Patent Description:
The following abbreviations are herewith defined, at least some of which are referred to within the following description.

In wireless communications networks, DL TBs may be carried on the PDSCH. A maximum of two TBs may be transmitted on PDSCH in one serving cell and in a subframe. "HARQ-ACK" may represent collectively the Positive Acknowledge ("ACK") and the Negative Acknowledge ("NAK"). ACK means that a TB is correctly received while NAK means a TB is erroneously received.

HARQ-ACK feedback bits corresponding to a PDSCH may be transmitted either on the PUCCH or on the PUSCH. For 3GPP Release <NUM> LTE FDD, HARQ-ACK feedback bits corresponding to PDSCH received in subframe n-<NUM> are transmitted in subframe n. See 3GPP TS36. Furthermore, for 3GPP Release <NUM> LTE TDD, HARQ-ACK feedback bits corresponding to PDSCH received in subframe n-k, where k belongs to the set K, are transmitted in subframe n. It should be noted that for LTE TDD, the elements in set K depends on the TDD UL/DL configuration, as well as the subframe index n, as shown in Table <NUM>.

The LTE TDD UL/DL configurations are shown in Table <NUM>. It should be noted that in Table <NUM>, "D" represents a DL subframe, "U" represents an UL subframe, and "S" represents a special subframe. The timing relationship between the subframe containing the PDSCH and the subframe containing the corresponding HARQ-ACK feedback may be referred to as the HARQ timing.

A frame structure for LTE FDD may be used in certain configurations. A radio frame of <NUM> milliseconds ("ms") may include <NUM> subframes, each of which is <NUM>. Each subframe further may include two slots, each of which is <NUM>. Within each slot, a number of OFDM symbols may be transmitted. The transmitted signal in each slot on an antenna port may be described by a resource grid comprising <MAT> subcarriers and <MAT> OFDM symbols, where <MAT> is number of RBs in the DL (which is dependent on the transmission bandwidth of a cell); <MAT> is the number of subcarriers in each RB; and each subcarrier occupies a certain frequency of size Δf. The values of <MAT>, Δf , and <MAT> may depend on a cyclic prefix as shown in Table <NUM>.

In certain configurations, an antenna port may refer to a logical antenna port (i.e., it may not necessarily refer to a physical antenna or antenna element). Mapping between an antenna port and physical antenna element(s) may be implementation specific. In other words, different devices may have a different mapping of physical antenna element(s) to the same antenna port. A receiving device may assume that the signals transmitted on the same antenna port go through the same channel. Moreover, a receiving device cannot assume signals transmitted on different antenna ports go through the same channel.

In certain configurations, carrier aggregation may be used such that more than one carrier may be aggregated by a UE to improve a transmission data rate. A UE may be able to aggregate a different number of carriers in the downlink and the uplink. For an RRC_CONNECTED UE (e.g., a UE in which an RRC connection has been established), each of the aggregated carriers may be a serving cell for the UE. Among the multiple aggregated serving cells, only one cell may be the primary cell while the other cells are secondary cells. In some configurations, PUCCH may be transmitted on both the primary cell and a secondary cell. Accordingly, PUCCH overhead may be offloaded from the primary cell to a secondary cell.

In some configurations, as part of carrier aggregation, aggregation of serving cells on a licensed spectrum and an unlicensed spectrum is supported for DL transmission. In such configurations, the serving cells in the unlicensed spectrum may only be secondary cells to a UE. The operation on the unlicensed carriers is assisted by the operation on the licensed carriers, hence the name licensed assisted access ("LAA").

In certain configurations, LAA includes UL support for LAA secondary cell operation in an unlicensed spectrum. LAA may also allow for fair coexistence between Wi-Fi and LAA and fair coexistence between different LAA systems. Coexistence measures may still allow efficient operation of all coexisting technologies. PUCCH transmission may be performed on unlicensed carriers to offload PUCCH overhead from licensed carriers to unlicensed carriers. In order to support dual connectivity for LAA operation (e.g., the network node hosting the licensed carriers and the network node hosting the unlicensed carriers are geographically non-collocated and connected with non-ideal backhaul), PUCCH transmission in unlicensed carriers may be supported.

