JP6578151B2 - Digital information transmission system and digital information transmission method - Google Patents

Description

  The present invention relates to a digital information transmission system and a digital information transmission method for transmitting and receiving digital information by transmitting electrical signals.

  In an information transmission system that converts digital information into electrical signals using a metal communication line such as Ethernet (registered trademark) or ADSL as a transmission medium, electromagnetic waves generated from household appliances in homes or electronic devices in offices are transmitted. In some cases, a conduction interference wave is induced on the communication line, which affects the electrical signal of the transmission line and causes deterioration of the transmission signal, thereby degrading the communication quality such as missing transmission information. Therefore, in a digital information transmission system, it is common to provide various error correction functions to information to be transmitted.

  For example, in an ADSL communication system, in addition to an error correction function, as described in Non-Patent Document 1, as a method for suppressing deterioration of a transmission signal due to a conducted interference wave (noise), between an ADSL modem and a DSLAM, For multiple carrier signals (bins) in the DMT communication system, relatively little information (bits) is assigned to carrier signals of carrier frequencies that are highly affected by noise, and carrier signals of carrier frequencies that are less affected by noise are assigned. Is disclosed to control to allocate a relatively large amount of information.

  Digital information transmitted from an information transmission device such as a server is encoded with CRC (Cyclic Redundancy Code) coding, Reed-Solomon Code (RS) coding, scramble processing, trellis coding, Quadrature Amplitude Modulation (QAM), DMT (Discrete Multitone) modulation, and CP (Cyclic Prefix) addition processing are performed in sequence, and then converted to an analog signal by AFE (Analog Front End) processing. Output as a signal. On the other hand, in the ADSL receiver, the electrical signal transmitted from the telephone line is converted to a digital signal by AFE processing, TEQ (Time domain Equalizer), CP deletion, DMT demodulation, FEQ (Frequency domain Equalizer: Frequency) Axis waveform equivalent), QAM demodulation, Viterbi decoding, descrambling processing, RS decoding, CRC check are sequentially performed and transmitted to a receiving terminal such as a PC.

  Here, as described in Non-Patent Document 1, the trellis encoding / Bidabi decoding process described above is an error correction process of a digital signal, and a past bit string is calculated for each carrier signal (bin). A redundant bit is generated by reference and encoded into a bin together with an information bit sequence to be transmitted. On the receiving side, the most probable bit sequence is estimated from several options by referring to the past bit sequence. Decrypt into sent information. In this way, since not only the bit string received now but also the relation with the bit string received in the past is examined and decoded, accurate information transmission is possible.

Hiroshi Kawamura, Realization technology of ADSL exceeding 20 mega, Nikkei Communications p128-p135, 2003.9.8

  However, the conventional digital information transmission system inevitably reduces the throughput of information transmission due to error correction processing of the digital signal deteriorated during transmission. In particular, in the ADSL trellis code processing, the accuracy of error correction improves as the data length used for decoding, called constraint length, increases. However, as the amount of error correction increases, the data processing time increases accordingly. .

  As described above, the improvement of the error correction capability for improving the information transmission quality at the time of digital transmission has a problem that the time required for the processing becomes longer and the throughput is lowered. In particular, when the error rate increases, the decoding efficiency of error correction (the amount of error correction processing within a unit time) decreases accordingly.

  When ADSL establishes a link between a transmitting device and a receiving device, the training function detects the influence of digital information transmission from the electromagnetic environment and determines the amount of information that can be allocated to each carrier frequency. However, it is not possible to compensate for a decrease in throughput due to electromagnetic interference generated after training.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a digital information transmission system and a digital information transmission method that are excellent in preventing a reduction in information transmission throughput due to electromagnetic interference. .

  In order to achieve the above object, a digital information transmission system and a digital information transmission method of the present invention are configured as follows.

