JP2006238129A - Error correction method for reed-solomon code, method for estimating/compensating signal distortion and communications system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform error corrections for continuous noises to the extent of a few milliseconds through an interleaver, without destroying block sequences in Reed-Solomon codes, in an error correction method for Reed-Solomon codes in digital transmission of the limited band. <P>SOLUTION: A transmission apparatus 10 has a Reed-Solomon encoder 12, which performs Reed-Solomon encoding for a transmission data sequence 11 in units of frames, and an interleaver 16, which divides each frame of Reed-Solomon encoded data into a plurality of subframes and interleaves, without destroying code sequences of the subframes. The interleaver 16 has a data table divided into n×m blocks, based on the frame number n for the Reed-Solomon encoded data, and the number m for subframes that each of the frames is divided. For the blocks of the data table, the interleaver 16 writes/reads the plurality of subframes, to correct errors with respect to continuous noise that occurs in the transmission route of the limited transmission band. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an error correction method for Reed-Solomon codes, a signal distortion estimation / compensation method, and a communication system, and more particularly, particularly in a transmission line connected to a multi-terminal having a limited transmission band, etc. Reed-Solomon code interleaver system and deinterleaver system used in digital transmission systems in transmission lines where long surge noise occurs and in transmission lines where line trap devices that block high-frequency bands cannot be inserted at branch points , Pilot symbol synchronization schemes, and communication systems to which these schemes are applied.

  In general, in a power line carrier system using a power transmission line, the bit error rate characteristics of digital transmission can be maintained well even in an environment of continuous surge noise of about several ms generated by operation of a power system such as a switch. In order to achieve this, interleaver technology that makes it possible to correct burst errors generated by continuous surge noise becomes important.

  Further, the frequency characteristics of a transmission line in which a line trap cannot be installed in the transmission tower due to a problem in strength of the transmission tower at the branch point is greatly influenced by the reflected wave at the branch point, and the frequency characteristic is greatly distorted. In addition, since the change in characteristic impedance due to load fluctuations in the power system appears significantly, the reception spectrum may fluctuate uniformly. For this reason, a technique in which an adaptive equalizer is combined with pilot symbol synchronization for compensating for amplitude and phase fluctuation of a received signal becomes important.

  Hereinafter, a transmission example of a power line carrier apparatus using a transmission line system in which a line trap cannot be installed at a branch point, the presence of continuous surge noise, the presence of a delayed wave, and frequency characteristics will be described with reference to the drawings.

  FIG. 11 is a diagram showing a configuration example of a power line carrier system that is an example of an application field of the present invention, in which 100, 110, 120, and 130 are electrical stations (substations), 122 and 132 are branch locations, Indicates a transmission line. The substation 100 includes a transmission line high-frequency carrier device 101, a coupling capacitor 102, a line trap 103, a circuit breaker 104, and a transformer 105. The substation 110 includes a transmission line high-frequency carrier device 111, a coupling capacitor 112. , Line trap 113, circuit breaker 114, transformer 115, substation 120 has line trap 121, circuit breaker 123, transformer 124, and substation 130 includes line trap 131, circuit breaker 133, transformer. A container 134 is provided. This system shows a connection configuration example of a high-frequency transfer device for a transmission line in which a line trap cannot be installed at a branch point.

  In a multi-terminal connection transmission line system in which line traps cannot be installed at the branch points 122 and 132 shown in FIG. 11, the power substations 100 and 110 are allowed to pass power supply frequencies and block high-frequency signals for power line conveyance. Line traps 103 and 113 and coupling capacitors 102 and 112 for passing a high-frequency signal for power line conveyance are installed, and the transmission line high-frequency carrier devices 101 and 111 transmit power via the coupling capacitors 102 and 112, respectively. A communication line connected to the line 200 and passing through the power transmission line 200 is configured.

  Further, when power is supplied to the substations 120 and 130 from the transmission line 200, the transmission line 200 is provided with branch points 122 and 132, respectively, but the line trap for blocking the high-frequency signal for carrying the power line is branched. The line traps 121 and 131 are installed on the side of the substations 120 and 130, and the line traps 121 and 131 are regarded as the branch points 122 and 132, respectively.

  In such a transmission line system, when an operation operation of the power system such as a circuit breaker switching operation is performed at the substations 100, 110, 120, and 130, a continuous surge noise 200a of about 1 ms as shown in FIG. It may be received by the devices 101 and 111. Due to the influence of the continuous surge noise 200a, it becomes clear that the error correction function used in the digital transmission system exceeds the correctable number of bits, and as a result, a large number of bit errors occur and the error rate characteristics deteriorate significantly. Some sort of solution is required.

When digital data communication is performed on a wired transmission line such as the transmission line 200, the power line carrier apparatuses 101 and 111 have a Reed-Solomon code suitable for error correction of burst noise, etc., against continuous noise such as surge noise. The outer code error correction method is used. As an example, as shown in FIG. 13, the frame format of the Reed-Solomon code that can be corrected for 64 bits of continuous error is a total of 256 bytes including a synchronization code part 1 byte, a data part 239 bytes, and an FEC code part 16 bytes. Error correction for burst noise is performed using a Reed-Solomon code (RS255, 239) based on a primitive polynomial that defines GF (2 ⁸ ) in which one frame is configured.

