EP2289183A2 - Procédé et système d estimation et d égalisation de canal - Google Patents

Procédé et système d estimation et d égalisation de canal

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Publication number
EP2289183A2
EP2289183A2 EP09758531A EP09758531A EP2289183A2 EP 2289183 A2 EP2289183 A2 EP 2289183A2 EP 09758531 A EP09758531 A EP 09758531A EP 09758531 A EP09758531 A EP 09758531A EP 2289183 A2 EP2289183 A2 EP 2289183A2
Authority
EP
European Patent Office
Prior art keywords
signal
channel
impulse response
response value
outputting
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Withdrawn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
EP09758531A
Other languages
German (de)
English (en)
Other versions
EP2289183A4 (fr
Inventor
So Ra Park
Se Bin Im
Hyung Jin Choi
Sung Ik Park
Yong Tae Lee
Jong Soo Lim
Soo In Lee
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.)
Electronics and Telecommunications Research Institute ETRI
Original Assignee
Electronics and Telecommunications Research Institute ETRI
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Application filed by Electronics and Telecommunications Research Institute ETRI filed Critical Electronics and Telecommunications Research Institute ETRI
Publication of EP2289183A2 publication Critical patent/EP2289183A2/fr
Publication of EP2289183A4 publication Critical patent/EP2289183A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/01—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
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • 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
    • H04L25/0202—Channel estimation
    • H04L25/0212—Channel estimation of impulse response
    • 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
    • H04L25/0202—Channel estimation
    • H04L25/022—Channel estimation of frequency response
    • 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
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • 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
    • H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
    • 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
    • H04L25/03292—Arrangements for operating in conjunction with other apparatus with channel estimation circuitry
    • 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
    • H04L25/03891—Spatial equalizers
    • 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
    • H04L27/2602—Signal structure
    • 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
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H04L27/26136—Pilot sequence conveying additional information
    • 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
    • H04L27/2651—Modification of fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators for performance improvement
    • 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
    • H04L27/26524—Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation
    • H04L27/26526—Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
    • 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
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • 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
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference 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
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H04L27/26134—Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain

Definitions

  • the present invention relates to a channel estimation and equalization method and system.
  • the orthogonal frequency division multiplexing (OFDM) system safely provides various multimedia services to a user when a receiver moves. Attention to the OFDM system has increased all over the world because of the merit. Hence, the OFDM system is anticipated to be applicable to various fields such as vehicles, high-fidelity (HiFi) home theaters, and mobile receivers. In Korea, the Ministry of Information and Communication has determined the Eureka-147 digital audio broadcasting (DAB) for the terrestrial DMB (T-DMB) standard in 2002, and the terrestrial digital broadcasting systems have been provided and various types of software have been developed. Accordingly, services started to be provided to users in December 2005.
  • DAB digital audio broadcasting
  • T-DMB terrestrial DMB
  • T-DMB As the domestic commercialization and outreach of the T-DMB service to foreign countries have accelerated, it has become required for the T-DMB system to generate plans for generating comparative advantage over the digital video broadcasting-handheld (DVB-H) system, the media forward link only (MediaFLO) system, or the integrated service digital broadcasting terrestrial (ISDB-T) system that are competitive with the T-DMB system concerning skills and services.
  • DVD-H digital video broadcasting-handheld
  • MediaFLO media forward link only
  • ISDB-T integrated service digital broadcasting terrestrial
  • an AT-DMB transmitter separates a standard-definition (SD) video source into high priority (HP) video signals and low priority (LP) video signals to encode them, and provides them to the receiver through a single T-DMB channel by using a layered modulation skill.
  • SD standard-definition
  • HP high priority
  • LP low priority
  • error protection performance for the high priority video signals and the low priority video signals are realized differently.
  • the conventional T-DMB receiver restores the high priority video signal from the AT-DMB signals transmitted by the transmitter, and uses the quarter video graphics array (QVGA) quality T-DMB service that is similar to the existing quality.
