WO2003088538A1 - Recepteur et procede de reception associe - Google Patents
Recepteur et procede de reception associe Download PDFInfo
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- WO2003088538A1 WO2003088538A1 PCT/JP2003/004739 JP0304739W WO03088538A1 WO 2003088538 A1 WO2003088538 A1 WO 2003088538A1 JP 0304739 W JP0304739 W JP 0304739W WO 03088538 A1 WO03088538 A1 WO 03088538A1
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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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
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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
- H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
- H04L25/067—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing soft decisions, i.e. decisions together with an estimate of reliability
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2649—Demodulators
Definitions
- the present invention relates to a receiving apparatus and a receiving method for receiving a signal that has been frequency-division multiplexed by a plurality of carriers, such as an orthogonal frequency division multiplexing (hereinafter, referred to as OFDM (Orthogonal Frequency Division Multiplex)) transmission method.
- OFDM Orthogonal Frequency Division Multiplex
- modulation and demodulation are performed by allocating data to a plurality of carriers that are orthogonal to each other and are different from each other in the transmission band, and the transmitting side uses an inverse fast Fourier transform (hereinafter called IFFT (Inverse Fast Fourier Transform)). ) Process, and the receiving side performs fast Fourier transform (FFT (Fast Fourier Transform)) processing.
- IFFT Inverse Fast Fourier Transform
- FFT Fast Fourier transform
- Each carrier can use any modulation method, such as synchronous modulation such as QPSK (Quaternary Phase Shift Keying) and QAM (Quadrature Amplitude Modulation), and differential modulation such as DQPSK (Differential Quaternary Phase Shift Keying) .
- a pilot signal whose amplitude and phase are known on the receiving side is periodically inserted into a transmission signal, and demodulation is performed on the receiving side by obtaining transmission path characteristics based on the pilot signal.
- demodulation is performed by differential detection.
- error correction coding and decoding are performed to improve transmission characteristics.
- the level of a specific carrier drops due to reflected waves, multipath interference that occurs when a receiver mounted on a mobile unit is moving, and analog communication that coexists with digital broadcasting. If there is frequency-selective interference, which is mainly due to the same channel interference caused by broadcasting, demodulation performance and error correction capability may be significantly reduced.
- Patent Document 1 As an OFDM receiving device for avoiding such a situation, a device disclosed in Patent Document 1 described below has already been developed. This conventional technique will be briefly described with reference to the drawings.
- FIG. 24 shows a configuration of an OFDM receiving apparatus according to a conventional technique.
- an OFDM transmission signal is input to a tuner section 103 via a receiving antenna 101 and an RF amplifier 102, and channel selection is performed here.
- Tuning in the tuner section 103 is performed by adjusting the oscillation frequency of the local oscillator 111 to a desired channel frequency based on a frequency control signal input to the tuning information input terminal 110.
- the output of the tuner section 103 is converted to a digital signal by an analog / digital (hereinafter referred to as A / D) converter section 104, and is orthogonally detected by a quadrature detection section 105 to be converted to a baseband OFDM signal. Is converted.
- This baseband FDM signal is supplied to FFT section 106.
- the FFT section 106 converts the input OFDIV signal from a time domain to a signal in a frequency domain. Note that the clock and timing signal used in the AZD conversion clock and other digital circuits are those reproduced by the synchronous reproduction unit 112 from the baseband ⁇ FDM signal itself.
- the output of FFT 106 indicates the phase and amplitude of each carrier of the OFDM signal, and this is supplied to demodulation section 107.
- the demodulation unit 107 performs demodulation processing on the input FDM signal by synchronous detection corresponding to the modulation scheme. Synchronous detection refers to the detection of channel characteristics for each carrier using a pilot signal inserted at a rate of 1/3 in the frequency direction and 1Z4 in the time direction. Then, amplitude equalization and phase equalization are performed. In the synchronous detection, since a pilot signal is arranged in a 4-symbol cycle in a received OFDM signal, a 3-carrier-interval transmission path characteristic can be obtained by a 4-symbol pilot signal. Therefore, the transmission path characteristics of all carriers are obtained by interpolating these in the frequency direction.
- the demodulated signal is input to an error correction unit 108, and after an error generated during transmission is corrected, is output from an output terminal 109.
- the output of the FFT section 106 is also input to the interference detection section 113.
- the interference detection unit 113 determines the carrier affected by the frequency selective interference by determining the state of the received pilot signal.
- the signal is output to the correction unit 108 and the synchronous reproduction unit 112, and is used for improving the demodulation performance. That is, the demodulation unit 107 detects the transmission path characteristics of each carrier using a pilot signal at the time of synchronous detection, and performs amplitude equalization and phase equalization. However, if it is found that the frequency being interfered with matches the frequency of the pilot signal, this is not used, and a signal interpolated with a pilot signal that is not affected by interference is transmitted. Demodulation is performed by detecting road characteristics.
- the error correction unit 108 performs weighting processing such as erasure correction using carrier information under the influence of interference.
- the synchronous reproduction unit 112 performs synchronous reproduction with little error from a signal that is not disturbed.
- FIG. 25 is a block diagram showing a specific configuration of the interference detection unit 113 of the multicarrier receiving apparatus of FIG.
- the signal subjected to the fast Fourier transform from the FFT section 106 is input to the pilot extraction section 113a of the interference detection section 113.
- the pilot extractor 113a extracts a pilot signal from the input signal.
- the output is output to the integrator 113b and also supplied to the subtractor 113c.
- the integrator 113 b obtains an average value by integrating the amplitude of each pilot signal, and this average value is supplied to the subtraction unit 113 c.
- the subtraction unit 1 13 c detects the difference between the average value of the amplitude of each of the pilot signals and the amplitude of each of the pilot signals. Is output to the absolute value calculation unit 113 d.
- the absolute value calculation unit 113d calculates the absolute value of the error of each pilot signal.
- the output of the absolute value calculator 1 13 d is supplied to the integrator 1 13 e, and each The integration process of the error of the mouth signal is performed.
- the result of this processing is supplied to the comparing section 113f and the averaging section 113g as an error signal of each pilot signal.
- the error signal of each pilot signal corresponds to the CZN value of each pilot signal.
- the C / N value of each pilot signal is output by the averaging unit 113 g as the CZN value of all pilot signals.
- the comparison unit 113f compares the C / N value of each of the pilot signals with the C / N value of all the pilot signals, and if the difference between the comparison results is large, Judge that there is interference in frequency selectivity.
- the output of the comparison unit 113f is output to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112 as the interference carrier information described above.
- the error correction unit 108 improves the influence of the interference by performing weighting processing such as erasure correction on the carrier information affected by the interference.
- the conventional OFDM receiving apparatus monitors the pilot carrier of the received OFDM signal and determines the carrier that is being disturbed, thereby improving the demodulation performance.
- frequency-selective interference such as the same channel / level interference of a spurious / analog TV or a jump in the clock of the receiving device itself may occur. Under these influences, the performance of demodulation error correction is significantly degraded.
- the output of the integrator 113 e may be considered to indicate the level of the disturbance, but the value increases as the influence of the disturbance on the OFDM signal increases. Therefore, when frequency-selective interference is mixed in the received OFDM signal, the output of the integrator 113 e shows a prominent level near the position on the frequency axis where the interference exists.
- Fig. 12 shows the situation when two types of frequency selective interference are simultaneously superimposed on the received OFDM signal.
- the two types of frequency-selective disturbances are referred to as disturbance A and disturbance B, respectively, and disturbance A and disturbance B are assumed to exist near positions f A and f B on different frequency axes, respectively. In addition, it is assumed that disturbance A and disturbance B have different causes.
- the average part 113 g calculates the average value over all carriers (all pit signals). This is because, when a high-level signal that is locally protruded from the integrator 113 e is output, the value output by the average part 113 g is increased by the signal.
- the presence or absence of frequency-selective interference is determined based on the average value of the detected interference levels. If they do, relatively low-impact interferences may be missed. For this reason, error correction may be performed using the disturbed carrier, which may lead to poor demodulation error correction performance.
- the interference detection correction disclosed in Patent Document 2 is described.
- the second conventional example There is a method (hereinafter referred to as the second conventional example).
- the dispersion value (C / N value) of the carrier is detected as an interference level.
- an average value of the variance value is obtained in the frequency direction, a carrier having a variance value exceeding the average value is detected as a carrier subjected to frequency selective interference, and erasure correction is performed.
- the presence or absence of frequency-selective interference is determined based on the average value of the detected interference levels. If there is, there is a possibility that the detection of the interference with a relatively small influence may be missed. For this reason, error correction is performed using the disturbed carrier, which may result in poor demodulation error correction performance.
- the second conventional example describes a method of obtaining a minimum value of a variance value in the frequency direction and performing erasure correction for a carrier exceeding the minimum value as another interference detection and correction method.
- this alternative jamming detection and correction method may cause the following malfunctions.
- the method of obtaining the minimum value of the variance value in the frequency direction and performing erasure correction on a carrier exceeding the minimum value performs erasure correction on a carrier having a variance value exceeding the minimum value.
- a carrier that undergoes erasure correction processing for a cause other than its original purpose, even though it is not subject to frequency selective interference, rather degrades the performance of demodulation error correction. It leads to letting you do.
- an average value and a minimum value of the variance are obtained in the frequency direction as another interference detection and correction method, and a threshold level is provided between the minimum value and the average value.