  Further, an interleaver method called a crossing method is generally used as an error correction method for burst noise. For this, for example, a conventional interleaver method using a Reed-Solomon code described in Patent Document 1 will be described.

  FIG. 14 is a block diagram showing a configuration example of a communication system to which a conventional interleaver system using a Reed-Solomon code is applied. In the figure, 1 is a transmission path, 10 is a transmission device, and 20 is a reception device. A transmission apparatus 10 and a reception apparatus 20 that constitute a communication system are connected via a transmission line 1. The transmission device 10 includes a Reed-Solomon encoder unit 12, an interleaver unit 13, a convolutional encoder unit 14, and a modulation circuit unit 15. The reception device 20 includes a demodulation circuit unit 21, a Viterbi decoder unit 22, and a deinterleaver unit. 23, a Reed-Solomon decoder 24 is provided.

  As shown in FIG. 14, the digital input signal 11 on the transmission side (transmitting apparatus 10) is encoded by the Reed-Solomon encoder 12, and the output signal is interleaved by the interleaver unit 13, so that the convolutional encoder unit 14 is obtained. Is input. At this time, the convolutional encoder unit 14 adds redundant bits for random error correction to the interleaved signal, and the output signal is input to the modulation circuit unit 15 and transmitted to the transmission line 1. On the receiving side (receiving device 20), the signal received from the transmission path 1 is demodulated by the demodulation circuit unit 21, error correction is performed on the random error by the Viterbi decoder unit 22 and the like, and the deinterleaver unit 23 performs correction. After deinterleaving, the signal is decoded by the Reed-Solomon decoder unit 24 and a digital signal 25 is output.

  Subsequently, in a multi-terminal transmission line transmission line in which a line trap cannot be installed at the branch point, impedance mismatch at the branch points 122 and 132 shown in FIG. As described above, the level difference between the direct wave 201a and the delayed wave 201b becomes small, and as a result, the frequency characteristic becomes a characteristic distorted more greatly than the transmission path in which the line trap is installed as shown in FIG. In addition, there is a fluctuation characteristic similar to fading in which the reception spectrum fluctuates uniformly due to an impedance change accompanying the electric station side load fluctuation. When digital data communication is performed with high quality on such a transmission path, the receiver receives the amplitude of the received signal in order to strongly compensate for fluctuations such as intersymbol interference caused by overlapping of the received signal waveform. And a pilot symbol synchronization signal system that compensates for phase fluctuation is required.

FIG. 17 is a block diagram showing a configuration example of a transmission apparatus using a conventional pilot symbol insertion method, in which 30 indicates the transmission apparatus. This example shows a configuration of a transmission apparatus of a system incorporating an adaptive equalizer and distortion estimation / compensation using pilot symbols described in Patent Document 2 and the like. In the transmission device 30, a pilot symbol 31 necessary for estimating and compensating the distortion of the received signal is transmitted from the frame signal generation unit 32 with one symbol added to the head of the data frame or the like. On the receiving apparatus side, amplitude and phase fluctuation compensation is performed with reference to the pilot symbol, and a frame configuration is obtained in which the pilot symbol is added to the information symbol sequence as shown in FIG.
JP-A-2-195732 JP 2002-111756 A

  However, in the frame structure of the Reed-Solomon code described above, for example, when the transmission rate is transmitted at 192 kbps, the transmission rate of 1 bit is 1/192 000≈5.2 μs, so that 64 × 5.2≈333 μs at 64 bits. Thus, it can be seen that the continuous noise of about 1 ms exceeds the number of error correctable bits and cannot be corrected. For this reason, to increase the number of bits that can be corrected, it is possible to increase the number of bytes in the FEC code part. However, since the data frame part is reduced by that amount, there is a problem that the effective transmission rate is lowered. To do.

  As for the interleaver method using Reed-Solomon codes, the Reed-Solomon-coded input signal is written in the column direction indicated by the arrow to the N-row × M-column interleaver table as shown in FIG. In the later reading method, reading is performed in the direction indicated by the arrow as shown in FIG. For this reason, the continuity of the Reed-Solomon code sequence in byte units is lost, and the bit sequence is converted from a block signal to a random signal, and is always included in the convolutional encoder unit 14 shown in FIG. 14 as a correction function for random errors. An encoder must be added. This is because of the characteristics of Reed-Solomon error correction, because even 1-bit errors are handled in 1-byte block units, all 8 bits become errors, and even the error of several bits may exceed the error correction capability. This is because it is necessary to adapt to random errors in 1-bit units.

  For this reason, when a convolutional encoder is inserted, if the coding rate is ½ as an example, a 1-bit redundant bit is added to the input signal and the signal is output to the modulator. The transmission speed is ½, and the amount of information that can be transmitted is limited or reduced in a transmission path with a limited transmission band, which may make it difficult to apply.

  In addition, in order to perform the interleaver and deinterleaver, it is necessary to specify the start positions of the interleaver table and the deinterleaver table. For this reason, a unique word (UW) or the like is added to the head of the transmission interleaver data sequence on the transmission side, and the UW or the like is recognized as the start position of the deinterleaver table on the reception side. The effective transmission efficiency decreases depending on the ratio of the additional bits to the data series.

