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EP0071192A1
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System for baseband digital transmission in both directions on a two-wire line
Assignee: Telecom Italia SpA
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Filing: 1982-07-22
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Granted: —
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Expires: 2002-07-22
Abstract
Abstract The system is to be applied to a subscriber line. It allows the cancellation of the echo, due to the signal transmitted by a data terminal, from the signal received by the terminal itself, so that the information and the timing signals might be recovered. A fixed line equalization, designed for a mean trunk length, and a circuit which cancels the noise by a correlation between the received and transmitted signal are used. The statistical independence between the digital streams in both directions is obtained by the use of a line code of the binary type.
Inventors
- 👤 Gianfranco Panarotto
- 👤 Adler Tofanelli
- 👤 Luigi Varetto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 14:03
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/235; H04L; H04L5/00; H04L5/14; H04L5/1423; H04B3/238
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
297 words
A system for baseband digital transmission in both directions on a two - wire line (3) characterized in that the transmission is effected by encoding the locally generated digital signal by a binary line - code which maintains the statistical independence between the two digital streams with opposite direetions present at the same time on the line and is designed such that the algebraic sum at the end of each word is equal to zero and the maximum value attained within the word itself does not exceed a predetermined value; further characterized in that the reception is effected by sampling several times within the signalling period the received signal, duly amplitude and bandwidth controlled, by adding to the said received signal a correction signal, by detecting the signs of the obtained sum signal, duly band-limited, and by deco - ding in a way opposite to that effected at the transmitting end the stream of symbols correlated to said signs, the transitions of said sum signal, duly filtered at the fundamental frequency, being used to obtain the timing and synchronism signals by which samplings and sign detections are effected; characterized also in that said correction signal is obtained by the analog-to-digital conversion of said sum signal and by multiplying in both by a coefficient (D), whose choice is dependent on the desired convergence precision and rate, and by a suitable number N of symbols transmitted by the local transmit ter within the same period and those which immediately precede, the obtained products being added to the results of analogous operations effected in the preceding period, and then being orderly multiplied by said transmitted symbols, the new resultant products being finally added to each other and converted from digital to analog form, the final result being said correction signal.
Claim 2
Independent Claim
297 words
A system for baseband digital transmission in both directions on a two - wire line (3) characterized in that the transmission is effected by encoding the locally generated digital signal by a binary line - code which maintains the statistical independence between the two digital streams with opposite direetions present at the same time on the line and is designed such that the algebraic sum at the end of each word is equal to zero and the maximum value attained within the word itself does not exceed a predetermined value; further characterized in that the reception is effected by sampling several times within the signalling period the received signal, duly amplitude and bandwidth controlled, by adding to the said received signal a correction signal, by detecting the signs of the obtained sum signal, duly band-limited, and by deco - ding in a way opposite to that effected at the transmitting end the stream of symbols correlated to said signs, the transitions of said sum signal, duly filtered at the fundamental frequency, being used to obtain the timing and synchronism signals by which samplings and sign detections are effected; characterized also in that said correction signal is obtained by the analog-to-digital conversion of said sum signal and by multiplying in both by a coefficient (D), whose choice is dependent on the desired convergence precision and rate, and by a suitable number N of symbols transmitted by the local transmit ter within the same period and those which immediately precede, the obtained products being added to the results of analogous operations effected in the preceding period, and then being orderly multiplied by said transmitted symbols, the new resultant products being finally added to each other and converted from digital to analog form, the final result being said correction signal.
Claim 3
Dependent Claim
39 words
- 2. System according to claim 1 characterized in that said line code is of the 11 B - 14B type and half the words are obtained by perfor ming the operation of logic negation of the other half.
Claim 4
Dependent Claim
20 words
System according to claim 1 or 2, characterized in that said line is the subscriber line of a telecommunication network.
Claim 5
Dependent Claim
42 words
System according to any of claims 1 to 3, characterized in that the transmitting end comprises: - an encoder (CO), apt to convert the locally generated signal into said line code; - a line amplifier (AL), apt to amplify the encoded signals.
Claim 6
Dependent Claim
204 words
System according to any of claims 1 to 4, characterized in that the receiving end comprises: - a circuit for the automatic gain control (CG), operating on the peak value of the received signal; - a passive network (EQ), apt to limit the band of the received signal and to equalize the line in a fixed way; - a sampling circuit (CC), controlled by a signal at a first frequen cy, connected to the output of that passive network; - a first adder (SO), apt to add to the signal supplied by said sam pling circuit said correction signal; - a low - pass filter (PB), with a cut - off frequency equal at least to the frequency of the signal sent onto the line, connected to the output of said first adder; - a detecting circuit (CD), apt to detect at instants scanned by a signal at a second frequency, the algebraic sign of the signal at the output of said low - -pass filter; - a decoder (DE), apt to convert the sequence of algebraic signs supplied by said detecting.circuit into the signal generated by the remote transmitter, effecting a decoding operation inverse to the one used to obtain that line code.
Claim 7
Dependent Claim
101 words
System according to claim 5, characterized in that said signals at a first and second frequency are obtained by a circuit comprising: - a threshold comparator (CS), apt to detect the zero - crossings of the signal at the output of said low-pass filter (PB); - a pulse generator (FP), connected to the output of said threshold comparator; - a bandpass filter (FR), tuned on the fundamental repetition frequency of the pulses supplied by said pulse generator; - a generator (BT), apt to generate the signals at said first and second frequency by utilizing the signals supplied by said bandpass filter.
Claim 8
Dependent Claim
21 words
System according to claim 6, characterized in that said generator (BT) is a phase loop circuit with a voltage-controlled crystal oscillator.
Claim 9
Dependent Claim
295 words
System according to any of claims 1 to 7, characterized in that said correction signal is obtained by a circuit (CE) comprising: - a delay line, consisting of N - 1 equal delay cells (Tl, T2, ....), which receives at its input the locally generated signal after being coded; - an - analog - to - digital converter (AD) which receives at its input said sum signal; - a first multiplier (MP) which receives at its inputs both the digi tal signal supplied by said analog - to - digital converter, and said coefficient; - N second multipliers (Ml, M2, ...), each of them effecting the multiplication of the encoded signal or of the signal at the output of each of said N-1 delay cells by the signal supplied by said first multiplier; - N second adders (Sl, S2, ... ) each of them effecting the addition of the signal at the output of one of said second multipliers with the signal at the output of the associated one of the N memory cells (Cl, C2, ...); - N memory cells (C1,C2,...), each of them receiving at the writing input the signal supplied by the associated one of said second adders; - N third multipliers (P1,P2,...), each of them effecting the multiplication of the signal at the reading output of each of said memory cells by the coded signal or by the signal at the output of each of said delay cells; - a third adder (AB), apt to add with each other all the signals present at the outputs of said N third multipliers; - a digital - to - analog converter (DA), which receives at its in- input the signal supplied by said third adder and supplies at the output said correction signal.
Claim 10
Dependent Claim
43 words
System according to claim 8, characterized in that said first multiplier (MP) is a circuit apt to effect a number of shifts within the binary word supplied by said analog - to - digital converter (AD) equal to the value of said coefficient.
References Cited (Backward Citations)
US4131767A
Cited
GB2041702A
Cited
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