In various configurations, if there are a large number of carriers in the unlicensed spectrum and a limited number of carriers in licensed spectrum, it may be useful to offload some UCI from the licensed spectrum to the unlicensed spectrum. In some situations, the channel quality of the unlicensed spectrum may be worse than the channel quality of the licensed spectrum and there may be unpredictable channel access of unlicensed spectrum. Accordingly, HARQ-ACK corresponding to PDSCH in licensed spectrum may be transmitted in the licensed spectrum. Furthermore, HARQ-ACK transmitted in the uplink on an unlicensed spectrum may correspond to PDSCH transmitted on the unlicensed spectrum. This may be facilitated by eNB configuration.

As may be appreciated, LBT may be performed before transmissions on an unlicensed spectrum to facilitate fair coexist with other wireless systems on the same unlicensed spectrum. Moreover, for HARQ-ACK transmissions on an unlicensed carriers, LBT may be performed before actual HARQ-ACK transmissions. After an LBT is successful, a UE may start a HARQ-ACK transmission in the LAA uplink subframe according to a DL HARQ timing relationship. In contrast, HARQ-ACK transmission corresponding to DL transmission in an LAA secondary cell may not be transmitted on an LAA secondary cell uplink in response to a failed LBT for uplink channel access. Not transmitting a HARQ-ACK transmission may reduce DL throughput performance.

<NPL>, describes contention window adaption rules relating to ACK/NACK.

<NPL>, describes methods related to UL control signaling.

These 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.

<FIG> depicts an embodiment of a wireless communication system <NUM> for data acknowledgment. In one embodiment, the wireless communication system <NUM> includes remote units <NUM> and base units <NUM>. Even though a specific number of remote units <NUM> and base units <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM> and base units <NUM> may be included in the wireless communication system <NUM>.

The base units <NUM> may be distributed over a geographic region. In certain embodiments, a base unit <NUM> may also be referred to as an access point, an access terminal, a base, a base station, a Node-B, an eNB, a Home Node-B, a relay node, a device, or by any other terminology used in the art. The base units <NUM> are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding base units <NUM>.

In one implementation, the wireless communication system <NUM> is compliant with the LTE of the 3GPP protocol, wherein the base unit <NUM> transmits using an OFDM modulation scheme on the DL and the remote units <NUM> transmit on the UL using a SC-FDMA scheme. More generally, however, the wireless communication system <NUM> may implement some other open or proprietary communication protocol, for example, WiMAX, among other protocols.

In one embodiment, a base unit <NUM> may transmit to a device (e.g., remote unit <NUM>). In such an embodiment, the base unit <NUM> may determine a response window having multiple subframes for receiving an acknowledgement corresponding to the data. The base unit <NUM> may receive the acknowledgement from the device within the response window. Accordingly, the acknowledgement may be received during a time period longer than a single subframe to facilitate multiple attempts by the device to transmit the acknowledgement to the base unit <NUM> because of times in which LBT may be unsuccessful.

In another embodiment, a remote unit <NUM> may receive data from a device (e.g., base unit <NUM>). In such an embodiment, the remote unit <NUM> may determine a response window having multiple subframes for transmitting an acknowledgement corresponding to the data. The remote unit <NUM> may transmit the acknowledgement within the response window. Thus, the acknowledgement may be transmitted during a time period longer than a single subframe to facilitate multiple attempts by the remote unit <NUM> to transmit the acknowledgement to the device because of times in which LBT may be unsuccessful.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for transmitting a data acknowledgment. The apparatus <NUM> includes one embodiment of the remote unit <NUM>. Furthermore, the remote unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. In some embodiments, the input device <NUM> and the display <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit <NUM> may not include any input device <NUM> and/or display <NUM>. In various embodiments, the remote unit <NUM> may include one or more of the processor <NUM>, the memory <NUM>, the transmitter <NUM>, and the receiver <NUM>, and may not include the input device <NUM> and/or the display <NUM>.

