JP2010278827A - Ofdm symbol identification device and ofdm receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an OFDM symbol identification device or the like for identifying an OFDM symbol with high accuracy at low cost. <P>SOLUTION: A delaying part 50 delays an input OFDM signal S13 to generate a delay signal. A correlation calculating part 70 calculates a correlation between the OFDM signal S13 and the delay signal. A peak position detecting part 90 detects peak positions of the correlation for each observation period of predetermined time length. A peak position evaluating part 110 obtains a plurality of detected peak positions, and evaluates the identity of the peak positions on the basis of a difference (peak position difference) among the plurality of peak positions. An identifying part 130 obtains a plurality of kinds of peak position evaluation results by the peak position evaluating part, and identifies the effective symbol length and guard interval length of the OFDM signal on the basis of a peak position evaluation result that has the best identity of the peak position among the plurality of kinds of peak position evaluation results. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an OFDM symbol identification device capable of identifying an effective symbol length and a guard interval length of an Orthogonal Frequency Division Multiplexing (OFDM) which is an example of a digital transmission method, and also relates to the OFDM symbol identification device. Is related to an OFDM receiver.

  As a first conventional example of an OFDM signal receiving apparatus, there is one described in Patent Document 1. In this receiving apparatus, a correlation signal is obtained based on the product of the received signal and a delayed signal obtained by delaying the received signal by a certain time. The delay time of the delay signal is set to each of the effective symbol lengths that may be transmitted. For this reason, as many correlation signals as the number of effective symbol lengths that may be transmitted are obtained.

  Then, a correlation integration signal is obtained by integrating these correlation signals over a certain period of time. The integration time at this time is set to each of the guard interval lengths that may be transmitted. Therefore, as many correlation integral signals as the number of guard interval lengths that may be transmitted are obtained. For each obtained correlation integrated signal, a peak (peak signal) is detected and held.

  Thereafter, the magnitudes of the obtained peak signals are compared in the comparison / determination unit, and the effective symbol length and guard interval length of the received signal are determined based on the peak value detection pattern.

  A second conventional example of an OFDM signal receiving apparatus is described in Patent Document 2. This receiving apparatus has a guard interval length detection apparatus. The guard interval length detection device includes a correlation maximum value position information output unit and a guard interval determination unit.

  The correlation maximum value position information output means calculates the correlation between the OFDM signal and a delayed signal obtained by delaying the OFDM signal by a certain time, and outputs the position having the strongest correlation in a specific section as the correlation maximum value position information. . The guard interval determination means detects the guard interval length based on the correlation maximum value position information.

JP-A-10-327122 JP 2006-042297 A

  As described above, the first conventional receiving apparatus detects the guard interval length using the magnitude of the peak signal. For this reason, when the level fluctuation of the received signal is large, there is a problem that the detection accuracy deteriorates.

  One solution to this problem is a second conventional example that does not use the magnitude of the peak signal.

  However, the device cost may be a problem in the second conventional example. More specifically, in order to analyze the variation of the maximum correlation position, the variance value of the position information is calculated. In order to calculate the variance value, it is necessary to calculate the average value of the square of the position information and the square value of the average value of the position information. When these operations are realized by hardware, the circuit scale of a square operation circuit is particularly large, which increases the device cost.

  An object of the present invention is to provide an OFDM symbol identification device and an OFDM reception device capable of accurately identifying an OFDM symbol at low cost.

  An OFDM signal identification device according to the present invention includes a delay unit that delays an input OFDM signal to generate a delayed signal, a correlation calculation unit that calculates a correlation between the OFDM signal and the delayed signal, and a peak of the correlation A peak position detection unit that detects a position for each observation period of a predetermined time length, and acquires a plurality of detected peak positions, and based on a peak position difference that is a difference between the plurality of peak positions, A peak position evaluation unit that evaluates identity, and a plurality of types of peak position evaluation results obtained by the peak position evaluation unit are acquired, and among the plurality of types of peak position evaluation results, the peak position evaluation with the best peak position identity is obtained. And an identification unit for identifying an effective symbol length and a guard interval length of the OFDM signal based on the result.

  According to the above configuration, the effective symbol length and guard interval length of the input OFDM signal are identified using the peak position difference. For this reason, better discrimination accuracy can be obtained as compared with a configuration in which the OFDM symbol is identified using the magnitude of the peak signal. Further, the cost can be reduced as compared with the configuration in which the OFDM symbol is identified using the dispersion value of the peak position.

1 is a block diagram illustrating an OFDM receiving apparatus according to Embodiment 1. FIG. 3 is a block diagram illustrating an OFDM symbol identification unit according to Embodiment 1. FIG. 3 is a block diagram illustrating an example of a delay unit according to Embodiment 1. FIG. 6 is a block diagram showing another example of the delay unit according to Embodiment 1. FIG. 3 is a block diagram illustrating a correlation calculation unit according to Embodiment 1. FIG. 3 is a block diagram illustrating a peak position detection unit according to Embodiment 1. FIG. 4 is a block diagram illustrating a peak position evaluation unit according to Embodiment 1. FIG. 3 is a block diagram illustrating a peak position difference calculation processing unit according to Embodiment 1. FIG. 3 is a block diagram illustrating an absolute value addition processing unit according to Embodiment 1. FIG. 4 is a block diagram illustrating an identification unit according to Embodiment 1. FIG. 6 is a block diagram illustrating an identification unit according to Modification 1 of Embodiment 1. FIG. FIG. 10 is a block diagram illustrating an absolute value addition processing unit according to a second modification of the first embodiment. FIG. 10 is a schematic diagram outlining a process in an absolute value addition processing unit according to Modification 2 of Embodiment 1. FIG. 10 is a block diagram illustrating a peak position difference calculation processing unit according to Modification 3 of Embodiment 1. 10 is a block diagram illustrating an example of an absolute value addition processing unit according to Modification 3 of Embodiment 1. FIG. FIG. 10 is a block diagram illustrating another example of an absolute value addition processing unit according to Modification 3 of Embodiment 1. 6 is a block diagram illustrating an OFDM symbol identification unit according to Embodiment 2. FIG. 6 is a block diagram illustrating a delay unit according to Embodiment 2. FIG. 6 is a block diagram illustrating an identification unit according to Embodiment 2. FIG.

Embodiment 1 FIG.
FIG. 1 is a block diagram illustrating an OFDM receiver 10 according to the first embodiment. The receiving device 10 is a device capable of receiving an OFDM signal by a wired or wireless system, and can constitute, for example, a digital broadcast receiving device, a wireless LAN receiving device, or the like.

