Patent Description:
In the current networks, traffic of mobile terminals (smartphones and feature phones) occupies most of network resources. Furthermore, traffic used by mobile terminals tends to be continuously increased in the future.

In contrast, with the development of Internet of things (IoT) services (for example, transportation systems, smart meters, monitoring systems for devices, and the like), there is a demand for coping with services having various requirements. Thus, in the communication standards for the fifth generation mobile communication (<NUM> or New Radio (NR)), in addition to the standard technologies (for example, Non Patent Literatures <NUM> to <NUM>) of the fourth generation mobile communication (<NUM>), there is a demand for a technology that implements high-data-rate, high-capacity, and low-latency communication. Furthermore, regarding the fifth generation communication standards, technical studies are being conducted in 3GPP working groups (for example, TSG-RAN WG1, TSG-RAN WG2, and the like) (Non Patent Literatures <NUM> to <NUM>).

Furthermore, in a wireless communication system (for example, long term evolution (LTE) or <NUM>), a technology of hybrid automatic repeat request (HARQ) is used to implement efficient data transmission. In HARQ, a receiving device requests a transmitting device to retransmit data that is not correctly decoded in a process performed in a protocol hierarchy of, for example, layer <NUM> in LTE or the like. When the transmitting device is requested to retransmit the data, the transmitting device transmits the retransmission data associated with the retransmission request. In the receiving device, data is decoded by combining the original data that is not correctly decoded with the retransmission data. Consequently, high efficiency and high accuracy retransmission control is implemented.

Transmission timing of feedback of HARQ is designated by, for example, control information. Namely, timing at which an ACK or a NACK with respect to downlink data is fed back is designated by information in DCI format 1_0 transmitted by, for example, a physical downlink control channel (PDCCH) that is a control channel for a downlink. The timing of the feedback is designated by the number of slots from, for example, the slot in which the data is transmitted to the slot in which an ACK or a NACK is transmitted.

<CIT> relates to an HARQ-ACK transmission method and apparatus. The method comprises: determining, by means of a predefinition or a signaling indication, an HARQ-ACK to be transmitted and a resource location on an unlicensed carrier transmitting the HARQ-ACK; executing listen before talk (LBT) on the unlicensed carrier; and after the LBT is successfully executed, transmitting the HARQ-ACK on the resource location.

WO <NUM>/<NUM> A1 relates to a network node configured to operate in an unlicensed communication spectrum. The network node includes a processor and a transceiver, the processor being configured to determine an identifier for subframe for an uplink control channel transmission, the uplink control channel transmission comprising at least HARQ-ACK information, wherein the subframe for the uplink control channel transmission is a function of at least an index of a subframe in a downlink control channel that is configured to transmit the identifier, and the identifier. The transceiver is configured to transmit the identifier in the downlink control channel.

Incidentally, HARQ is not only applicable to communication that uses a licensed band (hereinafter, simply referred to as an "L band") for which a license is needed to use in wireless communication, but also applicable to communication that uses an unlicensed band (hereinafter, simply referred to as a "U band") for which a license is not needed to use in wireless communication. In general, because the U band is shared by a plurality of wireless communication systems, interference between wireless communication systems may possibly occur in communication performed by the U band. Thus, when communication is performed by using the U band, a listen before talk (LBT) process is performed before a signal is transmitted, and the signal is transmitted when transmission is not performed by another device and the U band is idle. In contrast, transmission of a signal is suspended when transmission is performed by the other device and the U band is busy.

However, there is a problem in that, when HARQ is used in the U band, transmission efficiency is decreased. Specifically, for example, when a burst containing a plurality of consecutive slots is transmitted by using the U band, the feedback timing of an ACK or a NACK with respect to data in each of the slots included in the burst is designated by control information. Consequently, an ACK or a NACK is transmitted by the designated feedback timing. Accordingly, because the U band is used to transmit an ACK or a NACK at the feedback timing, another transmission using the U band is not performed.

In contrast, an LBT process is performed before the next burst is transmitted and, when the U band becomes idle, burst transmission is performed. Consequently, for example, if a period of time in which the U band is busy continues, there may be a case in which the execution timing of the next burst transmission and the feedback timing described above are overlapped. In this case, a part of the burst is transmitted before the feedback timing and the rest part of the burst is transmitted after the LBT process is again performed after the feedback timing.

As a result, transmission of the data is intermittent and the number of times of the LBT processes is increased, whereby the transmission efficiency of data is decreased. In other words, continuous transmission of burst is limited due to feedback of the ACK or the NACK and throughput is thus decreased.

Accordingly, the present invention has been conceived in light of the circumstances described above and an object thereof is to provide a base station device, a terminal device, and a wireless communication system that can suppress a decrease in transmission efficiency.

The invention is defined in the independent claims, to which reference should now be made. Advantageous developments are set out in the dependent claims.

According to an aspect of the base station device, the terminal device, and the wireless communication system, an advantage is provided in that it is possible to suppress a decrease in transmission efficiency.

Preferred embodiment of a base station device, a terminal device, and a wireless communication system will be described in detail below with reference to the accompanying drawings. Furthermore, the present invention is not limited to the embodiments.