(1) A digital information transmission system in which a first communication device and a second communication device are connected by an information transmission path, wherein the first communication device includes a test frame receiving unit that receives a plurality of test frames; A transmission throughput control unit that analyzes a generation period and duration of a periodic interference wave based on reception results of a plurality of test frames and determines a transmission method; and transmits information to the second communication device by the determined transmission method The transmission throughput control unit, the interference wave parameter extraction unit for extracting the generation period and duration of the periodic interference wave received by the plurality of test frames, the generation period and the duration It calculates a delay time for delaying the transmission timing, and a transmission delay processing unit for determining the transmission delay time, and the transmission unit, the transmission delay Transmitting the information in timing, the second communication device comprises a test frame transmitting unit for transmitting the plurality of test frames to the first communication device, a receiving unit that receives the information.

(2) In the digital information transmission system according to (1), the transmission delay processing unit skips until the transmission timing exceeds the delay time when the duration of the periodic interference wave overlaps the transmission timing. that sends the information transmission delay time.

( 3 ) The digital information transmission system according to ( 2 ), wherein the transmission delay processing unit skips transmission of the information in a frame that overlaps with a duration of the periodic interference wave. And the time required for the second transmission process that is not skipped. If the time required for the first transmission process is shorter than the time required for the second transmission process, the first transmission process is performed. If the time required for the first transmission process is equal to or longer than the time required for the second transmission process, the second transmission process is selected.

(4) A digital information transmission method applied to a digital information transmission system in which a first communication device and a second communication device are connected by an information transmission path, wherein the first communication device includes a plurality of test frames. Determining the transmission method by analyzing the generation period and duration of the periodic interference wave based on the reception results of the plurality of test frames, and determining the transmission method is the periodicity received by the plurality of test frames. Extracting the generation period and duration of the jamming wave, calculating a delay time for delaying transmission timing from the generation period and the duration, and determining the transmission delay timing, and according to the determined transmission method Transmitting information to the second communication device, and transmitting the information includes transmitting the information at the transmission delay timing, and transmitting the information. Device transmits the plurality of test frames to the first communication device, to receive the information.

  That is, according to the present invention, it is possible to provide a digital information transmission system and a digital information transmission method that are excellent in preventing a decrease in throughput of information transmission caused by electromagnetic interference.

  (1) According to the digital information transmission system of the present invention, information is transmitted by a transmission method in which the generation period and duration of a periodic interference wave are determined based on the analysis result. Can be avoided, and a decrease in decoding efficiency in error correction, particularly in the decoding process can be suppressed.

  (2) According to the digital information transmission system of the present invention, it is possible to delay the transmission timing to avoid the deterioration of information due to the periodic component of the interference wave, and to perform error correction, particularly decoding efficiency in the decoding process. Can be suppressed.

  (3) According to the digital information transmission system of the present invention, when there is a periodic jamming wave, it is possible to skip the frame with the timing overlapping with the jamming wave without transmitting it, and transmit at a timing not overlapping with the jamming wave. In addition, it is possible to suppress a decrease in decoding efficiency in error correction, particularly in the decoding process.

  (4) According to the digital information transmission system of the present invention, the optimum transmission process can be selected by comparing the time of the transmission process using the skip and the transmission process not using the skip, thereby reducing the transmission throughput. Can be prevented.

  (5) According to the digital information transmission system of the present invention, the analysis of the periodic interference wave generation period and duration can be performed in detail by transmitting the test frame.

  (6) According to the digital information transmission method of the present invention, information is transmitted by the transmission method in which the generation period and duration of the periodic interference wave are determined based on the analysis result. Can be avoided, and a decrease in decoding efficiency in error correction, particularly in the decoding process can be suppressed.

