WO2019186919A1

WO2019186919A1 - Wireless communication method, wireless communication system, and terminal device

Info

Publication number: WO2019186919A1
Application number: PCT/JP2018/013320
Authority: WO
Inventors: 武志芥川; 義博河▲崎▼
Original assignee: 富士通株式会社
Priority date: 2018-03-29
Filing date: 2018-03-29
Publication date: 2019-10-03

Abstract

[Problem] When an error is included in received data and a NACK signal is transmitted to a transmission-side device, packet retransmission is not executed by the transmission-side device if the NACK signal is misdetermined as an ACK signal. [Solution] A wireless communication method in which there is used a wireless communication system that includes a transmission-side device and a reception-side device, wherein: the transmission-side device executes packet transmission to the reception-side device; the reception-side device determines whether an error is included in data; and, when it is determined that an error is included in the data and when the quality of a wireless signal between the transmission-side device and the reception-side device is less than or equal to a prescribed value, the reception-side device transmits a NACK signal to the transmission-side device multiple times.

Description

Wireless communication method, wireless communication system, and terminal device

The present disclosure relates to a wireless communication method, a wireless communication system, and a terminal device.

In the wireless communication, the base station and the terminal device execute transmission / reception of data using a wireless signal. For example, when data transmitted from the base station is received by the terminal device, the terminal device verifies whether or not an error is included in the received packet data. For example, in cyclic redundancy check (CRC), the base station calculates a remainder value obtained by dividing the data by a predetermined generator polynomial, and adds the calculated remainder value to the data as an error detection code (CRC code) for transmission. . Then, the terminal device that has received the data also uses the same generator polynomial to obtain a remainder value obtained by dividing the data, and by comparing with the error detection code notified from the transmitting device, there is an error in the received packet data. Determine whether it is included.

When the terminal device detects that the received data includes an error, a response signal (hereinafter referred to as “NACK signal”) indicating that the data includes an error is transmitted to the base station. The base station that has received the NACK signal performs data retransmission in accordance with the NACK signal. On the other hand, when no error is included in the received data, the terminal device transmits a response signal (hereinafter referred to as “ACK signal”) indicating that the data has been correctly received to the base station. In the following description of this specification, the “response signal” is used as a high-level concept word including both the ACK signal and the NACK signal.

However, an error may occur in the content of the response signal transmitted from the terminal device. That is, the base station that has received the response signal may mistakenly recognize the ACK signal as a NACK signal, or may mistakenly recognize the NACK signal as an ACK signal. Usually, the response signal does not include an error detection code such as a CRC code, and even if the response signal data includes an error, the base station cannot detect the error. As a result, if the base station misrecognizes the NACK signal as an ACK signal, data retransmission is not executed.

In preparation for such a case, a method has been developed in which the terminal device is set in advance so that the NACK signal is transmitted a plurality of times. However, this method causes a problem that radio resources are unnecessarily consumed because transmission of a NACK signal is executed a preset number of times. As another method, when the corresponding data is not retransmitted until a predetermined time elapses after the NACK signal is transmitted, a retransmission request signal different from the previously transmitted NACK signal is transmitted from the terminal device to the base station. A method of transmitting to a station is also being studied. However, in this method, since a retransmission request signal is transmitted after a predetermined time has elapsed since the transmission of a NACK signal, a delay of at least a predetermined time or more occurs with respect to data retransmission.

In recent years, for example, in the communication of the fifth generation mobile communication system (5G), data communication with high reliability and low delay is required as in, for example, Ultra Reliable and Low Latency Communications (URLLC).

Japanese Patent Laying-Open No. 2005-020590 JP-T-2004-518352

When the received data includes an error and the NACK signal is returned to the transmission side device, if the NACK signal is erroneously determined to be ACK by the transmission side device, the data re-transmission is not executed. A solution is desired.

An object of the present invention is to provide an appropriate solution to the problem that data retransmission is not performed when a NACK signal is erroneously determined to be ACK.

A wireless communication method using a wireless communication system including a first communication device and a second communication device that performs wireless communication with the first communication device, wherein the first communication device transmits the second communication of data. The second communication device determines whether a reception error has occurred for the data, and determines that the reception error has occurred, the second communication device determines that the reception error has occurred. A first response signal indicating the occurrence of the error is transmitted to the second communication device, and it is determined that the reception error has occurred, and a radio signal between the first communication device and the second communication device When the quality of the second communication device is equal to or lower than the first value, the second communication device transmits a second response signal indicating the occurrence of the reception error to the first communication device, and the first communication device At least one of the first response signal and the second response signal Based on one, a wireless communication method characterized by performing the retransmission of the data are disclosed.

According to the present invention, it is possible to suppress the problem that data retransmission is not performed properly.

