JP5658637B2 - Frequency error detection apparatus and program - Google Patents

Description

  The present invention relates to an apparatus and a program for receiving video, audio, or data using an orthogonal frequency division multiplexing (OFDM) transmission system and detecting a frequency error of the received OFDM signal.

  OFDM is one of the modulation methods used for wireless transmission, and is used in various transmission systems such as digital terrestrial broadcasting and wireless LAN. OFDM is a modulation scheme using a plurality of orthogonal subcarriers, and information on these subcarriers is transmitted in parallel. In a system using such an OFDM transmission system, if there is a signal frequency shift between the transmission side and the reception side, the orthogonality of each subcarrier is lost and the demodulated signal deteriorates.

  In the case of a terrestrial digital broadcasting system using the OFDM transmission system, since hundreds to thousands of subcarriers are used, the carrier interval becomes very narrow, and the influence of the frequency error on the demodulated signal becomes large. For this reason, the receiving side detects a frequency error of the received OFDM signal, performs a process of correcting the frequency error (automatic frequency control (AFC)), and then demodulates the OFDM signal.

  In general, there are narrowband AFC and wideband AFC in AFC for received OFDM signals. Narrowband AFC refers to control for correcting a frequency error within ± 1/2 of a subcarrier interval (narrowband frequency error) (see, for example, Non-Patent Document 1), and wideband AFC is, for example, a subcarrier interval. This is a control for correcting a frequency error (broadband frequency error) exceeding ± 1/2 of.

  Hereinafter, a conventional broadband AFC will be described. Here, the received OFDM signal will be described as a signal adopted in ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) which is a Japanese terrestrial digital broadcasting system. In ISDB-T, four types of pilot signals that are AC, TMCC, CP, and SP are defined. The power value of each pilot signal is boosted 16/9 times the average power value of the data symbols.

  FIG. 4 is a diagram showing the SP arrangement of ISDB-T. In FIG. 4, the horizontal axis represents frequency (subcarrier number), the vertical axis represents time (symbol number), and the vertical axes # 0 to # 3 represent SP sequence numbers. The SPs are distributed every 12 carriers in the carrier direction and every 4 symbols in the symbol direction, and are arranged in a cycle of 4 symbols. Sequence numbers # 0 to # 3 are numbers indicating which symbol arrangement pattern of the four symbols the SP arrangement corresponds to. Other AC, TMCC, and CP are arranged in preset subcarrier numbers.

  FIG. 5 is a diagram illustrating a pilot arrangement of AC and TMCC at the time of synchronous modulation in ISDB-T mode 3. Subcarrier numbers in which AC (AC1_1,..., AC1_8) and TMCC (TMCC1,..., TMCC4) are arranged are shown for segment numbers 0 to 12 in the OFDM segment frame. For example, in the OFDM segment frame of segment number 11, the pilot signal of AC1_1 is arranged at subcarrier number 10, and the pilot signal of TMCC1 is arranged at subcarrier number 70. In this way, in ISDB-T mode 3, AC and TMCC are arranged at predetermined numbers within subcarrier numbers 0 to 431 of one symbol.

  FIG. 6 is a block diagram showing the configuration of a conventional broadband AFC unit (frequency error detection device). The conventional broadband AFC unit 150 includes a power calculation unit 151, a correlation calculation unit (integrated power value calculation unit) 152, and a maximum position detection unit (maximum value determination unit) 153. The broadband AFC unit 150 inputs an FFT output signal for each subcarrier, which is a frequency domain signal obtained by orthogonal demodulation and fast Fourier transform (FFT) of the OFDM signal, and calculates a power value for each subcarrier. The integrated power value of the subcarrier corresponding to the predetermined pilot arrangement information is calculated within a predetermined range where the subcarrier number is slid, and the maximum integrated power value of each integrated power value in the predetermined range is determined. Then, the number of subcarrier number slides at the maximum integrated power value is detected. As described above, the broadband AFC unit 150 detects a frequency error for correcting a frequency error equal to or greater than the subcarrier interval, and outputs the detected frequency error as broadband frequency information.