  The exemplary receiving apparatus 10 includes an analog processing unit 11, an A / D conversion unit 12, an orthogonal demodulation unit 13, an effective symbol extraction unit 14, an FFT unit 15, a P / S conversion unit 16, and an OFDM symbol identification. Part 17. In the drawings, various elements are appropriately abbreviated.

  The analog processing unit 11 acquires an analog OFDM signal, performs predetermined analog processing on the signal, and outputs the signal. Examples of the predetermined analog processing include gain adjustment by an amplifier, frequency conversion by a mixer, band limitation by a bandpass filter, and the like.

  The A / D conversion unit 12 acquires an output signal from the analog processing unit 11, performs analog / digital conversion on the signal, and outputs the signal.

  The orthogonal demodulator 13 acquires an output signal from the A / D converter 12, converts the signal into a complex baseband signal S13, and outputs the complex baseband signal S13.

  The effective symbol extraction unit 14 acquires the output signal S13 from the orthogonal demodulation unit 13, and removes the guard interval for each OFDM symbol from the signal. Thereby, the effective symbol of the OFDM symbol is extracted from the acquired signal S13. A signal composed of the extracted effective symbols is output from the effective symbol extraction unit 14.

  The FFT unit 15 acquires the output signal from the effective symbol extraction unit 14 and performs fast discrete Fourier transform on the signal. Thereby, parallel data corresponding to each subcarrier is obtained and output from the FFT unit 15.

  The P / S conversion unit 16 acquires the output signal from the FFT unit 15, that is, parallel data, and converts it into serial data. Thereby, complex symbol data is obtained and output from the P / S converter 16. Note that the signal output from the P / S conversion unit 16, that is, complex symbol data, is provided for reproduction processing or the like by a configuration (not shown), for example.

  The OFDM symbol identification unit 17 acquires the output signal (complex baseband signal) S13 from the orthogonal demodulation unit 13, and identifies, in other words, identifies the OFDM symbol of the signal S13. More specifically, the effective symbol length and the guard interval length are identified. The identification result S17, that is, the identified effective symbol length and guard interval length are output to the effective symbol extraction unit 14, the FFT unit 15, and the P / S conversion unit 16.

  In the effective symbol extraction unit 14, the symbol identification result S17 is used, for example, to determine an effective symbol part to be extracted, in other words, to determine a guard interval part to be removed. The FFT unit 15 uses the symbol identification result S17 in order to set the FFT size, for example. Further, in the P / S conversion unit 16, for example, a desired setting of the P / S conversion process is performed based on the symbol identification result S17.

  As described above, by providing the symbol identification unit 17, each of the units 14, 15, and 16 can execute an appropriate operation according to the characteristics of the OFDM signal. That is, the receiving apparatus 10 can cope with a plurality of types of OFDM signals.

  A specific example of the OFDM symbol identification unit 17 will be described below. FIG. 2 is a block diagram illustrating the symbol identification unit 17.

  The exemplary symbol identification unit 17 includes a delay unit 50, a correlation calculation unit 70, a peak position detection unit 90, a peak position evaluation unit 110, and an identification unit 130.

  The delay unit 50 acquires the complex baseband signal S13 output from the orthogonal demodulation unit 13 as an identification target signal, and generates and outputs a delay signal obtained by delaying the signal S13 by a predetermined delay time. The delay time is set to the same time length as the effective symbol length that may be employed in the identification target signal S13.

  Here, a case where there are three possible values (candidate values) as effective symbol lengths A, B, and C (assuming A <B <C) is illustrated. Note that the reference symbol A is used for the effective symbol length having the time length A, and so on. In this example, three types of delay signals S50A, S50B, and S50C (see FIG. 3) are generated with three types of time lengths A, B, and C.

  More specifically, the delay unit 50 delays the identification target signal S13 by an effective symbol length A, a delay signal S50B by delaying the signal S13 by an effective symbol length B, and the signal S13 by an effective symbol. A delayed signal S50C delayed by a length C is generated.

  FIG. 3 shows a configuration example of the delay unit 50. In the example of FIG. 3, the delay unit 50 includes four delay processing units 51 to 54 connected in series, and the signal S13 input to the first-stage delay processing unit 51 is received by the delay processing units 51 to 54. Sequentially delayed cumulatively. In the example of FIG. 3, the output signals of the first-stage, second-stage, and fourth-stage delay processing sections 51, 52, and 54 correspond to the delayed signals S50A, S50B, and S50C, respectively.

  In this case, the delay time of the delay processing unit 51 is set to the effective symbol length A, the total delay time of the delay processing units 51 and 52 is set to the effective symbol length B, and the total delay time of the delay processing units 51 to 54 is set. Is set to an effective symbol length C.

  FIG. 4 shows another configuration example of the delay unit 50. In the example of FIG. 4, the delay unit 50 includes three delay processing units 55A, 55B, and 55C provided in parallel, and the identification target signal S13 is input to each of the delay units 55A, 55B, and 55C. The delay times of the delay processing units 55A, 55B, and 55C are set to the effective symbol lengths A, B, and C, respectively, whereby the delay signals S50A, S50B, and S50C are output from the delay processing units 55A, 55B, and 55C, respectively. .

  3 and FIG. 4, the delay signals 50A, 50B, and 50C are output from the delay unit 50 in parallel, in other words, simultaneously.

  The correlation calculation unit 70 (see FIG. 2) acquires the identification target signal S13 and the delayed signals S50A, S50B, and S50C, calculates the correlation between the identification target signal S13 and each of the delayed signals S50A, S50B, and S50C, and calculates the calculation result. Output.

  FIG. 5 shows a configuration example of the correlation calculation unit 70. The correlation calculation unit 70 illustrated in FIG. 5 includes a complex conjugate multiplication unit 71 and a moving average calculation unit 75.

  The complex conjugate multiplier 71 obtains a complex baseband signal S13 that is an identification target signal and delay signals S50A, S50B, and S50C, and performs complex conjugate multiplication of the identification target signal S13 and each of the delay signals S50A, S50B, and S50C. Go and output.

  In the example of FIG. 5, the complex conjugate multiplication unit 71 includes a complex conjugate multiplication processing unit 72A that performs complex conjugate multiplication of the complex baseband signal S13 and the delayed signal S50A, and complex conjugate multiplication that performs complex conjugate multiplication of the signals S13 and S50B. A processing unit 72B and a complex conjugate multiplication processing unit 72C that performs complex conjugate multiplication of the signals S13 and S50C are provided. The complex conjugate multiplication processing units 72A, 72B, and 72C output multiplication results S71A, S71B, and S71C, respectively. In the case of the configuration of FIG. 5, complex conjugate multiplication is performed in parallel, and the operation results S71A, S71B, and S71C are output from the complex conjugate multiplier 71 in parallel.

