JP6518611B2 - 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 disturbance waves are mixed into a communication line from the outside, and a transmission apparatus and transmission method used in this system.

  In digital information transmission systems that use metal wires as signal transmission paths, electromagnetic waves that are used for other communications and broadcasts, and electromagnetic waves emitted from surrounding electrical and electronic devices are mixed in the signal transmission path, causing conductive electromagnetic interference By affecting the electric signal transmitted through the signal transmission path as a wave, deterioration of communication quality such as an error or omission of transmission information may occur. In order to avoid this, a general digital information transmission system is provided with an error detection and correction function to correct an error occurring in information to be transmitted.

  In many digital information transmission systems, an error correction data area is added to the data (user data) area generated by the communication terminal on the transmission side and transmitted, and the bit error generated during transmission on the reception side is corrected as described above. Forward error correction (FEC) method that uses data for correction. Therefore, increasing the amount of data for error correction increases the error correction capability, but on the other hand, since the redundant data for the total amount of transmission data increases, the transmission rate of user data decreases. That is, the throughput of the digital information transmission system and the improvement of the error correction capability by increasing the amount of error correction data are in a trade-off relationship.

  For example, in IEEE 802.11a, which is one of wireless LAN (Local Area Network) standards, at least 1⁄4 of the data area in the transmission frame, which is a transmission unit, is used as an error correction code data area (coding rate It is defined that the value is 3/4 or less), and as a result, the throughput is suppressed to 54 Mbps at the maximum while the maximum value of the transmission rate considering the modulation scheme is 72 Mbps (bit per second).

  As a transmission / reception technique of a transmission frame including an error correction process in a digital information transmission system, for example, Non-Patent Document 1 relates to Asymmetric Digital Subscriber Line (ADSL).

  That is, in a system using ADSL, when digital information transmitted from an information transmitting apparatus such as a server is input to the ADSL transmitter, the ADSL transmitter performs CRC (Cyclic Redundancy Check) coding on the digital information. , Reed-Solomon Code (RS) coding, scrambling, trellis coding, DMT (Discrete Multi-tone) modulation including Quadrature Amplitude Modulation (QAM) and Inverse Fast Fourier Transform (IFFT), CP (Cyclic) Prefix) Add processing is sequentially performed, then converted into an analog signal by AFE (Analog Front End) processing, and transmitted as an electrical signal to the transmission path.

  On the other hand, in an ADSL receiver, an electrical signal (analog multiplex wave) transmitted through a transmission line is first converted 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 are performed, waveform equalization processing FEQ (Frequency domain Equalizer) on the frequency axis is performed. In the QAM demodulation process included in the DMT demodulation process, Euclidean distance information from each QAM constellation point of the reception signal detected from each frequency component of the analog multiplex wave is calculated and passed to a Viterbi decoder. The Viterbi decoder performs symbol determination of the received signal based on the Euclidean distance information. Thereafter, after the descrambling process and the RS decoding process are performed, it is checked by the CRC whether there is an error in the information after symbol determination, 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 which can not be corrected by the error correction process remains at a predetermined rate, the information is generally discarded.

  When frame data such as Ethernet (registered trademark) frames are to be transmitted using the ADSL digital information transmission system as described above, the following relationship between the transmission signal wave and the electromagnetic interference wave occurs. . The relationship is shown in FIG.

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

  When the Ethernet frame is input to the ADSL transmitter, the ADSL transmitter first removes the MAC header and the FCS from the input frame and is divided into a predetermined number of intermediate frames as shown in FIG. 9 (b). . The size of the intermediate frame is determined from the size of the transmission frame generated in one digital modulation and sent to the transmission path. The size of this transmission frame is determined by training at link establishment in ADSL. Subsequently, an error correction data area (FEC) is added to the data structure in which the divided intermediate frames are linked. The data size of this FEC is also determined according to the size of the transmission frame. Then, the entire frame structure shown in (b) of FIG. 9 is divided into predetermined data sizes as shown in (c) of FIG. 9, and the divided data areas are further rearranged in the arrangement order by a predetermined method. . That is, it is scrambled. Therefore, the IP header information and data area information shown in (a) of FIG. 9 and the FEC data shown in (b) of FIG. 9 are fragmented in the data structure shown in (c) of FIG. It becomes.