  • the AT-DMB receiver restores the high priority video signals and the low priority video signals included in the AT-DMB signals transmitted by the transmitter to use an SD quality video service.
  • the AT-DMB system may substantially degrade the performance of receiving data signals that are additionally transmitted according to the layered modulation scheme in the real radio channel condition. Also, the signals may be easily distorted by the channel.
  • the present invention has been made in an effort to provide a channel estimation and equalization method and system for increasing data rates by reducing channel estimation errors when a receiver moves at a high speed.
  • An exemplary embodiment of the present invention provides a system for estimating and equalizing a channel of a signal, including: a serial/parallel converter for dividing the signal into a guard interval and an useful data signal, and outputting the signals; a first channel estimator for receiving the guard interval, estimating an impulse response of the channel, and outputting an impulse response value; a channel equalizer for equalizing channel distortion of the useful data signal by using the impulse response value output by the first channel estimator, and outputting an equalized signal; and a second channel estimator for receiving the useful data signal and the equalized signal output by the channel equalizer, estimating a frequency response to the useful data signal, and outputting a frequency response value.
  • Another embodiment of the present invention provides a method for estimating and equalizing a channel of a signal, including: converting the signal into a guard interval and a useful data signal; estimating an initial impulse response value of the channel through the guard interval, and outputting an impulse response value; estimating a frequency response on the channel through the useful data signal, and outputting a frequency response value; correcting the output impulse response value and outputting the impulse response value; and equalizing a channel of the signal based on the corrected impulse response value, and outputting an equalized signal.
  • FIG. 1 shows an AT-DMB system according to an exemplary embodiment of the present invention.
  • FIG. 2 shows a configuration diagram of a transmitting system according to an exemplary embodiment of the present invention.
  • FIG. 3 to FIG. 6 show a constellation according to an exemplary embodiment of the present invention.
  • FIG. 7 and FIG. 8 show a frequency domain pilot subcarrier arrangement according to an exemplary embodiment of the present invention.
  • FIG. 9 shows a configuration diagram of a receiving system according to an exemplary embodiment of the present invention.
  • FIG. 10 shows a time domain subcarrier arrangement according to an exemplary embodiment of the present invention.
  • FIG. 11 shows a frequency domain subcarrier arrangement according to an exemplary embodiment of the present invention.
  • FIG. 12F and FIG. 13 show performance according to symbol positions according to an exemplary embodiment of the present invention.
  • FIG. 14 and FIG. 15 show performance according to the received signal power according to an exemplary embodiment of the present invention.
  • FIG. 16 and FIG. 17 show performance according to the moving speed of a receiver according to an exemplary embodiment of the present invention.
  • FIG. 18 and FIG. 19 show performance according to the number of repeated estimation according to an exemplary embodiment of the present invention.
  • a receiver may indicate a mobile station (MS), a mobile receiver (MR), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), user equipment (UE), and an access receiver (AT), and may include partial or entire functions of the mobile station, the mobile receiver, the subscriber station, the portable subscriber station, the user equipment, and the access receiver.
  • MS mobile station
  • MR mobile receiver
  • MT mobile terminal
  • SS subscriber station
  • PSS portable subscriber station
  • UE user equipment
  • AT access receiver
  • FIG. 1 shows an AT-DMB system according to an exemplary embodiment of the present invention.
  • a transmitting system of an AT-DMB system includes a video/audio source encoder 10, a high priority modulator 20, a low priority modulator 30, a subcarrier mapper 40, an OFDM modulator 50, and a transmitter 60.
  • a receiving system includes a basic quality video receiver 70 and a high quality video receiver 80.
  • the video/audio source encoder 10 encodes an input video source and an audio source into high priority (HP) signals and low priority (LP) signals having digital binary codes.
