CN1574824A - TDS-OFDM receiving device for equalizing channel - Google Patents

TDS-OFDM receiving device for equalizing channel Download PDF

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Publication number
CN1574824A
CN1574824A CNA2004100496427A CN200410049642A CN1574824A CN 1574824 A CN1574824 A CN 1574824A CN A2004100496427 A CNA2004100496427 A CN A2004100496427A CN 200410049642 A CN200410049642 A CN 200410049642A CN 1574824 A CN1574824 A CN 1574824A
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ofdm
tds
unit
time domain
receiving system
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朴义俊
郑晋熙
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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    • 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
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
    • 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
    • H04L25/03082—Theoretical aspects of adaptive time domain methods
    • H04L25/03101—Theory of the Kalman algorithm
    • 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
    • H04L25/03178—Arrangements involving sequence estimation techniques
    • H04L25/03248—Arrangements for operating in conjunction with other apparatus
    • H04L25/03254—Operation with other circuitry for removing intersymbol interference
    • H04L25/03267—Operation with other circuitry for removing intersymbol interference with decision feedback equalisers
    • 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
    • H04L25/03178—Arrangements involving sequence estimation techniques
    • H04L25/03248—Arrangements for operating in conjunction with other apparatus
    • H04L25/03286—Arrangements for operating in conjunction with other apparatus with channel-decoding circuitry
    • 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
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/26546—Demodulators with oversampling

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention relates to a TDS-OFDM receiver with channel equalization through the over-sampling OFDM code elements, comprising a synchronization unit, which is used in the synchronous OFDM broadcasting signal that is received by antenna, downscaled to the baseband and is sampled at the predetermined sampling ratio T0; first sampler, which is used to sample the OFDM broadcasting signals output by the synchronization unit at the predetermined first sampling ratio T1; a time domain equalization unit, which is used to sample the equalized OFDM broadcasting signals output by the time domain equalization unit at the predetermined second sampling ratioT2. Thus, the effects from sampling timing error and code elements timing error are avoided. Furthermore, the distortion in the multi-path is effectively compensated because of the use of over-sampled OFDM broadcasting signals in the equalization.