Next, the data shown in (c) of FIG. 9 is re-divided into the size of the original output frame as shown in (d) of FIG. At this time, the data structure inside each output frame is rearranged in byte units. Then, data (bits) of each output frame shown in (d) of FIG. 9 is allocated to predetermined plural bins which are subcarriers of ADSL as shown in (e) of FIG. In (e) of FIG. 9, the horizontal axis represents frequency, and the four continuous output frames 1 to 4 shown in (d) of FIG. 9 are within the frequency bandwidth f _w shown in (e) of FIG. It shows an aspect in which each bin is sequentially assigned. f _w is 138 kHz to 2208 kHz for downstream transmission of ADSL, and is composed of 478 bins with a bandwidth of about 4 kHz per bin.

After QAM processing according to the structure of bits allocated 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. It is sent from the machine to the transmission line. The horizontal axis of (f) of FIG. 9 is time. The output frame transmission time interval is the modulation time interval of each output frame and is called the symbol length, but will be called modulation time slot (T _s ) hereafter.

In (g) of FIG. 9, when the four output frames of (d) of FIG. 9 successively propagate the transmission path as the respective signal waveforms of (f) of FIG. The wave example of a wave is shown. Here, the time axis of (f) of FIG. 9 and (g) of FIG. 9 is the same, and the intensity of the burst interference wave is shown by the dotted line of (g) of FIG. Signal component transmitted by the same carrier frequency as this frequency component is interfered, and as a result, an error occurs in reading bit information assigned to the signal waveform component at the receiver. Occur. In the bursty disturbance shown in (g) of FIG. 9, there are frequency components exceeding the intensity level causing signal degradation at times T ₁ , T ₃ , and T ₄ , so the output frame 1 of (d) of FIG. , 3 and 4 will cause bit errors.

Yuasa Shigeru, Shuichiro Asagai, "There are a lot of advanced technologies in a small box to reveal the inside of an ADSL modem," Nikkei NETWORK, pp. 194-199, 2002. 08.

  As described above, in the conventional digital information transmission system such as ADSL, it is necessary to enable error correction even if burst errors due to electromagnetic interference occur in any data region of the output frame. Necessary FEC data area is secured. In addition, as described in (c) of FIG. 9, IP header information, data area information and FEC data are fragmented, and these fragmented data are scrambled so as to be dispersed in all frames.

However, the electromagnetic interference waves generated in the real environment are not always generated at an intensity level that causes signal degradation, but as shown in (g) of FIG. In most cases, bursty disturbance waves included in a part occur irregularly. Thus, it is shown in FIG. 9 (c) and 9, it will be understood that the (g), of FIG. 9 weak electromagnetic waves having no intensity levels resulting signal degradation is sent to the time T ₂ be present (d) Output frame 2 does not generate an information error. On the other hand, in the output frames 1, 3 and 4 of (d) of FIG. 9 transmitted during the times T ₁ , T ₃ and T ₄ during which electromagnetic waves having intensity levels causing signal degradation exist, error correction is performed. Also, the original data may not always be completely recovered. As an example, if the data regarding the IP header present in output frames 1, 3 and 4 is damaged so as to be irreparable, that is, the data is forwarded from the receiver with the partial data structure of the IP header corrupted. Even if the frame can be transferred to the communication device such as the router, the IP device can not transfer the packet from the communication device to the destination. As a result, retransmission processing of non-arriving IP packets must be performed between the information terminals, and the throughput between the information terminals is reduced. The same applies to the TCP header and the HTTP header used in the upper layer protocol as well as the above-mentioned incomplete repair of the IP header.

