WO1999033195A1 - Adaptiv nichtlinearer echokompensator - Google Patents
Adaptiv nichtlinearer echokompensator Download PDFInfo
- Publication number
- WO1999033195A1 WO1999033195A1 PCT/DE1998/003671 DE9803671W WO9933195A1 WO 1999033195 A1 WO1999033195 A1 WO 1999033195A1 DE 9803671 W DE9803671 W DE 9803671W WO 9933195 A1 WO9933195 A1 WO 9933195A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- echo canceller
- arrangement according
- linear
- message signal
- coefficients
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
- H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
Definitions
- the present invention relates to a non-linear echo canceller and an echo canceller arrangement which contains such a non-linear echo canceller.
- Echoko compensators are used m the duplex data transmission between two terminals on a line to suppress echoes at the input of a receiver of a terminal, which result from feeding the transmission signal of the same terminal on the line. This echo suppression is necessary if both directions are transmitted in the same frequency band m.
- Transmission systems with echo cancellers are e.g. From US-A-5 132 963, US-A-4 464 545 and US-Re. 31 253 known.
- FIG. 6 shows a block diagram of a typical duplex transmission system with two data transmission devices, which each comprise a transmitter 2, a receiver 4 and a line connection 6, also called a hybrid or fork, the line connection 6 having the function of data from Transmitter 2 m to couple a transmission line 8 and to forward incoming data via the transmission line to the receiver 4.
- Part of the echo is usually compensated for with the aid of an analog line simulation which is housed in the line connection 6.
- Trick et al., Ntz-Archiv Vol. 10, pp. 59-68 (1988) describe several variants of such a line connection. Because of the variety of possible connectable lines and the tolerances of the components used, only a part of the echo signal can be compensated.
- FIG. 7 This figure schematically shows the structure of a data transmission device with a line encoder 16, which converts incoming data into the signal format used on the transmission line 8 and outputs it to a transmission channel 12 via which they are supplied to both the transmitter 2 and the echo canceller 10.
- the transmitter 2 comprises a pulse shaper 18 for temporal smoothing and spectral limitation of the message signal to be transmitted, and then an amplifier (line driver) 20.
- This amplifier is an essential source of non-linear distortions, the extent of which depends on the implementation effort and the power loss required.
- the parameters of the compensator 10 must be set such that the output signal of the echo canceller corresponds as closely as possible to the residual echo signal on a reception channel 14 to which the output of the echo canceller is connected.
- Linear echo components must be taken into account, which result from convolution of the data sequence passing through the transmission channel with an I pulse response h (t) of the transmitter, and non-linear components also occur in the output signal of the transmitter, which are determined by the sequence of the symbols of the data sequence and are due to the fact that the transitional behavior of the transmitter between two different transmission signal symbols can vary depending on the combination of these symbols. This results in interference pulses at the receiver input, which decay over the course of several symbol periods T and which cannot be suppressed with a linear echo canceller.
- the non-linearities are not differentiated according to their point of origin (transmitter or receiver). It follows that if the echo impulse response decays in the course of M symbol periods, where M> N, decays, ie has a duration of M * T, all M symbols transmitted in this period must be taken into account in the echo cancellation.
- the storage method and the Volterra series method are used for this.
- the echo signal is first developed into a Volterra series in which contributions from all combinations of transmission symbols up to a length M of the combination to the echo signal are taken into account.
- the series can be prematurely terminated and the number of coefficients to be taken into account can be reduced, but the effort involved with increasing echo impulse response lengths and multi-stage transmission is considerable.
- a nonlinear echo canceller is known from US Pat. No. 5,146,494, which has a plurality of coefficient memories. comprising brass, which is a symbol of sympathomimetic, and nicotine. Furthermore, a superimposition device is provided with which the coefficients read out from the memories are superimposed on a received signal.
- An echo canceller is known from US Pat. No. 5,148,427, which is formed from a linear and a non-linear echo canceller.
- the linear echo canceller has a digital transversal filter.
- the object of the invention is to provide a compensator structure in which the storage effort is considerably reduced.
- This structure is particularly suitable for the compensation of non-linearities that arise in the transmitter.
- a non-linear echo canceller for an L-stage message signal, with a plurality of groups of coefficient memories, each group being assigned to at least one tuple of N successive symbols of the message signal, a selection circuit which is connected to a transmission channel, in order to receive an expiring message signal and which is able to select the group assigned to the tuple formed by these symbols on the basis of a currently received value and symbols of the message signal preceding Nl, and an overlay circuit which is able to determine the coefficients of the Superimposing the group one after the other in the symbol cycle on a message signal arriving on a receiving channel.
