JP2011199391A - Response estimator of transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a delayed wave whose power level is low, and obtain a delayed profile of high precision.SOLUTION: An estimator is characterized to be provided with: a correlation unit 11 which inputs a received signal of a frame composition including a known pattern, calculates time correlation of a reference signal of the same pattern of the known pattern and a received signal, and outputs the correlation value; a time distance detection unit 13 which obtains a time distance of the output of the correlation unit making the maximum peak position of the correlation value in a frame period of the received signal as a standard, and outputs the time distance information; a threshold value creation unit 14 which creates the threshold value corresponding to a change of the correlation value calculated by the correlation unit based on the maximum peak position and the time distance information; and an effective path discrimination unit 12 which obtains a detection result of the effective delayed wave based on the correlation level by comparing the correlation value from the correlation unit with the threshold value, and outputs the detection result as the delayed profile.

Description

  The present invention relates to a transmission path response estimator in a broadcast and wireless communication reception system.

  In general, in a broadcasting system and a wireless communication system, a radio signal transmitted from a transmission station is reflected, scattered, or diffracted by terrain or a building or the like while reaching the receiver, and becomes a plurality of radio signals to the receiver. To reach. When the receiver receives the same radio signal that has followed these multiple paths, the received signals may be combined with each other and the waveform may be distorted.

  This phenomenon is generally called multipath, and the path followed by each wireless signal is called a multipath transmission path (hereinafter also simply referred to as a path).

  Therefore, in the receiver, processing for reproducing the current waveform of the radio signal transmitted from the transmitting station is performed from the received signal whose waveform is distorted. This processing is generally called equalization processing.

  In general, distortion components generated in a multipath transmission line can be expressed as a filter response when an impulse is used as an input signal, and accurately estimating this transmission line response improves the accuracy of the receiver equalization process. Connected. This transmission line response is generally called a delay profile.

  In a multipath environment, the received signal is a composite wave of a main signal (main wave) and a multipath delayed signal (delayed wave). The transmission path response estimator obtains a correlation waveform having a maximum peak at the timing of the main wave frame header and a small peak at the timing of the frame header of the delayed signal. The peak position in the correlation waveform corresponds to the main wave and delayed wave paths.

  In general, a certain threshold is set for such a correlation waveform, and the peak portion that does not satisfy the threshold is deleted as noise from the correlation waveform, and only the peak portion that exceeds the threshold is set as the main wave and the delayed wave. Select it as a corresponding effective path and output it as a delay profile. The reception quality is improved by performing waveform equalization using the delay profile.

  As a method for setting the threshold value, Patent Document 1 proposes a method for switching the threshold value according to the status of the wireless communication channel, the type of service, the modulation method, and the like.

  However, even if the technique disclosed in Patent Document 1 is used, if there is a delayed signal that is relatively close to the main wave and has relatively low power, the path corresponding to this delayed signal can be detected as an effective path. As a result, there is a problem that the channel estimation accuracy deteriorates, and the reception quality deteriorates.

JP 2004-23763 A

  It is an object of the present invention to provide a transmission path response estimator that can enable highly accurate transmission path response estimation even in a multipath environment where a delayed signal with relatively low power exists.

  The transmission path response estimator according to one aspect of the present invention receives a received signal having a frame configuration including a known pattern, calculates a time correlation between the reference signal having the same pattern as the known pattern and the received signal, and obtains a correlation value. A correlation unit that outputs, a time distance detection unit that obtains a time distance of the output of the correlation unit based on a maximum peak position of the correlation value in a frame period of the received signal, and outputs time distance information; and the maximum By comparing the correlation value from the correlation unit with the threshold value, a threshold value generation unit that generates a threshold value corresponding to the change in the correlation value calculated by the correlation unit based on the peak position and the time distance information. And an effective path determination unit that obtains an effective delay wave detection result based on the level of the correlation value and outputs the detection result as a delay profile.