  As described above, in the conventional digital information transmission system, the importance of the data area in frame (packet) transfer including the IP header regardless of the duration and frequency of electromagnetic interference in frame processing. Is scrambled regardless of the result, and as a result, there is a problem that the throughput between information terminals is reduced.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to enable transmission timing of specific data to be optimized in accordance with the occurrence status of disturbance waves, and thereby, in an environment where disturbance waves exist. It is another object of the present invention to provide a digital information transmission system and its transmission apparatus and transmission method which can perform high-throughput information transmission.

  In order to solve the above problems, according to a first aspect of the present invention, in transmitting 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 transmission of the digital information, the occurrence of the disturbance is detected for each time slot used for transmission of the digital information, and based on the occurrence of the detected interference, It is determined whether or not the influence of the interference wave is smaller than a predetermined value for each time slot, and information representing the determination result is notified to the first transmission apparatus. Then, in the first transmission device, based on the information representing the determination result notified from the second transmission device, a plurality of the digital information for the time slot in which the influence of the interference wave is smaller than a predetermined value A process of preferentially assigning specific data among the data of (1) is performed, and the digital information after the assignment process is transmitted to the second transmission apparatus via the signal transmission path. Then, in the second transmission device, the digital information after the assignment processing transmitted from the first transmission device is received, and the received digital information after the assignment processing is determined as the determination result. Is reproduced on the basis of the information indicating.

  A second aspect of the present invention receives a time slot synchronization signal wave transmitted from the first transmission apparatus when detecting the occurrence of the disturbance wave, and uses the time slot synchronization signal wave as a trigger. An interference wave parameter including the intensity, the duration and the frequency component of the interference wave is detected for each time slot.

  According to a third aspect of the present invention, header information required for transmission among a plurality of data constituting the digital information is allocated to a time slot in which the influence of the disturbance wave is less than a predetermined value.

  According to the first aspect of the present invention, prior to the transmission of the digital information, the time slot which receives signal degradation due to the disturbance wave and the time slot which does not receive it are determined, and for the time slot determined not to receive the signal deterioration, Specific data among a plurality of data constituting digital information is preferentially assigned. Therefore, when digital information is transmitted from the first transmission device to the second transmission device, data of high importance among digital information is transmitted while avoiding a period estimated to be affected by interference waves. It becomes possible.

  According to the second aspect of the present invention, time slot synchronization is achieved in the second transmission apparatus on the reception side by the synchronization signal wave sent from the first transmission apparatus on the transmission side, and the disturbance wave is transmitted every time slot. Since disturbance parameters including intensity, duration and frequency components are detected, it is possible to more accurately determine the period affected by the disturbance.

  According to the third aspect of the present invention, at the time of the allocation, header information of digital information is allocated to a time slot in which the influence of an interference wave is less than a predetermined value. For this reason, it becomes possible to transmit header information essential for transmission of digital information, avoiding a period estimated to be affected by interference waves, thereby reducing the number of times of retransmission processing of digital information, and interference waves. It is possible to suppress the decrease in throughput due to

  That is, according to each aspect of the present invention, it is possible to optimize transmission timing of specific data according to the occurrence status of disturbance waves, thereby enabling high-throughput information transmission even in the presence of disturbance waves. It is possible to provide a digital information transmission system and its transmission apparatus and transmission method.