- Digital transversal filters are preferably used as partial filters.
- Each group of coefficients can form a sub-filter in the form of a digital transversal filter.
- the selection circuit is expediently able to excite the sub-filter assigned to the tuple formed by these symbols on the basis of the currently received value and the Nl preceding symbols of the message signal, and the superimposition circuit is set up to superimpose the incoming message signal with the response signals of the sub-filters. This measure ensures that in each symbol period the incoming message signal is superimposed with the first coefficient of a currently excited sub-filter, possibly the second coefficient of a sub-filter excited in the previous symbol period, generally the nth coefficient of a symbol period in an nl symbol period, and thus an exact replication of the non-linearities caused in succession in the transmitter is obtained.
- each group of coefficients can form a column of a memory matrix organized in rows and columns, the selection circuit being able to select the first coefficient of the group assigned to the tuple in one symbol period and subsequent coefficients of the group in subsequent symbol periods, and that Superimposition circuit superimposes the incoming message signal with the sum of the selected coefficients, in order to obtain an exact replica of the non-linearities caused in succession in the transmitter.
- the number of coefficients of each group is expediently chosen in accordance with the duration of the echo signal component caused by the assigned tuples.
- the number of coefficients corresponding to the duration of the longest echo signal component for all groups may be the same or individually adapted to the length of the respective echo signal component.
- the nonlinear echo canceller according to the invention can advantageously be used in combination with a linear echo canceller. Since the linear component in the echo signal weighs, the linear compensator can perform a coarse compensation, so that the amplitudes of the responses to be generated by the individual groups are reduced and the number of coefficients can be kept lower.
- the echo canceller can advantageously be used in a data transmission system with a transmitter which receives data to be transmitted on the transmission channel and sends it to a transmission line, the transmission pulse duration of the message signal in the transmitter being limited to NT, where T is the symbol period of the message signal.
- This limitation of the transmission pulse duration implies that the signal output by the transmitter is determined at any time by a maximum of N symbols, these N symbols also determining the non-linearities m of the output of the transmitter.
- FIG. 1 shows a block diagram of the nonlinear echo canceller according to the invention
- FIG. 3 shows a circuit arrangement for the coefficient determination in the non-linear echo canceller from FIG. 2;
- 6 shows a conventional transmission system
- 7 shows a transmission device with an echo canceller
- Fig. 11 non-linear interference pulses at the input of the receiver.
- FIG. 8 shows an idealized transmission pulse as can be generated by the pulse shaper 18 of a transmission device as shown in FIG. 7. Its duration is limited to a maximum of 2T, where T is the symbol duration of the transmission device.
- 9 shows the eye diagram of a four-stage message signal with such time-limited pulses. The eye diagram shows that the signal level at the Line Driver 20 depends on a maximum of two symbols at any time. Accordingly, the output signal of the line driver can be composed of a linear component and a non-linear component if the individual pulse is limited to 2 * T.
- the linear part is obtained by convolution of the four-stage data sequence to be transmitted with the impulse response of the transmitter h (t).
- the non-linear component is composed of time-shifted distortion pulses that correspond to the transitions between two symbols of the transmission signal.
- the non-linear distortion pulses will be explained in more detail using a practical example.
- a static output characteristic with saturation characteristics is used as a simplification as the non-linear distortion of the line driver.
- the third harmonic of -45dB and the fifth harmonic of -50dB result in a sinusoidal control.
- the non-linear distortion pulses shown in FIG. 10 were measured at the output of the line driver.
- the figure shows a total of five pulses, corresponding to transitions from +3 to ⁇ 1, from +1 to ⁇ 3 and from +3 to -3.
- a further five distortion pulses result from sign reversal, four distortion pulses (+3 to +3, +1 to +1, -1 to -1 and -3 to -3) are not present, and the remaining two (+1 to -1, -1 after +1) are negligible.
- the real transmission signal is thus obtained by superimposing these storage pulses on the linear output signal.
- the reception of the receiver because of the dispersive nature of the echo path, there are disturbing pulses which only decay after several symbol periods. 11 shows these storage pulses.
- a linear echo canceller is not able to compensate for these interference pulses.