It is a figure which shows the radio | wireless communications system containing a base station and a terminal device. It is a ladder chart regarding transmission / reception of data and transmission / reception of an ACK signal between a base station and a terminal device. It is a ladder chart regarding transmission / reception of data and transmission / reception of a NACK signal between a base station and a terminal device. It is a ladder chart about transmission / reception of data and transmission / reception of a NACK signal between a base station and a terminal device in a 1st Example, Comprising: The figure which shows a process when a NACK signal is misjudged as an ACK signal by the base station. is there. It is a hardware block diagram of the base station in 1st Example. It is a hardware block diagram of the terminal device in 1st Example. It is a functional block diagram of the processor of the base station in 1st Example. It is a functional block diagram of the processor of the terminal device in 1st Example. It is a figure which shows the example of a format of the response signal in 1st Example. It is a flowchart of the process performed by the processor of the base station in 1st Example. It is a flowchart of the process performed by the processor of the terminal device in 1st Example. It is a ladder chart regarding transmission / reception of data and transmission / reception of a NACK signal between the base station and the terminal device in the second embodiment, and is a diagram illustrating processing when the NACK signal is erroneously determined as an ACK signal. It is a figure for demonstrating the method for a terminal device to designate the modulation system of the data transmitted from a base station in 2nd Example. It is a figure for demonstrating the method for a terminal device to designate the modulation system of the data transmitted from a base station in 2nd Example. It is a functional block diagram of the processor of the terminal device in 2nd Example. It is a flowchart of the process performed by the processor of the terminal device in 2nd Example. It is a flowchart of the process performed by the processor of the base station in 2nd Example.

<First embodiment>
In the first embodiment, a method for reducing the possibility that data retransmission will not be executed even when a NACK signal transmitted from a terminal apparatus to a base station is erroneously determined as an ACK signal in the base station Is disclosed. In the first embodiment, if it is determined that an error is included in data transmitted from a first communication apparatus, for example, a base station, to a second communication apparatus, for example, a terminal apparatus, the terminal apparatus transmits a first NACK signal. To the base station. Furthermore, the terminal device specifies the signal quality of the radio signal between the base station and the terminal device, and transmits the second NACK signal to the base station when the signal quality is equal to or lower than the threshold value. The base station performs data retransmission based on at least one of the first NACK signal and the second NACK signal. As described above, when the data includes an error and the signal quality of the radio signal between the base station and the terminal device is equal to or lower than the threshold value, the NACK signal is transmitted to the base station a plurality of times. As a result, even if any one of the plurality of NACK signals is not correctly recognized by the base station, data retransmission is performed if another NACK signal is correctly recognized by the base station, thereby improving the reliability of wireless communication. Can keep. In addition, unnecessary consumption of radio resources can be suppressed as compared with a method in which the terminal apparatus is set in advance to execute transmission of a NACK signal multiple times. In addition, data retransmission can be performed earlier compared to a method in which a data retransmission request signal is transmitted when data retransmission based on a NACK signal is not performed within a predetermined time.

FIG. 1 is a diagram showing a wireless communication system including a base station 3 and a terminal device 4. The base station 3 is connected to a host device such as the server 2 via the network 1. The server 2 is, for example, an application server. Further, the base station 3 and the terminal device 4 are connected by a wireless link, and perform data transmission / reception.

FIG. 2 is a ladder chart regarding data transmission / reception and ACK signal transmission / reception between the base station 3 and the terminal device 4. In step S10, the base station 3 performs encoding processing and modulation processing on the transmitted data. Thereafter, the base station 3 transmits data to the terminal device 4 in the process S11.

In processing S20, the terminal device 4 receives the data transmitted from the base station 3. In process S21, the terminal device 4 performs demodulation processing and decoding processing on the received data. In step S22a, the terminal device 4 confirms whether or not the data includes an error based on an error detection code such as a CRC code added to the data. In the example of FIG. 2, it is assumed that no error is included in the data. In the process S23a, the terminal device 4 transmits a response signal (ACK signal) indicating that no error is included in the data to the base station 3. In step S12a, the base station 3 receives a response signal (ACK signal).

FIG. 3 is a ladder chart relating to data transmission / reception and NACK signal transmission / reception between the base station 3 and the terminal device 4. The processes having the same contents as those in FIG. After the demodulating process and the decoding process of the received data are completed in the process S21, the terminal apparatus 4 confirms whether or not an error is included in the data in the process S22b. Here, it is assumed that the data contains an error. In the process S23b, the terminal device 4 transmits a response signal (NACK signal) indicating that an error is included in the data to the base station 3. In step S12b, the base station 3 receives a response signal (NACK signal). In step S13a, the base station 3 performs data retransmission based on the received NACK signal. Note that the NACK signal includes information (for example, a data ID) that identifies data to be retransmitted. In the process S24a, the terminal device 4 receives the retransmitted data.

As described above, the response signal generally does not include an error detection code such as a CRC code. Therefore, when the terminal device 4 transmits a NACK signal as a response signal, an error occurs in the response signal data, and the base station 3 erroneously determines the response signal as an ACK signal. The error cannot be detected. As a result, the data requested by the terminal device 4 is not retransmitted. In preparation for such a case, a method in which the terminal device 4 transmits the NACK signal again will be described with reference to FIG.