The block diagram which shows the hardware constitutions of the digital information transmission system concerning one embodiment of this invention. The block diagram which shows the characteristic function of the digital information transmission system which concerns on one Embodiment of this invention. FIG. 3 is a diagram showing a transmission and reception sequence in the digital information transmission system shown in FIGS. 1 and 2; FIG. 3 is a flowchart showing processing procedures and processing contents in a training period by a transmitter and a receiver of the digital information transmission system shown in FIG. 1 and FIG. 2. The figure for demonstrating the waveform measurement operation | movement of the electromagnetic interference wave synchronized with the modulation timing. FIG. 3 is a flowchart showing a processing procedure and processing contents in a digital information transmission period by a transmitter and a receiver of the digital information transmission system shown in FIGS. 1 and 2. FIG. 3 is a diagram showing in more detail the processing procedure and processing contents by the transmitter and receiver of the digital information transmission system shown in FIG. 1 and FIG. 2; The figure for demonstrating the allocation operation | movement to the specific flame | frame of the data transfer essential data area (IP header). The figure which shows the relationship between the processing content of the input frame and electromagnetic interference in the conventional system.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[One embodiment]
(Constitution)
FIG. 1 is a block diagram showing a hardware configuration of a digital information transmission system according to an embodiment of the present invention.
A digital transmission system according to an embodiment is an ADSL digital transmission system, and communication comprising a metallic signal cable between the transmitter 1 as a first transmission device and the receiver 2 as a second transmission device It allows the transmission of digital information via line 3. As a communication method, a multicarrier communication method using a plurality of subcarriers (bins) is used.

  Although FIG. 1 illustrates the case of transmitting digital information in one direction from the transmitter 1 to the receiver 2 for the sake of simplicity, it will be described by way of example. Transmission to the direction is also included in the present invention.

  The transmitter 1 and the receiver 2 are both connected to a LAN (Local Area Network) using Ethernet (registered trademark). The transmitter 1 converts transmission data consisting of an Ethernet frame transmitted from an electronic device such as a personal computer or server (not shown) via the LAN into an analog transmission signal and transmits it to the communication line 3, and the receiver 2 After converting the analog transmission signal received from the communication line 3 into received data of the Ethernet frame, the data is transferred to an electronic device such as a personal computer or a server (not shown) via a LAN.

  Each of the transmitter 1 and the receiver 2 includes, as hardware, LAN-IFs (LAN-Interfaces) 11 and 12, CPUs (Central Processing Units) 12 and 22, and DSPs (Digital Signal Processors) 13 and 23, The memory 14, 24 and the AFE (Analog Front End) 15, 25 are provided. The LAN-IFs 11 and 21 transmit and receive data consisting of an Ethernet frame via a LAN with an electronic device such as a personal computer or a server (not shown). The AFEs 15 and 25 convert the transmission data into an analog transmission signal by the D / A converter and transmit it to the communication line 3, and after converting the analog transmission signal received from the communication line 3 into a digital transmission signal by the A / D converter , Perform waveform equalization processing (TEQ) on the time axis.

  The DSPs 13 and 23 have a modulation / demodulation 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 modulation / demodulation unit performs digital modulation processing and CP (Cyclic Prefix) addition processing on the transmission data after the coding processing for the error detection and the error correction.

  On the other hand, in the case of functioning as the receiver 2, after removing the CP from the digital transmission signal output from the AFE 25, the modem unit performs demodulation processing for each subcarrier, and further performs waveform equalization processing on the frequency axis (FEQ After that, digital demodulation is performed to restore the received baseband signal. The error correction coding / decoding unit performs an error correction decoding process and an error detection process on the reception baseband signal obtained by the demodulation process, and outputs the reception data after the process to the CPU 22.

  As a basic function, the CPUs 12 and 22 have a control function for transmitting and receiving data consisting of an Ethernet frame with an electronic device such as a personal computer or a server (not shown) via a LAN, and between the DSPs 13 and 23 It has a data transfer function.

  The CPUs 12 and 22 and the DSPs 13 and 23 have the following new functions necessary to realize one embodiment in addition to the above basic functions. FIG. 2 is a block diagram showing the functional configuration.

  That is, as a function of the transmitter 1, the CPU 12 has a time slot count timing synchronization signal transmission unit 121 and a time slot count information reception unit 122. The time slot count timing synchronization signal transmission unit 121 transmits a signal wave for synchronizing time slots 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 in the training period, and stores the time slot count information in the memory 14.

