JP6310384B2 - Error detection method, communication system, and communication apparatus - Google Patents

Description

  The present invention relates to an error detection method.

  In digital communication, error correction coding for correcting bit errors in received signals is performed for the purpose of reducing packet retransmission and improving communication efficiency. In particular, in wireless data communication such as wireless LAN or cellular wireless, convolutional coding is possible because of the advantage that the processing speed can be increased by sequential decoding during reception, and the coding rate can be finely controlled by puncture processing. Is widely used (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

  For example, Non-Patent Document 1 discloses 3GPP LTE (Long Term Evolution), and Non-Patent Document 2 discloses an error correction coding method in various wireless data communications such as IEEE 802.11, and a convolutional code is adopted. .

  On the other hand, in recent years, there has been a growing demand for remote monitoring and maintenance of facilities, or monitoring of energy consumption in the premises of factories, etc. from the center side away from the site. Since a cost increases when a communication cable is connected, and a monitoring target may move irregularly, a configuration for collecting sensor information by wireless communication has attracted attention. In these industrial wireless communications, convolutional codes are widely adopted (see, for example, Non-Patent Document 3).

JP 2014-053781 A JP 2004-040318 A

3GPP TS 36.212 v12.1.0, “Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding (Release 12)”, Section 5.1.3, 2014/07. IEEE Std 802.11-2011, "IEEE Standard for Information Technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications", Section 18.1.1, 2011/11 P. J. et al. Lee, “Further Results on Rate 1 / N Convolutional Code Constructions With Minimum Required SNR Criterion”, TDA Progress Report 42-80 pp. 97-102, 1984/12

  Although the convolutional code is excellent in random error correction capability, it is not suitable for correcting burst errors (locally continuous errors). For example, when using a convolutional code, the communication device determines that the bit error of the received packet can be corrected from the viewpoint of the bit error rate, but if the error occurs locally, it is actually accurate. May not be corrected.

  As a method for dealing with burst errors, for example, interleaving / deinterleaving processing is known (for example, see Non-Patent Document 1). In the interleaving / deinterleaving process, a transmission apparatus at the transmission source accumulates an input bit sequence having a predetermined number of bits, randomizes the input bit sequence with a predetermined pattern (interleaving process), and then transmits the input bit sequence to a transmission destination. . Then, the receiving-side communication device obtains an output bit sequence by applying (deinterleaving) a reverse pattern of the pattern applied in the transmission-source communication device to the received input bit sequence.

  By such interleaving / deinterleaving processing, even if a burst error occurs in communication, the output bit sequence is output as a bit sequence including a random error. For this reason, the communication device on the receiving side can improve the success rate of error correction by convolution decoding into the output bit sequence.

  However, the above-mentioned effect due to the randomization of the interleaving / deinterleaving process depends on the number of errors in the number of bits accumulated in the interleaving process. Specifically, when the number of errors that occur in communication is large, burst errors remain in the output bit sequence, and error correction by convolutional decoding may not succeed.

  For example, when a truck moves to load or unload a load or a person moves, the communication environment around the installed sensor changes, and the signal transmission time is relatively long. May occur. In this case, since the amount of sensor data collected from the sensor is small and the time for transmitting the sensor data is short, a large number of errors occur in the packet including the sensor data, and the interleaving / deinterleaving processing is effective. May not work.

  Furthermore, especially in wireless communication, since communication quality varies greatly compared to wired communication, burst errors may easily occur according to the speed of quality variation and communication speed.

  As described above, there is a method for detecting whether a random error or a burst error is dominant in a communication environment where a large burst error may occur with respect to the amount of data included in the packet.

  This method improves, for example, the arrival rate per packet such as the parity of an error correction code when random errors occur predominantly. Also, for example, when burst errors occur predominantly, communication efficiency is improved by allocating radio communication resources for packet retransmission and the like.

  As a method for detecting the occurrence status of a burst error, a method is known in which a bit error sequence of a received signal is acquired and the occurrence status of a burst error is determined by analyzing the bit error sequence (see, for example, Patent Document 1). . In Patent Document 1, two types of error rates (for example, a bit error rate before error correction and a bit error rate after error correction) are obtained as indices for the same received signal, and the indices obtained for a plurality of received signals Is plotted on a graph, and a method in which an index is plotted in a portion out of the majority is determined as a burst error.

  However, this method is based on the premise that random errors are dominantly generated, and there is a problem that a large number of samples to the extent that random errors are determined to be dominant are necessary.

  Conventionally, a method has been disclosed in which a burst state is determined by dividing it into a low burst state and a high burst state, and the occurrence status of a burst error is analyzed in more detail (see, for example, Patent Document 2). However, since this method performs a plurality of processes for each bit of the received signal, a large amount of memory and processing are required.

  Therefore, when the technique of Patent Document 2 is applied to the sensor and its peripheral devices, it is difficult to implement from the viewpoint of the memory amount and the processing amount. In addition, for example, even if the technique of Patent Document 2 is applied and communication transmitted from sensors or the like is collected and processed in a place such as a monitoring center, the communication cost for collecting is high. Therefore, there is a problem that it is difficult to implement in an industrial field such as remote monitoring.

  The present invention is an invention for solving the above-described problems, and provides a burst error determination method that requires a small number of samples and requires a small amount of processing.

  In order to solve the above-described problem, the present invention provides an error detection method in a communication device that transmits and receives a signal, wherein the communication device uses a plurality of information units of a predetermined amount greater than 1 bit included in a received signal. A first procedure for calculating an index indicating an error amount to be generated; and a second procedure for determining whether or not the communication apparatus is likely to have a burst error in the received signal using the index. Procedures.

  According to the present invention, it is possible to provide a burst error detection method that requires a small amount of processing and requires a small number of samples.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a block diagram which shows the structure of the remote monitoring system of Example 1. FIG. 3 is a functional block diagram of a communication apparatus according to Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of a physical device included in a communication device according to Embodiment 1. FIG. 3 is a flowchart illustrating processing of the communication apparatus according to the first embodiment. 6 is an explanatory diagram illustrating a part of a parameter management table according to Embodiment 1. FIG. FIG. 3 is an explanatory diagram illustrating a frame format according to the first embodiment. It is explanatory drawing which shows the evaluation value table of Example 1. FIG. 6 is an explanatory diagram illustrating a comparison table including a bit error sequence according to the first embodiment. FIG. FIG. 6 is an explanatory diagram illustrating a bit error sequence in which a random error occurs in Example 1 and a bit error sequence in which a burst error occurs. It is explanatory drawing which shows cumulative frequency distribution of ratio (alpha) of Example 1. FIG. 6 is a flowchart illustrating processing of the communication apparatus according to the second embodiment. 10 is a flowchart illustrating processing of the communication apparatus according to the third embodiment.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals indicate the same operation, and therefore description thereof is omitted.