FIG. 4 is a ladder chart relating to data transmission / reception and NACK signal transmission / reception between the base station 3 and the terminal device 4 in the first embodiment, and the NACK signal is erroneously determined to be an ACK signal by the base station 3. It is a figure which shows the process in a case. The processes having the same contents as those in FIG.

If the data transmitted from the base station 3 to the terminal device 4 includes an error, the terminal device 4 transmits a response signal (NACK signal) to the base station 3 in step S23b. In step S12b, the base station 3 receives a response signal (NACK signal). Here, it is assumed that the base station 3 erroneously determines the content of the received response signal as an ACK signal in the process S14. In this case, the base station 3 does not retransmit data.

On the other hand, when an error is detected in the data in the process S22b, the terminal apparatus 4 transmits a NACK signal in the process S23b and specifies the signal quality of the radio signal between the base station 3 and the terminal apparatus 4 in the process S26. . For example, a signal interference ratio (SIR) value is measured by the terminal device 4 as the reception quality of the downlink signal (downlink signal) from the base station 3 to the terminal device 4 at the terminal device 4. This SIR measurement may be performed after an error is detected in step S22b, or an SIR value measured before an error is detected may be used.

In process S27, the terminal device 4 determines whether or not to transmit the NACK signal again based on the specified signal quality. Specifically, when the SIR value as the signal quality is equal to or lower than a predetermined value, the terminal device 4 determines to retransmit the NACK signal. This is because if the signal quality is not good, it is considered that the NACK signal transmitted in the process S23b may not be correctly recognized as a NACK signal by the base station 3. In step S28a, the terminal device 4 transmits a response signal that is a NACK signal to the base station 3. In the following part of this specification, the response signal that is retransmitted based on the signal quality is referred to as a “re-response signal” for convenience.

The re-response signal transmitted from the terminal device 4 in the process S28a is received by the base station 3 in the process S16a. When it is determined that the received re-response signal is a NACK signal (process S17), the base station 3 performs retransmission of the target data in process S13a. The terminal device 4 receives the retransmitted data in the process S24a.

Since the NACK signal is transmitted again based on the signal quality of the radio signal between the base station 3 and the terminal device 4 by the method disclosed in FIG. 4, data retransmission from the base station 3 is executed. Probability can be increased.

FIG. 5 is a hardware configuration diagram of the base station 3 in the first embodiment. The base station 3 includes a wireless processing circuit 310, a processor 320, a nonvolatile memory 340, a volatile memory 350, and a network interface circuit 360. The radio processing circuit 310 performs frequency down-conversion, analog to digital (AD) conversion, and the like on the radio signal received by the antenna. In addition, the radio processing circuit 310 performs digital to analog (DA) conversion, frequency up-conversion, and the like on a radio signal transmitted from the antenna. The processor 320 executes data transmission processing to the terminal device 4, data retransmission processing for the NACK signal received from the terminal device 4, and the like. The processor 320 is a hardware processor, and includes a central processing unit (CPU), a micro control unit (MCU), a micro processing unit (MPU), a digital signal processor (DSP), and a field programmable processor (DSP). Circuit (ASIC) is also applicable.

The nonvolatile memory 340 is a computer-readable recording medium. The nonvolatile memory 340 stores a computer program executed by the processor 320 and the like. The non-volatile memory 340 includes, for example, Read Only Memory (ROM), Mask Read Only Memory (mask ROM), Programmable Read Only Memory (PROM), Flash Memory, Magnetoretic Memory Random Memory Random Access Memory. For example, Ferroelectric Random Access Memory (FeRAM). The computer program can be recorded on a storage medium other than the non-volatile memory 340 and a computer-readable recording medium (except for a carrier wave). Also, portable recording media such as Digital Versatile Disc (DVD) and Compact Disc Read Only Memory (CD-ROM) in which a computer program is recorded can be distributed. The computer program can be transmitted via a network.

The volatile memory 350 is a computer-readable recording medium. The computer program stored in the non-volatile memory 340 is loaded into the volatile memory 350. The volatile memory 350 holds data used for arithmetic processing by the processor 320, data that is the result of the arithmetic processing, and the like. The volatile memory 350 is, for example, Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), or the like.

The network interface circuit 360 is an interface device with the network 1.

FIG. 6 is a hardware configuration diagram of the terminal device 4 in the first embodiment. The terminal device 4 includes a wireless processing circuit 410, a processor 420, a nonvolatile memory 440, and a volatile memory 450. The wireless processing circuit 410 performs down conversion, AD conversion, and the like on the wireless signal received by the antenna. The wireless processing circuit 410 performs DA conversion, up-conversion, and the like on the wireless signal transmitted from the antenna. The processor 420 performs processing related to data transmission / reception with the base station 3, error detection processing, signal quality measurement processing, response signal generation processing, and the like. The processor 420 is a hardware processor, and in addition to a CPU, MCU, MPU, and DSP, an FPGA or an ASIC is also applicable.