- a technique for performing erasure correction on carriers exceeding the threshold level is also described. Also in this case, if there is frequency-selective interference that indicates a prominent interference level, the average value will increase due to the interference, so the threshold level will change depending on the interference situation. May be lost. For this reason, when there are multiple frequency-selective disturbances with different degrees of influence, detection of relatively small influences may be missed, resulting in poor demodulation error correction capability. There is.
- the spectrum is known, or the interference level becomes a prominent value. It also mentions a method of performing jamming detection by using the. However, even if this method is used, it is not always possible to calculate the optimum interference detection for frequency-selective interference other than co-channel interference in analog TV broadcasting.
- Patent Document 1
- Patent Document 2
- Patent No. 295 5570 (P. 8-9, Fig. 2)
- the present invention has been made in view of such a problem of the conventional technology, and the degree of influence on a multicarrier signal differs when a multicarrier signal such as OFDM is received and demodulated and error corrected. It is an object of the present invention to provide a receiving apparatus and a receiving method capable of accurately detecting the influence of simultaneous interference of a plurality of frequency selectivities and suppressing deterioration of demodulation error correction performance. . Disclosure of the invention
- an information signal to which a plurality of carriers (hereinafter, referred to as carriers) generated at different frequencies in a transmission band are assigned respectively.
- a reference value calculation unit that calculates the degree of influence of frequency-selective interference from the received FDM transmission signal as an interference level, and a reference value calculation unit that calculates the interference level based on the reference value and the interference level.
- an interference average calculating unit that calculates an average value of an interference level detected by the interference detecting unit.
- the reliability determination unit determines a carrier subjected to frequency selective interference based on the average value calculated by the interference average calculation unit and the interference level, and the received FDM based on the reference value. This is to determine the reliability level of the carrier constituting the transmission signal.
- an interference average calculating unit that calculates an average value of an interference level detected by the interference detecting unit;
- An interference determination unit that determines the degree of influence of the interference over the transmission band ⁇ ⁇ ⁇ based on the average value of the interference levels, and outputs the result as an interference determination level.
- the reliability determination unit outputs an output of the interference determination unit. Accordingly, the determined reliability level value is controlled.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by information signals assigned to the respective carriers, and the information signal And a demodulation unit for demodulating an information signal from the received FDM transmission signal, wherein the reception device receives a FDM transmission signal in which a pilot signal serving as a reference for detection is detected for a plurality of carriers modulated by the FDM transmission signal.
- a reference value calculation unit that calculates an average power of a transmission path characteristic of the carrier based on the pilot signal inserted in the received FDM signal and outputs the average power as a reference value;
- An interference detection unit that detects the degree of the influence of frequency selective interference on a plurality of carriers of the DM signal as an interference level, and sets one or more thresholds based on the reference value;
- a reliability determination unit that determines the reliability of the plurality of carriers based on the comparison result and outputs the result as a reliability level; and corrects an error in the demodulated output based on the reliability level.
- an error correction unit for performing the following.
- the carrier suffering frequency selective interference can be determined more accurately, and error correction can be performed according to the degree of the interference effect. Demodulation error correction capability can be improved.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by an information signal allocated to each of the FDM transmission signals.
- a receiving device which demodulates an information signal from the received FDM transmission signal, calculates an average power of a plurality of carriers constituting the received FDM signal, and outputs the average power as a reference value.
- a reference value calculation unit an interference detection unit that detects a degree of the influence of frequency selective interference on a plurality of carriers of the received FDM signal as an interference level, and a threshold or a plurality of thresholds based on the reference value.
- a reliability determination unit that sets the number, compares the threshold value with the interference level, determines the reliability of the plurality of carriers based on the comparison result, and outputs the reliability as a reliability level; and the demodulation output. In contrast, based on the confidence level! And an error correction section for performing error correction.
- the carrier suffering the frequency selective interference can be more accurately determined, and the error correction can be performed according to the degree of the influence of the interference. Error correction capability can be improved.
- a plurality of carriers generated at different frequencies in a transmission band are modulated with information signals assigned to the respective carriers, and the information signal And a demodulation unit for demodulating an information signal from the received FDM transmission signal, wherein the reception device receives a pilot signal serving as a reference for detection for a plurality of carriers modulated by the FDM transmission signal.
- a reference value calculation unit that calculates the average power of the signals, and outputs the reference power as a reference value; Setting one or more first threshold values based on the reference value, performing a first comparison between the interference level and the first threshold value, and calculating an average value based on a result of the first comparison.
- An interference average calculation unit that calculates the average of the interference levels selected by the selection and outputs the average as an interference average level; and 2 is compared, a carrier that has been subjected to frequency selectivity interference is determined based on the result of the second comparison, and one or more second thresholds are set based on the reference value.
- the frequency selection A third comparison is performed on the interference level of a carrier that has suffered interference with the second threshold and the second threshold, and the reliability of the plurality of carriers is determined based on the result of the third comparison. It is provided with a reliability judgment unit for outputting, and an error correction unit for performing error correction on the demodulated output based on the reliability level.
- the original interference level is determined without the influence of the floor, so that the carrier affected by the frequency selective interference can be determined more accurately, and the level of the influence of the interference is determined.
- Error correction can improve the demodulation error correction capability.
- the FDM transmission signal modulated with the information signal to which a plurality of carriers generated at different frequencies are assigned to the transmission band ⁇ is used.
- a receiving unit for demodulating an information signal from the received FDM transmission signal, calculating an average power of a plurality of carriers constituting the received FDM signal, and outputting the average power as a reference value A reference value calculation unit, an interference detection unit that detects the degree of the influence of frequency selective interference on the plurality of carriers of the received FDM signal as an interference level, and a single first threshold based on the reference value.
- An interference average calculator that calculates an average value of the selected interference levels and outputs the average as an interference average level
- the original interference level is determined without the influence of the floor, so that the carrier affected by the frequency selective interference can be more accurately determined, and the degree of the interference influence can be determined. Error correction can be performed accordingly, and the demodulation error correction capability can be improved.
- the interference average calculating unit sets the first threshold to: One or more fixed values are set.
- the average interference level can be output as a multi-step value. Can calculate the average level of interference flexibly according to the value of, and can more accurately determine the carrier affected by frequency selective interference. This has the effect of further improving the correction ability.
- the interference average calculation unit includes the interference level and the first interference. Performing a first comparison with respect to the threshold value, correcting the interference level based on a result of the first comparison, calculating an average value of the interference levels including the detected interference level, and calculating the interference average. It is output as a level.
- the interference average calculating unit includes the interference level and the interference level.
- Performing a first comparison with a first threshold value selecting the interference level for calculating an average value based on the result of the first comparison, and calculating an average value of the interference level selected by the selection;
- the average value of the interference average level is calculated and multiplied by a predetermined coefficient, and the average value is output as the interference average level.
- the raised average value is used as the interference average level, the detection accuracy of the floor is improved, and even if a floor exists in the detected interference level, the original interference level is determined by removing the influence of the floor.
- the carrier suffering from frequency selective interference can be determined more accurately, and error correction can be performed according to the degree of the influence of the interference, so that the demodulation error correction capability can be further improved.
- the reliability determination unit is configured to control the second threshold value. Is set as one or more fixed values.
- the reliability judgment level can be output in multiple levels, and a flexible reliability level according to the interference level If the floor is present at the detected interference level, the original interference level is determined by removing the influence of the floor, making it possible to more accurately determine the carrier subjected to frequency-selective interference. Since error correction can be performed according to the degree of influence of demodulation, demodulation error correction capability can be further improved.
- the signal '! A difference between the level and the interference average level is calculated as a difference level, a carrier that has been subjected to frequency-selective interference is determined based on the difference level, and a carrier that has been determined to have received the frequency-selective interference is determined.
- Performing a third comparison on the difference level and the second threshold determining the reliability of the plurality of carriers stepwise based on a result of the third comparison, and outputting the determined level as the reliability level; It is like that.
- the original interference level is determined by excluding the effect, so that the carrier affected by frequency-selective interference can be determined more accurately, and the degree of interference Error correction can be performed, so that the demodulation error correction capability can be improved.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by information signals assigned to the respective carriers
- a disturbance detection unit that detects the degree of influence of frequency selective disturbance on a plurality of carriers of the received FDM signal as a disturbance level, and a disturbance that calculates an average value of the disturbance levels and outputs the average value as a disturbance average level.
- An average calculation unit, an interference determination unit that compares the interference average level calculated by the interference average calculation unit with the interference determination reference value, and a single or a plurality of third thresholds are set based on the reference value.
- a reliability determining unit that corrects the reliability of the plurality of carriers and outputs the result as a reliability level
- an error correction unit that performs error correction on the demodulated output based on the reliability level. It is.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by an information signal assigned to each of the FDM transmission signals.
- a receiving device for receiving comprising: a demodulation unit for demodulating an information signal from the received FDM transmission signal; and a plurality of components constituting the received FDM signal.
- a reference value calculation unit that calculates an average power of the carrier of the received FDM signal and outputs the reference power as a reference value; and an interference detection unit that detects a degree of influence of frequency selective interference on a plurality of carriers of the received FDM signal as an interference level.
- An interference average calculation unit that calculates the average value of the interference levels and outputs the average as the interference average level; and an interference determination unit that compares the interference average level calculated by the interference average calculation unit with the interference determination reference value.
