WO2018173225A1

WO2018173225A1 - Terminal device, base station device, wireless communication system and wireless communication method

Info

Publication number: WO2018173225A1
Application number: PCT/JP2017/011869
Authority: WO
Inventors: 田中　良紀
Original assignee: 富士通株式会社
Priority date: 2017-03-23
Filing date: 2017-03-23
Publication date: 2018-09-27

Abstract

A terminal device comprises: a reception unit that receives repeatedly transmitted data and control information indicating the modulation scheme and coding rate of the data; a first decoding unit that decodes the control information received by the reception unit; an acquisition unit that acquires the number of repetitions in which the data is repeatedly transmitted, on the basis of a resource size assigned to the control information decoded by the first decoding unit, and the modulation scheme and coding rate of the data indicated by the control information; and a second decoding unit that decodes the data received by the reception unit on the basis of the number of repetitions acquired by the acquisition unit.

Description

Terminal apparatus, base station apparatus, radio communication system, and radio communication method

The present invention relates to a terminal device, a base station device, a wireless communication system, and a wireless communication method.

In the current network, traffic from mobile terminals (smartphones and feature phones) occupies most of the network resources. In addition, the traffic used by mobile terminals tends to continue to expand.

On the other hand, in response to the development of IoT (Internet of things) services (for example, monitoring systems for traffic systems, smart meters, devices, etc.), it is required to support services with various requirements. Therefore, in the next generation (for example, 5G (5th generation mobile communication)) communication standard, in addition to the 4G (4th generation mobile communication) standard technology (for example, Non-Patent Documents 1 to 11), an even higher There is a demand for a technology that realizes a data rate, a large capacity, and a low delay. Regarding next-generation communication standards, technical studies in Non-Patent Documents 12 to 18 are in progress.

As described above, in order to support a wide variety of services, eMBB (Enhanced Mobile BroadBand), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable) in the next generation communication standards (for example, 5G) and support for many use cases classified as “Low Latency Communication”.

Among them, URLLC is the most difficult use case to be realized. First, there is a requirement for ultra-high reliability that the error rate in the wireless section is on the order of 10 ⁻⁵ . As one method for realizing ultra-high reliability, there is a method of increasing the amount of resources used and making data redundant. However, since the radio resources are limited, the use resources cannot be increased without limit.

Regarding low delay as well, URLLC aims to set the delay in the radio section of the user plane in the uplink and downlink to 0.5 milliseconds. This is a high requirement of less than 1/10 of LTE (Long Term Evolution) 4G wireless system. In URLLC, it is desired to satisfy the two requirements of ultra-high reliability and low delay as described above.

Moreover, in LTE (4th generation communication system) and the like, a hybrid automatic repeat request (HARQ) technology is adopted to realize efficient data transmission. In HARQ, the receiving apparatus requests the transmitting apparatus side to retransmit the data that could not be correctly decoded in the processing of the layer 1 protocol layer such as LTE. When retransmission of data is requested, the transmission device transmits retransmission data corresponding to the original data retransmission request that could not be correctly decoded on the reception device side. On the receiving device side, data decoding is performed by combining data that could not be correctly decoded and retransmission data.

HARQ can increase the reliability by setting a large number of retransmissions, but the delay increases as the number of retransmissions increases. For this reason, it is difficult to apply to data such as URLLC that requires low delay.

As a method for ensuring the reliability required for the next-generation communication standard, a repetition or open loop HARQ method in which the number of times data is repeatedly transmitted is determined in advance and the determined number of times of repeated transmission is executed is effective. (Non-patent document 20).

International Publication No. 2016/163502 International Publication No. 2015/198490 Japanese Unexamined Patent Publication No. 2016-197876

By the way, in these repetition and open loop HARQ, the number of repeated transmissions appropriate for data transmission is notified from the transmission side to the reception side. Therefore, there is a problem that the overhead of the control signal accompanying the data increases.

The disclosed technology has been made in view of the above points, and an object thereof is to provide a terminal device, a base station device, a wireless communication system, and a wireless communication method capable of reducing an increase in overhead.