  FIG. 1 is a block diagram illustrating the configuration of the remote monitoring system according to the first embodiment.

  The remote monitoring system described below includes at least one sensor device 101, at least two communication devices 102 and 103, and one center device 104. However, the remote monitoring system according to the present embodiment may be any system including two communication devices, for example, a system in which two communication devices communicate by wire.

  The sensor device 101 has a function of collecting information such as temperature or pressure from a device (such as a generator or a motor) or a structure (such as a piping facility or a wall) and inputting the collected information to the communication device 102. The sensor device 101 includes, for example, a sensor and a PC (Personal Computer).

  The communication device 102 transmits the information input by the sensor device 101 to the communication device 103 by wireless communication, for example. The communication device 103 inputs the received information to the center device 104. The communication apparatus 103 of this embodiment determines whether a burst error has occurred.

  The center device 104 accumulates information collected from one or a plurality of sensor devices 101, for example, according to a request from an operator or an administrator (hereinafter referred to as an operator) in the remote monitoring system of the present embodiment. It has a function to display the information. The center device 104 is a computer composed of a storage device and a processor, for example.

  The processing of the first embodiment will be described with reference to FIGS. The communication apparatus 103 according to the first exemplary embodiment includes an area in which the content transmitted by the communication apparatus 102 is preset in the communication apparatus 103 in the area of the signal received from the communication apparatus 102, or the content transmitted by the communication apparatus 102. The occurrence of a burst error is determined using an area (known part) that the communication apparatus 103 can predict.

  FIG. 2 is a functional block diagram of the communication apparatus 103 according to the first embodiment.

  In the specific low power radio and IEEE 802.15.4, there is no significant difference in the communication function between nodes. Therefore, the communication device 102 and the communication device 103 have the same function. Although the function and configuration of the communication device 103 will be described below, the communication device 102 also has the same function and configuration.

  The communication apparatus 103 includes functional units of an antenna 1101, a wireless transmission / reception unit 1102, a control unit 1103, a baseband demodulation unit 1104, a decoding unit 1105, a network interface unit 1106, an encoding unit 1107, and a baseband modulation unit 1108.

  The wireless transmission / reception unit 1102 has the yesterday to convert the radio frequency signal input from the antenna 1101 into a baseband signal and output the converted signal to the baseband demodulation unit 1104.

  Baseband demodulation section 1104 demodulates the input signal in accordance with the modulation method instructed from control section 1103. Baseband demodulation section 1104 then outputs the demodulated result to decoding section 1105.

  The decoding unit 1105 performs error correction processing according to the error correction code method and parameters specified by the control unit 1103. Then, after decoding the data, the decoding unit 1105 outputs the data to the network interface unit 1106, and outputs the control information and the decoding result to the control unit 1103.

  The decoding unit 1105 according to the first embodiment extracts a reception bit sequence in an area corresponding to a known portion of a transmitted signal from the demodulated signal input from the baseband demodulation unit 1104, and the extracted reception bit sequence is a control unit Output to 1103.

  Also, the decoding unit 1105 according to the second embodiment outputs the Path Metric value of the output path of Viterbi decoding and the maximum value of the Branch Metric value in a predetermined predetermined amount of information bits to the control unit 1103.

  The network interface unit 1106 outputs the output of the decoding unit 1105 to the center device 104 via wired communication or wireless communication. In addition, when a signal is input from the center device 104, the network interface unit 1106 outputs the input information to the encoding unit 1107.

  The encoding unit 1107 receives information input from the network interface unit 1106. Also, the encoding unit 1107 receives control information generated inside the communication device 103 and sent to the communication device 103 from the control unit 1103.

  The encoding unit 1107 encodes the input information in accordance with the error correction code information acquired from the control unit 1103. After that, encoding section 1107 inputs the encoded information to baseband modulation section 1108.

  The baseband modulation unit 1108 modulates the input from the encoding unit 1107 according to the modulation method instructed by the control unit 1103, and generates a baseband signal.

  When a baseband signal is input from the baseband modulation unit 1108, the radio transmission / reception unit 1102 converts the input baseband signal into a radio frequency signal, and then outputs the signal to the sensor device 101 via the antenna 1101. .

  The control unit 1103 is a subject of processing of the communication device in the present embodiment. The control unit 1103 manages an error correction code and a modulation method applied to the transmitted information. Further, the control unit 1103 determines whether or not to input the output of the decoding unit 1105 to the network interface unit 1106 based on the decoding result input from the decoding unit 1105.

  In the information reception process, the control unit 1103 instructs the baseband demodulation unit 1104 to perform a modulation method, and instructs the decoding unit 1105 to perform an error correction code method. In the information transmission process, the control unit 1103 generates control information, notifies the encoding unit 1107 of the control information and the error correction code method, and instructs the baseband modulation unit 1108 about the modulation method.

  In addition, the control unit 1103 of the communication apparatus 103 according to the present embodiment determines whether to perform burst error determination. Then, the control unit 1103 determines the burst error rate based on the input from the decoding unit 1105, and determines whether it is necessary to change the coding rate of the error correction code or the number of packet retransmissions.

  As a result of the determination, when it is necessary to change the coding rate of the error correction code or the number of packet retransmissions, the control unit 1103 of the communication apparatus 103 sends a parameter such as the coding rate of the error correction code or the number of packet retransmissions to the communication apparatus 102. The control information for requesting the change is generated. Then, the control unit 1103 of the communication apparatus 103 transmits the generated control information to the encoding unit 1107.

  In addition, the control unit 1103 of the communication device 102 changes the control information notified from the decoding unit 1105 if the control information received from the communication device 103 is a request for changing a parameter such as an error correction code encoding rate or the number of packet retransmissions. The requested parameter is changed according to the control information.

  The functional units of the communication device 102 and the communication device 103 may be each implemented by a physical device such as an integrated circuit, or may be implemented by software such as a program.