  Further, with regard to the pilot symbol synchronization signal system, known pilot symbols are transmitted periodically or at specific intervals, and the reception side performs distortion estimation / compensation based on the known signals. In this case, as described above, since the data is added as pilot symbol data of several symbols at the beginning of the data frame sequence on the transmitting side, there is a problem that the effective transmission rate decreases at the rate of the number of inserted symbols, and the transmission band is limited. However, this may limit or reduce the amount of information that can be transmitted, and may be difficult to apply.

The present invention has been made in view of the above-described circumstances, and in a Reed-Solomon code error correction method in digital transmission with a limited transmission band, the Reed-Solomon code block sequence is not corrupted. By using the synchronization code, the convolutional encoder required for the interleaver method is unnecessary, and without adding redundant bits such as UW for specifying the start position of the data table, it can be applied to continuous noise of about several ms. Error correction is possible,
Also, in the Reed-Solomon code signal distortion estimation / compensation method, by using the Reed-Solomon code synchronization code, it is possible to estimate received signal distortion without adding pilot symbol data required for the pilot symbol synchronization method. The purpose of the present invention is to enable the compensation and to reduce the number of bit errors of digital data to be transmitted and received without lowering the transmission efficiency by using these two methods.

In order to achieve the above-described object, the Reed-Solomon code error correction method, the signal distortion estimation / compensation method, and the communication system to which these methods are applied according to the present invention are any of the following inventions: It is configured.
A first invention is a Reed-Solomon code that performs Reed-Solomon encoding of transmission data in units of frames in an error correction system for Reed-Solomon code for correcting errors with respect to continuous noise generated in a transmission path with a limited transmission band. And interleaver / deinterleaver means that divides each frame of the Reed-Solomon encoded data into a plurality of subframes and performs interleaver / deinterleaver without breaking the code sequence of the divided subframes. It is characterized in that an error correction can be made for the continuous noise.

  In a second aspect based on the first aspect, the interleaver / deinterleaver means sets the number of frames of the Reed-Solomon encoded data (n) and the number of subframes (m) obtained by dividing each frame. And a data table divided into blocks of the number of frames (n) × the number of subframes (m), and the plurality of subframes can be written to and read from the blocks of the data table. It is what.

  In a third aspect based on the second aspect, the data table is designated with a block position in which the plurality of subframes are written such that at least one of the plurality of subframes is included in each row of the data table, The interleaver means, when writing the plurality of subframes to the data table, sequentially writes in units of 1 byte in the column direction of the data table for each block corresponding to the plurality of subframes. It is a thing.

  In a fourth aspect based on the second or third aspect, the interleaver means sequentially reads from the most significant bit of the data table in the column direction when reading the plurality of subframes from the data table. It is characterized by that.

  In a fifth aspect based on the second aspect, when the deinterleaver means writes the plurality of interleaved subframes to the data table, from the most significant bit of the data table toward the column direction. When sequentially writing and reading the plurality of subframes from the data table, the blocks are sequentially read in units of 1 byte in the column direction of the data table for each block of the plurality of subframes. It is.

  In a sixth aspect based on the third aspect, the interleaver means divides each frame so that a synchronization code of each frame is included in a head subframe of each frame, and the data table includes: The block position in which the subframe is written is specified so that the first subframe of each frame appears periodically.

  In a sixth aspect based on the sixth aspect, the deinterleaver means recognizes the periodic pattern of the synchronization code included in the first subframe of each transmitted frame, and uses the periodic pattern of the synchronization code as the periodic pattern. Based on this, the start position of the data table is recognized.

  An eighth aspect of the present invention is a Reed-Solomon code signal distortion estimation / compensation method for estimating / compensating for signal distortion in a transmission line with a limited transmission band, and which uses Reed-Solomon coding for transmitting data in units of frames. Dividing means, interleaver means for dividing each frame of the Reed-Solomon encoded data into a plurality of subframes, and performing interleaving without breaking the code sequence of the divided subframes, and the interleaved frames Signal distortion estimation / compensation means for estimating / compensating signal distortion based on a synchronization code included in the interleaver, wherein the interleaver means determines the number of frames (n) of the Reed-Solomon encoded data and each of the frames. Based on the number of divided subframes (m), the number of frames (n) × number of subframes (m) The data table is divided into patterns such that the synchronization code of each frame appears periodically according to the data table, and the signal distortion estimation / compensation means performs the synchronization when performing multilevel modulation. A code is used as a known symbol point.

  In a ninth aspect based on the eighth aspect, the signal distortion estimation / compensation means is configured so that the known symbol point is positioned so that the maximum amplitude and the maximum phase change of the signal point arrangement of the multilevel modulation are located. A code signal pattern is used.

  In a tenth aspect based on the eighth or ninth aspect, the data table has a number of frames (n) × sub-number so that the number of columns and the total number are divisors of 4 bits, 6 bits, and 8 bits. The synchronization code is divided into the number of blocks of the number of frames (m), and the synchronization code is stored in the data table so that any of 4 bits, 6 bits, and 8 bits of the synchronization code is used for a known symbol point in multi-level modulation. It is characterized by being arranged above.