In one aspect, a terminal device disclosed in the present application is a receiving unit that receives repeatedly transmitted data and control information indicating a modulation scheme and a coding rate of the data, and the control information received by the receiving unit. Based on the first decoding unit that decodes the resource, the resource size assigned to the control information decoded by the first decoding unit, and the modulation scheme and coding rate of the data indicated by the control information. An acquisition unit that acquires the number of repetitions transmitted repeatedly, and a second decoding unit that decodes data received by the reception unit based on the number of repetitions acquired by the acquisition unit.

According to one aspect of the terminal device, the base station device, the wireless communication system, and the wireless communication method disclosed in the present application, there is an effect that an increase in overhead can be reduced.

FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to an embodiment. FIG. 2 is a block diagram showing a configuration of the base station apparatus according to one embodiment. FIG. 3 is a diagram for explaining determination of the aggregation level. FIG. 4 is a diagram illustrating a specific example of repeated transmission. FIG. 5 is a flowchart showing a transmission method according to an embodiment. FIG. 6 is a block diagram illustrating a configuration of a user terminal device according to an embodiment. FIG. 7 is a flowchart showing a reception method according to an embodiment. FIG. 8 is a diagram illustrating a specific example of the repetition count table.

Hereinafter, embodiments of a terminal device, a base station device, a wireless communication system, and a wireless communication method disclosed in the present application will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Moreover, since the following embodiment is applicable to the system described in the said nonpatent literature, the content of the said nonpatent literature is included here by reference.

FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to an embodiment. The radio communication system illustrated in FIG. 1 includes a base station device 100 and a plurality of user terminal devices 200.

The base station apparatus 100 transmits, for example, transmission data such as eMBB data and URLLC data and control channel information including downlink control information (DCI: Downlink Control Information) to the user terminal apparatus 200. At this time, base station apparatus 100 repeatedly transmits transmission data. Base station apparatus 100 determines the number of times data is repeatedly transmitted based on the size of resources allocated to DCI, the modulation scheme and coding rate of transmission data. The repeated transmission of transmission data by the base station apparatus 100 will be described in detail later.

User terminal apparatus 200 receives data such as eMBB data and URLLC data transmitted from base station apparatus 100, and information on the control channel including DCI. Then, the user terminal device 200 calculates the number of times data is repeatedly transmitted based on the size of the resource allocated to DCI, the modulation method and the coding rate of the received data. The user terminal device 200 decodes the repeatedly transmitted data according to the calculated repetition count. Decoding of received data by the user terminal device 200 will be described in detail later.

FIG. 2 is a block diagram showing a configuration of base station apparatus 100 according to one embodiment. A base station apparatus 100 illustrated in FIG. 2 includes a processor 100a, a memory 100b, and a wireless transmission / reception unit 100c.

The processor 100a includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and performs overall control of the base station apparatus 100 as a whole. Specifically, the processor 100a includes an FFT (Fast Fourier Transform) unit 110, a CQI (Channel Quality Indicator) acquisition unit 120, an aggregation level (hereinafter abbreviated as “AGGR level”) determination unit 130, and transmission control. Unit 140, transmission data generation unit 150, control channel generation unit 160, multiplexing unit 170, and IFFT (Inverse Fast Fourier Transform) unit 180.

The FFT unit 110 performs fast Fourier transform on the uplink signal received by the wireless transmission / reception unit 100c, and generates a frequency-domain signal that can acquire data for each of a plurality of subcarriers having different frequencies.

The CQI acquisition unit 120 acquires CQI indicating the downlink channel quality from the frequency domain signal generated by the FFT unit 110. That is, the user terminal apparatus 200 measures, for example, SINR (Signal to Interference and Noise Ratio) of the downlink, and feeds back the CQI corresponding to the measurement result to the base station apparatus 100. Therefore, the CQI acquisition unit 120 acquires the CQI fed back from each user terminal device 200.

The AGGR level determination unit 130 determines an aggregation level (AGGR level) indicating the size of a resource to be allocated to DCI based on the CQI. Specifically, the AGGR level determination unit 130 assigns a smaller size resource to the DCI as the downlink channel quality is better, and assigns a larger size resource to the DCI as the downlink channel quality is lower. That is, for example, when the AGGR level is represented by the number of CCEs (Control Channel Elements) assigned to the control channels, the AGGR level determination unit 130 assigns fewer CCEs to the DCI as the downlink channel quality is better. More CCEs are assigned to DCI as the downlink channel quality is poorer.

