OFDM Symbol (“OS”)), whereas an UL transmission on CC 2   510  uses sub-slots (e.g., either two OFDM/SC-FDMA symbols or three OFDM/SC-FDMA symbols in duration). In other embodiments, the CC 1   505  and CC 2   510  are NR carriers configured with different OFDM numerologies, such that multiple NR slots on CC 2   510  overlap with one NR slot on CC 1   505 . 
     In the first scenario  500 , an uplink transmission on (s)PUSCH is scheduled for sTTI- 1  on CC 1   505 . Here, the UE  205  multiplexes a PHR MAC CE in the sPUSCH in sTTI- 1  on CC 1   505 . The UE  205  is further scheduled with an uplink transmission on (s)PUSCH in sTTI- 2  on CC 2   510 . 
     According to one embodiment, the UE  205  reports Power headroom information for sTTI- 2  on CC 2   510  within the PHR MAC CE transmitted in sTTI- 1  on CC 1   505 . Reporting the power headroom information for sTTI- 2  on CC 2  has the advantage that the UE  205  reports an actual PHR, i.e., PHR is reported for a scheduled TTI. The actual PHR provides information on the used MPR for the corresonding uplink transmission to the RAN node. Therefore, for cases when the UE  205  is scheduled for an uplink transmission in one of the overlapped TTIs, the UE  205  may report the actual PH for this scheduled TTI. 
       FIG.  6    depicts a second scenario  600  where the UE  205  aggregates serving cells (e.g., in a carrier aggregation deployment) with different TTI lengths, according to various embodiments of the disclosure. Here, the UE  205  aggregates a first component carrier (e.g., “CC 1 ”)  605  and second component carrier (e.g., “CC 2 ”)  610 . In certain embodiments, both CC 1   505  and CC 2   510  are LTE carriers configured with a short TTI of different lengths, such that one TTI on CC 1  may correspond to an LTE slot, and three TTIs on CC 2  fit within one TTI on CC 1 . In other embodiments, the CC 1   605  and CC 2   610  are NR carriers configured with different OFDM numerologies, such that multiple NR slots on CC 2   610  overlap with one NR slot on CC 1   605 . 
     Note that in the second scenario  600 , the UE is scheduled for sPUSCH on sTTI- 1  of CC 1   605  as well as sTTI- 1  of CC 2   610 . In the second scenario  600 , the UE  205  reports PH information for sTTI- 1  of CC 2  within the PHR MAC CE transmitted on CC 1 . In certain embodiments, when the UE  205  is scheduled for an uplink transmission in one of the overlapped TTIs, the UE  205  reports the power headroom information for this scheduled TTI, unless there is another sTTI having its PHR due before the PHR MAC CE is generated. Thus, in the first scenario  500  shown in  FIG.  5    (e.g., sPUSCH at sTTI- 2  of CC 2  is scheduled with n+8 timing, i.e., 8 subslots before sTTI- 2 ), the UE  205  may report PH information for sTTI- 2  of CC 2  within the PHR MAC CE transmitted on CC 1  when no PHR is due in sTTI- 1  of CC 2  (e.g., due to expiration of periodicPHR-Timer). However, if there is a PHR due in sTTI- 1  of CC 2  then the UE  205  may instead report PH information for sTTI- 1  of CC 2  within the PHR MAC CE transmitted on CC 1  and not that of sTTI- 2  of CC 2 . 
       FIG.  7    depicts a third scenario  700  where a UE aggregates serving cells (e.g., in a carrier aggregation deployment) with different TTI lengths, according to various embodiments of the disclosure. Here, the UE aggregates a first component carrier (e.g., “CC 1 ”)  705  and second component carrier (e.g., “CC 2 ”)  710 . Note that in the third scenario  700 , the UE is scheduled for sPUSCH on sTTI- 1  of CC 1   705  and also on sTTI- 1 , sTTI- 2 , and sTTI- 3  of CC 2   710 . 
     For cases when there is only one of the overlapping TDUs on CC 2  which is scheduled for an uplink transmission, the RAN node is aware for which TDU the UE  205  has reported power headroom information. However, in case several of the overlapping TDUs on CC 2  are scheduled for an uplink transmission, then the RAN node and UE  205  need a common understanding for which of the overlapping TDUs the UE  205  is to report power headroom information. According to one embodiment, the UE  205  reports power headroom information for the first of the overlapping TDUs which are scheduled for an uplink transmission. One example of reporting for the first overlapping TDU is described above with reference to  FIG.  2   . 
     Given the third scenario  700 , where all three overlapping (s)TTIs are scheduled for an uplink transmission, e.g., sPUSCH is scheduled in sTTI- 1  through sTTI- 3  on CC 2  (e.g., via individual UL grants or via multi-TTI UL grant), the UE  205  may report power headroom information for sTTI- 1  of CC 2   710  within the PHR MAC CE transmission on CC 1   705 . In an alternative embodiment the UE  205  reports power headroom information for the last scheduled overlapping sTTI (e.g., sTTI- 3 ). However, since the UL grant timing, i.e., timing between UL grant and corresponding uplink transmission, needs to be also considered, reporting power headroom for the first overlapped TTI may ensure sufficient processing time to calculate the PH information. 