Description

The time-domain synchronization OFDM receiving system that is used for equalization channel
Technical field
The present invention relates to a kind of TDS-OFDM receiving system.Relate in particular to a kind of TDS-OFDM receiving system, its over-sampling ofdm signal and this signal is input to time-domain equalizer comes compensating distortion.
Background technology
The OFDM scheme will convert predetermined block-based parallel data to the code element row of serial form input, and the code element that will walk abreast is multiplexed to each different sub-carrier frequencies.This OFDM scheme is used multicarrier, and this method with traditional use single carrier is different.In multicarrier, each carrier wave has orthogonality mutually.This orthogonality is meant to be zero characteristic when multiplying each other two carrier waves, this is to use the demand of multicarrier.This OFDM scheme is mainly used fast Fourier transform (FFT) and invert fast fourier transformation (IFFT).Therefore, realize the OFDM scheme based on orthogonality between the carrier wave and FFT.
Ofdm signal comprises multicarrier, and each multicarrier has very little bandwidth.And therefore therefore, entire spectrum is becoming squarely in shape basically,, compares with the situation of using single carrier and to have improved frequency efficiency.In addition, because the waveform of ofdm signal is identical with the waveform of white Gauss noise, ofdm signal has less interference than other broadcasting service such as Phase Alternate Line (PAL) and "systemme electronique couleur avec memoire".
Recently, in order to improve the speed of terrestrial digital television (DTV) transmission transmission system standard, introduced terrestrial digital multimedia broadcasting (DMB-T), it is the transmission standard of a kind of new land DTV.The transmission system of this use DMB-T is also used the TDS-OFDM scheme.The OFDM modulating unit uses 3780 point discrete Fourier inverse transformation/discrete Fourier transform (DFT) (IDFT/DFT) processors.
Yet, in transmission channel, may produce various distorted signals according to channel status.Especially influence signal significantly owing to this distortion of multipath, and this distortion is fatal in digital broadcasting.In order to compensate this distortion, provide equalizer to compensate mistake about transmission channel to receiving terminal.
Fig. 1 is the block diagram of traditional TDS-OFDM receiving system, and this device comprises rf receiver unit (RFRX) 10, analogue-to-digital converters (ADC) 12, lock unit 14, demultiplexer 16, pseudo noise (PN) correlation unit 20, a FFT unit 30, the 2nd FFT unit 40, frequency-domain balancing unit 50 and forward error correction (FEC) unit 60.
RF RX 10 will downconvert to base band via the OFDM broadcast singal that antenna receives, and ADC 12 will become digital signal from the analog signal conversion of RF RX 10.
Lock unit 14 uses as the PN sequence of synchronizing information transmission and carries out symbol timing and Frequency Synchronization.This PN sequence information be used for the ofdm signal that receives from the TDS-OFDM receiving system synchronously and the synchronizing information of channel estimating.Insert this PN sequence before, as described later to protection interval (GI).
Demultiplexer 16 will be cut apart and will be output as PN sequence, GI and OFDM code element from the OFDM broadcast singal that lock unit 14 receives.
PN correlation unit 20 outputs to a FFT unit 30 in order to provide about the information of channel status with the PN correlation between reference signal row and the PN sequence.The one FFT unit 30 is this PN sequence transformation, and it is outputed to frequency-domain balancing unit 50.
To output to the 2nd FFT unit 40 from the OFDM code element of demultiplexer 16 output, and the 2nd FFT unit 40 by FFT with this OFDM symbol transformations, to output to frequency-domain balancing unit 50.
Frequency-domain balancing unit 50 is come the OFDM code element of the balanced conversion that receives from the 2nd FFT unit 40 based on the PN correlation that receives from a FFT unit 30.
FEC unit 60 uses the error-detecting method of the OFDM code element after the suitable equilibrium to detect mistake, and corrects detected mistake.
As mentioned above, traditional TDS-OFDM receiving system uses the PN sequence to estimate channel status, and it is balanced to use the channel status that estimates to come in frequency domain.Yet, when about the information of channel status because distortion and noise component(s) and when inaccurate, equalization function has been worsened.
Summary of the invention
The objective of the invention is to overcome the above problems at least and advantage and following advantage is provided at least.Therefore, the purpose of this invention is to provide a kind of TDS-OFDM receiving system, its over-sampling ofdm signal and be entered into time-domain equalizer and come compensating distortion.
In order to realize above-mentioned purpose of the present invention, a kind of TDS-OFDM receiving system is provided here, comprising: lock unit is used for synchronously receiving, to be down converted to base band and by with predetermined sampling rate T via antenna 0The OFDM broadcast singal with synchronizing information of sampling; First sampler is used for the first predetermined sampling rate T 1Sample from the OFDM broadcast singal of lock unit output; The time domain equalization unit is used for using the synchronizing information OFDM broadcast singal after the aligned sample time domain that comprises from the OFDM broadcast singal of first sampler output; With second sampler, be used for the second predetermined sampling rate T 2The OFDM broadcast singal of sampling after the equilibrium of time domain equalization unit output.
Lock unit uses synchronizing information.This synchronizing information is the PN sequence.
Sampling rate T 1Equation below satisfying T 1 = T 0 N , And N is a natural number.T 2With T 0Identical, and T 0Be
Figure A20041004964200052
Second.The time domain equalization unit is a DFF.This time domain equalization unit comprises: feedforward filter is used for removing the pre-ghost image of the OFDM code element that is included in the OFDM broadcast singal after the sampling of first sampler output; Feedback filter is used to remove the back ghost image from the OFDM code element of first sampler output; And adder unit, be used for addition from wherein having removed the OFDM code element of pre-ghost image and back ghost image, and the value after the addition outputed to the feedback filter and second sampler.
Sampling rate T 1Equation below satisfying T 1 = T 0 N , And N is a natural number.T 2With T 0Identical, and T 0Be Second.
Description of drawings