The AGGR level determination unit 130 determines the AGGR level so that the DCI received in the user terminal device 200 satisfies a predetermined error rate when determining the DCGR AGGR level. That is, for example, as shown in FIG. 3, the AGGR level for each user terminal apparatus 200 is determined according to the downlink SINR indicated by the CQI and the target error rate Er to be satisfied.

In the example shown in FIG. 3, for example, in the range of SINR from S1 to S2, the AGGR level 301 is selected in order to make the error rate less than the target error rate Er. For example, when the SINR is in the range of S2 to S3, the AGGR level 302 is selected. For example, when the SINR is in the range of S3 to S4, the AGGR level 303 is selected. Is done. In other words, FIG. 3 shows that the required SINR, which is the minimum SINR required when adopting the AGGR level 301, is S1. Similarly, the required SINR when employing the AGGR level 302 is S2, the required SINR when employing the AGGR level 303 is S3, and the required SINR when employing the AGGR level 304 is S4.

The transmission control unit 140 selects MCS (Modulation Coding Scheme) of transmission data to be transmitted to the user terminal device 200 based on the CQI. That is, the transmission control unit 140 determines the transmission data modulation scheme and coding rate for each user terminal device 200 based on the CQI. Specifically, the transmission control unit 140 increases the modulation multi-value number and the coding rate as the downlink channel quality is better, and increases the coding rate as the downlink channel quality is worse. The modulation multi-level number is reduced and the coding rate is reduced. Therefore, if the channel quality of the downlink is good, the transmission control unit 140 uses a modulation scheme having a large modulation multi-level number such as 256QAM (Quadrature Amplitude Modulation) or 64QAM, and reduces redundant bits for error correction. Then decide. Further, if the downlink channel quality is poor, the transmission control unit 140 uses a modulation scheme with a small modulation multi-level number such as BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying), and redundant bits. Decide to increase.

However, the transmission control unit 140 selects an MCS corresponding to channel quality better than the channel quality indicated by the CQI. That is, the transmission control unit 140 selects a modulation scheme and coding rate corresponding to SINR better than the actual SINR. In other words, the transmission control unit 140 selects a modulation scheme having a larger modulation multi-value number than the modulation scheme corresponding to CQI, and selects a coding rate larger than the coding rate corresponding to CQI.

Then, transmission control section 140 determines the number of repeated data transmissions based on the difference between the required SINR of the data required by the selected MCS and the required SINR of the DCI required by the DCI AGGR level. Specifically, the transmission control unit 140 repeats the number of repetitions when the required SINR of the data required by the selected MCS is γ _d dB and the required SINR of the DCI required by the DCI AGGR level is γ _c dB. n is calculated by the following formula (1).

In Equation (1), ceil (x) is the smallest integer greater than x, and a is a predetermined coefficient (for example, 3 or 6). The required SINR (γ _d ) of data required by the selected MCS is the minimum SINR that can satisfy a predetermined error rate when the transmission data modulation scheme and coding rate are used. . As described above, since the transmission control unit 140 selects an MCS corresponding to channel quality better than the channel quality indicated by the CQI, the required SINR (γ _d ) of the data is better than the actual SINR. It is. On the other hand, the DCI required SINR (γ _c ) required by the DCI AGGR level is the minimum SINR that can satisfy a predetermined error rate when the DCI AGGR level is adopted. As described above, since the AGGR level determination unit 130 selects the AGGR level corresponding to the channel quality indicated by the CQI, the required SINR (γ _c ) of DCI is an SINR that reflects the actual SINR.

Therefore, as shown in the above equation (1), the larger the difference between the required SINR (γ _d ) of the data MCS and the actual SINR (γ _c ), the larger the number of repetitions n. By repeatedly transmitting data, a predetermined error rate is satisfied even when data is transmitted using MCS corresponding to better line quality than actual.

The transmission data generation unit 150 generates transmission data using the MCS determined by the transmission control unit 140. That is, transmission data generating section 150 encodes transmission information at the coding rate selected by transmission control section 140 and modulates it with the modulation scheme selected by transmission control section 140.