  An eleventh invention is the Reed-Solomon code error correction method according to any one of the first to seventh inventions, and the Reed-Solomon code signal distortion estimation / compensation method according to any one of claims 8 to 10. It is a communication system provided with.

  The present invention is not limited to the digital data power line carrier system for power transmission lines, but can be similarly applied to a multi-point digital data transmission system in a multi-terminal system using metal cables.

  According to the Reed-Solomon code error correction method of the present invention, since the Reed-Solomon code synchronization code is used without destroying the Reed-Solomon code block sequence, the interleaver is used in a narrowband transmission line with a limited transmission band. In addition to eliminating the need for a convolutional encoder required for the system, it is possible to correct errors with respect to continuous noise of about several ms without adding redundant bits such as UW for specifying the start position of the data table.

  Further, according to the signal distortion estimation / compensation system of the present invention, the pilot symbol synchronization system required for the pilot symbol synchronization system is used by using the Reed-Solomon code synchronization code in a narrowband transmission line with a limited transmission band. Without adding data, the phase and amplitude of the received signal can be estimated and compensated. By using these two methods, the number of bit errors in digital data to be transmitted / received can be greatly reduced without lowering the transmission efficiency.

  That is, by using the data table of the present invention in the interleaver method and the pilot symbol synchronization method required when performing digital data transmission in a frequency band with a limited transmission band using a multi-terminal power transmission line or the like, Since interleaving can be performed without destroying the block signal form of the Reed-Solomon code sequence, error correction can be performed even for continuous noise of about several ms.

  In addition, by utilizing the Reed-Solomon code, it is not necessary to add redundant bits that are required when using the interleaver method, so bit errors in digital data to be transmitted and received without reducing transmission efficiency The number can be greatly reduced.

  The Reed-Solomon code error correction method according to the present invention is a transmission line digital data power line carrier system or a multi-terminal multipoint digital data transmission system using a metal cable as shown in FIG. It is effectively applied in an environment where continuous surge noise occurs due to the above, or in an environment where a line trap cannot be installed at a transmission line branch point. In particular, it can be suitably used for a system operating in a frequency band of 200 kHz or less adjacent to a spectrum such as switch surge noise or lightning surge noise.

  In the Reed-Solomon code error correction method applied to a digital data transmission line in an environment where continuous surge noise of about several ms is superimposed, the present invention performs convolution in order to perform interleaving while maintaining the Reed-Solomon code block signal format. By inserting Reed-Solomon encoded data in the data table so that the encoder is not required and the Reed-Solomon code synchronization code appears in a specific pattern, an additional bit indicating the head position of the data table such as UW is inserted. Is not required, and error correction can be performed without reducing transmission efficiency.

  Further, the present invention is a signal distortion estimation / compensation method applied to a digital data transmission line in an environment where a line trap cannot be installed at a transmission line branch point, and causes the Reed-Solomon code synchronization code to appear in a specific pattern. The pilot symbol synchronization method can be realized without adding pilot symbol data by using the synchronization code and placing it in the data table so that the multi-level modulation symbol position has the maximum amplitude and phase change. Thus, the influence on the bit error rate of digital data to be transmitted / received can be reduced.

  Hereinafter, an embodiment of an Reed-Solomon code error correction method, a signal distortion estimation / compensation method, and a communication system to which these methods are applied will be described with reference to the drawings.

  FIG. 1 is a configuration diagram for explaining an example of a Reed-Solomon code 1 frame division method and an interleaver table block division / arrangement method according to the present invention. 1A shows a configuration example of Reed-Solomon encoded data composed of a plurality of frames, FIG. 1B shows a configuration example of one frame forming Reed-Solomon encoded data, and FIG. An example of the interleaver table for arrange | positioning the sub-frame which divided | segmented each flame | frame which comprises Solomon encoding data further is shown.

  One frame of the Reed-Solomon code (RS255, 239) shown in FIG. 1B is composed of 256 bytes of a synchronization code part, a data part, and an FEC code part. This 1-frame data is divided into four in units of 64 bytes, and the 8-bit × 64-bit configuration is provided at positions 1-1, 1-2, 1-3, and 1-4 in the interleaver table shown in FIG. Write frame data. Also, the frame 2 data and the frame 3 data shown in FIG. 1A are arranged in the divided block positions of the interleaver table shown in FIG. 1C by the same division method and writing method. The interleaver size in this example is 3 frames of Reed-Solomon code, and an interleaver table of 24 horizontal rows × 256 vertical rows so that the number of columns and the total number are divisors of 4 bits, 6 bits, and 8 bits. Yes. Of course, the configuration of the interleaver table is not limited to this. The subframe of the present invention corresponds to frames 1-1, 1-2, 1-3, and 1-4 shown in FIG.

  FIG. 2 is a diagram for explaining a writing method to the interleaver table shown in FIG. As shown in FIG. 2, data obtained by dividing one frame into four is set in advance in 12 divisions for 1 frame (8 bits) × 64 rows for n frames (3 frames in this example). To n-1, n-2, n-3, n-4 (1-1, 1-2, 1-3, 1-4,..., 3-4 in this example) which are positions of the interleaver table, Writing is performed in the column direction which is the direction of the arrow for each block. In addition, the synchronization code for Reesolomon code is arranged at the first position byte of the matrix of frames 1-1, 2-1, and 3-1. At this time, the frames are arranged so that each row of the interleaver table always includes one subframe obtained by dividing each frame.