  In addition, a transmission path response estimator according to another aspect of the present invention receives a received signal having a frame configuration including a known pattern, and calculates a time correlation between the reference signal having the same pattern as the known pattern and the received signal. A correlation unit that outputs a correlation value and a time distance of output of the correlation unit for each peak position based on a peak position of one or more correlation values that are equal to or greater than a predetermined threshold are output. A time distance detection unit; a threshold value generation unit that generates a threshold value corresponding to a change in the correlation value calculated by the correlation unit based on the time distance information for each peak position; and the threshold value generation unit. A delay unit effective based on the level of the correlation value by comparing the correlation value from the correlation unit with the synthesis threshold value by combining the threshold value for each peak position generated by Inspection The results give, characterized by comprising an effective path judgment unit which outputs the detection result as a delay profile.

  According to the present invention, there is an effect that it is possible to enable highly accurate transmission path response estimation even in a multipath environment where a delay signal with relatively low power exists.

The block diagram which shows the transmission-line response estimator which concerns on the 1st Embodiment of this invention. Explanatory drawing for demonstrating the correlation detection of the correlation part 11 in FIG. The timing chart for demonstrating the detection of a frame synchronizing signal in case the delay signal (delayed wave) by multipath is included. Explanatory drawing which shows a delay profile in case the threshold value of the effective path determination part 12 is constant. Explanatory drawing for demonstrating operation | movement of 1st Embodiment. The block diagram which shows the 2nd Embodiment of this invention. The block diagram which shows the 3rd Embodiment of this invention. The block diagram which shows the 4th Embodiment of this invention. Explanatory drawing which shows a correlation waveform. Explanatory drawing for demonstrating the operation | movement of 4th Embodiment. The block diagram which shows the 5th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a transmission path response estimator according to the first embodiment of the present invention.

  The received signal is input to the correlation unit 11. The received signal is a signal having a frame structure in which a specific known pattern is periodically inserted. For example, as such a received signal, there is DTMB (Digital Terrestrial Multimedia Broadcast) of the Chinese (People's Republic of China) terrestrial digital broadcasting standard. In DTMB, a frame is composed of a frame body and a frame header. The frame body stores 3780 symbols in which modulated source stream data and system information are combined. The frame header stores a known PN sequence for identifying the frame.

  The correlation unit 11 also receives a reference signal having the same pattern as the known pattern included in the received signal. The correlation unit 11 calculates a time correlation between the received signal and the reference signal.

  FIG. 2 is an explanatory diagram for explaining the correlation detection of the correlation unit 11 in FIG. FIG. 2A shows a correlation detection method, and FIG. 2B shows a correlation detection result.

  FIG. 2A shows a signal frame (hereinafter simply referred to as a frame) in which a frame header as a known pattern and a frame body as a data body are periodically inserted as a received signal. The reference signal is a signal having the same pattern as the frame header.

  The correlation unit 11 calculates a sliding complex time correlation while shifting the reference signal by one symbol from the received signal. As shown in FIG. 2B, the correlation value between the received signal and the reference signal has a peak at the timing when the symbol of the reference signal and the symbol of the frame header completely match, and the level of the correlation value at other timings. Is sufficiently low and noisy. In this way, the correlation unit 11 outputs a correlation waveform having a peak portion and a noise-like portion as shown in FIG.

  Note that in a receiving apparatus in which a transmission path response estimator is incorporated, a frame synchronization signal is generated at a timing when the correlation value between the received signal and the reference signal peaks. The frame synchronization signal may be a pulse or a number indicating timing.

  FIG. 3 is a timing chart for explaining detection of a frame synchronization signal when a delay signal (delayed wave) due to multipath is included.

  In FIG. 3, a delayed wave is multiplexed by the multipath on the main wave of the received signal. A delayed wave frame header is received after a predetermined time delay from the main wave. The correlation value between the received signal (delayed wave) and the reference signal peaks at the timing when the symbol of the delayed wave frame header and the symbol of the reference signal completely coincide. Accordingly, the correlation value peak based on the delayed wave appears at the output of the correlation unit 11 after a predetermined time delay from the correlation value peak detected based on the main wave.

  In general, in multipath, the power of the main wave is sufficiently larger than the power of the delayed wave. Therefore, the peak of the correlation value based on the main wave has a sufficiently higher power level than the peak of the correlation value based on the delayed wave. Due to the difference in power level, the peak of the correlation value based on the main wave can be detected separately from the peak of the correlation value based on the delayed wave.