<FIG> is a block diagram illustrating a configuration of a base station device <NUM> according to an embodiment. The base station device <NUM> performs transmission using a U band. The base station device <NUM> illustrated in <FIG> includes a network interface unit (hereinafter, simply referred to as a "network I/F unit") <NUM>, a processor <NUM>, a wireless communicating unit <NUM>, a LBT processing unit <NUM>, and a memory <NUM>. In <FIG>, only the processing units related to transmission performed by using a U band is illustrated; however, the base station device <NUM> may also perform transmission by using not only the U band but also an L band.

The network I/F unit <NUM> is an interface that is connected to a communication device constituting, for example, a core network or that is connected to another base station device. The network I/F unit <NUM> receives information that is needed to generate a signal of a control channel or information that is needed to generate a signal of a data channel from the communication device that constitutes a core network.

The processor <NUM> includes, for example, a central processing unit (CPU), a field programmable gate array (FPGA) or a digital signal processor (DSP), and performs overall control of the base station device <NUM>. Specifically, the processor <NUM> includes a control channel generating unit <NUM>, a data channel generating unit <NUM>, a mapping unit <NUM>, and a control unit <NUM>.

When burst transmission using the U band is performed, the control channel generating unit <NUM> generates a control channel of each of a plurality of slots included in the burst. Specifically, the control channel generating unit <NUM> generates, for each slot, a control channel that includes allocation information on a wireless resource including one or both of the frequency domain and the time domain, modulation scheme, and an encoding rate with respect to a data channel of each of the slots and that includes information (hereinafter, simply referred to as a "FB timing information") that designates feedback timing of an ACK or a NACK with respect to the data channel of each of the slots.

Here, the control channel may also designate, by including information related to the number of transport blocks (TBs) of data included in each of the slots, to generate an ACK or a NACK in units of TBs. Furthermore, the control channel may also designate, by including information related to the number of code block groups (CBGs) constituting the TB, to generate an ACK or a NACK in units of CBGs. When an ACK or a NACK associated with each of the plurality of TBs or CBGs is fed back, a retransmission process is performed in units of feedback of the ACKs or the NACKs. In a description below, a description will be given with the assumption that a single TB is transmitted per slot and the ACK or the NACK are fed back in units of TBs. In a case in which a plurality of TBs or CBGs are transmitted per slot and a plurality of ACKs or NACKs are fed back, in a description below, for example, "a slot" described in the "a slot associated with a NACK" may also be replaced with "a TB" or "a CBG".

At this time, regarding a predetermined number of slots from the top of a burst, the control channel generating unit <NUM> includes FB timing information indicating the number of slots from each of the slots to the feedback timing in the control channel. Namely, regarding the predetermined number of slots from the top of the burst, the control channel generating unit <NUM> generates, for each slot, the FB timing information that designates a common slot located after the end of the burst transmission as a feedback timing. Furthermore, regarding the rearward slots except for the predetermined number of slots from the top of the burst, the control channel generating unit <NUM> includes, in the control channel, the FB timing information that instructs to transmit ACKs or NACKs at the same time of the feedback with respect to the next burst. Namely, regarding the rearward slots in the burst, the control channel generating unit <NUM> generates FB timing information that instructs to collectively feed back the ACKs or the NACKs together with a next burst without specifying the slots that are used to feed back the ACKs or the NACKs.

When the burst transmission using the U band is performed, the data channel generating unit <NUM> generates a data channel of each of the plurality of slots included in a burst. Specifically, the data channel generating unit <NUM> generates, for each slot, a data channel including transmission data.

The mapping unit <NUM> generates the burst by mapping both of the control channel generated by the control channel generating unit <NUM> and the data channels generated by the data channel generating unit <NUM> onto the plurality of slots. Then, the mapping unit <NUM> temporarily holds the generated burst and transmits the burst from the wireless communicating unit <NUM> at the timing instructed by the LBT processing unit <NUM>.

When a code book including the ACK or the NACK for each slot is received by the wireless communicating unit <NUM>, the control unit <NUM> instructs the data channel generating unit <NUM> to generate transmission data of the slot associated with the NACK and retransmit the transmission data via the mapping unit <NUM>. Namely, because, in the code book, both of an ACK related to the slot that is correctly decoded in the terminal device that is the transmission destination of the burst and a NACK related to the slot that is not correctly decoded are included, the control unit <NUM> performs retransmission control of the transmission data of the slot that is associated with the NACK.

The wireless communicating unit <NUM> performs a predetermined wireless transmission process, such as digital/analog (D/A) conversion and up-conversion, on the transmission data or the retransmission data output from the mapping unit <NUM>, and then, transmits the processed data via an antenna. Furthermore, the wireless communicating unit <NUM> receives the code book including the ACK or the NACK for each slot and performs predetermined wireless reception processes, such as down-conversion and analog/digital (A/D) conversion.

The LBT processing unit <NUM> performs the LBT process on the U band via the wireless communicating unit <NUM>. Namely, the LBT processing unit <NUM> judges, by measuring received power of the U band, whether the other device transmits a signal by using the U band. Then, when the received power of the U band is greater than or equal to a predetermined threshold, the LBT processing unit <NUM> judges that the other device is transmitting a signal and the U band is busy, whereas, when the received power of the U band is less than the predetermined threshold, the LBT processing unit <NUM> judges that the other device is not transmitting the signal and the U band is idle. When the U band is idle, the LBT processing unit <NUM> instructs the mapping unit <NUM> to transmit the transmission data or the retransmission data.