  FIG. 3 is a block diagram illustrating a configuration of a physical device included in the communication device 103 according to the first embodiment.

  The communication device 103 may be implemented by a computer shown in FIG. The communication device 103 includes a processor 1201, a data buffer 1202, and a processing unit of a memory 1203, and each processing unit is connected by an internal bus 1204.

  Furthermore, the communication apparatus 103 includes a wireless transmission / reception unit 1112, a network interface 1116, and an input / output interface 1113 as physical interfaces to external nodes. In addition, the communication device 103 includes a storage device 1205 that stores programs and tables.

  When the functional unit illustrated in FIG. 2 is implemented by software, the storage device 1205 may include a program corresponding to the functional unit illustrated in FIG.

  The processor 1201 executes a program stored in the storage device 1205. In addition, the processor 1201 implements the processing of the functional units illustrated in FIG. 2 such as the control unit 1103 by executing a program.

  The data buffer 1202 temporarily stores information received from the center device 104 or the sensor device 101 or information obtained by error-correction coding of the information for transmission to the center device 104 or the sensor device 101. The data buffer 1202 temporarily stores, for example, information indicating whether the control information has been received, or control information generated by the communication device such as a request for changing the coding rate of the error correction code or the number of packet retransmissions. .

  The data buffer 1202 also temporarily stores the code word generated by the encoding unit 1107 and the control information generated by the control unit 1103. The data buffer 1202 also temporarily stores information used for burst error determination in this embodiment, such as the number of packets whose BER exceeds a threshold.

  A memory 1203 is a storage area in which a program processed by the processor 1201 is expanded, and holds data necessary for processing.

  The wireless transmission / reception unit 1112 and the network interface 1116 are physical devices for mounting the wireless transmission / reception unit 1102 and the network interface unit 1106 shown in FIG.

  The wireless transmission / reception unit 1112 is a device for the communication device 102 and the communication device 103 to communicate wirelessly. The wireless transmission / reception unit 1102 includes a duplexer, a power amplifier, a low noise amplifier, an up converter, a down converter, an analog / digital converter, a digital / analog converter, an automatic frequency adjuster, and an automatic gain adjuster.

  The network interface 1116 is an interface for transmitting and receiving signals to and from the center device 104 or the sensor device 101.

  The input / output interface 1113 is an interface for connecting an input device for an operator or the like to input an instruction to the communication device and an output device for outputting a processing result in the communication device to the operator or the like.

  The input device is, for example, a mouse or a keyboard, and the output device may be, for example, a printer or a display, or may be a device that lights up, such as an LED. Further, the input device and the output device may be implemented by a single device such as a tablet terminal.

  The storage device 1205 is a storage device such as a nonvolatile memory or a hard disk drive. The storage device 1205 stores a communication control program 1206, a determination index recording program 1207, a burst error determination program 1208, and a parameter management table 1209. Note that the storage device 1205 may store any program and information corresponding to processing in the communication device 102 and the communication device 103 in addition to the above-described program and information.

  The processor 1201 implements the function of the control unit 1103 in FIG. 2 by executing the communication control program 1206, the determination index recording program 1207, and the burst error determination program 1208.

  The communication control program 1206 has a function of updating the parameter management table 1209 based on control information sent from the decoding unit 1105 and the network interface unit 1106, and generates control information based on the parameter management table 1209, It has a function of storing the generated control information in the data buffer 1202 and also has a function of holding unreachable packets in the data buffer 1202 until a predetermined number of packet retransmissions is reached based on the parameter management table 1209.

  Further, the communication control program 1206 directs the error correction code information (method and parameters, etc.), the control information, the modulation method parameters, and the like by the encoding unit 1107 indicated by the parameter management table 1209 to the baseband modulation unit 1108. Output function. Further, the communication control program 1206 notifies the baseband demodulator 1104 of the modulation method parameters indicated by the parameter management table 1209, and further notifies the decoding unit 1105 of information on the error correction code indicated by the parameter management table 1209. It has a function.

  The determination index recording program 1207 has a function of instructing the decoding unit 1105 to store an index used for determination by the burst error determination program 1208 or information for calculating the index in the data buffer 1202. The determination index recording program 1207 according to the first embodiment records a received bit sequence of a known part of a transmitted signal as information for calculating an index. The determination index recording program 1207 according to the second embodiment records a Viterbi decoding metric value as an index used for determination.

  Note that the communication device 103 according to the first embodiment may set a known portion of a signal to be transmitted in advance using a signal format.

  The burst error determination program 1208 has a function of determining the bit error rate and the presence / absence of a burst error in a received packet based on information stored in the data buffer 1202. Then, the burst error determination program 1208 generates a control signal for requesting an increase in the number of packet retransmissions according to the determination result, or control information for requesting a decrease in the coding rate of the error correction code. A function to input to the conversion unit 1107.

  The parameter management table 1209 includes a modulation method, an error correction code and coding rate, the number of packet retransmissions, and information used for burst error determination processing (SER / BER threshold, packet retransmission number and coding rate of error correction code) For example, a threshold value for determining whether or not the change is necessary.

  FIG. 4 is a flowchart illustrating processing of the communication apparatus 103 according to the first embodiment.

  The determination index recording program 1207 executes processing 203 and processing 204 shown in FIG. 4, and the burst error determination program 1208 executes other processing shown in FIG.

  When the burst error determination program 1208 of the communication apparatus 103 is activated in the remote monitoring system of the present embodiment, it first acquires a threshold value used for a predetermined burst error determination process from the data buffer 1202, and the acquired threshold value is parameter-managed. This is set in the table 1209 (201).

  FIG. 5 is an explanatory diagram illustrating thresholds included in the parameter management table 1209 according to the first embodiment.

  The parameter management table 1209 holds thresholds used for burst error determination processing in a table format as shown in FIG. 5, for example. FIG. 5 shows only the parameters 301, 304, 302, and 303 included in the parameter management table 1209, but the parameter management table 1209 of the present embodiment includes other parameters such as a coding rate and the number of retransmissions.

  The parameter 301 is a threshold value that is compared with the BER per packet in the process 209. The parameter 304 is a threshold value compared with the ratio of SER to BER (a ratio α described later) in the process 211.

  The parameter 302 is a threshold value used to determine whether it is necessary to execute the method for reducing the BER in the process 213. The parameter 302 is a threshold value that is compared with the ratio of packets having a BER equal to or greater than a threshold value (parameter 301) with respect to the total number of received packets.