FIG. 3 is a diagram for explaining a method of reading the interleaver table in which the subframe is written in FIG. As shown in FIG. 3, in the interleaver table reading method, reading is performed in order from the first row of the interleaver table in the column direction, which is the direction of the arrow, and the result is input to the subsequent modulator (modulation circuit unit). By performing such writing and reading, the continuity of 8 bits, which is the number of units necessary for expressing the primitive polynomial defining GF (2 ⁸ ) in the Reed-Solomon code format (RS255, 239), is not lost. The synchronization code part, the frame data part, and the FEC code part are transmitted at a depth of 3 frames of interleaver.

  In the case of deinterleaving, the writing and reading processes are performed in the reverse order of the writing and reading order used in the interleaving described with reference to FIGS. That is, at the time of writing in the deinterleaver, sequentially from the first row (most significant bit) of the deinterleaver table (same as the interleaver table shown in FIG. 1C) in the column direction that is the arrow direction shown in FIG. Writing is performed, and when reading is performed, reading is performed in units of 1 byte in the column direction, which is the arrow direction illustrated in FIG.

  FIG. 4 is a diagram for explaining a configuration example of a transmission frame format after interleaving according to the present invention and a frame format in the case of deinterleaving after receiving continuous noise on the transmission path. 4A and 4B show a configuration example of a transmission frame format after interleaver, and FIG. 4C shows a configuration example of a frame format when deinterleaving after receiving continuous noise on the transmission path. Indicates.

  As shown in FIG. 4A, the transmission format after the interleaver includes the synchronization code of frame 1, the data of frame 2-3, the synchronization code of frame 3, the frames 1-1, 2-3, and 3-1. Data and the like are alternately transmitted in units of 1 byte. In the burst noise occurrence error section shown in FIG. 4B, when 9 bytes of errors occur, a specific frame is erroneously mistaken for 9 bytes in the Reed-Solomon code that is not interleaved. In the interleaver method, since the number of 9-byte errors is divided into three Reed-Solomon codes of 3 frames, as shown in FIG. It is converted into a continuous error interval of only 3 bytes.

  Therefore, since the Reed-Solomon code format (RS255, 239) can correct a continuous error of 8 bytes, the number of continuous errors that can be handled after interleaving is 8 bytes × 3 frames = 24 bytes (192 bits). It becomes. For example, if the transmission rate is 192 kbps as described above, 192 bits × 5.2 μs≈1 ms, and even for continuous surge noise up to 1 ms, error correction can be performed without using an inner encoder such as a convolutional encoder. Can be performed.

  FIG. 5 is a diagram for explaining the appearance interval and period of the Reed-Solomon code synchronization code after interleaving according to the present invention. As shown in FIG. 5A, in the Reed-Solomon code synchronization code in each frame, the synchronization code of frame 3 appears after 2 bytes of the synchronization code of frame 1, and the synchronization code of frame 2 appears after 382 bytes. . Furthermore, the synchronization code of frame 1 appears again after 384 bytes of the synchronization code of frame 2, and the synchronization code appears by repeating this specific pattern interval. Therefore, as shown in FIG. 5B, the start position of the interleaver table can be set by recognizing and detecting the appearance interval of the specific pattern.

  FIG. 6 is a flowchart for explaining an example of the procedure for setting the start position of the interleaver table according to the present invention. When data reception is started on the receiving side, first, a search for detecting an initial synchronization code is performed (step S1), and it is determined whether or not an initial synchronization code is detected (step S2). If it is detected (YES in step S2), a counter indicating the position detection of the initial synchronization code is activated (step S3). If the initial synchronization code is not detected (NO in step S2), the process returns to step S1 to repeatedly search for the initial synchronization code.

  Next, after starting the initial synchronization code position detection counter, a search is performed as to whether a synchronization code exists after 384 bytes (step S4), and it is determined whether a synchronization code exists after 384 bytes (step S5). If a synchronization code exists after 384 bytes (YES in step S5), a counter indicating the detection position of the synchronization code is started 384 bytes after the initial synchronization code (step S6). If the synchronization code does not exist after 384 bytes (NO in step S5), the counter indicating the position detection of the initial synchronization code is reset (step S18), and the search is performed again to return to step S1 and detect the initial synchronization code. To do.

  Next, after starting the counter indicating the detection position of the synchronization code after 384 bytes from the initial synchronization code, a search is performed as to whether or not the synchronization code exists after 2 bytes from the initial synchronization code (step S7). It is determined whether or not a code exists (step S8). If a synchronization code exists after 2 bytes (YES in step S8), a counter indicating the detection position of the synchronization code is started 2 bytes after the initial synchronization code (step S8). S9). If there is no synchronization code after 2 bytes from the initial synchronization code (NO in step S8), a counter indicating the position detection of the initial synchronization code and a counter indicating the detection position of the synchronization code after 384 bytes from the initial synchronization code, respectively. 384 bytes are shifted (step S13). Then, a search is again performed as to whether or not a synchronization code exists after 2 bytes from the initial synchronization code (step S14), and it is determined whether or not a synchronization code exists after 2 bytes (step S15). If it exists (YES in step S15), a counter indicating the detection position of the synchronization code is started 2 bytes after the initial synchronization code (step S9).