  • the high priority modulator 20 and the low priority modulator 30 code and multiplex channels of respective bits of the high priority signals and the low priority signals that are encoded and output by the video/audio source encoder 10, and an adder outputs the multiplexed signals as a signal.
  • the output signal is input to the subcarrier mapper 40 to be mapped into a predetermined constellation.
  • the high priority modulator 20 modulates high priority signals by a predetermined data modulation rate.
  • the low priority modulator 30 modulates low priority signals by a predetermined data modulation rate based on the high priority signals.
  • the predetermined data modulation rate will use quadrature phase shift keying (QPSK) constellation as an example, but the embodiment is not restricted thereto.
  • QPSK quadrature phase shift keying
  • the OFDM modulator 50 modulates the mapping signal to OFDM signal.
  • the transmitter 60 amplifies the OFDM signal with appropriate power by up-converting and transmits the signals.
  • the basic quality video receiver 70 of the receiving system receives and demodulates the high priority signals.
  • the high quality video receiver 80 receives the high priority signals and the low priority signals and demodulates them.
  • the transmitting system will now be described with reference to FIG. 2.
  • FIG. 2 shows a configuration diagram of a transmitting system according to an exemplary embodiment of the present invention.
  • the high priority modulator 20 of the transmitting system includes a first channel encoder 21 , a first QPSK mapper 22, a symbol delay unit 23, and a first phase rotator 24, and the low priority modulator 30 includes a second channel encoder 31 , a second QPSK mapper 32, and a second phase rotator 33.
  • the OFDM Modulator 50 includes an inverse fast
  • the transmitter 60 includes an RF unit 61 and a base station antenna 62.
  • the first channel encoder 21 and the second channel encoder 31 respectively receive the high priority signals and the low priority signals having digital binary codes from the video/audio source encoder 10, and encode channels in order to correct transmission errors in preparation for the case in which the digital binary codes may generate transmission errors because of the radio channel.
  • the first channel encoder 21 and the second channel encoder 31 will be described to be included in the high priority modulator 20 and the low priority modulator 30, and are not restricted thereto.
  • the first QPSK mapper 22 QPSK maps the high priority data that are channel encoded by the first channel encoder 21 on four phases.
  • the first phase rotator 24 rotates the phase of the QPSK mapped signal by using a delayed signal for an OFDM symbol interval. Simultaneously, the first phase rotator 24 transmits phase information of the mapped signal to the second phase rotator 33 of the low priority modulator 30.
  • the second QPSK mapper 32 QPSK maps the channel encoded low priority data on four phases.
  • the second phase rotator 33 rotates the phase of the signal mapped by the second QPSK mapper 32 by using phase information transmitted through the first phase rotator 24.
  • the adder 25 adds the output signal of the high priority modulator 20 and the output signal of the low priority modulator 30, and outputs them as a layer modulation signal to the subcarrier mapper 40.
  • the constellations for the output signal of the high priority modulator 20 are shown in FIG. 3 and FIG. 4, and the constellations for the output signal of the low priority modulator 30 are shown in FIG. 5 and FIG. 6.
  • FIG. 3 to FIG. 6 show constellations according to an exemplary embodiment of the present invention.
  • FIG. 3 shows the constellation of the high priority signal of the even OFDM symbol according to an exemplary embodiment of the present invention
  • FIG. 4 shows the constellation of the high priority signal of the odd OFDM symbol
  • FIG. 5 shows the constellation of the low priority signal of the even OFDM symbol according to an exemplary embodiment of the present invention
  • FIG. 6 shows the constellation of the low priority signal of the odd OFDM symbol.
  • the subcarrier mapper 40 shown in FIG. 2 inputs the input layered modulation signal to the IFFT 51 in order to insert the layered modulation signal into a predetermined subcarrier position within the range of N used used
  • Equation 1 the output signal x (m) ( v n ⁇ ) of the
  • Equation 1 Equation 1
  • HP represents the k-th high priority modulation signal of
  • N shows the IFFT dimension
  • ko represents the first subcarrier position that is the reference within the used subcarrier range.