  The power calculation unit 151 receives an FFT output signal for each subcarrier that is a frequency domain signal, squares the amplitude value of each subcarrier, calculates a power value, and calculates the power value for each subcarrier. It outputs to 152.

  Correlation calculation section 152 receives the power value for each subcarrier from power calculation section 151, and AC, TMCC, and CP arrangement information (AC, TMCC, and CP arrangement information reflecting the subcarrier number on the frequency axis) From the memory (not shown), the power values of the subcarriers corresponding to the read AC, TMCC, and CP arrangement information are integrated in one symbol (all subcarriers), and the integrated power value is stored in the maximum position detecting unit 153. Output. Further, the correlation calculation unit 152 slides the subcarrier number indicated by the AC, TMCC, and CP arrangement information read from the memory by one carrier, and integrates the power value of the subcarrier when it is slid by one carrier in one symbol. The integrated power value is output to the maximum position detector 153. Furthermore, correlation calculation section 152 calculates an integrated power value when a predetermined number of subcarrier numbers indicated by AC, TMCC, and CP arrangement information read from the memory are slid. As described above, the correlation calculation unit 152 sets the integrated power value at the subcarrier number indicated by the read AC, TMCC, and CP arrangement information, and the integrated power value when each carrier is slid for each predetermined range. Is output to the maximum position detector 153 as the integrated power value.

  Here, AC, TMCC, and CP are pilot signals used for frequency error detection, and are fixedly arranged at predetermined subcarrier numbers as described above. It is assumed that AC, TMCC, and CP arrangement information that can specify a subcarrier number on the frequency axis is stored in advance in the memory.

  The maximum position detection unit 153 inputs the respective integrated power values in the predetermined range from the correlation calculation unit 152, determines the maximum integrated power value among these integrated power values in the predetermined range, and determines the maximum integrated power. The number of slide carriers of the subcarrier number in the value is detected, and this is output to the outside as a frequency error.

  FIG. 7 is a first image diagram for explaining the frequency error detection process. The correlation calculation unit 152 shown in FIG. 6 shows the integrated power value of the subcarrier number indicated by the AC, TMCC, and CP arrangement information read from the memory. The processing to be obtained is shown. FIG. 8 is a second image diagram for explaining the frequency error detection processing. The correlation calculation unit 152 shown in FIG. 6 slides the subcarrier number indicated by the AC, TMCC, and CP arrangement information read from the memory by one carrier. The process which calculates | requires the integrated electric power value when making it show is shown.

  7 and 8, the horizontal axis indicates the frequency axis of the subcarrier number, and the vertical axis indicates the power value for each subcarrier. The arrow near the power value 1 represents the power value of the data carrier, and the arrow near the power 16/9 represents the power value of the boosted pilot signal, which is higher than the power value of the data carrier. The power value is larger. The AC, TMCC, and CP arrangement information in the middle stage of FIGS. 7 and 8 shows an example, and the position of the subcarrier used for frequency error detection (subcarrier number), that is, the position of the pilot signal used for frequency error detection is shown. Is sequence information composed of 1 or 0 in each subcarrier number in one symbol, with 1 being placed at each subcarrier position (subcarrier number) not used for frequency error detection. It can be seen that the AC, TMCC and CP arrangement information shown in FIG. 8 is shifted by one carrier compared to the AC, TMCC and CP arrangement information (subcarrier number read from the memory) shown in FIG. In this case, in FIG. 7, the upper subcarrier numbers corresponding to AC, TMCC, and CP arrangement information of 1 are 9, 27, and the power values of these subcarrier numbers 9, 27 are the power values of the data carriers. . In contrast, in FIG. 8, the upper subcarrier numbers corresponding to AC, TMCC, and CP arrangement information of 1 are 10, 28, and the power values of these subcarrier numbers 10, 28 are AC power values. .

