Patent Publication Number: US-2018049046-A1

Title: Apparatus and method of signalling support for reduced latency operation

Description:
BACKGROUND 
     Field 
     Embodiments of the invention generally relate to wireless or mobile communications networks, such as, but not limited to, the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), LTE-A Pro, and/or 5G radio access technology. Some embodiments may generally relate to latency reduction in such networks. 
     Description of the Related Art 
     Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) refers to a communications network including base stations, or Node Bs, and for example radio network controllers (RNC). UTRAN allows for connectivity between the user equipment (UE) and the core network. The RNC provides control functionalities for one or more Node Bs. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS). In case of E-UTRAN (enhanced UTRAN), no RNC exists and radio access functionality is provided by an evolved Node B (eNodeB or eNB) or many eNBs. Multiple eNBs are involved for a single UE connection, for example, in case of Coordinated Multipoint Transmission (CoMP) and in dual connectivity. 
     Long Term Evolution (LTE) or E-UTRAN refers to improvements of the UMTS through improved efficiency and services, lower costs, and use of new spectrum opportunities. In particular, LTE is a 3GPP standard that provides for uplink peak rates of at least, for example, 75 megabits per second (Mbps) per carrier and downlink peak rates of at least, for example, 300 Mbps per carrier. LTE supports scalable carrier bandwidths from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD). 
     As mentioned above, LTE may also improve spectral efficiency in networks, allowing carriers to provide more data and voice services over a given bandwidth. Therefore, LTE is designed to fulfill the needs for high-speed data and media transport in addition to high-capacity voice support. Advantages of LTE include, for example, high throughput, low latency, FDD and TDD support in the same platform, an improved end-user experience, and a simple architecture resulting in low operating costs. 
     Certain releases of 3GPP LTE (e.g., LTE Rel-10, LTE Rel-11, LTE Rel-12, LTE Rel-13) are targeted towards international mobile telecommunications advanced (IMT-A) systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). 
     LTE-A is directed toward extending and optimizing the 3GPP LTE radio access technologies. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is a more optimized radio system fulfilling the international telecommunication union-radio (ITU-R) requirements for IMT-Advanced while maintaining backward compatibility. One of the key features of LTE-A, introduced in LTE Rel-10, is carrier aggregation, which allows for increasing the data rates through aggregation of two or more LTE carriers. 
     5 th  generation wireless systems (5G) refers to the new generation of radio systems and network architecture. 5G is expected to provide higher bitrates and coverage than the current LTE systems. Some estimate that 5G will provide bitrates one hundred times higher than LTE offers. 5G is also expected to increase network expandability up to hundreds of thousands of connections. The signal technology of 5G is anticipated to be improved for greater coverage as well as spectral and signaling efficiency. 
     SUMMARY 
     In a first aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and at least one memory that includes computer program code. The at least one memory and computer program code are configured, with the at least one data processor, to cause the apparatus, at least to transmit, by the apparatus, a configuration for reduced processing time operation on a specific carrier to a user equipment; perform a scheduling decision for the user equipment for physical downlink shared channel and/or physical uplink shared channel wherein the scheduling decision comprises determining, based at least on a latency reduction threshold, of whether to apply reduced processing time. 
     In a further aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and at least one memory that includes computer program code. The at least one memory and computer program code are configured, with the at least one data processor, to cause the apparatus, at least to receive, from a base station, a configuration for reduced processing time operation on a specific carrier; receive, from the base station, downlink control information scheduling physical downlink shared channel and/or physical uplink shared channel; determine, based at least on a latency reduction threshold, whether to apply reduced processing time; and transmitting physical uplink shared channel or downlink hybrid automatic repeat request information according to a selected timing determined based on the latency reduction threshold. 
     In another aspect thereof the exemplary embodiments of this invention provide a method that comprises transmitting, by a base station, a configuration for reduced processing time operation on a specific carrier to a user equipment; performing a scheduling decision for the user equipment for physical downlink shared channel and/or physical uplink shared channel wherein the scheduling decision comprises determining, based at least on a latency reduction threshold, of whether to apply reduced processing time. 
