EP1649651A1 - Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulation - Google Patents
Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulationInfo
- Publication number
- EP1649651A1 EP1649651A1 EP04726173A EP04726173A EP1649651A1 EP 1649651 A1 EP1649651 A1 EP 1649651A1 EP 04726173 A EP04726173 A EP 04726173A EP 04726173 A EP04726173 A EP 04726173A EP 1649651 A1 EP1649651 A1 EP 1649651A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- communication devices
- carrier communication
- impulse response
- parameters
- channel
- 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- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0004—Modulated-carrier systems using wavelets
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
- H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
- H04L25/03038—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a non-recursive structure
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03343—Arrangements at the transmitter end
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03375—Passband transmission
- H04L2025/03414—Multicarrier
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
- H04L2025/03439—Fixed structures
- H04L2025/03445—Time domain
- H04L2025/03458—Lattice
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
- H04L2025/03439—Fixed structures
- H04L2025/03445—Time domain
- H04L2025/03471—Tapped delay lines
- H04L2025/03484—Tapped delay lines time-recursive
- H04L2025/0349—Tapped delay lines time-recursive as a feedback filter
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03592—Adaptation methods
- H04L2025/03745—Timing of adaptation
- H04L2025/03764—Timing of adaptation only during predefined intervals
- H04L2025/0377—Timing of adaptation only during predefined intervals during the reception of training signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
Definitions
- the present invention relates to an equalization method to be used in cosine modulated filter bank-based multi-carrier communication devices and/or in wavelet packet modulation-based multi-carrier communication devices in order to reduce the adverse effects of the transmission channel and to an apparatus using this method.
- a cycle prefix chosen to be preferably longer than the channel impulse response, is commonly added to each transmitted symbol in order to avoid inter-symbol interferences. If the channel impulse response is longer than the cycle prefix, an additional time-domain equalizer is used at the receiver's side for shortening the channel impulse response.
- a simple frequency domain equalizer with complex coefficients can be employed in the receiver after the OFDM modulation in order to retrieve the sent data.
- Fig. 1 shows for example the block-diagram of a communication system using such prior art multi-carrier communication devices.
- the data 10 to be sent over the channel 103 is first fed to the serial to parallel converter 101 before being converted from the frequency domain into the time-domain by inverse discrete Fourier transform (DFT) in the OFDM modulator 102.
- DFT inverse discrete Fourier transform
- the modulated data 12 out of the sender 11 is then sent over the transmission channel 103 with the channel noise 104.
- the transmission channel's output 13 at the input of receiver 14 is fed into an optional time-domain finite impulse response (FIR) equalizer 105 for shortening the channel impulse response such that the shortened channel impulse response becomes shorter than or equal to the cycle prefix.
- FIR time-domain finite impulse response
- the demodulator's output is connected to the frequency domain equalizer (FEQ) 107, the output of which is then converted in the parallel to serial converter 108.
- FEQ frequency domain equalizer
- Such prior art multi-carrier communication devices have a major drawback in that OFDM modulation has a poor stop-band attenuation. This results in significant inter-channel interferences when adjacent channels are used simultaneously in a real communication system. In order to avoid or to reduce these inter-channel interferences, the different channels must be chosen sufficiently far apart from each other, thus resulting in a poor spectral efficiency of the communication system, that is in an inefficient usage of the communication system's available bandwidth.
- multi-carrier communication devices In order to increase the communication system's spectral efficiency, other multi-carrier communication devices can be used, such as for example cosine modulated filter bank-based multi-carrier communication devices or wavelet packet modulation-based multi-carrier communication devices, which provide higher stop-band attenuation, leading to lower inter-channel interference.
- the frequency domain combiner needed by the receiver of such communication devices in order to estimate the sent data is considerably more complex than the frequency domain equalizer 107 needed for example in the case of OFDM modulation, making such multi-carrier communication devices unattractive for a practical implementation in a data communication system.
- An example of a frequency combiner for use in a multi-carrier transmission system using wavelet modulation is for instance described in Patent US 5,636,246. Summary of the invention
- An aim of the present invention is thus to propose a method and an apparatus for efficient channel equalization in cosine modulated filter bank-based multi-carrier communication devices and/or in wavelet packet modulation-based multi-carrier communication devices.
- Another aim of the present invention is to propose a method and an apparatus for channel equalization in cosine modulated filter bank- based multi-carrier communication devices and/or in wavelet packet modulation-based multi-carrier communication devices that can be implemented in a data communication system at lower costs than prior art methods or apparatus.