The memory <NUM> includes, for example, a random access memory (RAM) or a read only memory (ROM), or the like and stores information that is used by the processor <NUM> to perform processes.

<FIG> is a block diagram illustrating a configuration of a terminal device <NUM> according to an embodiment. The terminal device <NUM> receives a signal in the U band and transmits ACKs or NACKs. The terminal device <NUM> illustrated in <FIG> includes a wireless communicating unit <NUM>, a processor <NUM>, a LBT processing unit <NUM>, and a memory <NUM>. In <FIG>, only the processing units related to performing communication using the U band are illustrated; however, the terminal device <NUM> may also perform communication not only using the U band, but also using the L band.

The wireless communicating unit <NUM> receives a signal in the U band transmitted from the base station device <NUM> and performs the predetermined wireless reception processes, such as down-conversion and A/D conversion, on the received signal. Furthermore, the wireless communicating unit <NUM> performs predetermined wireless transmission processes, such as D/A conversion and up-conversion, on the code book that includes the ACKs or the NACKs related to the received signal and transmits the processed data via the antenna.

The processor <NUM> includes, for example, a CPU, an FPGA, a DSP, or the like and performs overall control of the terminal device <NUM>. Specifically, the processor <NUM> includes a control channel reception processing unit <NUM>, a data channel reception processing unit <NUM>, a code book generating unit <NUM>, a data channel generating unit <NUM>, and a mapping unit <NUM>.

The control channel reception processing unit <NUM> demodulates and decodes the control channel in each of the slots in the received signal in the U band. Then, the control channel reception processing unit <NUM> outputs the allocation information included in the control channel to the data channel reception processing unit <NUM> and outputs the FB timing information to the code book generating unit <NUM>.

The data channel reception processing unit <NUM> demodulates and decodes a data channel in each of the slots in the received signal in the U band in accordance with the allocation information. Namely, because the allocation information output from the control channel reception processing unit <NUM> includes information, such as a modulation scheme and an encoding rate of a data channel, the data channel reception processing unit <NUM> performs the reception process on the data channel by referring to the allocation information. Then, the data channel reception processing unit <NUM> notifies the code book generating unit <NUM> of the status indicating whether the data channel for each slot has been correctly decoded. Namely, the data channel reception processing unit <NUM> notifies the code book generating unit <NUM> of the decoding judgement result of, for example, for each slot.

The code book generating unit <NUM> generates, for each slot, an ACK or a NACK indicating a decoding result of the data channels and generates a code book including the ACKs or the NACKs of the plurality of slots. At this time, the code book generating unit <NUM> generates the code book associated with the plurality of slots that are instructed to feed back the ACKs or the NACKs by using the common slot in accordance with the FB timing information. Accordingly, the code book generating unit <NUM> generates the code book including the ACKs or the NACKs related to a predetermined number of slots from the top of a single burst. Then, the code book generating unit <NUM> temporarily holds the ACKs or the NACK related to the rearward slots in the burst and generates, when the next burst is received, a code book that includes both of the ACKs or the NACKs that are being held and the ACKs or the NACKs that are associated with the next burst. In other words, regarding the slots that are instructed by the FB timing information to collectively feed back the ACKs or the NACKs together with the next burst, the code book generating unit <NUM> generates another code book when the next burst is received.

In this way, the code book generating unit <NUM> collectively generates the code book related to the rearward slots in the burst together with the next burst, and the reason for this is as follows. Namely, a certain amount of processing time is needed for the data channel reception processing unit <NUM> to perform the reception process on the data channel for each slot and needed for the code book generating unit <NUM> to generate a code book. Consequently, it is difficult to feed back, to the base station device <NUM>, the code book including the ACKs or the NACKs related to the rearward slots in the burst immediately after the completion of the reception of the entirety of the burst. In contrast, regarding the predetermined number of slots from the top of the burst, it is possible to generate ACKs or NACKs during reception of the rearward slots in the burst and it is possible to feed back, to the base station device <NUM>, the code book including these ACKs or NACKs immediately after the completion of the entirety of the burst.

Thus, regarding the predetermined number of slots from the top of the burst, the FB timing information specifies the slots located immediately after the completion of the reception of the entirety of the burst as the slots for feeding back of ACKs or NACKs. Consequently, the code book generating unit <NUM> generates a code book including the ACKs or the NACKs related to the predetermined number of slots from the top of the burst. In contrast, regarding the rearward slots in the burst, the FB timing information designates to collectively feed back ACKs or NACKs together with the next burst. Consequently, the code book generating unit <NUM> holds the ACK or the NACK related to the rearward slots in the burst until the next burst is received, and then, collectively generates a code book together with the ACKs or the NACKs related to the next burst.

The data channel generating unit <NUM> generates a data channel including transmission data when the data channel generating unit <NUM> transmits data to the base station device <NUM> by using the U band.

The mapping unit <NUM> generates a transmission signal in an uplink by mapping both of the code book generated by the code book generating unit <NUM> and the data channels generated by the data channel generating unit <NUM>. Then, the mapping unit <NUM> temporarily holds the generated transmission signal and transmits the transmission signal from the wireless communicating unit <NUM> at the timing instructed by the LBT processing unit <NUM>.