     In a first aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and at least one memory that includes computer program code. The at least one memory and computer program code are configured, with the at least one data processor, to cause the apparatus, at least to transmit, by the apparatus, a configuration for reduced processing time operation on a specific carrier to a user equipment; perform a scheduling decision for the user equipment for physical downlink shared channel and/or physical uplink shared channel wherein the scheduling decision comprises determining, based at least on a latency reduction threshold, of whether to apply reduced processing time. 
     In a further aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and at least one memory that includes computer program code. The at least one memory and computer program code are configured, with the at least one data processor, to cause the apparatus, at least to receive, from a base station, a configuration for reduced processing time operation on a specific carrier; receive, from the base station, downlink control information scheduling physical downlink shared channel and/or physical uplink shared channel; determine, based at least on a latency reduction threshold, whether to apply reduced processing time; and transmitting physical uplink shared channel or downlink hybrid automatic repeat request information according to a selected timing determined based on the latency reduction threshold. 
     In another aspect thereof the exemplary embodiments of this invention provide a method that comprises transmitting, by a base station, a configuration for reduced processing time operation on a specific carrier to a user equipment; performing a scheduling decision for the user equipment for physical downlink shared channel and/or physical uplink shared channel wherein the scheduling decision comprises determining, based at least on a latency reduction threshold, of whether to apply reduced processing time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For proper understanding of the invention, reference should be made to the accompanying drawings, wherein: 
         FIG. 1  illustrates an example block diagram of an approach for processing time switching for HARQ-ACK transmission corresponding to DL data (PDSCH) transmission, according to one embodiment; 
         FIG. 2  illustrates an example block diagram of an approach for processing time switching for PUSCH data transmission, according to one embodiment; 
         FIG. 3  illustrates an example signaling diagram, according to one embodiment; 
         FIG. 4 a    illustrates an example block diagram of an apparatus, according to one embodiment; 
         FIG. 4 b    illustrates an example block diagram of an apparatus, according to another embodiment; 
         FIG. 5 a    illustrates an example flow diagram of a method, according to an embodiment; and 
         FIG. 5 b    illustrates an example flow diagram of a method, according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the components of the invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of embodiments of systems, methods, apparatuses, and computer program products of signalling support for reduced latency operation, as represented in the attached figures, is not intended to limit the scope of the invention, but is merely representative of some selected embodiments of the invention. 
     The features, structures, or characteristics of the invention described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus, appearances of the phrases “in certain embodiments,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Additionally, if desired, the different functions discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions may be optional or may be combined. As such, the following description should be considered as merely illustrative of the principles, teachings and embodiments of this invention, and not in limitation thereof. 
     Some embodiments of the invention may relate to the LTE-Advanced Pro system, which will be part of 3GPP LTE Rel-13/14. More specifically, certain embodiments are directed to latency reduction. A Rel-13 Study Item entitled, “Study on Latency reduction techniques” carried out in 3GPP has indicated that processing time reduction is necessary in order to improve the physical layer radio latency. Follow-up work items have objectives that include the introduction of shorter transmission time interval (TTI) operation with reduced processing, as well as also enabling reduced processing time for legacy 1 millisecond (ms) TTI channel designs. 
     Specifically, the work item objectives include, for Frame structure types 1, 2 and 3 for legacy 1 ms TTI operation, specifying support for a reduced minimum timing compared to legacy operation between UL grant and UL data and between DL data and DL HARQ feedback for legacy 1 ms TTI operation, reusing the 3GPP Rel-14 physical downlink shared channel (PDSCH)/(E)physical downlink control channel (PDCCH)/physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) channel design. This may apply at least for the case of restricted maximum supported transport block sizes for PDSCH and/or PUSCH when the reduced minimum timing is in operation, and if agreed by RAN1 for the case of unrestricted maximum supported transport block sizes. Another objective includes specifying support for a reduced maximum timing advance (TA) to enable processing time reductions. It is noted that the size of the reduction in minimum timing may be different between UL and DL cases. Any impact on channel state information (CSI) feedback and processing time may be studied and, if needed, necessary modifications may be specified. Also to be studied and specified, if agreed by RAN1, is asynchronous hybrid automatic repeat request (HARQ) for PUSCH with reduced processing time. 