The control channel generation unit 160 generates control channel information including DCI for notifying the user terminal apparatus 200 of the MCS determined by the transmission control unit 140. At this time, the control channel generation unit 160 generates DCI of the resource size of the AGGR level determined by the AGGR level determination unit 130. Therefore, the control channel generator 160 generates a DCI having a smaller resource size as the downlink channel quality is better, and generates a DCI having a larger resource size as the downlink channel quality is lower. In addition to the DCI, the control channel generation unit 160 may generate, for example, a reference signal used by the user terminal device 200 for measurement of downlink channel quality. However, the control channel generation unit 160 does not generate control information indicating the number of times transmission data is repeatedly transmitted. This is because the number of repeated transmissions of transmission data can be calculated from the MCS of transmission data and the AGGR level of DCI, and it is not necessary to explicitly notify the user terminal device 200 as control information. Since control information indicating the number of times transmission data is repeatedly transmitted is not generated, an increase in overhead can be reduced.

The multiplexing unit 170 multiplexes the transmission data generated by the transmission data generation unit 150 and the control information generated by the control channel generation unit 160. Specifically, for example, multiplexing section 170 arranges control information including DCI in the control channel area for each subframe, and arranges transmission data in the data channel area. At this time, the multiplexing unit 170 repeatedly arranges transmission data for the number of repetitions determined by the transmission control unit 140. That is, for example, when the number of repetitions is 2, multiplexing section 170 arranges the same transmission data in the data channel region of two consecutive subframes.

There are the following two methods for the multiplexing unit 170 to repeatedly arrange transmission data. That is, for example, as illustrated in the upper diagram of FIG. 4, the multiplexing unit 170 may arrange DCI 411 in one control channel region 410 and arrange the

same transmission data

421 and 422 in two data channel regions 420. . In this case, the DCI 411 indicates the MCS of the

data

421 and 422 that are repeatedly arranged. For this reason, the modulation method and coding rate of the

data

421 and 422 repeatedly arranged are not changed.

On the other hand, for example, as shown in the lower diagram of FIG. 4, the multiplexing unit 170 arranges

DCIs

431 and 441 in the two control channel regions 410 and arranges the

same transmission data

441 and 442 in the two data channel regions 420, respectively. Also good. In this case, DCI 431 indicates the MCS of data 441, and DCI 432 indicates the MCS of data 442. For this reason, the modulation method and coding rate of the

data

441 and 442 that are repeatedly arranged may be changed. In any of the transmission data arrangements shown in FIG. 4, it is desirable that the DCI and the transmission data corresponding to each other are arranged in the same or close frequency bands.

The IFFT unit 180 performs inverse fast Fourier transform on the transmission data and control information multiplexed by the multiplexing unit 170 to generate a time-domain transmission signal.

The memory 100b includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores various types of information when processing is executed by the processor 100a.

The wireless transmission / reception unit 100c performs wireless transmission processing such as D / A (Digital / Analog) conversion and up-conversion on the transmission signal generated by the IFFT unit 180. And the radio | wireless transmission / reception part 100c transmits a transmission signal via an antenna. Also, the radio transmission / reception unit 100c performs radio reception processing such as down-conversion and A / D (Analog / Digital) conversion on the uplink signal received via the antenna.

Next, a transmission method by the base station apparatus 100 configured as described above will be described with reference to the flowchart shown in FIG.

The user terminal device 200 that wirelessly communicates with the base station device 100 measures the SINR of the downlink, and feeds back the CQI corresponding to the measurement result to the base station device 100. The uplink signal including the CQI is received by the antenna of the base station apparatus 100 and is input to the processor 100a via the radio transmission / reception unit 100c. Then, the FFT unit 110 performs fast Fourier transform on the received signal, and the CQI acquisition unit 120 acquires the CQI included in the received signal (step S101).

The CQI is notified to the AGGR level determining unit 130, and the AGGR level indicating the resource size assigned to the DCI is determined (step S102). Specifically, it is determined that the AGGR level of DCI is set to an AGGR level having a smaller resource size as the downlink channel quality is better, and the DCI AGGR level is set to the resource size as the downlink channel quality is lower. Is determined to be a large AGGR level. The AGGR level determined here reflects the actual channel quality of the downlink reported from the user terminal device 200.