  Each peak of the correlation waveform between the received signal and the reference signal corresponds to each path in the multipath, and the distance between the peaks corresponds to the delay time of the delayed wave. Since a delay profile can be obtained by detecting the peak of the correlation waveform, hereinafter, the peak on the correlation waveform is also referred to as a path or a delay wave.

  The output (correlation waveform) of the correlation unit 11 is supplied to the effective path determination unit 12. The effective path determination unit 12 is given a threshold value from the threshold generation unit 14 and compares the correlation waveform with the threshold value to select only the peak portion of the correlation waveform as an effective path corresponding to the main wave and the delayed wave. And output as a delay profile. In order to extract only the peak portion of the correlation waveform, it is necessary to set a threshold value higher than the level of the noise-like portion other than the peak portion as the threshold value of the effective path determination unit 12.

  FIG. 4 is an explanatory diagram showing a delay profile when the threshold of the effective path determination unit 12 is constant. FIG. 4A shows a correlation waveform when a reception signal in which a main wave and one delay wave are multiplexed is received, and FIG. 4B shows a delay profile.

  When a reception signal including a main wave and one delayed wave is received, the output of the correlation unit 11 is as shown in FIG. That is, in this case, a correlation waveform having a path based on the main wave and a path based on a delayed wave delayed for a predetermined time from this path is obtained. The peak level of the correlation waveform corresponds to the power levels of the main wave and delayed wave signals.

  By the way, generally, a pseudo random noise sequence (PN (Pseudo random noise) sequence) is used as the known pattern. When a PN sequence is used, if the correlation between the received signal and the reference signal is obtained at a symbol position that does not completely match the symbol position in the frame header, the correlation between the reference signal symbol and the frame body symbol Thus, the correlation value increases as the symbol position shifts. In other words, since the variance of the cross-correlation value between the frame body and the reference signal is proportional to the time distance from the main wave, the correlation waveform calculated by the complex time correlation has a variance proportional to the time distance from the main wave. It has the feature of becoming larger.

  FIG. 4A shows this feature. That is, when the PN sequence is adopted as the known pattern, the correlation value increases as the symbol position from the path based on the main wave shifts (FIG. 4A). For this reason, as shown by the broken line in FIG. 4A, when the threshold value is made higher than the level of the noise-like portion, the peak of the delayed wave becomes lower than the threshold value, and as shown in FIG. The peak based on the wave is not detected, and only the peak based on the main wave is detected.

  Therefore, in the present embodiment, the threshold value generation unit 14 sets a threshold value that changes with time so as to be higher than the noise-like portion and lower than the peak portion due to the delayed wave. The threshold generation unit 14 uses a timing at which a peak having a level higher than a predetermined threshold is detected as a temporal reference for changing the threshold. For example, the threshold generation unit 14 uses the timing of the peak having the highest level in the frame, for example, the timing of the frame synchronization signal, as a temporal reference for changing the threshold.

  The frame synchronization signal is given to the threshold value generator 14 and the distance detector 13. For example, the distance detection unit 13 calculates the time distance (for example, symbol unit) of the current output of the correlation unit 11 based on the frame synchronization signal indicating the frame start position of the main wave in the received signal, and generates a threshold value for the calculation result. It outputs to the part 14.

  Based on the frame synchronization signal and the output of the distance detection unit 13, the threshold generation unit 14 adaptively sets a temporally changing threshold so as to be higher than the noise-like portion and lower than the peak portion due to the delayed wave. It is designed to generate. The level of the noise-like part of the correlation value is a value corresponding to the PN sequence. Therefore, the threshold value generation unit 14 can obtain the level of the noise-like portion in advance, for example, by simulation. The threshold generation unit 14 generates a threshold according to the time distance from the path position based on the main wave by adding a predetermined value to the level of the noise-like portion obtained by the simulation.

  The effective path determination unit 12 selects a path based on the correlation waveform from the correlation unit 11 and the threshold supplied from the threshold generation unit 14, and outputs a delay profile with the selected path as an effective path. The valid path determination unit 12 may regard a path that has not been selected as noise, and improve the S / N by setting it to 0 level.