  The complex conjugate multiplication may be performed by multiplying the complex baseband signal S13 by the conjugate complex number of each delay signal S50A, S50B, S50C, or conversely, the conjugate complex number of the complex baseband signal S13 and each delay signal. S50A, S50B, and S50C may be multiplied.

  The moving average calculation unit 75 acquires the complex conjugate multiplication result signals S71A, S71B, S71C, calculates the moving average of each signal S71A, S71B, S71C, and outputs the calculation result. The moving average calculation target period, in other words, the calculation window is set to the same time length as the guard interval length that may be employed in the identification target signal S13.

  Here, in general, the guard interval consists of a copy of the rear part of the effective symbol and is added to the head of the effective symbol. Note that the ratio of the length of the copy portion to the effective symbol length, that is, the ratio of the guard interval length to the effective symbol length may be referred to as a guard interval ratio. The guard interval ratio is defined in advance, and here, four types of k, l, m, and n (0 <k, l, m, and n <1) are exemplified.

  In such an example, four types of values of A × k, A × 1, A × m, and A × n are candidates for the guard interval length for the effective symbol length A. Similarly, for the effective symbol length B, B × k, B × 1, B × m, and B × n are guard interval length candidate values, and for the effective symbol length C, C × k and C × l. , C × m, and C × n are guard interval length candidate values. Note that the reference symbol Ak is used for the guard interval length having the time length A × k, and the others are similarly expressed.

  Therefore, the moving average calculation unit 75 calculates the moving average of the complex conjugate multiplication result signal S71A related to the effective symbol length A, and calculates the time lengths of A × k, A × 1, A × m, and A × n, respectively. And the calculation results 75Ak, S75Al, S75Am, and S75An are output. The calculation results S75Ak, S75Al, S75Am, and S75An correspond to the calculation target periods Ak, Al, Am, and An, respectively.

  5, only the moving average calculation processing unit 76Ak that performs the moving average of the signal S71A over the period Ak and outputs the calculation result signal S75Ak is illustrated in order to avoid complication of the drawing.

  Similarly, the moving average calculation unit 75 calculates the moving average by applying the calculation target periods Bk, B1, Bm, Bn to the complex conjugate multiplication result signal S71B related to the effective symbol length B, and calculates the calculation results S75Bk, S75Bl. , S75Bm, S75Bn are output. Further, the moving average calculating unit 75 calculates the moving average by applying the calculation target periods Ck, Cl, Cm, and Cn to the complex conjugate multiplication result signal S71C related to the effective symbol length C, and calculates the results S75Ck, S75Cl, and S75Cm. , S75Cn is output.

  In this way, the moving average calculation results are the same as the integrated value of the number of effective symbol length candidate values and the number of guard interval ratio candidate values (in other words, the effective symbol length candidate value and the guard interval length candidate value). Are generated for 12 systems (hereinafter also referred to as candidate systems).

  In the example of FIG. 5, the moving average calculation result signals S75Ak, S75Al, S75Am, S75An, S75Bk, S75Bl, S75Bm, S75Bn, S75Ck, S75Cl, S75Cm, and S75Cn are correlation calculation result signals that are output signals from the correlation calculation unit 70. It corresponds to. In the case of the configuration of FIG. 5, the moving average calculation results S75Ak, S75Al, S75Am, S75An, S75Bk, S75Bl, S75Bm, S75Bn, S75Ck, S75Cl, S75Cm, and S75Cn are generated in parallel. Output from the correlation calculation unit 70 in parallel.

  The peak position detector 90 (see FIG. 2) acquires correlation calculation result signals S75Ak, S75Al, S75Am, S75An, S75Bk, S75B1, S75Bm, S75Bn, S75Ck, S75Cl, S75Cm, and S75Cn. Then, the peak position detection unit 90 is provided for each correlation calculation result signal, in other words, for each candidate system, the peak position in the signal (position where the signal level is locally increased. Here, the position where the signal level is maximum). And detection results S90Ak, S90Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, and S90Cn (see FIG. 6) are output.

  In addition, regarding the correlation calculation result signal and the peak position detection result signal, signals having the same last two characters of the reference numerals correspond to each other. For example, the peak position detection result signal S90Ak is obtained based on the correlation calculation result signal S75Ak. Such notation of the reference signs is also used for various signals described later.

  FIG. 6 shows a configuration example of the peak position detection unit 90. In the example of FIG. 6, only the peak position detection processing unit 91Ak that detects the peak position of the correlation calculation result signal S75Ak and outputs the detection result signal S90Ak is illustrated in order to avoid complication of the drawing.

  The detection of the peak position is repeated with the observation period set to a predetermined time length as one unit. Here, the peak expression time when the start time of the observation period is used as a reference (origin), in other words, the time length from the start time of the observation period to the peak expression time is used as the peak position value.

  The length of the observation period is the sum of the effective symbol length candidate value and the guard interval length candidate value involved in the generation of the correlation calculation result signal to be observed (hereinafter also referred to as the symbol length candidate value). Set to For example, since the correlation calculation result signal S75Ak is generated based on the effective symbol length A and the guard interval length Ak, the length of the peak position observation period for the signal S75Ak is set to A + Ak. Here, the length of the peak position observation period has the same number (12 in this case) as the candidate system.

  In the case of the configuration of FIG. 6, the detection of peak positions for the input signals S75Ak, S75Al, S75Am, S75An, S75Bk, S75B1, S75Bm, S75Bn, S75Ck, S75Cl, S75Cm, and S75Cn is performed in parallel. The peak position detection results S90Ak, S90Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, and S90Cn are output from the peak position detector 90 in parallel.

  The peak position evaluation unit 110 (see FIG. 2) acquires peak position detection result signals S90Ak, S90Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, and S90Cn. And the peak position evaluation part 110 evaluates the identity of a peak position, and outputs an evaluation result.

  FIG. 7 shows a configuration example of the peak position evaluation unit 110. The peak position evaluation unit 110 illustrated in FIG. 7 includes a peak position difference calculation unit 111 and an absolute value addition unit 116.

  The peak position difference calculation unit 111 calculates differences for a plurality of peak positions and outputs the obtained difference values. FIG. 7 illustrates only the peak position difference calculation processing unit 112Ak that calculates the peak position difference for the peak position detection result S90Ak and outputs the calculation result (in other words, the difference value) S111Ak in order to avoid complication of the drawing. Yes.