       FIG.  8    depicts a fourth scenario  800  where the UE  205  aggregates serving cells (e.g., in a carrier aggregation deployment) with different TTI lengths, according to various embodiments of the disclosure. In various embodiments, when PHR is due on more than one CC, the UE  205  may report the PH information for the earliest PHR occasion, and the pending PHR corresponding to the longer TTI may be cancelled if a virtual PHR is reported for the CC associated with the longer TTI assuming a shorter TTI length. Here, the UE aggregates a first component carrier (e.g., “CC 1 ”)  805  and second component carrier (e.g., “CC 2 ”)  810 . Note that in the fourth scenario  800 , the UE is scheduled for sPUSCH on sTTI- 1  of CC 1   805 . During the depicted time duration, CC 2   810  includes a TTI (e.g., subframe)-based PUSCH. 
     In the fourth scenario  800 , assume sPUSCH at sTTI- 1  of CC 1   805  is scheduled with n+4 timing, i.e., 4 slots before sTTI- 1 , and subframe-based PUSCH is scheduled with n+3 timing, i.e., 3 subframes before the subframe where PUSCH is transmitted). Here, the UE  205  may report a (e.g., virtual) PHR computed assuming the PHR calculation for the UL sTTI in which the PHR is transmitted (according to 3GPP agreement), and may further cancel the PHR that was due on subframe-length TTI on CC 2   810 . 
       FIG.  9    depicts a fifth scenario  900  where the UE  205  aggregates serving cells (e.g., in a carrier aggregation deployment) with different TTI lengths, according to various embodiments of the disclosure. Apart from the shorter TTI durations introduced for LTE Rel-15 or NR, also the minimum timing from UL grant transmission to UL PUSCH transmission has been reduced. Therefore, the different timing relations, i.e., (s)PDCCH to sPUSCH, also need to be considered when reporting power headroom information. 
     In the fifth scenario  900 , the UE  205  aggregates a first component carrier (e.g., “CC 1 ”)  905  and second component carrier (e.g., “CC 2 ”)  910 . Note that in the fifth scenario  900 , the UE is scheduled for sPUSCH on sTTI- 4  of CC 1   905  and on sTTI- 14  of CC 2   910 . As depicted, the UE  205  is aggregating two serving cells/CCs with different TTI lengths, where one TTI of CC 1  overlaps with three TTIs of CC 2   910 . Also, the timing relations between UL grant and the corresponding UL PUSCH transmission may be different for the two aggregated serving cells. 
     As power headroom is calculated based on a received UL grant, i.e. estimated UL power according to the grant, when configured with different serving cells having different TTI lengths (and potentially also different timing relations, i.e. from UL grant to corresponding UL transmission), when generating the PHR MAC CE the UE  205  may not be aware (e.g., at sTTI- 0  of CC 1   905 ) whether there will be some uplink transmission on the other carriers in any of the TTIs which overlap with the TTI in which PHR MAC CE is transmitted. For example, the UE might not be fast enough to process the UL grant(s) for the overlapping TTIs on the other carriers when calculating the power headroom information. Taking the exemplary scenario depicted in  FIG.  9   , when generating the PHR MAC CE for transmission on CC 1   905  in sTTI- 4 , the UE is not aware of the presence of an UL grant for the overlapping sTTI(s) on CC 2   910 , i.e., sTTI- 13 , sTTI- 14 , and sTTI- 15 . 
     Therefore, the UE  205  may determine whether the power headroom value for an activated Serving Cell is based on real transmission or a reference format by considering the downlink control information which has been received until and including the Physical Downlink Control Channel (“PDCCH”) occasion in which the first UL grant is received since a PHR has been triggered. Here, the UE  205  considers all the UL grants having received until it receives an UL grant allocating UL resource for inclusion of PHR MAC CE. In the example above, the UE  205  considers all UL allocations having been received until and including sTTI- 0  on CC 1  for determining the PHR format. Therefore, the UE  205  reports a virtual PHR for CC 2  since no UL grant information is available for the overlapping sTTIs on CC 2 , i.e., sTTI- 13 , sTTI- 14 , and sTTI- 15 . Because the UE  205  does not have UL grant information for any of the overlapping sTTIs on CC 2 , the UE  205  would report always a virtual PHR for CC 2  regardless of how the reference PHR TTI is defined, i.e., TTI to which a reported PHR refers to. 
     However, considering that the UE  205  might be also configured with UL resources without dynamic scheduling, i.e., Semi-Persistent scheduling (SPS) or configured grants, it is still required to define a reference PHR TTI. 
     Assuming that the UE  205  is allocated configured grants for one or multiple of the overlapping sTTIs on CC 2 , the UE  205  needs to know for which of the overlapping TTI to report power headroom information. It should be noted that the UE  205  may be aware of these configured grants at sTTI- 0  on CC 1  and hence should consider them for PHR reporting. Here, the reference PHR TTI could be, e.g., defined—as outlined in the other embodiment—as the first of the overlapping (s)TTIs which are scheduled for an uplink transmission. Alternatively, the reference PHR TTI, i.e., TTI for which Power headroom level is computed, could be defined as the first overlapped (s)TTI. 