  Further, in order to function as the transmitter 1, the DSP 13 has an allocation processing unit 132 and a scramble processing unit 133 as new functions of the digital information transmission processing unit 131. When transmitting the digital information, the allocation processing unit 132 uses the time slot count information notified from the receiver 2 during the training period, to the time slot whose influence by the burst electromagnetic interference is less than a predetermined level. Allocation processing is performed to allocate an IP header, which is data transmission essential data of transmission data. The scramble processing unit 133 scrambles the information transmission essential data after the allocation processing so as not to receive the signal deterioration based on the time slot count information.

  On the other hand, in order to function as the receiver 2, the CPU 22 has 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. There is.

  The time slot counting unit 221 detects an electromagnetic interference wave present 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 in the training period. The electromagnetic interference wave parameter extraction unit 222 extracts the intensity, duration, and frequency component of the electromagnetic interference wave for each subcarrier based on the detection result of the electromagnetic interference wave by the time slot counting unit 221, and extracts the extraction result It stores in the memory 24 as an electromagnetic interference wave parameter.

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

  Further, in order to function as the receiver 2, the DSP 23 has a descrambling processing unit 232 as one function of the digital information transmission processing unit 231. The descrambling processing unit 232 performs a descrambling process on the received baseband signal after 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)
The operation of the digital information transmission system configured as described above will be described.
FIG. 3 is a sequence diagram showing an outline of processing procedures of the transmitter 1 and the receiver 2.
As shown in FIG. 3, first, in the training period, processing of counting time slots based on the signal wave for time slot count timing synchronization transmitted from the transmitter 1 by the receiver 2, electromagnetic interference wave parameter A detection process and a process of determining the presence or absence of signal deterioration due to an electromagnetic interference wave are performed for each time slot (step S41). Subsequently, during the transmission period of digital information, allocation processing and scrambling processing of information transmission essential data are performed by the transmitter 1 (steps S42 and S43), and the receiver 2 descramble processing of received data and frame reconstruction processing Is performed (steps S44 and S45).

Next, the operation described above will be described in more detail.
(1) Operation of Training Period Prior to transmission of digital information, the transmitter 1 and the receiver 2 execute a training operation as follows. FIG. 4 is a flowchart showing details of the processing procedure and the processing content.
First, 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 as a communication counterpart to the communication line 3. An example of this time slot count timing synchronization signal wave waveform, shown in the time slot T _s 00 in FIG.

On the other hand, when the receiver 2 receives the signal wave for time slot count timing synchronization, first, at step S52, the time slot counting unit 221 starts counting of modulation time slots triggered by the signal wave. The propagation, electromagnetic interference parameter extraction unit 222 by the step S53 is, in the time slot T _s 00 subsequent predetermined time slot several minutes (e.g. T _s 11~T _s 16 in FIG. 5), the communication line 3 The frequency component, the reception intensity level and the duration time of the electromagnetic interference wave to be measured are respectively measured, and the measurement result is stored in the memory 14 as an electromagnetic interference wave parameter (step S54).

Subsequently, in step S55, the receiver 2 determines, based on the electromagnetic interference wave parameter, the time slot count information calculation unit 223 the time slot that receives signal deterioration and the time slot that does not receive signal deterioration. For example, the reception intensity level of the electromagnetic interference wave is compared with a preset threshold value, and a time slot in which the reception intensity level exceeds the threshold value is determined as a time slot receiving signal degradation, and a time slot in which the reception intensity level is less than the threshold value Is determined as a time slot that does not receive signal degradation. In FIG. 5, it is determined that the modulation time slots T _s 13, T _s 14 and T _s 15 are time slots that receive signal degradation, and the modulation time slots T _s 11, T _s 12 and T _s 16 do not receive signal degradation. It is determined to be a slot.

