JP6581946B2 - Digital information transmission system, transmission apparatus and transmission method thereof - Google Patents

Description

  The present invention relates to a digital information transmission system used in an environment where periodic interference waves are mixed into a communication line from the outside, and a transmission apparatus and transmission method used in this system.

  In a digital information transmission system using a metal wire as a communication transmission path, electromagnetic waves emitted from a medium other than the system (for example, electromagnetic waves used for other communications and broadcasting, electromagnetic waves emitted from surrounding electric / electronic devices) are generated. It is coupled on the communication transmission line and affects the electric signal transmitted through the communication transmission line as a conductive electromagnetic interference wave (electromagnetic interference). This may cause degradation of communication quality such as transmission information errors and omissions. In order to avoid this, a general digital information transmission system has an error detection and correction function for correcting an error (for example, a bit error) generated in information to be transmitted.

  In many digital information transmission systems, a data area for error correction is added to the data (user data) area generated by the transmission device on the transmission side and transmitted, and bit errors occurring during transmission on the reception side are A Forward Error Correction (FEC) method is employed that corrects using error correction data. For this reason, increasing the amount of error correction data increases the error correction capability. However, on the other hand, the ratio of the redundant data amount to the total transmission data amount increases, and the user data transmission rate decreases. That is, there is a tradeoff between the throughput of the digital information transmission system and the improvement of error correction capability by increasing the amount of error correction data.

  For example, in IEEE802.11a, which is one of the wireless LAN (Local Area Network) standards, at least a quarter of a data area of a transmission frame as a transmission unit is used as an error correction code data area (the coding rate is As a result, the throughput is suppressed to a maximum of 54 Mbps with respect to the maximum transmission rate of 72 Mbps (bit per second) considering the modulation / demodulation method.

  Non-Patent Document 1 discloses, for example, ADSL (Asymmetric Digital Subscriber Line) as a transmission frame transmission / reception technique including error correction processing in a digital information transmission system.

  That is, in a system using ADSL, when digital information transmitted from an information transmission device such as a server is input to the ADSL transmitter, the ADSL transmitter performs CRC (Cyclic Redundancy Check; CRC) on the digital information. ) Coding, Reed-Solomon Code (RS) coding, scramble processing, trellis coding, QMT (Quadrature Amplitude Modulation) and IFFT (Inverse Fast Fourier Transform) modulation, DMT (Discrete Multi-Tone) modulation CP (Cyclic Prefix) addition processing is sequentially performed, and then converted from a digital signal to an analog signal by AFE (Analog Front End) processing, and transmitted as an electrical signal to a transmission line.

  On the other hand, in an ADSL receiver, an electrical signal transmitted via a transmission path is first converted from an analog signal to a digital signal by AFE processing, and waveform equalization on the time axis is performed by TEQ (Time domain Equalizer). Subsequently, after CP deletion and DMT demodulation processing by FFT, waveform equalization processing on the frequency axis is performed by FEQ (Frequency domain Equalizer). In the QAM process included in the DMT demodulation process, Euclidean distance information from each QAM coordinate point of the received signal detected from each frequency component of the analog multi-wave is calculated and passed to the Viterbi decoder. The Viterbi decoder performs symbol determination of the received signal based on the Euclidean distance information. Thereafter, after descrambling processing and RS decoding are performed, whether or not there is an error in the information after symbol determination is checked by CRC, and if there is no error, it is sent to an information receiving apparatus such as a personal computer. On the other hand, when information that cannot be corrected by using the error correction process remains at a predetermined rate, the information is generally discarded.

  By the way, when frame data such as an Ethernet (registered trademark) frame is transmitted using the ADSL digital information transmission system as described above, the transmission signal wave and the electromagnetic interference wave are illustrated in FIG. A relationship arises.

  That is, as shown in FIG. 9A, an Ethernet frame generated by an information transmission apparatus such as a server generates an IP packet by adding an IP (Internet Protocol) header to the user data area, and A MAC (Media Access Control) header is added to the header, and an FCS (Frame Check Sequence) is added to the footer of the IP packet. Although not illustrated in FIG. 9, the user data area includes data related to protocols belonging to a higher layer than IP, such as a TCP (Transmission Control Protocol) header and an HTTP (Hyper Text Transfer Protocol) header. .