     According to another embodiment, the UE  205  reports a virtual PHR for a carrier/serving cell which has a different TTI length than the serving cell on which PHR MAC CE is transmitted. Taken the examples depicted in the above figures, the PHR MAC CE is transmitted on CC 1  which has a TTI length of, e.g., seven OFDM symbols (OS). As CC 2  is configured 2OS-UL TTI respectively 3OS-UL TTI, the UE will report virtual for CC 2 , i.e., PHR calculation is performed for 7OS-UL TTI and there is no  705 -UL allocation/transmission on CC 2 . 
     Referring back to  FIG.  7   , in some embodiments, the UE  205  reports a virtual power headroom corresponding to a first TTI length (e.g., slot-length TTI) on CC 2  within the PHR MAC CE transmitted in sTTI- 1  on CC 1 , although CC 2  is not configured with the first TTI length (e.g., slot-length TTI), but configured with a second TTI length (e.g., 2/3 OFDM/SC-FDMA symbol duration). 
     To calculate the virtual PHR, the UE  205  assumes a TPC state (e.g., “f” used in the power control formula) corresponding to a third TTI length. In one example, the TPC state may be derived from one or both of the TPC states corresponding to 1 ms and 2/3 symbol sTTI. For example, the third TTI can be: a) fixed/specified to 1 ms TTI, b) fixed/specified to 2/3 symbol-sTTI, c) indicated/configured to one of 1 ms TTI or 2/3 symbol-sTTI, or d) most recently scheduled TTI length on CC 2 . 
     In another embodiment, the UE  205  reports a power headroom for CC 2  corresponding to a TTI length (e.g., 1 ms-length TTI) different than the TTI length configured for CC 2  within the PHR MAC CE transmitted in sTTI- 1  on CC 1 . For example, referring again to  FIG.  3   , the UE  205  may report a virtual power headroom for CC 2  within the PHR MAC CE transmitted in sTTI- 1  on CC 1 , wherein the TTI length that the virtual power headroom for CC 2  is based on is different than the TTI length associated with the sPUSCH transmission on CC 2 . One example of computing a power headroom for a component carrier/serving cell based on a TTI length being different than the TTI length configured for this component carrier/serving cell is described above with reference to  FIG.  3   . 
     According to one embodiment, the UE  205  aggregating multiple serving cells reports an actual PHR for a serving cell/CC according to a configured grant, i.e., UL resources allocated without dynamic scheduling, even though there is no PUSCH transmission in the corresponding TTI on that serving cell. Here, the UE  205  transmits the PHR MAC CE on one of the other activated serving cells on which a PUSCH transmission takes place. 
     For cases when UE  205  has no data available for transmission in its buffer, UE  205  may not perform an uplink transmission on PUSCH even though it has a valid resource allocation, e.g., allocated by a configured grant like SPS scheduling. Because there is no higher layer data available, the UE  205  would otherwise send a MAC PDU which contains only padding bits and potentially padding Buffer Status Report (“BSR”). However, from a power headroom reporting perspective, it will be still useful to send an actual PHR for the serving cell, i.e., Power headroom calculation is based on the uplink resource allocation, even when there is no PUSCH transmission, since the actual PHR provides more information to the RAN node than a virtual PHR. 
     The actual PHR provides for example information on the used MPR for the corresponding uplink allocation, which is not provided by a virtual PHR, i.e., MPR is set to  0 dB for a virtual PHR. Furthermore, the UE  205  might know at a late point of time whether it will skip the uplink transmission or not due to changes in its transmission buffer. 
       FIG.  10    depicts a sixth scenario  1000  where the UE  205  aggregates serving cells (e.g., in a carrier aggregation deployment) with different TTI lengths, according to various embodiments of the disclosure. Here, the UE  205  aggregates a first component carrier (e.g., “CC 1 ”)  1005  and second component carrier (e.g., “CC 2 ”)  1010 . Note that in the sixth scenario  1000 , the UE  205  is scheduled for sPUSCH on sTTI- 4  of CC 1  and sTTI- 13  and sTTI- 14  of CC 2 . 
     In the sixth scenario  1000 , the UE  205  at sTTI- 0  on CC 1  when receiving an UL grant allocating PUSCH resources in sTTI- 4  which contains a PHR MAC CE, i.e., there was a triggered PHR pending before sTTI- 0 , is not aware of the presence of a UL grant received for the overlapping sTTI- 13 . However, the UE  205  at sTTI- 0  on CC 1  is aware of the configured grant for sTTI- 14  on CC 2 . Therefore, the UE  205  may report an actual PHR for CC 2  for sTTI- 14  within the PHR MAC CE contained in the PUSCH in sTTI- 4  on CC 1 . 
