EP0843927A1 - Procede de transmission bidirectionnelle de donnees par l'intermediaire d'une ligne a deux fils - Google Patents

Procede de transmission bidirectionnelle de donnees par l'intermediaire d'une ligne a deux fils

Info

Publication number
EP0843927A1
EP0843927A1 EP96917276A EP96917276A EP0843927A1 EP 0843927 A1 EP0843927 A1 EP 0843927A1 EP 96917276 A EP96917276 A EP 96917276A EP 96917276 A EP96917276 A EP 96917276A EP 0843927 A1 EP0843927 A1 EP 0843927A1
Authority
EP
European Patent Office
Prior art keywords
data
transmission
time
time slots
transmitted
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96917276A
Other languages
German (de)
English (en)
Inventor
Johann Pfieffer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ericsson Austria GmbH
Original Assignee
Ericsson Austria GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ericsson Austria GmbH filed Critical Ericsson Austria GmbH
Publication of EP0843927A1 publication Critical patent/EP0843927A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/023—Multiplexing of multicarrier modulation signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/14—Two-way operation using the same type of signal, i.e. duplex
    • H04L5/1469—Two-way operation using the same type of signal, i.e. duplex using time-sharing
    • H04L5/1484—Two-way operation using the same type of signal, i.e. duplex using time-sharing operating bytewise
    • H04L5/1492—Two-way operation using the same type of signal, i.e. duplex using time-sharing operating bytewise with time compression, e.g. operating according to the ping-pong technique