  The parameter 303 is a threshold value used in the process 214 to determine whether or not a burst error has predominantly occurred in a plurality of received packets. The parameter 303 is a threshold value that is compared with the ratio of packets determined to be burst errors to the total number of received packets.

  After the process 201, the burst error determination program 1208 determines whether to perform burst error determination (202). In the process 202, the burst error determination program 1208 may determine, for example, that burst error determination is performed when a predetermined time has elapsed since the previous determination process, or a communication quality index such as a packet arrival rate. May be determined to perform burst error determination when the value falls below a predetermined threshold.

  If it is determined not to perform burst error determination, the determination index recording program 1207 receives, for example, a packet including sensor information or control information from the communication apparatus 102 (203). Then, the determination index recording program 1207 extracts a received bit sequence corresponding to a portion where the transmission signal is known from the received packet. Then, the determination index recording program 1207 records the extracted received bit sequence in the data buffer 1202 or the like (204).

  The known part of the transmitted signal is determined by the prior art (IEEE Std 802.15.4-2011, "IEEE Standard for Local and metropolitan area networks-Part 15.4: Low-Rate Wireless LTE. -WPANs) "See Section 5.2, 2011/9). For example, a beacon signal periodically transmitted, a physical layer header, or MAC layer header information is used as a known portion of the transmitted signal.

  FIG. 6 is an explanatory diagram illustrating the frame format 400 according to the first embodiment.

  A frame format 400 shown in FIG. 6 is a frame format defined by IEEE 802.15.4g. The frame format 400 includes areas 401 to 403.

  Area 401 is a beacon signal. The contents of the area 401 indicate a sequence number and fixed system information. When the communication apparatus 103 holds the sequence number indicated by the area 401 in advance, the communication apparatus 103 can predict the contents to be included in the area 401 in the received signal.

  For this reason, the determination index recording program 1207 holds information for specifying the region 401 in advance as information indicating a known part of the transmitted signal, and the region 401 included in the received signal is received in the received bit sequence in the process 204. May be extracted as

  An area 402 is a MAC header. An area 403 is a synchronization header for synchronizing the MAC header.

  The contents of the area 402 are not changed except for the sequence number if the transmission side and the reception side have the same address. For this reason, since the area 403 is a bit sequence whose value does not change, the communication apparatus 103 can predict the transmission contents of the area 403.

  For this reason, the determination index recording program 1207 holds information for specifying the areas 402 and 403 in advance as information indicating a known part of the transmission signal, and the area 403 included in the received signal is received in the process 204. You may extract as a series.

  When it is determined in the process 202 that burst error determination is performed, the burst error determination program 1208 initializes the counters c1 and c2 that are arguments held in advance by updating them to 0 (205, 206). Then, processing 207 to processing 212 are repeatedly executed for the received bit sequence included in each of the received N packets.

  In the following, the content that should be included in the region of the received bit sequence in the transmitted signal is referred to as a predicted value. In addition, the value of the recorded received bit sequence in the signal received from the communication apparatus 102 is described as a received value.

  First, the burst error determination program 1208 extracts a received value of one received bit sequence from the data buffer 1202 and its predicted value. Then, the burst error determination program 1208 obtains a bit error sequence indicating an error occurring in the received bit sequence by specifying a bit (digit position) where the extracted predicted value of the received bit sequence differs from the actual received value. .

  Then, the burst error determination program 1208 calculates a bit error rate (BER) using the obtained bit error sequence (207). The burst error determination program 1208 calculates, as a BER, a value obtained by dividing the number of errors generated in one received bit sequence by the total number of bits included in the received bit sequence.

  Further, the burst error determination program 1208 calculates an error rate (SER) of symbols including consecutive k bits using the obtained bit error sequence (208). A symbol is a unit of a bit sequence generated as a result of dividing a bit error sequence by k bits. The burst error determination program 1208 calculates, as SER, a value obtained by dividing the number of symbols in which an error has occurred by the total number of symbols included in one received bit sequence.

  After the processing 208, the burst error determination program 1208 performs processing 209, 210, and 213, and the BER with respect to the total number of packets (that is, received bit sequences) is equal to or greater than a predetermined threshold (corresponding to the parameter 301 of the parameter management table 1209) The ratio of the number of packets (that is, the received bit sequence) is calculated. Also, the burst error determination program 1208 calculates a burst error rate by processing 211, 212, and 214.

  Specifically, the burst error determination program 1208 compares the threshold acquired from the parameter 301 of the parameter management table 1209 with the BER calculated in the process 207 and determines whether the calculated BER is equal to or greater than the acquired threshold. (209). When the calculated BER falls below the acquired threshold value, the burst error determination program 1208 maintains the value of the counter c1.

  If the calculated BER is greater than or equal to the acquired threshold, the burst error determination program 1208 counts up the counter c1 (210). The program of this embodiment counts up the argument by adding 1 to the argument (for example, counters c1 and c2).

  When the calculated BER falls below the acquired threshold value or after the process 210, the burst error determination program 1208 calculates a ratio α obtained by normalizing the SER calculated in the process 208 using the calculated BER. The burst error determination program 1208 acquires the threshold value of the parameter 304 of the parameter management table 1209, and determines whether the calculated ratio α is equal to or greater than the acquired threshold value (211). When the calculated ratio α is less than the acquired threshold value, the burst error determination program 1208 maintains the value of the counter c2.

  When the calculated ratio α is equal to or greater than a predetermined threshold, the symbol error rate is sufficiently high with respect to the bit error rate, and there is a high possibility that a local error has occurred in one packet. Therefore, the burst error determination program 1208 counts up the counter c2 (212). The burst error determination program 1208 maintains the value of the counter c2 when it is less than the predetermined threshold value.

  Note that the threshold used in the process 211 may be a range of the ratio α, not the lower limit value of the ratio α that is determined to have a high possibility of occurrence of a burst error. When the ratio α is specified by a value range, the ratio α may be stored in the parameter management table 1209 or may be stored in a table such as the evaluation value table 1210 shown in FIG.

  FIG. 7 is an explanatory diagram illustrating an evaluation value table 1210 according to the first embodiment.