  FIG. 8 shows a configuration example of the peak position difference calculation processing unit 112Ak. In the example of FIG. 8, the peak position detection result S90Ak is directly input to the subtraction unit 113 and is input to the subtraction unit 113 via the latch unit 114.

  The latch unit 114 receives the peak position detection result S90Ak and holds the peak position detection result S90Ak until the next input (peak position detection result S90Ak). Then, the latch unit 114 outputs the held peak position detection result S90Ak with the end of the holding.

  The subtraction unit 113 receives the peak position detection result S90Ak input to the latch unit 114 and the peak position detection result S90Ak output from the latch unit 114 (that is, the previous peak position detection result S90Ak). . Then, the subtractor 113 calculates and outputs the difference between the two inputs, that is, the peak position difference. In this case, the subtraction unit 113 calculates the peak position difference for the continuous peak position detection result S90Ak.

  Similarly, the peak position difference calculation unit 111 performs peak position detection results S90Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, and S90Cn, in other words, for each candidate system. The difference is calculated, and the calculation results (that is, the difference values) S111Al, S111Am, S111An, S111Bk, S111B1, S111Bm, S111Bn, S111Ck, S111Cl, S111Cm, and S111Cn are output.

  The absolute value addition unit 116 acquires the peak position difference calculation results S111Ak, S111Al, S111Am, S111An, S111Bk, S111Bl, S111Bm, S111Bn, S111Ck, S111Cl, S111Cm, and S111Cn, and in other words, for each peak position difference calculation result. For example, a value obtained by taking the absolute value of the difference value is cumulatively added for each candidate system. Then, the absolute value addition unit 116 outputs the obtained cumulative addition result (that is, cumulative addition value).

  In FIG. 7, only the absolute value addition processing unit 117Ak that performs the above-described absolute value addition on the peak position difference calculation result signal S111Ak and outputs the calculation result (that is, the absolute value addition value) S115Ak is illustrated in order to avoid complication of the drawing. Show.

  FIG. 9 shows a configuration example of the absolute value addition processing unit 117Ak. In the example of FIG. 9, the peak position detection result S90Ak is input to the adder 119 via the absolute value calculator 118 that takes the absolute value of the input signal. The output of the adder 119 is input to the adder 119 via the latch unit 120.

  The latch unit 120 receives the addition result from the addition unit 119 and holds the addition result until the next input is made to the addition unit 119. Then, the latch unit 120 outputs the held addition result to the adding unit 119 when the holding ends. Thereby, the addition unit 119 adds the absolute value of the new peak position difference output from the absolute value calculation unit 118 and the cumulative addition result up to the previous time output from the latch unit 120. That is, the absolute value of the peak position difference obtained sequentially is cumulatively added.

  Similarly, the absolute value addition unit 116 performs the peak position difference calculation results S111Al, S111Am, S111An, S111Bk, S111Bl, S111Bm, S111Bn, S111Ck, S111Cl, S111Cm, and S111Cn, in other words, for each candidate system. Are cumulatively added, and calculation results S115Al, S115Am, S115An, S115Bk, S115B1, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, and S115Cn are output.

  In the example of FIG. 7, the absolute value addition result signals S115Ak, S115Al, S115Am, S115An, S115Bk, S115Bl, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, and S115Cn are peak positions that are output signals from the peak position evaluation unit 110. It corresponds to the evaluation result signal.

  In the case of the configuration of FIG. 7, the peak position difference calculation is performed in parallel for the input signals S90Ak, S90Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, and S90Cn. The same applies to absolute value addition. The evaluation result signals S115Ak, S115Al, S115Am, S115An, S115Bk, S115Bl, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, and S115Cn are supplied in parallel from the absolute value addition unit 116, in other words, from the peak position evaluation unit 110. Is output.

  Here, according to the configuration of FIG. 7, the smaller the absolute value of the peak position difference is, the higher the frequency at which peaks appear at the same position in each observation period, that is, it can be evaluated that the identity of the peak positions is high. It is. This tendency is the same even if the absolute value of the peak position difference is cumulatively added. Further, by accumulating the absolute values of the peak position differences, it is possible to perform evaluation with higher accuracy, that is, with higher reliability than using only the absolute values of the peak position differences each time.

  For example, the latch unit 120 of the absolute value addition unit 116 may be reset and the cumulative addition value may be returned to zero after a predetermined time set in advance.

  The identification unit 130 (see FIG. 2) acquires a plurality of types of peak position evaluation results S115Ak, S115Al, S115Am, S115An, S115Bk, S115Bl, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, and S115Cn for each candidate system. Then, based on these evaluation results, the effective symbol length and guard interval length of the complex baseband signal S13 input to the symbol identifying unit 17 are identified, in other words, identified. Then, the identification unit 130 outputs a signal S17 of the identification result.

  FIG. 10 shows a configuration example of the identification unit 130. The identification unit 130 illustrated in FIG. 10 includes a minimum value determination unit 131.

  The minimum value determination unit 131 acquires peak position evaluation results S115Ak, S115Al, S115Am, S115An, S115Bk, S115Bl, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, and S115Cn, and selects the best evaluation result among these evaluation results. Judgment and selection. Here, whether the peak position evaluation result is good or best can be determined by the fact that the cumulative addition value of the absolute value of the peak position difference is relatively small or even minimum.

  Then, the minimum value determination unit 131 uses the effective symbol length and guard interval length candidate values involved in the generation of the selected evaluation result as the effective symbol length and guard of the complex baseband signal S13 input to the symbol identification unit 17. Certified as interval length.

  The minimum value determining unit 131 outputs information S131 of the recognized effective symbol length and guard interval length.

  In the example of FIG. 10, the recognition result signal S131 corresponds to the identification result signal S17 that is an output signal from the identification unit 130. In the example of FIG. 2, the identification result signal S <b> 17 corresponds to an output signal from the symbol identification unit 17.

  Here, the candidate values of the effective symbol length and the guard interval length are given in advance in the symbol identification unit 17 or the receiving apparatus 10 in such a manner that the delay unit 50 in the symbol identification unit 17 and the like can be used. . Instead of or in addition to the guard interval length candidate value, a guard interval ratio candidate value may be given in advance.

  For example, by previously storing the candidate value in a storage unit (not shown) (hereinafter referred to as a candidate value storage unit), the delay unit 50 or the like can acquire a predetermined candidate value from the candidate value storage unit. .