- One or more first threshold values are set based on the reference value, a first comparison is made between the first threshold value and the interference level, and the first comparison is performed based on a result of the first comparison.
- a reliability determination unit that determines the reliability of the plurality of carriers, corrects the reliability of the plurality of carriers based on the interference determination level, and outputs the corrected level as a reliability level; Said Those having an error correction unit that performs error correction based on the-reliability levels.
- the interference determination unit is based on the reference value.
- One or more third thresholds are set, and a fourth comparison is made with respect to the average interference level and the third threshold, based on the result of the fourth comparison, within the transmission band due to the interference. , And outputs the result as the interference determination level.
- the interference determination level can be output in multi-step values, and a flexible calculation of the interference determination level according to the average interference level can be performed, so that all carriers such as fading can be calculated. If the interference is erroneously recognized as frequency selective interference and the reliability of the carrier is excessively reduced, the problem of deteriorating the demodulation error correction performance on the contrary can be resolved, and the demodulation error correction capability can be improved even for fading interference. It is better.
- the interference determination unit is configured to: the third threshold , One or more fixed values are set.
- the process of calculating the third threshold becomes unnecessary, and when there are a plurality of third thresholds, the interference determination level can be output in multiple levels, and a flexible interference determination level corresponding to the average interference level can be obtained. Since calculation is possible, it is possible to mistakenly disturb all carriers, such as fading, as frequency selective interference, resulting in excessively low carrier reliability and degraded demodulation error correction performance. The demodulation error correction ability can be further improved even with fading interference.
- a plurality of carriers generated at different frequencies within a transmission band are modulated by information signals assigned to the respective carriers.
- a fourth threshold value is set by setting one or more threshold values, comparing the threshold value with the interference level, determining the reliability of the plurality of carriers based on the comparison result, and outputting the reliability as a reliability level. And a fifth step of performing error correction on the demodulated output based on the reliability level.
- the carrier affected by frequency selective interference can be determined more accurately, and error correction can be performed in accordance with the degree of influence of the interference, so that a receiving method that can improve the demodulation error correction capability can be obtained.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by information signals assigned to the respective carriers, and A method of receiving an FDM transmission signal in which a pilot signal serving as a reference for detection is detected for a plurality of carriers modulated by a signal, wherein the information signal is obtained from the received FDM transmission signal.
- a first threshold or a plurality of first thresholds is set based on the reference value, a first comparison is performed on the interference level and the first threshold, and based on a result of the first comparison.
- a fourth step of selecting the interference level for which the average value is to be calculated by calculating the average value of the interference levels selected by the selection, and outputting the average value as the average interference level; and the interference level and the average interference level.
- a second carrier is determined based on the result of the second comparison, and a carrier that has been interfered with frequency selectivity is determined, and one or more second thresholds are set based on the reference value.
- a plurality of carriers generated at different frequencies in a transmission band are modulated by information signals assigned to the respective carriers, and A receiving method for receiving an FDM transmission signal in which a pilot signal serving as a reference for detection is inserted into a plurality of carriers modulated by an information signal, wherein the information signal is obtained from the received FDM transmission signal.
- a sixth step of correcting the reliability and outputting the result as a reliability level, and a seventh step of performing error correction on the demodulated output based on the reliability level. is there.
- a multi-carrier signal such as OFDM
- demodulated, and error-corrected a plurality of frequency-selective disturbances having different degrees of influence on the multi-carrier signal are simultaneously affected. Even if it is received, the effect can be detected with high accuracy, and the performance of demodulation error correction can be improved.
- FIG. 1 is a diagram showing an overall configuration of a multicarrier receiving apparatus according to Embodiment 1 of the present invention.
- FIG. 2 is an explanatory diagram showing an arrangement of a pilot signal.
- FIG. 3 is a layout diagram in which transmission line characteristics of a pilot signal can be obtained.
- FIG. 4 is an explanatory diagram showing the concept of time axis interpolation of a pilot signal.
- FIG. 4 (a) shows a direction in which time axis interpolation is performed based on a pilot signal
- FIG. FIG. 6 is a diagram showing a temporal arrangement in which a transmission signal characteristic obtained by interpolating a transmission signal and time axis interpolation is obtained.
- Fig. 5 is an explanatory diagram showing the concept of frequency axis interpolation of the Pipit signal.
- Fig. 5 (a) shows the frequency axis interpolation based on the Pipit signal and the signal interpolated on the time axis.
- Fig. 5 (b) is a diagram showing a pilot signal, a signal interpolated on the time axis, and a signal interpolated on the frequency axis.
- FIG. 6 is a layout diagram of an error signal output from the error calculation unit according to the first embodiment of the present invention.
- FIG. 7 is a layout diagram of the interference level output from the error signal interference calculation unit, and
- FIG. 7 (a) is a diagram showing a direction in which interpolation is performed in the time axis direction based on the error signal. The figure shows an error signal and a signal on which time axis interpolation is performed.
- FIG. 8 is a layout diagram of interference levels output from the interference calculation unit according to the first embodiment.
- FIG. 9 is an explanatory diagram showing the concept of frequency axis interpolation of interference level.
- Fig. 9 (a) shows the direction of interpolation on the frequency axis based on the interference level
- FIG. 3 is a diagram showing a signal subjected to level and frequency axis interpolation.
- FIG. 10 is a diagram for explaining the operation of the reliability judgment unit 9 provided in the first embodiment of the present invention.
- FIG. 10 (a) shows an example of an interference level having two peaks.
- FIG. 10 (b) is a diagram showing the result of determining the reliability level.
- FIG. 11 is a diagram showing the concept of the soft decision decoding method.
- FIG. 12 is a diagram illustrating a state of a received signal that has been subjected to frequency selective interference.
- FIG. 13 is a diagram showing a relationship between an interference level obtained by the interference detection unit 8 provided in the first embodiment of the present invention and a threshold used in the reliability determination unit 9; a) The figure shows the case where the threshold value is lower than the disturbance A and B, where the difference between the peaks is not so large, and two disturbances can be detected.
- Figure 13 (b) shows the large difference between the peaks. It is a figure which shows the case where a threshold value becomes low with respect to disturbance A and disturbance B, and two disturbances can be detected.
- FIG. 14 is a diagram in which Embodiment 1 of the present invention is replaced with another configuration.
- FIG. 15 is a diagram showing an example of the internal configuration of the reference value calculation unit in FIG.
- FIG. 16 is a diagram showing an overall configuration of a multicarrier receiving apparatus according to Embodiment 2 of the present invention.
- FIG. 17 is a diagram showing a state of a floor at an interference level.
- FIG. 18 is a diagram showing the state of the interference level and its average value.
- FIG. 19 is a diagram showing the state of the interference level affected by Gaussian noise.
- FIG. 20 is a diagram showing a configuration of a disturbance average calculating unit provided in the second embodiment of the present invention.
- FIG. 21 is a diagram showing an entire configuration of a multicarrier receiving apparatus according to Embodiment 3 of the present invention.
- FIG. 22 is a diagram showing the state of the interference level when fading interference has occurred.
- FIG. 23 is a diagram showing an overall configuration of a multi-carrier receiving apparatus in which Embodiment 2 and Embodiment 3 of the present invention are combined.
- FIG. 24 is an overall configuration diagram of an OFDM receiving apparatus according to a conventional technique.
- FIG. 25 is a configuration diagram of a disturbance detection unit provided in an OFDM receiver according to the conventional technique.
- FIG. 26 is a diagram showing the output level of the integrator 1 13 e and the average value output from the averaging section 113 g in the conventional technology, and FIG. 26 (a) shows that the difference between the peaks is small.
- Fig. 26 (b) shows a case where two thresholds can be detected because the threshold is low for non-large interferences A and B.
- Fig. 26 (b) shows a high threshold for disturbances A and B with a large peak difference.
- FIG. 9 is a diagram showing a case where it becomes difficult to detect disturbance B.
- the first embodiment corresponds to the invention described in claims 1, 4, 5, and 17, and follows the transmission line characteristics but follows the interference level.
- frequency-selective interference By detecting frequency-selective interference using a difficult reference value as a threshold, frequency-selective interference can be accurately detected, and demodulation error correction performance can be improved.
- the following describes the multicarrier receiving apparatus according to Embodiment 1 of the present invention, which is applied as an apparatus for receiving an OFDM transmission message.
- FIG. 1 is an overall configuration diagram of a multicarrier receiving apparatus according to Embodiment 1 of the present invention.
- an OFDM transmission signal supplied to a multi-carrier receiving apparatus through a receiving antenna or a cable is tuned by a tuner unit 1 using a local oscillation signal, and after being converted into a digital signal by an AZD conversion unit 2, Input to quadrature detector 3.
- the quadrature detection unit (detection unit) 3 performs quadrature detection on the input signal, converts it to a baseband OFDM signal, and outputs it.
- the FFT unit (signal conversion unit) 4 performs a fast Fourier transform on the input signal, and converts the time domain signal to the frequency domain signal. And output.
- This FFT output indicates the phase and amplitude of each carrier of the OFDM transmission signal, and is specifically handled in the form of a complex signal having independent levels in the I-axis and Q-axis directions.
- the demodulator 5 demodulates information signals allocated to multiple carriers by performing differential detection or synchronous detection on the input frequency-domain OFDM signal, and corrects the result as a demodulated signal. Output to Part 6.