  When the Ethernet frame is input to the ADSL transmitter, the ADSL transmitter first removes the MAC header and FCS from the input frame, and divides the frame into a predetermined number of intermediate frames as shown in FIG. 9B. The The size of the intermediate frame is determined by the size of the transmission frame generated by one digital modulation and sent to the transmission path. In ADSL, the size of a transmission frame is determined by training during link establishment.

  Subsequently, an error correction data area (FEC area) is added to the data structure in which the divided intermediate frames are connected. The data size of the FEC area is determined according to the size of the transmission frame. The entire frame structure shown in FIG. 9B is divided into a predetermined data size as shown in FIG. 9C. Each divided data area is rearranged in order (that is, scrambled) by a predetermined method. Therefore, the IP header information and data area information shown in FIG. 9A and the FEC area shown in FIG. 9B are fragmented in the data structure shown in FIG. 9C. .

Next, the data shown in FIG. 9C is subdivided into the size of a transmission frame (hereinafter also referred to as an output frame) as shown in FIG. 9D. At this time, the data structure in each output frame is rearranged in units of bytes. The data (bits) of each output frame shown in FIG. 9D is allocated to a plurality of predetermined bins which are ADSL subcarriers, as shown in FIG. 9E. In FIG. 9 (e) each of four successive output frames 1-4 shown in FIG. 9 (d) have shown the manner in which are successively assigned to each bin in the frequency band f _w. f _w denotes, in the case of ADSL downstream transmission has a bandwidth from 138kHz to 2208KHz, composed of 478 bins of approximately 4kHz bandwidth per bottle.

After QAM processing is performed according to the bit structure assigned to each bin, a carrier signal wave (multiplexed analog wave) having the frequency of each bin as a carrier frequency is generated as shown in FIG. To the transmission path. The horizontal axis of FIG.9 (f) is time. The output frame transmission time interval is a modulation time interval of each output frame, and is referred to as a symbol length, and hereinafter referred to as a modulation time slot (T _s ).

FIG. 9 (g) shows a bursty interference wave that disturbs the four output frames in FIG. 9 (d) in succession and sequentially propagates through the transmission line as the signal waveforms in FIG. 9 (f). An example of a waveform is shown. Here, the time axes of FIG. 9 (f) and FIG. 9 (g) are the same, and the frequency at which the intensity of the burst interference wave exceeds the “intensity level causing signal degradation” shown by the broken line in FIG. 9 (g). When the component is included, the signal waveform component transmitted at the same carrier frequency as the frequency component is interfered, and as a result, an error occurs when the bit information assigned to the signal waveform component is read at the receiver. In the bursty interference wave shown in FIG. 9 (g), since there are frequency components exceeding the intensity level that cause signal degradation at times T ₁ , T ₃ , and T ₄ , the output frames 1, 3, and 3 in FIG. A bit error occurs in at least a part of 4.

Shigenori Yuasa, Shuichiro Asagi, “A lot of advanced technology is revealed in a small box, and the inside of the ADSL modem is revealed”, Nikkei NETWORK, pp. 194-199, 2002. 08

  As described above, in a conventional digital information transmission system such as ADSL, it is necessary to enable error correction even if a burst error due to electromagnetic interference occurs in any data area of the output frame. The necessary FEC data area is secured. In addition, as described in FIG. 9C, the IP header information, the data area information, and the FEC data are fragmented and scrambled so that the fragmented data is distributed in all frames.

However, the electromagnetic interference generated in the actual environment does not always have an intensity level that causes signal degradation, and as shown in FIG. In most cases, bursty interference waves included in the part occur irregularly. Therefore, as can be seen from the comparison between FIG. 9C and FIG. 9G, FIG. 9D is transmitted at times T ₁ , T ₃ , and T ₄ where electromagnetic waves having intensity levels that cause signal degradation exist. ) Output frames 1, 3, and 4 require error correction (that is, FEC is included in the data area). On the other hand, FIG. 9 output frame 2 (d) to weak electromagnetic waves having no intensity levels resulting signal degradation is sent to the time T ₂ that is present is not possible to generate information error, it does not require error correction (That is, it is not necessary to include FEC in the data area). For this reason, the FEC existing in the output frame 2 is not effectively used.

  As described above, the conventional digital information transmission system enables error correction in any data area of the output frame regardless of the duration or frequency of occurrence of electromagnetic interference in frame processing. As a result, there has been a problem that throughput between information terminals has reached its peak.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent error correction data from being included in an output frame according to the state of occurrence of the interference wave, thereby causing an electromagnetic interference wave. It is an object of the present invention to provide a digital information transmission system, a transmission apparatus, and a transmission method that can perform information transmission with high throughput even in an environment.