FIG. 1 is a diagram illustrating an example of a transmission processing block of a digital information transmission system according to each embodiment. FIG. 2 is a diagram illustrating an example of an information input / output relationship between functional components such as a CPU and a DSP (Digital Signal Processor) constituting the transmission device and the reception device. FIG. 3A is a block diagram for explaining transmission throughput control realized by the CPU of the transmission apparatus. FIG. 3B is a block diagram for explaining transmission throughput control realized by the CPU of the receiving apparatus. FIG. 4 is a diagram illustrating an example of a time chart of an ADSL output frame transmission interval and interference wave application timing. FIG. 5 is a diagram showing an example of experimental results showing the relationship between the interference wave application condition and the throughput. FIG. 6 is a diagram illustrating an example of transmission timing skip. FIG. 7 is a diagram illustrating an example of the configuration of a test frame.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a transmission processing block of a digital information transmission system according to each embodiment. FIG. 1 mainly illustrates an example of an internal configuration of a transmission device 1 (for example, an ADSL transmission device) and an example of an internal configuration of a reception device 2 (for example, an ADSL reception device). FIG. 2 is a diagram illustrating an example of an information input / output relationship between functional components such as a CPU and a DSP constituting the transmission device 1 and the reception device 2. FIG. 3A is a block diagram for explaining transmission throughput control realized by the CPU of the transmission apparatus 1. FIG. 3B is a block diagram for explaining transmission throughput control realized by the CPU of the reception device 2.

  First, an experiment conducted by the inventors as an opportunity of the present invention and knowledge obtained therefrom will be described. The digital information transmission system according to the present invention is not limited by the experimental results and the embodiments according to the embodiments described below.

[Experimental Results According to Embodiment]
In general, a burst interference wave suddenly rises from a state where the intensity level is almost zero, and a state where the intensity level is not zero while accompanied by fluctuations in the intensity level is a relatively short time (hereinafter referred to as “duration time”). ”), And the electromagnetic waves follow the process of reaching an almost zero intensity level. Burst jamming waves have a certain width in their frequency band, and when viewed on the time axis, their durations are also wide, and the timing of their occurrence varies with each burst wave. Focusing on the case where the intensity level of the wave is periodic in time, in order to clarify the relationship between the burst disturbance generation time period and its duration and the throughput, as a test disturbance to simulate the burst disturbance An experiment was conducted in which an interfering wave having a constant frequency and a constant duration (hereinafter referred to as a “pulse-modulated jamming wave”) was applied to the ADSL downlink signal while changing the duration and pulse repetition. The frequency of the applied pulse jamming wave was 1173 kHz. This employs the median value of the frequency band of 138 to 2200 kHz used for ADSL downlink communication, but the frequency of the pulse jamming wave to be applied is not limited to this frequency, it is between 138 and 2200 kHz. Any value in the vicinity of the carrier frequency can be adopted.

  FIG. 4 shows a time chart of an example of the ADSL output frame transmission interval and the interference wave application timing in the experiment. In ADSL, transmission data corresponding to one output frame is processed according to the processing flow shown in FIG. 1, and information for one output frame is multiplexed into a plurality of carrier signals (analog waves) by one QAM modulation. Since it is transmitted, the time between QAM modulation timings 250 μs (QAM time slot) is equal to the output frame transmission time interval. For ADSL frame transmission time interval of 250 μs, condition A has a duration of 12.5 μs and a repetition period of 100 μs, condition B has a period of 25 μs and a repetition period of 200 μs, and condition C has a period of 62.5 μs In condition D, the repetition period was 500 μs, and in condition D, the repetition period was 125 μs and the repetition period was 1 msec.

  If the time required for transmission processing at the ADSL output frame transmission timing is Δt (eg, Δt is 1 μs, but Δt varies depending on the communication conditions), transmission within the ADSL output frame transmission time interval of 250 μs Referring to FIG. 4, the ratio of the time over which the pulse modulation interfering wave can interfere with the signal is as follows. Condition A: Δt / 12.5 × 3, Condition B: Δt / 25 × 2, Condition C: Δt / 62.5, Condition D: Since Δt / 125, when the interference time under condition A is 1, the interference times (relative interference time) under conditions B, C, and D are 1.33, 1.67, and 3.33, respectively.

  Next, FIG. 5 shows an example of an experimental result showing the relationship between the application condition of the pulse modulation interference wave and the throughput. Here, the throughput is the number of playback frames in the receiving device per unit time with respect to the number of output frames per unit time generated by the transmitting device. The vertical axis in FIG. 5 is the normalized throughput assuming that the throughput when no pulse jamming wave is applied is 1. It shows that the transmission throughput decreases as the relative interference time increases.