     Because at the point of time when UE is generating the PHR MAC CE it is only aware of the configured grant in sTTI- 14 , the UE reports an actual PHR for this sTTI on CC 2  even though the UE  205  might later on skip the corresponding PUSCH transmission on CC 2  (in sTTI- 14 ) due to an empty buffer. It should be noted that the PHR format is different for an actual reported PHR and a virtual PHR due to the fact that the UE reports P C MAX,C for an actual PHR in addition to the PH info. Therefore, in various embodiments the UE  205  follows the determined PHR format even if, later on, the UE  205  is actually not performing a PUSCH transmission on a serving cell for which an actual PHR is reported. 
     According to another embodiment, the UE  205  aggregating several serving cells reports an actual PHR for a serving cell according to a dynamic UL grant, i.e., UL resource allocated by Downlink Control Information (“DCI”), even though the UE skips the corresponding PUSCH transmission on this serving cell since there is no data available for transmission in the buffer. Similar as for the previous embodiment, reporting an actual PHR is beneficial for the scheduler since the actual PHR, i.e., power headroom information calculation computed according to the received UL grant, provides information on the MPR used for the corresponding UL allocation. 
     Referring again to  FIG.  9   , the UE  205  may transmit a PHR MAC CE in sTTI- 4  on CC 1  including a virtual PH for CC 2  because the UE is not aware of any uplink allocations in the “overlapping” sTTIs on CC 2  when generating the PHR MAC CE. In the case where the UE  205  receives later in sTT 8  on CC 2  an UL grant for sTTI- 14 , the UE  205  may include a PHR MAC CE in the corresponding PUSCH transmission in sTTI- 14  which includes an actual PHR for CC 2  (actual PHR computed based on UL grant for sTTI- 14 ). This second PHR MAC CE provides more detailed information to the scheduler in the RAN node, e.g., because it also provides information on the used MPR for CC 2 . 
     For cases where a “longer” sTTI overlaps with several “shorter” sTTIs and several of these overlapping (s)TTIs are scheduled for an uplink transmission, a rule (e.g., network policy) allows for unambiguous determination of which of the overlapping (s)TTIs UE reports power headroom information. 
     The PHR is used to give the scheduler (in RAN node) an indication whether additional resources can be scheduled without power scaling at the UE  205 , or whether resources should be reduced to avoid the power scaling. Therefore, according to another embodiment, the UE  205  reports the smallest PHR across the scheduled “overlapping” sTTIs. Referring again to  FIG.  7   , the UE  205  may report for CC 2 , the smallest actual PHR of the multiple (scheduled) overlapping sTTIs (e.g., that of sTTI- 3  on CC 2 ). 
     According to another embodiment, the PHR MAC CE includes a field to indicate which TDU was used for the PHR computation for CC 2 . Then the scheduler in the RAN node unambiguously knows which UL grant is the reference for the PH computation. Including the information explicitly in the PHR MAC CE would be also a safeguard against the loss of an UL grant, i.e., a situation where the base station scheduled sTTI- 1  through sTTI- 3  on CC 2 , but the UE  205  only detects the scheduling for sTTI- 2  and sTTI- 3 . In that case, if there is no explicit TDU indicator included in the PHR MAC CE, but only the rule exists that the PHR is based on the first overlapping scheduled sTTI, the UE  205  would report for sTTI- 2  on CC 2 , but the RAN nodes would (incorrectly) interpret it as a PHR valid for sTTI- 1  on CC 2 . 
     Furthermore, for the case where the UE  205  is free to choose which TDU is the reference for the reported sTTI (i.e., the UE  205  would be free to not report the minimum PHRs for that carrier), the indication of the reference TDU is used by the scheduler to correctly interpret the reported PH information and to use this information for future uplink resource allocations. 
     In one embodiment, on a first CC (also referred to as “CC 1 ”) in which the PHR MAC CE is not transmitted, if PUSCH is scheduled on this carrier (i.e., CC 1 ) in the subframe in which the PHR is transmitted on the second CC (also referred to as “CC 2 ”), and an sPUSCH also is scheduled on the first CC or sPUCCH is transmitted on the first CC, then the PUSCH transmission is stopped or dropped in the subframe on the first CC and sPUSCH/sPUCCH is transmitted on the first CC. Here, the PHR for this carrier (i.e., CC 1 ) is an actual PHR for the scheduled PUSCH. 
       FIG.  11    depicts one embodiment of a method  1100  for receiving a paging message, according to embodiments of the disclosure. In some embodiments, the method  1100  is performed by a remote unit, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . In certain embodiments, the method  1100  may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like. 
     The method  1100  begins and the remote unit communicates  1105  with a base unit using a first uplink carrier and a second uplink carrier concurrently. Here, each carrier has a different transmission duration unit length, wherein the first uplink carrier has a longer transmission duration unit length than the second uplink carrier. In some embodiments, each of the first and second uplink carriers is associated with a different serving cell. 
     The method  1100  includes receiving  1110  an uplink resource allocation for a first transmission duration unit on the first uplink carrier. Here, the first transmission duration unit overlaps in time with at least two second transmission duration units on the second uplink carrier. 