     The allowed processing times for LTE FDD (LTE FS1) have been defined in 3GPP Rel-8 to have a N+4 relationship between the PDSCH and the related HARQ-Ack feedback, as well as between an UL grant sent to the UE and the related PUSCH transmission by the UE. This means that for the PDSCH transmitted in subframe/TTI N, the UE is required to feedback the related HARQ-Ack feedback in subframe/TTI N+4 (in the case of FDD/Frame Structure 1), or in subframe N+4 or later (in the case of TDD/FS2). Similarly, an UL grant sent in the subframe/TTI N requests the UE to send the related PUSCH in the subframe/TTI N+4. 
     With reduced processing time for the 1 ms TTI length, the aim is to decrease the processing time in a way to enable the UE: 1) to send the HARQ-Ack feedback earlier, and 2) to transmit PUSCH earlier. Instead of the LTE Rel-8 timing relation of N+4, a reduction to, for example, N+3 or even N+2 is currently envisioned. 
     Certain embodiments of the invention are directed to the signalling mechanisms that facilitate switching between different processing times (i.e., HARQ-ACK feedback delays and or UL scheduling delays), taking into account that UEs may not be able to process transport block of all sizes faster than using N+4 timing. It should be noted that since the 3GPP Work Item deals with Frame Structure 3 as well, some embodiments are also applicable to LTE Licensed Assisted Access (LAA), as well as MulteFire. 
     As discussed in the foregoing, reduction of the maximum supported transport block size may need to be considered along with shortened processing times. This may be necessary to ensure that a UE can indeed process the data one or two milliseconds faster, as required. On the other hand, it should be possible to switch back to legacy N+4 ms timing and vice versa, allowing for utilization of all transport block sizes when necessary, for example when the TCP window grows over certain threshold or is reset. In other words, the network should have the means for dynamic (on a per subframe time scale) switching between the legacy N+4 timing, and the reduced processing times with N+2 or N+3 ms timing. Embodiments of the invention provide solutions for performing such switching, while minimizing the changes to the LTE air interface (e.g., PDCCH DCI formats). 
     One embodiment includes determining the timing for HARQ-ACK feedback transmission corresponding to PDSCH transport block, and/or timing between UL grant reception and PUSCH transmission such that the complexity of UE processing associated with the DL or UL data processing is taken into account. For example, an embodiment is configured to determine the HARQ-ACK feedback timing and/or UL grant timing based on a Latency Reduction Threshold (LRT), where the LRT is defined as discussed in the following. 
     In an embodiment, the LRT is defined in terms of a Transport Block Size (in the case of single multiple input multiple output (MIMO) layer transmission) and/or sum of Transport Block Sizes (with MIMO spatial multiplexing, taking the number of transmitted channel coded codewords into account). An LRT may be set such that, for Transport Block Sizes (TBSs) below the LRT a faster timing is applied, and, for TBSs larger than the LRT, legacy N+4 timing is used. In certain embodiments, the LRT may be predetermined, such as being fixed in the (3GPP) specifications, or may be configurable by the eNB. For example, the maximum value for LRT may be fixed in the specifications or depend on UEs capability, but the eNB may choose a lower value for the threshold amongst a predefined set of values and indicate the threshold for the UE via RRC signalling. 
     In some embodiments, the Latency Reduction Threshold may also depend on the subframe type (e.g., normal vs. DwPTS), system bandwidth (BW), DL Transmission mode/scheme (e.g., CRS vs. DMRS based demodulation), and/or the downlink physical control channel used (e.g., PDCCH vs. EPDCCH based DL control). When the Latency Reduction Threshold depends on the subframe type, in DwPTS subframes the threshold may be scaled according to the number of available OFDM symbols. When the Latency Reduction Threshold depends on the DL Transmission mode/scheme, for DMRS based DL demodulation, since the time required for channel estimation is larger than with CRS based operation, N+4 timing may always be followed, or the LRT may be defined separately from that of CRS based demodulation (e.g., smaller LRT for DM-RS based PDSCH demodulation compared to CRS based demodulation in order to balance the longer time needed for channel estimation). When the Latency Reduction Threshold depends on the downlink physical control channel used, a DL or UL grant can be either sent through 3GPP Rel. 8 PDCCH—or EPDCCH introduced in 3GPP Rel. 11. The UE is able to start DL control (DCI) decoding with PDCCH immediately after end the PDCCH at latest in the 5 OFDM symbol of a DL subframe whereas in case of EPDCCH the information is spread in time over the full DL subframe and the DCI blind decoding with EPDCCH can start later. Therefore, it would be possible to define a smaller LRT for EPDCCH based DL control, whereas a larger LRT for PDCCH based DL control could be applied. This way, the additional about half a subframe latency of EPDCCH compared to PDCCH based DL control can be balanced. Alternatively, the different timing may be applied with PDCCH and EPDCCH. For example, with PDCCH the timing could be N+2 whereas with EPDCCH N+3 timing might suffice. 