The nonvolatile memory 440 is a computer-readable recording medium. The nonvolatile memory 440 stores a computer program executed by the processor 420 and the like. The nonvolatile memory 440 is, for example, a ROM, mask ROM, PROM, flash memory, MRAM, ReRAM, FeRAM, or the like. The computer program can be recorded on a storage medium other than the nonvolatile memory 440 and a computer-readable recording medium (excluding a carrier wave). In addition, portable recording media such as DVDs and CD-ROMs on which computer programs are recorded can be distributed. The computer program can be transmitted via a network.

The volatile memory 450 is a computer-readable recording medium. The computer program stored in the nonvolatile memory 440 is loaded into the volatile memory 450. The volatile memory 450 holds data used for arithmetic processing by the processor 420, data that is the result of the arithmetic processing, and the like. The volatile memory 450 is, for example, SRAM or DRAM.

FIG. 7 is a functional block diagram of the processor 320 of the base station 3 in the first embodiment. The processor 320 includes an encoding processing unit 321, a modulation processing unit 322, a transmission unit 323, a decoding processing unit 324, a demodulation processing unit 325, a receiving unit 326, a buffer unit 327, a response signal determination unit 328, and a retransmission processing unit 329. Function as.

The encoding processing unit 321 performs encoding processing on the transmitted data. The modulation processing unit 322 performs modulation processing on transmitted data. In the modulation process, the transmission signal is modulated based on a predetermined modulation method. Examples of the modulation method include a two-phase shift keying (BPSK) method, a four-phase shift keying (QPSK) method, and a quadrature transfer amplitude modulation (QAM) method. The transmission unit 323 executes data transmission processing.

The decryption processing unit 324 performs decryption processing on the received data. The demodulation processing unit 325 performs demodulation processing on the received data. The received data is added with modulation scheme information indicating which modulation scheme is used in the transmission side apparatus. The demodulation processing unit 325 specifies the modulation method of the modulation process performed by the transmission-side apparatus based on the modulation method information, and executes the demodulation process according to the specified modulation method. The receiving unit 326 performs data reception processing.

The buffer unit 327 holds data received from the server 1, for example. In addition, the buffer unit 327 holds the data transmitted to the terminal device 4 for a predetermined time after the transmission process. When a NACK signal from the terminal device 4 is received, a process for retransmitting data held in the buffer unit 327 is executed. The response signal determination unit 328 decodes the contents of the response signal and the reresponse signal received from the terminal device 4 and determines whether the response signal or the reresponse signal is an ACK signal or a NACK signal. The retransmission processing unit 329 executes data retransmission processing when it is determined that the received response signal or retransmission response signal is a NACK signal.

FIG. 8 is a functional block diagram of the processor 420 of the terminal device 4 in the first embodiment. The processor 420 includes an encoding processing unit 421, a modulation processing unit 422, a transmission unit 423, a decoding processing unit 424, a demodulation processing unit 425, a receiving unit 426, an error determination unit 427, a signal quality identification unit 428, and a response signal generation unit. 429 functions.

The encoding processing unit 421 performs an encoding process on data transmitted to the base station 3. The modulation processing unit 422 performs modulation processing on data transmitted to the base station 3. The transmission unit 423 executes transmission processing of data transmitted to the base station 3.

The decryption processing unit 424 performs a decryption process on the data received from the base station 3. The demodulation processing unit 425 performs demodulation processing on data received from the base station 3. The receiving unit 426 executes processing for receiving data from the base station 3.

The error determination unit 427 determines whether or not an error is included in the received data. For example, based on the CRC code added to the data, it is determined whether or not the data includes an error. The signal quality specifying unit 428 measures, for example, an SIR value as the signal quality of a radio signal between the base station 3 and the terminal device 4. The response signal generation unit 429 generates a response signal for the received data. If an error is detected by the error determination unit 427, a NACK signal is generated as a response signal. If no error is detected, an ACK signal is generated as a response signal. Further, the response signal generation unit 429 generates a reresponse signal that is a NACK signal when an error is detected and the signal quality of the radio signal is lower than a predetermined state.

FIG. 9 is a diagram showing a format example of a response signal in the first embodiment. The response signal includes a response signal ID assigned individually for each response signal. For example, different response signal IDs are attached to the response signal transmitted in the process S23b disclosed in FIG. 4 and the reresponse signal transmitted in the process S28a. Therefore, the base station 3 that receives these signals can individually identify the response signal and the re-response signal based on the response signal ID.

Further, the response signal includes information indicating whether the response signal is an ACK signal or a NACK signal. This information is, for example, 1-bit information. When this information is “1”, for example, the response signal is an ACK signal. When this information is “0”, the response signal is Indicates a NACK signal.

Further, when the response signal is a NACK signal, the response signal includes a data ID for specifying data to be retransmitted. As described above, the response signal transmitted in step S23b of FIG. 4 and the re-response signal transmitted in step S28a have different response signal IDs but the same data ID. Therefore, even if the response signal that is a NACK signal is erroneously determined to be an ACK signal in the process S14 of FIG. 4, if the reresponse signal is correctly determined to be a NACK signal in the process S17, the response signal is changed. The same data as the requested data is transmitted based on the re-response signal. When the response signal received by the base station 3 is correctly determined as a NACK signal and data is retransmitted, the base station 3 records the response signal ID and the data ID included in the response signal. deep. After that, when the re-response signal is received, the response signal and the re-response signal are issued for the same data by referring to the response signal ID and the data ID included in each of the response signal and the re-response signal. It is determined that Then, the base station 3 can perform control so as not to further transmit data based on the re-response signal.