     In certain embodiments, the remote unit also receives an uplink resource allocation for at least one of the overlapping second transmission duration units on the second uplink carrier. 
     The method  1100  includes determining  1115  a third transmission duration unit on the second uplink carrier. Here, the third transmission duration unit comprises at least one of the second transmission duration units. 
     The method  1100  includes calculating  1120  PH information for the second uplink carrier associated with the third transmission duration unit and reporting  1125  the PH information in an uplink transmission on the first transmission duration unit. The method  1100  ends. In some embodiments, the PH information is calculated according to a predefined reference format. In certain embodiments, the PH information is calculated assuming the apparatus is not scheduled to transmit a PUSCH in the third transmission duration unit. 
     In some embodiments, the first transmission duration unit corresponds to a slot on the first uplink carrier and the second transmission duration unit corresponds to a slot on the second uplink carrier. In certain embodiments, multiple second slots on the second uplink carrier fully overlap with the first slot. In such embodiments, calculating  1120  PH information may include calculating PH information for a first physical uplink shared channel (“PUSCH”) scheduled on the first of the multiple second slots that fully overlaps with the first slot on the first uplink carrier, wherein reporting  1125  the PH information for the second uplink carrier in an uplink transmission on the first slot comprises transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH. In certain embodiments, the first uplink carrier is configured with a first subcarrier spacing (“SCS”) and the second uplink carrier is configured with a second SCS, wherein the first SCS is smaller than the second SCS. 
     In some embodiments, the first transmission duration unit corresponds to a transmit time interval (“TTI”) of the first uplink carrier and the second transmission duration unit corresponds to a TTI of the second uplink carrier. In certain embodiments, the first uplink carrier is configured with a first TTI length and the second uplink carrier is configured with a second TTI length, wherein the first TTI length is larger than the second TTI length. In such embodiments, calculating  1120  PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH for a TTI duration longer than the second TTI length. 
     In certain embodiments, the length of the third transmission duration unit is greater than the length of the first TTI. In certain embodiments, the third transmission duration unit is equal to a subframe. In certain embodiments, calculating  1120  PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH information for a subframe containing the first TTI. In certain embodiments, the third transmission duration unit contains multiple TTIs of the second uplink carrier. 
     In various embodiments, the reporting  1125  PH information comprises reporting a power headroom level computed based on the uplink resource allocation. In some embodiments, the at least one of the second transmission duration units on the second uplink carrier (e.g., second TTI on the second uplink carrier) has a shortened TTI length that is less than 1 millisecond. In some embodiments, the PH information is calculated based on an uplink resource allocation received for the third transmission duration unit. In such embodiments, the uplink transmission on the third transmission duration may be either stopped or dropped. 
       FIG.  12    depicts one embodiment of a method  1200  for reporting power headroom information, according to embodiments of the disclosure. In various embodiments, the method  1200  is performed by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . In some embodiments, the method  1200  is performed by a processor, such as a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like. 
     The method  1200  begins and receives  1205  a configuration for a first serving cell for physical uplink shared channel (“PUSCH”) transmissions having a first subcarrier spacing (“SCS”) and a second serving cell for PUSCH transmissions having a second SCS, wherein the first SCS is smaller than the second SCS. The method  1200  includes receiving  1210  an uplink resource allocation for a first slot on the first serving cell, wherein the first slot overlaps in time with multiple second slots on the second serving cell. The method  1200  includes receiving  1215  an uplink resource allocation for at least one of the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. The method  1200  includes calculating  1220  PH information for the second serving cell for a first PUSCH scheduled on a first slot of the multiple second slots that fully overlaps with the first slot on the first serving cell. The method  1200  includes transmitting  1225  the PH information in an uplink transmission on the first slot on the first serving cell. The method  1200  ends. 
       FIG.  13    depicts one embodiment of a method  1300  for reporting power headroom information, according to embodiments of the disclosure. In various embodiments, the method  1300  is performed by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . In some embodiments, the method  1300  is performed by a processor, such as a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like. 
     The method  1300  begins and receives  1305  a configuration for a first serving cell having a first TTI length and a second serving cell having a second TTI length, where the second TTI length is smaller than the first TTI length. The method  1300  includes receiving  1310  an uplink resource allocation for a first TTI on the first serving cell, where the first TTI overlaps in time with multiple second TTIs on the second serving cell. The method  1300  includes calculating  1315  PH information for the second serving cell for a third TTI associated with a third TTI length that contains the first TTI on the first serving cell. The method  1300  includes transmitting  1320  the PH information in an uplink transmission on the first TTI on the first serving cell. The method  1300  ends. 
     Disclosed herein is a first apparatus for reporting power headroom information, according to embodiments of the disclosure. The first apparatus may be implemented by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 , described above. The first apparatus includes a transceiver and a processor. The first apparatus is configured with (i.e., the processor receives a configuration via the transceiver for) a first serving cell for PUSCH transmissions having a first SCS and a second serving cell for PUSCH transmissions having a second SCS, where the first SCS is smaller than the second SCS. The first apparatus has (i.e., the processor receives via the transceiver) an uplink resource allocation for a first slot on the first serving cell, where the first slot overlaps in time with multiple second slots on the second serving cell. Additionally, the first apparatus has (i.e., the processor receives via the transceiver) an uplink resource allocation for at least one of the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. The processor calculates PH information for the second serving cell for a first PUSCH scheduled on a first slot of the multiple second slots that fully overlaps with the first slot on the first serving cell and controls the transceiver to transmit the PH information in an uplink transmission on the first slot on the first serving cell. 