  The evaluation value table 1210 may be stored in the storage device 1205. The evaluation value table 1210 includes a BER 1211, a SER lower limit value 1212, and a SER upper limit value 1213. The evaluation value table 1210 is set in advance by an operator or the like. The evaluation value table 1210 indicates a range of SER values in which a burst error is considered to have occurred per calculated BER.

  BER1211 shows BER. The SER lower limit value 1212 indicates the lower limit value of the SER at which there is a high possibility that a burst error has occurred in the BER indicated by the BER 1211. The SER upper limit value 1213 indicates the upper limit value of the SER that has a high possibility that a burst error has occurred in the BER indicated by the BER 1211.

  In process 211, the burst error determination program 1208 extracts an entry whose BER calculated in process 207 corresponds to BER 1211 from the evaluation value table 1210, and the calculated ratio α is equal to or greater than the value of the SER lower limit 1212 of the extracted entry. Yes, and it is determined whether it is below the SER upper limit 1213. The burst error determination program 1208 determines that there is a high possibility that a burst error has occurred when the calculated ratio α is equal to or greater than the value of the SER lower limit value 1212 and is lower than the SER upper limit value 1213.

  The burst error determination program 1208 can calculate a ratio α indicating how errors are distributed in a packet by using the result of dividing SER by BER as the ratio α. By using, it can be determined that there is a high possibility that a burst error has occurred.

  If it is not determined in process 211 that there is a high possibility that a burst error has occurred, or after process 212, burst error determination program 1208 executes processes 207 to 212 for other received bit sequences.

  After executing processing 207 to processing 212 for all received bit sequences, the burst error determination program 1208 normalizes the counter c1 by dividing the counter c1 by the total number N of received packets. The normalized counter c1 is a ratio of the number of packets whose BER is equal to or greater than a predetermined threshold to the total number of received packets.

  Then, the burst error determination program 1208 determines whether the normalized counter c1 is equal to or larger than the threshold acquired from the parameter 302 of the parameter management table 1209 (213).

  If the normalized counter c1 is below the acquired threshold, the BER is relatively low and no processing to reduce the BER is necessary. Therefore, the burst error determination program 1208 returns to the process 202.

  If the normalized counter c1 is equal to or greater than the acquired threshold, the burst error determination program 1208 determines that the BER is high, and determines a BER reduction method according to the burst error rate. Specifically, the burst error determination program 1208 obtains the normalized counter c2 by dividing the counter c2 by the total number N of packets.

  The normalized counter c2 is a burst error rate in a plurality of received packets. The burst error determination program 1208 determines whether the normalized counter c2 is equal to or greater than the threshold acquired from the parameter 303 of the parameter management table 1209 (214).

  When the normalized counter c2 is less than the threshold acquired from the parameter 303, the burst error determination program 1208 determines that the random error is dominant, and reduces the coding rate of the convolutional code, for example, To increase the accuracy of 216 (216). In the process 216, the burst error determination program 1208 may determine any method and parameter as a method for reducing the BER as long as the random error can be improved.

  If the normalized counter c2 is equal to or larger than the threshold value acquired from the parameter 303, the burst error determination program 1208 determines that the burst error is dominant and decides to increase the number of packet retransmissions, for example. (215). In the process 215, the burst error determination program 1208 may determine any method and parameter as a method for reducing the BER as long as the burst error can be improved.

  After determining the BER reduction method or parameter in the process 215 or 216, the burst error determination program 1208 requests the communication apparatus 102 for the determined method or parameter using, for example, an upper layer control signal (217). ).

  The decoding unit 1105 of the communication apparatus 102 detects the notified control signal as control information, and inputs the control information to the control unit 1103. The control unit 1103 of the communication apparatus 102 updates the coding rate in the parameter management table 1209 or the number of packet retransmissions according to the input control information.

  Thereby, the communication control program 1206 updates the number of times to instruct packet retransmission or the coding rate input to the coding unit 1107.

  In FIG. 4 described above, the burst error determination program 1208 may determine the method or parameter for reducing the BER based only on the determination result of the burst error rate in the process 214 without executing the process 213.

  FIG. 8 is an explanatory diagram illustrating a comparison table 500 including a bit error sequence according to the first embodiment.

  Details of the BER calculation process in the process 207 and the SER calculation process in the process 208 will be described below. The bit error sequence used for the calculation of BER and SER is obtained by using a generated comparison table 500 as shown in FIG. 8, for example.

  The data buffer 1202 stores the comparison table 500. The comparison table 500 includes a received bit sequence 501, a predicted value 502, and a bit error sequence 503. The determination index recording program 1207 stores the received bit sequence extracted in the process 204 in the received bit sequence 501.

  The predicted value 502 may be a value set in advance, or may be a value predicted by the determination index recording program 1207 from the contents of a packet received in the past. The burst error determination program 1208 obtains the value of the bit error sequence 503 based on the values of the received bit sequence 501 and the predicted value 502.

  The burst error determination program 1208 compares the received bit sequence 501 and the predicted value 502 for each digit position. If the received bit sequence 501 and the predicted value 502 are the same value, the burst error determination program 1208 sets the value of the digit position of the bit error sequence. A bit error sequence is obtained by setting 0 as a different digit to 1. 1 in the bit error sequence of this embodiment indicates that an error has occurred. Then, the burst error determination program 1208 stores the generated bit error sequence in the bit error sequence 503.

  Note that the burst error determination program 1208 may obtain a plurality of bit error sequences 503 at the timing of performing burst error determination (timing for executing the processing from the processing 205). The burst error determination program 1208 may obtain the bit error sequence 503 at the timing of receiving a signal from the communication apparatus 102 (timing of processing 204) and hold only the bit error sequence 503.

  The burst error determination program 1208 according to the first embodiment can detect the occurrence of an error by generating a bit error sequence based on the predicted value and the received bit sequence.

  Details of the burst error rate determination method will be described with reference to FIGS. 9 and 10.

  FIG. 9 is an explanatory diagram illustrating a bit error sequence in which a random error has occurred and a bit error sequence in which a burst error has occurred according to the first embodiment.

  A symbol error 601 shown in FIG. 9 is a symbol error in the bit error sequence 602. In the bit error sequence 602, a random error has occurred.

  A symbol error 603 is a symbol error in the bit error sequence 604. In the bit error sequence 604, a burst error has occurred.

  By using an error (symbol error) in units of symbols including a plurality of consecutive bits as an index, the burst error determination program 1208 can evaluate the error occurrence state at the macro level and evaluate the burstiness of the error.