  Next, the operation of the embodiment configured as described above will be described with reference to FIG. FIGS. 5A and 5B are explanatory diagrams for explaining the operation of the first embodiment. FIG. 5A shows a correlation waveform and FIG. 5B shows a delay profile.

  The received signal is given to the correlation unit 11. The correlation unit 11 calculates the sliding complex time correlation while shifting the reference signal by one symbol from the received signal, and outputs the correlation waveform to the effective path determination unit 12.

  On the other hand, a frame synchronization signal generated at a timing corresponding to the peak of the correlation waveform between the main wave and the reference signal in the received signal is input to the distance detection unit 13. The distance detection unit 13 calculates the current time distance of the output of the correlation unit 11 based on the frame synchronization signal corresponding to the frame start position of the main wave, and outputs the calculation result to the threshold generation unit 14.

  The threshold generation unit 14 obtains the level of the noise-like portion excluding the peak portion of the correlation waveform by simulation, and adapts the threshold according to the current time based on the output of the frame synchronization signal and the distance detection unit 13. Generated and output to the valid path determination unit 12.

  FIG. 5A shows a correlation waveform when a reception signal in which one delayed wave is multiplexed on the main wave is received. In the present embodiment, the threshold value generator 14 sets a threshold value obtained by adding a predetermined added value to the level of the noise-like portion of the correlation waveform obtained by simulation, as indicated by the broken line in FIG.

  The effective path determination unit 12 selects a peak portion exceeding the threshold supplied from the threshold generation unit 14 from the correlation waveform from the correlation unit 11 as an effective path corresponding to the main wave and the delayed wave. The effective path determination unit 12 outputs a delay profile (FIG. 5B) indicating the selected effective path.

  Thus, in the present embodiment, by setting a threshold value that adaptively changes corresponding to the noise-like portion of the correlation waveform, the peak of the correlation waveform is higher than the noise-like portion and based on the main wave and the delayed wave. It is possible to determine an effective path using a threshold level lower than that of the portion. Therefore, a peak portion corresponding to a delayed wave with a low power level can be detected without erroneously detecting a noise-like portion as a peak. Thus, a path based on the main wave and the delayed wave can be reliably detected from the correlation waveform, and an accurate delay profile based on the main wave and the delayed wave can be obtained. By using this delay profile, the transmission line response can be estimated with high accuracy, and reliable waveform equalization can be performed by a subsequent circuit.

  FIG. 6 is a block diagram showing a second embodiment of the present invention. In FIG. 6, the same components as those in FIG.

  This embodiment is different from the first embodiment in that a threshold generation unit 24 is used instead of the threshold generation unit 14. In addition to the frame synchronization signal and the output of the distance detection unit 13, the threshold generation unit 24 is supplied with the output of the correlation unit 11.

  The threshold generation unit 24 obtains the threshold thr to be set in the effective path determination unit 12 using the frame synchronization signal, the output of the distance detection unit 13 and the output of the correlation unit 11. For example, the threshold generation unit 24 uses the maximum path power value peak obtained from the output of the correlation unit 11 and the time distance range from the distance detection unit 13 to obtain the threshold thr by the calculation of the following equation (1). .

thr = gain1 · range + gain2 · peak (1)
Note that gain1 and gain2 are predetermined coefficients set by the threshold generation unit 24, the slope of the threshold can be controlled by gain1, and the offset amount in the power direction with respect to peak can be controlled by gain2.

  Other configurations are the same as those of the first embodiment.

  In the embodiment configured as described above, the method of obtaining the threshold used for determining the effective path is only different from that of the first embodiment. In the first embodiment, the threshold value is obtained by adding a predetermined value to the level of the noise-like portion obtained by the simulation. However, in the present embodiment, the output of the correlation unit 11 is further used. By controlling the coefficients gain1 and gain2, it is possible to control the slope of the threshold and the offset amount in the power direction. Thereby, according to the magnitude of the cross-correlation between the reference signal and the frame body, the magnitude of the influence of noise, the change of the reception environment, the difference of the wireless communication standard, etc., the state of change of the threshold can be adaptively changed, It is possible to obtain the delay profile with higher accuracy.

  As described above, the present embodiment has an effect that the delay profile can be obtained with higher accuracy by controlling the coefficients gain1 and gain2 to adaptively change the change state of the threshold value.

