WO2004100413A1 - 復調装置及び復調方法 - Google Patents
復調装置及び復調方法 Download PDFInfo
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- WO2004100413A1 WO2004100413A1 PCT/JP2003/016298 JP0316298W WO2004100413A1 WO 2004100413 A1 WO2004100413 A1 WO 2004100413A1 JP 0316298 W JP0316298 W JP 0316298W WO 2004100413 A1 WO2004100413 A1 WO 2004100413A1
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- 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
- H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
- H04L25/0232—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals
- H04L25/0234—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals by non-linear interpolation
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- 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
- H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
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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
- H04L27/2655—Synchronisation arrangements
- H04L27/2662—Symbol synchronisation
- H04L27/2665—Fine synchronisation, e.g. by positioning the FFT window
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- 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
- H04L25/0216—Channel estimation of impulse response with estimation of channel length
-
- 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
- H04L27/2655—Synchronisation arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
Definitions
- the present invention relates to a demodulation apparatus or a demodulation method for an orthogonal frequency division multiplexing signal (hereinafter, also referred to as an OFDM (Orthogonal Frequency Division Multiplexing) signal).
- OFDM Orthogonal Frequency Division Multiplexing
- a conventional 0 FDM signal demodulation device demodulates a 0 FDM signal as follows.
- the demodulation device obtains a Fourier transform signal by Fourier-transforming the received OFDM signal with a Fourier transform circuit. Further, a pilot signal synchronizing with the Fourier transform signal is generated by a pilot signal generation circuit.
- the Fourier transform signal is divided by a pilot signal in a divider, whereby a transmission path characteristic corresponding to the pilot signal is calculated.
- the delay time calculation circuit calculates the maximum delay time in the delayed wave component in the received 0 FDM signal.
- the Doppler frequency calculation circuit calculates the magnitude of the transmission path characteristic due to time variation based on the OFDM signal.
- the demodulator fills the transmission path characteristic output from the divider with a variable band filter based on the calculation result of the delay time calculation circuit and the calculation result of the Doppler frequency calculation circuit, and calculates the transmission path characteristic for all subcarrier components. Is calculated. Further, a demodulated signal is obtained by dividing the free-transformed signal by the output from the band variable filter.
- Patent Document 1 Japanese Patent Application Laid-Open No. H10-752226
- the conventional OFDM signal demodulator cannot provide a sufficient noise suppression effect, and the error rate obtained after demodulating the OFDM signal cannot be reduced sufficiently. Disclosure of the invention
- the present invention has been made in order to solve the above-described problems, and uses an estimated delay profile (refers to information (delay time, power value, etc.) corresponding to a delay wave in a multipath environment).
- an estimated delay profile refers to information (delay time, power value, etc.) corresponding to a delay wave in a multipath environment.
- An aspect of the OFDM signal demodulation device is a Fourier transform unit that Fourier transforms a received OFDM signal and outputs a subcarrier component obtained as a result of the Fourier transform, and a Fourier transform unit that is output from the Fourier transform unit.
- a pilot signal extraction unit that extracts a pilot signal included in the subcarrier component, a known signal generation unit that generates and outputs a known signal corresponding to the pilot signal, A first division for calculating a transmission path characteristic corresponding to the pilot signal by dividing the pilot signal output from the pilot signal extraction unit by the known signal output from the known signal generation unit And estimating a delay profile based on the transmission path characteristics of the pilot signal output from the first divider, and corresponding to a maximum delay time in the delay profile.
- a delay profile estimating unit that outputs a signal and a signal corresponding to a minimum delay time in the delay profile; and a transmission path characteristic of the pilot signal output from the first division unit in a time direction and a frequency direction.
- An interpolation filter that performs interpolation and outputs a channel characteristic corresponding to the subcarrier component, and a signal corresponding to the minimum delay time output from the delay profile estimating unit and the 0 FDM signal.
- a timing synchronizing unit that outputs a timing signal for controlling the timing of performing the Fourier transform in the Fourier transform unit; and the subcarrier component output from the Fourier transform unit is output from the interpolation filter unit.
- a second divider that divides by a transmission path characteristic corresponding to the obtained subcarrier component and outputs a demodulated signal
- the Fourier transform unit performs the Fourier transform in accordance with the timing signal
- the interpolation filter unit determines a frequency within a frequency used for interpolation in the frequency direction based on a signal corresponding to the maximum delay time. Insertion of the evening A passband is set, and a frequency band of a transmission path characteristic corresponding to the subcarrier component is limited and output.
- the demodulation device According to the aspect of the demodulation device according to the present invention, it is possible to reduce the deterioration of reception performance due to unnecessary noise components passing through the interpolation filter. Further, according to the aspect of the demodulation device according to the present invention, since the delay profile is estimated using the pilot signal after the Fourier transform, there is an effect that the delay profile can be accurately estimated.
- FIG. 1 is a block diagram showing a configuration example of the demodulation device according to Embodiment 1 of the present invention.
- FIG. 2 is a layout diagram of a pilot signal according to Embodiment 1 of the present invention.
- FIG. 3 is a diagram illustrating a timing and a delay time at which Fourier transform is performed in the demodulation device according to Embodiment 1 of the present invention.
- FIG. 4 is a block diagram showing a configuration example of the first delay profile estimating section according to Embodiment 1 of the present invention.