  7 and 8, the horizontal axis indicates the frequency axis of the subcarrier number, and the vertical axis indicates the power value of the subcarrier corresponding to the arrangement information of 1. As described above, the correlation calculation unit 152 shown in FIG. 6 corresponds to the power values of the subcarriers remaining in the signal bandwidth shown in the lower part of FIG. 7 and FIG. The integrated power value can be obtained by integrating the subcarrier power value). In other words, correlation calculation section 152 can slide the subcarrier number within a predetermined range and obtain the integrated power value at that time.

  From the power values of the subcarriers shown in the lower part of FIGS. 7 and 8, it can be seen that the integrated power value is larger in FIG. 8 than in FIG. In FIG. 8, the pilot signal arrangement indicated by the AC, TMCC, and CP arrangement information matches the actual pilot signal arrangement, and the power value of the subcarrier shown in the lower part of FIG. This is because the power value of the pilot signal is larger than that. Thus, if the number of slide carriers at the maximum integrated power value among the integrated power values obtained by sliding for each carrier within a predetermined range is known, the frequency error can be detected.

Takashi Seki and two others, “Examination of new frequency synchronization method using guard period in OFDM”, Television Society Technical Report, August 24, 1995, ITE Technical Report Vol.19, No.38, pp.13 -18, BCS '95 -42, BFO '95 -49, ROFT '95 -49 (Aug. 1995)

  The maximum position detector 153 of the wideband AFC unit 150 shown in FIG. 6 has a specific pilot signal power value of the data carrier when the boost ratio (pilot signal power ratio) is the same for all pilot signals. The frequency error is detected by utilizing the fact that it is larger than the average power value. However, the maximum position detector 153 cannot correctly detect the frequency error when the boost ratio differs between pilot signals.

  FIG. 9 is a conceptual diagram illustrating frequency error detection processing of OFDM signals having different pilot signal boost ratios, and assumes a case where the power value of the SP of the ISDB-T wave is twice that of the prior art. 9, the horizontal axis indicates the frequency axis of the subcarrier number, and the vertical axis indicates the power value for each subcarrier, as in the upper stages of FIGS. 7 and 8. The arrow near the power value 1 represents the power value of the data carrier, the arrow near the power 16/9 represents the boosted AC power value, and the arrow near the power 32/9 represents the boosted SP power value. Thus, the power value of AC is larger than that of the data carrier, and the power value of SP is larger than that of AC. The middle stage AC, TMCC, and CP arrangement information in FIG. 9 shows an example as in the middle stage in FIGS. The upper subcarrier number corresponding to 1 in the AC, TMCC, and CP arrangement information is 12, and the power value of the subcarrier number 12 is the SP power value.

  The integrated power value calculated by correlation calculation section 152 corresponds to AC, TMCC, and CP arrangement information of 1 when the subcarrier corresponding to AC, TMCC, and CP arrangement information of 1 is SP (see FIG. 9). It becomes larger than the case where the subcarrier is other than SP. That is, the integrated power value calculated based on the AC, TMCC, and CP arrangement information used for frequency error detection is greatly influenced by the SP having a large power value.

  Thus, in the conventional broadband AFC unit 150 shown in FIG. 6, when the boost ratio differs between pilot signals, the pilot signal having the largest power value (SP in FIG. 9) greatly affects the integrated power value. Therefore, there is a problem that the frequency error cannot be detected correctly. Specifically, when the power value of the pilot signal or data carrier that is not the reference when calculating the integrated power value is larger than the power value of the pilot signal that is the reference (for example, as shown in FIG. 9, When the power value of the SP that is not the reference is larger than the power value of the AC that is the reference), the pilot signal having the largest power value in the subcarrier corresponding to AC, TMCC, and CP arrangement information of 1 (not the reference) When the pilot signal is included, the integrated power value becomes a large value, and even if the maximum integrated power value is determined, the frequency error cannot be detected correctly.

  Therefore, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide a frequency capable of correctly detecting a frequency error even in an OFDM signal in which pilot signals having different boost ratios are mixed. An object of the present invention is to provide an error detection device and a program.