The LBT processing unit <NUM> performs the LBT process on the U band via the wireless communicating unit <NUM>. Namely, the LBT processing unit <NUM> judges, by measuring the received power of the U band, whether the other device is transmitting a signal by using the U band. Then, when the received power of the U band is greater than or equal to the predetermined threshold, the LBT processing unit <NUM> judges that the other device is transmitting the signal and the U band is busy, whereas, when the received power of the U band is less than the predetermined threshold, the LBT processing unit <NUM> judges that the other device does not currently transmit a signal and the U band is idle. When the U band is idle, the LBT processing unit <NUM> instructs the mapping unit <NUM> to transmit the transmission signal.

The memory <NUM> includes, for example, a RAM, a ROM, or the like and stores information that is used by the processor <NUM> to execute processes.

In the following, an operation of the base station device <NUM> according to an embodiment will be described with reference to the flowchart illustrated in <FIG>. In a description below, an operation performed in a case in which a burst including a plurality of slots is transmitted from the base station device <NUM> to the terminal device <NUM> will be described.

The data transmitted from the base station device <NUM> to the terminal device <NUM> is acquired from a core network by, for example, the network I/F unit <NUM>. Then, a data channel is generated, for each slot, from the transmission data obtained from the core network by the data channel generating unit <NUM> (Step S101).

Furthermore, a control channel that includes allocation information and the FB timing information on the data channel is generated by the control channel generating unit <NUM> for each slot. Specifically, it is determined whether the individual slots are the slots from the top to the predetermined slot in the burst or whether the individual slots are the slots after the predetermined slot (Step S102). Then, when the target slots are the slots from the top to the predetermined slot in the burst (No at Step S102), the FB timing information that specifies the number of slots up to the feedback timing with respect to the subject slot is generated and the control channel that includes the subject FB timing information is generated (Step S103). At this time, FB timing information that specifies the number of slots up to the slot immediately after, for example, completion of the transmission of the entirety of burst is generated for each slot and is included in the control channel.

In contrast, when the target slots are the slots after the predetermined slot in the burst (Yes at Step S102), the FB timing information designating that the feedback timing with respect to the subject slots is the same as that of the feedback with respect to the next burst is generated and a control channel that includes the subject FB timing information is generated (Step S104).

In this way, from among the plurality of slots included in a single burst, regarding the predetermined number of slots from the top, the FB timing information that specifies the common slot as the feedback timing of the ACKs or the NACKs is generated. Furthermore, regarding the rearward slots in the burst, the FB timing information that designates, as the feedback timing of the ACKs or the NACKs, to collectively feed back the rearward slots together with the next burst is generated.

The control channel generated by the control channel generating unit <NUM> and the data channel generated by the data channel generating unit <NUM> are output to the mapping unit <NUM> and are mapped onto each of the plurality of slots, and a burst is generated (Step S105). The encoding bits of the transmission data for each slot included in this burst are held by the data channel generating unit <NUM> in preparation for retransmission.

In a period of time for which the burst is generated, the LBT process is periodically performed by the LBT processing unit <NUM> and it is judged whether the U band is idle (Step S106). Specifically, it is judges whether the received power of the U band in the wireless communicating unit <NUM> is greater than or equal to the predetermined threshold, and when the received power is greater than or equal to the predetermined threshold, it is judged, by the LBT processing unit <NUM>, that the U band is busy. When the U band is busy (No at Step S106), the burst is kept on standby until the U band becomes idle, whereas, when the U band becomes idle (Yes at Step S106), the burst is output from the mapping unit <NUM> to the wireless communicating unit <NUM>. Then, the predetermined wireless transmission process is performed on the burst by the wireless communicating unit <NUM> and the slots included in the burst are sequentially transmitted from the antenna (Step S107).

In the following, an operation of the terminal device <NUM> according to an embodiment will be described with reference to the flowchart illustrated in <FIG>. In a description below, an operation performed in a case in which the terminal device <NUM> receives a burst transmitted from the base station device <NUM> will be described.

Each of the slots in the burst transmitted from the base station device <NUM> is sequentially received by the wireless communicating unit <NUM>, is subjected to the predetermined wireless reception process, and is then output to the control channel reception processing unit <NUM> and the data channel reception processing unit <NUM>. Then, demodulation and decoding of the control channel of each slot is performed by the control channel reception processing unit <NUM> (Step S201). Consequently, the allocation information and the FB timing information for each slot are obtained, and then, the allocation information is output to the data channel reception processing unit <NUM>, whereas the FB timing information is output to the code book generating unit <NUM>.

Then, demodulation and decoding of the data channel of each of the slots are performed by the data channel reception processing unit <NUM> (Step S202). Namely, by referring to the allocation information for each slot, the data channel of each of the slots is demodulated and decoded, and the, information indicating whether the data channel for each slot is correctly coded is sent to the code book generating unit <NUM> as a notification.

Incidentally, a decoding result related to the rearward slots included in the burst that has been received last time is held in the code book generating unit <NUM>. Namely, from among the slots included in the burst received last time, the ACKs or the NACKs related to the slots designated to be collectively fed back together with the next burst are held. Thus, the decoding result related to the burst received last time is referred to by the code book generating unit <NUM> (Step S203), and the held ACKs or NACKs related to the last burst are acquired.