  In order to solve the above-mentioned problem, the first aspect of the present invention is to first transmit digital information from a first transmission device to a second transmission device via a signal transmission path affected by an interference wave. In the second transmission apparatus, prior to the transmission of the digital information, the occurrence state of the interference wave is detected for each time slot used for the transmission of the digital information, and based on the occurrence state of the detected interference wave. Then, for each time slot, it is determined whether or not the influence of the interference wave is smaller than a predetermined value, and information representing the determination result is notified to the first transmission apparatus. Then, in the first transmission device, based on the information indicating the determination result notified from the second transmission device, it is determined whether or not the influence of the interference wave is smaller than a predetermined value, and the determination result is determined. The information to be represented is notified to the first transmission apparatus. Then, in the first transmission device, the digital information is configured for a time slot in which the influence of the disturbing wave is a predetermined value or more based on the information indicating the determination result notified from the second transmission device. Assigning data including error correction data relating to data, assigning data not including error correction data relating to data constituting the digital information to a time slot in which the influence of the interference wave is smaller than a predetermined value, The digital information after the allocation process is transmitted to the second transmission device via the signal transmission path. Then, the second transmission device receives the digital information after the assignment processing transmitted from the first transmission device, and determines the received digital information after the assignment processing as the determination. Playback is based on information representing the result.

  In the second aspect of the present invention, when the occurrence state of the interference wave is detected, the time slot synchronization signal wave transmitted from the first transmission device is received, and the time slot synchronization signal wave is used as a trigger. The interference wave parameter including the intensity, duration and frequency component of the interference wave is detected for each time slot.

  According to a third aspect of the present invention, specific data of a plurality of data constituting digital information is preferentially allocated to a time slot in which the influence of the disturbing wave is smaller than a predetermined value during the allocation process. It is a thing.

  According to the first aspect of the present invention, prior to transmission of digital information, a time slot that is subjected to signal degradation due to an interference wave and a time slot that is not subjected to signal degradation are determined. Data including error correction data relating to data constituting digital information is assigned, and data not including error correction code data relating to data constituting digital information is assigned to a time slot determined not to undergo signal degradation. It is done. For this reason, when digital information is transmitted from the first transmission device to the second transmission device, more user data is allocated in an output frame in a period estimated not to be affected by the interference wave than before. It becomes possible to transmit.

  According to the second aspect of the present invention, time slot synchronization is established in the second transmission apparatus on the reception side by the synchronization signal wave transmitted from the first transmission apparatus on the transmission side, and the interference wave is generated for each time slot. Since the interference wave parameters including the intensity, the duration, and the frequency component are detected, it is possible to more accurately determine the period affected by the interference wave.

  According to the third aspect of the present invention, in the assignment process, specific data among a plurality of pieces of data constituting the digital information is preferentially assigned to time slots determined not to undergo signal degradation. For this reason, when digital information is transmitted from the first transmission apparatus to the second transmission apparatus, highly important data of the digital information is transmitted while avoiding a period estimated to be affected by the interference wave. It becomes possible.

  That is, according to each aspect of the present invention, it is possible to prevent error correction data from being included in an output frame in accordance with the state of occurrence of jamming waves, whereby high throughput is achieved even in environments where jamming waves exist. It is possible to provide a digital information transmission system, a transmission apparatus, and a transmission method capable of performing information transmission.

The block diagram which illustrates the hardware constitutions of the digital information transmission system concerning one embodiment of this invention. The block diagram which illustrates the characteristic function of the digital information transmission system concerning one embodiment of this invention. The figure which illustrates the transmission / reception sequence in the digital information transmission system shown to FIG. 1 and FIG. The flowchart which illustrates the process sequence and process content in the training period by the transmitter and receiver of the digital information transmission system shown in FIG. 1 and FIG. The figure for demonstrating the waveform measurement operation | movement of the electromagnetic interference wave synchronized with the modulation timing. 3 is a flowchart illustrating a processing procedure and processing contents in a digital information transmission period by a transmitter and a receiver of the digital information transmission system illustrated in FIGS. 1 and 2. The figure which illustrated in more detail the processing procedure and processing content by the transmitter and receiver of the digital information transmission system shown in FIG. 1 and FIG. The figure for demonstrating the reduction method of the data area for error correction. The figure which illustrates the relationship between the processing content of the input frame in a conventional system, and electromagnetic interference.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
(Constitution)
FIG. 1 is a block diagram illustrating a hardware configuration of a digital information transmission system according to an embodiment of the present invention.
A digital information transmission system according to an embodiment includes an ADSL digital information transmission system, and a metallic signal cable between a transmitter 1 as a first transmission device and a receiver 2 as a second transmission device. Digital information can be transmitted via the communication line 3. As the transmission communication method, for example, a multi-carrier communication method using a plurality of subcarriers (bins) is used.