- FIG. 5 is a block diagram showing a configuration example of a first evening timing synchronization section according to Embodiment 1 of the present invention.
- FIG. 6 is a block diagram showing a configuration example of the first evening synchronization section according to Embodiment 1 of the present invention.
- FIG. 7 is a block diagram showing a configuration example of a demodulation device according to Embodiment 2 of the present invention.
- FIG. 8 is a block diagram showing a configuration example of a demodulation device according to Embodiment 3 of the present invention.
- FIG. 9 is a diagram for explaining the timing and the delay time at which the Fourier transform is performed in the demodulation device according to Embodiment 3 of the present invention.
- FIG. 10 is a block diagram illustrating a configuration example of a demodulation device according to Embodiment 4 of the present invention.
- FIG. 11 is a schematic diagram showing the evening that performs Fourier transform in the demodulation device according to Embodiment 4 of the present invention.
- FIG. 12 is a schematic diagram showing a delay profile in the demodulation devices according to Embodiments 1 and 4 of the present invention.
- transmission data is modulated and transmitted by a transmission device using a plurality of carriers (hereinafter, also referred to as “subcarrier components”) whose frequencies are orthogonal to each other, and the transmission data is received and demodulated by a reception device.
- subcarrier components a plurality of carriers whose frequencies are orthogonal to each other
- the transmitting device allocates transmission data to signal point constellations according to the modulation method of each subcarrier component.
- an inverse Fourier transform is performed on each of the subcarrier components, and a plurality of subcarrier components having mutually orthogonal frequencies are multiplexed to generate a signal.
- a part of the tail of the multiplexed signal (multiplexed signal) is added to the beginning of the multiplexed signal as a guard interval.
- the multiplexed signal to which the guard section is added is frequency-converted into a predetermined frequency band and transmitted.
- the receiving apparatus frequency-converts the received OFDM signal into a predetermined frequency band, specifies the position of the guard section, and establishes synchronization.
- Fourier transform is performed on the symbol to calculate each subcarrier component, and demodulate the subcarrier component to transmit the symbol. Play overnight.
- the demodulation of the subcarrier component is performed by calculating the amount of change in amplitude and phase in the subcarrier component, and reproducing the signal point arrangement at the time of transmission based on the calculation result.
- a method of transmitting a known signal (pilot signal), which is a reference for calculating the amount of change, using a specific subcarrier component is widely used to facilitate calculation of the amount of change in amplitude and phase.
- pilot signal which is a reference for calculating the amount of change
- a specific subcarrier component is widely used to facilitate calculation of the amount of change in amplitude and phase.
- a pilot signal is periodically inserted every 12 subcarrier components in the frequency direction and every 4 symbols in the time direction.
- the receiver calculates the amplitude and phase changes based on the pilot signal and demodulates the subcarrier component.
- the pilot signal In the terrestrial digital TV broadcasting system in Japan, the pilot signal is referred to as a skid and pilot signal.
- the pilot signal inserted into the OFDM signal in the transmitting device is referred to as a transmitting pilot signal
- the pilot signal in the 0 FDM signal received by the receiving device is referred to as a receiving pilot signal. Signal.
- FIG. 1 is a block diagram showing a configuration of the demodulation device according to the present embodiment.
- a Fourier transform unit 1 receives a signal obtained by frequency-converting a received OFDM signal into a predetermined signal band (hereinafter, also referred to as “S 1”) from a first timing synchronization unit 2 described later.
- the Fourier transform is performed based on the timing signal, and the subcarrier components included in S 1 are output to the pilot extraction unit 3 and the first delay adjustment unit 9.
- Pilot extraction section 3 extracts a received pilot signal included in the subcarrier component.
- the transmission pilot signal inserted into the OFDM signal in the transmission device is set in advance as a known signal, and thus, in the demodulation device, the transmission pilot signal and the reception pilot signal, which are the known signals, are transmitted.
- the channel characteristics corresponding to the received pilot signal can be calculated.
- the known signal generation unit 4 generates and outputs a transmission pilot signal at a timing synchronized with the output of the pilot extraction unit 3, and the first division unit 5 extracts the pilot pilot signal.
- the transmission path characteristics corresponding to each reception pilot signal are calculated, and The characteristics are output to the time interpolation filter section 6 and the first delay profile estimation section 7 in the interpolation filter section 18.
- the channel characteristics calculated by the first divider 5 can be obtained only for the received pilot signal. Interpolation processing is required. Hereinafter, the necessity of the interpolation processing will be specifically described.
- Figure 2 shows the arrangement of pilot signals in the 0 FDM signal used for the digital terrestrial TV broadcasting system in Japan.
- the horizontal direction is the frequency direction
- the vertical direction indicates the time direction, with black circles representing pilot signals and white circles representing subcarrier components other than pilot signals.
- the portion surrounded by the solid line represents the k-th subcarrier
- the portion surrounded by the broken line represents the i-th symbol
- the portion between the solid line and the portion surrounded by the broken line intersects.
- the pilot signal is inserted every 12 subcarrier components in the frequency direction and every 4 symbols in the time direction. Therefore, in order to calculate the channel characteristics for all subcarrier components from the channel characteristics calculated based on the pilot signal, interpolation in the time direction and the frequency direction is generally required.
- the time interpolation filter unit 6 performs a time-direction interpolation process of the interpolation process on the transmission path characteristics corresponding to the received pilot signal output from the first division unit 5.