  This experimental result shows that in the trellis coding / Bidabi decoding process employed in ADSL error correction, the quality of the transmission signal deteriorates as the interference time of the pulse modulation interfering wave with the transmission signal becomes longer. FIG. 5 shows that the decoding efficiency in the processing decreases, in other words, the longer the interference time between the transmission signal and the pulse-modulated jamming wave, the more errors in the transmission source signal and the longer the error correction processing time in the receiving apparatus. This is considered to be the main cause of throughput reduction obtained from

  Therefore, in the information transmission system according to the present embodiment, prior to information transmission, generation of an interference wave that characterizes periodicity in burst interference waves by exchanging a predetermined frame structure in common between the transmission device and the reception device in advance. Periodic information and its duration information are extracted and stored, and the information transmission timing that can avoid the influence of periodic interference is calculated from the extracted disturbance period information and duration, and ADSL is delayed to that transmission timing. Send output frame. On the receiving side, the transmitted ADSL signal is temporarily stored in the delay buffer memory, and predetermined information is read from the delay buffer memory, thereby avoiding deterioration of information due to periodic components of jamming waves and suppressing a decrease in throughput. To do. Note that the throughput within the transmission time is lower than when there is no interfering wave by delaying the transmission timing, but the information read from the delay buffer memory is not subject to deterioration due to the interfering wave in principle, and decoding is not possible. Since the processing time is minimized, the reading speed from the delay buffer memory is relatively improved, and the overall information transmission throughput from the transmitting terminal to the receiving terminal can be improved.

[First embodiment]
Hereinafter, this embodiment will be described in detail with reference to FIG. 1, FIG. 2, and FIG.

  As shown in FIG. 1, the information transmission system includes a transmission device 1 (first communication device) and a reception device 2 (second communication device). The transmitter 1 includes a DSP and an AFE. The DSP includes a CRC encoding processing unit 101, a Reed-Solomon encoding processing unit 102, a scramble processing unit 103, a trellis encoding processing unit 104, a QAM modulation processing unit 105, and a DMT modulation process. Unit 106 and CP addition processing unit 107, and AFE includes an AFE processing unit 108. The receiving device 2 also includes a DSP and an AFE, the AFE includes an AFE processing unit 201, and the DSP includes a TEQ processing unit 202, a CP deletion processing unit 203, a DMT demodulation processing unit 204, an FEQ processing unit 205, a QAM demodulation processing unit 206, a Viterbi A decoding processing unit 207, a descrambling processing unit 208, an RS decoding processing unit 209, and a CRC check processing unit 210 are provided. 301 is an information transmission path.

  FIG. 2 is a diagram illustrating a hardware configuration example of the transmission apparatus illustrated in FIG. As shown in FIG. 2, the transmission device 1 includes a LAN-IF 11, a CPU 12, a DSP 13, an AFE 14, and a memory 15, and the reception device 2 includes a LAN-IF 21, a CPU 22, a DSP 23, an AFE 24, and a memory 25. Information processing on the transmission apparatus 1 side according to the present invention is processed by the CPU 12 as a software function, and information processing on the reception apparatus 2 side according to the present invention is processed by the CPU 22 as a software function. When an Ethernet frame (input to the transmitter as a time-series data signal waveform) is transmitted from a server etc. via a LAN cable such as an Ethernet cable connected to the transmitter 1, it is received by the LAN-IF11. Move processing to CPU12.

  The CPU 12 executes information transmission processing described with reference to FIG. 3A, and further, the CPU 12 executes software processing for the ADSL transmission function. This software processing includes “training” processing that uses information obtained by exchanging signals with the DSLAM to calculate the link speed and the amount of data to be transmitted at one modulation. The Ethernet frame is divided into a predetermined data length such as 48 bytes by software processing in the CPU 12, and additional information necessary for subsequent processing is added and stored in the memory.