  In order to achieve the above object, a frequency error detection apparatus according to the present invention is an apparatus for detecting a frequency error of an OFDM signal in which a plurality of types of pilot signals are mixed, for each subcarrier obtained by performing FFT on the OFDM signal. Based on a power calculation unit that calculates a power value for each subcarrier from a signal, pilot arrangement information indicating a position where a pilot signal is arranged on a subcarrier, and a pilot boost ratio indicating a boost ratio of the pilot signal, Integrated power value calculation for dividing the power value calculated for the subcarrier corresponding to the position of the pilot signal indicated by the pilot arrangement information by the pilot boost ratio of the pilot signal and calculating the integrated power value based on the division result And the position of the pilot signal indicated by the pilot arrangement information within a predetermined range Of the integrated power values calculated by sliding the number of subcarriers, the maximum integrated power value is determined, and the frequency error of the OFDM signal is determined based on the number of carriers slid at the maximum integrated power value. And a maximum value determination unit for detecting.

  Further, in the frequency error detection apparatus according to the present invention, the integrated power value calculation unit is a first pilot indicating a position where a predetermined type of pilot signal that is a target for calculating the integrated power value is arranged on a subcarrier. Arrangement information, second pilot arrangement information indicating positions of pilot signals other than the predetermined type among a plurality of types of pilot signals mixed in the OFDM signal, and pilot boost ratios indicating respective boost ratios in the pilot signals. And dividing the power value calculated for the subcarrier corresponding to the position of each pilot signal indicated by the first pilot arrangement information and the second pilot arrangement information by the pilot boost ratio of the pilot signal. The integrated power value is calculated based on the division result.

  Also, in the frequency error detection apparatus according to the present invention, the integrated power value calculation unit indicates a position where a predetermined type of first pilot signal that is a target for calculating the integrated power value is arranged on a subcarrier. 1 pilot arrangement information, and when a second pilot signal other than the predetermined type out of a plurality of types of pilot signals mixed in the OFDM signal is arranged in one period with a predetermined number of symbols, the predetermined number of symbols The first pilot arrangement information using the second pilot arrangement information indicating the position of the second pilot signal in the sequence number corresponding to each and the pilot boost ratio indicating each boost ratio in the pilot signal And subcarriers corresponding to the positions of the respective pilot signals indicated by the second pilot arrangement information The calculated power value is divided by a pilot boost ratio of the pilot signal, an integrated power value is calculated based on the division result, and the maximum value determination unit is a pilot indicated by the first pilot arrangement information. The position of the signal is slid by the number of subcarriers within a predetermined range, and the maximum integrated power value among the integrated power values calculated for each sequence number indicated by the second pilot arrangement information is determined, and the maximum The frequency error of the OFDM signal is detected based on the number of carriers slid at the integrated power value, and the sequence number at the maximum integrated power value is detected.

  Furthermore, a frequency error detection program according to the present invention causes a computer to function as the frequency error detection device.

  As described above, according to the present invention, it is possible to correctly detect the frequency error of an OFDM signal in which pilot signals having different boost ratios are mixed.

It is a block diagram which shows the structure of the OFDM signal receiver containing the wideband AFC part (frequency error detection apparatus) by embodiment of this invention. It is a block diagram which shows the structure of a wideband AFC part. It is a flowchart which shows the process of a broadband AFC part. It is a figure which shows SP arrangement | positioning of ISDB-T. It is a figure which shows the pilot arrangement | positioning of AC and TMCC at the time of the synchronous modulation in the mode 3 of ISDB-T. It is a block diagram which shows the structure of the conventional broadband AFC part. It is a 1st image figure explaining a frequency error detection process. It is a 2nd image figure explaining a frequency error detection process. It is an image figure explaining the frequency error detection process of the OFDM signal from which the boost ratio of a pilot signal differs.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention equalizes power values of pilot signals having different boost ratios based on information on the arrangement of pilot signals and boost ratios, calculates an integrated power value using the equalized power values, and generates a frequency error of the OFDM signal. Is detected. As a result, even if the boost ratio is different between pilot signals, the power value of the pilot signal is made equal to calculate the integrated power value, so that the pilot signal with the largest power value greatly affects the integrated power value. Therefore, a correct frequency error can be detected.