- the duration of the transmit pulse is generally limited to N * T, it can be seen that in this case the input level of the amplifier 20 is determined by the last N symbols and that the non-linear interference pulses cannot all be determined by the two symbols last transmitted, but have to depend on the last N symbols. In such a case, a total of L N different storage pulses must be taken into account.
- This non-linear echo canceller comprises a selection circuit 102 m in the form of a demultiplexer with two inputs 104, 106 and L 2 outputs, of which only three, 110, 112, 114, are shown. It is designed for a message signal limited to a pulse duration of 2T.
- the first input 104 is connected directly to a transmission channel, the second 106 via a delay register 120, which outputs the transmission signal delayed by one symbol period T.
- the inputs d of the selection circuit 102 thus each have the symbol d (k) currently transmitted on the transmission channel and the symbol d (kl) transmitted one symbol period earlier.
- An output 110, 112, 114 is assigned to each combination of symbols (d (k), d (k-l)).
- an excitation signal e.g. B. logical 1
- a digital transversal filter 130, 132, 134 is connected to each of the outputs 110, 112, 114.
- Each of these sub-filters contains, in a manner known per se, a chain of delay registers 136, multipliers 138 connected to the input and output of the delay register chain and multipliers 138 connected between the delay registers for multiplication by a stored, adjustable coefficient and an adder 140 for adding the Output signals from the multipliers.
- An output adder 150 adds the output signals to form a compensation signal.
- one of the sub-filters 130, 132, 134 is excited and thereupon reproduces a characteristic sequence of compensation values during a number of periods corresponding to the number of its delay registers 136, which simulates the non-linear disturbance caused by the corresponding symbol pair in the transmitter .
- This disturbance subsides after a certain number of periods a limit below which compensation is no longer required.
- the length of the delay register chain is chosen according to this number of periods.
- symbol pairs which cause identical non-linear disturbances, such symbol pairs can be assigned to a sub-filter together.
- a non-linear echo canceller according to the construction principle shown in FIG. 1 for a message signal generally limited to a duration of N * T has a selection circuit 102 with N inputs and N1 delay register 120, which form a chain, to connect the N last symbols to the inputs of the selection circuit 102 to create.
- the following table shows the maximum number of sub-filters required for transmission pulse lengths of 2T or 3T and various levels.
- the number of sub-filters actually required can be lower than specified in Table I.
- FIG. 2 shows a second embodiment of the non-linear echo canceller according to the invention.
- This comprises a memory array 200 organized in a matrix of m columns and rows with W columns 202, 204, 206, 208, each containing M coefficients, a selection circuit in the form of address logic 210 for reading and writing the coefficients, and a state memory 212 for storing the last M States of the echo canceller, a buffer 214, an adder 216 and a memory 218.
- the state of the echo canceller is defined as the combination of the last N symbols sent. If d (k) denotes the symbol currently being transmitted on the transmission channel, the most recent state stored in cell 1 of the state memory 212 comprises the symbols d (k), d (kl), .., d (kN), the m The state stored in cell 2 comprises the symbols d (kl), d (k-2), .., d (kNl), etc. In each symbol period, the oldest stored state is replaced by the current one. Each state identifies the m of the sub-filter excited in the corresponding symbol period.
- This column with the m stored coefficients forms the sub-filter assigned to the state.
- the addressed coefficient is transferred to the buffer 214 and is added by the adder 216 to a value already contained in the memory 218. After the coefficients for all M states have been read and added, contains the memory 218 contains the compensation value required for the relevant symbol period.
- Adjustment logic 300 receives an error signal indicating the difference between the compensation signal and the actual echo on the receive channel. This difference signal is added or subtracted by the adder 216 to a coefficient loaded with the aid of the address logic 210 m and the buffer 214 is written back and m the memory cell of the coefficient is written back.
- the entire echo canceller 10 expediently includes, in addition to the non-linear described above, a linear echo canceller 402 which, as shown in FIG. 4A, receives data from the transmission channel 12 in parallel with the non-linear 400 and suppresses its linear echo component.
- a linear echo canceller 402 which, as shown in FIG. 4A, receives data from the transmission channel 12 in parallel with the non-linear 400 and suppresses its linear echo component.
- the compensation of linear echo components with the non-linear echo canceller is also possible, since the amplitude and duration of the linear echo components is generally greater than that of the non-linear echo canceller, it is both with regard to the width (number of bits) of the coefficients to be processed in the non-linear echo canceller as well as their number advantageous to provide the linear compensator 402.
