Communication system, transmitting and receiving device, error correction method, and program

Abstract

While the error correction capability can be altered by changing the redundancy level, requiring different error correction circuits to achieve this increases the circuit size. [Solution] The communication system according to the disclosed technology comprises a transmitting device having an error correction code generation unit and a receiving device having an error correction unit. The error correction code generation unit selects a k-bit data signal, generates an encoded signal by adding (mk) bits of fixed-value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on the error-correction target signal, which consists of the received data signal, the (mk) bits of fixed-value signals, and the received parity signal.

Description

Technical Field

[0001] The disclosed technology relates to an error correction method in a digital coherent optical transmission system.

Background Art

[0002] In the current backbone communication network, a method of accommodating a plurality of client signals in a frame format for optical transmission has been defined by a standardization organization and is widely used (Reference 1: ITU-T G.709 / Y.1331, "Interfaces for the optical transport network"). Also, in the backbone communication network where long-distance and high-capacity communication is required, coherent optical communication technology is widely used (Reference 2: Open ROADM, "MSA 6.0 W B400G Port Digital Specification").

[0003] In coherent optical communication, in order to improve transmission characteristics, distortion and frequency / phase fluctuations that occur during transmission are compensated by digital signal processing. In order to further improve transmission characteristics, in addition to the above compensation function, an error correction function for transmitted and received data is provided to reduce data errors associated with transmission characteristics. Generally, error correction encoding is performed on data on the transmission side, and error correction is performed on the reception side according to the encoding, thereby improving transmission characteristics. As error correction methods, for example, BCH codes, Reed-Solomon codes, and convolutional codes are generally well known. In particular, in recent communication devices, due to the development of the computing power of the CPU, high-performance error correction methods such as low-density parity-check codes (LDPC) are used.

[0004] Fig. 1 shows a configuration example of a transmission device and a reception device of an optical transmission system (hereinafter, "coherent optical transmission system") using coherent optical communication technology. Multiple client signals are input to the transmitter 1. The OTN frame generation unit 101 generates an OTN frame by multiplexing client signals. The error correction code generation unit 102 adds an error correction bit (parity bit). The IQ signal generation unit 103 converts a binary signal into an IQ signal (a signal intended to represent a multi-level signal using the orthogonal phases of analog signals). The optical symbol generation unit 104 converts the IQ signal into an optical signal and transmits it to the network (optical fiber).

[0005] The receiving device 2 receives an optical signal. The IQ signal restoration unit 201 restores the IQ signal from the optical signal. The transmitted optical signal undergoes waveform distortion as it passes through the optical fiber. When restoring the IQ signal from an optical signal with a distorted waveform, errors occur. The binary signal reconstruction unit 202 reconstructs a binary signal from an IQ signal that contains errors. Naturally, the binary signal will also contain errors. The error correction unit 203 performs error correction of the binary signal using parity bits. The OTN frame processing unit 204 separates the error-corrected signal and extracts the client signal.

[0006] In information and communication systems, transmission quality deteriorates over long transmission distances due to signal attenuation and noise. In such cases, improvements can be made to the overall transmission characteristics by switching to a method with relatively good transmission characteristics (more resistant to noise), such as QPSK (Quadrature Phase Shift Keying), slowing down the baud rate (which indicates the number of modulation / demodulation cycles per second), or, in some cases, increasing the redundancy of error correction to improve error correction capability. On the other hand, when the transmission distance is short, the transmission quality is relatively good, so the modulation scheme can be changed to a higher level-of-level one such as 16QAM (Quadrature Amplitude Modulation) or 64QAM, the baud rate can be increased, or the redundancy of error correction can be reduced to improve transmission efficiency. Coherent optical transmission systems are configured to support various communication distances and transmission capacities. Figure 2 shows the symbol mapping of QPSK and 16QAM in the IQ plane. Received optical symbols, accompanied by noise and distortion, are distributed around the ideal coordinate point. In such cases, it can be seen that QPSK symbol position determination is easier (more robust to noise) compared to 16QAM.