     In some embodiments, the processor further receives (via the transceiver) a second uplink resource allocation for at least one of the overlapping second slots on the second uplink carrier. In some embodiments, transmitting the PH information in an uplink transmission on the first slot on the first serving cell includes transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH scheduled on the first of the multiple second slots that is fully overlapped by the first slot. 
     In some embodiments, transmitting the PH information includes transmitting a Type 1 power headroom report. In some embodiments, transmitting the PH information includes transmitting a PHR MAC CE in the uplink transmission in an allocated uplink allocation on the first serving cell. 
     In some embodiments, the first slot corresponds to a TTI of the first serving cell and the second slots correspond to TTIs of the second serving cell. In certain embodiments, the PH information for the second serving cell is calculated for TTI duration that contains multiple TTIs of the second serving cell. 
     In some embodiments, the first serving cell is configured with a first TTI length and the second serving cell is configured with a second TTI length, where the first TTI length is larger than the second TTI length. In certain embodiments, calculating PH information for the second serving cell includes calculating PH information for a subframe that uses the first TTI length. 
     In certain embodiments, calculating PH information for the second serving cell includes calculating PH for a TTI duration longer than the second TTI length. In one embodiment, the PH for the second serving cell is calculated for TTI duration that is greater than the length of the first TTI. In another embodiment, the PH for the second serving cell is calculated for TTI duration that is equal to a subframe. 
     In some embodiments, the PH information is calculated according to a predefined reference format. In certain embodiments, the PH information is calculated assuming the UE is not scheduled to transmit a PUSCH in the at least two second slots that fully overlaps with the first slot. 
     In some embodiments, the at least one of the second slots on the second serving cell has a shortened TTI length that is less than 1 millisecond. In some embodiments, the reported PH information includes a power headroom level computed based on the uplink resource allocation. 
     In some embodiments, the PH information is calculated based on an uplink resource allocation received for a transmission duration corresponding to multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. In certain embodiments, an uplink transmission on the transmission duration is one of: stopped and dropped. 
     Disclosed herein is a first method for reporting power headroom information, according to embodiments of the disclosure. The first method may be performed by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 , described above. The first method includes being configured with a first serving cell for PUSCH transmissions having a first SCS and a second serving cell for PUSCH transmissions having a second SCS, where the first SCS is smaller than the second SCS. The first method includes having an uplink resource allocation for a first slot on the first serving cell, where the first slot overlaps in time with multiple second slots on the second serving cell and having an uplink resource allocation for at least one of the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. The first method includes calculating PH information for the second serving cell for a first PUSCH scheduled on a first slot of the multiple second slots that fully overlaps with the first slot on the first serving cell. The first method includes transmitting the PH information in an uplink transmission on the first slot on the first serving cell. 
     In some embodiments, the first method further includes receiving a second uplink resource allocation for at least one of the overlapping second slots on the second uplink carrier. In some embodiments, transmitting the PH information in an uplink transmission on the first slot on the first serving cell includes transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH scheduled on the first of the multiple second slots that is fully overlapped by the first slot. 
     In some embodiments, transmitting the PH information includes transmitting a Type 1 power headroom report. In some embodiments, transmitting the PH information includes transmitting a PHR MAC CE in the uplink transmission in an allocated uplink allocation on the first serving cell. 
     In some embodiments, the first slot corresponds to a TTI of the first serving cell and the second slots correspond to TTIs of the second serving cell. In certain embodiments, the PH information for the second serving cell is calculated for TTI duration that contains multiple TTIs of the second serving cell. 
     In some embodiments, the first serving cell is configured with a first TTI length and the second serving cell is configured with a second TTI length, where the first TTI length is larger than the second TTI length. In certain embodiments, calculating PH information for the second serving cell includes calculating PH information for a subframe that uses the first TTI length. 
     In certain embodiments, calculating PH information for the second serving cell includes calculating PH for a TTI duration longer than the second TTI length. In one embodiment, the PH for the second serving cell is calculated for TTI duration that is greater than the length of the first TTI. In another embodiment, the PH for the second serving cell is calculated for TTI duration that is equal to a subframe. 
     In some embodiments, the PH information is calculated according to a predefined reference format. In certain embodiments, the PH information is calculated assuming the UE is not scheduled to transmit a PUSCH in the at least two second slots that fully overlaps with the first slot. 
     In some embodiments, the at least one of the second slots on the second serving cell has a shortened TTI length that is less than 1 millisecond. In some embodiments, the reported PH information includes a power headroom level computed based on the uplink resource allocation. 