Then, a code book that includes the acquired ACKs or NACKs and that includes the ACKs or the NACKs related to the slots specified for feedback by the FB timing information is generated (Step S204). In other words, a code book that includes the ACKs or the NACKs related to the rearward slots in the burst received last time and that includes the ACKs or the NACKs related to the predetermined number of slots located from the top of the burst received this time is generated by the code book generating unit <NUM>. At this time, the ACKs or the NACKs related to the slots that are designated to be fed back together with the next burst by the FB timing information is held by the code book generating unit <NUM>. Namely, the ACKs or the NACKs related to the rearward slots in the burst received this time are held up to the reception time of the next burst.

In this way, because a single code book is generated from the ACKs or the NACKs that are present across a plurality of bursts is generated in accordance with the FB timing information, it is possible to reduce the number of times the ACKs or the NACKs are fed back to the minimum and it is possible to decrease a frequency in which the U band is occupied by feedback of the ACKs or the NACKs. As a result, continuous transmission of the bursts in the downlink is not limited due to feedback of the ACKs or the NACKs, it is thus possible to suppress a decrease in transmission efficiency.

When transmission data to be transmitted to the base station device <NUM> is present, a data channel in an uplink is generated by the data channel generating unit <NUM> (Step S205). Both of the code book generated by the code book generating unit <NUM> and the data channel generated by the data channel generating unit <NUM> are output to the mapping unit <NUM> and are mapped onto each of the slots, and then a transmission signal in the uplink is generated (Step S206).

In a period of time for which the transmission signal in the uplink is generated, the LBT process is periodically performed by the LBT processing unit <NUM> and it is judged whether the U band is idle (Step S207). Specifically, it is judged whether the received power of the U band in the wireless communicating unit <NUM> is greater than or equal to the predetermined threshold, and, when the received power is greater than or equal to the predetermined threshold, it is judged, by the LBT processing unit <NUM>, that the U band is busy. When the U band is busy (No at Step S207), the burst is kept on standby until the U band becomes idle, whereas, when the U band becomes idle (Yes at Step S207), the transmission signal in the uplink is output from the mapping unit <NUM> to the wireless communicating unit <NUM>. Then, a predetermined wireless transmission process is subjected to the transmission signal by the wireless communicating unit <NUM> and the transmission signal in the uplink is transmitted from the antenna (Step S208).

In the following, a specific transmission status using by the U band will be described with reference to <FIG> illustrates the transmission status when bursts <NUM> and <NUM> are transmitted from the base station device <NUM> to the terminal device <NUM> in the U band.

Each of the bursts <NUM> and <NUM> includes seven slots of slots #<NUM> to #<NUM>. Regarding the slots #<NUM> to #<NUM> included in the bursts <NUM> and <NUM>, the slot immediately after the burst is specified as the feedback timing. Namely, in the control channel associated with the slots #<NUM> to #<NUM>, the FB timing information that specifies the number of slots from each of the slots to the slot immediately after the burst is included. For example, in the control channel associated with the slot #<NUM>, the FB timing information that specifies that the feedback timing is seven slots after the slot #<NUM> is included, and, in the control channel associated with the slot #<NUM>, FB timing information that specifies that the feedback timing is six slots after the slot #<NUM> is included. <FIG> illustrates slot numbers <NUM> to <NUM> specified by the FB timing information in the slots #<NUM> to #<NUM>, respectively, included in the bursts <NUM> and <NUM>.

In contrast, regarding the slots #<NUM> to #<NUM> in each of the bursts <NUM> and <NUM>, these slots are designated to be collectively fed back together with the next burst. Namely, in the control channel associated with the slots #<NUM> to #<NUM>, the FB timing information that designates to simultaneously feed back the ACKs or the NACKs together with the ACKs or the NACKs related to the next burst is included. In <FIG>, FB timing information related to the slots #<NUM> to #<NUM> in each of the bursts <NUM> and <NUM> is indicated by "Nx".

As an outcome of the LBT process, when an idle time period <NUM> of the U band reaches a predetermined length, the base station device <NUM> transmits the burst <NUM> in the downlink to the terminal device <NUM>. As described above, in the slots #<NUM> to #<NUM> in the burst <NUM>, FB timing information that specifies the slots immediately after the burst <NUM> as the feedback timing is included, and, in the slots #<NUM> to #<NUM>, the FB timing information that designates to collectively feed back the slots together with the next burst is included.

The terminal device <NUM> that receives the burst <NUM> specifies, based on the FB timing information, that the feedback timings of the slots #<NUM> to #<NUM> are the same slot. Then, the terminal device <NUM> generates a code book that includes the ACKs or the NACKs related to the slots #<NUM> to #<NUM> and, when an idle time period <NUM> after the reception of the burst <NUM> reaches a predetermined length, the terminal device <NUM> sends a code book <NUM> by using a slot in the uplink specified by the FB timing information associated with the slots #<NUM> to #<NUM>. In contrast, because the terminal device <NUM> determines, based on the FB timing information, that the feedback timing of the slots #<NUM> to #<NUM> is the reception time of the next burst, the terminal device <NUM> holds the ACKs or the NACKs related to the slots #<NUM> to #<NUM> until the reception time of the next burst.