  Then, the time slot count information calculation unit 223 stores the above determination result as time slot count information in the memory 24 in step S56. At the same time, in step S57, the time slot count information notification unit 224 transmits the time slot count information to the communication line 3 to notify the transmitter 1.

  In the transmitter 1, after the transmission of the time slot count timing synchronization signal wave, the time slot count information reception unit 122 monitors the reception of the time slot count information in step S58. When the time slot count information is received from the receiver 2, the received time slot count information is stored in the memory 14.

(2) Operation of Digital Information Transmission Period When the training period is over, the transmitter 1 and the receiver 2 execute the digital information transmission operation as follows. FIG. 6 is a flowchart showing the processing procedure and the processing content, and FIG. 7 is a diagram showing the processing procedure and the processing content in more detail.

  The transmitter 1 monitors the input of transmission data in step S61. In this state, transmission data consisting of an Ethernet frame is transmitted from an electronic device such as a personal computer or a server, and when the transmission data is received through the LAN, the digital information transmission processing unit 131 first performs error correction coding processing in step S62. Run. In this error correction coding process, for example, as shown in steps S11 and S12 of FIG. 7, first, CRC coding and RS coding are performed.

  Next, in step S63, the allocation processing unit 132 transmits the information included in the transmission data to the 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 stored in the memory 14. Allocation processing for allocating an IP header, which is essential data, is performed (step S13 in FIG. 7). Subsequently, in step S64, the scramble processing unit 133 scrambles the information transfer essential data area after the allocation processing so as not to receive signal deterioration based on the time slot count information (step S14 in FIG. 7). ).

FIG. 8 is a diagram for explaining an example of the allocation process. Now, as shown in FIG. 8 (g), it is assumed that there is a bursty electromagnetic interference having a strength that causes signal degradation in modulation time slots T ₁ , T ₃ and T ₄ and this does not exist in modulation time slot T _2. Do. In this case the allocation processing unit 132, the output frame 2 to be transmitted in the modulation time slot T ₂ are no signal degradation in electromagnetic interference, the information transmission requirement data as shown in FIG. 8 (c) to the output frame 2 Assign preferentially. For example, an IP header shown in FIG. 8A corresponds to the information transmission essential data. FIG. 8 (b) shows a specific intermediate frame of the output frame 2 to be allocated. In addition to the IP header, essential data used in the upper layer protocol such as a TCP header or an HTTP header may be included as the information transmission essential data.

  The above-described allocation processing makes it possible to transmit information transmission essential data such as an IP header among data contained in an Ethernet frame received from a LAN without receiving signal degradation due to bursty electromagnetic interference waves. Although the user data area of the Ethernet frame is subject to signal deterioration due to electromagnetic interference, it can be corrected by data for error correction.

  Therefore, in principle, there is no non-arriving IP packet between the electronic device connected to the transmitter 1 via the LAN and the electronic device connected to the receiver 2 via the LAN. Therefore, the retransmission procedure of the non-arriving IP packet is unnecessary, and the retransmission processing of the IP packet is performed only when it is determined that the error correction is insufficient between the electronic devices. For this reason, it becomes possible to suppress the fall of the through-put between electronic devices by bursty electromagnetic interference waves.

  When the allocation process and the scrambling process are completed, the digital information transmission processing unit 131 performs trellis coding on the transmission data subjected to the allocation process and the scrambling process as shown in step S15 of FIG. A modulation process is performed by S65. Specifically, as shown in FIG. 7, in steps S161 and S162, DMT (Discrete Multi-tone) modulation processing including QAM (Quadrature Amplitude Modulation) and IFFT (Inverse Fast Fourier Transform) is performed.

  Finally, the digital information transmission processing unit 131 adds a CP to the transmission data subjected to the modulation processing in step S17 of FIG. 7, and outputs the transmission data to which the CP is added to the AFE 15. After converting the transmission data into an analog transmission signal in step S66, the AFE 15 transmits it to the communication line 3 (step S18 in FIG. 7).