- a method for channel equalization in a data communication system comprising at least two cosine modulated filter bank-based multi-carrier communication devices or at least two wavelet packet modulation-based multi-carrier communication devices being connected over a single transmission channel, the channel equalization being a recursive time-domain equalization comprising a finite impulse response equalization part and an infinite impulse response equalization part, as well as by an apparatus for channel equalization for use in one or more cosine modulated filter bank-based multi-carrier communication devices or in one or more wavelet packet modulation-based multi-carrier communication devices, the apparatus being a recursive time- domain channel equalizer comprising a finite impulse response part and an infinite impulse response part.
- the present invention assumes a slowly varying transmission channel and noise.
- the transmission channel is preferably symmetrical.
- the present invention is thus particularly adapted for use over wired networks, such as for example electric power distribution networks.
- the present invention uses a time-domain recursive equalizer to compensate the distortions due to the transmission channel.
- a recursive equalizer is placed before the cosine modulated filter bank or wavelet packet modulation at the receiver.
- the coefficients of the recursive equalizer are determined in such a way that the channel transfer function is compensated by the time- domain equalizer's transfer function.
- the coefficients are first calculated using a training sequence known to the receiver during an initialization procedure and are updated periodically using transmitted pilot symbols.
- the time-domain recursive equalizer has a rational transfer function having poles and zeros to better compensate the transmission channel transfer function.
- Such equalizers are usually avoided in prior art systems because they dramatically amplify the channel noise and decision feedback equalizers are preferably used instead.
- the channel noise amplification is avoided by performing, for data transmissions in both directions, a channel pre-equalization at the sender using the infinite impulse response (MR) part of the time-domain recursive equalizer, the finite impulse response (FIR) part of the equalizer being used at the receiver to reduce the remaining channel distortions.
- MR infinite impulse response
- FIR finite impulse response
- the time-domain recursive equalizer according to the present invention is less complex than the prior art frequency combiners proposed for use in cosine modulated filter bank-based multi-carrier communication devices or in wavelet packet modulation-based multi-carrier communication devices.
- the equalization method according to the present invention allows a near perfect reconstruction of the sent data in the cosine modulated filter bank-based multi-carrier communication devices or in the wavelet packet modulation-based multi-carrier communication devices.
- Near perfect reconstruction means that the carriers are orthogonal before demodulation. Thanks to the equalization method of the present invention, cosine modulated filter bank-based multi-carrier communication devices and/or wavelet packet modulation-based multi-carrier communication devices having intrinsically a better spectral efficiency than other multi-carrier communication devices are made attractive for an implementation in data transmission systems.
- FIG. 1 shows a block diagram of a communication system using prior-art OFDM-based multi-carrier communication devices.
- Fig. 2 is a block diagram during initialization of a data communication system using cosine modulated filter bank-based multi- carrier communication devices or wavelet packet modulation-based multi- carrier communication devices, in accordance with a preferred embodiment of the present invention.
- Fig. 3a is a detailed block diagram of a time-domain recursive equalizer according to an embodiment of the present invention.
- Fig. 3b is a detailed block diagram of a time-domain recursive equalizer according to another embodiment of the present invention.
- Fig. 4 is a block diagram during operation of a data communication system using cosine modulated filter bank-based multi- carrier communication devices or wavelet packet modulation-based multi- carrier communication devices, in accordance with a preferred embodiment of the present invention. Description of the invention
- Fig. 2 shows a block diagram of a communication system with multi-carrier communication devices in accordance with a preferred embodiment of the present invention during an initialization or a training phase.
- a sender 21 of a first communication device sends a known sequence of training symbols 20 to a receiver 24 of a second communication device.
- the training symbols 20 are first converted by a serial to parallel converter 201 and then converted from the frequency domain into the time domain by an inverse transform in a modulator 202.
- the inverse modulation employed in the modulator 202 is preferably inverse cosine modulated filter bank modulation or inverse wavelet packet modulation.
- the output of the sender 21 is a modulated training sequence 22 which is sent over the transmission channel 103 with the channel noise 104.
- the channel output 23 received by the receiver 24 is first fed into a time-domain recursive equalizer 207 having a rational transfer function with poles and zeros.
- the known modulated training sequence 22 which is for example stored in a memory area 211, is simultaneously fed by the receiver 24 into the recursive path of the equalizer 207, as explained below in more details.
- the output 27 of the time-domain equalizer 207 is then fed into the demodulator 209.
- the modulation performed in the demodulator 209 preferably is either a cosine modulated filter bank modulation or a wavelet packet modulation in accordance with the inverse transform used in the modulator 202.
- the parallel output of the demodulator 209 is fed into a parallel to serial converter 210, the output of which is a good estimate 25 of the data 20 sent by the sender 21.
- the time-domain recursive equalizer 207 comprises a finite impulse response (FIR) part 301 and an infinite impulse response (MR) part 304.
- the MR part 304 is fed with a noiseless reference modulated training sequence 22 instead of being recursively fed with the noisy output 27 of the equalizer.