  • u indicates the used subcarrier.
  • the pilot signal generator 52 generates a pilot signal c(n) by passing the constant amplitude zero autocorrelation code (CAZAC) sequence C(k) having the length N c , U sed through the IFFT having the dimension Nc.
  • CAZAC sequence C(k) is expressed in Equation 3
  • the pilot signal generated by the pilot signal generator 52 is expressed in Equation 4. (Equation 3)
  • ⁇ is a factor for controlling power of the pilot signal.
  • p ⁇ so that the average power of the pilot signal may correspond to the average power of the time domain OFDM symbol.
  • the parallel/serial converter 53 receives the pilot signal generated by the pilot signal generator 52 and the OFDM signal by the IFFT 51 and outputs an
  • OFDM signal by performing a parallel/serial conversion process.
  • the RF unit 61 converts the OFDM signal into a radio frequency (RF) signal so that the RF signal may be transmitted to the receiver through the base station antenna 62.
  • RF radio frequency
  • FIG. 7 and FIG. 8 show a frequency domain subcarrier arrangement according to an exemplary embodiment of the present invention.
  • FIG. 7 shows a subcarrier arrangement for a layered modulated data signal according to an exemplary embodiment of the present invention
  • FIG. 8 shows a subcarrier arrangement for a pilot signal generated by a CAZAC sequence according to an exemplary embodiment of the present invention.
  • the pilot signal occupies the same bandwidth as the data signal, but has a greater subcarrier interval than the data signal, and its ratio is set to be N/N c as shown in FIG. 8.
  • the first subcarrier of the data signal is given as k 0 .
  • the first subcarrier of the pilot signal is given as k 0 N c /N in consideration of the reduced number of the subcarriers. For reference, when the subcarrier interval is increased to N/Nc in the frequency domain, the length of the signal is reduced by N c /N that is an inverse number of the subcarrier interval in the time domain.
  • a receiving system according to an exemplary embodiment of the present invention will now be described in detail with reference to FIG. 9.
  • FIG. 9 shows a configuration diagram of a receiver according to an exemplary embodiment of the present invention.
  • the receiving system includes an RF unit 100, a serial/parallel converter 110, a first channel estimator 120, a second channel estimator 200, a first fast Fourier transformer (FFT) 130, a second FFT 140, a high priority demodulator 180, a first parallel/serial converter 190, a channel equalizer 150, a low priority demodulator 160, and a second parallel/serial converter 170.
  • the first channel estimator 120 includes a pilot signal extractor 121 , a channel impulse response estimator 122, and a first impulse response corrector 123.
  • the second channel estimator 200 includes a third FFT 205, a second impulse response corrector 204, an inverse fast Fourier transformer (IFFT) 203, a channel frequency response estimator 202, and a hard decision unit 201.
  • IFFT inverse fast Fourier transformer
  • the RF unit 100 converts the signal received through the base station antenna into a digital signal, and the serial/parallel converter 110 transforms the digital signal into an OFDM symbol that is a parallel layered modulation signal
  • Equation 5 m-th OFDM symbol y v ' is expressed in Equation 5.
  • Equation 5 h (m) (n)
  • Equation 5 h (m) (n)
  • v ' is a time domain impulse response of a channel
  • ⁇ ' is additive white Gaussian noise (AWGN) in the time domain.
  • L h represents a number of delay paths in the multipath channel environment, and ⁇ i is the l-th delay path.
  • serial/parallel converter 110 divides the OFDM symbol into a
  • guard interval GI ⁇ ' and a useful data signal V (IB) ( ⁇ ), (0 ⁇ n ⁇ N) v ' .
  • V (IB) ( ⁇ ) (0 ⁇ n ⁇ N) v ' .
  • OFDM symbol is input to the first channel estimator 120, and the useful data signal is input to the second Fourier transformer 140.