Definitions

  • the invention relates to a method for bidirectional data transmission over a two-wire line, wherein digital data for sending or receiving, e.g. by means of discrete multi-tone modulation (DMT), modulated or demodulated and the data to be sent and received, e.g. by frequency division multiplexing (FDM) or echo cancellation (EC).
  • DMT discrete multi-tone modulation
  • FDM frequency division multiplexing
  • EC echo cancellation
  • known methods of this type separate the e.g. DMT-modulated data in frequency division multiplex operation (FDM), whereby different frequency ranges are defined for the two transmission directions.
  • FDM frequency division multiplex operation
  • Another option for separation is to use the echo cancellation method (EC), in which the influence of the transmitting part on the receiver is suppressed by adaptive filters through the use of adaptive filters. No other separation processes have been used in the prior art in this connection.
  • the FDM method generates a lower and an upper frequency band during transmission in accordance with the two transmission directions.
  • the cable loss is frequency-dependent, it is very difficult to achieve the same transmission quality for both transmission channels. In the majority of cases, the transmission quality is better than in the other direction. In general, however, it is desirable to be able to offer the same quality as possible for both channels.
  • the variation of the transmission capacity is associated with considerable effort, since an adaptation of the band filter used in each case is necessary so that the channel bandwidth can be increased or decreased accordingly.
  • the echo cancellation method which is also known from the prior art, also has disadvantages of different types. In this method, near-crosstalk is a major technical problem, since the signal distance between the transmit and receive signals is very large.
  • the aim of the invention is to provide a method which is characterized by a low level of complexity with regard to the use of hardware or computer power, so that it can be carried out in a simple and inexpensive manner.
  • Another object of the invention is to achieve a very good transmission quality with relatively little technical effort, with a change in
  • Transmission capacity should be simple and inexpensive.
  • TDM time division multiplexing
  • Time frame is divided into a predeterminable number N of time slots, and a number K of these time slots excluding one direction of transmission, e.g. Sending, and the remaining number (N-K) of time slots excluding the other
  • Direction of transmission e.g. Receive, is assigned.
  • TDM is done with the same line loss. This allows both
  • the method is the very simple change in the transmission capacity, which is made possible by the appropriate choice of the number of time slots for the respective transmission direction.
  • the method according to the invention can be used for data transmission over telephone lines, pulse-like interference can occur, for example, through the number dialing on the line, which cause a transmission error that must be corrected.
  • the data transmission does not have to take place via telephone lines; in the context of the invention, it can be carried out via any suitable two-wire line happen.
  • a wide variety of electromagnetic disturbances including those external to the system, can influence data transmission.
  • ARQ Automatic Repeat Request
  • Time frame of the data transmission on average a predeterminable number of
  • Time slots for ARQ (Automatic Repeat Request) retransmissions are provided.
  • transmission overcapacity is therefore constantly available.
  • Time averaging is essentially due to the storage capacity of the ARQ
  • Transfer the data e.g. by means of a computing algorithm.
  • Inversion can be modified.
  • This inversion operation is a very easy to calculate algorithm that can be implemented with little effort.
  • the switching frequency of a source of interference e.g. a power supply unit, with which one of the carrier frequencies of the discrete multi-tone modulation is synchronized.
  • the interference only affects this carrier frequency and its multiples, so that it is adaptive
  • Algorithm can be compensated.
  • TDM time division multiplexing
  • FIG. 1 shows a block diagram for carrying out an embodiment of the method according to the invention
  • FIG. 2 shows a schematic representation of a time frame according to the invention.
  • a bidirectional data transmission of digital data in accordance with the block diagram shown in FIG. 1 is carried out by converting the digital data coming from a data source 1, 4 in the transmission part 50 into an analog transmission signal during transmission and via a line transmitter 13 of a two-wire line 100 to one at the end this line 100 located participants are transmitted.
  • a signal arriving on the two-wire line 100 is routed via the line transmitter 13 as a received signal to the input of a receiving part 51 and converted there into digital data.
  • the line transformer 13 can be used instead of an otherwise conventional hybrid circuit, as a result of which the often problematic adaptation of the hybrid circuit to the line impedance is eliminated from the outset. Interfering crosstalk caused by a hook-up circuit, through which signal residues reach the transmitter on the receiver on the same subscriber side, is therefore ruled out as a source of interference for this method.
  • FIG. 1 In the exemplary embodiment shown in FIG. 1
  • the transmitting and receiving part 50, 51 of both a central data point C (CENTRAL) and a peripheral data point R (REMOTE) is shown in a single block diagram, which is to be understood such that the central data point C is connected to the data point R via the transmitter 13, the two-wire line 100 and a further transmitter 13.
  • Those functional units that only belong to data point C or R are marked with "ATU-C only" or "ATU-R only”.
  • a home video system is described as an exemplary embodiment of an asymmetrical data transmission, in which the video information of various videos is stored in the main data point C in a mainframe computer as data in compressed form and can be called up via a peripheral data point R.
  • the control information is exchanged between data points C and R via a bidirectional control channel, a data rate of 64 kbit / s being specified.