  On the other hand, the receiver 2 operates as follows. That is, when the analog transmission signal transmitted from the transmitter 1 is received in step S71, the AFE 25 first A / D converts the analog transmission signal in step S21 as shown in FIG. 7, and then in step S22. Perform waveform equalization processing (TEQ) on the time axis.

  Next, the digital information transmission processing unit 231 of the DSP 23 executes demodulation processing in step S72. For example, as shown in FIG. 7, first, in step S23, after deleting the CP from the digital transmission signal outputted from the AFE 25, DMT demodulation processing is performed for each subcarrier by FFT (Fast Fourier Transform) in step S25. Step S24 in FIG. 7 shows the time slot counting process performed in the training period described above.

  Subsequently, in step S26, the digital information reception processing unit 231 performs waveform equalization processing (FEQ) on the frequency axis with respect to the received signal after the DMT demodulation, and in step S27, performs QAM demodulation to restore the reception baseband signal. Do. Then, the Viterbi decoder performs symbol determination of the received signal on the restored received baseband signal.

  Next, in step S73, the digital information transmission processing unit 231 performs a descrambling process on the reception baseband signal by the descrambling process unit 232 (step S29 in FIG. 7). This descrambling process is performed with reference to time slot count information stored in the memory 24.

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

(effect)
As described above, in one embodiment, prior to transmission of digital information, the transmitter 1 transmits a signal wave for time slot count timing synchronization, and the receiver 2 performs time slot synchronization based on the signal wave. I take the. Then, the parameter of the bursty electromagnetic interference wave is detected for each time slot, and based on the detection result, the time slot that receives signal degradation due to the bursty electromagnetic interference wave and the time slot that is not received are determined. Is notified to the transmitter 1 as time slot count information. When transmitting digital information, the transmitter 1 assigns an IP header, which is information transmission essential data, to a time slot which does not receive signal degradation due to bursty electromagnetic interference based on the notified time slot count information. After scramble processing, the signal is transmitted to the receiver 2.

  Therefore, it is possible to transmit an IP header of high importance among digital information while avoiding a period estimated to be affected by bursty electromagnetic interference, thereby reducing the number of times of digital information retransmission processing. It is possible to suppress the decrease in throughput due to interference waves. Also, time slot synchronization is achieved in the receiver 2 by the synchronization signal wave transmitted from the transmitter 1, and interference wave parameters including the intensity, duration and frequency components of the burst electromagnetic interference wave are detected for each time slot. Thus, it is possible to more accurately determine the period affected by the bursty electromagnetic interference.

[Other embodiments]
In the above embodiment, the IP header is assigned to a time slot that is not affected by bursty electromagnetic interference. However, not limited to this, data essential for information transmission by the upper layer protocol such as a TCP header or an HTTP header may be allocated to a time slot which is not affected by the bursty electromagnetic interference wave. Further, the user may arbitrarily designate important user data in the user data area by an input operation, and assign the designated user data to a time slot which is not affected by the bursty electromagnetic interference wave.

  Also, although the ADSL digital information transmission system has been described as an example in the above embodiment, an Ethernet transmission system for transmitting digital information in time series electric signals and OFDM (Orthogonal Frequency Division Multiplexing) which is a multicarrier transmission system are adopted. The present invention is applicable to various digital information transmission systems, including wireless digital information transmission systems.

  Furthermore, the extraction of electromagnetic interference wave parameters for each time slot and the reflection on allocation / scramble processing shown in the above embodiment are also in accordance with the time slot and frame processing employed in the digital information transmission system used. The information transfer essential data area may be transmitted in a time slot which does not receive signal deterioration.

  In addition, the configuration of transmitters and receivers, modulation / demodulation schemes, error correction coding / decoding schemes, frame configurations of transmission data, types of specific data to be allocated to time slots less affected by interference, etc. deviate from the scope of the present invention. Various modifications are possible within the scope of the invention.