- the reference value calculation unit 7 estimates the transmission path characteristics of the carrier in the transmission band from the received signal, calculates the reference power by calculating the average power of the transmission path characteristics of the carrier, and sends the result to the reliability determination unit 9. Output.
- This reference value follows the fluctuation of the transmission line characteristics, such as fading (a phenomenon in which the phase and amplitude of the received signal fluctuates with time when receiving a moving object), and follows this. The signal is not easily affected by interference.
- the interference detection unit 8 detects an interference level indicating the degree of influence of frequency selective interference in the received signal for each carrier, and notifies the signal individual determination unit 9 of the result.
- the interference detector 8 detects the interference level based on the signal input from the demodulator 5.
- the reliability determination unit 9 determines the reliability level for each carrier for each carrier based on the interference level from the interference detection unit 8 and the reference value from the reference value calculation unit 7, and sends it to the error correction unit 6. Output.
- the error correction unit 6 performs a soft decision on the OFDM signal demodulated by the demodulation unit 5, performs a correction based on the reliability level obtained by the reliability determination unit 9, and performs error correction.
- the reference value calculating section 7 and the interference detecting section 8 perform the reliability determination in the second and third steps in the receiving method according to claim 17 of the present invention.
- the unit 9 performs the processing corresponding to the fourth step, and the error correction unit 6 performs the processing corresponding to the fifth step.
- the demodulation unit 5 shows a form in which synchronous detection is performed, and as shown in FIG. It is composed of a pilot signal generator 51, a complex divider 52, a time axis interpolator 53, a memory 54, a frequency axis interpolator 55, and a complex divider 56. It can be something.
- a pilot signal is periodically inserted at discrete intervals in the frequency direction and the time axis direction as a reference signal for detection.In the case of synchronous detection, this pilot signal is amplitude- It shall be used as a reference for phase equalization.
- the pilot signal generator 51 generates a known pilot signal at the same timing as the pilot signal periodically inserted into the OFDM signal in the frequency domain. Output to 2.
- FIG. 2 shows a specific example of the arrangement of the pilot signal.
- D 1 indicates the position of the data carrier
- P 1 indicates the position of the pilot signal.
- the no-mouth signal is inserted into the OFDM signal in the frequency domain at a rate of one period with four symbologies.
- FIG. 3 shows the arrangement of the transmission line characteristics of the pilot signal estimated based on the arrangement of the pilot signals shown in FIG.
- C 1 indicates the position where the transmission line characteristics of the pilot signal can be obtained, and the transmission line characteristics cannot be obtained at the position of C O in FIG.
- the complex divider 52 shown in FIG. 1 is configured to generate a known pilot signal generated by the noise port signal generator 51 with respect to the pilot signal periodically inserted into the OFDM signal in the frequency domain. Performs complex division by the lot signal (reference value), estimates the transmission path characteristics of the pilot signal, and outputs it to the time axis interception unit 53.
- the time axis interpolator 53 sequentially accumulates the transmission path characteristics of the pilot signal obtained by the complex divider 52 in the memory 54, and the carrier present at the same position as the pilot signal on the frequency axis. For this, the transmission path characteristics of the pilot signal at the same carrier position stored in the memory unit 54 are read and applied. As a result, transmission path characteristics interpolated in the time axis direction (0-order interpolation) are obtained at fixed carrier intervals, and this signal is output to the frequency axis interception unit 55.
- the time axis interpolation unit 53 sequentially stores the transmission path characteristics of the pilot signal obtained by the complex division unit 52 in the memory unit 54, and stores the pilot signal obtained by the complex division unit 52. Transmission path characteristics of the cut signal and just one round on the time axis stored in the memory unit 54 From the transmission path characteristics of the pilot signal before the period, it is also possible to perform interpolation (primary interpolation) on the carrier existing at the same position as the pilot signal on the frequency axis and output it to the frequency axis interpolation unit 55. Good. This makes it possible to perform high-accuracy sampling that follows the time variation of the transmission path characteristics, and to improve the demodulation performance. Also in this case, similarly to the zero-order interpolation, transmission line characteristics interpolated (primary interpolation) in the time axis direction are obtained at regular carrier intervals, and this signal is output to the frequency axis interpolation unit 55.
- FIG. 4 shows a conceptual diagram of a time axis interpolation process based on the arrangement of the transmission path characteristics of the pilot signal shown in FIG.
- the arrow TC in FIG. 4 (a) indicates the position at which the time axis interpolation is performed and its order.
- C1 indicates a position at which the transmission path characteristic of the pilot signal is obtained
- C2 indicates a position at which the transmission path characteristic interpolated on the time axis is obtained. No transmission path characteristics can be obtained at the position C0 in FIG. 4 (b).
- the frequency axis interpolator 55 shown in FIG. 1 captures in the frequency axis direction by passing the transmission path characteristics obtained at the time axis interpolator 54 at constant carrier intervals on the frequency axis through a filter, and Is output to the complex division unit 56 as a transmission path characteristic with respect to.
- FIG. 5 shows a conceptual diagram of the frequency axis interpolation processing based on the time axis interpolation result shown in FIG. 4 (b).
- the curve FC in FIG. 5 (a) shows the position where the frequency axis interpolation is performed and its order.
- C1 indicates the position where the transmission path characteristics of the pilot signal can be obtained.
- C3 in FIG. 5 (b) indicates a position where frequency-interpolated transmission path characteristics can be obtained.
- the complex division unit 56 shown in FIG. 1 performs complex division on each carrier signal input to the demodulation unit 5 based on the carrier channel characteristics of the carrier obtained by the frequency axis interpolation unit 55, and calculates the calculation result. Output as a demodulated signal.
- the reference value calculation unit 7 includes a pilot signal generation unit 51, a complex division unit 52, a time axis interpolation unit 53, a memory unit 54, and a frequency interpolation unit. 55, a power calculation unit 71, and an average calculation unit 72.
- the reference value calculation unit 7 can use the signal obtained in the process of the demodulation unit 5 to calculate the reference value that is less affected by the interference level than the input signal.
- the components are shared with the demodulation unit 5. That is, the input signal is an OFDM signal in the same frequency domain as the demodulation unit 5, and the pilot signal
- the generation unit 51, the complex division unit 52, the time axis interpolation unit 53, the memory unit 54, and the frequency axis sampling unit 55 share these with the demodulation unit 5. Therefore, in FIG. 1, the same numbers are assigned to the components shared by the demodulation unit 5 and the reference value calculation unit 7. Note that a detailed description of some of the components shared by the demodulation unit 5 and the reference value calculation unit 7 will be omitted.
- the frequency axis interpolator 55 in the reference value calculator 7 interpolates the transmission path characteristics at constant carrier intervals on the frequency axis obtained by the time axis interpolator 53 in the direction of the frequency axis by passing them through a filter.
- the signal is output to the complex division unit 56 as a transmission path characteristic for the carrier, and is output to the power calculation unit 71.
- the power calculation unit # 1 receives the transmission path characteristics for all carriers output from the frequency axis interpolation unit 55 as input, calculates the power of this signal, and calculates the average as the power of the transmission path characteristics for all carriers. Output to unit # 2.
- the average calculation section 72 calculates and outputs the average value of the transmission path characteristic power for all carriers output by the power calculation section 71.
- the average value may be calculated by integrating the power of the transmission path characteristics for all carriers over the frequency domain and the time axis domain.
- the average power of the transmission line characteristics for all carriers obtained by the above-mentioned processing has the characteristics of following the fluctuations of the transmission line characteristics such as fading, as well as frequency selective interference such as spurious and analog TV channel interference. Even if they are affected, the ratio of carriers affected by them is very low compared to the whole, and large changes in the average power level of the entire carriers are unlikely to appear, so that they are less susceptible to frequency selective interference.
- the interference detection unit 8 includes a difference calculation unit 81, an integration unit 82, a time axis interpolation unit 83, and a frequency axis interpolation unit 84.
- the interference detection unit 8 includes a transmission path characteristic for a noise signal, which is obtained in the process of the demodulation unit 5, and a pilot signal one cycle before on the time axis.
- the input signal and the transmission path characteristics for the G signal are input, and the level of interference with the Pipit signal is detected from the difference between these two transmission path characteristics, that is, the amount of temporal fluctuation. Is interpolated in the time axis and frequency axis directions, and is output as an interference level for all carriers.
- the difference calculation unit 81 in the interference detection unit 8 determines these complex values based on the transmission path characteristics for the pilot signal output from the complex division unit 52 and the transmission path characteristics for the pilot signal output from the memory unit 54. The difference is obtained, the power is further obtained, and the obtained power is output to the integration section 82.
- the transmission path characteristic for the pilot signal output from the memory section 54 is one cycle earlier on the time axis than the transmission path characteristic for the pilot signal output from the complex division section 52. Therefore, the difference calculation unit 81 obtains the amount of change of the two transmission line characteristics during one cycle.
- FIG. 6 shows the arrangement of error signals calculated based on the arrangement of the transmission path characteristics of the pilot signal shown in FIG.
- E 1 indicates a position where an error signal is obtained, and no error signal is obtained at the position of E 0.
- the integrating unit 82 in FIG. 1 integrates the difference of the transmission line characteristics for each cycle at the position of each pilot signal on the frequency axis, obtained by the difference calculating unit 81, and calculates the integration result on the time axis. Output to interpolator 83.