[0007] Error correction functions are typically implemented using application-specific integrated circuits (ASICs). However, it is difficult to implement error correction methods with different levels of redundancy and algorithms within the same ASIC. Therefore, in conventional digital coherent optical transmission systems, as shown in Figure 3, multiple error correction circuits were prepared and used by switching between them according to the transmission capacity and error correction capability (Patent Document 1). Specifically, in the transmitting device 1, selectors 301 and 303 were used to switch between error correction code generation units 302-1 and 302-N. In the receiving device 2, selectors 311 and 313 were used to switch between error correction units 312-1 and 312-N. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2013-150339 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] As described above, the error correction capability can be changed by changing the redundancy of error correction. However, if different error correction circuits are prepared to change the redundancy (coding rate), the circuit scale increases. When the circuit scale increases, the power consumption of the ASIC increases.

Means for Solving the Problems

[0010] To solve the above problems, a communication system according to the disclosed technology includes a transmitting device having an error correction code generation unit that adds n-bit parity to m-bit data, and a receiving device having an error correction unit. The error correction code generation unit selects a k-bit (k < m) data signal, generates an encoding target signal by adding an (m - k)-bit fixed value signal to the data signal, and generates an n-bit parity signal from the encoding target signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on an error correction target signal composed of the received data signal, an (m - k)-bit fixed value signal, and the received parity signal.

Advantages of the Invention

[0011] According to the disclosed technology, error correction with different coding rates can be performed using the same circuit, so the circuit scale is reduced. When the circuit scale is reduced, the power consumption is also reduced in proportion to the scale. In addition, the bits with fixed values do not need to be inverted. This also reduces the power consumption of the error correction circuit.

Brief Description of the Drawings

[0012] [Figure 1] Functional block diagram showing a configuration example of a conventional digital coherent optical transmission system. [Figure 2] Diagram showing an example of symbol mapping in the IQ plane. [Figure 3]Functional block diagram showing a configuration example of a conventional digital coherent optical transmission system (with multiple error correction circuits). [Figure 4] Functional block diagram showing a configuration example of a transmission device according to the first embodiment. [Figure 5] Flowchart for explaining an example of the operation of the transmission device according to the first embodiment. [Figure 6] Diagram for explaining the operation of the transmission device according to the first embodiment using a specific example. [Figure 7] Functional block diagram showing a configuration example of a reception device according to the first embodiment. [Figure 8] Flowchart for explaining an example of the operation of the reception device according to the first embodiment. [Figure 9] Diagram for explaining the operation of the reception device according to the first embodiment using a specific example. [Figure 10] Functional block diagram showing a configuration example of a communication system according to the third embodiment. [Figure 11] Flowchart for explaining an example of the operation of the communication system according to the third embodiment. [Figure 12] Diagram for explaining an example of likelihood calculation. [Figure 13] Diagram showing a functional configuration example of a computer.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the disclosed technology will be described in detail. Components having the same function are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] [First Embodiment] In the first embodiment, error correction using soft decision is performed. First, soft decision will be described.

[0015] <Soft Decision> In error correction processing, there are hard decision which performs correction processing based on the result decoded into "1" or "0", and soft decision which performs correction processing based on the coordinates on the IQ plane of the received signal (before being decoded into "1" or "0") (Reference Document 3: Japanese Patent No. 7179934). While soft judgment error correction processing, when implemented in software, allows for adjustment of the correction amount by changing the multiplication coefficient in the correction threshold calculation, software processing at a throughput of 1 Tbps is impossible. When implementing soft judgment error correction processing in hardware, it is not possible to adjust the multiplication coefficient in the correction threshold calculation at high speed, so it is common to implement a soft judgment error correction circuit with a fixed correction threshold.

[0016] In the soft-decision error correction process, the bit sequence represented by the nearest transmitted optical symbol is reconstructed as the received binary signal based on the position of the received optical symbol in the IQ plane, and the probability that each bit of the received optical symbol is either 0 or 1 is calculated. This probability is called "likelihood" or "likelihood information." Then, errors contained in the received binary signal are corrected using the likelihood information for each bit.