  The DSP 13 reads information stored in the memory, includes output frame generation that is output from the transmission device to the transmission line by one QAM modulation, and continues until the conversion processing of the QAM modulation information to the analog signal performed by the AFE 14 Perform a series of digital data processing. In this process, CRC (Cyclic Redundancy Code) coding, Reed-Solomon Code (RS) coding, scramble processing, trellis coding, QAM modulation, DMT (Discrete Multitone) modulation, CP shown in FIG. (Cyclic Prefix) Addition processing etc. are executed sequentially.

  The AFE 14 maps the digital data generated by the DSP 13 to an analog signal waveform, sends it as an analog electric signal on a transmission line (telephone line), and transmits it to the receiving device 2.

  In the receiving device 2, a process reverse to the series of processes in the transmitting device 1 described above is performed, information from the analog signal waveform transmitted from the transmitting terminal is digitized, and the original transmission information is reproduced to obtain the information. Transfer to host device.

  Next, digital transmission processing will be described with reference to FIG. 3A. FIG. 3A shows the interrelationships of software function blocks executed by the CPU 12 of the transmission apparatus 1 in FIG. 2, but these functions are the same in the transmission apparatus 1 and the reception apparatus 2. In the present embodiment, the function in the transmission device 1 is described, but the function in the reception device 2 is also described. When a communication request is sent from the information transmission terminal such as a PC or server to the information transmission device 1 via the input / output IF 111, the test frame transmission / reception processing unit 113 of the transmission device 1 sends the test frame transmission / reception processing unit 213 of the reception device 2 to the test frame transmission / reception processing unit 213. Thus, it is requested to continuously transmit n test frames having a predetermined same frame structure to the transmitting apparatus 1 at a predetermined transmission timing. In the case of ADSL, test frames are sent at the transmission frame time interval shown in FIG. Accordingly, the n test frames received by the transmission device are continuously transmitted at a frame transmission interval (250 μsec).

  The waveform (amplitude and phase) of the output signal generated based on the test frame transmitted from the receiver 2 to the transmitter 1 is degraded by the burst electromagnetic interference before it reaches the transmitter after propagating through the transmission path. (Distortion and displacement from the original signal waveform of amplitude and phase).

  The n test frames sent from the receiving device 2 to the transmitting device 1 are directly sent to the test frame transmission / reception unit 113 of the transmitting device 1 for error correction performed when the receiving device 2 generates the test frame. The decoding process corresponding to the encoding of is not performed. Data related to the burst interference wave of the test frame received by the test frame transmission / reception processing unit 113 of the transmission apparatus 1 is stored in the storage unit 116. On the other hand, the storage unit 116 stores data of a predetermined frame structure of the test frame as reference data.

  Next, the interference wave parameter extraction unit 114 reads the reference data stored in the storage unit 116 and n test frame data delivered from the receiving device 2, and the reference data and n time-series test frame data Are extracted, information on the frequency distribution of burst electromagnetic interference received on the transmission path, information on the generation period, and duration information are extracted. Specifically, for n test frames transmitted at predetermined equal time intervals, the test frame from what number test frame to which bit error is the same as the bit position in the test frame where the bit error has occurred The generation period of the burst interference wave is extracted by detecting whether the same bit error has occurred continuously, and the duration is extracted by detecting whether the same bit error has occurred continuously. Hereinafter, the burst jamming wave from which the generation cycle can be extracted is referred to as a periodic jamming wave. The obtained periodic interference wave generation period and duration are stored in the storage unit.

  Here, when a guard interval time is set between test frames that are continuously transmitted, extraction is performed by adding the guard interval time to the period information and duration of the periodic interference wave generation period.

  The transmission delay processing unit 115 calculates a delay time for delaying the information signal transmission timing from the transmission device 1 to the transmission path from the generation period and the duration time stored in the storage unit 116. For example, in the case of ADSL, as shown in Fig. 4, information signals are sent at intervals of 250 μs, so if a certain transmission timing matches the timing of the above generation cycle, or if it falls within the duration time Then, skip until the initial transmission timing exceeds the delay time. FIG. 6 is a diagram illustrating an example of transmission timing skip. When there is an interference wave generated periodically as shown in condition A, a frame with a timing overlapping with the interference wave is skipped without being transmitted, and is transmitted with a timing not overlapping with the interference wave.