- the result of this integration indicates the average variation of the channel characteristics with respect to the pilot signal.At the position of the pilot signal that is affected by frequency selectivity, the variation in the channel characteristics of the pilot signal is shown. Higher levels indicate higher levels.
- this integration result is present at discrete positions at regular intervals on the time axis.
- the time axis interpolation unit 83 interpolates on the time axis the discrete integration results on the time axis obtained by the integration unit 82 and outputs the result to the frequency axis interpolation unit 84.
- the time axis interpolation method may be either zero-order interpolation or first-order interpolation.
- the average fluctuation amount is calculated for the carrier at the same position as the pilot signal on the frequency axis.
- the signal output by the time axis intercepting section 83 exists at the same position on the frequency axis as the pilot signal and at regular intervals with a constant carrier interval.
- FIG. 7 shows a conceptual diagram of the time axis interpolation processing based on the arrangement of the error signal shown in FIG.
- arrow TE in Fig. 2 (a) indicates the position and the order in which the time axis capture including the average calculation is performed.
- E1 indicates the position where the error signal is obtained
- E2 is the time axis. The position at which the captured error signal is obtained is shown. No error signal is obtained at the position of E 0 in the seventh (b).
- Fig. 8 shows the disposition of the interference level calculated based on the disposition of the misrepresentation shown in Fig. 7 (b).
- I 1 indicates the position where the interference level can be obtained, and at the position I 0 in FIG. 8, the interference level cannot be obtained.
- the frequency axis interpolator 84 shown in Fig. 1 uses the filter to filter the signals that are obtained at the time axis interpolator 83 and that exist at discrete positions on the frequency axis at fixed carrier intervals. Interpolate and output as interference level for all carriers. This interference level will be high near the carrier that has been subjected to frequency selective interference.
- FIG. 9 shows a conceptual diagram of the frequency axis interpolating process based on the interference level arrangement shown in FIG.
- the arrow F1 in FIG. 9 (a) indicates the position where the interference level is obtained
- the arrow I2 in FIG. 9 (b) indicates the position where the interference level interpolated on the frequency axis is obtained.
- the reliability judging unit 9 may include a threshold setting unit 91, a comparing unit 92, and a reliability level judging unit 93.
- the reliability determination unit 9 sets a threshold based on the reference value obtained by the reference value calculation unit 7, and compares the threshold with the interference level obtained by the interference detection unit 8, thereby receiving the interference. This is to identify the carrier that has been affected, to obtain a signal indicating the degree of the effect for each carrier in a stepwise manner, and to output the signal to the error correction unit 6 as a reliability level.
- the threshold setting unit 91 sets a threshold based on the reference value obtained by the reference value calculation unit 7, and outputs the threshold to the comparison unit 92.
- This threshold may be set experimentally so that the error rate of the received signal is minimized while comparing with the interference level.
- the reference value obtained by the reference value calculation unit 7 may be set to P and a predetermined coefficient may be set as, and the threshold value may be set by the product P ⁇ a.
- One or more thresholds may be used.
- the comparison unit 92 compares the interference level obtained by the interference detection unit 8 with the threshold obtained by the threshold setting unit 91 for each carrier, and determines the degree of the interference level with respect to the threshold. At this time, for example, when the number of thresholds is one, whether or not the interference level exceeds the threshold is determined and output. If there are a plurality of thresholds, it determines which threshold the interference level is between and outputs it.
- the reliability level determining section 93 determines a reliability level for each carrier according to the result obtained by the comparing section 92 and outputs the result to the error correcting section 6.
- the reliability level may be expressed by two values of the presence or absence of interference.
- the reliability level may be expressed as a multi-level value of two or more levels and output, so that the reliability level can be flexibly calculated according to the interference level.
- FIGS. 10 (a) and 10 (b) An example of the operation of the reliability determination unit 9 as described above will be described with reference to FIGS. 10 (a) and 10 (b).
- position f It is assumed that an interference level having different peaks near A and fB is obtained by the interference detection unit 8.
- the threshold setting unit 91 has set two thresholds based on the reference value, the thresholds “ ⁇ ” and “L.”
- the comparison unit 92 sets the interference level and the threshold “H” and In comparison with “L”, the interference level is above the threshold ' ⁇ "near fA, and the interference level is near the threshold” L “and' ⁇ ” near fB. Yes, and at other positions on the frequency axis, it is determined that the disturbance level is below the threshold “L.”
- the reliability level determination unit 93 determines the reliability level in ascending order of reliability. ⁇ Is expressed in three levels of "2", “7", and "10". For a carrier with an interference level exceeding the threshold """, the lowest reliability level is considered as the least reliable.
- the reliability level judgment unit 93 determines whether an intermediate reliability.
- the reliability level of the carrier near position fA is "2"
- the reliability level of the carrier near position fB is "7"
- the reliability level of other carriers is "10”. Then, the error correction unit 6 performs error correction based on the reliability level, thereby suppressing degradation of demodulation error performance due to the influence of co-channel interference even if co-channel interference occurs. Performance can be improved.
- the error correction unit 6 includes a soft decision unit 61, a soft decision correction unit 62, and an error correction decoding unit 63.
- the error correction unit 6 performs a correction process by soft decision decoding using the above reliability level.
- Soft-decision decoding is to convert a demodulated signal into a soft-decision information signal corresponding to the original information signal used in the modulation process, and to combine the soft-decision information signal with the original information signal (a known The accuracy of the received signal is expressed using the distance to the information signal and the like, and the sequence of the information signal is estimated by accumulating the information.
- FIG. An example of the soft decision decoding method is shown in FIG.
- a soft-decision information signal that is positioned stepwise between and around the original information signals " ⁇ " and "1", and the input demodulated signal contains "0" and "1"
- the soft-decision information signal is converted to the nearest signal among the soft-decision information signals, and the converted soft-decision information signal is an information signal that is decoded closer to the original information signal "0" or "1" It can be said that the closer to the center between the original information signals "0" and "1", the lower the reliability of the decoded information signal. Is converted to "0.5" as erasure.
- the soft decision unit 61 converts the demodulated signal obtained by the demodulation unit 5 into the above-described method.
- the soft decision correction unit 62 uses the reliability level obtained by the reliability decision unit 9 to convert it into a soft decision information signal.
- the soft decision information signal obtained by the decision unit 61 is corrected, specifically, the reliability of the soft decision information signal is made lower according to the reliability level, that is, the original information signal "0".
- the correction operation for the soft-decision information signal is performed closer to the center between "1" and "1". Do.
- the threshold for determining the level of the interference level it is hardly affected by frequency-selective interference and has a property of following the fluctuation of the transmission path characteristic. Since the signal is set as a reference, the threshold adaptively follows the fluctuation of the transmission line characteristics, etc. There is an effect that appropriate appropriate judgment can be made.
- FIG. 13 (a) and FIG. 13 (a) show processing performed when the multi-carrier receiving apparatus of the first embodiment receives a ⁇ FDM signal in which the two types of frequency selective interference shown in FIG. 12 are superimposed. This will be described with reference to FIG. 13 (b). Two types of frequency-selective disturbances A and B having different causes are assumed to exist near positions fA and fB on the frequency axis, respectively.
- Figs. 13 (a) and 13 (b) show the relationship between the interference level obtained by the interference detection unit 8 and the threshold value (one threshold value) used by the reliability judgment unit 9. ing.
- FIG. 13 (a) shows a case where the effects of disturbance A and disturbance B on the OFDM signal are not so large. At this time, it is shown that a certain difference exists between the output level of the interference detection unit 8 and the threshold value near the positions f A and ⁇ B on the frequency axis. Therefore, the comparing section 92 can easily detect the presence of both the disturbances ⁇ and ⁇ and appropriately determine the reliability level for each.
- FIG. 13 (b) shows a case where the influence of the disturbance A on the OFDM signal is considerably larger than the influence of the disturbance B on the OFDM signal.
- comparison section 92 can easily detect the presence of both jammer A and jammer B and appropriately determine the level of reliability for each.
- the effect of frequency selective interference is not compared with the value of the interference level, that is, the average value of the interference level itself over the entire carrier, as in the prior art. This is because a comparison is made with a reference value that is unlikely to cause a level change even when the signal is received, that is, a threshold value obtained from the average power of the transmission line characteristics for all carriers.
- the processing in the demodulation unit 5A in FIG. 14 is synchronized with the received signal. Any processing may be used as long as it performs wave or differential detection and outputs a demodulated signal.
- the processing in the reference value calculation unit 7A is such that a level change does not easily occur even if it is affected by frequency selective interference, and a signal that can follow power line fluctuations can be calculated from the received signal. If so, the internal processing can be anything.
- a carrier before demodulation is input as in a reference value calculation unit 7A, and as shown in FIG. 15, a power calculation unit 7A inside the reference value calculation unit 7A is used.
- a signal obtained by averaging the power of the carrier before demodulation over all carriers by 1 and the average calculation unit 7A2 may be used as a reference value.
- the average power is obtained from the signal obtained only from the time axis interpolation by omitting the frequency axis interpolation.
- the reference value may be used, or the average power may be obtained from a signal obtained only from the frequency axis interpolation by omitting the time axis sampling, and may be used as the reference value.
- it may be obtained from any of a signal obtained after demodulation or in the process of demodulation or a signal obtained in the process of interference detection.
- any internal processing may be used as long as the carrier receiving the frequency selective interference and the interference level can be detected.