[0017] A known method can be used to calculate the likelihood. An example is illustrated using Figure 12. Let's take the case where the transmitted optical symbol is QPSK as an example. "00", "01", "10", and "11" represent the transmitted optical symbols and their positions on the IQ plane. Suppose we obtain r as the coordinate of the received optical symbol. The identification region of the received signal (the region for determining the received binary signal) is the region containing the symbol "01". The likelihood L1 of the first bit of r is determined as follows: Find the distance (d4) between r and the nearest transmitted symbol ("11") whose first bit is "1" ("11" or "10"), and the distance (d2) between r and the nearest transmitted symbol ("01") whose first bit is "0" ("01" or "00"). Since the value of the first bit determined from the identification region of the received signal point is "0", L1 is calculated by subtracting the distance to "01" (the smaller the distance, the more likely "0" is) from the distance to "11" (the larger the distance, the more likely "0" is), resulting in d4-d2. The likelihood L2 of the second bit of r is determined as follows: Find the distance (d2) between r and the nearest transmitted symbol ("01") among the transmitted symbols ("11" or "01") whose second bit is "1", and find the distance (d1) between r and the nearest transmitted symbol ("00") among the transmitted symbols ("10" or "00") whose second bit is "0". Since the value of the second bit determined from the identification region of the received signal point is "1", L2 is calculated by subtracting the distance to "01" (a smaller value indicates a higher probability of "1") from the distance to "00" (a larger value indicates a higher probability of "1").

[0018] The optical transmission system according to the first embodiment will be described below, in the order of the transmitting device and the receiving device. <Transmitter> Figure 4 is a functional block diagram showing an example configuration of a transmitting device according to the first embodiment. The transmitting device 4 comprises an OTN frame generation unit 401, an error correction code generation unit 402, an IQ signal generation unit 403, an optical symbol generation unit 404, and a fixed value coupling unit 405. The error correction code generation unit 402 generates an n-bit parity signal from an m-bit data signal. Figure 5 is a flowchart illustrating an example of the operation of the transmitter 4. This will be explained using Figures 4 and 5.

[0019] The OTN frame generation unit 401 integrates the input client signals to generate an OTN frame. The fixed-value coupling unit 405 acquires a k-bit data signal from the OTN frame, which will be the processing unit (step S501). k is determined such that (mk) is an integer multiple of the number of bits represented by one optical symbol. The fixed-value coupling unit 405 combines (mk) bits of fixed-value signals with the data signal to generate an m-bit signal to be coded (step S502). The fixed-value signals can be, for example, all 0s or all 1s. The error correction code generation unit 405 generates an n-bit parity signal from the signal to be coded (step S503). The IQ signal generation unit 403 combines the data signal (k bits) and the parity signal (n bits) to form a transmission signal. The IQ signal generation unit 403 also divides the transmission signal into a predetermined size to generate an IQ signal. The optical symbol generation unit 404 converts the IQ signal into an optical symbol (step S505). The transmission device 4 outputs the optical symbol to an optical fiber.

[0020] Using FIG. 6, the operation of the transmission device will be specifically described. Let m = 111 and n = 17. Also, assume that the IQ signal generation unit generates an IQ signal corresponding to a 16QAM optical symbol (expressing 4 bits of data per symbol). <Example where k = 111> FIG. 6(a) shows the case of communicating with the maximum coding rate (minimum redundancy), corresponding to the case where k = m. The fixed value combining unit 405 acquires an 111-bit data signal from the OTN frame. When k = m, the number of bits of the fixed value signal is 0, and the combination of the fixed value signals is not performed. The signal to be coded is 111 bits. The error correction code generation unit 405 generates a 17-bit parity signal from the signal to be coded. The IQ signal generation unit 403 combines the data signal (111 bits) and the parity signal (17 bits) to form a transmission signal. The IQ signal generation unit 403 also divides the transmission signal into 32 (in 4-bit units) to generate an IQ signal.

[0021] <Example where k = 95> FIG. 6(b) shows the case of communicating with a reduced coding rate. The fixed value combining unit 405 acquires a k = 95-bit data signal from the OTN frame. The fixed value combining unit 405 combines a (m - k) = 16-bit fixed value signal with the data signal to generate an 111-bit signal to be coded. The error correction code generation unit 405 generates a 17-bit parity signal from the signal to be coded. The IQ signal generation unit 403 combines the data signal (95 bits) and the parity signal (17 bits) to form a 112-bit transmission signal. The IQ signal generation unit 403 also divides the transmission signal into 28 units (4 bits each) to generate the IQ signal.