By describing its exemplary embodiment with reference to the accompanying drawings in detail, above-mentioned purpose of the present invention and other characteristics will become apparent, wherein:
Fig. 1 is the block diagram of traditional TDS-OFDM receiving system;
Fig. 2 is the block diagram according to the TDS-OFDM receiving system of the embodiment of the invention;
Fig. 3 is the block diagram of the time domain equalization unit in the detailed displayed map 2; With
Fig. 4 is used to show the structure of OFDM broadcast singal and the pattern of training technique.
Embodiment
Below, describe embodiments of the invention in detail with reference to accompanying drawing.
Fig. 2 is the block diagram according to the TDS-OFDM receiving system of the embodiment of the invention.With reference to figure 2, this TDS-OFDM receiving system comprises: rf receiver unit (RF RX) 100, analogue-to-digital converters (ADC) 120, lock unit 140, time domain equalization unit 200, fast Fourier transform unit (FFT) 300 and forward error correction unit (FEC) 400.
RF RX 100 will downconvert to base band via the OFDM broadcast singal that antenna receives, and ADC120 is according to the sampling rate T that sets in advance 0Sampling converts digital signal to from the analog signal that RF RX 100 receives.In TDS-OFDM, sampling rate T 0Be Second (sec).
Lock unit 140 uses as the PN sequence of synchronizing information transmission and carries out symbol timing and Frequency Synchronization.
Time domain equalization unit 200 uses the PN sequence to come balanced OFDM broadcast singal, and comprises: first sampler 210, feedforward filter (FFF) 220, feedback filter (FBF) 230, adder unit 240 and second sampler 250.Time domain equalization unit 200 with FFF220 and FBF230 is called DFF (DFE).
Because time domain equalization unit 200 receives the OFDM broadcast singal that has as the structure that shows from lock unit 140 among Fig. 4, so PN sequence, GI and OFDM code element sequentially are input to time domain equalization unit 200.Between PN sequence and OFDM code element, insert GI, to be suppressed at the inter symbol interference (ISI) in the multi-path environment.
When input PN sequence during to time domain balanced unit 200, this time domain equalization unit 200 is operated with training method.Therefore, according to the sampling rate T that in first sampler 210, sets in advance 1The PN sequence of sampling and importing.This sampling rate T 1Equation below satisfying.
[equation 1]
T 1 = T 0 N
In [equation 1], N is a natural number.In this embodiment, N is set to 2.
By according to T 1Come resampling to be input to OFDM broadcast singal in the time domain equalization unit 200, the influence that can offset sample-timing error and symbol timing error.In addition, come equilibrium, can compensate the distortion in multipath more effectively by the OFDM broadcast singal that uses over-sampling.Time domain equalization unit 200 uses according to T 1PN sequence after the sampling is upgraded the tap coefficient of FFF and the tap coefficient of FBF.
As long as GI and OFDM code element are input to time domain equalization unit 200, so just do not upgrade FFF tap coefficient and FBF tap coefficient.When OFDM code element positive input during to time domain balanced unit 200, this OFDM code element is by equilibrium.In this process, time domain equalization unit 200 uses FFF tap coefficient and FBF tap coefficients, and this coefficient is to use and calculates with the PN sequence behind the training method over-sampling.To at length explain the balancing procedure of time domain equalization unit 200 as described above now.
Fig. 3 is the block diagram of the time domain equalization unit 200 in the displayed map 2 at length.With reference to figure 3, FFF200 comprises buffer portion 222, multiplication part 224 and addition section 226, and FBF 230 comprises buffer portion 232, multiplication part 234 and addition section 236.
According to the sampling rate T that in first sampler 210, sets in advance 1Sample from the OFDM code element of lock unit 140 outputs, and output to FFF 220.
FFF 220 removes the influence of the pre-ghost image of each OFDM code element.With reference to figure 3, FFF 220 comprises buffer portion 222, multiplication part 224 and addition section 226.Buffer portion 222 usefulness code elements are that unit stores the OFDM code element in each buffer into the order of importing temporarily.Multiplication part 224 multiplies each other in order to remove pre-ghost image and stores each code element and FFF tap coefficient in each buffer temporarily into.Addition section 226 additions each from wherein removing the value of pre-ghost image in multiplication part 224.
FBF 230 removes the influence of the back ghost image of each OFDM code element.FBF 230 comprises buffer portion 232, multiplication part 234 and addition section 236.Buffer portion 232 usefulness code elements are that unit will store into each buffer from the value of adder unit 240 outputs with the order of importing temporarily.Multiplication part 234 is each code element and the FBF tap coefficient in each buffer that temporarily stores buffer portion 232 into that multiplies each other in order to remove the back ghost image.Addition section 226 additions each from wherein remove the back ghost image value.
Adder unit 240 additions are from wherein removing the value of pre-ghost image and from wherein removed the value of back ghost image at FBF 230, the value after the addition is fed back to FBF 230 and outputs to second sampler 250 at FFF 220.Second sampler, 250 basis and T 0The identical sampling rate T that sets in advance 2Sample OFDM code element after the equilibrium.
Although in this embodiment, this time domain equalization unit 200 has used DFE as an example, also can adopt Kalman's (Kalman) equalizer and data recirculation (recycling) equalizer.
With reference to figure 2, come the OFDM code element of conversion by FFT 300, and output to FEC unit 400 from 250 outputs of second sampler.
The error correction method that these FEC unit 400 uses are set detects and corrects the mistake of the OFDM code element after the conversion.
As understanding,,, can carry out equilibrium by over-sampling OFDM broadcast singal according to the embodiment of the invention from top description.Therefore, can offset the influence of sample-timing error and symbol timing error.In addition, the OFDM broadcast singal by behind the use over-sampling in equilibrium can more effectively compensate the distortion in multipath.
Although show and described the present invention with reference to some embodiment, it should be appreciated by those skilled in the art, do not breaking away under the situation of the spirit and scope that limit by claims of the present invention, can make various changes in form and details.