- the jammer detector 8A receives the output of the demodulator 5A as input, and internally calculates the variance of the constellation of each carrier to determine the carrier suffering frequency selective interference. And so on. Further, a certain level before demodulation may be obtained from any of a signal obtained in the process of demodulation or a signal obtained in the process of reference calculation.
- the demodulation and reference calculation processes in Embodiment 1 described above include a common processing step, that is, a process of obtaining the channel characteristics for all carriers by interpolating the channel characteristics for the pilot signal. Since these are common to both, the demodulation unit 5 and the reference value calculation unit 7 have a configuration in which some components are shared as shown in FIG.
- demodulation section 5 and reference value calculation section 7 are different from those in the first embodiment. You can. For example, when performing the division of a complex signal in the complex division unit 56 in FIG. 1, when performing the sum of squares of the output of the frequency axis interpolation unit 55, that is, when performing the division operation using power, this square
- the configuration may be such that the sum is input to the average calculation unit 72, and in this case, the power calculation unit 71 becomes unnecessary.
- a reference value which is not easily affected by the frequency selective interference is obtained, Since the reliability of each carrier is determined by comparing this reference value with the detected interference, it is necessary to prevent the detection of small-effect interference from being missed due to the presence of relatively high-impact interference. it can. Furthermore, even when there is a change in transmission line characteristics such as fading, a reference value that adapts to this is obtained. / Also, appropriate calculation of reliability level is possible. As a result, it is possible to perform error correction based on an appropriate reliability level for a carrier that has been subjected to frequency selective interference, and to prevent performance degradation of demodulation error correction.
- the second embodiment corresponds to the invention described in Claims 2, 6 to 12, and 18.
- a so-called floor that is, a frequency If there is a tail in the characteristic, the floor is removed and frequency selective interference is detected to prevent malfunction due to the influence of the floor.
- a receiving device Similar to Embodiment 1, a case will be described where the multicarrier receiving apparatus according to the present invention is applied to an apparatus that receives an OFDM transmission signal.
- FIG. 16 is an overall configuration diagram of the multicarrier receiving apparatus according to the second embodiment.
- components having the same processing contents as those in the first embodiment are denoted by the same reference numerals as in FIG. 1, and description thereof will be omitted.
- Embodiment 2 differs from Embodiment 1 in that a disturbance average calculation unit 10 is provided between the disturbance detection unit and the reliability determination unit, and the internal processing of the reliability determination unit is performed in Embodiment 1.
- the feature is that it is different from the above.
- any input signal or internal configuration may be used as long as it shows a peak of the interference level near the position on the frequency axis subjected to frequency selective interference. Good.
- an interference detection unit 8B that calculates an interference level from a signal to which a signal after FFT is input is provided.
- a peak appears at a position on the frequency axis where frequency-selective interference exists, but depending on its internal processing, frequency selectivity such as Gaussian noise interference may occur at other positions. Some floors may be caused by other disturbances.
- the interference average calculation unit 10 estimates the above-mentioned flow from the interference level obtained from the interference detection unit 8B, and outputs it to the reliability determination unit 9A as the interference average level.
- the reliability determination unit 9A compares the interference level from the interference detection unit 8B with the interference average level from the interference average calculation unit 10, and indicates a carrier level that indicates an interference level higher than the interference average level. Are judged to be suffering frequency-selective interference, and the reliability level is determined stepwise for those carriers based on the reference value obtained from the reference value calculation unit 7. Output.
- the reference value calculating section 7, the interference detecting section 8B and the interference average calculating section 10 are the second step and the third step in the receiving method according to claim 18 of the present invention.
- the reliability determination unit 9A performs a process corresponding to the fifth process
- the error correction unit 6 performs a process corresponding to the sixth process.
- the reliability level is determined as it is for the interference level where this floor exists, the reliability level of the carrier on the floor part caused by causes other than frequency selective interference except for the vicinity of the position f A will be excessively lowered. This can lead to a deterioration in the overall error rate.
- the disturbance average calculation unit 10 estimates the floor based on the average value of the disturbance levels, and outputs the estimation result to the reliability determination unit 9A as the disturbance average level.
- Reliability judging unit 9A judges the reliability level for carriers that show an interference level higher than the average interference level. As a result, it is possible to appropriately measure the degree of reliability of a carrier that has undergone frequency selective interference that should be evaluated.
- interference A and interference B which are frequency-selective interferences having different influences on the received signal, are received simultaneously, and exist near positions fA and fB on the frequency axis, respectively.
- the average value (assumed to be a Vg1) is obtained for the entire carrier regardless of the level of the interference, the overall value is pulled by the interference A, which has a large effect.
- the average value a V g 1 increases. If the average value a V g 1 itself is used as the interference average level, and if a carrier having an interference level higher than this average interference level is determined for reliability, the effect is relatively small, equivalent to the average value a V g 1. It overlooks the presence of jammer B, which results in a reduced error rate.
- the interference average calculation unit 10 estimates the floor based on the average value of the interference levels, and the interference level of the carrier subjected to the frequency selective interference having a strong influence shows a very large value. Therefore, it is characterized in that such a very large interference signal is excluded from the average calculation target. For example, as shown in Fig. 18, a threshold value is prepared, and carriers having an interference level exceeding this threshold value are excluded from the average calculation. As a result, an average value (avg 2) that suppresses the increase in the average value due to the presence of a relatively large interference level is obtained, and this makes it possible to estimate an appropriate floor.
- the reliability determination unit 9A can appropriately calculate the reliability level from the interference level with respect to the relatively small influence and the interference.
- the interference average calculator 10 according to the second embodiment will be described in detail.
- the disturbance average calculation unit 10 may include a threshold setting unit 101, a comparison unit 102, and a conditional average calculation unit 103. .
- the threshold value setting unit 101 may set a threshold value (first threshold value) based on the reference value obtained by the reference value calculation unit 7. This threshold value is used together with the threshold value (second threshold value) of the threshold value setting unit 9A2 of the reliability judgment unit 9A and the value of the experimenter so as to minimize the error rate of the received signal while comparing it with the interference level. You can set it.
- the reference value obtained by the reference value calculation unit 7 may be P
- a predetermined coefficient may be ⁇
- a threshold value may be set by the product P ⁇ ⁇ .
- the reference value obtained by the reference value calculation unit 7 follows the fluctuation of the transmission line characteristics and is hardly affected by the power frequency selective disturbance.
- the threshold value set by the threshold value setting unit 101 also changes the transmission line characteristics. It is possible to obtain a threshold that follows fluctuations and is not easily affected by frequency selective interference.
- the first threshold may be a fixed value.
- the comparison unit 102 compares the interference level obtained by the interference detection unit 8 ⁇ with the threshold value obtained by the threshold setting unit 101 (first comparison), and the result is sent to the conditional average calculation unit 103. Notice.
- the conditional average calculation unit 103 determines that the interference level exceeds the threshold based on the comparison result output by the comparison unit 102. Is excluded from the target of the average calculation, and if not, the interference level is the target of the average calculation. At this time, the average value may be calculated by integrating the interference level over the frequency domain and the time domain. As a result, even if there is a carrier whose interference level is extremely large, the floor of the interference level can be appropriately estimated without being affected by the carrier.
- the calculation result of the conditional average calculation unit 103 is supplied to the reliability determination unit 9A as an interference average level.
- the interference levels exceeding the threshold are not excluded from the target of the average calculation, but the interference levels are replaced with predetermined representative values. May be used to calculate the average).
- the threshold value used in the interference average calculation unit 10 does not need to be one, and a plurality of threshold values are prepared. You may.
- the calculation accuracy of the average interference level can be varied according to the number of thresholds to be set, and the average interference level can be calculated more accurately by preparing a large number of threshold values, and the carrier subjected to frequency selective interference can be more accurately determined.
- the demodulation error correction capability can be further improved.
- N predetermined coefficients j3 1, ⁇ 2, ⁇ 3,..., ⁇ ⁇ (> 1) are prepared, and the product of these coefficients and the reference value ⁇ , P. J31, V ⁇ ⁇ 2, ⁇ ⁇ / 3 3, ..., ⁇ ⁇ ] 3 ⁇ ⁇ may be set as the threshold value, and the floor can be more reliably removed, so that the demodulation error correction capability can be further improved.
- the magnitude relationship between the interference level and each threshold value may be compared, and replaced with a predetermined representative value in a stepwise manner according to the value of the interference level (correction), and used for calculating the average value. Also according to this, the floor can be more reliably removed, and as a result, the demodulation error correction capability can be further improved.
- the disturbance average calculator 10 compares the disturbance level obtained by the disturbance detector 8 ⁇ with the threshold obtained by the threshold setting unit 101 (first comparison), and based on the comparison result, Select the interference level for calculating the average value, calculate the average value of the interference level selected by the selection, and raise the value by multiplying the average value of the average interference level by a predetermined coefficient.
- the average value obtained may be output as the interference average level.
- the interference average calculator 10 since the position and magnitude on the frequency axis where frequency selective interference such as co-channel interference of an analog TV signal exists is not known and processed, There is an effect that the position and magnitude of the protruding interference level are adaptively detected regardless of the type and position of the interference, and the average interference level can be calculated optimally according to those values.