  The method for generating the threshold is not limited to the linear function shown in the above equation (1), and an arbitrary function such as a quadratic function may be adopted. Further, a table prepared in advance may be referred to, and the above-described calculation and table may be used in combination, and the present invention is not limited to these methods.

  FIG. 7 is a block diagram showing a third embodiment of the present invention. In FIG. 7, the same components as those in FIG.

  This embodiment is different from the second embodiment in that a threshold value generation unit 34 is employed instead of the threshold value generation unit 24 and a smoothing unit 35 is added. The output of the correlation unit 11 is given to the smoothing unit 35, and the output of the smoothing unit 35 is supplied to the threshold value generation unit 34 and the effective path determination unit 12.

  The smoothing unit 35 smoothes the correlation waveform output from the correlation unit 11 by integrating it in units of frames, and supplies the smoothed output to the threshold generation unit 34 and the effective path determination unit 12. The cross-correlation value by the frame body and the reference signal can be regarded as substantially white noise, and the S / N can be improved by the smoothing process. Thereby, the threshold value generation unit 34 can set the threshold value lower than that in the second embodiment.

  Therefore, in this embodiment, it is possible to detect an effective path with a lower power level, and to improve the transmission path estimation accuracy.

  The smoothed output from the smoothing unit 35 is output to the waveform equalization circuit at the subsequent stage and used for improving the accuracy of the waveform equalization processing.

  Thus, in the present embodiment, by integrating and smoothing the correlation waveform in units of frames, the S / N can be improved, and the transmission line response can be estimated with higher accuracy.

  Note that the smoothing unit 35 may perform smoothing by integrating the power of the output of the correlation unit, vector integration, and path vectors in phase. Further, the smoothing unit 35 may perform smoothing using an FIR or IIR filter. Further, the smoothing unit 35 may perform a smoothing process in the symbol direction or both directions instead of the frame direction.

  Also, this embodiment can be applied to the first embodiment. In this case, the threshold generation unit 14 can recognize the actual level of the noise-like portion of the correlation waveform based on the output of the smoothing unit 35. As a result, the threshold value can be set lower so as to be higher than the noise-like portion and lower than the peak portion due to the delayed wave, and the delay profile can be obtained with high accuracy.

  FIG. 8 is a block diagram showing a fourth embodiment of the present invention. In FIG. 8, the same components as those in FIG.

  In each of the above embodiments, an example has been described in which only a peak corresponding to the main wave in the correlation waveform, that is, only one path having sufficient power is generated. However, depending on the reception environment, multiple paths with sufficient power may occur.

  FIG. 9 is an explanatory diagram showing the correlation waveform in this case, FIG. 9A shows the correlation waveform of the main wave and the delayed wave separately, and FIG. 9B shows the correlation waveform output from the correlator 11. Show.

  As described above, the correlation value between the main wave and the reference signal increases as the symbol position from the path based on the main wave shifts. Further, when the delayed wave has sufficient power as in the case of the main wave, as shown in FIG. 9A, the correlation value increases as the symbol position from the path based on the delayed wave shifts. Although FIG. 9A shows the correlation waveform of the main wave and the delayed wave separately, the actual correlation waveform is a composite waveform of both, and as shown in FIG. 9B, between the main wave and the delay. Produces a portion where the level change is substantially flat.

  In this case, when the first embodiment is adopted and the threshold value is set based on only the peak position of the main wave, the threshold value T1 ′ having the lowest level at the peak position of the main wave as shown in FIG. 9B. Is obtained. However, the threshold T1 'has a relatively high level at the peak position of the delayed wave as compared with the correlation waveform. Therefore, when such a threshold value T1 'is used, a delayed wave having a relatively low level cannot be detected in the vicinity of the peak position of the delayed wave. Conversely, when the threshold T2 ′ is set in consideration of the level of the correlation waveform in the vicinity of the peak position of the delayed wave, this threshold T2 ′ is only a level lower than the level of the correlation waveform other than in the vicinity of the peak position of the delayed wave. The delayed wave is erroneously detected in the noise portion.

  Therefore, in the present embodiment, it is possible to set a threshold corresponding to the level change of the correlation waveform obtained from the correlation unit 11.