The CQI is also notified to the transmission control unit 140, and the MCS of the transmission data to be transmitted to the user terminal device 200 is determined (step S103). Specifically, it is determined that the better the downlink channel quality is, the larger the modulation level of the modulation scheme and the higher the coding rate. The worse the downlink channel quality, It is determined to reduce the modulation multi-level number and the coding rate.

However, when determining the MCS, an MCS corresponding to a better channel quality than the actual downlink channel quality reported from the user terminal device 200 is selected. That is, a modulation scheme having a larger modulation multi-value number than the modulation scheme corresponding to CQI is selected, and a coding rate larger than the coding rate corresponding to CQI is selected. Therefore, the required SINR for using the selected MCS is higher than the required SINR for using the AGGR level described above. Note that either the determination of the AGGR level in step S102 or the determination of MCS in step S103 may be performed first or may be performed simultaneously.

When the AGGR level and MCS are determined, the transmission control unit 140 determines the number of repetitions for repeatedly transmitting the transmission data (step S104). Specifically, the number of repetitions is determined by the above equation (1) from the required SINR of the data for using the MCS and the required SINR of the DCI for using the AGGR level. The determined number of repetitions is notified to transmission data generation section 150 together with the determined MCS. Further, the determined AGGR level and MCS are also notified to the control channel generation unit 160.

Then, the control channel generation unit 160 generates DCI for notifying the transmission data MCS (step S105). The DCI is generated by assigning an AGGR level resource determined by the AGGR level determination unit 130 to the MCS information of the transmission data. Therefore, if the channel quality of the downlink is good, DCI having a small resource size is generated, and if the channel quality of the downlink is poor, DCI having a large resource size is generated.

Note that control information other than DCI may be generated by the control channel generation unit 160. However, control information indicating the number of repetitions of transmission data is not generated, and the number of repetitions is not notified to the user terminal device 200 with explicit control information. Thereby, even when transmission data is repeatedly transmitted, an increase in overhead due to control information indicating the number of repetitions is reduced.

In addition, the transmission data generation unit 150 generates transmission data using the determined MCS (step S106). That is, transmission information is encoded with the determined coding rate, and the transmission information is modulated with the determined modulation scheme. When the MCS of transmission data that is repeatedly transmitted is changed for each repetition, transmission data using each MCS is generated from the same transmission information. Further, either the determination of the number of repetitions in step S104 or the DCI generation in step S105 may be executed first or may be executed simultaneously. Furthermore, the determination of the number of repetitions in step S104 and the transmission data generation in step S106 may be executed first, and then the DCI generation in step S105 may be executed.

The control information including DCI and transmission data are multiplexed by the multiplexing unit 170 (step S107). Specifically, for example, control information including DCI is arranged in the control channel area of the subframe, and transmission data is arranged in the data channel area. At this time, the transmission data is repeatedly arranged by the number of repetitions. That is, the same transmission data is arranged in the data channel region of the same number of subframes as the number of repetitions. The MCS of these transmission data may be the same or different. When the MCS of the transmission data in each subframe is different, DCI is arranged in the control channel region in each subframe.

The transmission signal generated by multiplexing the control information and the transmission data is subjected to inverse fast Fourier transform by the IFFT unit 180 (step S108), and a time domain transmission signal is generated. This transmission signal is subjected to wireless transmission processing by the wireless transmission / reception unit 100c (step S109), and is transmitted to the user terminal device 200 via the antenna (step S110).

In this way, base station apparatus 100 determines the number of repeated transmissions of transmission data from the required SINR of data corresponding to the MCS of the transmission data and the required SINR of DCI corresponding to the AGGR level of DCI, and repeatedly transmits the transmission data. To do. Moreover, the base station apparatus 100 does not generate control information indicating the number of repeated transmissions, and does not notify the number of repeated transmissions based on the control information. For this reason, an increase in overhead due to control information can be reduced.

Next, the user terminal device 200 according to an embodiment will be described. FIG. 6 is a block diagram illustrating a configuration of the user terminal device 200. The user terminal device 200 illustrated in FIG. 6 includes a wireless transmission / reception unit 200a, a processor 200b, and a memory 200c.