- the channel characteristics corresponding to the received pilot signal are interpolated in the time direction to obtain the channel characteristics corresponding to each of the subcarrier frequency components including the pilot signal. Is obtained.
- the time interpolation filter section 6 outputs the result of performing the interpolation process in the time direction to the frequency interpolation filter section 8.
- the interpolation processing in the frequency direction is performed in the frequency interpolation filter section 8.
- the filter characteristics of the in-frequency / fill filter section 8 it is sufficient if there is a pass band through which the arriving wave component passes, and if the pass band is unnecessarily wide, unnecessary noise components are also filled. , The demodulation performance is degraded. In order to prevent such a deterioration in demodulation performance, it is necessary to minimize the pass band of the inner filter in the frequency direction.
- the Fourier transform unit 2 performs the Fourier transform.
- synchronization timing it is effective to perform both optimization of the timing (hereinafter, referred to as synchronization timing) and optimization of the pass band of the frequency interpolation filter used for the interpolation in the frequency direction.
- the optimization of the synchronization timing is performed based on the symbol position of the arriving wave arriving first before the receiving apparatus and the time difference between the symbol position of the arriving wave arriving with the latest delay and the synchronization timing. be able to.
- the pass band optimization of the interpolation filter is performed when the arriving wave having the largest time difference from the synchronization timing and the synchronization timing is delayed. It can be done on the basis of time. Therefore, the first delay profile estimating unit 7 generates a signal necessary for the optimization.
- the amplitude and phase of each subcarrier component output from the Fourier transform unit 1 depends not only on the multipath in the transmission path, the phase noise in the receiver, the residual frequency error, but also on the timing at which the Fourier transform is performed. .
- FIG. 3 is an explanatory diagram illustrating the synchronization evening and the delay time.
- two arriving waves having different arrival times to the receiver (the time required for the signal transmitted from the transmitter to arrive at the receiver (received)). Assume that it was received.
- a signal obtained by adding each arriving wave becomes a received wave, and therefore Fourier transform is performed at a timing such that interference between adjacent symbols (hereinafter, also referred to as “intersymbol interference”) does not occur. Need to do. Therefore, first, the timing for performing the Fourier transform, that is, the setting of the synchronization timing will be described with reference to FIG.
- FIG. 3 (a) shows a state in which the arriving wave 1 and the arriving wave 2 composed of the guard interval and the i-th symbol are received at different arrival times.
- the received wave is shown in FIG. 3 (a) as a signal to which the arriving wave 1 and the arriving wave 2 are added.
- the shaded portions before and after are portions where intersymbol interference occurs. Therefore, for example, a data section, a data section 1, a data section 2 and a data section 1 shown in Fig. 3 (a) are used to perform a Fourier transform without interfering with adjacent symbols. It becomes 3.
- the length of each of the de-evening sections 1, 2, and 3 is the symbol length before the guard section is added, and the starting point of the section is determined by synchronous evening.
- the synchronization timing is a boundary where no inter-symbol interference occurs between the (i-1) th symbol and the i-th symbol in the received wave.
- the end of the guard interval in incoming wave 1 is used as the synchronization timing.
- the end of this de-intersection 3 is located on the boundary where no inter-symbol interference occurs between the (i + 1) -th symbol and the i-th symbol in the received wave.
- the synchronization timing corresponding to Day 2 It is provided between the synchronization timing corresponding to the data section 1 and the synchronization timing corresponding to the data section 3.
- the synchronization timing is not uniquely determined, and may be within the time range depending on the arrival time difference of the arriving waves under the condition that no intersymbol interference occurs. Accordingly, for example, in FIG. 3A, the synchronization timing may be provided anywhere between the synchronization timing of the data section 1 and the synchronization timing of the data section 3.
- Fig. 3 (b) shows the delay profile corresponding to the signal obtained by Fourier transforming the data included in the data overnight section 1.
- Figure 3 (c) shows the delay profile corresponding to the signal obtained by performing the Fourier transform on the data included in the data overnight section 2.
- Figure 3 (d) shows the delay profile corresponding to the signal obtained by Fourier-transforming the data included in the data section 3.
- the horizontal axis is the delay corresponding to the end of the guard interval of each arriving wave with respect to the start point of the de-intersection performing Fourier transform, that is, the start position of the i-th symbol.
- the vertical axis represents the power corresponding to each arriving wave.
- the delay profile refers to information (delay time, power value, etc.) corresponding to a delayed wave in a multipath environment.
- the output of the Fourier transform unit 1 from the transmitting apparatus is output from the transmitting apparatus.
- the delay time and the received power corresponding to the received signal that has passed through the transmission path up to are treated as the delay profile.
- the difference a between the synchronization timing corresponding to data section 1 and the end of the guard section in arriving wave 1 is the delay time with respect to the synchronization timing of arriving wave 1, and the spectrum of arriving wave 1 is Appears at delay time a.
- the difference b between the synchronization timing corresponding to the de-intersection 2 and the end of the guard interval in the arriving wave 1 is the delay time of the arriving wave 1 with respect to the synchronization timing. The spectrum of appears at the position of the delay time b.
- the spectrum of the arriving wave 1 is located at the position of the delay time 0 and the spectrum of the arriving wave 2 is The vector appears at a position (t in the figure) separated by an amount corresponding to the arrival time difference of the arriving waves.