It is possible to generate the code book including the ACKs or the NACKs related to the slots #<NUM> to #<NUM> during the reception process performed on the slots #<NUM> to #<NUM>. Accordingly, it is possible to set the feedback timing related to the slots #<NUM> to #<NUM> in the burst <NUM> to the slot immediately after the burst <NUM>. Namely, it is possible to promptly perform feedback with respect to the ACKs or the NACKs related to the predetermined number of slots from the top of the burst <NUM>. Furthermore, because the feedback timing is the slot immediately after the burst <NUM>, it is possible to reduce the possibility that feedback is suspended due to busy state in the U band.

The base station device <NUM> performs the LBT process during a period of time for which the next burst <NUM> is transmitted, and then, stands by without transmitting the burst <NUM> in a busy time period <NUM> of the U band. Then, when an idle time period <NUM> of the U band reaches the predetermined length, the base station device <NUM> transmits the burst <NUM> in the downlink to the terminal device <NUM>. As described above, in the slots #<NUM> to #<NUM> in the burst <NUM>, the FB timing information that specifies the slot immediately after the burst <NUM> as the feedback timing is included and, in the slots #<NUM> to #<NUM>, the FB timing information that designates to feed back the slots together with the next burst is included.

The terminal device <NUM> that receives the burst <NUM> specifies, based on the FB timing information, that the feedback timings of the slots #<NUM> to #<NUM> are the same slot. Then, the terminal device <NUM> obtains the ACKs or the NACKs held at the time of reception of the burst <NUM> last time and generates a code book that includes these ACKs or NACKs and that includes the ACKs or the NACKs related to the slots #<NUM> to #<NUM> in the burst <NUM>. Namely, the terminal device <NUM> generates a single code book that includes the ACKs or the NACKs related to the slots #<NUM> to #<NUM> in the burst <NUM> and that includes the ACKs or the NACKs related to the slots #<NUM> to #<NUM> in the burst <NUM>.

When an idle time period <NUM> after the reception of the burst <NUM> reaches the predetermined length, the terminal device <NUM> transmits a code book <NUM> by using the slot in the uplink specified by the FB timing information associated with the slots #<NUM> to #<NUM>. In the code book <NUM>, not only the ACKs or the NACKs related to the slots #<NUM> to #<NUM> in the burst <NUM>, but also the ACKs or the NACKs related to the slots #<NUM> to #<NUM> in the burst <NUM> received last time are included. Namely, the ACKs or the NACKs that are present across the two bursts <NUM> and <NUM> are fed back by the code book <NUM> and it is thus possible to reduce the number of times of feedback. As a result, continuous transmission of the bursts in the downlink is not limited due to feedback of the ACKs or the NACKs, it is thus possible to suppress a decrease in transmission efficiency.

<FIG> is a diagram illustrating a specific example of the control information for each slot. <FIG> illustrates an example of the control information included in the control channel associated with the slots #<NUM> to #<NUM> included in the burst <NUM> illustrated in <FIG>.

As illustrated in <FIG>, in the control channel of each of the slots, the FB timing information and a counter downlink assignment index (DAI) are included. The FB timing information is control information composed of, for example, four bits, and these four bits are associated with, for example, each of the feedback timings illustrated in <FIG>. Namely, for example, the FB timing information on the slot #<NUM> is "<NUM>" and this indicates that seven slots after the slot #<NUM> is the feedback timing. Similarly, for example, the FB timing information on the slot #<NUM> is "<NUM>" and this indicates that three slots after the slot #<NUM> is the feedback timing.

It is found that, based on these pieces of FB timing information, in an example illustrated in <FIG>, the feedback timings of the slots #<NUM> to #<NUM> are the same slot; therefore, the terminal device <NUM> may simply generate a code book including the ACKs or the NACKs related to the slots #<NUM> to #<NUM>.

In contrast, the FB timing information on the slots #<NUM> to #<NUM> is "<NUM>" and this indicates that the feedback timing is at the reception time of the next burst. Consequently, regarding the slots #<NUM> to #<NUM> having the FB timing information or "<NUM>", the terminal device <NUM> may simply generate a code book together with the ACKs or the NACKs related to the next burst at the reception time of the next burst.

When the code book is generated, the ACK or the NACK related to each of the slots is aligned in the order in accordance with the counter DAI. Namely, for example, the ACK or the NACK of the slot #<NUM> having the counter DAI of "<NUM>" is arranged at the top of the code book and, after that, the ACK or the NACK of each of the slots is aligned in an ascending order of the counter DAIs. At this time, because the counter DAI is, for example, two bits, the ACK or the NACK of the slot #<NUM> having the counter DAI of "<NUM>" is cyclically arranged next to the ACK or the NACK of the slot #<NUM> having the counter DAI of "<NUM>".

<FIG> is a diagram illustrating another specific example of the control information for each slot. <FIG> illustrates an example of control information included in the control channel of the slots #<NUM> to #<NUM> in the burst <NUM> illustrated in <FIG>.

