JP2017112583A - Ofdm transmission device and ofdm reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a synchronization performance and transmission efficiency by matching a head of an error-correcting code with a head of an OFDM frame even in the case where a pilot insertion ratio is changed.SOLUTION: An OFDM transmission device 1 performs processing using a preset pilot insertion ratio PR, a code length L, a coding rate CR, a block number BN and the like in such a manner that a head of an error-correcting code is matched with a head of an OFDM frame. An error-correcting coding part 10 reads a segment number N, a modulation multilevel index M, the code length L, the block number BN corresponding to the coding rate CR and the pilot insertion ratio PR and a zero insertion number ZN for each block from a table 14 and performs normal error-correcting coding or error-correcting coding with shortening for each block. An OFDM framing part 12 constitutes an OFDM frame by disposing a modulation signal and a control signal such as TMCC including the pilot insertion ratio PR, the code length L and the like at predetermined frequency positions.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) transmitter and an OFDM receiver for next-generation terrestrial digital broadcasting.

  Conventionally, terrestrial digital broadcasting (ISDB-T) has been operated in accordance with a standard defined by ARIB (Radio Industry Association) (see Non-Patent Document 1). In this conventional digital terrestrial broadcasting, the transmission side matches the block length of the error correction code (outer code) with the OFDM frame length. Thereby, on the receiving side, the synchronization signal of the error correction code and the TSP (Transport Stream Packet) can be easily reproduced along with the synchronization processing of the OFDM signal.

  As described above, in the conventional terrestrial digital broadcasting, the synchronization performance is enhanced by matching the block length of the error correction code with the OFDM frame length. Also, since the OFDM signal does not require a header region indicating the relationship between the error correction code and the OFDM frame, transmission efficiency can be increased. Furthermore, a header adding function is unnecessary on the transmitting side, a decoding function is unnecessary on the receiving side, and a function for controlling the head position is also unnecessary.

  By the way, in next-generation terrestrial digital broadcasting, use of a block code having a high correction capability is being studied in order to improve reception characteristics. Further, LDPC (Low Density Parity Check: Low) adopted in the DVB-T2 transmission system (see Non-Patent Document 2) and the advanced broadband satellite digital broadcasting (Advanced BS) transmission system (see Non-Patent Document 3). Density parity check) codes are also being considered.

  The error correction code length of DVB-T2 is 16,200 bits or 64,800 bits, and the advanced BS uses 44,880 bits. Further, in order to further improve the reception characteristics, a spatially coupled LDPC code having an error correction code length of 200,000 bits or more has been studied (see Non-Patent Document 4).

ARIB STD-B31 ETSI EN 302 755 ARIB STD-B44 Asakura et al., "Transmission technology for next-generation terrestrial broadcasting-A study on spatially coupled LDPC codes-", Eiji Technical Report vol.37, no.39, BCT2013-90, 2013, p.9-12

  In mode 3 of conventional terrestrial digital broadcasting (ISDB-T), the number of data carriers per OFDM frame of one segment is 78,336 (= 384 × 204). When QPSK is used as the modulation method, the number of bits allocated per OFDM frame of one segment is 156,672 (= 78,336 × 2).

  This number of bits (156,672 bits) is 96 times the error correction code length (1,632 (= 204 × 8) bits) of RS code (Reed-Solomon code) (156,672 = 1,632 × 96), but error correction of LDPC code It is not an integral multiple of the code length (16,200, 64,800, 44,880 bits).

  That is, when the RS code is used as the error correction code, the head of the error correction code and the head of the OFDM frame match, but when the LDPC code is used, these heads do not match.

  On the other hand, in next-generation terrestrial digital broadcasting, it is assumed that transmission parameters such as a pilot pattern according to a pilot insertion ratio will be diversified in consideration of operation in various environments. For example, in DVB-T2 adopted in Europe, eight types (four types of pilot insertion ratios) are set as pilot patterns of a SISO (Single Input Single Output) system and can be selected during operation.