- the spectrum of the arriving wave 2 appears at a position apart from the spectrum of the arriving wave 1 by t.
- the first delay profile estimating unit 7 determines, based on the transmission path characteristics output from the first division unit 5, a transmission path until a signal corresponding to data transmitted from the transmitting device reaches the output of the Fourier transform unit 1. , And calculates a signal necessary for the optimization based on the delay time versus the received power.
- FIG. 4 is a block diagram showing a configuration of first delay profile estimating section 7 according to the present embodiment.
- the signal sorting unit 71 arranges the transmission path characteristics of the pilot signals output from the first division unit 5 in the order of higher or lower frequencies. However, if the arrangement of the pilot signal is offset for each symbol as shown in the figure, the frequency of the received pilot signal changes depending on the received symbol. Therefore, in such a case, the pilot signal of the symbol received before the current received symbol is also used, so that the frequency of the received pilot signal does not change at the output of signal sorting section 71. For example, when pilot signals are arranged as shown in Fig. 2, the pilot signals for the past 4 symbols including the currently received symbols are sorted.
- the inverse Fourier transform unit 72 performs an inverse Fourier transform on the transmission path characteristics corresponding to the pilot signals arranged in descending order of frequency or in descending order of frequency, and outputs a signal corresponding to the result of the inverse Fourier transform. Is output to the relative level calculator 73.
- the relative level calculator 73 calculates the amplitude or the square value of the amplitude of the signal output from the inverse Fourier transformer 72, that is, the signal corresponding to the transmission path characteristic of the Pipit signal. The result of the calculation is output to the first arriving wave determination unit 74.
- the output of the relative level calculator 73 that is, the amplitude or the square of the amplitude corresponds to the delay time versus the received power in the delay profile.
- the first arriving wave determination unit 74 determines a component whose amplitude or the square value of the amplitude is larger than a predetermined threshold value as a component corresponding to the arriving wave, and determines the component corresponding to the arriving wave.
- the relative time difference between the position on the time axis where the component exists on the time axis and the synchronization timing is output as a delay time to the maximum delay time calculation unit 75 and the synchronization timing offset calculation unit 76.
- the most preceded arriving wave is It is detected as an incoming wave with a small delay time.
- the first embodiment if there is an incoming wave whose delay time is obtained as a negative value, This means that inter-symbol interference has occurred.
- the maximum delay time calculation unit 75 determines the arriving wave component having the longest delay time among the delay times output from the first arriving wave determination unit 74, and determines the signal corresponding to the delay time (hereinafter referred to as the ⁇ filter ''). (Also called “evening band control signal”) to the frequency interpolation filter unit 8. Further, the synchronization timing offset calculation unit 76 determines the arrival wave component having the smallest delay time from among the delay times output from the first arrival wave determination unit 74, and outputs a signal (corresponding to the delay time) Hereinafter, also referred to as “timing offset adjustment signal”) to the first timing base 2.
- the relationship between the delay time and the magnitude (power value, current value, voltage value, etc.) of the fill band control signal or the magnitude of the timing offset adjustment signal with the delay time can be set to be, for example, a proportional relationship.
- the intra-frequency filter section 8 corresponds to each subcarrier component of the same frequency, which has been interpolated in the time direction in the intra-filter section 6 based on the input filter band control signal. For the transmission path characteristics, select the interpolation filter with the narrowest passband among the filters necessary and sufficient for the arriving wave corresponding to the maximum delay time to pass. Then, based on the selected internal filter, internal processing in the frequency direction is performed.
- the transmission path characteristics for all subcarrier components can be obtained by the interpolation processing in the time-in-frequency filter section 6 and the frequency interpolation filter section 8.
- it can be constituted by a mouth-to-pass filter that passes through low frequencies.
- the first evening synchronization section 2 generates information corresponding to the timing for performing the Fourier transform according to the timing offset adjustment signal output from S1 and the synchronization timing offset calculation section 76, A signal corresponding to the information is output to the Fourier transform unit 1 as a timing signal.
- FIG. 5 is a block diagram showing the configuration of the first evening synchronization section 2 according to the present embodiment.
- the first timing synchronization unit 2 utilizes the fact that the guard interval is a copy of a predetermined interval from the end of the effective symbol included in the received signal, and uses the guard timing to maximize the autocorrelation of the received signal. By detecting the synchronization timing Play the position of the ring.
- the S 1 is input to the effective symbol length delay unit 21 in the first timing base 2.
- the effective symbol length delay unit 21 delays by the data section length for performing the Fourier transform and outputs the result to the complex multiplication unit 22.
- the complex multiplication unit 22 performs a complex multiplication of S 1 and a complex conjugate of the output of the effective symbol length delay unit 21, and outputs a complex signal corresponding to the complex multiplication to the moving average calculation unit 23 .
- the moving average calculation unit 23 calculates a moving average value of a predetermined section length for the input complex signal, and outputs the result of the calculation to the maximum correlation position detection unit 24.
- the predetermined section length for example, a guard section length can be set.
- the maximum correlation position detection unit 24 detects the position where the signal amplitude is largest in the output of the moving average calculation unit 23, and based on the result, performs the Fourier transform, that is, the timing corresponding to the synchronization timing.