  In short, the present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Transmitter, 2 ... Receiver, 3 ... Communication line, 11, 12 ... 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 ... descrambling processing unit.

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 is
A means for detecting an occurrence state of the disturbance wave for each time slot used for transmission of the digital information prior to transmission of the digital information;
Based on the detection result of the generation state of the disturbance 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 representing the judgment result is sent to the first transmission apparatus. And means for notifying
The first transmission device is
Based on the information representing the determination result notified from the second transmission apparatus, specific data among a plurality of data constituting the digital information for a time slot in which the influence of the interference wave is smaller than a predetermined value Allocation means for preferentially assigning
And means for transmitting the digital information that has been assigned by the allocation means to the second transmission device via the signal transmission path.
The second transmission device is
Means for receiving the digital information transmitted from the first transmission apparatus after being subjected to the assignment process;
And D. means for reproducing the received allocation-processed digital information based on the information representing the determination result.   The means for detecting the occurrence state of the disturbance wave receives the time slot synchronization signal wave transmitted from the first transmission device, and the time slot synchronization signal wave is used as a trigger to cause the disturbance 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 of the signal is detected.   The digital information transmission system according to claim 1 or 2, wherein the allocation means allocates header information of the digital information to a time slot in which the influence of the disturbance wave is less than a predetermined value. A digital information transmission system for transmitting digital information from a first transmission device to a second transmission device through a signal transmission path affected by an interference wave, which is used as at least one of the first and second transmission devices Transmission device, and
Means for detecting an occurrence of the disturbance wave for each time slot used for transmission of the digital information prior to transmission of the digital information when used as the second transmission device ;
When used as the second transmission device, it is determined whether the influence of the interference wave is smaller than a predetermined value for each time slot based on the detection result of the generation state of the interference wave , and A unit for notifying the first transmission apparatus of information indicating a determination result ;
In the case of being used as the first transmission device , based on the information representing the determination result notified from the second transmission device , the digital signal is transmitted to a time slot in which the influence of the interference wave is smaller than a predetermined value. An allocation unit which preferentially allocates specific data among a plurality of data constituting the information;
A unit that, when used as the first transmission device, transmits the digital information that has been assigned by the allocation unit to the second transmission device via the signal transmission path;
A unit for receiving the digital information subjected to the assignment processing transmitted from the first transmission device when used as the second transmission device ;
A transmitter configured to reproduce the received digital information based on information representing the determination result when used as the second transmission device.   The means for detecting the occurrence status of the disturbance wave receives the time slot synchronization signal wave transmitted from the transmission apparatus on the transmission side, and the time slot synchronization signal wave is used as a trigger for the disturbance wave for each time slot. The transmission apparatus according to claim 4, wherein an interference wave parameter including strength, duration and frequency components is detected.   The transmission apparatus according to claim 4 or 5, wherein the allocation unit allocates header information of the digital information to a time slot in which the influence of the disturbance wave is less than a predetermined value. A digital information transmission method implemented 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, comprising:
Prior to the transmission of the digital information, the second transmission apparatus detects the occurrence of the disturbing wave for each time slot used for the transmission of the digital information;
The second transmission apparatus determines whether or not the influence of the interference wave is smaller than a predetermined value for each time slot based on the detected occurrence state of the interference wave, and information indicating the judgment result Notifying the first transmission apparatus of
A plurality of the first transmission devices, which configure the digital information for a time slot in which the influence of the interference wave is smaller than a predetermined value, based on the information representing the determination result notified from the second transmission device Process of preferentially assigning specific data among
The step of the first transmission device transmitting the digital information subjected to the assignment processing to the second transmission device via the signal transmission path;
The second transmission apparatus receives the digital information transmitted from the first transmission apparatus after the assignment process;
And D. the second transmission apparatus reproducing the received allocation-processed digital information based on the information representing the determination result.