  For example, one symbol in FIG. 9 includes 8 bits. The bit error sequences 602 and 604 are each 32 bits, and a 3-bit error occurs. For this reason, the BERs of the bit error sequences 602 and 604 are the same.

  However, the symbol error 601 is 3/4 and the symbol error 603 is 1/4. For this reason, the symbol error 603 is 1/3 of the symbol error 601.

  Therefore, the burst error determination program 1208 of this embodiment evaluates the ratio of burst errors by calculating the ratio α of SER to BER indicating the magnitude of SER relative to BER as an index. Specifically, the evaluation is performed using the evaluation value table 1210 shown in FIG.

  Note that when the BER calculated in the processing 207 does not completely match the value of the BER 1211, the burst error determination program 1208 sets the SER upper limit value and lower limit value corresponding to the calculated BER as the BER 1211 and the SER lower limit value 1212. Alternatively, it may be obtained by linear interpolation using the value of the SER upper limit value 1213.

The operator or the like may determine the values of the SER upper limit value 1213 and the SER lower limit value 1212 in the evaluation value table 1210 according to the strictness required for burst error separation. The BER is described as p, when the number of bits per symbol is described as k, the expected value E _r of SER in the random error is calculated by Equation 1 below.
E _r = 1- (1-p) ^k (Formula 1)

For example, the operator may set the SER lower limit value to 0 and the SER upper limit value to E _r × a (for example, a = 0.9). Further, in a bit error sequence region where a burst error occurs, assuming that the BER is 0.5, the probability that an n-bit error is distributed in an m-bit range is expressed by Equation 2.
_m-2 C _n-2 0.5 ^m-2 (Formula 2)

  Furthermore, when the total number of bits is described as L, since SER = (m / k) / (L / k) = m / L and BER = n / L, the ratio α = SER / BER = m / L n.

  FIG. 10 is an explanatory diagram illustrating the cumulative frequency distribution of the ratio α in the first embodiment.

  FIG. 10 shows a cumulative distribution function (CDF) when the ratio α is n = 100. From FIG. 10, 99% or more of the whole is in the range of 1.5 ≦ α ≦ 2.6. Therefore, the operator or the like may set the SER lower limit value 1212 of the evaluation value table 1210 to BER × 1.5 and set the SER upper limit value 1213 to BER × 2.6.

  According to the first embodiment, since the burst error can be determined even with one packet by using the ratio α of SER and BER, the operation can be performed with a small number of samples and the required processing amount is small. A burst error can be determined.

  According to the present embodiment, since the index is generated based on the symbol error rate that is qualitatively different between the random error and the burst error, the communication apparatus 103 determines whether the burst error does not depend on the number of received signals as samples. The percentage can be determined. In addition, since the processing for each received signal is only the calculation of the bit error rate, the symbol error rate, and their ratio α, the processing amount can be reduced compared to the case where a plurality of statistical processing is performed for each bit. This provides a burst error determination method that can operate with a small number of samples and has a low throughput.

  The configuration of the remote monitoring system and the configuration of the communication devices 102 and 103 in the second embodiment are the same as the configuration of the remote monitoring system of the first embodiment shown in FIGS. 1, 2, and 3, and the configuration of the communication devices 102 and 103. Is the same.

  However, the communication apparatus 103 according to the second embodiment determines the burst error rate by using the intermediate information obtained when the signal received from the communication apparatus 102 is convolutionally decoded.

  Viterbi decoding, which is a general convolutional decoding process, is a method of calculating a weight called a Branch Metric value according to a difference between an input expected for each information bit and an actual input value. Viterbi decoding is a method of calculating the total of Branch Metric values of all information bits included in a received signal as a Path Metric value, and outputting a decoding path having the smallest Path Metric value as a decoding result.

  The branch metric value increases as the difference between the expected input and the actual input increases, and is used as an index indicating the bit error amount of the input. Thus, in the second embodiment, the bit error rate of the input sequence is evaluated using the Path Metric value of the output path (corresponding to the BER in the first embodiment), and a plurality of (k) consecutive information bits (first embodiment). The local bit error rate, that is, the burst error occurrence state is evaluated using the maximum value of the Branch Metric values (corresponding to the SER in the first embodiment) (corresponding to the symbols in FIG. 1).

  Note that the Branch Metric value is not necessarily an integer. For example, in Soft Decision Viterbi decoding (SOVA), a Soft Decision value may be used as the Branch Metric value.

  FIG. 11 is a flowchart illustrating processing of the communication apparatus 103 according to the second embodiment.

  Processing 201 to processing 203, processing 205, processing 206, processing 210, and processing 212 to processing 217 illustrated in FIG. 11 are the same as the processing illustrated in FIG. Differences from the processing shown in FIG. 4 will be described below.

  After the process 203, the determination index recording program 1207 according to the second embodiment calculates the Path Metric value E1 of the Viterbi decoding output path for each received packet, and records it in the data buffer 1202 (901). Then, the determination index recording program 1207 calculates and records the maximum value E2 of the sum of Branch Metric values in information bits of a predetermined number of consecutive bits (k bits: k <L ′) included in the received packet. (902). Here, L ′ indicates the number of information bits included in the received information packet, and is calculated as L ′ = L / r where the coding rate is 1 / r.

（i＝０，１，…Ｌ’―ｋ） Here, the determination index recording program 1207 extracts a predetermined number of information bits from the received packet, for example, while shifting the information bit by bit. Therefore, when the Branch Metric value of i-th information bit is described as _{B i,} determining index recording program 1207, in the process 902 the results of Equation 3 is calculated as a maximum value E2, and records.

(I = 0, 1, ... L'-k)

  After the process 206, the burst error determination program 1208 uses the Path Metric value E1 and the maximum value E2 of each received packet to determine the number of packets whose Path Metric value E1 is equal to or greater than a predetermined threshold with respect to the total number of received packets. Calculate the percentage. Also, the burst error determination program 1208 calculates a burst error rate by processing 904, 212 and 214.

  Specifically, the burst error determination program 1208 uses the counters c1 and c2 in the same manner as in the first embodiment, and the Path Metric value E1 is greater than or equal to a predetermined threshold value for each of the recorded N received packets. It is determined whether or not there is (903). Here, the threshold value to be compared with the Path Metric value E1 is stored in the parameter management table 1209 in advance.