  Alternatively, for example, the candidate value may be supplied to the delay unit 50 or the like by a hardware circuit that generates a signal representing the candidate value.

  Alternatively, for example, when the delay unit 50 or the like performs part or all of its own processing using software, the candidate value may be described in advance in a program to be executed.

  In any of the above aspects, it is preferable that a manufacturer, an operator, a user, and the like can edit the candidate value via an input unit (not shown) such as an operation panel or a keyboard. For example, the application range of the symbol identification unit 17 can be flexibly changed. Note that editing includes at least one of change, addition, and deletion.

  Note that the effective symbol extraction unit 14 provided outside the symbol identification unit 17 can also use the candidate value by adopting the various aspects described above.

  Here, the processing of the symbol identification unit 17 according to the above configuration example will be outlined.

  As described above, the guard interval is formed by adding a rear copy of the effective symbol to the head of the effective symbol. Therefore, when the correlation between the OFDM symbol having such a configuration and the delayed symbol delayed by the actual effective symbol length of the symbol is calculated by the correlation calculating unit 70, the rear part of the OFDM symbol and the guard interval part of the delayed symbol Are strongly correlated.

  Moreover, such a strong correlation, in other words, a correlation peak, is observed with a period having the same time length as the symbol length of the OFDM symbol to be identified. For this reason, the peak position is detected at the same position in each observation period by detecting the peak position in the peak position detection unit 90 using the peak position observation period having the same length as the actual symbol length of the OFDM symbol. Is done.

  On the other hand, when a candidate value different from the actual effective symbol length and guard interval length of the OFDM symbol to be identified is used, the above-described peak position is low or not identical.

  Therefore, by evaluating the identity of the peak position, the effective symbol length and guard interval length of the OFDM symbol can be identified.

  According to the OFDM receiver 10, the following effects can be obtained.

  As described above, the symbol identification unit 17 identifies the effective symbol length and guard interval length of the input OFDM signal using the peak position difference. That is, unlike the first conventional example, the peak magnitude of the correlation signal is not used to identify the OFDM symbol. For this reason, even when the signal level of the OFDM signal to be identified varies greatly, the accuracy of symbol identification does not decrease. Therefore, good identification accuracy can be obtained.

  Further, unlike the second conventional example, the symbol identification unit 17 can identify an OFDM symbol without using the peak position variance value. For this reason, the circuit scale can be reduced as compared with the second conventional example, and the cost can be reduced and the apparatus can be downsized.

  Further, the symbol identification unit 17 according to the above example uses the absolute value of the peak position difference by cumulative addition for the evaluation of the identity of the peak position. Therefore, a simple circuit configuration as in the configuration examples of FIGS. 8 and 9 can be employed. Therefore, cost reduction and downsizing of the device can be achieved by suppressing the circuit scale.

  Further, according to the symbol identification unit 17, all combinations of effective symbol length and guard interval length candidate values are processed in parallel. Therefore, it is possible to perform high-speed processing as compared with a configuration in which candidate value combinations are processed sequentially, in other words, serially.

Modification 1 of Embodiment 1
FIG. 11 shows a configuration example according to the first modification of the identification unit 130. The identification unit 130 illustrated in FIG. 11 has a configuration in which a comparison unit 133 is added to the configuration illustrated in FIG. The comparison unit 133 acquires the best evaluation result S132 selected by the minimum value determination unit 131 (here, the minimum value of the cumulative addition value of the absolute value of the peak position difference is illustrated). Then, the comparison unit 133 compares the minimum value S132 with a predetermined threshold value TH and outputs a comparison result S133.

  For example, when the comparison unit 133 determines that the minimum value S132 is greater than the threshold value TH, the signal S133 outputs information indicating that the recognized effective symbol length and guard interval length have insufficient identification accuracy.

  On the other hand, for example, when the comparison unit 133 determines that the minimum value S132 is equal to or less than the threshold value TH, the information indicating that the effective symbol length and the guard interval length are recognized with sufficient identification accuracy is signaled. Output in S133.

  The comparison result 133 is used by, for example, the effective symbol extraction unit 14, the FFT unit 15, the P / S conversion unit 16, and the like.

  As described above, when the selected best peak position evaluation result does not satisfy the predetermined standard, the effective symbol extraction unit 14 determines that the identified effective symbol length and the guard interval length are insufficiently identified. Etc. can know the accuracy of the effective symbol length and guard interval length values used in its own processing, in other words, the reliability.

  Therefore, for example, when the accuracy of the recognized effective symbol length and guard interval length is low, the effective symbol extraction unit 14 determines that the desired OFDM signal is not received and does not execute its own processing. (For example, a standby mode). According to this, for example, power consumption can be reduced.

  Note that the comparison unit 133 may use, for example, the recognized effective symbol length and guard interval length as the best evaluation result S132. That is, the comparison unit 133 may be configured to compare the recognized effective symbol length and guard interval length with a predetermined threshold TH prepared for them.

Modification 2 of Embodiment 1
FIG. 12 shows a configuration example according to Modification 2 of the absolute value addition processing unit 117Ak (see FIG. 7).

  The absolute value addition processing unit 117Ak illustrated in FIG. 12 has a configuration in which a subtraction unit 121, a comparison unit 122, and a selection unit 123 are added to the configuration illustrated in FIG. More specifically, the peak position difference calculation result S111Ak is input to the subtraction unit 121, the comparison unit 122, and the selection unit 123 after passing through the absolute value calculation unit 118.

  The subtraction unit 121 uses the absolute value of the peak position difference S111Ak output from the absolute value calculation unit 118 as a candidate value for the symbol length involved in the generation of the peak position difference S111Ak (in other words, generation of the peak position difference S111Ak). Subtract from the peak position observation period involved in The subtraction result (hereinafter also referred to as a reference value) is output to the comparison unit 122 and the selection unit 123.

  The comparison unit 122 compares the absolute value of the peak position difference with the reference value and outputs the comparison result to the selection unit 123.

  Based on the comparison result by the comparison result unit 122, the selection unit 123 selects the smaller value of the absolute value of the peak position difference and the reference value.

  The smaller value selected by the selection unit 123 is input to the addition unit 119. The output S115Ak of the adder 119 is input to the adder 119 via the latch unit 120, as in the configuration example of FIG. Therefore, in the configuration of FIG. 12, when the absolute value of the peak position difference is larger than the reference value, cumulative addition is performed using the reference value instead of the absolute value of the peak position difference.

  Note that the same absolute value addition processing unit as in the example of FIG. 12 can be applied to the peak position difference calculation result signal S111Al other than the signal S111Ak.