Claims (9)

1, a kind of TDS-OFDM receiving system comprises:
Lock unit is used for synchronously receiving, to be down converted to base band and by with predetermined sampling rate T via antenna 0The OFDM broadcast singal with synchronizing information of sampling;
First sampler is used for the first predetermined sampling rate T 1Sample from the OFDM broadcast singal of lock unit output;
The time domain equalization unit is used for using the synchronizing information OFDM broadcast singal after the aligned sample time domain that comprises from the OFDM broadcast singal of first sampler output; With
Second sampler is used for the second predetermined sampling rate T 2The OFDM broadcast singal of sampling after the equilibrium of time domain equalization unit output.
2, TDS-OFDM receiving system as claimed in claim 1, wherein, lock unit uses synchronizing information.
3, TDS-OFDM receiving system as claimed in claim 2, wherein, synchronizing information is pseudo noise (PN) sequence.
4, TDS-OFDM receiving system as claimed in claim 1, wherein,
T 1 = T 0 N ,
Wherein N is a natural number.
5, TDS-OFDM receiving system as claimed in claim 1, wherein, T 2With T 0Identical.
6, TDS-OFDM receiving system as claimed in claim 1, wherein, T 0Approximately be Second.
7, TDS-OFDM receiving system as claimed in claim 1, wherein, the time domain equalization unit is DFF (DFE).
8, TDS-OFDM receiving system as claimed in claim 1, wherein, the time domain equalization unit comprises:
Feedforward filter is used for removing the pre-ghost image of the OFDM code element that is included in the OFDM broadcast singal after the sampling of first sampler output;
Feedback filter is used to remove the back ghost image from the OFDM code element of first sampler output; With
Adder unit is used for addition from wherein having removed the OFDM code element of pre-ghost image and back ghost image, and the value after the addition is outputed to the feedback filter and second sampler.
9, TDS-OFDM receiving system as claimed in claim 1, wherein, the time domain equalization unit is a kind of in Kalman's (Kalman) equalizer and data recirculation (recycling) equalizer.
CNA2004100496427A 2003-06-23 2004-06-23 TDS-OFDM receiving device for equalizing channel Pending CN1574824A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101305608B (en) * 2005-11-07 2010-10-13 Lg电子株式会社 Apparatus for receiving a signal of orthogonal frequency division multiplexing

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KR100808949B1 (en) * 2006-08-12 2008-03-04 삼성전자주식회사 Method of channel estimation using linear correlation based Interference Cancellation combined with Dicision-Feedback Equalization and apparatus thereof
KR100837114B1 (en) * 2006-10-30 2008-06-11 지씨티 세미컨덕터 인코포레이티드 Ofdm receiving circuit with multiple demodulation paths using oversampling analog-to-digital converter
KR100850360B1 (en) * 2006-11-17 2008-08-04 한국전자통신연구원 Apparatus and method for transmitting UWB of OFDM system
KR101302267B1 (en) * 2008-04-17 2013-09-02 에릭슨 엘지 주식회사 Apparatus and method for channel estimation using over-sampling in sc-fdma based mobile telecommunication system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101305608B (en) * 2005-11-07 2010-10-13 Lg电子株式会社 Apparatus for receiving a signal of orthogonal frequency division multiplexing

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