The wireless transmission / reception unit 200a receives a signal via an antenna and performs wireless reception processing such as down-conversion and A / D conversion on the received signal. Then, the radio transmission / reception unit 200a outputs the received signal to the processor 200b. The radio transmission / reception unit 200a performs radio transmission processing such as D / A conversion and up-conversion on an uplink signal including CQI and transmits the signal via an antenna.

The processor 200b includes, for example, a CPU, FPGA, DSP, or the like, and performs overall control of the entire user terminal device 200. Specifically, the processor 200b includes an FFT unit 210, a control channel decoding unit 220, an iterative number calculation unit 230, a reception data decoding unit 240, a CQI generation unit 250, and an IFFT unit 260.

The FFT unit 210 performs a fast Fourier transform on the reception signal received by the wireless transmission / reception unit 200a to generate a frequency domain reception signal. The received signal includes transmission data addressed to the user terminal device 200 and control information including DCI.

The control channel decoding unit 220 demodulates and decodes the DCI arranged in the control channel region of the received signal. At this time, the control channel decoding unit 220 blindly detects the DCGR AGGR level, and demodulates and decodes the DCI. That is, control channel decoding section 220 attempts to decode DCI for all resource sizes that may be assigned to DCI, and detects the DCI AGGR level of user terminal apparatus 200. Then, the control channel decoding unit 220 acquires MCS information of transmission data addressed to the user terminal apparatus 200 by decoding the detected AGGR level DCI.

The repetition count calculation unit 230 calculates the number of repetitions of transmission data based on the MCS notified by DCI and the DCGR AGGR level. Specifically, the repetition count calculation unit 230 calculates the above formula (1) based on the difference between the required SINR of data required by the MCS notified by DCI and the required SINR of DCI required by the AGGR level of DCI. ) To calculate the number of repeated data transmissions. As described above, since the number of repetitions is calculated based on the MCS information notified by the DCI and the AGGR level of the DCI, the user terminal device 200 can be used without the control information that explicitly notifies the number of repetitions. The number of repetitions of transmission data can be grasped.

The reception data decoding unit 240 demodulates and decodes the reception data arranged in the data channel region of the reception signal. At this time, the reception data decoding unit 240 uses the MCS information notified by the DCI and decodes the reception data repeated for the number of repetitions calculated by the repetition number calculation unit 230. That is, the reception data decoding unit 240 improves the decoding accuracy of the reception data by using the same data repeatedly transmitted.

The CQI generating unit 250 measures the downlink SINR using a known reference signal included in the control channel region. Then, CQI generating section 250 generates a CQI for reporting the measured SINR to base station apparatus 100.

The IFFT unit 260 performs inverse fast Fourier transform on the uplink signal including the CQI generated by the CQI generation unit 250 to generate a time domain signal.

Next, a reception method by the user terminal device 200 configured as described above will be described with reference to the flowchart shown in FIG.

The signal including the control information and the transmission data transmitted from the base station apparatus 100 is received by the radio transmission / reception unit 200a via the antenna (step S201). The received signal is subjected to wireless reception processing by the wireless transmission / reception unit 200a (step S202) and input to the processor 200b.

The received signal is fast Fourier transformed by the FFT unit 210 (step S203), and the DCI arranged in the control channel region of the received signal is demodulated and decoded by the control channel decoding unit 220 (step S204). The demodulation and decoding of DCI is performed by blind detection that attempts decoding for all resource sizes that may be assigned to DCI. That is, when the AGGR level of DCI is selected from 4 types of 2 CCEs, 4 CCEs, 8 CCEs, and 16 CCEs, for example, demodulation is performed for each of these 4 types of CCEs. And decryption is attempted. As a result, when DCI including MCS information of transmission data is obtained from the decoding results of any number of CCEs, the AGGR level of DCI is detected.

The MCS information indicated by the DCI and the AGGR level of the DCI are notified to the repetition number calculation unit 230, and the number of repetitions in which data is repeatedly transmitted is calculated based on the MCS notified by the DCI and the AGGR level of the DCI. (Step S205). That is, based on the difference between the required SINR of the data required by the MCS notified by the DCI and the required SINR of the DCI required by the DCI AGGR level, the number of repeated data transmissions is calculated by the above equation (1). Is done. Since the number of repetitions is calculated in this way, control information that explicitly notifies the number of repetitions is unnecessary, and an increase in overhead is reduced.