- the first timing information (hereinafter, also referred to as “first timing signal”) is generated and output to the timing offset adjusting unit 25.
- the evening timing offset adjusting section 25 gives an offset to the first timing signal based on the timing offset adjusting signal output from the first delay profile estimating section, and outputs the evening timing signal.
- the first timing signal is adjusted by the timing offset adjustment unit 25 under the constraint that intersymbol interference does not occur, and This is performed so that the delay time is minimized. Therefore, the timing offset adjustment signal may be a signal proportional to the delay time of the incoming wave component having the shortest delay time.
- the offset is a correction amount that cancels out the deviation when the first timing signal that can be arbitrarily set as described above deviates from the set position.
- Giving the offset to the first timing signal means to return the synchronization timing to a set position by moving the synchronization timing on a time axis so as to cancel the deviation.
- the shift in the synchronization timing mainly occurs due to multipath fuzzing, while the subcarrier component output from the Fourier transform unit 1 is frequency-interpolated from the subcarrier component and the pilot extraction unit 3.
- the signal corresponding to the subcarrier component is delayed by a predetermined time in the first delay adjusting unit 9 so as to be input to the second dividing unit 10 at the same time, and then output to the second dividing unit 10. Is done.
- the second division unit 10 divides each subcarrier component delayed by the first delay adjustment unit 9 by a transmission path characteristic corresponding to the subcarrier component output from the frequency interpolation filter unit 8, and Demodulate carrier components. Finally, the data reproducing unit 11 reproduces the transmission data from the signal point arrangement of the subcarrier components demodulated by the second dividing unit 10 and outputs the reproduced data (S 2).
- the first arriving wave determining unit 74 determines an incoming wave
- a predetermined threshold value and the amplitude or amplitude of the inverse Fourier transform output are used.
- the amplitude or the square of the amplitude of each transmission line characteristic having the highest level is used as a reference.
- the incoming wave may be determined using a value smaller by a predetermined level than the threshold as a threshold.
- the amplitude or the square of the amplitude of each transmission line characteristic having the lowest level among the outputs of the relative level calculator 73 is used as a reference, and a value larger than this reference value by a predetermined level as a threshold is used as an incoming wave. May be determined.
- the first arriving wave determining unit 74 determines an incoming wave
- the inverse Fourier transform which is the output of the relative level calculating unit 73
- the incoming wave is determined using the output amplitude or the square value of the amplitude as it is, the amplitude or the square value of the amplitude output from the relative level calculation unit 73 is a predetermined number of symbols per component.
- the first arriving wave determination unit 74 may determine the arriving wave based on the minute averaging and the result.
- the amplitude or the squared value of the amplitude output from the relative level calculator 73 is averaged for a predetermined number of symbols for each component, and when the carrier-to-noise power ratio of the subcarrier component is larger than the predetermined value, The arriving wave is judged by the first arriving wave judgment unit 74 based on the result before averaging, and if the carrier-to-noise power ratio is small, the first arriving wave is judged based on the result after averaging.
- the unit 74 may be configured to determine an incoming wave.
- the first timing synchronization section 2 can be configured as shown in FIG. sand That is, the autocorrelation of S1 is calculated in the autocorrelation calculation unit 26, and a signal corresponding to the result of the calculation is output to the correlation maximum position detection unit 24 to detect the position where the autocorrelation is the largest.
- the first timing signal may be generated based on the result.
- the demodulation device of the first embodiment it is possible to control the frequency interpolation filter band while adjusting the synchronization timing for performing the Fourier transform based on the estimated delay profile.
- the passband of the interpolation filter in the frequency direction can be minimized. Therefore, it is possible to reduce the deterioration of reception performance due to unnecessary noise components passing through the inner filter.
- the delay profile is estimated using the pilot signal after the Fourier transform, the delay profile can be estimated with high accuracy.
- the delay profile is estimated from the transmission path characteristics corresponding to the pilot signal output from the first divider 5.
- the delay profile corresponds to the pilot signal.
- the delay profile is estimated based on the channel characteristics obtained by interpolating the channel characteristics in the time direction.
- FIG. 7 is a block diagram showing a configuration of the demodulation device according to the present embodiment.
- the Fourier transform unit 1, the first timing synchronization unit 2, the pilot extraction unit 3, the known signal generation unit 4, the first division unit 5, the time interpolation filter unit 6, and the frequency filter unit Unit 8, first delay adjusting unit 9, second dividing unit 10, and data reproducing unit 11 have the same configuration as the demodulating unit in the first embodiment.
- the same reference numerals as those of the apparatus are added, and the detailed description is omitted.
- the demodulation device is provided with second delay profile estimating section 12 and is not provided with first delay profile estimating section 7 according to the first embodiment. Then, the second delay profile estimating unit 12 estimates the delay profile based on the output from the time interpolation filter unit 6 instead of the output from the first dividing unit 5, and thus estimates the first delay profile file. Part 7 is different. However, the configuration of the second delay profile estimator 12 is the same as the configuration of the first delay profile estimator 7 shown in FIG. In addition, the configuration of the second delay profile estimating unit 12 will be described using the codes shown in parentheses in FIG.
- the calculation of the delay profile based on the channel characteristics that have not been interpolated in the time direction is performed for every four symbols including the pilot signal arranged in the time direction in FIG. Therefore, if the transmission path characteristics change between the four symbols, the calculated delay profile includes an error based on the change.