     In some embodiments, the PH information is calculated based on an uplink resource allocation received for a transmission duration corresponding to the multiple second slots on the second serving cell that are overlapped by the first slot on the first serving cell. In certain embodiments, an uplink transmission on the transmission duration is one of: stopped and dropped. 
     Disclosed herein is a second apparatus for reporting PH information. In various embodiments, the second apparatus may be the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . The second apparatus includes a transceiver that communicates with a base unit using a first uplink carrier and a second uplink carrier concurrently. Here, each carrier has a different transmission duration unit length, wherein the first uplink carrier has a longer transmission duration unit length than the second uplink carrier. The second apparatus also includes a processor that receives an uplink resource allocation for a first transmission duration unit on the first uplink carrier. Here, the first transmission duration unit overlaps in time with at least two second transmission duration units on the second uplink carrier. The processor also determines a third transmission duration unit on the second uplink carrier. Here, the third transmission duration unit comprises at least one of the second transmission duration units. The processor calculates PH information for the second uplink carrier associated with the third transmission duration unit and reports, via the transceiver, the PH information in an uplink transmission on the first transmission duration unit. 
     In some embodiments, each of the first and second uplink carriers is associated with a different serving cell. In some embodiments, the processor further receives an uplink resource allocation for at least one of the overlapping second transmission duration units on the second uplink carrier. 
     In some embodiments, the first transmission duration unit corresponds to a slot on the first uplink carrier and the second transmission duration unit corresponds to a slot on the second uplink carrier. In certain embodiments, multiple second slots on the second uplink carrier fully overlap with the first slot. In such embodiments, the processor calculates PH information for a first physical uplink shared channel (“PUSCH”) scheduled on the first of the multiple second slots that fully overlaps with the first slot on the first uplink carrier, wherein reporting PH information for the second uplink carrier in an uplink transmission on the first slot comprises transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH. In certain embodiments, the first uplink carrier is configured with a first subcarrier spacing (“SCS”) and the second uplink carrier is configured with a second SCS, wherein the first SCS is smaller than the second SCS. 
     In some embodiments, the first transmission duration unit corresponds to a transmit time interval (“TTI”) of the first uplink carrier and the second transmission duration unit corresponds to a TTI of the second uplink carrier. In certain embodiments, the first uplink carrier is configured with a first TTI length and the second uplink carrier is configured with a second TTI length, wherein the first TTI length is larger than the second TTI length. In such embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH for a TTI duration longer than the second TTI length. 
     In certain embodiments, the length of the third transmission duration unit is greater than the length of the first TTI. In certain embodiments, the third transmission duration unit is equal to a subframe. In certain embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH information for a subframe containing the first TTI. In certain embodiments, the third transmission duration unit contains multiple TTIs of the second uplink carrier. 
     In some embodiments, the processor calculates the PH information according to a predefined reference format. In certain embodiments, the processor calculates the PH information assuming the apparatus is not scheduled to transmit a PUSCH in the third transmission duration unit. 
     In various embodiments, the reported PH information comprises a power headroom level computed based on the uplink resource allocation. In some embodiments, the at least one of the second transmission duration units on the second uplink carrier has a shortened TTI length that is less than 1 millisecond. In some embodiments, the PH information is calculated based on an uplink resource allocation received for the third transmission duration unit. In such embodiments, the uplink transmission on the third transmission duration may be either stopped or dropped. 
     Disclosed herein is a second method for reporting PH information. In various embodiments, the second method is performed by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . The second method includes the UE communicating with a base unit using a first uplink carrier and a second uplink carrier concurrently. Here, each carrier has a different transmission duration unit length, wherein the first uplink carrier has a longer transmission duration unit length than the second uplink carrier. The second method includes receiving an uplink resource allocation for a first transmission duration unit on the first uplink carrier. Here, the first transmission duration unit overlaps in time with at least two second transmission duration units on the second uplink carrier. The second method includes determining a third transmission duration unit on the second uplink carrier. Here, the third transmission duration unit comprises at least one of the second transmission duration units. The second method includes calculating PH information for the second uplink carrier associated with the third transmission duration unit and reporting the PH information in an uplink transmission on the first transmission duration unit. 
     In some embodiments, each of the first and second uplink carriers is associated with a different serving cell. In some embodiments, the second method further includes receiving an uplink resource allocation for at least one of the overlapping second transmission duration units on the second uplink carrier. 
     In some embodiments, the first transmission duration unit corresponds to a slot on the first uplink carrier and the second transmission duration unit corresponds to a slot on the second uplink carrier. In certain embodiments, multiple second slots on the second uplink carrier fully overlap with the first slot. In such embodiments, the method further includes calculating PH information for a first physical uplink shared channel (“PUSCH”) scheduled on the first of the multiple second slots that fully overlaps with the first slot on the first uplink carrier, wherein reporting PH information for the second uplink carrier in an uplink transmission on the first slot comprises transmitting on a PUSCH a PHR that contains the PH information for the first PUSCH. In certain embodiments, the first uplink carrier is configured with a first subcarrier spacing (“SCS”) and the second uplink carrier is configured with a second SCS, wherein the first SCS is smaller than the second SCS. 