The calculated repetition count is notified to the reception data decoding section 240, and the reception data decoding section 240 uses the MCS information notified by DCI and the repetition count to demodulate and decode the reception data (step S206). ). That is, demodulation corresponding to the modulation scheme notified by DCI is executed, and decoding corresponding to the coding rate notified by DCI is executed. And decoding accuracy can be improved by decoding repeatedly transmitted data.

As described above, according to the present embodiment, data is repeatedly transmitted based on the required SINR of data required by the MCS of transmission data and the required SINR of DCI required by the AGGR level of DCI. Determine the number of times. Since the user terminal apparatus calculates the number of repetitions based on the two required SINRs, it is possible to decode the repeatedly transmitted data without the control information that explicitly notifies the number of repetitions. As a result, an increase in overhead due to control information can be reduced.

In the above embodiment, the number of repetitions of data transmission is calculated using equation (1). However, the number of repetitions may be determined by referring to a prestored table, for example. . Specifically, for example, as shown in FIG. 8, a repetition count table that stores the number of repetitions of data transmission is referred to in association with the modulation multi-level number and coding rate of data and the AGGR level of DCI. good.

In the repetition count table shown in FIG. 8, for example, when the transmission data modulation scheme is BPSK (modulation multilevel number is 2), the coding rate is 1/9, and the AGGR level is two CCEs, the repetition count Is 0. For this reason, transmission data is transmitted only once and is not repeatedly transmitted. For example, even if the transmission data modulation scheme is BPSK (modulation multilevel number is 2) and the coding rate is 1/9, the number of repetitions is 1 when the AGGR level is 16 CCEs. . For this reason, the transmission data is transmitted once, then repeatedly transmitted once, and transmitted twice in total.

Thus, even if the MCS of the transmission data is the same, the number of repetitions increases as the DCGR AGGR level increases and the DCI required SINR decreases. This is equivalent to increasing the number of repetitions as the actual line quality is poor because the required SINR of DCI reflects the actual line quality reported by the CQI. On the contrary, even if the AGGR level of DCI is the same, the number of repetitions increases as the modulation multi-level number and coding rate of transmission data increase and the required SINR of data increases. This is equivalent to increasing the number of repetitions as the channel quality required by the MCS is better because the required SINR of the data is better than the actual channel quality reported by the CQI.

When using the repetition count table as described above, the base station apparatus 100 and the user terminal apparatus 200 hold the same repetition count table. Then, the transmission control unit 140 of the base station apparatus 100 determines the number of repetitions of data transmission by referring to the repetition number table. Also, the repetition count calculation unit 230 of the user terminal device 200 acquires the repetition count of the received data by referring to the repetition count table. Thereby, the base station apparatus 100 and the user terminal apparatus 200 can determine the same repetition number, without transmitting / receiving the control information which explicitly notifies the repetition number. Therefore, an increase in overhead due to control information can be reduced.

100a,

200b Processor

100b,

200c Memory

100c, 200a Radio transceiver 110, 210 FFT unit 120 CQI acquisition unit 130 AGGR level determination unit 140 Transmission control unit 150 Transmission data generation unit 160 Control channel generation unit 170

Multiplexing unit

180, 260 IFFT unit 220 Control Channel Decoding Unit 230 Repetition Count Calculation Unit 240 Received Data Decoding Unit 250 CQI Generation Unit