       FIG. 1  illustrates an example block diagram of an approach for processing time switching for HARQ-ACK transmission corresponding to DL data (PDSCH) transmission (the example shown applies PDCCH based DL control).  FIG. 2  illustrates an example block diagram of an approach for processing time switching for PUSCH data transmission (example shown applies PDCCH based DL control). 
     Alternatively or additionally, instead of TBS, the Latency Reduction Threshold may be defined in terms of Coding rate, or Coding rate×modulation order, or equivalently based on the number of coded PDSCH (or PUSCH) bits (i.e., transport block size) divided by the number of available uncoded PDSCH (or PUSCH) bits. In another embodiment, the Latency Reduction Threshold may be defined in terms of the number of allocated Physical Resource Blocks, i.e., the allocated bandwidth. For example, when the number of allocated PRBs is below a threshold, faster (N+X where X is &lt;4) timing is applied. In yet another embodiment, the Latency Reduction Threshold may be defined in terms of the number of spatial MIMO layers. For example, faster processing is applied only when the number of MIMO layers is less than a predetermined number (e.g., less than 2, i.e., no spatial multiplexing is applied). 
       FIG. 3  illustrates an example signaling flow diagram, according to one embodiment of the invention. As illustrated in  FIG. 3 , at  101 , the eNB configures the UE (e.g., a reduced processing time capable UE) with reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, which may be DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). At  102 , the eNB makes a scheduling decision selecting processing time for the UE for PDSCH and/or PUSCH taking into account the restrictions given by the Latency Reduction Threshold (LRT), and prepares the related DL control information (DCI). Thus, the scheduling decision may include, for example, whether reduced processing time or legacy processing time is to be applied. The selecting of a processing time may be based on the LRT in combination with the used DL transmission mode, system BW, subframe type, DL control region, and/or assignment content (number of MIMO layers, TBS size). Then, at  103 , the eNB may transmit the DL control information (and in case of PDSCH scheduling, the related PDSCH) to the UE. At  104 , the UE may transmit, to the eNB, the PUSCH or DL HARQ-Ack information (on PUCCH or PUSCH) according to the selected processing time (i.e., legacy N+4 assumption or reduced processing time assumption) in the requested subframe given by N+4 or N+2 or N+3, respectively, depending on the Latency Reduction Threshold. 
     In another embodiment, a UE, such as a reduced processing time capable UE, may receive from the eNB a configuration for reduced processing time operation on a specific carrier. According to one embodiment, the received configuration may include the configuration of the LRT, which may be DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). The UE may also receive DCI scheduling PDSCH or PUSCH and may determine, based on a Latency Reduction Threshold whether reduced processing time should be applied or not. In certain embodiments, the UE may then transmit HARQ-ACK or PUSCH according to the timing determined based on the Latency Reduction Threshold. 
       FIG. 4 a    illustrates an example of an apparatus  10  according to an embodiment. In an embodiment, apparatus  10  may be a node, host, or server in a communications network or serving such a network. For example, apparatus  10  may be a network node or access node for a radio access network, such as a base station, node B or eNB, or an access node of 5G radio access technology. Thus, in certain embodiments, apparatus  10  may include a base station, access node, node B or eNB serving a cell. It should be noted that one of ordinary skill in the art would understand that apparatus  10  may include components or features not shown in  FIG. 4   a.    