- the construction of the linear compensator is shown in FIG. 5.
- the bit width and the length (number of coefficients) of the linear compensator can be larger than that of the sub-filters.
- This filter 404 can be connected in series with the linear compensator 402 alone (FIG. 4B), or it may be connected downstream of an adder 406, as shown in FIG. 4C, so that it acts on the compensation signals of the linear and also the non-linear compensator .
- the latter arrangement represents a favorable solution, in particular in the case of transmission systems for copper two-wire lines, which makes it possible to reduce the number of coefficients of the linear as well as the non-linear compensator.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP98965612A EP1042873A1 (de) | 1997-12-22 | 1998-12-15 | Adaptiv nichtlinearer echokompensator |
JP2000525986A JP2001527315A (ja) | 1997-12-22 | 1998-12-15 | 非線形のエコーキャンセラ |
US09/599,279 US6563870B1 (en) | 1997-12-22 | 2000-06-22 | Nonlinear echo compensator |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19757337.1 | 1997-12-22 | ||
DE19757337A DE19757337C1 (de) | 1997-12-22 | 1997-12-22 | Echokompensatoranordnung |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/599,279 Continuation US6563870B1 (en) | 1997-12-22 | 2000-06-22 | Nonlinear echo compensator |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999033195A1 true WO1999033195A1 (de) | 1999-07-01 |
Family
ID=7853065
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DE1998/003671 WO1999033195A1 (de) | 1997-12-22 | 1998-12-15 | Adaptiv nichtlinearer echokompensator |
Country Status (7)
Country | Link |
---|---|
US (1) | US6563870B1 (de) |
EP (1) | EP1042873A1 (de) |
JP (1) | JP2001527315A (de) |
KR (1) | KR100404012B1 (de) |
CN (1) | CN1254928C (de) |
DE (1) | DE19757337C1 (de) |
WO (1) | WO1999033195A1 (de) |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19801389A1 (de) * | 1998-01-16 | 1999-07-22 | Cit Alcatel | Verfahren zur Echounterdrückung mit adaptiven FIR-Filtern |
DE19801390A1 (de) * | 1998-01-16 | 1999-07-22 | Cit Alcatel | Einrichtung und Verfahren zur Echounterdrückung mit adaptiven FIR-Filtern |
US7433665B1 (en) | 2000-07-31 | 2008-10-07 | Marvell International Ltd. | Apparatus and method for converting single-ended signals to a differential signal, and transceiver employing same |
USRE41831E1 (en) | 2000-05-23 | 2010-10-19 | Marvell International Ltd. | Class B driver |
US6775529B1 (en) | 2000-07-31 | 2004-08-10 | Marvell International Ltd. | Active resistive summer for a transformer hybrid |
US7194037B1 (en) | 2000-05-23 | 2007-03-20 | Marvell International Ltd. | Active replica transformer hybrid |
US7312739B1 (en) | 2000-05-23 | 2007-12-25 | Marvell International Ltd. | Communication driver |
US7606547B1 (en) | 2000-07-31 | 2009-10-20 | Marvell International Ltd. | Active resistance summer for a transformer hybrid |
DE10046901A1 (de) * | 2000-09-21 | 2002-05-02 | Siemens Ag | Verfahren und Vorrichtung zur Verbesserung der Übertragungsqualität in einem paket-orientierten Datenübertragungsnetz |
US6639949B2 (en) * | 2001-12-17 | 2003-10-28 | Ibiquity Digital Corporation | Method and apparatus for pulse overlap pre-compensation in digitally modulated signals |
AU2003251839A1 (en) * | 2002-07-12 | 2004-02-02 | Rambus Inc. | A selectable-tap equalizer, auto-configured equalizer, receiving circuit having an equalizer calibration function, and system having grouped reflection characteristics |
US7292629B2 (en) * | 2002-07-12 | 2007-11-06 | Rambus Inc. | Selectable-tap equalizer |
US8861667B1 (en) | 2002-07-12 | 2014-10-14 | Rambus Inc. | Clock data recovery circuit with equalizer clock calibration |
US7462318B2 (en) * | 2004-10-07 | 2008-12-09 | Biomet Manufacturing Corp. | Crosslinked polymeric material with enhanced strength and process for manufacturing |