  In the following, a case where digital information is transmitted in one direction from the transmitter 1 to the receiver 2 as shown in FIG. 1 will be described. However, the present invention also includes a case in which digital information is transmitted bidirectionally between transmission apparatuses having a transmission function and a reception function.

  Both the transmitter 1 and the receiver 2 are connected to a LAN using Ethernet. The transmitter 1 converts transmission data including an Ethernet frame transmitted from an electronic device (not shown) such as a personal computer or a server via a LAN into an analog transmission signal, and transmits the analog transmission signal to the receiver 2 via the communication line 3. And send. The receiver 2 converts the analog transmission signal received from the transmitter 1 via the communication line 3 into the received data of the Ethernet frame, and then sends it to an electronic device (not shown) such as a personal computer or a server via the LAN. Forward.

  The transmitter 1 and the receiver 2 are each configured as hardware, such as LAN-IF (LAN-Interface) 11 and 21, CPUs (Central Processing Units) 12 and 22, DSPs (Digital Signal Processors) 13 and 23, Memory 14 and 24 and AFE (Analog Front End) 15 and 25 are provided.

  The LAN-IFs 11 and 21 transmit and receive data including Ethernet frames to and from electronic devices (not shown) such as personal computers and servers via the LAN.

  The AFEs 15 and 25 convert transmission data into an analog transmission signal by a D / A (Digital-to-Analog) converter and transmit the analog transmission signal to the communication line 3. The AFEs 15 and 25 convert the analog transmission signal received from the communication line 3 into a digital transmission signal by an A / D (Analog-to-Digital) converter, and then perform waveform equalization on the time axis by TEQ.

  The CPUs 12 and 22 have, as basic functions, a control function for transmitting and receiving data consisting of Ethernet frames to and from electronic devices (not shown) such as personal computers and servers via the LAN, and DSPs 13 and 23. Data transfer function between

  The DSPs 13 and 23 include a modem unit and an error correction coding / decoding unit as basic functions.

  When operating as the transmitter 1, the error correction coding / decoding unit performs coding processing for error detection and error correction on the transmission data output from the CPU 12. The modem unit performs digital modulation processing and CP addition processing on the transmission data after the encoding processing for error detection and error correction.

  On the other hand, when operating as the receiver 2, the modem unit deletes the CP from the digital transmission signal output from the AFE 25 and then performs demodulation processing for each subcarrier. Further, the modem unit performs waveform equalization processing on the frequency axis by FEQ, and then performs digital demodulation to restore the received baseband signal. The error correction coding / decoding unit performs error correction decoding processing and error detection processing on the received baseband signal obtained by the demodulation processing, and outputs the received data after the processing to the CPU 22.

  In addition to the above basic functions, the CPUs 12 and 22 and the DSPs 13 and 23 have new functions in order to realize one embodiment. FIG. 2 is a block diagram showing the functional configuration. In FIG. 2, a part of the block diagram and the like are omitted for simplifying the explanation of the new function.

  In order to function as the transmitter 1, the CPU 12 includes a time slot count timing synchronization signal transmission unit 121 and a time slot count information reception unit 122. In order to function as the transmitter 1, the DSP 13 includes a digital information transmission processing unit 131 including an allocation processing unit 132 and a scramble processing unit 133.

  The signal transmission unit 121 for time slot count timing synchronization transmits a signal wave for synchronizing the time slot with the receiver 2 in a training period prior to transmission of digital information.

  The time slot count information receiving unit 122 receives the time slot count information notified from the receiver 2 during the training period and stores it in the memory 14.

  When transmitting the digital information, the allocation processing unit 132 sets a time slot in which the influence of the burst electromagnetic interference wave is less than a predetermined level based on the time slot count information notified from the receiver 2 during the training period. Then, an allocation process that does not include error correction data is performed.