[OFDM signal receiver]
First, an OFDM signal receiving apparatus including a wideband AFC (frequency error detection apparatus) according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of an OFDM signal receiving apparatus. The OFDM signal receiving apparatus 1 includes an orthogonal demodulation unit 10, a complex multiplication unit 11, an FFT unit 12, a demodulation unit 13, a narrowband AFC unit 14, and a wideband AFC unit 15.

  When the OFDM signal receiving apparatus 1 receives an OFDM signal transmitted by an OFDM signal transmitting apparatus (not shown), the orthogonal demodulation unit 10 inputs the received OFDM signal, orthogonally demodulates the OFDM signal, and performs an equivalent baseband signal. Is output to the complex multiplier 11.

  The complex multiplier 11 receives an equivalent baseband signal from the quadrature demodulator 10, and receives narrowband frequency error information from the narrowband AFC unit 14 and wideband frequency error information from the wideband AFC unit 15. The complex multiplication unit 11 generates a phase rotation coefficient so as to cancel these frequency errors based on the narrow band frequency error information and the wide band frequency error information, and converts the phase rotation coefficient into an equivalent baseband signal. Complex multiplication. Thereby, the frequency error of the equivalent baseband signal can be corrected. The equivalent baseband signal after correcting the frequency error is distributed and input to the FFT unit 12 and the narrowband AFC unit 14, respectively.

  The narrowband AFC unit 14 receives the equivalent baseband signal from the complex multiplication unit 11, detects a frequency error for correcting a frequency error within ± 1/2 of the subcarrier interval, and serves as narrowband frequency error information. Output to the complex multiplier 11. In order to detect a frequency error in a narrow band, a method based on the correlation of guard intervals added to the equivalent baseband signal is used. For details, see, for example, Non-Patent Document 1 described above.

  The FFT unit 12 receives the equivalent baseband signal from the complex multiplication unit 11, performs FFT on the equivalent baseband signal in the effective symbol period, and generates a signal for each subcarrier. A frequency domain signal that is a signal for each subcarrier, that is, an FFT output signal for each subcarrier, is distributed and input to the demodulation unit 13 and the broadband AFC unit 15.

  The demodulator 13 receives the FFT output signal for each subcarrier from the FFT unit 12, performs demodulation processing such as demapping, deinterleaving, and decoding, and restores transmission information from the OFDM signal transmission apparatus. Since demodulation processing such as demapping is already known, the description thereof is omitted.

The broadband AFC unit 15 receives an FFT output signal for each subcarrier from the FFT unit 12, and
The power value for each subcarrier is calculated, and the power values of pilot signals having different boost ratios are made equal based on AC, TMCC and CP allocation information, SP allocation information, AC, TMCC and CP boost ratio, and SP boost ratio. Then, using this equalized power value, the integrated power value is calculated within a predetermined range where the subcarrier number is slid. Then, the broadband AFC unit 15 determines the maximum integrated power value among the respective integrated power values in the predetermined range, and detects the number of slide carriers of the subcarrier number in the maximum integrated power value. As described above, the broadband AFC unit 15 outputs the detected number of slide carriers to the complex multiplier 11 as broadband frequency information for correcting a frequency error equal to or greater than the subcarrier interval.

[Broadband AFC section (frequency error detector)]
Next, the broadband AFC unit 15 shown in FIG. 1 will be described. FIG. 2 is a block diagram showing a configuration of the broadband AFC unit 15. The broadband AFC unit 15 includes a power calculation unit 151, a correlation calculation unit (integrated power value calculation unit) 16, and a maximum position detection unit (maximum value determination unit) 153. The wideband AFC unit 15 correctly detects the frequency error even when the boost ratio is the same between the pilot signals and even when the boost ratio is different between the pilot signals. Specifically, even if the pilot signal or data carrier power value is larger than the reference pilot signal power value when calculating the integrated power value, the frequency error of the OFDM signal Can be detected correctly.