In certain embodiments, the processor <NUM> may determine a response window having multiple subframes for transmitting an acknowledgement corresponding to the data.

For example, the response window may be considered a HARQ-ACK feedback opportunity window for HARQ-ACK transmission in the UL of an unlicensed carrier. In one embodiment, for a data (e.g., in the form of a PDSCH TB) received in a subframe n, its corresponding HARQ-ACK may be fed back in one subframe within the HARQ-ACK feedback opportunity window. In certain embodiments, the duration of the HARQ-ACK feedback opportunity window may be denoted as M subframes. In some embodiments, the value of M may be configured by higher layer signaling (e.g., RRC signaling) or fixed in a specification. Therefore, for a PDSCH transmitted in a subframe, its corresponding HARQ-ACK transmission may have a maximum of M transmission opportunities. In various embodiments, a HARQ-ACK feedback opportunity window may include a set of M consecutive subframes, while other embodiments may include a set of M non-consecutive subframes. In some embodiments, all or only part of the set of M subframes may be non-consecutive. For example, at least two of the subframes of the set of M subframes may be consecutive, while at least one subframe of the set of M subframes may not be consecutive with the at least two consecutive subframes.

In certain embodiments, LBT is performed by the remote unit <NUM> using the processor <NUM> before the possible transmission in each of the subframes within the HARQ-ACK feedback opportunity window. In some embodiments, within a HARQ-ACK feedback opportunity window corresponding to a HARQ-ACK, the first subframe for which LBT is successful is used to transmit one or more HARQ-ACKs. For example, assuming LBT for the first (N-<NUM>)th subframes in the HARQ-ACK feedback opportunity window fails and LBT for the Nth subframe is successful, the remote unit <NUM> may transmit the HARQ-ACK in the Nth subframe within the HARQ-ACK feedback opportunity window. If LBT is not successful for any of the M subframes within the HARQ-ACK feedback opportunity window corresponding to a HARQ-ACK, the remote unit <NUM> may not transmit that HARQ-ACK.

In certain embodiments, for an LBT procedure, some parameters may be generated (e.g., a random backoff counter for CCA checks) by the processor <NUM>. Taking the random backoff counter for CCA checks as an example, in one embodiment, the random backoff counter may be generated once for a HARQ-ACK feedback opportunity window. In other words, for a HARQ-ACK feedback and its corresponding HARQ-ACK feedback opportunity window, a random backoff counter for CCA checks may be generated (e.g., with value x<NUM>) for the LBT for the first subframe within the HARQ-ACK feedback opportunity window. If the LBT fails for the first subframe within the HARQ-ACK feedback opportunity window (e.g., the random backoff counter does not reach to <NUM> but reaches to a value x<NUM> <= x<NUM>), the remote unit <NUM> continues the LBT procedure with the random backoff counter value x<NUM> for the second subframe within the HARQ-ACK feedback opportunity window, and so on for the rest of the subframes within the HARQ-ACK feedback opportunity window. Still using the random backoff counter for CCA checks as an example, in another embodiment, the random backoff counter is newly generated for each LBT procedure for each of the M subframes within the HARQ-ACK feedback opportunity window. In other words, the random backoff counter value for a second subframe within the HARQ-ACK feedback opportunity window is independently generated from the random backoff counter value for a first subframe within the HARQ-ACK feedback opportunity window.