[0022] The above is a description of the transmitting device.

[0023] <Receiving device> Next, I will explain the operation of the receiving device. Figure 7 is a functional block diagram showing an example configuration of a receiving device according to the first embodiment. The receiving device 7 includes an IQ signal restoration unit 701, a binary signal restoration unit 702, an error correction unit 703, an OTN frame processing unit 704, a likelihood calculation unit 705, an expected value coupling unit 706, and a data signal extraction unit 707. The receiving device 7 receives the optical symbols transmitted by the transmitting device 4. The error correction unit 703 performs soft judgment error correction processing. Figure 8 is a flowchart illustrating an example of the operation of the receiving device 7. The following explanation will use Figures 7 and 8.

[0024] The IQ signal restoration unit 701 receives an optical symbol (step S801) and obtains coordinates on the IQ plane (received optical symbol coordinates) (step S802). The binary signal reconstruction unit 702 reconstructs the binary signal from the received optical symbol coordinates (step S803). In parallel, the likelihood calculation unit 705 calculates the likelihood of each bit of the binary signal from the received optical symbol coordinates (step S804). Steps S801 to S804 are repeated to obtain a (k+n)-bit binary signal and (k+n) likelihood values. The (k+n)-bit binary signal consists of a k-bit received data signal and an n-bit received parity signal.

[0025] The expectation value merging unit 706 combines the (mk)-bit expectation value signal with the (k+n)-bit binary signal to generate an (m+n)-bit error-correction target signal (step S805). The merging position of the expectation value signal is the same as that of the fixed-value signal in the above-mentioned code-generating target signal. The value of the expectation value signal is also the same as that of the fixed-value signal. Each bit of the expectation value signal is set to the maximum likelihood for a bit value of 0, or the maximum likelihood for a bit value of 1, depending on the value of the fixed-value signal.

[0026] The error correction unit 703 performs error correction on the signal to be corrected using the likelihood assigned to the signal to be corrected, and generates a corrected signal of (m+n) bits (step S806). For example, it selects a predetermined number of bits with low likelihood (bits that are likely to be errors) (e.g., 8 bits), generates all combinations of whether the selected bits are "0" or "1" (256 combinations in the case of 8 bits), identifies the correct combination, and verifies that errors remain in the signal to be corrected after replacing it with the identified combination. If errors remain, it selects a predetermined number of bits with low likelihood from the uncorrected bits and repeats the above process. The data signal extraction unit 707 extracts k bits corresponding to the received data signal from the corrected signal to generate a corrected data signal (step S807). The OTN frame processing unit integrates correction data signals and reconstructs the OTN frame. It also reconstructs and outputs the client signal from the OTN frame.

[0027] The operation of the receiving device will be explained in detail using Figure 9. The transmitting device is assumed to generate a parity signal of n=17 bits from a code generation target signal of m=111 bits. The received optical symbol is 16QAM. <When k=111 is set in the transmitting device> Figure 9(a) shows the case where the light symbol generated by the transmitting device is received with k=111. The IQ signal reconstruction unit 701 processes 32 16QAM optical symbols, and the binary signal reconstruction unit 702 reconstructs a binary signal consisting of a 111-bit received data signal and a 17-bit received parity signal. The likelihood calculation unit calculates the likelihood for each bit of the received data signal and the received parity signal. When k=m=111, the number of bits in the fixed value signal is 0, and no concatenation of the expected value signal is performed. The error-corrected signal is a 128-bit signal, which is the concatenation of the received data signal and the received parity signal. The error correction unit 703 performs error correction on the signal to be corrected and generates a 128-bit corrected signal. The data signal extraction unit 707 extracts 111 bits corresponding to the received data signal from the corrected signal to generate a corrected data signal.