- the reliability determination unit 9A determines a carrier that has received frequency-selective interference based on the interference level and the average level of interference, and determines the difference level between the carrier that has been determined to have received frequency-selective interference and the second level. A third comparison is made with respect to the threshold value.Based on the result of the third comparison, the reliability of a plurality of carriers is determined in a stepwise manner and output as a reliability level. As shown in the figure, the interference level correction section 9 A1 and the threshold setting section 9 A2, a comparison unit 9A3, and a reliability level determination unit 9A4 may be used.
- the interference level correction unit 9A1 performs a comparison (second comparison) by calculating a difference level between the interference level from the interference detection unit 8B and the interference average level from the interference average calculation unit 10; For carriers that show an interference level higher than the average interference level, it is determined that they have received frequency-selective interference, and the input interference level is output as it is. The value shown, for example, the disturbance level is corrected to a value such as "0", and the result is output to the comparator 9A3 as the disturbance level after the correction.
- the interference level detection unit 9A1 compares the interference level from the interference detection unit 8B with the average interference level from the average interference calculation unit 10, and determines the interference level that exceeds the average interference level.
- the determined carrier is judged to have received frequency-selective interference, and the difference between the interference level and the average interference level is calculated.
- ⁇ No frequency-selective interference '' May be corrected to a value such as "0" as the interference level, and the result may be output as the interference level after correction to the comparison 59 A3.
- the threshold value setting unit 9A2 sets a predetermined threshold value (second threshold value) based on the reference value obtained by the reference value calculation unit 7, and outputs the threshold value to the comparison unit 9A3.
- the reference value obtained by the reference value calculation unit 7 may be P
- the predetermined coefficient may be V
- the threshold may be set by the product P ⁇ V. Since the threshold setting unit 9A2 sets the threshold based on the reference value obtained by the reference value calculation unit 7, it is possible to follow a change in the transmission line characteristics and obtain a threshold that is not easily affected by frequency selective interference. I can do it.
- the number of thresholds may be one or more.
- the comparison unit 9A3 compares the interference level after correction obtained by the interference level correction unit 9A1 with the threshold value obtained by the threshold setting unit 9A2 (third comparison) for each carrier. The result of the comparison with the threshold is output to the reliability level judgment unit 9A4. At this time, for example, for 3 ⁇ 4 ⁇ with one threshold value, a force is determined to determine whether the result obtained by the interference level correction unit 9A1 exceeds the threshold value and output. If there are multiple thresholds, the interference level 9 A1 Determines the threshold between which the result obtained in 1 is located and outputs it.
- the reliability level determining unit 9A4 determines a reliability level for each carrier according to the result obtained by the comparing unit 9A3, and outputs the result to the error correcting unit 6.
- the reliability level may be represented by two values of the presence or absence of interference.
- the reliability level may be expressed as, for example, three or more values in multiple levels, and the reliability level can be calculated flexibly according to the interference level. The demodulation error correction capability can be further improved.
- the reliability determination unit 9A when determining the degree of the interference level, a signal that is not easily affected by frequency selective interference is used as a reference. ing. Therefore, it is necessary to determine an appropriate reliability level according to the interference level not only for received signals in which multiple frequency-selective interferences with different degrees of influence exist, but also for interferences with relatively small effects. You can do it.
- the reference signal used to determine the level of the interference level can follow the fluctuations in the transmission line characteristics, an appropriate reliability level can be calculated even in a reception environment where the transmission line characteristics fluctuate. Is possible.
- the interference level is compared with the interference average level, which indicates the estimated result of the floor!
- the reliability level can be calculated for a carrier that has frequency-selective interference, excluding the effect of the floor, thereby preventing the error rate from deteriorating.
- the threshold value set in the interference average calculator 10 is a predetermined fixed value.
- the threshold value set by the reliability judgment unit 9A is a fixed value.
- the threshold value may be a fixed value in both the disturbance average calculation unit 10 and the reliability determination unit 9A, or only one of the threshold values may be a fixed value, and the other may be a reference value obtained by the reference value calculation unit ⁇ . The threshold may be determined based on the threshold.
- the threshold value used in both the disturbance average calculation unit 10 and the reliability judgment unit 9A is a fixed value, the components used only to obtain the reference value in the reference value calculation unit 7 (In the case of FIG. 16, the power calculator 71 and the average calculator 72) are of course unnecessary.
- the interference detector 8 A difference may occur between the interference level obtained in B and the average value (a V g) of the interference levels obtained in the interference average calculator 10.
- the average value of the interference level itself is used as the interference average level, and if the reliability of a carrier having an interference level higher than the average interference level is determined, the Gaussian noise (other than frequency selective interference) can be determined. Interference can cause a carrier that exhibits an interference level above the average interference level to be too unreliable.
- an interference average calculation section 10A shown in FIG. 20 may be used instead of the interference average calculation section 10. This is obtained by adding a disturbance average correction unit 10 A 1 to the disturbance average calculation unit 10.
- a threshold value may be input to the threshold value setting unit 101, and a threshold value may be set based on the reference value. If a reception environment where transmission line characteristics change relatively little is assumed, A fixed value may be output.
- the average value of the interference level is often proportional to the power of the Gaussian noise, and the difference between the interference level and the average value is often proportional to the power of the Gaussian noise.
- the disturbance average correction unit 10A1 may perform the correction by multiplying the output of the conditional average calculation unit 103 by a predetermined coefficient, for example, y ( ⁇ 1).
- y ⁇ 1
- the average interference level is raised from the value before correction, and the average interference level that cancels out the effect of the Gaussian noise can be obtained.
- the second embodiment similarly to the first embodiment, when receiving a signal subjected to a plurality of frequency-selective disturbances having different degrees of influence, it is affected by the frequency-selective disturbance. Since a difficult reference value is determined and the reliability of each carrier is determined by comparing this reference value with the detected interference, the detection of small-effect interference may be missed due to the presence of relatively high-impact interference. Can be prevented. Further, similarly to Embodiment 1, even when there is a change in transmission path characteristics such as fading, a reference value adapted to the change is obtained and compared with the interference level. Appropriate calculation of the reliability level is possible even if it is described below.
- the floor is estimated from the average value of the interference level and used as the average interference level.
- the effect of the floor can be eliminated and the reliability level can be determined only for carriers that have received frequency-selective interference. It can prevent the error rate from deteriorating.
- the degree and position of the influence are detected adaptively and excluded from the average. By doing so, it is possible to estimate the floor properly, and to prevent the detection of interference with relatively small influence when receiving signals with multiple frequency-selective interference with different degrees of influence. .
- the position and magnitude on the frequency axis where frequency selective interference (such as co-channel interference of an analog TV signal) exists is not processed as known, There is an effect that the position and magnitude of the protruding interference level can be detected adaptively regardless of the type and position of the interference, and the average interference level can be calculated optimally according to those values.
- the second embodiment The configuration and internal processing of the demodulation unit 5, reference value calculation unit 7, interference detection unit 8B, interference average calculation unit 10, and reliability judgment unit 9A are always the same as described above. No need. As described in the first embodiment, any of these internal processes may be used as long as they can output a signal according to each purpose.
- the received signal is not limited to this, and a plurality of carriers may be provided by adopting a necessary configuration according to the signal to be received. Accordingly, the present invention can be applied to other devices that receive an FDM signal that has been frequency-division multiplexed.
- Embodiment 3 corresponds to the invention described in Claims 3, 13 to 15, and 19, and relates to a case where the multicarrier receiver is mounted on a mobile object. In cases such as when a high level of interference is exhibited over all carriers due to the effects of fading, etc., the effects of fading are eliminated by performing correction so as to increase the level of reliability of the carriers. Things. Embodiment 3 of the present invention will be described. As in the second embodiment, a case will be described in which the multicarrier receiving apparatus according to the present invention is applied as an apparatus that receives an OFDM transmission signal.
- FIG. 21 is an overall configuration diagram of the multicarrier receiving apparatus according to the third embodiment.
- components having the same processing contents as those of the second embodiment are denoted by the same reference numerals as in FIG. 7, and description thereof is omitted.
- the third embodiment is different from the second embodiment in that an interference determination unit 11 is provided between the interference average calculation unit 10B and the reliability determination unit 9C, and the reliability determination unit 9C is provided.
- the internal processing is different from that of the reliability determination unit 9A of the second embodiment.
- the configuration of the input signal ⁇ ⁇ unit may be any configuration as long as the average value of the interference level obtained by the interference detection unit is obtained.
- a unit that calculates the average value of the interference levels from the interference detection unit 8B is provided as the interference average calculation unit 10B.
- the interference determination unit 11 selects the frequency of the received signal from the average value of the interference levels (interference average level) obtained from the interference average calculation unit 10B and the reference value obtained from the reference value calculation unit 7.
- the degree of influence of sexual disturbance is determined stepwise, and the determination result is reported to the reliability determination unit 9C as a disturbance determination level.
- the reliability determination unit 9C determines a reliability level for each carrier based on the interference level of the interference detection unit 8B and the reference value from the reference value calculation unit 7, and then determines the interference determination unit 11 The reliability level is corrected based on the interference determination level obtained in step (1) and output to the error correction unit (6).
- the reference value calculation unit 7, the interference detection unit 8B, the interference average calculation unit 10B, and the interference determination unit 11 are configured to receive the signal according to claim 19 of the present invention.
- the reliability determination unit 9C performs the sixth step
- the error correction unit 6 performs the seventh step. Each performs corresponding processing.
- Embodiment 3 will be described in more detail.