  Based on the time slot count information, the scramble processing unit 133 scrambles the information transmission essential data after the allocation processing so as not to receive signal degradation.

  In order to function as the receiver 2, the CPU 22 includes a time slot count unit 221, an electromagnetic interference wave parameter extraction unit 222, a time slot count information calculation unit 223, and a time slot count information notification unit 224. . Further, the DSP 23 has a digital information transmission processing unit 231 including a descrambling processing unit 232 in order to function as the receiver 2.

  In the training period, the time slot count unit 221 detects an electromagnetic interference wave existing on the communication line 3 for each time slot, using the signal wave for time slot count timing synchronization transmitted from the transmitter 1 as a trigger.

  The electromagnetic interference wave parameter extraction unit 222 extracts the intensity, duration, and frequency components of the electromagnetic interference wave for each subcarrier based on the detection result of the electromagnetic interference wave by the time slot count unit 221 and extracts the extraction result. The electromagnetic interference parameter is stored in the memory 24.

  The time slot count information calculation unit 223 determines, based on the electromagnetic interference parameter stored in the memory 24, a time slot that receives signal degradation and a time slot that does not receive signal degradation, and stores the determination result as time slot count information. 24.

  The time slot count information notification unit 224 notifies the transmitter 1 of the time slot count information stored in the memory 24 via the communication line 3.

  The descrambling processing unit 232 performs a descrambling process on the received baseband signal after the symbol determination of the received signal is performed by Viterbi decoding with reference to the time slot count information stored in the memory 24.

(Operation)
As illustrated in FIG. 3, in the training period, the receiver 2 performs processing for counting time slots based on the signal wave for time slot count timing synchronization received from the transmitter 1, and electromagnetic interference wave parameters. Detection processing and processing for determining the presence or absence of signal degradation due to electromagnetic interference for each time slot (step S41).

  In the digital information transmission period, the transmitter 1 performs the error correction data area allocation process and the scramble process (steps S42 and S43), and the receiver 2 performs the received data descrambling process and the frame reconstruction. Processing is performed (steps S44 and S45).

(1) Operation during training period
In FIG. 4, the processing procedure and processing contents in the training period are shown in detail. The transmitter 1 and the receiver 2 perform a training operation prior to transmission of digital information.

In step S51, the transmitter 1 generates a signal wave for time slot count timing synchronization, and transmits the signal wave to the receiver 2 via the communication line 3. An example of the waveform of this time slot count timing synchronization signal wave is shown in time slot T _s 00 of FIG.

  In step S52, the receiver 2 receives the signal wave for time slot count timing synchronization, and the time slot count unit 221 starts counting the modulation time slot using the signal wave as a trigger.

In step S53, the electromagnetic interference wave parameter extraction unit 222 performs the communication line 3 in the time corresponding to the predetermined number of time slots following the time slot T _s 00 (for example, the time slots T _s 11 to T _s 16 in FIG. 5). The frequency component, the received intensity level, and the duration of the electromagnetic interference wave propagated by are respectively measured. The electromagnetic interference wave parameter extraction unit 222 stores the measurement result in the memory 14 as an electromagnetic interference wave parameter (step S54).

  In step S55, the time slot count information calculation unit 223 determines a time slot that undergoes signal degradation and a time slot that does not undergo signal degradation based on the electromagnetic interference parameter.

For example, the time slot count information calculation unit 223 determines that a time slot whose reception intensity level is equal to or greater than the threshold is a time slot that receives signal degradation by comparing the reception intensity level of the electromagnetic interference wave with a preset threshold. Then, a time slot whose reception intensity level is less than the threshold value is determined as a time slot not subjected to signal degradation. In FIG. 5, the modulation time slots T _s 13, T _s 14, and T _s 15 are determined as time slots that undergo signal degradation, and the modulation time slots T _s 11, T _s 12, and T _s 16 do not undergo signal degradation. It is determined as a time slot.

  In step S56, the time slot count information calculation unit 223 stores the determination result in the memory 24 as time slot count information.

  In step S57, the time slot count information notification unit 224 transmits the time slot count information to the transmitter 1 via the communication line 3.

  In step S <b> 58, the transmitter 1 receives time slot information from the receiver 2 and stores the received time slot information in the memory 14. The transmitter 1 monitors reception of the time slot count information calculated by the receiver 2 after the transmission of the time slot count timing synchronization signal wave in step S51.