  • the pilot signal extractor 121 in the first channel estimator 120 receives
  • Equation 6 /">(count - N 01 + N C>OI ), (0 ⁇ n ⁇ N c )
  • the channel impulse response estimator 122 estimates an initial impulse
  • Equation 7 Equation 7
  • the first impulse response corrector 123 corrects the error of the estimated impulse response as expressed in Equation 7. Since the process for correcting the impulse response value is performed for each OFDM symbol independently, the superscript (m) representing channel impulse response estimation of the m-th OFDM symbol in the equation developing process will be omitted for ease of description.
  • Equation 8 a position of the impulse response value of the channel having the maximum power is selected as expressed in Equation 8.
  • the superscript [1] represents the number that is selected first in the process for selecting the position having the consecutive maximum power.
  • Equation 8 the initial impulse response value of h( v ⁇ ⁇ ) is corrected with reference to the impulse response value of the first maximum power position as expressed in Equation 9.
  • Equation 10 the initial impulse response value of h( v ⁇ ⁇ ) is corrected with reference to the impulse response value of the first maximum power position as expressed in Equation 9.
  • Equation 10 the initial impulse response value of h( v ⁇ ⁇ ) is corrected with reference to the impulse response value of the first maximum power position as expressed in Equation 9.
  • Equation 10 Equation 10
  • h m ( ⁇ ) c ⁇ ⁇ J represents the first result value of the first error correction.
  • S usec ⁇ subcamer index indicates a used subcarrier index set.
  • the position of the i-th maximum power impulse response value is selected.
  • the position is selected by using Equation 11.
  • Equation 12 The impulse response value of h c ⁇ l ⁇ H v n mmax ) / is corrected with reference to the position of the i-th maximum power impulse response value that is selected by using Equation 11. In this instance, the impulse response value is corrected by using Equation 12. (Equation 12) / a V ⁇ *max "max ) • > V c /
  • the maximum value L c of i is set to be L 0 ⁇ U, and the process for selecting the position of the i-th maximum power impulse response value and
  • the resultant value h c ⁇ lL ⁇ Hn mmax ) that is acquired by repeated performance is a primary error correction value, and secondary error correction is performed through the primary error correction value.
  • ⁇ fi c2 H v ⁇ y represents the first resultant value of the secondary error correction process.
  • the first fast Fourier transformer 130 shown in FIG. 9 receives the useful
  • Equation 16 Equation 16
  • the second fast Fourier transformer 140 receives the useful data signal in the interval of 0 ⁇ n ⁇ N output by the serial/parallel transformer 110, transforms it into a parallel signal, and outputs a frequency domain signal
  • FIG. 9 is input to the high priority demodulator 180, the channel equalizer 150, and the second channel estimator 200.
  • the high priority demodulator 180 demodulates the high priority data bits of the frequency domain signal, and outputs them to the first parallel/serial converter 190.
  • the first parallel/serial converter 190 transforms the demodulated high priority data bits input by the high priority demodulator 180 into serial signals, and outputs them to a source decoder (not shown).
  • the channel equalizer 150 equalizes the frequency domain signal
  • the channel equalizer 150 re-receives a frequency response value of the channel estimated by the second channel estimator 200, and re-equalizes the frequency
  • the superscript * represents a conjugate complex
  • ⁇ 2 is noise power of a frequency domain received signal.
  • the second channel estimator 200 re-estimates the frequency response
  • the receiving without the first channel estimator 120 can use the channel estimate of the OFDM symbol.
  • the hard decision unit 201 in the second channel estimator 200 performs
  • the channel frequency response estimator 202 estimates a frequency response value of a channel by using the hard decision performed signal
  • the inverse fast Fourier transformer 203 receives the frequency response value estimated by the channel frequency response estimator 202,
  • Equation 20 Equation 20
  • the second impulse response corrector 204 receives an impulse
  • the impulse response correction process corresponds to the impulse response value correction process performed by the first impulse response corrector 123.