US7312662B1 (en) | 2005-08-09 | 2007-12-25 | Marvell International Ltd. | Cascode gain boosting system and method for a transmitter |
US7577892B1 (en) | 2005-08-25 | 2009-08-18 | Marvell International Ltd | High speed iterative decoder |
US8077642B2 (en) * | 2007-12-28 | 2011-12-13 | Intel Corporation | Methods and apparatus for signal echo cancellation and transmitter calibration in full duplex systems |
US10985951B2 (en) | 2019-03-15 | 2021-04-20 | The Research Foundation for the State University | Integrating Volterra series model and deep neural networks to equalize nonlinear power amplifiers |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5146494A (en) * | 1989-07-31 | 1992-09-08 | At&T Bell Laboratories | Overlapping look-up-and-add echo canceller requiring a smaller memory size |
US5148427A (en) * | 1990-04-10 | 1992-09-15 | Level One Communications, Inc. | Non-linear echo canceller |
US5343522A (en) * | 1992-02-05 | 1994-08-30 | Northern Telecom Limited | Adaptive sparse echo canceller using a sub-rate filter for active tap selection |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US31253A (en) * | 1861-01-29 | Machine | ||
SE416367B (sv) * | 1976-09-07 | 1980-12-15 | Western Electric Co | Ekoelimineringsanordning |
US4464545A (en) * | 1981-07-13 | 1984-08-07 | Bell Telephone Laboratories, Incorporated | Echo canceller |
GB2123259A (en) * | 1982-06-25 | 1984-01-25 | Philips Electronic Associated | Digital duplex communication system |
US4669116A (en) * | 1982-12-09 | 1987-05-26 | Regents Of The University Of California | Non-linear echo cancellation of data signals |
GB8511835D0 (en) * | 1985-05-10 | 1985-06-19 | British Telecomm | Adaptive digital filter |
EP0403716B1 (de) * | 1989-06-22 | 1995-09-13 | International Business Machines Corporation | Echokompensationseinrichtung mit Anpassung der Echokompensationskoeffizienten während der Vollduplexübertragung |
JP3336126B2 (ja) * | 1994-09-05 | 2002-10-21 | 富士通株式会社 | エコーキャンセラの波形歪み補償装置 |
JP2850814B2 (ja) * | 1995-12-15 | 1999-01-27 | 日本電気株式会社 | 適応フィルタによる未知システム同定の方法及び装置 |
JP3204151B2 (ja) * | 1997-02-13 | 2001-09-04 | 日本電気株式会社 | 適応フィルタ |
-
1997
- 1997-12-22 DE DE19757337A patent/DE19757337C1/de not_active Expired - Fee Related
-
1998
- 1998-12-15 WO PCT/DE1998/003671 patent/WO1999033195A1/de active IP Right Grant
- 1998-12-15 JP JP2000525986A patent/JP2001527315A/ja active Pending
- 1998-12-15 EP EP98965612A patent/EP1042873A1/de not_active Withdrawn
- 1998-12-15 KR KR10-2000-7007008A patent/KR100404012B1/ko not_active IP Right Cessation
- 1998-12-15 CN CNB988125250A patent/CN1254928C/zh not_active Expired - Fee Related
-
2000
- 2000-06-22 US US09/599,279 patent/US6563870B1/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5146494A (en) * | 1989-07-31 | 1992-09-08 | At&T Bell Laboratories | Overlapping look-up-and-add echo canceller requiring a smaller memory size |
US5148427A (en) * | 1990-04-10 | 1992-09-15 | Level One Communications, Inc. | Non-linear echo canceller |
US5343522A (en) * | 1992-02-05 | 1994-08-30 | Northern Telecom Limited | Adaptive sparse echo canceller using a sub-rate filter for active tap selection |
Non-Patent Citations (1)
Title |
---|
SMITH M.J., COWAN C.F.N, ADAMS P.F.: "NONLINEAR ECHO CANCELLERS BASED ON TRANSPOSE DISTRIBUTED ARITHMETIC", IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS, vol. 35, 1988, XP002100223 * |
Also Published As
Publication number | Publication date |
---|---|
EP1042873A1 (de) | 2000-10-11 |
CN1283337A (zh) | 2001-02-07 |
CN1254928C (zh) | 2006-05-03 |
JP2001527315A (ja) | 2001-12-25 |
KR20010033507A (ko) | 2001-04-25 |
KR100404012B1 (ko) | 2003-11-01 |
US6563870B1 (en) | 2003-05-13 |
DE19757337C1 (de) | 1999-06-24 |
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