(2) Operation during the digital information transmission period
In FIG. 6, the processing procedure and processing contents in the transmission period of digital information are shown in detail. The transmitter 1 and the receiver 2 transmit digital information when the training period ends. Hereinafter, description will be given with reference to FIG.

  In step S61, the transmitter 1 monitors input of transmission data. In this state, transmission data including an Ethernet frame is transmitted from an electronic device such as a personal computer or a server, and the transmitter 1 receives the transmission data via the LAN.

  In step S62, the transmitter 1 executes an error correction coding process. In the error correction coding process, for example, as shown in steps S11 and S12 in FIG. 7, CRC coding and RS coding are performed. In RS encoding, FEC area reservation and creation of an intermediate frame are performed. The FEC area is secured based on the time slot count information stored in the memory 14 for the time slot in which the influence of the burst electromagnetic interference wave exceeds a predetermined level, the area necessary for the EFC is secured. For time slots where the influence of electromagnetic interference is less than a predetermined level, an area necessary for EFC is not secured. The intermediate frame is created according to the size of the output frame and the area necessary for the EFC.

  In step S63, the allocation processing unit 132, based on the time slot count information stored in the memory 14, receives data including FEC relating to transmission data for a time slot in which the influence of the burst electromagnetic interference wave is a predetermined level or more. Allocation processing for allocating data that does not include FEC is performed for time slots in which the influence of allocation and burst electromagnetic interference is smaller than a predetermined level (step S13 in FIG. 7).

  In step S64, the scramble processing unit 133 performs a scramble process on the data area that does not include the FEC after the allocation process based on the time slot count information so as not to receive signal degradation (in FIG. 7, step S14). ).

FIG. 8 is a diagram for explaining an example of the allocation process. As shown in FIG. 8 (g), it is assumed that there is a bursty electromagnetic interference having a strength that causes signal degradation in the modulation time slots T ₁ , T ₃ , and T _4, and no modulation time slot T _2. . In this case, since the output frame 2 transmitted in the modulation time slot T ₂ does not cause signal degradation due to electromagnetic interference, the allocation processing unit 132 performs FEC on the output frame 2 as shown in FIG. Allocate data that does not contain

  In other words, the allocation processing unit 132 does not provide a data area for FEC for the output frame 2 and allocates intermediate frames to all areas. At this time, since it is not necessary to secure a data area for the FEC that is originally necessary, the FEC area becomes smaller than the size of the conventional FEC area as shown in FIG. An intermediate frame may be assigned to the reduced FEC area. Further, this FEC region is created only for a modulation time slot in which a bursty electromagnetic interference wave having a strength that causes signal degradation exists.

  Through the above-described allocation processing, an output frame that does not give FEC to data included in the Ethernet frame received from the LAN can be transmitted without being subjected to signal degradation due to burst electromagnetic interference.

  Therefore, not only the output frame to which FEC is normally performed between the electronic device connected to the transmitter 1 via the LAN and the electronic device connected to the receiver 2 via the LAN, but also the FEC An output frame not attached with can be transmitted and received. For this reason, more user data than before can be allocated to an output frame that does not include FEC. For this reason, high-throughput information transmission is possible even in an environment where bursty electromagnetic interference exists.

  When the allocation process and the scramble process are completed, the digital information transmission processing unit 131 performs the trellis coding shown in Step S15 of FIG. 7 on the transmission data subjected to the allocation process and the scramble process, and then performs Step S65. The modulation process is performed (step S16 in FIG. 7). Specifically, as shown in FIG. 7, in the modulation processing, DMT modulation processing including QAM and IFFT is performed in steps S161 and S162.

  When the modulation process is completed, the digital information transmission processing unit 131 adds a CP to the transmission data after the modulation process in step S17 of FIG. 7, and transmits the transmission data to which the CP is added to the AFE 15. Is output. In step S66, the AFE 15 converts the transmission data into an analog transmission signal, and then transmits the analog transmission signal to the receiver 2 via the communication line 3 (step S18 in FIG. 7).

  On the other hand, the receiver 2 operates as follows. In step S71, the receiver 2 receives the analog transmission signal transmitted from the transmitter 1. As shown in FIG. 7, the received analog signal is A / D converted by the AFE 25 in step S21, and the waveform is equalized on the time axis by TEQ in step S22.