  In step S15, if there is no synchronization code after 2 bytes from the initial synchronization code shifted by 384 bytes (NO in step S15), the synchronization code detection counter is reset after 384 bytes (step S17), and the process passes through step S18. Then, returning to step S1, a search is performed again to detect the initial synchronization code.

  Next, after starting the counter indicating the detection position of the synchronization code 2 bytes after the initial synchronization code in the above step S9, is the counter interval indicating each of the three synchronization code detection positions coincided with the specific pattern interval described above? If it matches (YES in step S10), it is considered that the 3-frame Reed-Solomon code synchronization code is locked (step S11), and the initial synchronization code position is set to the start of the interleaver table. The position is set (step S12), and writing is started from the top of the deinterleaver table.

  In step S10, if the counter intervals indicating the three synchronization code detection positions do not coincide with the specific pattern interval described above (NO in step S10), the synchronization code detection counter after 2 bytes is reset (step S16). Through steps S17 and 18, the process returns to step S1 and a search is performed again to detect the initial synchronization code.

  As described above, since the Reed-Solomon code synchronization code is used, it is possible to specify the start position of the table without inserting additional information indicating the start position of the interleaver table such as UW.

Next, in the signal distortion estimation / compensation synchronization method (pilot symbol synchronization method) of the present invention, a case where 64-QAM of multilevel modulation is used will be described as a representative example.
FIG. It is a figure which shows the example of symbol arrangement | positioning which shows the signal space arrangement | positioning of 64QAM in 35 extended standards. As shown in FIG. 7, the 64QAM signal space arrangement, which is an extension standard of V.32, is a 64-point symbol arrangement, and information of 6 bits per symbol is transmitted.

  FIG. 8 is a diagram for explaining the appearance interval and period of known symbols in the pilot symbol synchronization system of the present invention, and the appearance symbol position of known symbols in 64QAM. As shown in FIGS. 8A and 8B, in 64QAM, one symbol is 6 bits, and the synchronization code appears at a specific interval. Therefore, by using 6 bits out of 8 bits of this synchronization code, Reed-Solomon It is possible to generate a code synchronization code as a known symbol at a specific interval.

  FIG. 9 is a diagram for explaining an example of the number of bits used and the arrangement relationship of the Reed-Solomon code synchronization code for one symbol in multilevel modulation in the interleaver table of the present invention. Since the size of the interleaver table of the present invention is set so that the number of columns and the total number are divisors of 4, 6, and 8, 6 bits from the head position of the table matrix and 6 bits from the end position. As shown in FIG. 9 (A), the 6 bits of the synchronization code are always used as symbol points in 64QAM modulation, as shown in FIG. 9A. The known symbol position is periodically measured, and it is possible to perform received signal distortion estimation and compensation by the pilot symbol synchronization method.

  Regardless of 64QAM, as shown in FIG. 9B, in the case of 256QAM, 8 bits of the synchronization code are converted into one pilot symbol, and as shown in FIG. 9C, the synchronization code is used in the case of 16QAM. Can be used as pilot symbols of two symbols.

  In addition, when the extended standard of V.32 is used for the signal section arrangement of 64QAM modulation, the synchronization code signal pattern uses [01101010], and as shown in FIG. 6 bits are used, the signal pattern is [011010], and the symbol position can be set to the phase and maximum amplitude point as shown in FIG. In the synchronization code of frame 3, 6 bits are used before the last bit, the signal pattern is [101010], and the maximum amplitude whose phase is changed by 180 ° from the previous pilot symbol as shown in FIG. 8B. A symbol point is generated. Furthermore, since the synchronization code of frame 2 is the same as the signal pattern [011010] at the time of frame 1 synchronization, a maximum amplitude symbol point whose phase has changed by 180 ° from the previous pilot symbol is generated, and this is repeated at a specific interval. A symbol is transmitted.

  As described above, since the received signal distortion is estimated and compensated using the Reed-Solomon code synchronization code, the pilot symbol synchronization method can be applied without inserting additional bits (pilot symbol data). Become.

  FIG. 10 is a block diagram illustrating a configuration example of a communication system according to an embodiment of the present invention. The transmission apparatus 10 includes a Reed-Solomon encoder unit 12, a Reed-Solomon code interleaver unit 16, and a modulation circuit unit 15. The receiving apparatus 20 includes a demodulation circuit unit 21, a decision feedback equalizer 26, a Reed-Solomon code synchronization code pilot symbol distortion estimation / compensation unit 27, a Reed-Solomon code deinterleaver unit 28, and a Reed-Solomon code. A synchronization code frame pattern detection unit 29 and a Reed-Solomon decoder unit 24 are provided. In addition, the same code | symbol is provided to the thing which has the same function as each part shown in above-mentioned FIG. 14, and the repeated description is abbreviate | omitted.

  The communication system includes a transmission device 10 and a reception device 20. The transmission device 10 encodes a transmission data sequence 11 with a Reed-Solomon encoder unit 12, and then interleaves with a Reed-Solomon code interleaver unit 16 according to the present invention. The signal is read, input to the modulation circuit unit 15 and transmitted to the transmission line 1.