  • This control information can relate to various commands to be issued by the subscriber, such as PLAY, REWIND or the like, as issued by a Video recorders are known and relate to internal control commands and their amount is comparatively small compared to the broadband information transmitted by the central data point C, which essentially contains the video information, which with a data transfer rate of 2,048 Mbit / s only in one direction from C to R is sent.
  • the data rates mentioned can also be chosen completely differently, for example much higher, for the method according to the invention, wherein a data rate of approximately 50 Mbit / s to 150 Mbit / s can also be provided for the broadband information to be transmitted in one direction only.
  • the transmitted information can represent any type of voice, image or data information.
  • Another rate can also be implemented for the bidirectional control channel, which, however, can perform not only control functions but all possible data transmission functions.
  • the transmission part 50 On the input side of the transmission part 50, two different data inputs are formed for the data point C and only one data input for the data point R.
  • the data stream from data source 1 e.g. essentially sends out control commands which reach a send buffer 3 following a scrambler 2, the data coming from the data source 1 being converted in the scrambler 2 according to a predeterminable algorithm. This prevents a longer, constant logical state and achieves a balanced statistical distribution of the binary states.
  • the scrambled signals are buffered in the transmit buffer 3.
  • the data emerging from the transmit buffer 3 are multiplexed via a device MUX with other data which are generated in the ARQ buffer 24 and contain repeat instructions.
  • the data stream comes from the data source 4, which generates the broadband information, via a subsequent scrambler 5 and via an ARQ (Automatic Request) buffer 6, which has a CRC Generator contains, via which an error correction coding takes place, to the second input of the transmitting part 50.
  • the data converted in the scrambler 5 are temporarily stored in the ARQ buffer 6 and repeated if the transmission is faulty.
  • a special ARQ transmission technique according to the invention is described below.
  • the data arriving in series via the inputs of the transmitting part 50 are combined in the encoder 7 to reduce the data rate in a predeterminable length and are assigned to a corresponding symbol for further processing on the basis of a coding table.
  • this coded signal is modulated in the subsequent DMT (Discrete Multi Tone) modulator 8 according to this known method and passed through a high-pass filter 9, which essentially suppresses the speech frequency band in order to avoid interference.
  • the digital output signal of this high-pass filter 9 is converted via a digital-to-analog converter 10 into an analog signal, which reaches the converter 13 via a band-pass filter 11 and then via an amplifier 12.
  • the bandpass filter 1 1 again fulfills the function of the high pass 11 and on the other hand, it cuts off the high-frequency voltage peaks caused by the analog-digital converter 10.
  • the frequency of the analog-to-digital conversion is selected such that the analog-to-digital converter 10 scans at least twice for the highest occurring frequencies.
  • the transmitting part 50 and the receiving part 51 are controlled by a TDM (Time Division Multiplex) unit 30, so that, according to the invention, the data to be transmitted and the data to be received are separated by time multiplex operation, the associated multiplex time frame being divided into a predeterminable number N of time slots and a number K of time slots of the time frame is assigned exclusively to one direction of transmission, for example transmitting, and the remaining number NK of time slots is assigned exclusively to the other direction of transmission, for example receiving.
  • the TDM unit controls the transmitting part 50 and the receiving part 51 by activating them at the appropriate time.
  • the transmitting part 50 and the receiving part 51 are never in operation at the same time, as a result of which the processor power required for the control can be designed to be correspondingly low.
  • the method according to the invention has the advantage of a relatively low bandwidth requirement and a very low level of complexity, which is evident in the hardware or in the required computing power.
  • a considerable part of the computing power is lost for internal communication, while this computing auxiliary capacity can be kept very low in the method according to the invention.
  • the method according to the invention has its limit where the proportion of transmission and reception approaches the 50% percentage limit, since other methods such as echo canceling or the like can then be carried out with the same or less effort.
  • 2 shows the time frame divided into time slots as used in the method according to the invention.
  • the two transmission directions are identified by the terms "upstream” and "downstream".
  • the entire time frame is 20.625 ms long and is divided into different slots of 625 ⁇ s, the majority of the data being transmitted in the downstream direction. This division is particularly advantageous if a bidirectional channel with a low and a unidirectional channel with a high data rate is required in one transmission direction.
  • control commands are transmitted via the bidirectional channel through the time slots designated as CONTROL in the downstream and upstream directions, and via the unidirectional channel through the 30 downstream time slots designated as VIDEO with video information on average over an auxiliary slot.
  • This type of transmission can be for any information.
  • the distribution of the transmission or reception capacities can be adapted to the respective circumstances by choosing the number of upstream or downstream time slots. If the workload changes, this ratio can be adjusted automatically according to the current demand.
  • the specified transmission and reception times have the advantage over frequency division multiplex transmission that data which are not received and to be transmitted have to be processed at the same time, as a result of which the computing power and the hardware expenditure can be designed to be correspondingly low.
  • An encoded and DMT-modulated data unit is transmitted in each DMT slot.
  • a predeterminable number of time slots for ARQ retransmissions are provided in the multiplex time frame of the data transmission on average.
  • the data is sent, it is constantly written into the ARQ send buffer 6 and passed on to the encoder 7 again.
  • the data outgoing from the buffer 6 is transmitted faster than it is filled.