  In step S72, the digital information transmission processing unit 231 executes demodulation processing. For example, in step S23 of FIG. 7, the digital information transmission processing unit 231 deletes the CP from the digital transmission signal output from the AFE 25, and performs DMT demodulation processing for each subcarrier by FFT in step S25. Note that step S24 in FIG. 7 shows time slot counting processing performed in the above-described training period.

  In step S26, the digital information transmission processing unit 231 performs waveform equalization processing on the frequency axis by FEQ on the received signal after the DMT demodulation in step S26, and in step S27, the digital baseband signal is demodulated by QAM demodulation. Restore. Further, in step S28, the Viterbi decoder performs symbol determination of the received signal on the restored received baseband signal.

  In step S73, the descrambling processing unit 232 performs descrambling processing on the received baseband signal (step S29 in FIG. 7). This descrambling process is performed with reference to the time slot count information stored in the memory 24.

  In step S74, the digital information transmission processing unit 231 performs an error correction decoding process on the received baseband signal after the descrambling process. For example, in step S30 in FIG. 7, the digital information transmission processing unit 231 performs an RS decoding process, and in step S31, a CRC check is performed to determine whether there is an information error in the received data after the error correction decoding process. The received data after the inspection is output to the CPU 22. When it is determined that the received data has no error, the CPU 22 converts the received data into an Ethernet frame and transmits it to the LAN.

(effect)
As described above in detail, in one embodiment, prior to transmission of digital information, a signal wave for time slot count timing synchronization is transmitted from the transmitter 1, and the receiver 2 performs time slot synchronization based on the signal wave. I take the. Then, the parameter of the burst electromagnetic interference wave is detected for each time slot, and based on the detection result, the time slot that receives the signal degradation due to the burst electromagnetic interference wave and the time slot that does not receive the determination are determined. The result is notified to the transmitter 1 as time slot count information. When transmitting the digital information, the transmitter 1 assigns data including error correction data to time slots that are subject to signal degradation due to burst electromagnetic interference based on the notified time slot count information. Then, data that does not include error correction data is assigned to time slots that are not subject to signal degradation due to burst electromagnetic interference, and the data is transmitted to the receiver 2 after being scrambled.

  Therefore, it is possible to prevent the error correction data, which is redundant data, from being included in the transmission data during the period that is not affected by the burst electromagnetic interference, thereby transmitting the error correction data. It is possible to improve the throughput peak due to being included in the data. In addition, time slot synchronization is performed in the receiver 2 by the synchronization signal wave transmitted from the transmitter 1, and the interference wave parameter including the intensity, duration, and frequency component of the bursty interference wave is detected for each time slot. As a result, it is possible to more accurately determine the period of time affected by the bursty electromagnetic interference.

[Other Embodiments]
In the above embodiment, the case where data not including error correction data is assigned to a time slot that is not affected by burst electromagnetic interference has been described as an example. At this time, the data to be allocated may be further specified, for example, the IP header may be preferentially allocated. This is because if the data related to the IP header assigned to the time slot affected by the interference wave is damaged beyond repair, that is, the data structure of a part of the IP header is damaged from the receiver. Even if the frame can be transferred to a communication device such as a transfer destination router, the IP packet cannot be transferred from the communication device to the destination. As a result, retransmission processing of unreachable IP packets must be performed between information terminals, and throughput between information terminals decreases. Therefore, assigning a highly important IP header among digital information to time slots that are not affected by bursty electromagnetic interference leads to an improvement in throughput. In addition, upper layer protocols such as a TCP header and an HTTP header may be assigned, or a user arbitrarily designates important data in the user data area by an input operation, and bursts the designated user data. It may be assigned to a time slot that is not affected by electromagnetic interference.

  In the above embodiment, the ADSL digital information transmission system has been described. However, an Ethernet transmission system that transmits digital information using a time-series electrical signal and an OFDM (Orthogonal Frequency Division Multiplexing) modulation / demodulation method that is a multicarrier transmission method are employed. The present invention can also be applied to various digital information transmission systems including wireless digital information transmission systems.

  The configuration of the transmitter and receiver, the modulation / demodulation scheme, the error correction coding / decoding scheme, the frame configuration of the transmission data, and the like can be variously modified and implemented without departing from the scope of the present invention.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Transmitter, 2 ... Receiver, 3 ... Communication line, 11, 21 ... LAN-IF, 12, 22 ... CPU, 13, 23 ... DSP, 14, 24 ... Memory, 15, 25 ... AFE, 121 ... Time Slot count timing synchronization signal transmitter 122, time slot count information receiver 131, 231 ... digital information transmission processor 132, allocation processor 133, scramble processor 221 time slot counter 222, electromagnetic Interference wave parameter extraction unit, 223... Time slot count information calculation unit, 224... Time slot count information notification unit, 232.