In some embodiments, for a HARQ-ACK transmission corresponding to data received in a subframe n, a set of M subframes for the HARQ-ACK feedback opportunity window corresponding to the HARQ-ACK transmission may be defined. In one embodiment, for a HARQ-ACK transmission corresponding to data received in a subframe n, its corresponding HARQ-ACK feedback opportunity window includes a set of consecutive subframes (e.g., {n+x, n+x+<NUM>,. , n+x+M-<NUM>}). In some embodiments, the value of x equals <NUM>, while in other embodiments the value of x is equal to any suitable time period of delay from the subframe n where data is received to a first subframe in the HARQ-ACK feedback opportunity window. In another embodiment, for a HARQ-ACK transmission corresponding to data received in a subframe n, its corresponding HARQ-ACK feedback opportunity window includes a set of non-consecutive subframes (e.g., {n+x, n+x+<NUM>,. , n+x+<NUM>-<NUM>}). In one embodiment, the value of x equal <NUM>, while in other embodiments the value of x is equal to any suitable time period of delay from the subframe n where data is received to a first subframe in the HARQ-ACK feedback opportunity window. Furthermore, in one embodiment for non-consecutive subframes that make up the HARQ-ACK feedback opportunity window, a TDD UL/DL configuration defining the subframe usage is indicated from a base unit <NUM> to a remote unit <NUM>. Based on this, the remote unit <NUM> may know the uplink subframe positions that may be used to define the HARQ-ACK feedback opportunity window. In another embodiment for non-consecutive subframes that make up the HARQ-ACK feedback opportunity window, a bitmap defining M subframes from the available uplink subframes to make up the HARQ-ACK feedback opportunity window is indicated from a base unit <NUM> to a remote unit <NUM>. Based on this, the remote unit <NUM> may know the subframe positions used to define the HARQ-ACK feedback opportunity window.

In certain embodiments, the HARQ-ACK feedback opportunity window for multiple different HARQ-ACKs corresponding to data received in multiple different subframes may overlap. Accordingly, multiple HARQ-ACKs may be transmitted in a single subframe (e.g., the same subframe). In various embodiments, to transmit the multiple HARQ-ACKs in one subframe, different HARQ-ACK transmission schemes may be used. For example, the multiple HARQ-ACKs may be compressed (e.g., by time domain bundling or spatial bundling) to reduce the HARQ-ACK payload size. In some embodiments, the multiple HARQ-ACKs may not be bundled. For example, PUCCH formats 1a/1b/<NUM>/<NUM>/<NUM>/<NUM> defined by 3GPP LTE may be used to transmit the multiple HARQ-ACKs in a single subframe. As discussed, by transmitting HARQ-ACKs during the HARQ-ACK feedback opportunity window having more than one subframe, HARQ-ACKs may have a high opportunity for being transmitted to a base unit <NUM>, which consequently improves the DL throughput performance compared to conditions where HARQ-ACKs have only one possible subframe for transmission.

In some embodiments, the memory <NUM> stores data relating to an indication to be provided to another device.

As another, nonlimiting, example, the display <NUM> may include a wearable display such as a smart watch, smart glasses, a heads-up display, or the like.

The transmitter <NUM> is used to provide UL communication signals to the base unit <NUM> and the receiver <NUM> is used to receive DL communication signals from the base unit <NUM>. In one embodiment, the transmitter <NUM> is used to transmit an acknowledgement to the base unit <NUM> within a response window. In certain embodiments, the receiver <NUM> may be used to receive data.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for receiving a data acknowledgment. The apparatus <NUM> includes one embodiment of the base unit <NUM>. Furthermore, the base unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. As may be appreciated, the processor <NUM>, the memory <NUM>, the input device <NUM>, and the display <NUM> may be substantially similar to the processor <NUM>, the memory <NUM>, the input device <NUM>, and the display <NUM> of the remote unit <NUM>, respectively. In certain embodiments, the processor <NUM> may be used to determine a response window having multiple subframes for receiving an acknowledgement corresponding to the data from a remote unit <NUM>.

The transmitter <NUM> is used to provide DL communication signals to the remote unit <NUM> and the receiver <NUM> is used to receive UL communication signals from the remote unit <NUM>. In certain embodiments, the transmitter <NUM> is used to transmit data on a carrier to a remote unit <NUM>. In one embodiment, the receiver <NUM> is used to receive an acknowledgement from a remote unit <NUM> during a response window. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the base unit <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>.