As illustrated in <FIG>, in the control channel of each of the slot, a window ID, FB timing information, and a counter downlink assignment index (DAI) are included. The window ID is identification information for identifying the slots for which the feedback timings of ACKs or NACKs can be the same slot. Namely, it is possible to collectively feed back the ACKs or the NACKs related to the slots having the same window ID by using a single code book. Furthermore, the window ID indicates whether the ACKs or the NACKs are to collectively be fed back together with the next burst. Namely, in the example illustrated in <FIG>, regarding the slot having the window ID of "<NUM>", ACKs or NACKs are fed back in accordance with the FB timing information, whereas, regarding the slot having the window ID of "<NUM>", ACKs or NACKs are fed back together with the next burst regardless of the FB timing information. Accordingly, in the example illustrated in <FIG>, it is found that the ACKs or the NACKs related to the slots #<NUM> to #<NUM> are collectively fed back to a single code book immediately after the burst <NUM> and the ACKs or the NACKs related to the slots #<NUM> to #<NUM> are collectively fed back by a single code book together with the ACKs or the NACKs related to the next burst <NUM>.

Furthermore, the FB timing information illustrated in <FIG> is control information composed of, for example, four bits and these four bits are associated with the feedback timing illustrated in, for example, <FIG>. Namely, for example, the FB timing information in the slot #<NUM> is "<NUM>" and this indicates that "seven slots after" the slot #<NUM> is the feedback timing. Similarly, for example, the FB timing information in the slot #<NUM> is "<NUM>" and this indicates that "three slots after" the slot #<NUM> is the feedback timing.

In contrast, the FB timing information in the slots #<NUM> to #<NUM> is "<NUM>" and this indicates that FB timing information is not applied to the slots #<NUM> to #<NUM>. Namely, it is indicated that, because the feedback timing of the slots #<NUM> to #<NUM> having the window ID of "<NUM>" conforms to the FB timing information on the next burst <NUM>, the FB timing information in the slots #<NUM> to #<NUM> can be ignored.

Furthermore, in <FIG> and <FIG>, each of the pieces of FB timing information, the counter DAI, and the window ID are illustrated as independent control information; however, a part or all of the information may also be integrated. Namely, for example, four bits of the FB timing information and two bits of the counter DAI may also be integrated into six bits of control information. Furthermore, the number of bits of these pieces of control information can be arbitrarily changed.

Furthermore, instead of defining the window by the window ID, a <NUM>-bit window ID may also be used as the control information that indicates whether the FB timing information is valid. For example, it may also be possible to set the FB timing information in the slot having the window ID of "<NUM>" to be valid and the FB timing information in the slot having the window ID of "<NUM>" to be invalid. The data channel associated with the control channel including a certain burst of "<NUM>:invalid" may also be defined to belong to the same window as that of the data channel associated with the control channel including "<NUM>:valid" in the next burst. In this case, "<NUM>" described above can also be used to indicate the feedback timing.

As described above, according to the embodiment, the base station device performs transmission by including the control information that specifies the number of slots up to the feedback timing into the predetermined number of slots that are present from the top from among the plurality of slots constituting the burst and by including, in the rearward slots in the burst, the control information that designates to collectively performs feedback at the reception time of the next burst. Then, the terminal device generates a code book including the ACKs or the NACKs related to the predetermined number of slots from the top of the received burst and performs feedback at the feedback timing specified by the control information. Furthermore, the terminal device holds the ACKs or the NACKs related to the rearward slots in the burst until the reception time of the next burst, generates a code book by collecting the ACKs or the NACKs related to the next burst, and performs feedback at the feedback timing specified by the control information on the next burst. Consequently, it is possible to reduce the number of times of feedback of the ACKs or the NACKs to the minimum and it is thus possible to decrease a frequency in which the U band is occupied by feedback of the ACKs or the NACKs. As a result, continuous transmission of the bursts in the downlink is not limited due to feedback of the ACKs or the NACKs, it is thus possible to suppress a decrease in transmission efficiency.

Furthermore, in the embodiment described above, it is assumed that the code book including the ACKs or the NACKs is transmitted by using the slot immediately after the burst; however, when the U band is busy at the timing immediately after the burst, the code book is not transmitted. In such a case, the base station device <NUM> that detects that the code book is not received may also request to transmit the code book at the time of next burst and, immediately after this burst, an un-transmitted code book may also be transmitted.

Specifically, for example, as illustrated in <FIG>, a description will be given of a case in which, as an example, bursts <NUM>, <NUM>, and <NUM> are transmitted from the base station device <NUM> to the terminal device <NUM>. In <FIG>, each of the bursts <NUM>, <NUM>, and <NUM> has seven slots and the FB timing information is included in each of the slots. The FB timing information in each of the slots indicates "<NUM>" to "<NUM>" that specifies the number of slots up to the feedback timing or indicates "N" that designates to collectively perform feedback together with the next burst.

Based on these pieces of the FB timing information, the five slots from the top of the burst <NUM> constitute a window #<NUM> that is capable of simultaneously performing feedback of the ACKs or the NACKs, whereas the rearward two slots in the burst <NUM> and the five slots from the top in the burst <NUM> constitute a window #<NUM> that is capable of simultaneously performing feedback of the ACKs or the NACKs. Similarly, the rearward two slots in the burst <NUM> and the five slots from the top in the burst <NUM> constitute a window #<NUM> that is capable of simultaneously performing feedback of the ACKs or the NACKs.