     As illustrated in  FIG. 4 a   , apparatus  10  may include a processor  22  for processing information and executing instructions or operations. Processor  22  may be any type of general or specific purpose processor. While a single processor  22  is shown in  FIG. 4 a   , multiple processors may be utilized according to other embodiments. In fact, processor  22  may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. 
     Processor  22  may perform functions associated with the operation of apparatus  10  which may include, for example, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus  10 , including processes related to management of communication resources. 
     Apparatus  10  may further include or be coupled to a memory  14  (internal or external), which may be coupled to processor  12 , for storing information and instructions that may be executed by processor  12 . Memory  14  may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. For example, memory  14  can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory  14  may include program instructions or computer program code that, when executed by processor  12 , enable the apparatus  10  to perform tasks as described herein. 
     In some embodiments, apparatus  10  may also include or be coupled to one or more antennas  15  for transmitting and receiving signals and/or data to and from apparatus  10 . Apparatus  10  may further include or be coupled to a transceiver  18  configured to transmit and receive information. The transceiver  18  may include, for example, a plurality of radio interfaces that may be coupled to the antenna(s)  15 . The radio interfaces may correspond to a plurality of radio access technologies including one or more of LTE, WLAN, Bluetooth, BT-LE, NFC, radio frequency identifier (RFID), ultrawideband (UWB), and the like. The radio interface may include components, such as filters, converters (for example, digital-to-analog converters and the like), mappers, a Fast Fourier Transform (FFT) module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols (for example, via an uplink). As such, transceiver  18  may be configured to modulate information on to a carrier waveform for transmission by the antenna(s)  15  and demodulate information received via the antenna(s)  15  for further processing by other elements of apparatus  10 . In other embodiments, transceiver  18  may be capable of transmitting and receiving signals or data directly. 
     In an embodiment, memory  14  may store software modules that provide functionality when executed by processor  12 . The modules may include, for example, an operating system that provides operating system functionality for apparatus  10 . The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus  10 . The components of apparatus  10  may be implemented in hardware, or as any suitable combination of hardware and software. 
     In one embodiment, apparatus  10  may be a network node or access node, such as a base station, node B or eNB, or an access node of 5G, for example. According to one embodiment, apparatus  10  may be controlled by memory  14  and processor  12  to perform the functions associated with embodiments described herein. For instance, in an embodiment, apparatus  10  may be controlled by memory  14  and processor  12  to configure a UE with reduced processing time operation on a specific carrier. For example, in one embodiment, apparatus  10  may be controlled by memory  14  and processor  12  to transmit a configuration for reduced processing time operation on the specific carrier to the UE. The configuration may include, for instance, the configuration of the LRT, which may be DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). 
     According to certain embodiments, apparatus  10  may be further controlled by memory  14  and processor  12  to perform a scheduling decision selecting processing time for the UE for PDSCH and/or PUSCH taking the LRT into account and to prepare the related DL control information (DCI). In one embodiment, the scheduling decision may include whether reduced processing time or legacy processing time is to be applied. In some embodiments, apparatus  10  may also be controlled by memory  14  and processor  12  to transmit the DL control information (DCI) and, in case of PDSCH scheduling, the related PDSCH to the UE. According to an embodiment, apparatus  10  may also be controlled by memory  14  and processor  12  to receive the PUSCH or DL HARQ-ACK information (on PUCCH or PUSCH) according to the selected processing time (legacy N+4 assumption or reduced processing time assumption) in the requested subframe given by N+4 or N+2 or N+3, respectively, depending on the LRT. 
       FIG. 4 b    illustrates an example of an apparatus  20  according to another embodiment. In an embodiment, apparatus  20  may be a node or element in a communications network or associated with such a network, such as a UE, mobile device, stationary device, or other device. A UE may alternatively be referred to as, for example, a mobile station, mobile unit, mobile device, user device, subscriber station, wireless terminal, tablet, smart phone, or the like. Apparatus  20  may be implemented as, for example, a wireless handheld device, a wireless plug-in accessory, or the like. In some example embodiments, apparatus  20  may include one or more processors, one or more computer-readable storage medium (for example, memory, storage, and the like), one or more radio access components (for example, a modem, a transceiver, and the like), and/or a user interface. In some embodiments, apparatus  20  may be a UE configured to operate using one or more radio access technologies, such as LTE, LTE-A, 5G, WLAN, WiFi, Bluetooth, NFC, and any other radio access technologies. Moreover, apparatus  20  may be configured to have established connections to access points using a plurality of the radio access technologies. It should be noted that one of ordinary skill in the art would understand that apparatus  20  may include components or features not shown in  FIG. 4   b.    