<FIG> illustrates one embodiment of a response window for transmitting a data acknowledgment. Specifically, communications <NUM> include UL/DL data structure <NUM> for a primary cell and UL/DL data structure <NUM> for an LAA secondary cell. HARQ-ACKs <NUM>, <NUM>, <NUM>, and <NUM> correspond to PDSCH DL data in subframes <NUM>, <NUM>, <NUM>, and <NUM> of the UL/DL data structure <NUM>, respectively. In this embodiment, M is configured to <NUM>. Therefore, for a HARQ-ACK corresponding to data received in subframe n, its corresponding HARQ-ACK feedback opportunity window (e.g., response window) includes a set of <NUM> consecutive subframes {n+<NUM>, n+<NUM>, n+<NUM>, n+<NUM>}. Accordingly, for PDSCH in subframe <NUM> of the UL/DL data structure <NUM>, the corresponding HARQ-ACK <NUM>, may be transmitted in a window that includes subframes <NUM>, <NUM>, <NUM>, <NUM> of the UL/DL data structure <NUM>. LBTs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are performed prior to each potential UL in the UL/DL data structure <NUM>. If LBT <NUM> for transmission in subframe <NUM> of the UL/DL data structure <NUM> is successful, HARQ-ACK <NUM> is transmitted in subframe <NUM>. If LBT <NUM> fails, the remote unit <NUM> performs LBT <NUM> for subframe <NUM> and transmit HARQ-ACKs <NUM> and <NUM> in subframe <NUM> of the UL/DL data structure <NUM> if the LBT for transmission in subframe <NUM> is successful, and so forth. In one embodiment, each of the LBTs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> for possible HARQ-ACK transmission in a subframe m may be performed in subframe m. In another embodiment, each of the LBTs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> for possible HARQ-ACK transmission in a subframe m may be performed in subframe m-<NUM>.

<FIG> illustrates another embodiment of a response window for transmitting a data acknowledgment. Specifically, communications <NUM> again include the UL/DL data structure <NUM> for a primary cell and the UL/DL data structure <NUM> for an LAA secondary cell. In this embodiment, it is assumed that LBTs <NUM>, <NUM>, and <NUM> for transmission in subframes <NUM>, <NUM> and <NUM> are not successful (e.g., due to the channel being occupied by other LAA nodes or Wi-Fi). Accordingly, no HARQ-ACKs are transmitted in subframes <NUM>, <NUM>, and <NUM> (e.g., subframes <NUM>, <NUM>, and <NUM>). Moreover, LBT <NUM> for transmission in subframe <NUM> is successful. Therefore, the remote unit <NUM> may transmit HARQ-ACKs <NUM>, <NUM>, <NUM>, and <NUM> in subframe <NUM> because subframe <NUM> is part of the response window for all HARQ-ACKs <NUM>, <NUM>, <NUM>, and <NUM>. If the LBT <NUM> in subframe <NUM> were to fail, then the remote unit <NUM> would no longer attempt to transmit HARQ-ACK <NUM> because four transmission opportunities for HARQ-ACK <NUM> would have already been made (e.g., the response window would be expired). From the perspective of a base unit <NUM>, the base unit <NUM> may expect to receive HARQ-ACK <NUM> in any subframe within the response window (e.g., subframe <NUM> to subframe <NUM>). If the base unit <NUM> cannot detect the HARQ-ACK <NUM> corresponding to the LAA PDSCH in subframe <NUM> in any subframes within the response window, the base unit <NUM> may retransmit the PDSCH in a later DL transmission. If any HARQ-ACK <NUM>, <NUM>, <NUM>, and <NUM> has been transmitted within its corresponding response window, then the remote unit <NUM> may not perform LBT and may not retransmit the respective HARQ-ACK in the remaining subframes within its corresponding response window.

<FIG> is a schematic flow chart diagram illustrating one embodiment of a method <NUM> for receiving a data acknowledgment. In some embodiments, the method <NUM> is performed by an apparatus, such as the base unit <NUM>. In certain embodiments, the method <NUM> 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 <NUM> may include transmitting <NUM> data to a device (e.g., remote unit <NUM>). The method <NUM> may also include determining <NUM> a response window including multiple subframes for receiving an acknowledgement corresponding to the data. In one embodiment, the multiple subframes may be consecutive subframes, while in another embodiment, the multiple subframes may be non-consecutive subframes. In various embodiments, a number of subframes of the response window is fixed or configured by higher layer signaling. In certain embodiments, determining <NUM> the response window may include determining a time period of delay from the subframe where the data is transmitted to a first subframe within the response window. The method <NUM> may include receiving <NUM> the acknowledgement within the response window, and the method <NUM> may end. In certain embodiments, the acknowledgment includes a positive acknowledgement ("ACK") or a negative acknowledgement ("NAK").