  If the Path Metric value E1 is equal to or greater than a predetermined threshold, the burst error determination program 1208 determines that the BER is equal to or greater than the predetermined threshold, and counts up the counter c1 (210). When the burst error determination program 1208 determines that the BER falls below a predetermined threshold, the burst error determination program 1208 maintains the counter c1.

  The burst error determination program 1208 determines whether the maximum value E2 is equal to or greater than a predetermined threshold (904). Here, the threshold value to be compared with the maximum value E2 is stored in the parameter management table 1209 in advance.

  If the maximum value E2 is equal to or greater than the predetermined threshold, the burst error determination program 1208 counts up the counter c2 (212). When the burst error determination program 1208 determines that the maximum value E2 is below a predetermined threshold, the burst error determination program 1208 maintains the counter c2.

  According to the second embodiment, it is possible to calculate an index corresponding to BER and SER even if the predicted value of a signal to be transmitted is not held in advance, and to detect that a burst error has occurred. . For this reason, the process which sets or predicts a predicted value can be reduced rather than Example 1. FIG.

  In addition, since the burst error determination program 1208 performs burst error determination processing using the entire transmitted packet, determination can be made with the same degree of accuracy even if the number of samples is smaller than in the first embodiment.

  The third embodiment is a modification of the first embodiment, and the communication device 103 only determines whether a burst error has occurred. In the third embodiment, when it is determined that the ratio of packets whose BER is equal to or higher than a predetermined threshold is equal to or higher than the predetermined threshold, the burst error determination program 1208 determines whether a random error or a burst error is dominant. Is sent to the outside via the input / output I / F 1113.

  The operator or the like of the third embodiment refers to the notification and executes processing such as a decrease in the coding rate and an increase in packet retransmission in the communication device 102 and the communication device 103. According to the third embodiment, since it is not necessary to add a function for applying the processing of the first embodiment to the communication apparatus 102, the amount of change to the existing remote monitoring system is smaller than that of the first embodiment.

  The configuration of the remote monitoring system and the configuration of the communication devices 102 and 103 in the third embodiment are the same as the configuration of the remote monitoring system of the first embodiment and the configurations of the communication devices 102 and 103 shown in FIGS. Is the same.

  FIG. 12 is a flowchart illustrating processing of the communication apparatus 103 according to the third embodiment.

  Processing 201 to processing 214 in the third embodiment is the same as processing 201 to processing 214 in the first embodiment. However, the burst error determination program 1208 according to the third embodiment does not execute the processes 215 to 217, but instead executes the processes 1001 and 1002.

  The burst error determination program 1208 determines that the random error is dominant when the counter c2 normalized in the process 214 is less than the threshold acquired from the parameter 303, and notifies the occurrence of the random error. Is output to the output device via the input / output interface 1113 (1001).

  If the burst error determination program 1208 determines that the counter c2 normalized in the process 214 is equal to or greater than the threshold value acquired from the parameter 303, the burst error determination program 1208 determines that the burst error is dominant and notifies the occurrence of the burst error. Information to be output to the output device via the input / output interface 1113 (1002).

  After processing 204, processing 1001, and processing 1002, the burst error determination program 1208 returns to processing 202.

  The burst error determination program 1208 may output information for notifying the occurrence of a random error or a burst error, for example, by turning on an LED installed in the communication device 103. According to the third embodiment, an operator or the like can quickly detect the occurrence of a random error or a burst error.

  Note that the functions implemented in the devices shown in the above-described embodiments are merely examples. If the communication device 102, the communication device 103, the sensor device 101, and the center device 104 can realize equivalent functions as a whole, this function is implemented. The example remote monitoring system may have any configuration. Specifically, the functions of a plurality of apparatuses shown in the above-described embodiments may be implemented in one apparatus, and the functions of one apparatus may be implemented by a plurality of apparatuses.

  In the above-described embodiment, the bit is described as the minimum unit. However, for example, the presence / absence of a packet error may be determined based on CRC (Cyclic Redundancy Code), and the packet may be set as the minimum unit. Thereby, the burst error determination program 1208 can detect a burst error with a large time scale.

  The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. In addition, it is possible to add, delete, or replace another configuration for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by the processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function can be placed in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card or an SD card.

  Further, the control lines or information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. In practice, it may be considered that almost all the components are connected to each other.

  The present invention is applicable to a system for performing digital communication, particularly wireless communication, and a communication apparatus using digital communication.

DESCRIPTION OF SYMBOLS 101 Sensor apparatus 102, 103 Communication apparatus 104 Center apparatus 1101 Antenna 1102 Wireless transmission / reception part 1103 Control part 1104 Baseband demodulation part 1105 Decoding part 1106 Network interface part 1107 Encoding part 1108 Baseband modulation part 1201 Processor 1202 Data buffer 1203 Memory 1204 Inside Bus 1205 Storage device 1206 Communication control program 1207 Determination index recording program 1208 Burst error determination program 1209 Parameter management table

Claims (12)