     As illustrated in  FIG. 4 b   , apparatus  20  may include a processor  22  for processing information and executing instructions or operations. Processor  22  may be any type of general or specific purpose processor. While a single processor  22  is shown in  FIG. 4 b   , multiple processors may be utilized according to other embodiments. In fact, processor  22  may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. 
     Processor  22  may perform functions associated with the operation of apparatus  20  including, without limitation, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus  20 , including processes related to management of communication resources. 
     Apparatus  20  may further include or be coupled to a memory  24  (internal or external), which may be coupled to processor  22 , for storing information and instructions that may be executed by processor  22 . Memory  24  may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. For example, memory  24  can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory  24  may include program instructions or computer program code that, when executed by processor  22 , enable the apparatus  20  to perform tasks as described herein. 
     In some embodiments, apparatus  20  may also include or be coupled to one or more antennas  25  for receiving a downlink or signal and for transmitting via an uplink from apparatus  20 . Apparatus  20  may further include a transceiver  28  configured to transmit and receive information. The transceiver  28  may also include a radio interface (e.g., a modem) coupled to the antenna  25 . The radio interface may correspond to a plurality of radio access technologies including one or more of LTE, LTE-A, 5G, WLAN, Bluetooth, BT-LE, NFC, RFID, UWB, and the like. The radio interface may include other components, such as filters, converters (for example, digital-to-analog converters and the like), symbol demappers, signal shaping components, an Inverse Fast Fourier Transform (IFFT) module, and the like, to process symbols, such as OFDMA symbols, carried by a downlink or an uplink For instance, transceiver  28  may be configured to modulate information on to a carrier waveform for transmission by the antenna(s)  25  and demodulate information received via the antenna(s)  25  for further processing by other elements of apparatus  20 . In other embodiments, transceiver  28  may be capable of transmitting and receiving signals or data directly. Apparatus  20  may further include a user interface. 
     In an embodiment, memory  24  stores software modules that provide functionality when executed by processor  22 . The modules may include, for example, an operating system that provides operating system functionality for apparatus  20 . The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus  20 . The components of apparatus  20  may be implemented in hardware, or as any suitable combination of hardware and software. 
     According to one embodiment, apparatus  20  may be a reduced processing time capable UE, for example. In this embodiment, apparatus  20  may be controlled by memory  24  and processor  22  to perform the functions associated with embodiments described herein. In one embodiment, apparatus  20  may be controlled by memory  24  and processor  22  to receive, from an eNB, a configuration for reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, such as DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). In an embodiment, apparatus  20  may also be controlled by memory  24  and processor  22  to receive DCI scheduling PDSCH or PUSCH and to determine, based on a LRT, whether reduced processing time should be applied or not. Apparatus  20  may then be controlled by memory  24  and processor  22  to transmit HARQ-ACK or PUSCH according to the timing determined based on the LRT. 
       FIG. 5 a    illustrates an example flow diagram of a method, according to one embodiment. The method may be performed by a base station, eNB, or access node, for example. The method of  FIG. 5 a    may include, at  500 , transmitting a configuration for reduced processing time operation on the specific carrier to a UE. The configuration, which applies for that specific carrier, may include, for instance, the configuration of the LRT, which may be DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH) specific. According to an embodiment, the method may also include, at  510 , performing a scheduling decision selecting processing time for the UE for PDSCH and/or PUSCH taking into account the LRT, and preparing the related DCI. In one embodiment, the scheduling decision may include whether reduced processing time or legacy processing time is to be applied. In addition to the LRT, the scheduling decision of whether to apply reduced processing time may also be based on the used DL transmission mode, system BW, subframe type, DL control region as well as assignment content (number of MIMO layers, TBS size). In some embodiments, the method may further include, at  520 , transmitting the DCI and, in case of PDSCH scheduling, the related PDSCH to the UE. According to an embodiment, the method includes, at  530 , receiving the PUSCH or DL HARQ-ACK information (on PUCCH or PUSCH) according to the selected processing time (legacy N+4 assumption or reduced processing time assumption) in the requested subframe given by N+4 or N+2 or N+3, respectively, depending on the LRT. 