<FIG> is a schematic flow chart diagram illustrating one embodiment of a method <NUM> for transmitting a data acknowledgment. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> 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 <NUM> may include receiving <NUM> data from a device (e.g., base unit <NUM>). The method <NUM> may also include determining <NUM> a response window including multiple subframes for transmitting an acknowledgement corresponding to the data. In one embodiment, the multiple subframes may be consecutive subframes, while in another embodiment, the multiple subframes may be non-consecutive subframes. In various embodiments, a number of subframes of the response window is fixed or configured by higher layer signaling. In certain embodiments, determining <NUM> the response window may include determining a time period of delay from the subframe where the data is received to a first subframe within the response window. The method <NUM> may include transmitting <NUM> the acknowledgement within the response window, and the method <NUM> may end.

In certain embodiments, the acknowledgment includes a positive acknowledgement ("ACK") or a negative acknowledgement ("NAK"). In one embodiment, the method <NUM> may include performing a LBT before transmitting the acknowledgement. In some embodiments, transmitting <NUM> the acknowledgement within the response window includes transmitting the acknowledgement in a subframe within the response window immediately following a subframe in which LBT is successful. In various embodiments, transmitting <NUM> the acknowledgement within the response window includes transmitting the acknowledgement in a subframe within the response window in which LBT is successful.

In one embodiment, the method <NUM> may include generating a random backoff counter for a LBT in a first subframe within the response window and continuing to count down the random backoff counter for the LBT in a second subframe within the response. In some embodiments, determining <NUM> the response window includes determining multiple response windows with each response window of the multiple response windows corresponding to a respective portion of the data, and transmitting <NUM> an acknowledgement for each respective portion of the data within a corresponding response window of the multiple response windows. In certain embodiments, the method <NUM> includes transmitting the acknowledgement for each respective portion of the data together in a subframe after successfully performing a LBT. In various embodiments, the method <NUM> includes transmitting a common acknowledgement for each respective portion of the data (e.g., one acknowledgement that collectively responds to each portion of the data) in a subframe after successfully performing a LBT.

While embodiments described herein may be described for HARQ-ACK transmission or reception on a carrier of an unlicensed spectrum. The disclosed embodiments may be equally applicable for HARQ-ACK transmission or reception on a carrier of a licensed spectrum.

Claim 1:
A method performed by a remote unit (<NUM>) in a 3GPP system, the method comprising:
receiving (<NUM>) data from a device (<NUM>), wherein the data is first data and is in the form of a first Physical Downlink Shared Channel, PDSCH, transport block, TB;
receiving second data in the form of a second PDSCH TB at a second time which is after the time when the first PDSCH TB is received;
determining (<NUM>) a first response window comprising a plurality of subframes as a plurality of transmission opportunities for transmitting hybrid automatic repeat request, HARQ, acknowledgements corresponding to the first PDSCH TB;
determining (<NUM>) a second response window comprising a plurality of subframes as a plurality of transmission opportunities for transmitting HARQ acknowledgements corresponding to the second PDSCH TB, wherein at least one subframe of the second response window is a subframe of the first response window;
performing listen-before-talk, LBT, before the possible transmission of a HARQ acknowledgement for the first PDSCH TB in each of the plurality of subframes within the first response window until successful;
performing LBT before the possible transmission of a HARQ acknowledgement for the second PDSCH TB in each of the plurality of subframes within the second response window until successful; and
transmitting (<NUM>), to the device (<NUM>), both the HARQ-ACK corresponding to the first PDSCH TB and the HARQ-ACK corresponding to the second PDSCH TB in the same subframe if the LBT for the first PDSCH TB fails for a first subframe of the first response window and the LBT for the second PDSCH TB is successful for said same subframe.