  • the last data block is entered again, but this is recognized by the receiver as a repeated block and automatically removed.
  • the receiver in the peripheral data point R detects the error by means of its CRC error detection in the ARQ unit 24 and then forwards the command via the multiplexer of the transmit buffer 3 for data repetition, which is then sent as control information via the bidirectional channel becomes.
  • this information is demultiplexed in the receiver buffer 27 after passing through the receiver part 51 and a control command is given to the ARQ buffer 6 to repeat the faulty transmission.
  • auxiliary slot In this exemplary embodiment, only one auxiliary slot is available in this exemplary embodiment, which corresponds to an excess capacity of 3.33%.
  • the duration and number of auxiliary slots are not subject to any restrictions in this context and can be adapted to the respective conditions within the technically feasible.
  • the retransmission is carried out in the subsequent time frame, which can extend over several successive time slots. In this example, averaged over time, only one time slot per frame should be used for the repetitions.
  • the time span over which the time average is calculated is determined by the size of the ARQ buffer memory. As soon as this is filled with information, no further repetitions can be carried out and the incorrect data block must be output as transparent.
  • the time period specified for the data repetitions is fixed in the time average. This means that it cannot happen that the transmission is repeated until it is error-free due to a longer-lasting fault and the transmission time increases significantly.
  • the data transmission is repeated even in the event of any disturbances until it is received without errors, but as a result the data throughput drops very sharply.
  • the fixed overcapacity which is between 2 and 10%, but preferably between 3 and 5%
  • the transmission in the method according to the invention is only repeated as often as is possible within the framework of the overcapacity in order to maintain the nominal data throughput. If one can no longer repeat and correctly receive several successive wrong data blocks, it is output transparently.
  • the ratio of peak value to mean value is very large, so that clipping the “signal peak” is a frequent source of error.
  • the digital bit sequence during the repetition process in the transmitter can be modified, for example by a computing algorithm, and then transmitted again.
  • the calculation algorithm used is reversed and the data is recovered. This enables this transmission error to be eliminated very effectively. In particular, it can be carried out in a simple manner in terms of circuitry or computing technology in order to transmit the faulty data in inverted form
  • Another source of interference in the DMT process results from the switching frequency of the voltage supply used, e.g. of the power supply, since this switching frequency is in the transmission range and thus shows its effect as a frequency-selective interference.
  • these interferences depend on other influencing factors, such as the load currently on the power supply.
  • This type of interference can be reduced by synchronizing the switching frequency of the power supply to one of the carrier frequencies of the DMT modulation. This interference therefore only affects this carrier frequency and its multiples, so that they can be easily compensated for by an adaptive algorithm.
  • the receiving part 51 corresponding to the transmitting part 50.
  • the signals arriving from the other subscriber side via the two-wire line 100 and the transmitter 13 are transmitted via a bandpass 14 and via an AGC (Automatic Gain Control) unit. which, regardless of the current signal conditions on the line, generates an approximately amplitude-constant signal, is led to the input of an analog-digital converter 16 belonging to the receiving part 51, the output of which is connected to a high-pass filter 17.
  • the signal present at the input of the high pass 17 is fed back to the AGC unit 15 as an actuating variable via an AGC control circuit 18.
  • the signal is demodulated, from which the pilot tone transmitted to a pilot AGC unit 20 is only supplied in the peripheral data point R, from which a reference signal for the clock generation unit 31 of the peripheral data point R is obtained in the clock generation unit 21.
  • This clock generation unit 31 generates the for the TDM unit 30 and for the system clock Time base.
  • the data point C does not require a clock acquisition unit, since an independent time base is provided here.
  • the linear distortions caused by the transmission link are eliminated in an equalizer 22 connected to the DMT demodulator 19 with an update function.
  • This is followed by the decoding in accordance with a decoding table in a decoder 23, whereupon there is again a serial bit stream at the output of the decoder 23, which is carried over two outputs.
  • the first output which is the same for data points C and R, consists of a receive buffer 27 for control information, a subsequent descrambler 28, in which the data are restored in their correct order, and the data sink 29, which receives the transmitted control data.
  • the second output of the receiving part 51 which is only provided for the data point R, is connected to an ARQ buffer 24, which temporarily stores the transmitted broadband information from the data point C, verifies it and, if necessary, the command via a control unit integrated in the ARQ buffer 24 for retransmitting the incorrectly transmitted data to the multiplex input of the transmit buffer 3, which is retransmitted to the data point C.
  • a descrambler 25 and then a data sink 26 are connected to take over the broadband information. If data is transmitted over two or more two-wire lines, which are at least partially guided at a crosstalk distance, it can happen that the mutual inductive influence of the two-wire lines leads to crosstalk. This undesirable disturbance can occur particularly in a central data system in which many outgoing two-wire lines are routed side by side.
  • this type of interference is avoided by the time-division multiplex operation being carried out synchronously on all two-wire lines. This means that all two-wire lines are either sent or received at the same time, so that interference is no longer possible.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Bidirectional Digital Transmission (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Time-Division Multiplex Systems (AREA)