Claims

A receiving unit for receiving repeatedly transmitted data and control information indicating a modulation scheme and a coding rate of the data;
A first decoding unit for decoding the control information received by the receiving unit;
Based on the resource size allocated to the control information decoded by the first decoding unit and the modulation scheme and coding rate of the data indicated by the control information, the number of repetitions of the data transmitted repeatedly is obtained. An acquisition unit to
A terminal device comprising: a second decoding unit configured to decode data received by the receiving unit based on the number of repetitions acquired by the acquiring unit.
The acquisition unit
The first required channel quality required by the modulation scheme and coding rate indicated by the control information decoded by the first decoding unit, and the second required channel quality required by the resource size allocated to the control information The terminal device according to claim 1, wherein the number of repetitions is calculated from the difference.
The acquisition unit
The modulation scheme and coding rate indicated by the control information decoded by the first decoding unit with reference to a repetition count table that stores the repetition count in association with the data modulation scheme and coding rate and the resource size of the control information The terminal device according to claim 1, further comprising: acquiring a repetition count corresponding to the resource size allocated to the control information.
A selection unit for selecting a modulation scheme and a coding rate for generating transmission data;
A generating unit that generates control information indicating the modulation scheme and coding rate selected by the selecting unit;
A determination unit that determines the number of repetitions for repeatedly transmitting the transmission data based on the modulation scheme and coding rate selected by the selection unit and the resource size assigned to the control information generated by the generation unit When,
And a transmission unit that transmits the control information generated by the generation unit and repeatedly transmits the transmission data by the number of repetitions determined by the determination unit.
The determination unit is
The first required channel quality required by the modulation scheme and coding rate selected by the selection unit, and the second required channel quality required by the resource size allocated to the control information generated by the generation unit The base station apparatus according to claim 4, wherein the number of repetitions is calculated from the difference.
The determination unit is
Refer to the repetition count table that stores the repetition count in association with the data modulation scheme and coding rate and the resource size of the control information, and the modulation scheme and coding rate selected by the selection unit, and the generation unit The base station apparatus according to claim 4, wherein the number of repetitions corresponding to the resource size assigned to the generated control information is acquired.
A line quality information acquisition unit for acquiring line quality information of a line through which the transmission data is transmitted;
The selection unit includes:
5. The base station apparatus according to claim 4, wherein a modulation scheme and a coding rate corresponding to channel quality better than the channel quality indicated by the channel quality information acquired by the channel quality information acquiring unit are selected.
The generator is
8. The base station apparatus according to claim 7, wherein a resource size corresponding to the channel quality indicated by the channel quality information acquired by the channel quality information acquiring unit is allocated to the control information.
The transmitter is
A multiplexing unit that multiplexes the control information generated by the generation unit and the same transmission data for the number of repetitions determined by the determination unit, and generates a transmission signal;
The base station apparatus according to claim 4, further comprising: a wireless transmission unit that wirelessly transmits a transmission signal generated by the multiplexing unit.
A wireless communication system having a base station device and a terminal device,
The base station device
A selection unit for selecting a modulation scheme and a coding rate for generating transmission data;
A generating unit that generates control information indicating the modulation scheme and coding rate selected by the selecting unit;
A determination unit that determines the number of repetitions for repeatedly transmitting the transmission data based on the modulation scheme and coding rate selected by the selection unit and the resource size assigned to the control information generated by the generation unit When,
A transmission unit that transmits the control information generated by the generation unit and repeatedly transmits the transmission data by the number of repetitions determined by the determination unit;
The terminal device
A receiver that receives data transmitted by the transmitter and control information indicating a modulation scheme and a coding rate of the data;
A first decoding unit for decoding the control information received by the receiving unit;
Based on the resource size allocated to the control information decoded by the first decoding unit and the modulation scheme and coding rate of the data indicated by the control information, the number of repetitions of the data transmitted repeatedly is obtained. An acquisition unit to
A wireless communication system, comprising: a second decoding unit that decodes data received by the receiving unit based on the number of repetitions acquired by the acquiring unit.
A wireless communication method in a wireless communication system having a base station device and a terminal device,
The base station device
Select a modulation scheme and coding rate for generating transmission data,
Generating control information indicating the selected modulation scheme and coding rate;
Based on the selected modulation scheme and coding rate, and the resource size assigned to the generated control information, determine the number of repetitions to transmit the transmission data repeatedly,
While transmitting the generated control information, repeatedly transmitting the transmission data for the determined number of repetitions,
The terminal device is
Receives data transmitted by the base station apparatus and control information indicating the modulation scheme and coding rate of the data,
Decrypts the received control information,
Based on the resource size allocated to the decoded control information and the modulation scheme and coding rate of the data indicated by the control information, obtain the number of repetitions that the data was repeatedly transmitted,
A wireless communication method comprising: a process of decoding received data based on the obtained number of repetitions.