  In FIG. 8, the correlation waveform from the correlation unit 11 is given to the peak detection unit 41. The peak detector 41 detects a path with a predetermined power or higher by comparing the correlation waveform with a predetermined threshold. Thereby, the main wave and the delayed wave having a sufficiently high power level shown in FIG. 9A are detected. The detection result from the peak detector 41 is given to the distance detector 13 and the threshold generator 14. The detection result of the peak detection unit 41 indicates the peak position of a path having power greater than or equal to a predetermined power. Note that the peak detector 41 detects one or more peak positions in one frame.

  The distance detection unit 13 calculates, for example, the current time distance (for example, in symbol units) of the output of the correlation unit 11 using each peak position detected by the peak detection unit 41 as a reference, and calculates the calculation result as a threshold generation unit 14. To output. Based on the peak position and the output of the distance detector 13, the threshold generator 14 is higher than the noise-like portion and lower than the peak portion due to the delayed wave for each peak detected by the peak detector 41. In addition, a threshold value that changes with time is adaptively generated.

  For example, the threshold value generation unit 14 generates a threshold value corresponding to the time distance from each peak position by adding a predetermined value to the level of the noise-like portion obtained by the simulation. The threshold value corresponding to each peak from the threshold value generation unit 14 is supplied to the synthesis threshold value generation unit 42. The synthesis threshold generation unit synthesizes the input thresholds and outputs the synthesis threshold to the valid path determination unit 12. For example, the synthesis threshold value generation unit 42 may obtain the synthesis threshold value by adding and averaging the input threshold values.

  Other configurations are the same as those of the first embodiment.

  Next, the operation of the embodiment configured as described above will be described with reference to the explanatory diagram of FIG. FIG. 10A shows two threshold values corresponding to two peaks, respectively, and FIG. 10B shows a correlation waveform and a combined threshold value.

  Also in the present embodiment, the correlation unit 11 calculates the sliding complex time correlation while shifting the reference signal by one symbol from the received signal, and outputs the correlation waveform to the effective path determination unit 12. This correlation waveform is also given to the peak detector 41. The peak detector 41 detects a correlation waveform whose level exceeds a predetermined threshold as a path with sufficiently high power. The detection result of the peak detector 41 is given to the distance detector 13 and the threshold generator 14.

  The distance detection unit 13 calculates the time distance of the current output of the correlation unit 11 based on each peak position for each peak position of each path with high power, and generates a calculation result as a threshold value. To the unit 14. The threshold value generation unit 14 obtains the level of the noise-like portion excluding the peak portion of the correlation waveform by simulation, and corresponds to each peak according to the current time based on the peak position and the output of the distance detection unit 13. The generated threshold value is adaptively generated.

  FIG. 10A shows the threshold values T1 and T2 obtained by the threshold generation unit 14 for the correlation waveform shown in FIG. The threshold value T1 corresponds to the main wave S1, and the threshold value T2 corresponds to the delayed wave S2. The delayed wave S3 has a relatively low power level and is not detected as a peak in the peak detector 41.

  The threshold value for each peak detected by the peak detection unit 41 is supplied to the synthesis threshold value generation unit 42, and the synthesis threshold value generation unit 42 synthesizes the threshold values for each peak to obtain a synthesis threshold value. The broken line in FIG. 10B indicates the combined threshold value T3 obtained from the threshold values T1 and T2. The synthesis threshold value from the synthesis threshold value generation unit 42 is supplied to the effective path determination unit 12.

  The effective path determination unit 12 compares the correlation waveform from the correlation unit 11 with the synthesis threshold value. In the example of FIG. 10B, an effective path is obtained by comparing the correlation waveform indicated by the solid line with the combined threshold value T3 indicated by the broken line. Thus, a delay profile including the main wave S1 and the delay waves S2 and S3 is obtained.

  As described above, in the present embodiment, the same effect as in the first embodiment can be obtained, and even when a plurality of delayed waves having sufficiently high power levels are included in the received signal, the received signal is higher than the noise-like portion. In addition, a synthesis threshold level lower than the peak portion of the correlation waveform based on the main wave and the delay wave can be set, and an accurate delay profile based on the main wave and the delay wave can be obtained. By using this delay profile, the transmission line response can be estimated with high accuracy, and reliable waveform equalization can be performed by a subsequent circuit.