- the demodulation apparatus since the delay profile is estimated based on the transmission path characteristics that have already been subjected to inversion in the time direction, the demodulation apparatus follows changes in the transmission path characteristics in the time direction. This makes it possible to increase the accuracy of the calculated delay profile. As a result, the passband of the frequency direction interpolation filter can be controlled with higher accuracy.
- the channel characteristics output from the time interpolation filter unit 6 are input to the signal sorting unit 121 in the second delay profile estimating unit 12. Then, the signal sorting unit 122 arranges the transmission path characteristics output from the time interpolation filter unit 6 in the order of higher or lower frequencies and outputs the same to the inverse Fourier transform unit 122.
- the inverse Fourier transform unit 122 performs an inverse Fourier transform on the transmission path characteristics output from the signal sorting unit 121, and converts a signal corresponding to the result of the inverse Fourier transform into a relative level calculation unit 122. Output to 3.
- the relative level calculator 123 calculates the amplitude or the square of the amplitude of the signal corresponding to each subcarrier component based on the signal output from the inverse Fourier transformer 122, and calculates the result of the calculation. Output to the first arriving wave determination unit 124. Then, the first arriving wave determination unit 124 determines a component that is larger than a predetermined threshold value among the calculation results output from the relative level calculation unit 123 as an arriving wave component, and determines that component.
- the relative time difference between the position on the time axis where the symbol exists and the synchronization timing is output to the maximum delay time calculation unit 125 and the synchronization timing offset calculation unit 126 as a delay time.
- the synchronization timing offset calculation unit 126 determines the arrival wave component having the shortest delay time among the delay times output from the first arrival wave determination unit 124, and outputs a timing offset adjustment signal. .
- This figure shows how the delay profile changes when a phase rotation proportional to the number is given.
- FIG. 9 (a) shows a state in which the arriving wave 1 and the arriving wave 2 composed of the guard interval and the i-th symbol are received at different arrival times.
- FIG. 9A shows a received wave obtained by adding the arriving wave 1 and the arriving wave 2.
- the shaded portion before and after the received wave is a portion of intersymbol interference.
- the time interval in which the Fourier transform can be performed under the condition that it does not interfere with adjacent symbols is, for example, the time interval 1 as shown in Fig. 9 (a). .
- the position of the data interval 1 is determined by the synchronization timing, and the synchronization timing is determined on the condition that no inter-symbol interference occurs, and It can be arbitrarily determined within a time range depending on the arrival time difference.
- a synchronization timing is provided at the i-th symbol and the boundary timing where no inter-symbol interference occurs.
- FIG. 9 (a) the delay profiles for the signals obtained by performing the Fourier transform on the data section 1 are shown in FIGS. 9 (b) and 9 (c).
- the horizontal axis is the end of the guard interval of each arriving wave with respect to the start point of the data interval to be subjected to Fourier transform, that is, the delay time of the leading position of the i-th symbol with respect to the synchronization timing.
- the vertical axis represents the power corresponding to each arriving wave.
- FIG. 9 (b) shows a delay profile when the phase rotation section 14 does not apply phase rotation.
- the delay time corresponding to incoming wave 1 is the time difference c between the synchronization timing shown in FIG. 9 (a) and the end of the guard interval of incoming wave 1.
- It is configured to compare the amplitude or the square value of the amplitude of each transmission line characteristic with the highest level among the outputs of the relative level calculation unit 123.
- a configuration may be adopted in which an incoming wave is determined using a value smaller by the level as a threshold.
- the amplitude or the square of the amplitude of each transmission path characteristic having the smallest level is used as a reference, and a value larger than this reference value by a predetermined level as a threshold is used as an incoming wave. May be determined.
- the amplitude of the inverse Fourier transform output which is the output of the relative level calculating unit 123
- the incoming wave is determined using the square value of the amplitude as it is, but the square value of the amplitude or amplitude of the inverse Fourier transform output, which is the output of the relative level calculator 123, is determined for each component.
- the number of symbols may be averaged, and the first arriving wave determination unit 124 may determine the arriving wave based on the result.
- the amplitude of the inverse Fourier transform output which is the output of the relative level calculation unit 123, or the square value of the amplitude is averaged for a predetermined number of symbols for each component, and the carrier-to-noise power ratio of the subcarrier component is determined by a predetermined value. If the value is larger than the value, the arriving wave is determined by the first arriving wave determiner 124 based on the result before averaging, and if the carrier-to-noise power ratio is small, the result after averaging is also used. At the same time, the first arriving wave determination section 124 may be configured to determine the arriving wave.
- the demodulation device since the demodulation device according to the present embodiment performs interpolation in the time direction and calculates the delay profile based on the transmission characteristics after the interpolation, the time-dependent change in the channel characteristics is obtained. (E.g., when the receiver is installed on a moving object such as a car and the speed of the channel changes rapidly due to high-speed movement), the delay profile can be estimated accurately. it can.
- the pass band of the frequency internal filter can be set to a required minimum range.
- the demodulation device is configured to control the internal filter in the frequency direction while adjusting the synchronization timing for performing the Fourier transform.
- a phase rotation corresponding to the frequency of the subcarrier component is given to the subcarrier component output from the Fourier transform unit 1, and the subcarrier component in the frequency direction is also controlled. Construct a demodulation device.