  According to the configuration of FIG. 12, even when the peak position appears near the boundary of the observation period, the identity of the peak position can be accurately evaluated. This point will be described with reference to the schematic diagram of FIG.

  In the example of FIG. 13, the correlation signal is locally increased across the boundary between the continuous observation periods T1 and T2 (the length of each period is T). In the case of this example, in the previous observation period T1, the peak position P1 is detected near the end point of the period T1, and the value Q1 of the peak position P1 is a value close to the value of the observation period T1 (that is, the symbol length candidate value). I take the. On the other hand, in the later observation period T2, the peak position P2 is detected at the start point of the period T2, and the value Q2 of the peak position P2 is 0 (zero). For easy understanding, FIG. 13 shows the peak position P2 shifted from the starting point of the observation period T2.

  Therefore, in the example of FIG. 13, the absolute value of the peak position difference value Q1-Q2 is a large value close to the symbol length candidate value.

  However, since the peak positions P1 and P2 are inherently high in identity, the difference value between the peak positions P1 and P2 should be a small value. For example, the distance (specifically, the time length) δ from the peak position P1 to the peak position P2 is preferably acquired as a difference value between the peak positions P1 and P2. The distance δ between the peak positions P1 and P2 is calculated by {(symbol length candidate value T) − (absolute value of peak position difference Q1−Q2)} as can be seen from the illustration of FIG. That is, the distance δ is the above-described reference value that is an output of the subtraction unit 121 (see FIG. 12).

  Contrary to the above example, the same explanation as above applies to the case where the peak of the waveform straddling the observation periods T1 and T2 is within the observation period T2.

  Thus, by using the smaller value of the reference value and the absolute value of the peak position difference, the identity of the peak position can be accurately evaluated.

  According to the configuration of FIG. 12, it is not necessary to provide a separate peak position detection unit that detects a peak position in an observation period that is shifted from the observation period of the peak position detection unit 90. Therefore, a simple circuit configuration can reduce the cost, reduce the size of the apparatus, and the like.

Modification 3 of Embodiment 1
In the third modification, another configuration example of the peak position evaluation unit 110 will be described. FIGS. 14 and 15 show a configuration example according to the third modification of the peak position difference calculation processing unit 112Ak (see FIG. 7) and the absolute value addition processing unit 117Ak (see FIG. 7).

  The peak position difference calculation processing unit 112Ak illustrated in FIG. 14 has a configuration in which a subtraction unit 124 and a latch unit 125 are added to the peak position difference calculation processing unit 112Ak illustrated in FIG.

  The subtraction unit 124 receives the peak position detection result S90Ak directly and also receives the output of the latch unit 114 via the latch unit 125. That is, the peak position detection result S90Ak has two latch units 114 and 125. Is input via.

  In this case, the configuration including the two latch units 114 and 125 corresponds to means for holding the peak position detection result S90Ak and holding the peak position detection result S90Ak until the next input (peak position detection result S90Ak) occurs. . Then, the configuration outputs the held peak position detection result S90Ak as the holding ends.

  The subtracting unit 124 includes a peak position detection result S90Ak input to the holding unit including the latch units 114 and 125, and a peak position detection result S90Ak output from the holding unit (that is, a peak position detection result S90Ak that is input the previous time). ) And. Then, the subtraction unit 124 calculates and outputs the difference between the two inputs, that is, the peak position difference. In this case, the subtraction unit 124 calculates a peak position difference for every other peak position detection result S90Ak.

  Therefore, the peak position difference calculation processing unit 112Ak illustrated in FIG. 14 uses the difference value S111Ak1 calculated for the current and previous peak position detection results and the difference value S111Ak2 calculated for the current and previous peak position detection results. Output. The generic name of the two types of peak position difference calculation results S111Ak1 and S111Ak2 corresponds to the peak position difference calculation result signal S111Ak described in the first embodiment.

  The absolute value addition processing unit 117Ak illustrated in FIG. 15 has a configuration that can be adopted for the peak position difference calculation processing unit 112Ak in FIG. Specifically, as can be seen by comparing the configuration of FIG. 15 with the configuration of FIG. 9, an absolute value calculation unit 118 is provided for each of the two types of peak position difference calculation results S111Ak1 and S111Ak2. ing. The outputs of the two absolute value calculators 118 are added by the adder 126 and input to the adder 119 described above. Note that the addition unit 119 and the latch unit 120 described above are provided in the same manner as the configuration of FIG. 9 in the configuration of FIG.

  Note that the peak position difference calculation processing unit having the same configuration as that of FIG. 14 can be applied to the peak position detection result signal S90l other than the signal S90Ak. Further, an absolute value addition processing unit having the same configuration as that of FIG. 15 can be applied to the peak position difference calculation result signals other than the signals S111Ak1 and S111Ak2.

  By the way, when the symbol length candidate value involved in the generation of the peak position detection result A90Ak is different from the actual symbol length, the identity of the peak position is low. Therefore, by using the peak position detection result A90Ak obtained this time and the previous time as in the configurations of FIGS. 14 and 15, the peak position difference and further the absolute value thereof can be increased.

  On the other hand, when the symbol length candidate value is the same as the actual symbol length, the peak position is highly identical. Therefore, even if the current and previous peak position detection results A90Ak are used, The effect on the absolute value is small.

  Therefore, according to the configurations of FIGS. 14 and 15, the accuracy of symbol identification can be improved. This is particularly useful when the guard interval length is relatively small.

  In view of this point, it is possible to employ a configuration in which only the difference between the current and previous peak positions is used without using the difference between the current and previous peak positions.

  On the other hand, the accuracy of symbol identification can be further improved by using the two types of peak position differences as the targets of cumulative addition as in the configurations of FIGS. 14 and 15. Further, it is possible to identify a symbol with a small amount of data as compared with a configuration using only one of the above two types. For this reason, the time required for symbol identification can be shortened.

  Here, since the circuit configuration of FIG. 8 is simpler than the configuration of FIG. 14, cost reduction, downsizing of the apparatus, and the like can be achieved.

  It should be noted that whether to adopt the configuration of FIG. 14 or the configuration of FIG. 8 may be determined by, for example, comparatively considering a request for identification accuracy, a request for cost reduction, and the like.

  Here, the absolute value addition processing unit 117Ak illustrated in FIG. 16 can be applied to the peak position difference calculation processing unit 112Ak in FIG. In the configuration illustrated in FIG. 16, the portion constituted by the absolute value calculation unit 118, the subtraction unit 121, the comparison unit 122, and the selection unit 123 in the configuration of FIG. It is provided for each of the calculation results S111Ak1 and S111Ak2. The outputs of the two selection units 123 are added by the addition unit 126 and input to the addition unit 119. Note that the addition unit 119 and the latch unit 120 described above are provided in the same manner as the configuration of FIG. 12 in the configuration of FIG.