Claims (7)

A digital information transmission system for transmitting digital information from a first transmission device to a second transmission device via a signal transmission path affected by an interference wave,
The second transmission device includes:
Prior to transmission of the digital information, means for detecting the occurrence of the jamming wave for each time slot used for transmission of the digital information;
Based on the detection result of the occurrence state of the interference wave, it is determined whether or not the influence of the interference wave is smaller than a predetermined value for each time slot, and information indicating the determination result is sent to the first transmission device. And means for notifying,
The first transmission device includes:
Based on information indicating the determination result notified from the second transmission device, error correction data relating to data constituting the digital information is included for a time slot in which the influence of the interference wave is equal to or greater than the predetermined value. Allocation means for allocating data and allocating data not including the error correction data to a time slot in which the influence of the interference wave is smaller than the predetermined value;
Means for transmitting the digital information after the allocation processing by the allocation means to the second transmission device via the signal transmission path;
The second transmission device includes:
Means for receiving digital information transmitted from the first transmission device after the assignment processing;
A digital information transmission system comprising: means for reproducing the received digital information after the allocation processing based on information representing the determination result.   The means for detecting the occurrence state of the interference wave receives the time slot synchronization signal wave transmitted from the first transmission apparatus, and uses the time slot synchronization signal wave as a trigger to trigger the interference wave for each time slot. The digital information transmission system according to claim 1, wherein an interference wave parameter including an intensity, a duration, and a frequency component is detected.   2. The allocation means preferentially assigns specific data of a plurality of data constituting the digital information to a time slot in which the influence of the interference wave is smaller than the predetermined value. The digital information transmission system according to claim 2. The transmission apparatus used in a digital information transmission system for transmitting digital information between a plurality of transmission apparatuses via a signal transmission path affected by an interference wave,
Prior to transmission of the digital information, means for detecting the occurrence of the jamming wave for each time slot used for transmission of the digital information;
Means for determining whether the influence of the disturbing wave is smaller than a predetermined value for each time slot based on the detection result of the occurrence state of the disturbing wave;
Based on the information indicating the determination result determined by the determination means, data including error correction data related to data constituting the digital information is assigned to a time slot in which the influence of the interference wave is equal to or greater than the predetermined value. Allocation means for allocating data not including the error correction data to a time slot in which the influence of the interference wave is smaller than the predetermined value;
Means for transmitting the digital information after the allocation processing by the allocation means to the transmission device on the receiving side via the signal transmission path;
Means for reproducing the received digital information on the basis of information representing the determination result when the digital information after the allocation processing is received from a transmission apparatus on the transmission side. Transmission equipment.   The means for detecting the occurrence state of the interference wave receives a time slot synchronization signal wave transmitted from a transmission apparatus on the transmission side, and uses the time slot synchronization signal wave as a trigger for the interference wave for each time slot. The transmission apparatus according to claim 4, wherein an interference wave parameter including an intensity, a duration, and a frequency component is detected.   5. The allocation means preferentially assigns specific data among a plurality of data constituting the digital information to a time slot in which the influence of the interference wave is smaller than the predetermined value. The transmission apparatus according to claim 5. A digital information transmission method executed by a digital information transmission system for transmitting digital information from a first transmission device to a second transmission device via a signal transmission path affected by an interference wave,
The second transmission device detects the occurrence state of the interference wave for each time slot used for transmission of the digital information prior to transmission of the digital information;
The second transmission device determines whether or not the influence of the disturbing wave is smaller than a predetermined value for each time slot based on the detected occurrence state of the disturbing wave, and represents the determination result To the first transmission device; and
The first transmission device configures the digital information for a time slot in which the influence of the disturbing wave is equal to or greater than the predetermined value based on the information indicating the determination result notified from the second transmission device. Allocating data including error correction data regarding data, and allocating data not including the error correction data to a time slot in which the influence of the interference wave is smaller than the predetermined value;
The first transmission device transmits the digital information after the assignment processing to the second transmission device via the signal transmission path;
The second transmission device receiving the digital information transmitted from the first transmission device after the assignment processing;
The digital information transmission method comprising: the second transmission device reproducing the received digital information after the allocation processing based on information representing the determination result.