  The receiving device 20 demodulates the signal received from the transmission path 1 by the demodulation circuit unit 21 and inputs the signal to the decision feedback equalizer unit 26 and the Reed-Solomon code synchronization code pilot symbol distortion estimation / compensation unit 27. . The Reed-Solomon code synchronization code pilot symbol distortion estimation / compensation unit 27 performs multi-level QAM symbol determination by estimating and compensating for transmission path distortion from a known Reed-Solomon code synchronization code pilot symbol by interpolation. . The decision feedback equalizer 26 estimates the distortion of the transmission line 1 in the training mode and the tracking mode, and updates the tap coefficient by the LMS or RLS algorithm to compensate the delay distortion for the information symbol sequence. Then, multi-level QAM symbol determination is performed. Further, in the phase correction processing of the demodulation circuit unit 21, the pilot symbol distortion estimation / compensation unit 27 of the Reed-Solomon code synchronization code weights the pilot symbol and the error amount in the tracking mode with the phase error of the estimated complex baseband signal. Average and perform phase correction using the forgetting factor.

  The signal determined by the decision feedback equalizer unit 26 is input to the Reed-Solomon code deinterleaver unit 28 and the Reed-Solomon code synchronization code frame pattern detection unit 29. The Reed-Solomon code synchronization code frame pattern detection unit 29 detects a Reed-Solomon code synchronization code appearance pattern for three frames and outputs a signal indicating the start position of the table to the Reed-Solomon code deinterleaver unit 28. In the Reed-Solomon code deinterleaver unit 28, after a signal indicating the start position is detected, writing of the data series is started from the start position of the deinterleaver table according to the procedure of the present invention.

  The Reed-Solomon code deinterleaver unit 28 reads out the data according to the procedure of the present invention after writing, outputs a Reed-Solomon code format signal, and performs the error correction in the Reed-Solomon decoder unit 24. A data series 25 is output.

  As described above in detail, according to the present invention, by using a Reed-Solomon code synchronization code and causing the synchronization code to appear at specific intervals, it is possible to specify the start position of the interleaver table and use it as a known pilot symbol. Since transmission path distortion can be estimated and compensated, transmission is possible without adding redundant bits, and these systems can be applied without reducing transmission efficiency in transmission paths with limited transmission bandwidth. It becomes possible.

It is a block diagram for demonstrating an example of the division | segmentation method of the Reed-Solomon code | symbol 1 frame in this invention, and the block division | segmentation and arrangement | positioning method of an interleaver table. It is a figure for demonstrating the writing method to the interleaver table shown in FIG.1 (C). FIG. 3 is a diagram for explaining a method of reading an interleaver table in which a subframe is written in FIG. 2. It is a figure for demonstrating the structural example of the transmission frame format after the interleaver of this invention, and the frame format at the time of deinterleaving after receiving a continuous noise in a transmission line. It is a figure for demonstrating the appearance interval and period of the synchronous code for Reed-Solomon codes after the interleaver of this invention. It is a flowchart for demonstrating an example of the setting procedure of the start position of the interleaver table by this invention. V. It is a figure which shows the example of symbol arrangement | positioning which shows the signal space arrangement | positioning of 64QAM in 35 extended standards. It is a figure for demonstrating the appearance interval and period of a known symbol in the pilot symbol synchronization system of this invention, and the appearance symbol position of the known symbol in 64QAM. It is a figure for demonstrating an example of the use bit number and arrangement | positioning relationship of the synchronous code for Reed-Solomon code | cord | chord with respect to 1 symbol at the time of the multi-valued modulation in the interleaver table of this invention. It is a block diagram which shows the structural example of the communication system which shows one Embodiment of this invention. It is a figure which shows the structural example of the power line carrier system which is an example of the application field of this invention. It is a characteristic view for demonstrating presence of the continuous surge noise at the time of switching operation. It is a figure which shows the structural example of the frame format of a Reed-Solomon code (RS255,239). It is a block diagram which shows the structural example of the communication system to which the interleaver system using the conventional Reed-Solomon code is applied. It is a characteristic view which shows the electric power characteristic of the direct wave and delay wave in the multi-terminal power transmission line in which the line trap is not installed in the branch location. It is a characteristic view which shows the frequency characteristic in the multi-terminal power transmission line in which the line trap is not installed in the branch location. It is a block diagram which shows the structural example of the transmitter using the conventional pilot symbol insertion method. It is a figure which shows the frame structure of the transmission data in the conventional pilot symbol insertion method. It is a figure for demonstrating the writing method in the conventional interleaver system. It is a figure for demonstrating the reading method in the conventional interleaver system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmission path 10, 30 ... Transmission apparatus, 11 ... Transmission data series, 12 ... Reed-Solomon encoder part, 13 ... Interleaver part, 14 ... Convolutional encoder part, 15 ... Modulation circuit part, 16 ... Reed-Solomon code Interleaver unit, 20 ... receiving device, 21 ... demodulator circuit unit, 22 ... Viterbi decoder unit, 23 ... deinterleaver unit, 24 ... Reed-Solomon decoder unit, 25 ... received data sequence, 26 ... decision feedback type, etc. 27: Reed-Solomon code synchronization code pilot symbol distortion estimation / compensation unit 28: Reed-Solomon code deinterleaver unit 29: Reed-Solomon code synchronization code frame pattern detection unit 31: Pilot symbol 32 ... frame signal generation unit, 100, 110, 120, 130 ... electric station (substation), 101, 111 ... high frequency for transmission lines Transport device, 201a ... direct wave (direct signal), 201b ... delay wave (delayed signal), 102,112 ... coupling capacitor, 103,113,121,131 ... line trap, 104,114,123,133 ... breaker 105, 115, 124, 134 ... transformer, 122, 132 ... transmission line branch point, 200 ... transmission line, 200a ... switching noise that continues for about 1 ms.