- the coefficients a 0 to a n and bi to b m of the equalizer 207 are preferably determined by a calculator 208 using an error criterion like for instance minimum mean square error (MMSE) in order to minimize the difference between the output 27 of the equalizer 207 and the reference modulated training sequence 22, so as to make the output signal 25 represented on Fig. 2 a good estimate of the sent data 20.
- MMSE minimum mean square error
- Fig. 3b is the block diagram of the time-domain recursive equalizer 207 according to another embodiment of the invention.
- the MR part 304' is realized using a lattice form digital filter.
- the coefficients a 0 to a n and ki to k m are determined as previously explained for the embodiment illustrated in Fig. 3a.
- the advantage of the lattice form digital filter is that it is easily stabilized as its transfer function is always stable as long as the absolute value of all coefficients ki to k m is inferior to 1.
- a communication system is built by connecting at least two inventive multi-carrier communication devices over a transmission channel 103.
- Each communication device preferably comprises a sender 21, a receiver 22 and a hybrid circuit 404.
- the sender 21 and the receiver 22 are connected to the hybrid circuit 404 over which the communication device is connected to the transmission channel 103.
- the communication devices Before sending information data to each other, the communication devices perform an initialization phase as described above.
- the initialization or training phase is preferably performed at least once with each communicating sender-receiver pair.
- Each receiver 21 thus determines all necessary coefficients for an optimal channel equalization.
- the IIR part 304 or 304" is preferably performed in the senders 21 which thus perform a pre-equalization of the channel's transfer function on the signal before transmitting it. This avoids the channel noise 104 to be amplified by the IIR part 304 or 304', as only the FIR part 301 of the equalization is performed on the received signal.
- the coefficients bi to b m or ki to k m determined for the IIR part 304 or 304' by each receiver 24 can be used to tune the IIR part 304 or 304' within the same communication device.
- the coefficients calculated within the receiver 24 are thus preferably transferred to the IIR part 304 of the sender 21 within the same communication device.
- the one skilled in the art will however recognize that it is possible within the frame of the invention to compute the coefficients bi to b m or ki to k m in the receiver of one communication device and send them over the channel 103 to the sender of another communication device for tuning its IIR part.
- the transmission of the coefficients over the channel can even be required, for example if the communication devices only comprise either a receiver or a sender, or if the transmission channel is not symmetrical.
- the transmission channel 103 is preferably assumed to be slowly varying over time.
- the training phase thus doesn't need to be frequently performed in order to keep the equalizer in optimal operating conditions. Only a very small proportion of the communication system's transmission capacities are thus required for training purposes.
- inventive equalization and apparatus as described above are thus particularly adapted to be used over a wired and symmetrical transmission network, such as for example an electrical power distribution network comprising the area between the low-voltage transformer station and the house connection unit and/or the electricity distribution within the house.
- a wired and symmetrical transmission network such as for example an electrical power distribution network comprising the area between the low-voltage transformer station and the house connection unit and/or the electricity distribution within the house.
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Power Engineering (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04726173A EP1649651A1 (en) | 2003-04-08 | 2004-04-07 | Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulation |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03100942 | 2003-04-08 | ||
EP04726173A EP1649651A1 (en) | 2003-04-08 | 2004-04-07 | Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulation |
PCT/EP2004/050486 WO2004091159A1 (en) | 2003-04-08 | 2004-04-07 | Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulation |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1649651A1 true EP1649651A1 (en) | 2006-04-26 |
Family
ID=33155218
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04726173A Withdrawn EP1649651A1 (en) | 2003-04-08 | 2004-04-07 | Method and apparatus for channel equalization in multi-carrier communication devices using discrete cosine modulated filter bank or wavelet packet modulation |
Country Status (2)
Country | Link |
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EP (1) | EP1649651A1 (en) |
WO (1) | WO2004091159A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102196111B (en) * | 2011-04-14 | 2014-05-07 | 西安烽火电子科技有限责任公司 | Short-wave two-path modulator-demodulator |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5636246A (en) | 1994-11-16 | 1997-06-03 | Aware, Inc. | Multicarrier transmission system |
US6526105B1 (en) * | 1998-05-29 | 2003-02-25 | Tellabs, Operations, Inc. | Time domain equalization for discrete multi-tone systems |
US6212229B1 (en) * | 1998-12-16 | 2001-04-03 | General Dynamics Government Systems Corporation | Adaptive pre-emphasis technique |
-
2004
- 2004-04-07 EP EP04726173A patent/EP1649651A1/en not_active Withdrawn
- 2004-04-07 WO PCT/EP2004/050486 patent/WO2004091159A1/en active Application Filing
Non-Patent Citations (1)
Title |
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See references of WO2004091159A1 * |
Also Published As
Publication number | Publication date |
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WO2004091159A1 (en) | 2004-10-21 |
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