- FIG. 8 is a block diagram showing a configuration of the demodulation device according to the present embodiment.
- the second timing synchronization section 13 in the demodulation device of the third embodiment differs from the first timing synchronization section 2 in the first or second embodiment in that the synchronization timing signal is based only on the S1 signal. Is output.
- phase rotation unit 14 rotates the phase of each subcarrier component output from the Fourier transform unit 1 according to the output of the phase adjustment amount calculation unit 15.
- the magnitude of the phase rotation is proportional to the frequency of each subcarrier component.
- the delay time of the arriving wave in the delay profile corresponding to the signals input to the pilot extraction unit 3 and the first delay adjustment unit 9 is represented on the time axis according to the magnitude of the phase rotation.
- the phase adjustment amount calculation unit 15 calculates the phase adjustment amount given to the subcarrier component in the phase rotation unit 14 based on the timing offset adjustment signal output from the first delay profile estimation unit 7. .
- the first delay adjuster 9 controls the phase rotator 14 so that the output of the phase rotator 14 and the output of the frequency interpolation filter 8 are input to the second divider 10 at the same timing. Delay the output from 14 for a predetermined time.
- FIG. 9 is a schematic diagram showing the relationship between the timing at which Fourier transform is performed and the delay profile in the demodulation device according to the present embodiment.
- FIG. 9 shows the frequency of the subcarrier component relative to the subcarrier component. This is because the time shift in the signal is converted into the phase rotation of each frequency component in the frequency domain.
- the time shift of the time domain signal can be apparently canceled, and the delay profile in the frequency domain is equivalently reduced. Can operate.
- the phase adjustment amount calculation unit 15 calculates the phase rotation amount based on the timing offset adjustment signal, and the phase rotation unit 14 gives a phase rotation in proportion to the frequency of the subcarrier component for each subcarrier component. Adjustment of the amount of phase rotation in the phase adjustment amount calculator 15 is the smallest among the delay times corresponding to each arriving wave component under the constraint that no intersymbol interference occurs. It is done to become. Therefore, the timing offset adjustment signal may be a signal proportional to the delay time of the arriving wave component having the shortest delay time.
- the second delay profile estimating unit 12 shown in Embodiment 2 is used instead of the first delay profile estimating unit 7 to estimate the delay profile from the output of the time interpolation filter unit 6. You may do it.
- the passband of the interpolation filter in the frequency direction can be minimized when estimating the transmission path characteristics without changing the synchronization timing of the Fourier transform. It is possible to suppress the degradation of the reception performance due to unnecessary noise components passing through the interpolation filter.
- the signal is demodulated by controlling the bandwidth of the synchronous timing and the frequency interpolation filter based on the delay profile obtained based on the output of the Fourier transform unit 1.
- the demodulation device according to the present embodiment applies a predetermined phase rotation corresponding to the frequency of the subcarrier component to the output of Fourier transform section 1, and performs synchronization based on a delay profile corresponding to the signal after the phase rotation. Demodulates signals by controlling the bandwidth of evening and frequency interpolation filters.
- FIG. 10 is a block diagram showing a configuration of the demodulation device according to the present embodiment.
- the Fourier transform unit 1, the first evening synchronization unit 2, the pilot extraction unit 3, the known signal generation unit 4, the first division unit 5, the time interpolation filter unit 6, the frequency interpolation filter Since the luminance unit 8, the second division unit 10, and the data reproduction unit 11 are the same as the demodulation device in the first embodiment, the same reference numerals are given to these components, and the detailed description is given. Is omitted.
- a fixed phase rotator 16 is provided at the subsequent stage of the Fourier transform unit 1, and the fixed phase rotator 16 is a subcarrier component output from the Fourier transform unit 1.
- a fixed amount of phase rotation in proportion to the frequency of the subcarrier component is given. Further, the first delay adjusting unit 9 sets the fixed phase so that the output of the fixed phase rotating unit 16 and the output of the frequency interpolation filter unit 8 are input to the second dividing unit 10 at the same timing. The output of the rotating unit 16 is delayed by a predetermined time.
- the synchronization timing of the Fourier transform is determined so as not to cause inter-symbol interference.
- the synchronization timing should be set to the minimum. It must be provided at the end of the guard section of the preceding incoming wave. In this case, the synchronization timing coincides with the boundary where inter-symbol interference occurs. Therefore, even if the synchronization timing is slightly deviated, inter-symbol interference occurs, and the error rate after demodulation increases.
- the synchronization timing may be shifted to the front of the symbol to cope with the synchronization timing jitter or the erroneous detection of the synchronization timing.
- the need to shift the synchronization timing to the front of the symbol also means that the bandwidth of the frequency interpolation filter cannot be narrowed sufficiently.
- the frequency interpolation filter in the demodulator of the first embodiment as a filter for band-limiting the time signal, the frequency interpolation filter is the narrowest when the complex filter passes only positive frequency components. Bandwidth.
- the necessary condition is that the frequency interpolation filter is a complex filter.
- the circuit scale can be reduced, but the passband is symmetric about the frequency band, so the passband is the desired band. Double the bandwidth.
- the first synchronization timing is set forward by half the guard section length with respect to the end of the guard section in the arriving wave corresponding to the largest power.
- the output of the Fourier transform unit 1 is configured to be given a predetermined phase rotation based on the guard section length and the frequency of the subcarrier component.