  Comparing the conventional broadband AFC unit 150 shown in FIG. 6 with the broadband AFC unit 15 shown in FIG. 2, both broadband AFC units 150 and 15 are provided with a power calculation unit 151 and a maximum position detection unit 153. Are the same. On the other hand, the broadband AFC unit 15 is different in that the correlation calculation unit 16 is different from the correlation calculation unit 152 of the broadband AFC unit 150. Comparing the input information, the correlation calculation unit 152 of the wideband AFC unit 150 inputs AC, TMCC, and CP arrangement information that reflects the subcarrier number of the pilot signal that is the reference for calculating the integrated power value. On the other hand, the correlation calculation unit 16 of the wideband AFC unit 15 is not the same AC, TMCC, and CP arrangement information, but is not a reference for calculation of the integrated power value, and the SP subcarrier number whose power value is larger than AC or the like Is different in that SP arrangement information, AC, TMCC, CP boost ratio, and SP boost ratio reflecting the above are also input.

FIG. 3 is a flowchart showing the processing of the broadband AFC unit 15. When the FFT output signal for each subcarrier input to the power calculation unit 151 of the broadband AFC unit 15 is F (k) (k is a subcarrier number), the power calculation unit 151 includes the FFT output signal F (k for each subcarrier. ) (Step S301), the amplitude value of the FFT output signal F (k) is squared to obtain a power value F (k) × F (k) ^* for each subcarrier, and is output to the correlation calculation unit 16 (Step S302). Here, * represents a complex conjugate.

The correlation calculation unit 16 inputs the power value F (k) × F (k) ^* for each subcarrier from the power calculation unit 151, and from the memory (not shown), AC, TMCC, and CP arrangement information P ′ ( k), SP arrangement information SP (i, k) (i is the SP sequence number, k is the subcarrier number), AC, TMCC, CP boost ratio r _P , and SP boost ratio r _SP are read (step S303). Here, AC, TMCC, CP arrangement information P ′ (k) and SP arrangement information SP (i, k) are the subcarrier numbers where the pilot signals are arranged in all subcarrier numbers constituting one symbol. 1 and a sequence of 0s in other subcarrier numbers.

The correlation calculation unit 16 performs total pilot weight information P _all (P _all () including weights for equalizing the power values of pilot signals indicated by AC, TMCC, CP arrangement information P ′ (k) and SP arrangement information SP (i, k). i, k) using AC, TMCC and CP arrangement information P ′ (k), SP arrangement information SP (i, k), AC, TMCC and CP boost ratio r _P , and SP boost ratio r _SP (Step S304).
P _all (i, k) = P ′ (k) / r _P + SP (i, k) / r _SP

Here, the total pilot weight information P _all (i, k) is a weight capable of equalizing the pilot signal power value by multiplying the pilot signal power value F (k) × F (k) ^*. It is a sequence consisting of The weights at the positions of AC, TMCC and CP are P _all (i, k) = P ′ (k) / r _P = 1 / r _P , and the weight at the position of SP is P _all (i, k) = SP. (I, k) / r _SP = 1 / r _SP . In the example of FIG. 9, assuming that the AC boost ratio r _P = 16/9 and the SP boost ratio r _SP = 32/9, the total pilot weight information P _all (i, k) = _{9/16 at} the AC position is obtained. All pilot weight information P _all (i, k) at the position of SP is _9/32 .

例えば、所定範囲である探索スライドキャリア数の範囲を−５０≦α≦５０（αは整数）とすると、１０１×４＝４０４通りの積算電力値Ｓ（ｉ，α）が求められる。 The correlation calculation unit 16 sets the number (slide carrier number) α to slide the subcarrier number within a predetermined range (within the number of search slide carriers) (step S305). In the case of the first process, the number of slide carriers α is set to 0, and the subcarrier number is not slid. Then, the correlation calculation unit 16 multiplies the power value F (k + α) × F (k + α) ^* for each subcarrier by the total pilot weight information P _all (i, k), where N is the total number of subcarriers in the OFDM signal. Then, the integrated power value (correlation value) S (i, α) is obtained by the following equation and output to the maximum position detecting unit 153 (step S306).

For example, assuming that the range of the number of search slide carriers that is a predetermined range is −50 ≦ α ≦ 50 (α is an integer), 101 × 4 = 404 integrated power values S (i, α) are obtained.