FIG. 10 is a flowchart of processing executed by the processor 320 of the base station 3 in the first embodiment. The processing flow is started in process S50, and in process S51, the encoding processing unit 321 and the modulation processing unit 322 respectively perform encoding processing and modulation processing of transmitted data. In step S <b> 52, the transmission unit 323 transmits data to the terminal device 4.

After the process S52, the reception unit 326 determines whether a response signal from the terminal device 4 is received in the process S53. If it is determined that a response signal has been received (Yes in process S53), the process flow proceeds to process S54. If it is not determined that a response signal has been received (No in process S53), the process flow repeats process S53. . In step S54, the response signal determination unit 328 determines whether the received response signal is a NACK signal. When it is determined that the response signal is a NACK signal (Yes in process S54), the process flow returns to process S51, and the data encoding process, the modulation process, and the transmission process are executed again. On the other hand, when it is not determined that the response signal is a NACK signal (No in process S54), the process flow ends in process S59.

The process flow proceeds to process S55 after process S52. In step S55, the reception unit 326 determines whether a reresponse signal from the terminal device 4 has been received. If it is determined that a reresponse signal has been received (Yes in process S55), the process flow proceeds to process S56. If it is not determined that a reresponse signal has been received (No in process S55), the process flow is processed in process S59. End with.

In process S56, the response signal determination unit 328 determines whether the received reresponse signal is a NACK signal. If it is determined that the re-response signal is a NACK signal (Yes in process S56), the process flow proceeds to process S57. If it is not determined that the re-response signal is a NACK signal (No in process S56), the process proceeds to step S57. The flow ends in process S59.

In processing S57, the retransmission processing unit 329 determines whether or not data retransmission has already been performed on the response signal. If the response signal is determined to be a NACK signal in process S54 (Yes in process S54), the process flow returns to process S51, and data is retransmitted in process S52. Therefore, process S57 is executed in order to prevent a plurality of retransmission processes from being performed on the same data. If it is determined that retransmission has already been performed (Yes in process S57), the process flow ends in process S59. If it is not determined that the data has been retransmitted (No in process S57), the process flow proceeds to process S58. In step S58, the retransmission processing unit 329 executes retransmission of the data specified by the retransmission response signal to the terminal device 4. Thereafter, the process flow ends in process S59.

FIG. 11 is a flowchart of processing executed by the processor 420 of the terminal device 4 in the first embodiment. The processing flow is started by processing S70, and the reception unit 426 receives data transmitted from the base station 3 in processing S71. In step S72, the demodulation processing unit 425 and the decoding processing unit 424 execute demodulation processing and decoding processing, respectively. In step S73, the error determination unit 427 determines whether the received data includes an error. If it is determined that the data contains an error (Yes in process S73), the process flow proceeds to process S75. If it is not determined that the data contains an error (No in process S73), the process flow is processed in process S74. Proceed to

When the process flow proceeds to process S74, the response signal generation unit 429 generates a response signal (ACK signal) in process S74, and the generated response signal is transmitted to the base station 3. Thereafter, the process flow ends in process S79.

On the other hand, when the process flow proceeds to process S75, the response signal generation unit 429 generates a response signal (NACK signal) in process S75, and the generated response signal is transmitted to the base station 3. In process S76, the signal quality specifying unit 428 determines whether the signal quality of the radio signal is equal to or less than a threshold value. If it is determined that the signal quality is less than or equal to the threshold (Yes in process S76), the process flow proceeds to process S77. If the signal quality is not determined to be less than or equal to the threshold (No in process S76), the process flow is It progresses to process S78.

In process S77, the response signal generation unit 429 generates a reresponse signal that is a NACK signal, and the generated reresponse signal is transmitted to the base station 3. In process S78, the receiving unit 426 re-receives data. Here, the re-received data is data transmitted from the base station 3 based on either the response signal transmitted in the process S75 or the re-response signal transmitted in the process S77. After process S78, the process flow ends in process S79.

So far, the first embodiment has been disclosed. In the first embodiment, there is disclosed an example in which a re-response signal is transmitted when an error is included in data transmitted from the base station 3 and the SIR value in the downlink is not more than a predetermined value. It was. When the frequency of the radio signal used in the downlink and the frequency of the radio signal used in the uplink are close, in a situation where the SIR value in the downlink is low, the SIR value in the uplink is also low. May show. Therefore, it is possible to use the SIR value in the downlink instead of the SIR value in the uplink in determining whether or not to transmit the re-response signal. However, the first embodiment is not limited to using the signal quality of the radio signal used in the downlink in determining whether to transmit the re-response signal. For example, in determining whether or not to transmit a re-response signal, it may be determined whether or not to transmit a re-response signal using the SIR value in the uplink. In this case, the base station 3 measures the SIR value in the uplink. Then, the measured SIR value is notified from the base station 3 to the terminal device 4. The terminal device 4 transmits a re-response signal when an error is included in the received data and the SIR value in the uplink notified from the base station 3 is equal to or less than a predetermined value. With this method, it is possible to more accurately determine the possibility of an error occurring in the uplink in which the NACK signal is transmitted, and a determination as to whether or not to transmit a re-response signal is performed.