  • the third Fourier transformer 205 receives an impulse response value
  • Equation 21 An output signal that is a fast Fourier transform result is a frequency response value of a channel, and is expressed in Equation 21. (Equation 21)
  • the low priority demodulator 160 receives an output signal Y « ⁇ m) ( Vk / ⁇ of the channel equalizer 150, demodulates low priority data bits, and outputs resultant data.
  • the data that are output by demodulating the low priority data bits are input to the second parallel/serial converter 170 to be transformed into serial signals, and the serial signals are transmitted to a source decoder (not shown).
  • a subcarrier arrangement according to an exemplary embodiment when the transmitter of the AT-DMB system transmits data signals will now be described with reference to FIG. 10 and FIG. 11.
  • the first channel estimator 120 of FIG. 9 estimates the channel of the signal transmitted by the method of FIG. 10
  • the second channel estimator 200 of FIG. 9 estimates the channel of the signal transmitted by the method of FIG. 11.
  • a time domain subca ⁇ er arrangement will now be described with reference to FIG. 10.
  • FIG. 10 shows a time domain subcarrier arrangement according to an exemplary embodiment of the present invention.
  • a guard interval of an OFDM signal is in the format of reproducing the latter part of the used symbol interval and inserting the latter part thereof into the former part.
  • the guard interval according to the exemplary embodiment of the present invention arranges part of the signal of the existing guard interval at the latter part and arranges a pilot signal at the former part as shown in FIG. 10.
  • the guard interval length N G ⁇ is divided into N G ⁇ (1) and N G i(2), and a pilot signal having the length N 0 and a pilot guard interval having the length N C, G I are arranged in the interval N G ⁇ i-
  • a signal of a general guard interval is arranged in the interval N G I ( 2 ) -
  • the latter part of the pilot signal is reproduced and inserted into the pilot guard interval.
  • the time domain OFDM signal including the guard interval follows Equation 22.
  • FIG. 11 shows a frequency domain subcarrier arrangement according to an exemplary embodiment of the present invention.
  • the general T-DMB system arranges 1 phase reference symbol (PRS) for each group of 76 OFDM symbols. Further, when considering high priority transmission, transmission of a frequency domain pilot signal except the PRS is not allowed. However, when considering additional low priority transmission, it is required to transmit an additional pilot signal together with a phase reference symbol for the purpose of in-phase demodulation through channel estimation.
  • PRS phase reference symbol
  • the pilot signal represents a pilot signal that is transmitted within the used symbol interval of the OFDM signal, and it is different from the time domain pilot signal according to the exemplary embodiment of the present invention inserted into the guard interval.
  • the signal including a phase reference symbol and a layered modulated data signal is controlled to be transmitted.
  • FIG. 11 shows the same structure of the existing transmission signal exclusively for high priority. However, when the low priority signal is transmitted, no additional pilot signal is transmitted within the used symbol interval.
  • Channel estimation performance according to an exemplary embodiment of the present invention will now be described with reference to FIG. 12 to FIG. 19.
  • a simulation is performed by recording statistical performance numbers repeatedly in the condition of the random multi-path Rayleigh fading channel and white Gaussian noise.
  • the radio channel model is based on the COST 207 typical urban (TU), and expresses the radio channel condition in the real urban environment.
  • Each performance estimation is based on the symbol error rate (SER) of the high priority and the low priority, and it is assumed that the receiver is perfectly synchronized since it is for checking channel estimation performance.
  • SER symbol error rate
  • CE Proposed channel estimation
  • CE1 channel estimation method using a time domain pilot signal according to an exemplary embodiment of the present invention.
  • CE2 channel estimation method using a frequency domain hard decision signal according to an exemplary embodiment of the present invention.
  • CE3 channel estimation method using a time domain pilot signal and a frequency domain hard decision signal according to an exemplary embodiment of the present invention.
  • Ideal CE ideal channel estimation method.