  In conventional terrestrial digital broadcasting (ISDB-T), hierarchal transmission is performed with 12 segment parts transmitting high-definition and 1 segment part transmitting one segment, but transmission is performed with the same pilot insertion ratio. ing. That is, there is one type of pilot pattern of the pilot insertion ratio, and 1/12 = 0.08333... Is used as the pilot insertion ratio.

  As described above, in next-generation terrestrial digital broadcasting, it is assumed that a pilot pattern having a different pilot insertion ratio is used for each segment, such as arranging many pilots in a mobile reception segment.

  However, in conventional terrestrial digital broadcasting (ISDB-T), since there is only one type of pilot pattern, if the technology is applied to next-generation terrestrial digital broadcasting as it is, next-generation terrestrial digital broadcasting supports pilot patterns. It is difficult to select transmission parameters flexibly.

  Here, in the next-generation terrestrial digital broadcasting, even in a system that has a long error correction code length and allows a plurality of pilot insertion ratios, transmission parameters can be flexibly selected, and conventional terrestrial digital broadcasting (ISDB-T) It is desirable to be able to achieve the same synchronization performance and transmission efficiency as in the above, and reduce the functions on the transmission and reception side.

  Therefore, the present invention has been made to solve the above-described problem, and its purpose is to make the head of the error correction code coincide with the head of the OFDM frame even when the pilot insertion ratio is changed. Therefore, an object of the present invention is to provide an OFDM transmitter and an OFDM receiver that can improve synchronization performance and transmission efficiency.

  In order to solve the above-mentioned problem, the OFDM transmitter according to claim 1 performs error correction coding on data to be transmitted, carrier-modulates the error correction code, converts the modulated signal into an OFDM frame, and performs IFFT on the signal of the OFDM frame. In an OFDM transmission apparatus that transmits an OFDM signal, a relation between an error correction code length and the number of bits of data to be transmitted corresponding to all the modulation signals arranged in the OFDM frame is a positive integer ratio. The error correction code length is set in advance, and the error correction code of the error correction code length is obtained by performing error correction coding on predetermined data for each block having the number of blocks corresponding to the pilot insertion ratio. Perform normal error correction coding to be generated, or perform error correction coding by inserting zero bits of a predetermined number of zero insertions into predetermined data And generating error correction code length code, and deleting the predetermined zero insertion number of zero bits from the code to generate the error correction code and performing error correction coding with shortening An encoding unit; a carrier modulation unit that performs carrier modulation in accordance with preset modulation multilevel information on the error correction code generated by the error correction encoding unit; and generates the modulation signal; and the carrier modulation An OFDM framing unit that configures the OFDM frame by arranging the modulation signal generated by a unit at a predetermined position, and when the error correction coding unit has a preset pilot insertion ratio, When the normal error correction coding is performed for the block and the preset pilot insertion ratio is changed, the previous block is changed for all the blocks. Perform error correction coding with shortening, or perform error correction coding with shortening for a part of all the blocks, and perform normal error correction coding for the remaining blocks It is characterized by performing.

  Further, the OFDM transmitter according to claim 2 performs error correction coding on data to be transmitted, carrier modulates the error correction code, converts the modulated signal into an OFDM frame, and performs OFDM processing on the OFDM frame signal to transmit an OFDM signal. In the transmission apparatus, a table storing the number of blocks and the number of zero insertions for each block corresponding to the number of segments, modulation multilevel information, error correction code length, coding rate, and pilot insertion ratio, and preset segments Number, modulation multi-level information, error correction code length, coding rate, and pilot insertion ratio, for each block of the number of blocks, an error correction coding process is performed on the transmission target data, and the error correction code is An error correction encoding unit to be generated and a preset variable for the error correction code generated by the error correction encoding unit. A carrier modulation unit that performs carrier modulation according to multi-value information and generates the modulation signal; an OFDM frame conversion unit that arranges the modulation signal generated by the carrier modulation unit at a predetermined position and constitutes the OFDM frame; The error correction encoding unit from the table, the number of blocks corresponding to the preset number of segments, modulation multilevel information, error correction code length, coding rate and pilot insertion ratio, and for each block The zero insertion number is read out, and error correction coding is performed on predetermined data for the block having the zero insertion number of 0, the error correction code having a preset error correction code length is generated, and the zero insertion number is 0. For a block that is not, the first data is generated by inserting zero bits of the zero insertion number into predetermined data, and the first data is erroneous Performing positive encoding, generating a first code of the preset error correction code length, and deleting the zero bits of the number of zero insertions from the first code to generate the error correction code. Features.