[0028] <When k=95 is set in the transmitting device> Figure 9(b) shows the case where an optical symbol generated by the transmitting device is received with k=95. The IQ signal reconstruction unit 701 processes 28 16QAM optical symbols, and the binary signal reconstruction unit 702 reconstructs a binary signal consisting of a 95-bit received data signal and a 17-bit received parity signal. The expectation value merging unit 706 combines a (mk) = 16-bit expectation value signal with a (k+n) = 112-bit binary signal to generate a (m+n) = 128-bit error-correction target signal. The merging position of the expectation value signal is the same as that of the fixed-value signal in the above-mentioned code-generating target signal. The value of the expectation value signal is also the same as that of the fixed-value signal. The maximum likelihood is set for each bit of the expectation value signal. The error correction unit 703 performs error correction on the signal to be corrected and generates a 128-bit corrected signal. The data signal extraction unit 707 extracts 95 bits corresponding to the received data signal from the corrected signal to generate a corrected data signal.

[0029] The above is a description of the receiving device.

[0030] When k=111, the coding rate is 111 / (111+17)=0.87. When k=95, the coding rate is 95 / (95+17)=0.85, demonstrating that the coding rate could be reduced (error correction capability increased) by using a single error correction code generation unit. The minimum value of k depends on the number of bits realized by one optical symbol, but in 16QAM, by setting k=4, the coding rate can be reduced to 4 / (4+17)=0.19.

[0031] The above is a description of the first embodiment. Furthermore, any error correction coding method that clearly separates the parity signal from the data signal on which the parity signal is based is acceptable. Furthermore, although the first embodiment described above used a soft judgment error correction process, a hard judgment error correction process may be used instead. Furthermore, while the above explanation assumed that fixed-value signals were all 0 or all 1, fixed-value signals are not limited to these; any bit sequence can be set. However, if an arbitrary bit sequence is used, it is necessary to store that arbitrary bit sequence in both the transmitting and receiving devices.

[0032] [Second Embodiment] As can be seen from Figure 6, the number of bits converted to an optical signal differs between the cases of k=111 and k=95. It is 128 bits for k=111 and 112 bits for k=95. When the optical symbol generation unit 404 of the transmitting device 4 generates an optical signal at the speed when k=111, the IQ signal is insufficient at a rate of 4 out of 32 times when k=95. Therefore, in the case of k=95, the rate of optical signal generation should be slowed down. If the rate of optical symbol generation when k=111 is B [symbols / sec], then when k=95, it should be B × 112 / 128. Generalizing this, the rate of light symbol generation B when k=m is m Based on this, B k You just need to decide that.

number

[0033] The above is a description of the second embodiment.

[0034] [Third Embodiment] In the first embodiment, it was shown that a single error correction code generation unit and a single error correction unit can support different coding rates. When the communication state is stable (such as short - distance communication), it is desired to operate the transmission device and the reception device using a high coding rate state (for example, k = m), and when high - performance error correction is required for long - distance communication, the coding rate is reduced (set to k < m).

[0035] FIG. 10 is a functional block diagram showing a configuration example of a communication system according to the third embodiment. Generally, a transmission device and a reception device are mounted on one transmission apparatus, and the transmission apparatuses are connected oppositely. The first transmission apparatus 1001 communicates with the second transmission apparatus 1002 via a communication network 1003. The first transmission apparatus 1001 includes a transmission device 4 - 1, a reception device 7 - 1, and a first communication quality monitor 1004. Similarly, the second transmission apparatus 1002 includes a transmission device 4 - 2, a reception device 7 - 2, and a second communication quality monitor 1005. The transmission devices 4 - 1 and 4 - 2 have the same configuration as the transmission device 4 in the first embodiment. The reception devices 7 - 1 and 7 - 2 have the same configuration as the reception device 7 in the first embodiment. FIG. 11 is a flowchart for explaining an example of the operation of the communication system 10. This will be explained using FIGS. 10 and 11.

[0036] Assume that the first transmission apparatus 1001 and the second transmission apparatus 1002 are communicating with k = m (without using fixed - value signals and expected - value signals). Assume that the second communication quality monitor 1005 detects a deterioration in communication quality (step S1101). The deterioration can be determined, for example, by the number of bits with error correction. The second communication quality monitor 1005 changes the number of bits of the fixed - value signal of the transmission device 4 - 2 and the number of bits of the expected - value signal of the reception device 7 - 2 to k1 < m (step S1102). The value of k1 may be determined in advance according to the degree of communication quality deterioration. The second transmission apparatus 1002 notifies the first transmission apparatus 1001 of k1 (step S1103). The first communication quality monitor 1004 of the first transmission device 1001 changes the number of bits of the fixed value signal of the transmitting device 4-1 and the number of bits of the expected value signal of the receiving device 7-1 to k1 (step S1104). From this point onward, the first transmission device 1001 and the second transmission device 1002 communicate with k=k1 (performing high-performance error correction with a low coding rate).