  Note that an absolute value addition processing unit having the same configuration as in FIG. 16 can be applied to the peak position difference calculation result signals other than the signals S111Ak1 and S111Ak2.

  According to the configuration of FIG. 16, both the effect of the configuration of FIG. 14 and the effect of the configuration of FIG. 12 can be obtained.

Embodiment 2. FIG.
FIG. 17 is a block diagram illustrating an OFDM symbol identification unit 217 according to the second embodiment. The symbol identification unit 217 can be applied to the reception device 10 (see FIG. 1) instead of the symbol identification unit 17 (see FIG. 1).

  The exemplary symbol identification unit 217 includes a delay unit 250, a correlation calculation unit 270, a peak position detection unit 290, a peak position evaluation unit 310, and an identification unit 330. These elements 250, 270, 290, 310, and 330 basically have the same functions as the elements 50, 70, 90, 110, and 130 according to the first embodiment.

  FIG. 18 is a block diagram illustrating the delay unit 250. The exemplary delay unit 250 has a configuration in which a selection unit 251 is added to the configuration illustrated in FIG. 3.

  The selection unit 251 acquires the delayed signals S50A, S50B, and S50C, and selectively outputs one of these delayed signals S50A, S50B, and S50C. Which of the delay signals S50A, S50B, and S50C is selected is controlled by a selection control signal S251 input to the selection unit 251. Thereby, for example, the delay signals S50A, S50B, and S50C are selected cyclically in a predetermined cycle. In the configuration of FIG. 18, the delay signal output from the selection unit 251 corresponds to the output signal S250 of the delay unit 250.

  For example, the delay unit 250 may be configured by combining the delay unit 50 and the selection unit 251 illustrated in FIG.

  The correlation calculation unit 270 can be configured using the correlation calculation unit 70 according to the first embodiment. The same applies to the peak position detection unit 290 and the peak position evaluation unit 310.

  Particularly, since the delayed signals S50A, S50B, and S50C are output sequentially as described above, in other words, in series, the correlation calculation unit 270, the peak position detection unit 290, and the peak position evaluation unit 310 are the same as those in the first embodiment. Compared to the correlation calculation unit 70, the peak position detection unit 90, and the peak position evaluation unit 110, a simple configuration is sufficient.

  For example, in the correlation calculation unit 270, the complex conjugate multiplication unit can be composed of one element corresponding to the complex conjugate multiplication processing unit 72A (see FIG. 5), and the moving average calculation unit is a moving average calculation processing unit 76Ak ( It can be configured by one element corresponding to FIG.

  Similarly, the peak position detection part 290 can be comprised by one element corresponded to the peak position detection process part 91Ak (refer FIG. 6), for example. Further, in the peak position evaluation unit 310, for example, the peak position difference calculation unit can be configured with one element corresponding to the peak position difference calculation processing unit 112Ak (see FIG. 7), and the absolute value addition unit has an absolute value. It can be configured by one element corresponding to the addition processing unit 117Ak (see FIG. 7).

  However, since the delay signals S50A, S50B, and S50C are switched and output from the delay unit 250, the correlation calculation unit 270 operates according to the type of the delay signal output from the delay unit 250.

  For example, when the delay signal S50A is output from the delay unit 250, the correlation calculation unit 270 sequentially switches the four types of moving average calculation periods Ak, Al, Am, An, and the complex conjugate multiplication result S71A (see FIG. 5). The moving average of is calculated. The same applies to the other delay signals S50B and S50C. That is, correlation calculation section 270 calculates the correlation in series for all combinations of candidate values for effective symbol length involved in generation of the output signal from delay section 250 and candidate values for guard interval length related thereto. Generate and output the result.

  The same applies to the peak position detection unit 290 and the peak position evaluation unit 310. For example, the peak position observation period and the data holding period such as the latch unit 114 are set according to the symbol length candidate value related to the signal to be processed.

  Each of the units 250, 270, 290, 310, for example, based on a candidate value switching control signal sent from a candidate value switching control unit (not shown), the effective symbol length and guard interval length applied to its own processing. It can be configured to switch candidate values. The selection control signal S251 (see FIG. 18) is an example of a candidate value switching control signal. The candidate value switching control unit can be configured to output a candidate value control signal at predetermined intervals using, for example, a timer.

  FIG. 19 is a block diagram illustrating the identification unit 330. The exemplary identification unit 330 has a configuration in which a storage unit 331 is added to the configuration illustrated in FIG. 11.

  The storage unit 331 sequentially stores the evaluation results output in series from the peak position evaluation unit 310. For example, the peak position evaluation result is stored in association with the effective symbol length and guard interval length candidate values involved in the evaluation result. Such association can be performed by the storage unit 331 or the peak position evaluation unit 310 in the previous stage using, for example, the candidate value switching control signal. Information stored in the storage unit 331 is used for processing by the minimum value determination unit 131.

  The minimum value determination unit 131 determines and selects the best result among the peak position evaluation results stored in the storage unit 331. Then, the minimum value determination unit 131 uses the effective symbol length and guard interval length candidate values involved in the selected signal as the effective symbol length and guard interval length of the complex baseband signal S13 input to the symbol identification unit 17. Authorize as.

  It should be noted that the identification unit 330 can be configured by removing the comparison unit 133 from the configuration of FIG.

  According to the OFDM symbol identification unit 217, processing is performed in series for all combinations of candidate values for effective symbol length and candidate values for guard interval length. Therefore, as described above, the number of constituent circuits can be reduced as compared with the symbol identification unit 17 according to the first embodiment. Therefore, reduction in circuit scale can reduce costs, reduce the size of the apparatus, and the like.

  Note that the parallel processing type symbol identification unit 17 is more suitable for high-speed processing than the serial processing type symbol identification unit 217. For this reason, for example, it is only necessary to determine which one of the symbol identification units 17 and 217 is adopted by comparing and considering the request for high-speed processing and the request for cost reduction.

Modification common to the first and second embodiments.
It is also possible to configure an OFDM symbol identification device using the configuration of the OFDM symbol identification units 17 and 217. Such an OFDM symbol identification device can be used alone or in combination with a separate OFDM receiver, for example.