An error detection method in a communication device for transmitting and receiving signals,
A first procedure by which the communication device calculates an index indicating an error amount that occurs in a plurality of information units having a predetermined amount greater than 1 bit included in a received signal;
A second procedure by which the communication device determines whether or not a burst error is likely to occur in the received signal using the indicator;
The communication device receives a plurality of data blocks; and
The first procedure includes:
The communication device calculates a bit error rate of one received data block for each received data block;
The communication device extracts a plurality of symbols as the plurality of information units from the received one data block, and calculates a symbol error rate as the indicator for each received data block;
The communication device calculating a ratio between the bit error rate and the symbol error rate for each received data block; and
The second procedure is:
A procedure for determining, for each received data block based on the ratio, whether or not the communication device has an error locally;
When the ratio of the number of data blocks in which the communication apparatus determines that an error has occurred locally is equal to or greater than a first threshold, there is a possibility that a burst error has occurred in the plurality of received data blocks. error detecting method, wherein the procedure for determining high, the-containing Mukoto.   The error detection method according to claim 1,
  The first procedure includes a procedure in which the communication apparatus calculates a result obtained by dividing the symbol error rate by the bit error rate as the ratio,
  The second procedure includes a procedure in which the communication apparatus determines that an error has occurred locally when the ratio is equal to or greater than a second threshold value.   The error detection method according to claim 1,
  The first procedure includes:
  The communication apparatus calculates, as the bit error rate, the ratio of the bit amount of errors included in the received one data block to the bit amount of the received one data block for each received data block. Procedure and
  A procedure for the communication device to extract the plurality of symbols as the plurality of information units by dividing the received one data block into a plurality by the predetermined amount;
  A step of calculating a ratio of the number of symbols in which the error occurs with respect to the total number of symbols as the symbol error rate for each received data block. Method.   The error detection method according to claim 1,
  The communication device holds information for specifying a predetermined area included in the received data block,
  In the first procedure, the communication apparatus obtains the amount of error by comparing the value of the predetermined area of the received one data block with the predicted value of the predetermined area. An error detection method comprising:   An error detection method in a communication device for transmitting and receiving signals,
  A first procedure by which the communication device calculates an index indicating an error amount that occurs in a plurality of information units having a predetermined amount greater than 1 bit included in a received signal;
  A second procedure for determining whether or not a burst error is likely to occur in the received signal using the indicator; and the first procedure includes:
  A procedure for the communication device to receive a plurality of data blocks;
  The communication device outputs a decoded data block by performing convolutional decoding on the received one data block;
  The communication device calculates, as the index, a plurality of branch metric values in the plurality of information units included in the received one data block based on a difference between the decoded data block and the received data block. Including steps,
  The second procedure is:
  The communication device selects the highest value for each of the data blocks from among the determined plurality of branch metric values;
  When the ratio of the number of data blocks in which the selected maximum value is greater than or equal to a third threshold to the plurality of received data blocks is greater than or equal to a fourth threshold, the communication device receives the plurality of received data And a procedure for determining that there is a high probability that a burst error has occurred in the block.   The error detection method according to claim 5,
  The error detection method according to claim 1, wherein the received one data block is one packet.   A sensor device that collects information, a first communication device that receives the information from the sensor device, a second communication device that transmits and receives signals to and from the first communication device, and a signal from the second communication device A communication system comprising a center device for receiving
  The second communication device is
  The possibility that a burst error has occurred in the received signal is calculated using an index indicating the amount of error that occurs in a plurality of information units of a predetermined amount greater than 1 bit included in the received signal. A processor that generates an instruction to reduce the burst error when there is a high possibility that a burst error has occurred in the received signal as a result of the determination;
  A transmission / reception unit for transmitting the generated instruction to the first communication device;
  The first communication device is:
  A transmission / reception unit for receiving an instruction generated by the second communication device;
  A processor for controlling transmission of the signal based on an instruction received from the second communication device;
  The transceiver unit of the second communication device receives a plurality of data blocks,
  The processor of the second communication device is:
  The bit error rate of one received data block is calculated for each received data block,
  A plurality of symbols are extracted as the plurality of information units from the received one data block, and a symbol error rate is calculated as the index for each received data block,
  A ratio between the bit error rate and the symbol error rate is calculated for each received data block;
  Determining whether an error has occurred locally for each received data block based on the ratio;
  When the ratio of the number of data blocks determined to have an error locally is equal to or greater than a first threshold, it is determined that there is a high possibility that a burst error has occurred in the plurality of received data blocks A communication system characterized by the above.   A communication system according to claim 7,
  The processor of the second communication device is:
  The result of dividing the symbol error rate by the bit error rate is calculated as the ratio,
  When the ratio is equal to or greater than a second threshold, it is determined that an error has occurred locally.   A communication system according to claim 7,
  The processor of the second communication device is:
  The ratio of the bit amount of errors included in the one data block to the bit amount of the received one data block is calculated as the bit error rate for each received data block,
  Extracting the plurality of symbols as the plurality of information units by dividing the received one data block into a plurality by the predetermined amount;
  A communication system, wherein a ratio of the number of symbols in which the error occurs to the total number of symbols is calculated for each received data block as the symbol error rate.   A communication system according to claim 7,
  The second communication device has a storage unit that holds information for specifying a predetermined area included in the received data block;
  The processor of the second communication device obtains the amount of error by comparing a value of the predetermined area of the received one data block with a predicted value of the predetermined area. Communication system.   A sensor device that collects information, a first communication device that receives the information from the sensor device, a second communication device that transmits and receives signals to and from the first communication device, and a signal from the second communication device A communication system comprising a center device for receiving
  The second communication device is
  The possibility that a burst error has occurred in the received signal is calculated using an index indicating the amount of error that occurs in a plurality of information units of a predetermined amount greater than 1 bit included in the received signal. A processor that generates an instruction to reduce the burst error when there is a high possibility that a burst error has occurred in the received signal as a result of the determination;
  A transmission / reception unit for transmitting the generated instruction to the first communication device;
  The first communication device is:
  A transmission / reception unit for receiving an instruction generated by the second communication device;
  A processor for controlling transmission of the signal based on an instruction received from the second communication device;
  The transceiver unit of the second communication device receives a plurality of data blocks,
  The processor of the second communication device is:
  Generate a decoded data block by performing convolutional decoding on one received data block,
  Based on the difference between the decoded data block and the received data block, a plurality of branch metric values in the plurality of information units included in the received one data block are calculated as the index,
  The highest value is selected for each data block from the plurality of branch metric values obtained,
  When the ratio of the number of data blocks having the selected maximum value equal to or greater than a third threshold to the plurality of received data blocks is equal to or greater than a fourth threshold, a burst error occurs in the plurality of received data blocks. A communication system, characterized by determining that the possibility of occurrence is high.   A communication device for transmitting and receiving signals,
  A first procedure for calculating an index indicating the amount of error that occurs in a plurality of information units of a predetermined amount greater than 1 bit included in the received signal;
  A second procedure for determining whether a burst error is likely to have occurred in the received signal using the indicator;
  Receiving a plurality of data blocks; and
  In the first procedure,
  A procedure for calculating the bit error rate of one received data block for each received data block;
  Extracting a plurality of symbols as the plurality of information units from the received one data block, and calculating a symbol error rate as the index for each received data block;
  Performing a procedure for calculating a ratio of the bit error rate and the symbol error rate for each received data block;
  In the second procedure,
  Determining whether a local error has occurred for each received data block based on the ratio; and
  A procedure for determining that there is a high possibility that a burst error has occurred in the plurality of received data blocks when the ratio of the number of data blocks determined to have locally generated an error is equal to or greater than a first threshold. And a communication device.

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