- the fixed phase rotator 16 in the demodulator cancels the time corresponding to the time required to shift the position of the synchronous timing forward (to the left in FIG. 10).
- the fixed phase rotation amount is given to the subcarrier component output from the Rie transform. As a result, it is possible to prevent inter-symbol interference due to deviations in synchronization timing and jitter.
- the delay profile of the transmission path characteristics at the output of the first divider 5 indicates that even if there is an incoming wave whose delay time is obtained as a negative value, intersymbol interference does not necessarily occur. Absent.
- FIG. FIG. 12 is a schematic diagram of a delay profile in a case where there is one incoming wave.
- the delay profile of A represents the delay profile obtained in the case of the demodulation device according to the first embodiment
- the delay profile of B represents the delay profile obtained in the case of the demodulation device of the present embodiment.
- the arriving wave exists in the hatched portion in the figure, that is, when it exists in the intersymbol interference generation area, it means that intersymbol interference occurs in the output of the Fourier transform unit 1. That is, as shown in FIG. 12B, in the demodulation apparatus according to the present embodiment, even if an arriving wave whose delay time is obtained as a negative value exists, the arriving wave exists in the inter-symbol interference generation region. do not do.
- the horizontal axis in FIG. 12 is the delay time shown in FIGS. 3 and 9. The same is true, but the delay time can be positive or negative, so for convenience of description, it is described as arrival time.
- the arrival time of the arriving wave only needs to be present in a symmetrical area around the position of zero arrival time, and the pass band of the intra-frequency filter is However, it may be the narrowest mouth-to-pass filter that can pass the incoming wave in the area. Therefore, if the frequency interpolation filter is regarded as a filter for band-limiting the time signal, the frequency interpolation filter is the narrowest when the pass band is a complex filter in which the pass band is asymmetric with respect to frequency zero. Although it is a band, as in the demodulation device according to the present embodiment, the spectrum corresponding to the arriving wave with the longest arriving time in the delay profile and the spectrum corresponding to the arriving wave with the shortest arriving time arrive.
- the frequency interpolation filter does not need to be a complex filter because the passband is symmetric with respect to the frequency zero.
- the band can be sufficiently narrowed with a small circuit.
- the timing offset adjustment signal input to the first timing synchronization section 2 is based on the condition that intersymbol interference does not occur, and the arrival time of the arriving wave having the longest arriving time and the shortest arriving time are It is given as a signal proportional to 1/2 (average value) of the sum of the arrival time of the arriving wave.
- the fill band control signal is given as a signal proportional to the absolute value of the arrival time of the arriving wave having the largest absolute value of the arrival time.
- an interpolation filter is determined according to the filter band control signal.
- the second delay profile estimating unit 12 shown in the second embodiment is used, and the delay profile is estimated from the output of the time interpolation filter unit 6. May be.
- the first timing synchronization section 2 may control the synchronization timing signal by controlling the operation clock of the analog / digital conversion for generating S1.
- the demodulation device in the demodulation device according to the fourth embodiment, the case has been described where the starting point of the Fourier transform, that is, the first synchronous evening is set to be at the center of the guard interval.
- the synchronization timing is from the end of the guard section to the guard section. It is sufficient if the position is shifted in the leading direction (leftward from the end of the guard section in FIG. 11), and the amount of phase rotation may be determined according to the position.
- the first synchronization timing is set to be in the center of the guard section as described above.
- the ratio with the effective symbol section length can be used as a parameter.
- 1/4, 1/8, 1/16, and 1/32 are set as the ratios.
- the first synchronization timing is located half the guard section length ahead of the end of the guard section in the arriving wave with the highest power.
- a predetermined phase rotation in accordance with the guard section length and the frequency of the subcarrier is applied to the Fourier transform output, thereby canceling the time when the position of the synchronization timing is shifted forward.
- Such a fixed amount of phase rotation can be given to the subcarrier component subjected to Fourier transform.
- the demodulator is configured to include the first delay profile 7, but instead of the first delay profile estimator 7, the second delay profile is used.
- the estimation unit 12 may be used.
Abstract
Description
Claims
Priority Applications (5)
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DE60321401T DE60321401D1 (de) | 2003-05-12 | 2003-12-19 | Demodulationseinrichtung und demodulationsverfahren |
US10/555,530 US7580466B2 (en) | 2003-05-12 | 2003-12-19 | Demodulation device and demodulation method |
EP03780921A EP1624602B1 (en) | 2003-05-12 | 2003-12-19 | Demodulation device and demodulation method |
JP2004548359A JP3654646B2 (ja) | 2003-05-12 | 2003-12-19 | 復調装置及び復調方法 |
TW093103600A TWI244281B (en) | 2003-05-12 | 2004-02-16 | Demodulation device and demodulation method |
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US7580466B2 (en) | 2009-08-25 |
JP3654646B2 (ja) | 2005-06-02 |
TW200425667A (en) | 2004-11-16 |
EP1624602A4 (en) | 2007-08-08 |
EP1624602A1 (en) | 2006-02-08 |
JPWO2004100413A1 (ja) | 2006-07-13 |
TWI244281B (en) | 2005-11-21 |
DE60321401D1 (de) | 2008-07-10 |
EP1624602B1 (en) | 2008-05-28 |
US20070036231A1 (en) | 2007-02-15 |
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