[0037] The above is a description of the third embodiment.

[0038] [Programs, recording media] The functions realized by the components described herein may be implemented in a circuit or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to realize the functions described herein. A processor is considered to be a circuit or processing circuitry, including transistors and other circuits. A processor may be a programmed processor that executes a program stored in memory.

[0039] In this specification, circuitry, unit, and means are hardware programmed to perform or execute the functions described herein. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to perform or execute the functions described herein.

[0040] If the hardware is a processor that is considered to be a type of circuitry, then the circuitry, means, or unit is a combination of hardware and software used to constitute the hardware and / or processor.

[0041] The various processes described above can be carried out by loading a program that executes each step of the above method into the recording unit 2020 of the computer 2000 shown in Figure 13, and then causing the control unit 2010, input unit 2030, output unit 2040, display unit 2050, etc. to operate.

[0042] The program describing this process can be recorded on a computer-readable recording medium. Any computer-readable recording medium can be used, such as a magnetic recording device, optical disc, magneto-optical recording medium, or semiconductor memory.

[0043] Furthermore, this program may be distributed, for example, by selling, transferring, or lending portable recording media such as DVDs or CD-ROMs on which the program is recorded. Alternatively, the program may be stored in the storage device of a server computer and distributed by transferring the program from the server computer to other computers via a network.

[0044] A computer executing such a program may, for example, first store the program recorded on a portable storage medium or a program transferred from a server computer in its own memory. Then, when processing is to be executed, the computer reads the program stored in its memory and executes the processing according to the read program. Alternatively, the computer may directly read the program from the portable storage medium and execute the processing according to that program, or it may sequentially execute the processing according to the received program each time a program is transferred to it from a server computer. Furthermore, the processing may be executed by a so-called ASP (Application Service Provider) type service, where the processing function is realized only by execution instructions and result acquisition, without transferring the program from the server computer to this computer. Moreover, the processing may be executed using a so-called SaaS (Software as a Service) type service, where a part of the server computer is made available to the user along with the program. The above-mentioned program includes information used for processing by an electronic computer that is equivalent to a program (data that is not a direct instruction to the computer but has the property of defining the computer's processing).

[0045] Furthermore, although the above explanation assumes that the device is configured by executing a predetermined program on a computer, at least a part of these processes may be implemented in hardware. [Industrial applicability]

[0046] This invention can be used in digital coherent optical transmission systems. [Explanation of Symbols]

[0047] 4. Transmitter 401 OTN Frame Generation Unit 402 Error Correction Code Generation Unit 403 IQ Signal Generation Unit 404 Light Symbol Generation Unit 405 Fixed Value Connection Section 7. Receiving device 701 IQ Signal Restoration Unit 702 Binary Signal Restoration Unit 703 Error Correction Section 704 OTN Frame Processing Unit 705 Likelihood Calculation Unit 706 Expected Value Connection Section 707 Data signal extraction unit 10 Communication Systems 1001 First transmission device 1002 Second transmission device 1003 Communication Network 1004 First Communication Quality Monitor 1005 First Communication Quality Monitor 2000 Computer 2010 Control Unit 2020 Records Department 2030 Input Section 2040 Output Section 2050 Display section

Claims

1. A transmitting device having an error correction code generation unit that adds n bits of parity to m bits of data, A communication system comprising a receiving device having an error correction unit, The error correction code generation unit selects a k-bit (k < m) data signal, generates an encoded signal by adding a (m - k)-bit fixed value signal to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. Let Bm be the speed at which the transmitting device generates optical symbols when the fixed-value signal is not used, and let Bk be the speed at which the transmitting device generates optical symbols when the (m-k) bit fixed-value signal is used. [Math 2] A communication system that does this.