In the equation (1), the subcarrier number k of the power value F (k) × F (k) ^* for each subcarrier is slid, but the total pilot weight information P _all (i, k) The subcarrier number k may be slid.

In the example of FIG. 9, the multiplication result of the AC power value F (k + α) × F (k + α) ^* and the total pilot weight information P _all (i, k) is (16/9) × (9/16) = The result of SP multiplication is (32/9) × (9/32) = 1. The power value of SP is larger than that of AC, but by multiplying power value F (k + α) × F (k + α) ^* by all pilot weight information P _all (i, k), the case of AC and the value of SP The power value F (k + α) × F (k + α) ^* × P _all (i, k) can be made equal to each other, and the equal power value F (k + α) × F (k + α) ^* × P _all (i, k) The accumulated power value S (i, α) can be calculated using k).

  The correlation calculation unit 16 determines whether or not all the slide carrier numbers α have been set within a predetermined range (step S307), and determines that all the slide carrier numbers α have been set (step S307). : Y), the process proceeds to step S308, and if it is determined that all the slide carrier numbers α have not been set (step S307: N), the process proceeds to step S305, and a new slide carrier number α is set within a predetermined range. .

  The maximum position detection unit 153 moves from step S307, inputs the number of slide carriers α and the integrated power value S (i, α) for each SP sequence number i from the correlation calculation unit 16, and these integrated power values The maximum value is determined, and the slide carrier number α and the SP sequence number i at the maximum integrated power value S (i, α) are detected (step S308). Then, the maximum position detection unit 153 outputs the detected number of slide carriers α to the outside as a wideband frequency error, and the detected sequence number i of the SP is a sequence number i (in FIG. 4) indicating the arrangement of SPs in the symbol. (Sequence number of any of # 0 to # 3) is output to the outside. The detected number of slide carriers α may be positive. It may be negative.

As described above, according to the wideband AFC unit 15 (frequency error detection device) according to the embodiment of the present invention, the power calculation unit 151 determines whether the power value for each subcarrier is the amplitude value of the FFT output signal F (k) for each subcarrier. The power value is obtained, and the correlation calculation unit 16 performs AC, TMCC and CP arrangement information P ′ (k), SP arrangement information SP (i, k), AC, TMCC, CP boost ratio r _P , and SP boost ratio r _SP. Is used to obtain all pilot weight information P _all (i, k) including weights for equalizing the power values of the pilot signals, and the number of slide carriers α is set within a predetermined range, and the power value F for each subcarrier is set. The integrated power value (correlation value) S (i, α) is obtained by multiplying (k + α) × F (k + α) ^* by all pilot weight information P _all (i, k). Then, the maximum position detecting unit 153 determines the maximum value among the integrated power values S (i, α) for each of the slide carrier number α and the SP sequence number i, and the maximum integrated power value S (i, α). ) And the sequence number i of the SP are detected, the detected slide carrier number α is set as a wideband frequency error, and the detected SP sequence number i is output as a sequence number i indicating the SP arrangement in the symbol. I tried to do it. Thus, even for an OFDM signal in which pilot signals having different boost ratios are mixed, the power value F (k + α) × F (k + α) ^* for each subcarrier is multiplied by all pilot weight information P _all (i, k). By doing so, the power value for calculating the integrated power value becomes equal in all pilot signals indicated by AC, TMCC, CP arrangement information P ′ (k) and SP arrangement information SP (i, k). Therefore, the integrated power value is not affected by the pilot signal having the largest power value, and is calculated assuming that the power values of all pilot signals are equal. The SP sequence number i can be detected correctly, and the frequency error and the SP sequence number in the symbol can be detected correctly.