  • FIG. 12, FIG. 13, FIG. 14, and FIG. 15 show graphs for comparing performance between the exemplary embodiment of the present invention and the prior art assuming that the receiver moves at the speed of 60km/h.
  • the number of repeatedly estimating Prop. CE2 and Prop. CE3 will be given as 1 , and it is not restricted thereto.
  • FIG. 12 and FIG. 13 show performance for respective symbol positions according to an exemplary embodiment of the present invention.
  • FIG. 12 shows a symbol error rate of the high priority according to an exemplary embodiment of the present invention
  • FIG. 13 shows a symbol error rate of the low priority.
  • the channel estimation method according to the exemplary embodiment of the present invention, the high priority and the low priority have no symbol error rate change with respect to time. Also, the channel estimation generates performance near Ideal CE in the order of Prop. CE3, Prop. CE2, and
  • FIG. 14 and FIG. 15 show performance according to the received signal power according to an exemplary embodiment of the present invention.
  • FIG. 14 shows a symbol error rate of the high priority
  • FIG. 15 shows a symbol error rate of the low priority.
  • the in-phase demodulation method When the channel estimation error is less, the in-phase demodulation method generally outperforms the differential in-phase demodulation method. However, when the high priority symbol error rate of the in-phase demodulation method is greater than that of the differential in-phase demodulation method, degradation may occur because the DDCE depending on the hard decision error has a large estimation error and is not adaptive to the channel change caused by the OFDM symbol position.
  • FIG. 16 and FIG. 17 show performance according to the moving speed of a receiver according to an exemplary embodiment of the present invention.
  • the number of repeatedly estimating Prop. CE2 and Prop. CE3 is given as 1 , but it is not restricted thereto.
  • FIG. 16 shows a symbol error rate of the high priority
  • FIG. 17 shows a symbol error rate of the low priority.
  • the change rate of the channel is also increased, and channel estimation performance and demodulation performance are degraded.
  • FIG. 18 and FIG. 19 show performance according to the number of repeated estimations according to an exemplary embodiment of the present invention.
  • FIG. 18 shows a symbol error rate of the high priority
  • FIG. 19 shows a symbol error rate of the low priority.
  • Prop. CE2 and Prop. CE3 including repeated estimation improve demodulation performance as the number of repetitions is increased, and the demodulation performance reaches a predetermined level of performance over a predetermined repeated number.
  • Prop. CE2 reaches stable performance when the repeated number becomes greater than 6 under the condition in which the receiver moves at the speed of 180km/h.
  • Prop. CE3 generates excellent performance through at least 2 repeated numbers.
  • the channel estimation method solves the performance degradation caused by the receiver's moving speed by increasing the number of repeatedly estimating the channel.
  • a channel estimation error is reduced by inserting a pilot signal into a guard interval of an OFDM symbol, and estimating the channel by using a sequence included in the pilot signal.
  • performance improvement in the fast moving object speed condition is substantial, and the maximum performance can be generated when linked with channel estimation using a time domain pilot signal.
  • the above-described embodiments can be realized through a program for realizing functions corresponding to the configuration of the embodiments or a recording medium for recording the program in addition to through the above-described device and/or method, which is easily realized by a person skilled in the art.

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Abstract

La présente invention concerne un procédé et un système d’estimation et d’égalisation de canal. Le procédé comprend l’introduction d’un signal pilote dans le domaine temporel dans un intervalle de garde, l’utilisation d’un signal de décision stricte dans le domaine fréquentiel pour estimer une réponse en fréquence du canal, et l’égalisation d’une distorsion de canal radio grâce à la valeur du canal estimé.
EP09758531.9A 2008-06-04 2009-06-04 Procédé et système d estimation et d égalisation de canal Withdrawn EP2289183A4 (fr)

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PCT/KR2009/002991 WO2009148278A2 (fr) 2008-06-04 2009-06-04 Procédé et système d’estimation et d’égalisation de canal

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