       FIG. 5 b    illustrates an example flow diagram of a method, according to one embodiment. The method may be performed by a UE or mobile station, for example. The method of  FIG. 5 b    may include, at  550 , receiving, from an eNB, a configuration for reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, such as DL transmission mode, system BW, subframe type, and/or used DL control region (e.g., PDCCH/EPDCCH specific). In an embodiment, the method may also include, at  560 , receiving DCI scheduling PDSCH or PUSCH and determining, based at least on a LRT, whether reduced processing time should be applied or not. In addition to the LRT, the determining of whether to apply reduced processing time may also be based on the used DL transmission mode, system BW, subframe type, DL control region as well as assignment content (number of MIMO layers, TBS size). The method may also include, at  570 , transmitting HARQ-ACK or PUSCH according to the timing determined based on the LRT. 
     Embodiments of the invention provide several advantages and/or technical improvements. For example, embodiments of the invention enable dynamic switching between operation with normal (subframe N+4) and reduced processing times (subframe N+2 or N+3), taking UEs limitations with respect to processing large transport blocks into account. Furthermore, embodiments allow for the reuse of legacy DCI formats (DL Assignments and UL grants). As a consequence, a UE is required to search only for the single DCI format and blind-detection complexity is the same as in legacy, and the LTE feature can be introduced with minimal changes to LTE specification and minimal implementation effort. Accordingly, embodiments of the invention can improve performance and throughput of network nodes including, for example, eNBs and UEs. As a result, the use of embodiments of the invention result in improved functioning of communications networks and their nodes. 
     In some embodiments, the functionality of any of the methods, processes, signaling diagrams, or flow charts described herein may be implemented by software and/or computer program code or portions of code stored in memory or other computer readable or tangible media, and executed by a processor. In some embodiments, the apparatus may be, included or be associated with at least one software application, module, unit or entity configured as arithmetic operation(s), or as a program or portions of it (including an added or updated software routine), executed by at least one operation processor. Programs, also called program products or computer programs, including software routines, applets and macros, may be stored in any apparatus-readable data storage medium and they include program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of an embodiment may be performed as routine(s), which may be implemented as added or updated software routine(s). Software routine(s) may be downloaded into the apparatus. 
     Software or a computer program code or portions of it may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium. 
     In other embodiments, the functionality may be performed by hardware, for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another embodiment, the functionality may be implemented as a signal, a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network. 
     According to an embodiment, an apparatus, such as a node, device, or a corresponding component, may be configured as a computer or a microprocessor, such as single-chip computer element, or as a chipset, including at least a memory for providing storage capacity used for arithmetic operation and an operation processor for executing the arithmetic operation. 
     One embodiment is directed to a method, which may include transmitting, by an eNB, a configuration for reduced processing time operation on a specific carrier to a UE. The method may also include performing a scheduling decision for the UE for PDSCH and/or PUSCH including the determination, based at least on a LRT, of whether reduced processing time should be applied or not. In addition to the LRT, the scheduling decision of whether to apply reduced processing time may also be based on the used DL transmission mode, system BW, subframe type, DL control region as well as assignment content (number of MIMO layers, TBS size). The method may further include preparing the related DCI and transmitting the DCI. The method may then include receiving PUSCH or DL HARQ-ACK information according to the selected processing time in the requested subframe given by N+4 or N+2 or N+3, respectively. 
     Another embodiment is directed to an apparatus including at least one processor, and at least one memory including computer program code. The at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to transmit a configuration for reduced processing time operation on a specific carrier to a UE, to perform a scheduling decision for the UE for PDSCH and/or PUSCH including the determination, at least based on the LRT, of whether reduced processing time should be applied or not, to prepare the related DCI, to transmit the DCI, and to receive PUSCH or DL HARQ-ACK information according to the selected processing time in the requested subframe given by N+4 or N+2 or N+3, respectively. 