When an idle time period of the U band is a predetermined length as the result of the LBT process, the base station device <NUM> transmits the burst <NUM>. The terminal device <NUM> that receives the burst <NUM> generates a code book related to the slots included in the window #<NUM> and transmits the code book associated with the window #<NUM> by using the slot <NUM> in accordance with the FB timing information in the slots included in the window #<NUM>.

Then, when the idle time period of the U band is again the predetermined length as the result of the LBT process, the base station device <NUM> transmits the burst <NUM>. The terminal device <NUM> that receives the burst <NUM> generates a code book related to the slots included in the window #<NUM> and attempts to transmit the code book associated with the window #<NUM> in accordance with the FB timing information in the slots in the burst <NUM> included in the window #<NUM>. However, in a case in which the U band is busy immediately after the burst <NUM>, the terminal device <NUM> holds the code book associated with the window #<NUM> instead of transmitting the code book.

Then, when the idle time period of the U band is the predetermined length as the result of a regular LBT process, the base station device <NUM> transmits the burst <NUM>. At this time, the base station device <NUM> detects that the code book associated with the window #<NUM> is not received, and then, includes the control information that instructs to transmit the code book associated with the window #<NUM> into the slots included in the burst <NUM>. The terminal device <NUM> that receives the burst <NUM> generates a code book related to the slots included in the window #<NUM> and transmits the code book associated with the window #<NUM> by using a slot <NUM> in accordance with the FB timing information in the slots in the burst <NUM> included in the window #<NUM>.

Furthermore, because the control information that designates to transmit the code book associated with the window #<NUM> is included in the burst <NUM>, the terminal device <NUM> transmits the code book associated with the window #<NUM> by using a slot <NUM> located immediately after the slot <NUM>. Consequently, the code book that is associated with the window #<NUM> and that is not transmitted due to busy in the U band is fed back to the base station device <NUM>.

In <FIG>, the code book associated with the window #<NUM> is fed back in a separated manner from the code book associated with the window #<NUM>; however, un-transmitted code books may also be integrated and fed back. Namely, for example, as illustrated in <FIG>, when the code book associated with the window #<NUM> is not transmitted immediately after the burst <NUM>, a single code book associated with the window #<NUM> and the window #<NUM> may also be generated and fed back by using a slot <NUM> located immediately after the burst <NUM>. In this case, it may also be possible to use both cases, i.e., a case in which the control information that designates to transmit the associated code book by including the window #<NUM> is included in a slot in the burst <NUM> and a case in which the control information is not included in a slot in the burst <NUM>. In a case in which the control information is included, the control information may also be included in the control channel that includes allocation information related to the data channel or the control information may also be included in the control channel that does not include the allocation information related to the data channel.

In a case in which the control information is included in the control channel that includes the allocation information related to the data channels, for example, in addition to the ACKs or the NACKs associated with the window #<NUM> to which the data channels of the current slots belong, the control information that designates, by one bit, whether feedback is performed by integrating the ACKs or the NACKs associated with immediately before the window #<NUM> into a single code book may also be included. By doing so, there is no need to arrange a new control channel.

In contrast, in a case in which the control information is included in the control channel that does not include the allocation information related to the data channels, because an independent control channel is used, an amount of resources used for transmission is increased; however, because it is also possible to perform transmission by using the slot in which the data channel addressed to the terminal device <NUM> is not present, it is possible to enhance flexibility of channel arrangements.

Furthermore, in a case in which the control information that designates to transmit the associated code book including the window #<NUM> is not included in the slot in the burst <NUM>, it may also be possible to previously indicate, by using a higher layer signal, such as radio resource control (RRC), to generate and feed back a single code book associated with a plurality of un-transmitted windows when the immediately before code book associated with the window #<NUM> is not yet transmitted.

Furthermore, in the embodiment described above, a description has been given of a case in which the base station device <NUM> and the single piece of the terminal device <NUM> performs communication by using the U band; however, the base station device <NUM> may also communicate with a plurality of terminal devices by using the U band. Namely, the data channels addressed to a terminal device other than the terminal device <NUM> may also be multiplexed in the time direction or the frequency direction. Furthermore, the transmission timing of the code book including the ACKs or the NACKs may also be slots other than the slot immediately after the burst, or slots that are different for each terminal device may also be designated. Furthermore, carrier aggregation in the U band may also be used between the base station device <NUM> and the terminal device <NUM>. When the carrier aggregation is used, the ACKs or the NACKs related to all of the bursts that are transmitted and received in a plurality of carriers may also be collectively fed back in one of the carriers.

Claim 1:
A base station device (<NUM>) comprising:
a first generating unit (<NUM>) configured to generate a data channel transmitted in each of a plurality of time units;
a second generating unit (<NUM>) configured to generate a control channel including allocation information on the data channel and group identifying information for identifying a group to which each time unit belongs, wherein acknowledgements related to the data channel in time units belonging to a same group are collectively fed back;
a judging unit (<NUM>) configured to judge whether a frequency band for which a license is not needed to use in wireless communication is being used by another device; and
a transmitting unit (<NUM>) configured to transmit, when it is judged, by the judging unit (<NUM>), that the frequency band is not being used, the data channel and the control channel by using the frequency band, wherein
the control channel includes a feedback timing information which is not applied for the data channel when an acknowledgement for the data channel is collectively fed back with an acknowledgement for an other data channel that belongs to a same group as the data channel, the other data channel being transmitted after transmitting the data channel.