An OFDM transmission apparatus according to claim 3 is the OFDM transmission apparatus according to claim 2, wherein the number of segments is N _seg , and the modulation multilevel number is 2 when the modulation multilevel information is the modulation multilevel number. Is an exponent when expressed by a power of N, N _{d is} the number of data carriers per symbol of the OFDM frame, S _{f is} the number of symbols of the OFDM frame, L is the error correction code length, a predetermined positive integer or When a positive integer number is a, the mathematical formula: N _seg × M × N _d × S _f = a × L is satisfied.

  An OFDM transmission apparatus according to claim 4 is the OFDM transmission apparatus according to claim 2, wherein the transmission corresponding to all the modulation signals arranged in the OFDM frame as the preset error correction code length. When a positive integer multiple or a positive integer value is used for the number of bits of the target data and the pilot insertion ratio is set in advance, the error correction coding unit When the predetermined data is subjected to error correction coding, the error correction code having the preset error correction code length is generated, and the preset pilot insertion ratio is changed, As the number of zero insertions per block, according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame The error correction encoding unit generates the first data by inserting zero bits of the zero insertion number into the predetermined data for all the blocks of the number of blocks, and generates the first data as the first data. Performing error correction coding, generating the first code of the preset error correction code length, and deleting the zero bits of the number of zero insertions from the first code to generate the error correction code; It is characterized by that.

  An OFDM transmission apparatus according to claim 5 is the OFDM transmission apparatus according to claim 2, wherein the transmission corresponding to all the modulation signals arranged in the OFDM frame as the preset error correction code length. When a positive integer multiple or a positive integer value is used for the number of bits of the target data and the pilot insertion ratio is set in advance, the error correction coding unit When the predetermined data is subjected to error correction coding, the error correction code having the preset error correction code length is generated, and the preset pilot insertion ratio is changed, As the number of zero insertions per block, according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame And the error correction coding unit inserts zero bits of the zero insertion number into the predetermined data for a part of the blocks having the number of zero insertions of which the number of zero insertions is not zero. Generate first data, perform error correction coding on the first data, generate the first code having the preset error correction code length, and generate the zero insertion number from the first code. The error correction code is generated by deleting the zero bits of the block, and the error correction coding is performed on the predetermined data for the other blocks in which the zero insertion number is not 0 among all the blocks of the number of blocks, and the preset value is set. The error correction code having the error correction code length generated is generated.

  Furthermore, the OFDM receiver of claim 6 receives an OFDM signal from the OFDM transmitter of claim 1, performs FFT on the OFDM signal, equalizes the signal after FFT, carrier-demodulates the signal after equalization, In an OFDM receiver that restores original data by error correction decoding of a signal after carrier demodulation, carrier demodulation is performed on the equalized signal according to the same modulation multilevel information as that of the OFDM transmitter, and a demodulated signal is obtained. A carrier demodulator to be generated, and for each block of the number of blocks corresponding to the pilot insertion ratio, the original data is restored by performing error correction decoding on the demodulated signal having the same error correction code length as that of the OFDM transmitter. Or by subtracting a predetermined number of zero insertions from the same error correction code length as that of the OFDM transmitter, and demodulating the length of the subtraction result The first demodulated signal having the same error correction code length as that of the OFDM transmitter is generated by inserting zero bits of the predetermined number of zero insertions into the signal, error correction decoding is performed on the first demodulated signal, and error correction decoding is performed. An error correction decoding unit that performs error correction decoding with extension to delete the predetermined zero insertion number of zero bits from a later signal and restore the original data, and the error correction decoding unit includes the OFDM transmission In the case of the same pilot insertion ratio as that of the apparatus, the normal error correction decoding is performed for all blocks, and when the same pilot insertion ratio as that of the OFDM transmitter is changed, all the blocks Error correction decoding with extension, or error correction decoding with extension of some of all the blocks Performed for the remaining blocks, performs the usual error correction decoding, characterized in that.