  In addition, according to the configuration in which the analog processing unit 11, the A / D conversion unit 12, and the quadrature demodulation unit 13 are included in the above-exemplified OFDM symbol identification units 17 and 217, an analog OFDM signal is used as an input signal. An OFDM symbol identification unit or an OFDM symbol identification device applicable to the above can be configured.

  DESCRIPTION OF SYMBOLS 10 OFDM receiver, 17,217 OFDM symbol identification part (OFDM symbol identification apparatus), 50,250 delay part, 70,270 correlation calculation part, 90,290 Peak position detection part, 110,310 Peak position evaluation part, 113, 124, subtracting unit (subtracting unit), 114, 125 latching unit (holding unit), 130, 330 identification unit, A, B, C effective symbol length candidate values, Ak, Al, Am, An, Bk, Bl, Bm, Bn, Ck, Cl, Cm, Cn Guard interval length candidate values, S13 OFDM signal, S50A, S50B, S50C delay signal, S75Ak, S75Al, S75Am, S75An, S75Bk, S75Bl, S75Bm, S75Bn, S75Ck, S75Cl, S75Cm, S75Cn correlation calculation result, S90Ak, S9 0Al, S90Am, S90An, S90Bk, S90Bl, S90Bm, S90Bn, S90Ck, S90Cl, S90Cm, S90Cn Peak position detection result, S111Ak, S111Al, S111Am, S111An, S111Bk, S111Bl, S111Bm, S111CnS111S111C111S111S111 Position difference, S115Ak, S115Al, S115Am, S115An, S115Bk, S115Bl, S115Bm, S115Bn, S115Ck, S115Cl, S115Cm, S115Cn Cumulative addition result (peak position evaluation result).

Claims (11)

A delay unit that delays an input OFDM signal to generate a delayed signal;
A correlation calculating unit for calculating a correlation between the OFDM signal and the delayed signal;
A peak position detector for detecting the peak position of the correlation for each observation period of a predetermined time length;
A plurality of the detected peak positions, a peak position evaluation unit that evaluates the identity of the peak positions based on a peak position difference that is a difference between the plurality of peak positions;
A plurality of types of peak position evaluation results obtained by the peak position evaluation unit are acquired, and an effective symbol of the OFDM signal is obtained based on a peak position evaluation result having the best identity of the peak positions among the plurality of types of peak position evaluation results. An OFDM symbol identification device comprising: an identification unit for identifying a length and a guard interval length. The OFDM symbol identification device according to claim 1, wherein
The delay unit uses the effective symbol length candidate value as a delay time for generating the delayed signal,
The correlation calculation unit uses the guard interval length candidate value for calculating the correlation,
The peak position detection unit is a symbol that is a value obtained by adding the candidate values of the effective symbol length and the guard interval length involved in the correlation to be detected as the predetermined time length of the observation period Using long candidate values,
The identification unit determines the candidate value involved in the best peak position evaluation result among the candidate values of the effective symbol length and the guard interval length as the effective symbol length and the guard interval length of the OFDM signal. Certify as,
OFDM symbol identification device. The OFDM symbol identification device according to claim 1 or 2,
The said peak position evaluation part is an OFDM symbol identification apparatus which performs the cumulative addition of the absolute value of the said peak position difference, and produces | generates the said peak position evaluation result using the result of the said cumulative addition. The OFDM symbol identification device according to claim 3, wherein
When the absolute value of the peak position difference is larger than a reference value obtained by subtracting the absolute value of the peak position difference from the candidate value of the symbol length, the peak position evaluation unit An OFDM symbol identification device that performs the cumulative addition using the reference value instead of an absolute value. The OFDM symbol identification device according to any one of claims 1 to 4, comprising:
The peak position evaluation unit
First holding means for inputting the detection result of the peak position, holding and outputting the peak position detection result until the next input;
First subtracting means for calculating and outputting the peak position difference for the peak position detection result input to the first holding means and the peak position detection result output from the first holding means. An OFDM symbol identification device comprising: The OFDM symbol identification device according to any one of claims 1 to 5,
The peak position evaluation unit
A second holding unit that receives the detection result of the peak position, holds and outputs the peak position detection result until there is a next input; and
Second subtracting means for calculating and outputting the peak position difference for the peak position detection result input to the second holding means and the peak position detection result output from the second holding means. An OFDM symbol identification device comprising: The OFDM symbol identification device according to claim 6, comprising:
When the peak position evaluation unit includes the first holding unit, the first subtracting unit, the second holding unit, and the second subtracting unit, the first holding unit, Both the peak position difference calculated by the first subtracting means and the peak position difference calculated by the second holding means and the second subtracting means are targets of the cumulative addition, OFDM symbol identification device. The OFDM symbol identification device according to any one of claims 1 to 7,
The identification unit, when the best peak position evaluation result does not satisfy a predetermined criterion, determines that the identification accuracy of the effective symbol length and the guard interval length is insufficient.
OFDM symbol identification device. The OFDM symbol identification device according to any one of claims 2 to 8, comprising:
The delay unit outputs a plurality of the delayed signals corresponding to each of the candidate values of the effective symbol length in parallel,
The correlation calculation unit calculates the correlation between the OFDM signal and each of the plurality of delayed signals in parallel using each of the candidate values of the guard interval length, and the calculated plurality of correlations in parallel Output
The peak position detection unit performs detection of the peak position in parallel with respect to the plurality of correlations, and outputs in parallel a plurality of peak position detection results corresponding to the plurality of correlations,
The peak position evaluation unit performs the evaluation of the peak position in parallel with respect to the plurality of peak position detection results, and outputs the plurality of peak position evaluation results corresponding to the plurality of peak position detection results in parallel. To
An OFDM symbol identification device comprising: The OFDM symbol identification device according to any one of claims 2 to 8, comprising:
The delay unit outputs a plurality of the delay signals corresponding to each of the candidate values of the effective symbol length in series,
The correlation calculation unit calculates the correlation between the OFDM signal and each of the plurality of delayed signals in series using each of the candidate values of the guard interval length, and the calculated plurality of correlations are serially calculated. Output
The peak position detection unit serially detects the peak position for the plurality of correlations, and outputs a plurality of peak position detection results corresponding to the plurality of correlations in series,
The peak position evaluation unit serially evaluates the peak position with respect to the plurality of peak position detection results, and outputs the plurality of peak position evaluation results corresponding to the plurality of peak position detection results in series. To
An OFDM symbol identification device comprising:   An OFDM receiver comprising the OFDM symbol identification device according to any one of claims 1 to 10 as an OFDM symbol identification unit that identifies an effective symbol length and a guard interval length of a symbol of a received OFDM signal.

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