In the first embodiment, the case where an error is included in the data transmitted from the base station 3 and received by the terminal device 4 has been described. However, the present invention is not limited to the case where the value of the data transmitted from the base station 3 has changed in the wireless communication process due to interference of other signals, for example, when the terminal device 4 fails to receive data. It is also applicable to. For example, even when data to be received by the terminal device 4 is not received by the terminal device 4 in a predetermined period, or when an error occurs in the reception operation of the terminal device 4 and the data is not correctly received. The present invention is applicable. These errors are collectively referred to as “reception errors”.

<Second embodiment>
Next, a second embodiment will be disclosed. In the first embodiment, the terminal device 4 transmits a re-response signal that is a NACK signal to the base station when an error is included in the data received from the base station 3 and the signal quality of the radio signal is lower than a predetermined value. Sent to station 3. Accordingly, it is possible to suppress the possibility that the NACK signal is erroneously determined as the ACK signal in the base station 3 and the data retransmission is not executed. In the second embodiment, when transmitting a re-response signal, the terminal device 4 transmits the re-response signal including modulation method specifying information for specifying a modulation method for performing data re-transmission. The base station 3 that has received the re-response signal retransmits data based on the modulation scheme designation information included in the re-response signal. For example, assume that the modulation method in the first data transmission is the QAM method. In this case, in order to suppress the occurrence of an error again in the data retransmission, the terminal apparatus 4 changes the modulation scheme in the data retransmission to the base station 3 to a modulation scheme that is less likely to cause an error, for example, QPSK. Instruct to change to the method. Thereby, it is possible to suppress the occurrence of a data error again in data retransmission.

FIG. 12 is a ladder chart related to data transmission / reception and NACK signal transmission / reception between the base station 3 and the terminal device 4 in the second embodiment, and processing when a NACK signal is erroneously determined to be an ACK signal. FIG. The same processes as those disclosed in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

In process S11, the base station 3 transmits the modulated data to the terminal device 4. Here, when transmitting data, the base station 3 notifies the terminal device 4 of the downlink modulation scheme by adding modulation scheme information indicating the modulation scheme used in the wireless transmission of the data to the data. .

If an error is detected in the data in process S22b, a response signal that is a NACK signal is transmitted in process S23b, and the signal quality is specified in process S26. If the identified signal quality is equal to or lower than the predetermined value, the terminal device 4 determines to transmit a reresponse signal.

Further, the terminal device 4 generates modulation scheme designation information for designating a downlink modulation scheme when the specified signal quality is equal to or lower than a predetermined value. Specifically, the modulation scheme designation information is generated so that the data is retransmitted by a modulation scheme that is less likely to cause an error than the modulation scheme used in the modulation processing of step S10. For example, in the process S10, when the modulation process is performed by the QAM system, it is preferable that the data retransmission is performed using the QPSK system, which has a lower risk of error than the QAM system. In this case, the terminal apparatus 4 generates modulation scheme designation information so that data retransmission is performed using the QPSK scheme. In step S <b> 28 b, the terminal device 4 transmits a reresponse signal including the generated modulation scheme designation information to the base station 3. In step S16b, the base station 3 receives the re-response signal, and identifies the modulation method in the data retransmission processing based on the modulation method designation information included in the re-response signal. In step S13b, the base station 3 executes a modulation process based on the specified modulation method, and executes data retransmission. In step S24b, the terminal device 4 receives the retransmitted data.

FIG. 13 is a diagram for explaining a method for the terminal device 4 to specify the modulation method of data transmitted from the base station 3 in the second embodiment. FIG. 13A shows the correspondence between the modulation method and the Modulation and Coding Scheme (MCS) value. An MCS value is added to the data transmitted from the base station 3 to the terminal device 4 as modulation scheme information indicating the modulation scheme executed by the base station 3. The MCS value is divided into, for example, 10 levels from “0” to “9”. For example, the MCS value “0” corresponds to the BPSK method, and the MCS values “1” and “2” correspond to the QPSK method. The MCS values “3” and “4” correspond to the 16QAM system, the MCS values “5”, “6”, and “7” correspond to the 64QAM system, and the MCS values “8” and “9”. It corresponds to the 256QAM system.