     In some embodiments, the first transmission duration unit corresponds to a transmit time interval (“TTI”) of the first uplink carrier and the second transmission duration unit corresponds to a TTI of the second uplink carrier. In certain embodiments, the first uplink carrier is configured with a first TTI length and the second uplink carrier is configured with a second TTI length, wherein the first TTI length is larger than the second TTI length. In such embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH for a TTI duration longer than the second TTI length. 
     In certain embodiments, the length of the third transmission duration unit is greater than the length of the first TTI. In certain embodiments, the third transmission duration unit is equal to a subframe. In certain embodiments, calculating PH information for the second uplink carrier associated with the third transmission duration unit comprises calculating PH information for a subframe containing the first TTI. In certain embodiments, the third transmission duration unit contains multiple TTIs of the second uplink carrier. 
     In some embodiments, the PH information is calculated according to a predefined reference format. In certain embodiments, the PH information is calculated assuming the apparatus is not scheduled to transmit a PUSCH in the third transmission duration unit. 
     In various embodiments, the reported PH information comprises a power headroom level computed based on the uplink resource allocation. In some embodiments, the at least one of the second transmission duration units on the second uplink carrier has a shortened TTI length that is less than 1 millisecond. In some embodiments, the PH information is calculated based on an uplink resource allocation received for the third transmission duration unit. In such embodiments, the uplink transmission on the third transmission duration may be either stopped or dropped. 
     Disclosed herein is a third apparatus for reporting power headroom information. The third apparatus may be implemented by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . The third apparatus includes a memory and a processor coupled to the memory, where the processor is configured to: A) receive an uplink resource allocation for a first TTI on the first serving cell, where the first TTI overlaps in time with multiple second TTIs on the second serving cell, where the apparatus is configured with a first serving cell having a first TTI length and a second serving cell having a second TTI length, and where the second TTI length is smaller than the first TTI length; B) calculate PH information for the second serving cell for a third TTI associated with a third TTI length that contains the first TTI on the first serving cell; and C) transmit the PH information in an uplink transmission on the first TTI on the first serving cell. 
     In some embodiments, to transmit the PH information, the processor is configured to cause the apparatus to transmit a PHR MAC CE in the uplink transmission on the uplink resource allocation on the first serving cell. In certain embodiments, the reported PHR MAC CE comprises a power headroom information for the first serving cell computed based on the uplink resource allocation. 
     In some embodiments, to calculate the PH information for the second serving cell for the third TTI, the processor is configured to cause the apparatus to calculate PH information for a TTI length being longer than the second TTI length. In some embodiments, the length of the third TTI is greater than the length of the first TTI. In some embodiments, the third TTI is equal to a subframe. 
     In some embodiments, to calculate the PH information for the second serving cell for the third TTI, the processor is configured to cause the third apparatus to calculating PH information for a subframe containing the first TTI. In some embodiments, the third TTI contains multiple TTIs of the second serving cell. 
     In some embodiments, the processor calculates the PH information based on a predefined reference format. In certain embodiments, the processor calculates the PH information assuming the third apparatus is not scheduled to transmit a PUSCH in the third TTI. 
     In some embodiments, the first TTI length is equal to a slot. In some embodiments, the at least one of the second slots on the second serving cell has a shortened TTI length that is less than 1 millisecond. 
     Disclosed herein is a third method for reporting power headroom information. The third method may be performed by a UE device, such as the remote unit  105 , the UE  205 , and/or the user equipment apparatus  400 . The third method includes being configured with a first serving cell having a first TTI length and a second serving cell having a second TTI length, wherein the second TTI length is smaller than the first TTI length and having an uplink resource allocation for a first TTI on the first serving cell, wherein the first TTI overlaps in time with multiple second TTIs on the second serving cell. The third includes calculating PH information for the second serving cell for a third TTI associated with a third TTI length that contains the first TTI on the first serving cell and transmitting the PH information in an uplink transmission on the first TTI on the first serving cell. 
     In some embodiments, transmitting the PH information comprises transmitting a PHR MAC CE in the uplink transmission on the uplink resource allocation on the first serving cell. In certain embodiments, the reported PHR MAC CE comprises power headroom information for the first serving cell computed based on the uplink resource allocation. 
     In some embodiments, calculating the PH information for the second serving cell for the third TTI comprises calculating PH information for a TTI length being longer than the second TTI length. In some embodiments, the length of the third TTI is greater than the length of the first TTI. In some embodiments, the third TTI is equal to a subframe. 
     In some embodiments, calculating PH information for the second serving cell for the third TTI comprises calculating PH information for a subframe containing the first TTI. In some embodiments, the third TTI contains multiple TTIs of the second serving cell. 
     In some embodiments, the PH information is calculated based on a predefined reference format. In certain embodiments, the PH information is calculated assuming the UE is not scheduled to transmit a PUSCH in the third TTI. 
     In some embodiments, the first TTI length is equal to a slot. In some embodiments, the at least one of the second slots on the second serving cell has a shortened TTI length that is less than 1 millisecond. 
     Embodiments may be practiced in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.