  When the information (signal waveform) sent from the information device 1 is delivered to the receiving device 2, the original signal sent from the transmitting device 1 through the processing from the ADE processing unit 201 to the CRC inspection processing unit 210 of the receiving device 2 Is once stored in the delay buffer memory 217 in the receiving device 2. The transmission delay processing unit 215 of the receiving device 2 reads the original transmission information stored in the delay buffer memory 217, and passes it to the processing program in the receiving terminal connected to the receiving device 2 via the input / output interface 211.

  By the series of processes shown in the present embodiment, it is possible to suppress the deterioration of the decoding efficiency in the error correction, particularly the decoding process, by avoiding the deterioration of the information due to the periodic interference wave generation period. In this embodiment, the throughput within the transmission time from the transmission device 1 to the reception device 2 is lower than that in the case where there is no periodic interference wave by the amount by which the transmission timing is delayed, but is read from the delay buffer memory 117. In principle, the information to be transmitted has not been degraded by the periodic interference wave, and the decoding processing time is minimized, so that the reading speed from the delay buffer memory 117 is relatively improved, and the transmitting terminal The overall throughput of information transmission from the terminal to the receiving terminal can be improved.

[Second Embodiment]
In the first embodiment, the transmission timing of the test frame is immediately after a communication request is sent from the information transmission terminal such as a PC or server to the information transmission device, and the generation period and duration of the periodic interference wave from the test frame After calculating, the transmission of information from the information transmission terminal is started to avoid interference with the transmission signal due to the periodic interference wave as much as possible, thereby reducing the throughput within the transmission time of the digital information between the transmission and reception terminals However, the present invention is not limited to this. For example, if the randomness of the interference wave becomes high, it takes time to calculate the generation period and duration of the periodic interference wave. Also, if the generation period is long or the interference wave has a long duration that can be regarded as a continuous interference wave, adopting the method of the first embodiment in order to avoid these effects will cause the transmission timing to be skipped. There is a possibility that the throughput is lowered and the throughput is lowered in the transmission time between the transmitting and receiving terminals.

Therefore, in the second embodiment, when the interference wave parameter extraction unit 114 of FIG. 3A executes the periodic interference wave period information calculation process or the duration calculation process from n consecutive test frames, the k th testing frame and a (k + 1) th interference wave period extracted from a test frame (P _k) or than the duration (T _k) (k + 1) -th test frame and (k + 2) -th when the interference wave period extracted from a test frame (P _{k + 1)} or duration (T _{k + 1)} becomes small, the maximum generation period: P _max and P _k, the maximum duration: the T _{max Tk} is determined, and the period information calculation process and the duration calculation process are terminated. The determination of P _max and T _max is determined, for example, as P _max = P _k when one is performed prior to the other, and T _max = T _k is determined when T _max is not yet determined.

On the other hand, if the determination of P _max or T _max is not completed even after a predetermined time has passed, it is assumed that there are no periodic interference waves in the electromagnetic environment where the digital transmission system is located, and transmission is performed using the normal transmission method To do.

  Furthermore, when the transmission timing to be skipped increases, the transmission delay processing unit 115 refers to the data in the storage unit 116 and determines that the normal transmission method (non-skip transmission method) can suppress the decrease in throughput. Also, it is assumed that transmission is performed by a normal transmission method. That is, the time required for the first transmission process is compared with the time required for the transmission process with the skip (first transmission process) and the time required for the normal transmission process (second transmission process). When the time required for the transmission process is shorter, the first transmission process is selected, and when the time required for the first transmission process is longer than the time required for the second transmission process, the second transmission process is selected. That is, when the time required for calculating the periodicity of the interference wave or the time required for transmission while avoiding the influence of the interference wave is shorter than the time required for the second transmission process, information is transmitted by the first transmission process, When the time required for the first transmission process is longer than the time required for the second transmission process due to a high skip frequency or the like, information is transmitted by the second transmission method.

  According to this embodiment, even when information generation using skip is uniformly selected even when the generation period is long or the duration is long like a continuous jamming wave, the transmission throughput may be reduced. By comparison, an optimal transmission process can be selected, and a decrease in transmission throughput can be prevented.