FIG. 13B shows a table for specifying the changed value of the MCS value based on the SIR value. The terminal device 4 that has received the data acquires the MCS value added to the data. Further, the terminal device 4 specifies a value indicating the signal quality, for example, a downlink SIR value. Then, the change value of the MCS value is specified based on the difference value between the specific threshold value and the SIR value. For example, when the measured value of the SIR value is −80 dBm and the specific threshold value is −60 dBm, the difference value between the specific threshold value and the SIR value is −20 dBm. In this case, the change value of the MCS value is specified as “−2” by referring to the table shown in FIG. In this case, if the MCS value added to the data received from the base station 3 is “4”, for example, the terminal device 4 adds “−2” to “4”, so that the changed MCS value is “2” is obtained. Then, the terminal device 4 notifies the base station 3 of “2” that is the changed MCS value as the modulation scheme designation information. As shown in FIG. 13C, the terminal device 4 transmits modulation scheme designation information to, for example, a re-response notification signal and transmits it to the base station. The base station 3 sets the modulation scheme to the QPSK scheme based on the MCS value “2” that is the modulation scheme designation information included in the re-response notification signal, and executes data retransmission using the set QPSK scheme. . As a result, data retransmission can be executed by a modulation scheme that is less likely to cause errors than previous data transmission.

FIG. 14 is a diagram for explaining a method for the terminal device 4 to specify the modulation method of data transmitted from the base station 3 in the second embodiment. In the example disclosed in FIG. 13C, a method for instructing the modulation scheme to the base station 3 by including the MCS value (the MCS value after the change) for designating the modulation scheme in the re-response signal. Was disclosed. In the example disclosed in FIG. 14, the terminal device 4 instructs the base station 3 on the modulation scheme by adjusting the phase difference of the reresponse signal with respect to the reference signal. For example, when the change value of the MCS value is “−1”, the phase difference with respect to the reference signal is set to “90 °”, and when the change value of the MCS value is “−2”, the position with respect to the reference signal is set. When the phase difference is set to “180 °” and the change value of the MCS value is “−3”, the phase difference with respect to the reference signal is set to “270 °”. A re-response signal having a phase difference with respect to the reference signal set in this way is transmitted from the terminal device 4. Then, the base station 3 that has received the reresponse signal can recognize the change value of the MCS value by detecting the phase difference of the reresponse signal with respect to the reference signal. The base station 3 identifies the modulation scheme based on the changed value of the MCS value, and retransmits data using the identified modulation scheme.

FIG. 15 is a functional block diagram of the processor 420 of the terminal device 4 in the second embodiment. The processor 420 includes the encoding processing unit 421, the modulation processing unit 422, the transmission unit 423, the decoding processing unit 424, the demodulation processing unit 425, the reception unit 426, the error determination unit 427, and the response signal generation unit 429 disclosed in FIG. In addition, it functions as a modulation scheme designation unit 430.

The modulation scheme designation unit 430 generates modulation scheme designation information that designates a modulation scheme used when data is retransmitted when the terminal device 4 transmits a re-response notification to the base station 3. The generated modulation scheme designation information is notified to the base station 3 by the method shown in FIG. 13C or FIG.

FIG. 16 is a flowchart of processing executed by the processor 420 of the terminal device 4 in the second embodiment. The same processes as those disclosed in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Of the processing flow disclosed in FIG. 16, processing S70 to S79 are the same as the contents disclosed in FIG. If it is determined in process S76 that the signal quality is equal to or lower than the threshold value (Yes in process S76), the process flow proceeds to process S80. In step S80, the modulation scheme designation unit 430 generates modulation scheme designation information based on the modulation scheme information added to the data from the base station 3 and the signal quality of the radio signal. The generated modulation scheme designation information is notified to the base station 3 when the re-response signal is transmitted in step S77.

FIG. 17 is a flowchart of processing executed by the processor 320 of the base station 3 in the second embodiment. The same processes as those disclosed in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Of the processing flow disclosed in FIG. 17, processing S50 to processing S59 are the same as the content disclosed in FIG. If it is not determined in step S57 that data transmission for the response signal has already been performed (No in step S57), the process flow proceeds to step S60. In step S <b> 60, the modulation processing unit 322 specifies a modulation scheme used in data retransmission based on the modulation scheme designation information included in the reresponse signal from the terminal device 4. In step S58, data retransmission is performed using the specified modulation method.

As described above, the second embodiment has been disclosed. In the second embodiment, when the data from the base station 3 includes an error and the signal quality is equal to or lower than a predetermined value, a re-response signal that is a NACK signal is transmitted from the terminal device 4. Also, modulation scheme designation information for designating a modulation scheme used when data retransmission is executed is notified from the terminal device 4 to the base station 3. Thereby, it is possible to suppress the occurrence of an error in the data in the data retransmission.