     Another embodiment is directed to an apparatus including transmitting means for transmitting a configuration for reduced processing time operation on a specific carrier to a UE. The apparatus may also include performing means for performing a scheduling decision for the UE for PDSCH and/or PUSCH including the determination, at least based on the LRT, whether reduced processing time should be applied or not. In addition to the LRT, the scheduling decision of whether to apply reduced processing time may also be based on the used DL transmission mode, system BW, subframe type, DL control region as well as assignment content (number of MIMO layers, TBS size). The apparatus may further include preparing means for preparing the related DCI, transmitting means for transmitting the DCI, and receiving means for receiving PUSCH or DL HARQ-ACK information according to the selected processing time in the requested subframe given by N+4 or N+2 or N+3, respectively. 
     Another embodiment is directed to a method, which may include receiving, at a UE, a configuration for reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, such as DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). The method may also include receiving DCI scheduling PDSCH or PUSCH and determining, based at least on the LRT, whether reduced processing time should be applied or not. The determining may further include determining whether to apply reduced processing time based on the DL transmission mode, system BW, subframe type and/or used DL control region. The method may also include transmitting HARQ-ACK or PUSCH according to the timing determined based on the LRT. 
     Another embodiment is directed to an apparatus including at least one processor, and at least one memory including computer program code. The at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to receive a configuration for reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, such as DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). The apparatus may also be caused to receive DCI scheduling PDSCH or PUSCH and determine, based at least on a LRT, whether reduced processing time should be applied or not. The determination of whether to apply reduced processing time may be further based on the DL transmission mode, system BW, subframe type and/or used DL control region. The apparatus may be further caused to transmit HARQ-ACK or PUSCH according to the timing determined based on the LRT. 
     Another embodiment is directed to an apparatus including receiving means for receiving a configuration for reduced processing time operation on a specific carrier. The configuration may include the configuration of the LRT, such as DL transmission mode, system BW, subframe type and/or used DL control region (e.g., PDCCH/EPDCCH specific). The apparatus may also include receiving means for receiving DCI scheduling PDSCH or PUSCH and determining means for determining, based at least on a LRT, whether reduced processing time should be applied or not. The determination of whether to apply reduced processing time may be further based on the DL transmission mode, system BW, subframe type and/or used DL control region. The method may also include transmitting means for transmitting HARQ-ACK or PUSCH according to the timing determined based on the LRT. 
     One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. 
     List of Abbreviations 
     3GPP Third Generation Partnership Program 
     ACK Acknowledgement 
     AL Aggregation Level 
     C-RNTI Cell Radio Network Temporal Identifier 
     CRS Common Reference Signal 
     CSS Common Search Space 
     DCI Downlink Control Information 
     DL, D Downlink 
     DwPTS Downlink Pilot Time Slot 
     eNB Enhanced NodeB 
     EPDCCH Enhanced Physical Downlink Control Channel 
     FDD Frequency Division Duplexing 
     FDM Frequency Division Multiplexing 
     FS2 Frame Structure 2 
     GP Guard Period 
     HARQ Hybrid Automatic Retransmission request 
     LTE Long Term Evolution 
     OFDM Orthogonal Frequency Division Multiplexing 
     PCFICH Physical Control Format Indicator Channel 
     PDCCH Physical Downlink Control Channel 
     PDSCH Physical Downlink Shared Channel 
     PHICH Physical HARQ-ACK Indicator Channel 
     PSS Primary Synchronization Sequence 
     PUCCH Physical Uplink Control Channel 
     PUSCH Physical Uplink Shared Channel 
     RAN Radio Access Network 
     Rel Release 
     S Special Subframe 
     SI Study Item 
     SIB System Information Block 
     SSS Secondary Synchronization Sequence 
     TCP Transmission Control Protocol 
     TDD Time Division Duplexing 
     TDM Time Division Multiplexing 
     TSG Technical Steering Group 
     TTI Transmission Time Interval 
     UCI Uplink Control Information 
     UE User Equipment 
     UL, U Uplink 
     UpPTS Uplink Pilot Time Slot 
     WG Working Group 
     WI Work Item