[Third embodiment]
A specific configuration example of the test frame will be described with respect to the test frame employed in the first and second embodiments. FIG. 7 is a diagram illustrating an example of the configuration of a test frame. The configuration of the Ethernet frame input to the transmitter 1 is a configuration in which a payload portion (IP header area and data area) having a maximum length of 65535 bytes is sandwiched between a MAC header and an FCS (Frame Check Sequence) area. However, when the transmitting apparatus 1 receives the Ethernet frame, the MAC header and FCS are removed from the Ethernet frame, and the series of processing shown in FIG. 1 is performed on the payload portion. When the transmission device 1 receives the test frame, the test frame is processed in the same manner as the Ethernet frame. However, the configuration of the test frame is a UT area that is not used for processing as a test frame as an area corresponding to the IP header area at the top. A data area other than the UT area is an area to which necessary information as a test frame is assigned. As shown in FIG. 7, the test frame configuration includes a frame counter area for identifying n consecutive test frames and an error marker area for recording traces of bit errors due to periodic interference waves. The error marker area is composed of a predetermined test bit string. If the n test frames transmitted from the receiving device 2 to the transmitting device 1 undergo waveform degradation due to periodic interference waves while propagating through the information transmission path 301 as transmission signal waveforms, the test frame is transmitted from the receiving device 2. Since the test bit string is different after the reception of the transmission device 1, the influence of the periodic interference wave is detected by different portions of the bit string. The RF area is used for adjusting the byte length of the test frame and for other purposes. The test frame is adjusted to a minimum fixed byte length sufficient to detect the periodic interference wave generation period and duration.
[Other Embodiments]
In the first, second, and third embodiments, the information transmission process when applied to an ADSL transmission / reception system has been described. However, the present invention is not limited to this. Since it is only necessary to prepare a reference frame in advance according to the frame used in the digital information communication system to be used, an Ethernet transmission system that transmits digital information as a time-series electrical signal, or OFDM (Orthogonal Frequency Division Multiplexing) modulation The present invention can also be applied to various digital information transmission systems including a wireless digital transmission system adopting the method.

  In the first embodiment, the n test frames sent from the receiving apparatus 2 to the transmitting apparatus 1 are decoded corresponding to the encoding for error correction performed when the receiving apparatus 2 generates the test frame. It was assumed that no processing was performed. However, encoding and decoding processing for error correction may be performed on n test frames in the same manner as in normal frame transmission / reception. In this case, detection of a bit error in the test frame indicates the presence of a periodic interfering wave that cannot be reproduced by original correction even with error correction. In normal frame transmission / reception, retransmission control is performed between transmission / reception terminals. Is done. However, even in this case, it is possible to avoid a decrease in throughput required for retransmission control performed between the transmitting and receiving terminals by skipping the transmission timing so as to avoid a periodic interference wave incapable of error correction.

  The digital information transmission system described above will be summarized below.

  The digital information transmission system includes a test frame transmission / reception processing unit that transmits a plurality of test frames to a receiving device at a certain time interval, triggered by an information transmission request from a transmitting terminal, and a test frame at the time of transmission. Interference wave parameter extraction unit that extracts the frequency, generation period, and interference wave duration of the periodic electromagnetic interference received, and calculates the transmission timing and time with less influence of the periodic interference wave from the extracted generation period and duration, It has a transmission delay processing part which performs transmission delay processing to the said transmission timing, It is characterized by the above-mentioned.

  Thereby, since the influence of the periodic electromagnetic interference wave can be avoided as much as possible, it is possible to suppress a decrease in error correction efficiency of digital information and to compensate for a decrease in throughput.

  The information transmission processing procedure described above can be executed by software. For this reason, the above-described processing can be easily realized simply by downloading a program for executing the above-described processing procedure, installing this program in the information processing apparatus, and executing it. Alternatively, this program is simply installed in the information processing apparatus through a computer-readable storage medium storing a program for executing the above processing procedure, for example, a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, and the like. Thus, the above processing can be easily realized.