2. A transmitting device having an error correction code generation unit that adds n bits of parity to m bits of data, A communication system comprising a receiving device having an error correction unit and a communication quality evaluation unit, The error correction code generation unit selects a k-bit (k < m) data signal, generates an encoded signal by adding a (m - k)-bit fixed value signal to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. When the communication quality evaluation unit detects a deterioration in communication quality, it updates the value of k to a value k' smaller than k, and notifies the transmitting device of k'. The transmitting device performs error correction coding using k' instead of k, The receiving device performs error correction using k' instead of k. Communication system.

3. An error correction method performed by a communication system comprising a transmitting device having an error correction code generation unit that adds n bits of parity to m bits of data, and a receiving device having an error correction unit, The error correction code generation unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. Let Bm be the speed at which the transmitting device generates optical symbols when the fixed-value signal is not used, and let Bk be the speed at which the transmitting device generates optical symbols when the (m-k) bit fixed-value signal is used. [Math 3] An error correction method that is as follows.

4. An error correction method performed by a communication system comprising a transmitting device having an error correction code generation unit that adds n bits of parity to m bits of data, and a receiving device having an error correction unit and a communication quality evaluation unit, The error correction code generation unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting device transmits the data signal and the parity signal to the receiving device. The receiving device receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. When the communication quality evaluation unit detects a deterioration in communication quality, it updates the value of k to a value k' smaller than k, and notifies the transmitting device of k'. The transmitting device performs error correction coding using k' instead of k, The receiving device performs error correction using k' instead of k. Error correction methods.

5. A transmitting and receiving device that constitutes a communication system, An error correction encoding unit that adds n bits of parity to m bits of data, Light symbol generation unit, The transmitting unit, Error correction section, It comprises a receiving unit, The error correction coding unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting unit transmits the data signal and the parity signal. The receiving unit receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal from another transmitting / receiving device. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. Let Bm be the rate at which the optical symbol generation unit generates optical symbols when the fixed value signal is not used, and let Bk be the rate at which the optical symbol generation unit generates optical symbols when the (m-k) bit fixed value signal is used. [Math 4] A transmitting and receiving device.

6. A transmitting and receiving device that constitutes a communication system, An error correction encoding unit that adds n bits of parity to m bits of data, The transmitting unit, Error correction section, The receiving unit and It includes a communication quality evaluation unit, The error correction coding unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting unit transmits the data signal and the parity signal. The receiving unit receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal from another transmitting / receiving device. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. When the communication quality evaluation unit detects a deterioration in communication quality, it updates the value of k to a value k' smaller than k, and notifies the other transmitting and receiving devices of k'. The other transmitting and receiving device receives the received data signal and the received parity signal generated by error correction coding using k' instead of k. The error correction unit performs error correction using k' instead of k. Transceiver.

7. An error correction method performed by a transmitting and receiving device that constitutes a communication system, The error correction coding unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting unit transmits the data signal and the parity signal. The receiving unit receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal from another transmitting / receiving device. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. Let Bm be the rate at which the optical symbol generation unit generates optical symbols when the fixed value signal is not used, and let Bk be the rate at which the optical symbol generation unit generates optical symbols when the (m-k) bit fixed value signal is used. [Math 5] An error correction method that is as follows.

8. An error correction method performed by a transmitting and receiving device that constitutes a communication system, The error correction coding unit selects a k-bit (k < m) data signal, generates an encoded signal by adding (m - k) bits of fixed value signals to the data signal, and generates an n-bit parity signal from the encoded signal. The transmitting unit transmits the data signal and the parity signal. The receiving unit receives a k-bit received data signal corresponding to the data signal and an n-bit received parity signal corresponding to the parity signal from another transmitting / receiving device. The error correction unit performs error correction on the error correction target signal, which consists of the received data signal, the (m-k) bit fixed value signal, and the received parity signal. When the communication quality evaluation unit detects a deterioration in communication quality, it updates the value of k to a value k' smaller than k, and notifies the other transmitting and receiving devices of k'. The other transmitting and receiving device receives the received data signal and the received parity signal generated by error correction coding using k' instead of k. The error correction unit performs error correction using k' instead of k. Error correction methods.

9. A program for causing a computer to function as a transmitting and receiving device according to claim 5 or 6.

Images