Abstract

L'invention concerne un procédé de transmission bidirectionnelle de données par l'intermédiaire d'une ligne à deux fils, selon lequel des données numériques à envoyer ou à recevoir, par ex. par modulation de tonalité multiple discrète (DMT), sont modulées ou démodulées. Les données à envoyer ou à recevoir sont séparées par multiplexage dans le temps. Le cadre-temps de multiplex associé est divisé en un nombre prédéterminable N de tranches de temps, dont un nombre K de tranches de temps est attribué exclusivement à un sens de transmission, par ex. l'émission, le nombre résiduel (N-K) de tranches de temps étant attribué exclusivement à l'autre sens de transmission, par ex. la réception.
EP96917276A 1995-06-26 1996-06-21 Procede de transmission bidirectionnelle de donnees par l'intermediaire d'une ligne a deux fils Withdrawn EP0843927A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT1087/95 1995-06-26
AT0108795A AT406533B (de) 1995-06-26 1995-06-26 Verfahren zur bidirektionalen datenübertragung über eine zweidrahtleitung
PCT/AT1996/000112 WO1997001900A1 (fr) 1995-06-26 1996-06-21 Procede de transmission bidirectionnelle de donnees par l'intermediaire d'une ligne a deux fils

Publications (1)

Publication Number Publication Date
EP0843927A1 true EP0843927A1 (fr) 1998-05-27

Family

ID=3506312

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96917276A Withdrawn EP0843927A1 (fr) 1995-06-26 1996-06-21 Procede de transmission bidirectionnelle de donnees par l'intermediaire d'une ligne a deux fils

Country Status (8)

Country Link
US (1) US20020031098A1 (fr)
EP (1) EP0843927A1 (fr)
JP (1) JPH11508425A (fr)
AT (1) AT406533B (fr)
AU (1) AU707189B2 (fr)
CA (1) CA2225754A1 (fr)
IL (1) IL122331A (fr)
WO (1) WO1997001900A1 (fr)

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DE19857821A1 (de) * 1998-12-15 2000-06-29 Siemens Ag Verfahren und Kommunikationsanordnung zur Übermittlung von Informationen mit Hilfe eines Multiträgerverfahrens
JP2000244441A (ja) * 1998-12-22 2000-09-08 Matsushita Electric Ind Co Ltd Ｏｆｄｍ送受信装置
EP2267914A3 (fr) 2000-01-07 2012-09-26 Aware, Inc. Systèmes et procédés pour déterminer la longueur d'une boucle et d'un branchement en dérivation d'une ligne de transmission
PT1245093E (pt) 2000-01-07 2007-01-31 Aware Inc Sistemas e métodos de diagnóstico para modems de portadoras múltiplas
JP4311902B2 (ja) 2000-01-07 2009-08-12 アウェア， インコーポレイテッド 伝送ラインのループ長・ブリッジタップ長を決定するためのシステムおよび方法
DE60127395T2 (de) 2000-04-18 2007-12-06 Aware, Inc., Bedford Datenzuweisung mit änderbaren signal-rauschabstand
JP2002051003A (ja) * 2000-05-22 2002-02-15 Matsushita Electric Ind Co Ltd データ伝送システム及びデータ伝送方法
EP1382188A2 (fr) 2001-04-26 2004-01-21 Aware, Inc. Systemes et procedes de caracterisation de boucle a partir de mesures doubles
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Also Published As

Publication number Publication date
AU5991096A (en) 1997-01-30
IL122331A (en) 2000-08-13
IL122331A0 (en) 1998-04-05
AT406533B (de) 2000-06-26
AU707189B2 (en) 1999-07-08
JPH11508425A (ja) 1999-07-21
WO1997001900A1 (fr) 1997-01-16
CA2225754A1 (fr) 1997-01-16
ATA108795A (de) 1999-10-15
US20020031098A1 (en) 2002-03-14

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