  For example, the digital information transmission system (the transmission device 1 and the reception device 2) can download the program, store the downloaded program, and complete the installation of the program. The digital information transmission system can read the program from a computer-readable storage medium, store the read program, and complete the installation of the program. Thereby, the digital information transmission system can easily realize the processing based on the installed program.

  In addition, various modifications can be made 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 ... Transmission apparatus, 11 ... LAN-IF, 12 ... CPU, 13 ... DSP, 14 ... AFE, 15 ... Memory, 101 ... CRC encoding processing part, 102 ... Reed-Solomon encoding processing part, 103 ... Scramble processing part 104 ... Trellis encoding processing unit, 105 ... QAM modulation processing unit, 106 ... DMT modulation processing unit, 107 ... CP addition processing unit, 108 ... AFE processing unit, 111 ... I / O IF, 112 ... Transmission throughput control unit, 113 Test frame transmission / reception processing unit 114 Interference wave parameter extraction unit 115 Transmission delay processing unit 116 Storage unit Delay 117 Buffer memory 2 Receiving device 21 LAN-IF 22 CPU 23 DSP, 24 ... AFE, 25 ... Memory, 201 ... AFE processing unit, 202 ... TEQ processing unit, 203 ... CP deletion processing unit, 204 ... DMT demodulation processing unit, 205 ... FEQ processing unit, 206 ... QAM demodulation processing unit, 207 ... Viterbi decoding processing unit, 208 ... Descramble processing unit, 209 ... RS decoding processing unit, 210 ... CRC check processing unit, 211 ... Input / output IF, 212 ... Transmission throughput control unit, 213 Test frame transmission and reception processing section, 214 ... disturbance parameter extraction unit, 215 ... transmission delay processing unit, 216 ... storage unit, 217 ... delay buffer memory, 301 ... information transmission path.

Claims (4)

A digital information transmission system in which a first communication device and a second communication device are connected by an information transmission path,
The first communication device is:
A test frame receiver for receiving a plurality of test frames;
A transmission throughput control unit that analyzes a generation period and duration of a periodic interference wave based on reception results of a plurality of test frames and determines a transmission method;
A transmission unit for transmitting information to the second communication device according to the determined transmission method;
With
The transmission throughput control unit
An interference wave parameter extraction unit for extracting the generation period and duration of the periodic interference wave received by the plurality of test frames;
Calculating a delay time for delaying transmission timing from the generation period and the duration, and determining a transmission delay timing; and
With
The transmission unit transmits the information at the transmission delay timing,
The second communication device is:
A test frame transmission unit that transmits the plurality of test frames to the first communication device; a reception unit that receives the information;
A digital information transmission system comprising: The transmission delay unit, when the duration of the periodicity disturbance overlaps the transmission timing, wherein the transmission timing is characterized that you send the information in the transmission delay time to skip to greater than the delay time Item 4. The digital information transmission system according to Item 1.   The transmission delay processing unit includes: a time required for a first transmission process that skips transmission of the information in a frame that overlaps with a duration of the periodic interference wave; and a time required for a second transmission process that is not skipped. In comparison, if the time required for the first transmission processing is shorter than the time required for the second transmission processing, the first transmission processing is selected, and the time required for the first transmission processing is the second time. 3. The digital information transmission system according to claim 2, wherein the second transmission process is selected when the time required for the transmission process exceeds the time required. A digital information transmission method applied to a digital information transmission system in which a first communication device and a second communication device are connected by an information transmission path,
The first communication device is:
Receive multiple test frames,
Based on the results of receiving multiple test frames, determine the transmission method by analyzing the generation period and duration of periodic jamming,
Determining the transmission method includes extracting a generation period and duration of a periodic interference wave received by the plurality of test frames, and calculating a delay time for delaying transmission timing from the generation period and the duration. Determining transmission delay timing,
Transmitting information to the second communication device by the determined transmission method;
Transmitting the information includes transmitting the information at the transmission delay timing;
The second communication device is:
Transmitting the plurality of test frames to the first communication device;
A digital information transmission method for receiving the information.