Claims (11)

  Reed-Solomon encoding means for performing Reed-Solomon encoding of transmission data in units of frames in an error correction method for Reed-Solomon encoding for correcting errors with respect to continuous noise generated in a transmission path with a limited transmission band, and the read Interleaver / deinterleaver means for dividing each frame of the Solomon encoded data into a plurality of subframes and performing interleaver / deinterleaver without breaking the code sequence of the divided subframes, An error correction method for Reed-Solomon codes, characterized in that error correction can be performed on   2. The Reed-Solomon code error correction method according to claim 1, wherein the interleaver / deinterleaver means includes the number of frames (n) of the Reed-Solomon encoded data and the number of subframes obtained by dividing each frame (m). ) And a data table divided into blocks of the number of frames (n) × the number of subframes (m), and the plurality of subframes can be written to and read from the blocks of the data table. An error correction method for Reed-Solomon codes.   3. The Reed-Solomon code error correction method according to claim 2, wherein in the data table, a block position in which the plurality of subframes are written is specified so that at least one of the plurality of subframes is included in each row of the data table. When the plurality of subframes are written to the data table, the interleaver means sequentially writes the blocks corresponding to the plurality of subframes in units of 1 byte in the column direction of the data table. An error correction method for Reed-Solomon codes.   4. The Reed-Solomon code error correction method according to claim 2, wherein the interleaver means reads the plurality of subframes from the data table from the most significant bit toward the column direction. An error correction method for Reed-Solomon codes, characterized by sequential reading.   3. The Reed-Solomon code error correction method according to claim 2, wherein the deinterleaver means performs a column direction from the most significant bit of the data table when writing the interleaved subframes to the data table. When reading the plurality of subframes from the data table, the blocks are sequentially read in units of 1 byte in the column direction of the data table when the plurality of subframes are read from the data table. An error correction method for Reed-Solomon codes.   4. The Reed-Solomon code error correction method according to claim 3, wherein the interleaver means divides each frame so that a synchronization code of each frame is included in a head subframe of each frame, and the data An error correction method for a Reed-Solomon code, wherein the table specifies a block position in which the subframe is written so that the first subframe of each frame appears periodically.   7. The Reed-Solomon code error correction method according to claim 6, wherein the deinterleaver means recognizes a periodic pattern of a synchronization code included in a head subframe of each transmitted frame, and An error correction method for a Reed-Solomon code, wherein the start position of the data table is recognized based on a periodic pattern.   In a Reed-Solomon code signal distortion estimation / compensation system for estimating / compensating for signal distortion in a transmission path with a limited transmission band, Reed-Solomon encoding means for Reed-Solomon encoding transmission data in units of frames, and the Reed-Solomon encoding means An interleaver means that divides each frame of the Solomon encoded data into a plurality of subframes and performs interleaving without breaking the code sequence of the divided subframes, and a synchronization code included in each interleaved frame Signal distortion estimation / compensation means for performing signal distortion estimation / compensation based on the number of frames (n) of the Reed-Solomon encoded data and the number of subframes obtained by dividing each frame (n). m) and divided into blocks of the number of frames (n) × the number of subframes (m). A data table, wherein the data table is patterned so that the synchronization code of each frame appears periodically, and the signal distortion estimation / compensation means converts the synchronization code into a known symbol point when performing multilevel modulation. A signal distortion estimation / compensation method for Reed-Solomon codes, characterized by being used as:   9. The signal distortion estimation / compensation method for Reed-Solomon code according to claim 8, wherein the signal distortion estimation / compensation means is configured such that the known symbol point is a maximum amplitude and a maximum phase change position of the signal point arrangement of the multilevel modulation. A signal distortion estimation / compensation method for Reed-Solomon codes, wherein the signal pattern of the synchronization code is used so that   10. The Reed-Solomon code signal distortion estimation / compensation method according to claim 8 or 9, wherein the data table has a number of frames such that the number of columns and the total number are divisors of 4 bits, 6 bits, and 8 bits. (N) × number of subframes (m) is divided into blocks, and the synchronization code is used so that any one of 4 bits, 6 bits, and 8 bits of the synchronization code is used for a known symbol point at the time of multilevel modulation. A signal distortion estimation / compensation method for Reed-Solomon codes, wherein a code is arranged on the data table.   A communication system comprising the Reed-Solomon code error correction method according to any one of Claims 1 to 7 and the Reed-Solomon code signal distortion estimation / compensation method according to any one of Claims 8 to 10.

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