  In the present embodiment, the threshold value generator 14 obtains the threshold value for each peak by adding a predetermined value to the level of the noise-like portion obtained by simulation, but the second embodiment. And the threshold value for each peak may be obtained from the above equation (1).

  FIG. 11 is a block diagram showing a fifth embodiment of the present invention. 11, the same components as those in FIGS. 7 and 8 are denoted by the same reference numerals, and the description thereof is omitted.

  This embodiment is different from the fourth embodiment in that a threshold value generator 34 is employed instead of the threshold value generator 14 and a smoothing unit 35 is added. The output of the correlation unit 11 is given to the smoothing unit 35, and the output of the smoothing unit 35 is supplied to the threshold value generation unit 34 and the effective path determination unit 12.

  This embodiment is a combination of the third embodiment in FIG. 7 and the fourth embodiment in FIG. 8, and the correlation output from the correlation unit 11 by using the smoothing unit 35. The waveform is smoothed by integrating in units of frames to improve S / N. The threshold value generation unit 34 can set the threshold value lower than that in the fourth embodiment, and the synthesis threshold value is also lower than that in the fourth embodiment.

  Thus, in the present embodiment, by integrating and smoothing the correlation waveform in units of frames, the S / N can be improved, and the transmission line response can be estimated with higher accuracy.

  In the above embodiment, the correlation waveform from the correlation unit 11 is given to the peak detection unit 41, but the correlation waveform after smoothing from the smoothing unit 35 is also given to the peak detection unit 4. Also good.

    DESCRIPTION OF SYMBOLS 11 ... Correlation part, 12 ... Effective path determination part, 13 ... Distance detection part, 14, 24, 34 ... Threshold generation part, 35 ... Smoothing part.

Claims (6)

A correlation unit that receives a reception signal having a frame configuration including a known pattern, calculates a time correlation between a reference signal having the same pattern as the known pattern and the reception signal, and outputs a correlation value;
A time distance detection unit for obtaining a time distance of an output of the correlation unit based on a maximum peak position of the correlation value during a frame period of the received signal and outputting time distance information;
A threshold generation unit that generates a threshold corresponding to a change in the correlation value calculated by the correlation unit based on the maximum peak position and the time distance information;
An effective path determination unit that obtains an effective detection result of a delayed wave based on the level of the correlation value by comparing the correlation value from the correlation unit with the threshold value, and outputs the detection result as a delay profile; A transmission path response estimator characterized by the above. A correlation unit that receives a reception signal having a frame configuration including a known pattern, calculates a time correlation between a reference signal having the same pattern as the known pattern and the reception signal, and outputs a correlation value;
A time distance detection unit that outputs a time distance information by obtaining a time distance of the output of the correlation unit for each peak position based on a peak position of one or more of the correlation values equal to or greater than a predetermined threshold;
A threshold value generation unit that generates a threshold value corresponding to a change in the correlation value calculated by the correlation unit based on the time distance information for each peak position;
A combining unit that combines the thresholds for each of the peak positions generated by the threshold generation unit to obtain a combined threshold;
An effective path determination unit that obtains an effective detection result of a delayed wave based on the level of the correlation value by comparing the correlation value from the correlation unit with the synthesis threshold, and outputs the detection result as a delay profile; A transmission path response estimator characterized by comprising:   The transmission path response estimator according to claim 1, wherein the threshold generation unit generates the threshold based on the maximum peak position, the time distance information, and the correlation value.   The transmission path response estimator according to claim 3, wherein the threshold value generation unit controls an offset amount of the threshold value based on a maximum value of the correlation value. Comprising a smoothing unit for smoothing and outputting the correlation value from the correlation unit;
The transmission path response estimator according to claim 1 or 2, wherein the threshold generation unit generates the threshold based on the maximum peak position, the time distance information, and an output of the smoothing unit.   The smoothing unit performs smoothing by performing vector integration of the received signal in units of frames, performing phase integration and performing vector integration, using an IIR filter, or using an FIR filter. 5. A transmission path response estimator according to 5.

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