DESCRIPTION OF SYMBOLS 1 Network 2 Server 3 Base station 4 Terminal device 310 Wireless processing circuit 320 Processor 340 Non-volatile memory 350 Volatile memory 360 Network interface circuit 410 Wireless processing circuit 420 Processor 440 Non-volatile memory 450 Volatile memory 321 Encoding processing unit 322 Modulation processing Unit 323 transmission unit 324 decoding processing unit 325 demodulation processing unit 326 reception unit 327 buffer unit 328 response signal determination unit 329 retransmission processing unit 421 encoding processing unit 422 modulation processing unit 423 transmission unit 424 decoding processing unit 425 demodulation processing unit 426 receiving unit 427 error determining unit 428 signal quality specifying unit 429 response signal generating unit 430 modulation method specifying unit

Claims

A wireless communication method using a wireless communication system including a first communication device and a second communication device that performs wireless communication with the first communication device,
The first communication device performs transmission of data to the second communication device;
The second communication device determines whether a reception error has occurred for the data;
When it is determined that the reception error has occurred, the second communication device transmits a first response signal indicating the occurrence of the reception error to the first communication device;
If it is determined that the reception error has occurred, and the quality of the radio signal between the first communication device and the second communication device is equal to or lower than a first value, the second communication device A second response signal indicating the occurrence of the reception error is transmitted to the first communication device;
The wireless communication method, wherein the first communication device performs retransmission of the data based on at least one of the first response signal and the second response signal.
The first communication device does not execute the retransmission of the data according to the second response signal when the retransmission of the data is performed according to the first response signal. The wireless communication method according to claim 1.
The second communication device is a first signal quality of a first radio signal transmitted from the first communication device and received by the second communication device, or transmitted from the second communication device and received by the first communication device. 3. The wireless communication method according to claim 1, wherein any one of the second signal qualities of the second radio signal is specified as the quality. 4.
The wireless communication method according to claim 3, wherein the first communication device adds the second signal quality to the data and transmits the data to the second communication device.
When the first communication device modulates the data using a first modulation method, the first communication device transmits the data including modulation method information specifying the first modulation method to the second communication device,
The second communication device identifies a second modulation scheme based on the modulation scheme information added to the data and the quality,
The second communication device transmits the second response signal including modulation scheme designation information for specifying the second modulation scheme to the first communication device;
When the first communication device performs the retransmission of the data in response to the second response signal, the first communication device determines the second modulation scheme based on the modulation scheme designation information included in the second response signal. The wireless communication method according to any one of claims 1 to 4, wherein the data is modulated by using the data.
The wireless communication method according to claim 1, wherein the first communication device is a base station, and the second communication device is a terminal device.
A first communication device;
A second communication device for performing wireless communication with the first communication device;
A wireless communication system comprising:
The first communication device performs transmission of data to the second communication device;
The second communication device determines whether a reception error has occurred for the data;
When it is determined that the reception error has occurred, the second communication device transmits a first response signal indicating the occurrence of the reception error to the first communication device;
If it is determined that the reception error has occurred, and the quality of the radio signal between the first communication device and the second communication device is equal to or lower than a first value, the second communication device A second response signal indicating the occurrence of the reception error is transmitted to the first communication device;
The wireless communication system, wherein the first communication device performs retransmission of the data based on at least one of the first response signal and the second response signal.
The first communication device does not execute the retransmission of the data according to the second response signal when the retransmission of the data is performed according to the first response signal. The wireless communication system according to claim 7.
The second communication device is a first signal quality of a first radio signal transmitted from the first communication device and received by the second communication device, or transmitted from the second communication device and received by the first communication device. The radio communication system according to claim 7 or 8, wherein any one of the second signal qualities of the second radio signal that has been determined is specified as the quality.
The wireless communication system according to claim 9, wherein the first communication device adds the second signal quality to the data and transmits the data to the second communication device.
When the first communication device modulates the data using a first modulation method, the first communication device transmits the data including modulation method information specifying the first modulation method to the second communication device,
The second communication device identifies a second modulation scheme based on the modulation scheme information added to the data and the quality,
The second communication device transmits the second response signal including modulation scheme designation information for specifying the second modulation scheme to the first communication device;
When the first communication device performs the retransmission of the data in response to the second response signal, the first communication device determines the second modulation scheme based on the modulation scheme designation information included in the second response signal. The wireless communication system according to any one of claims 7 to 10, wherein the data is modulated by using the data.
The wireless communication system according to any one of claims 7 to 11, wherein the first communication device is a base station, and the second communication device is a terminal device.
A terminal device that performs wireless communication with a base station,
An error determination unit that determines whether a reception error has occurred with respect to data transmitted from the base station;
When it is determined that the reception error has occurred, a first response signal indicating the occurrence of the reception error is generated, and when it is determined that the reception error has occurred, the base station and the terminal device A response signal generating unit that generates a second response signal indicating the occurrence of the reception error when the quality of the radio signal during the period is equal to or lower than the first value;
A terminal apparatus comprising: a transmission unit configured to transmit the first response signal and the second response signal to the base station.
Either the first signal quality of the first radio signal transmitted from the base station and received by the terminal device, or the second signal quality of the second radio signal transmitted from the terminal device and received by the base station The terminal device according to claim 13, further comprising: a signal quality specifying unit that specifies the quality as the quality.
When the base station modulates the data using the first modulation scheme, the data is added with modulation scheme information specifying the first modulation scheme,
The terminal device further includes a modulation scheme designating unit that identifies a second modulation scheme based on the modulation scheme information added to the data and the quality,
The terminal apparatus according to claim 13 or 14, wherein the transmission unit transmits the second response signal including modulation scheme designation information specifying the second modulation scheme to the base station.