- the Doppler frequency is used as an index indicating the amount of fluctuation of a received signal due to fading.
- the interference level which is the output
- the higher the Doppler frequency the higher the value and the higher the average value may be. This situation is high only near a position on a specific frequency axis! This is significantly different from the case where the frequency selective disturbance showing the / ⁇ peak was received.
- the reliability level is calculated when the average value of the interference levels for all the carriers is excessively increased beyond a predetermined value due to fading interference or the like which is not the original target of the detection purpose.
- the system is characterized by applying a certain amount of correction to prevent the overall reliability of the carrier from becoming too low. In this way, when a high level of interference is exhibited over all the carriers, there is an effect of preventing the signal reproduction of all the carriers from becoming too low, and thereby reducing the error rate as a whole.
- a signal that is less susceptible to frequency-selective interference and that adapts to fluctuations in transmission path characteristics such as fading is used as a criterion for determining the average value of the interference level. Appropriate determination of the interference level is possible even in a reception environment where the road characteristics fluctuate.
- the interference average level is calculated by the interference average calculation unit 1 OB, and the threshold and the interference average level are set by the interference determination unit 11 based on the reference value obtained by the reference value calculation unit 7. And outputs the comparison result to the reliability determination unit 9C as the interference determination level.
- the reliability determination unit 9C makes a certain correction to the reliability level calculated based on the interference determination level. It is characterized by multiplying.
- the interference determination unit 11 may be composed of a threshold setting unit 111 and a comparison unit 112, for example, as shown in FIG.
- the threshold value setting unit 111 sets a threshold value (third threshold value) using the reference value from the reference value calculation unit 7 as a disturbance detection reference value.
- the threshold value is set so that the credibility of the entire carrier is too low due to fading interference and the error rate is low.
- the value may be determined so as not to degrade, and the threshold value is obtained by multiplying the reference value P by a predetermined coefficient ⁇ ;
- the threshold value does not need to be one, and a plurality of values such as ⁇ ⁇ ⁇ ⁇ 1, ⁇ ⁇ ⁇ 2,... May be prepared using predetermined coefficients ⁇ 1, ⁇ 2,.
- the threshold value may be set to a predetermined value in advance to eliminate the need for the calculation process.
- a large number of fixed threshold values may be used to prevent interference.
- the decision level can be calculated with higher accuracy, and the demodulation error correction capability can be further improved with respect to fading interference.
- a predetermined value may be set in advance as the interference determination reference value as the reference value.
- the comparison unit 112 compares the disturbance average level obtained by the disturbance average calculation unit 110 ⁇ with the threshold value obtained by the threshold setting unit 111 (fourth comparison), and compares the result with reliability. Notify judgment section 9C. For example, if the number of thresholds is one, it may be determined in two stages whether or not the average disturbance level exceeds the threshold. When there are a plurality of thresholds, it is determined which of the thresholds the interference average level is between, and the result is notified to the credibility determination unit 9C as an interference determination level. When there are a plurality of thresholds, the interference determination level may be expressed as a multi-step value of, for example, three or more levels, and may be output.This allows flexible calculation of the interference determination level according to the average interference level. The demodulation error correction capability can be further improved for fading interference.
- the reliability judging unit 9C includes a threshold setting unit 9C1, a comparing unit 9C2, a reliability level judging unit 9C3, a reliability level correcting unit 9C4, and a power.
- the threshold setting unit 9 C 1, the comparison unit 9 C 2, and the reliability level determination unit 9 C 3 include the threshold setting unit 91 of the reliability determination unit 9 and the comparison unit 9 2 in the first embodiment.
- the reliability level determination unit 93 may have the same configuration, and detailed description will be omitted.
- a reference value that is less susceptible to frequency-selective interference is determined, and a threshold (fourth threshold) set based on this reference value is compared with the detected interference (fifth comparison).
- a threshold fourth threshold set based on this reference value is compared with the detected interference (fifth comparison).
- the reliability level correction unit 9 C 4 is provided with an error correction unit 6 according to the interference determination level obtained from the interference determination unit 11 in order to prevent the reliability of the entire carrier from being excessively reduced in a fading environment or the like.
- the output of the reliability level determination unit 9C3 is corrected so as to prevent the reliability level output to the CPU from becoming too low. For example, when a signal indicating that the average interference level exceeds a predetermined threshold value due to fading interference or the like is obtained from the comparison unit 112, the reliability level determination unit 9C3 outputs the carrier reliability. Is raised by one level, for example, to perform processing to prevent the reliability level from becoming too low.
- the reliability level obtained after the level correction is output to the error correction unit 6.
- the reliability determination unit 9C corrects the reliability level according to the interference determination level obtained from the interference determination unit 11, but instead obtains the correction from the interference determination unit 11.
- a process is performed to increase the threshold value for determining the interference level so as not to lower the reliability level after the correction too much.
- each carrier Since the reliability of each carrier is determined by comparing the detected interference with the detected interference, it is possible to prevent the detection of a small-impact interference from being missed due to the presence of a relatively high-impact interference. Further, similarly to Embodiment 1, even when there is a change in transmission path characteristics such as fading, a reference value adapted to the change is obtained and compared with the interference level. Even below, an appropriate calculation of the reliability level becomes possible.
- the receiving apparatus using the third embodiment it is particularly effective in a receiving environment in which fusing interference is expected, such as mounting on a mobile body for reception.
- the configuration and internal processing of the demodulation unit 5, the reference value calculation unit 7, and the interference detection unit 8B are not necessarily the same as described above. Need not be. As described in the first embodiment, these internal processes may be any as long as they can output a signal according to each purpose.
- Embodiment 2 and Embodiment 3 An example of a combination of Embodiment 2 and Embodiment 3 is shown in FIG. In FIG. 23, the same components as those used in FIGS. 16 and 21 are denoted by the same reference numerals, and detailed description thereof will be omitted. In this case, the internal processing of the reliability judging unit shown in the second embodiment and the third embodiment is combined and provided as a reliability judging unit 9D.
- the reliability determination unit 9D includes an interference level / level correction unit 9D1, a threshold setting unit 9D2, a comparison unit 9D3, a reliability level determination unit 9D4, and a reliability level correction unit 9. D5.
- the interference level correction unit 9D1 is the same as the interference level correction unit 9A1 in the reliability determination unit 9A of the second embodiment, and includes a threshold setting unit 9D2, a comparison unit 9D3, Regarding the reliability level judging unit 9D4 and the individual signal level correcting unit 9D5, the threshold setting unit 9C1 of the reliability judging unit 9C in the third embodiment, the comparing unit 9C2,
- the reliability level determination section 9C3 and the reliability level correction section 9C4 may have the same configuration.
- the interference level when calculating the average interference level by calculating the average of the interference detection results (interference level), the interference level is compared with a predetermined reference value, and for a carrier that shows a very large interference level, The degree of influence and the position are adaptively detected, and the average value is calculated as an interference average level excluding from the average, and a carrier having an interference level higher than the interference average level is determined based on the predetermined reference value. Judgment is made in stages to calculate the reliability level. Further, the average interference level is determined stepwise based on the predetermined reference value, and the reliability level is appropriately corrected based on the determination result. And outputs the result to the error correction unit.
- the floor is estimated from the average value of the interference level, and the average interference level is obtained.
- the degree and position of the influence are detected adaptively and excluded from the average. This makes it possible to properly estimate the floor, and when signals receiving multiple frequency-selective disturbances with different degrees of influence are received, the effect of preventing missed detection of relatively small-effects interference Also joins.
- Embodiment 3 describes an application example in which an OFDM signal is received, the received signal is not limited to this, and a plurality of carriers can be provided by adopting a necessary configuration according to the signal to be received. Accordingly, the present invention can be applied to other devices that receive an FDM signal that has been frequency-division multiplexed. Industrial applicability
- the present invention improves the deterioration of demodulation performance due to frequency selective interference such as spurious and co-channel interference when receiving an FDM signal, and also reduces the floor due to frequency selective interference due to Gaussian noise and the like. If it is present, the effect of the floor is eliminated to suppress malfunctions.Furthermore, when the receiver is mounted on a mobile unit, malfunctions occur assuming that the effects of fading are caused by interference over all carriers. It is suitable for use in applications that suppress odor.
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Description
Claims
Priority Applications (5)
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BR0303345-7A BR0303345A (pt) | 2002-04-15 | 2003-04-15 | Aparelho de recepção e método de recepção |
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US10/476,584 US7424072B2 (en) | 2002-04-15 | 2003-04-15 | Receiving apparatus and receiving method |
EP03723113A EP1499052A4 (en) | 2002-04-15 | 2003-04-15 | RECEIVER AND RECEIVING METHOD THEREOF |
US12/193,197 US7653162B2 (en) | 2002-04-15 | 2008-08-18 | Receiving apparatus and receiving method |
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Also Published As
Publication number | Publication date |
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US7653162B2 (en) | 2010-01-26 |
JPWO2003088538A1 (ja) | 2005-08-25 |
US20040208138A1 (en) | 2004-10-21 |
EP1499052A1 (en) | 2005-01-19 |
TW200307432A (en) | 2003-12-01 |
US20090052564A1 (en) | 2009-02-26 |
US7424072B2 (en) | 2008-09-09 |
JP4299148B2 (ja) | 2009-07-22 |
BR0303345A (pt) | 2004-08-10 |
EP1499052A4 (en) | 2008-07-16 |
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