  As a hardware configuration of the broadband AFC unit 15 according to the embodiment of the present invention, a normal computer can be used. The broadband AFC unit 15 is configured by a computer including a volatile storage medium such as a CPU and a RAM, a non-volatile storage medium such as a ROM, an interface, and the like. The functions of the power calculation unit 151, the correlation calculation unit 16, and the maximum position detection unit 153 included in the broadband AFC unit 15 are realized by causing the CPU to execute a program describing these functions. These programs can also be stored and distributed in a storage medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), optical disk (CD-ROM, DVD, etc.), semiconductor memory, or the like.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea thereof. The present invention is not only applied to the OFDM signal receiving apparatus 1 shown in FIG. 1, but also a measuring apparatus, a compensating apparatus, and an OFDM signal that receive video, audio, or data using the OFDM transmission method and measure the OFDM signal. This also applies to a relay device that relays In short, the present invention is also applicable to an apparatus including a frequency error detection apparatus that is the broadband AFC unit 15.

DESCRIPTION OF SYMBOLS 1 OFDM signal receiver 10 Orthogonal demodulation part 11 Complex multiplication part 12 FFT part 13 Demodulation part 14 Narrow band AFC part 15,150 Wide band AFC part (frequency error detection apparatus)
16, 152 Correlation calculation unit (integrated power value calculation unit)
151 Power calculation unit 153 Maximum position detection unit (maximum value determination unit)

Claims (4)

In an apparatus for detecting a frequency error of an OFDM signal in which a plurality of types of pilot signals are mixed,
A power calculator that calculates a power value for each subcarrier from a signal for each subcarrier obtained by performing FFT on the OFDM signal;
Based on the pilot arrangement information indicating the position where the pilot signal is arranged on the subcarrier and the pilot boost ratio indicating the boost ratio of the pilot signal, the subcarrier corresponding to the position of the pilot signal indicated by the pilot arrangement information is calculated. An integrated power value calculation unit that divides the power value by a pilot boost ratio of the pilot signal and calculates an integrated power value based on the division result;
Among the integrated power values calculated by sliding the position of the pilot signal indicated by the pilot arrangement information within a predetermined range by the number of subcarriers, a maximum integrated power value is determined, and the maximum integrated power value is A maximum value determination unit for detecting a frequency error of the OFDM signal based on the number of carriers slid;
A frequency error detection apparatus comprising: The frequency error detection device according to claim 1,
The integrated power value calculation unit
First pilot arrangement information indicating a position where a predetermined type of pilot signal that is a target for calculating the integrated power value is arranged on a subcarrier, and the predetermined type among a plurality of types of pilot signals mixed in the OFDM signal The first pilot arrangement information and the second pilot arrangement information are obtained by using second pilot arrangement information indicating the positions of pilot signals other than and pilot boost ratios indicating respective boost ratios in the pilot signal. The power value calculated for the subcarrier corresponding to each pilot signal position shown is divided by the pilot boost ratio of the pilot signal, and an integrated power value is calculated based on the division result Frequency error detection device. The frequency error detection device according to claim 1,
The integrated power value calculation unit
Of the plurality of types of pilot signals mixed in the OFDM signal, first pilot arrangement information indicating a position where a predetermined type of first pilot signal to be calculated for calculating the integrated power value is arranged on a subcarrier. A second pilot signal indicating a position of the second pilot signal in a sequence number corresponding to each of the predetermined number of symbols when the second pilot signals other than the predetermined type are arranged in one cycle with a predetermined number of symbols; Corresponding to the positions of the respective pilot signals indicated by the first pilot arrangement information and the second pilot arrangement information, using the pilot arrangement information of the first pilot arrangement information and the pilot boost ratio indicating the respective boost ratios in the pilot signal. The power value calculated for the subcarrier is used as a pilot block of the pilot signal. Divided by the strike ratio to calculate an integrated power value based on the division result,
The maximum value determination unit
The position of the pilot signal indicated by the first pilot arrangement information is slid within the predetermined range by the number of subcarriers, and the maximum of the integrated power values calculated for each sequence number indicated by the second pilot arrangement information is Determining the integrated power value, detecting the frequency error of the OFDM signal based on the number of carriers slid at the maximum integrated power value, and detecting the sequence number at the maximum integrated power value. A frequency error detection apparatus characterized by the above.   A frequency error detection program for causing a computer to function as the frequency error detection device according to any one of claims 1 to 3.

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