  An OFDM receiver according to claim 7 receives an OFDM signal from the OFDM transmitter according to claim 2 or 3, performs FFT on the OFDM signal, equalizes the signal after FFT, and performs carrier demodulation on the equalized signal. In the OFDM receiver that restores the original data by performing error correction decoding on the carrier demodulated signal, a block corresponding to the number of segments, modulation multilevel information, error correction code length, coding rate, and pilot insertion ratio A table in which the number and the number of zero insertions for each block are stored, and a carrier demodulation unit that performs carrier demodulation in accordance with the same modulation multilevel information as the OFDM transmission device and generates a demodulated signal for the equalized signal, The number of blocks corresponding to the same number of segments, modulation multilevel information, error correction code length, coding rate, and pilot insertion ratio as in the OFDM transmitter An error correction decoding unit that performs error correction decoding processing on the demodulated signal generated by the carrier demodulation unit and restores original data, and the error correction decoding unit is configured to transmit the OFDM transmission from the table. Read the number of blocks corresponding to the same number of segments, modulation multi-level information, error correction code length, coding rate and pilot insertion ratio as the device and the number of zero insertions for each block, and for the block where the number of zero insertions is 0, Error correction decoding is performed on the demodulated signal having the same error correction code length as that of the OFDM transmission apparatus, the original data is restored, and the block having a nonzero zero insertion number from the same error correction code length as that of the OFDM transmission apparatus Same as the OFDM transmitter by subtracting the number of zero insertions and inserting zero bits of the number of zero insertions into the demodulated signal of the length of the subtraction result A first demodulated signal having a correction code length is generated, error correction decoding is performed on the first demodulated signal, and zero bits of the zero insertion number are deleted from the signal after error correction decoding to restore the original data It is characterized by that.

  An OFDM receiving apparatus according to claim 8 is the OFDM receiving apparatus according to claim 7, wherein the OFDM receiving apparatus receives an OFDM signal from the OFDM transmitting apparatus according to claim 4 instead of the OFDM transmitting apparatus according to claim 2 or 3. As the same error correction code length as that of the OFDM transmitter, the value is a positive integer multiple or a positive integer for the number of bits of data to be transmitted corresponding to all modulated signals arranged in the OFDM frame. 1 is used, and when the pilot insertion ratio is the same as that of the OFDM transmitter, the error correction decoding unit performs the demodulation of the demodulated signal having the same error correction code length as that of the OFDM transmitter for all blocks. When error correction decoding is performed, the original data is restored, and the same pilot insertion ratio as the OFDM transmitter is changed, As the number of zero insertions for each block, a number corresponding to a change in the number of bits of the data to be transmitted corresponding to all the modulation signals arranged in the OFDM frame is used, and the error correction decoding unit, For all the blocks, the number of zero insertions is subtracted from the same error correction code length as that of the OFDM transmitter, and the zero bits of the number of zero insertions are inserted into the demodulated signal having the length of the subtraction result. A first demodulated signal having the same error correction code length is generated, error correction decoding is performed on the first demodulated signal, and zero bits of the zero insertion number are deleted from the signal after error correction decoding to restore the original data It is characterized by.

  An OFDM receiving apparatus according to claim 9 is the OFDM receiving apparatus according to claim 7, wherein the OFDM receiving apparatus receives an OFDM signal from the OFDM transmitting apparatus according to claim 5 instead of the OFDM transmitting apparatus according to claim 2 or 3. And a value that is a positive integer multiple of the number of bits of data to be transmitted corresponding to all the modulation signals arranged in the OFDM frame, as the same error correction code length as that set in the OFDM transmitter, or When a positive integer value is used and the pilot insertion ratio is the same as that of the OFDM transmitter, the error correction decoding unit has the same error correction code length as that of the OFDM transmitter for all blocks. The demodulated signal is subjected to error correction decoding, the original data is restored, and the same pilot insertion ratio as that of the OFDM transmitter is changed. In this case, the number of zero insertions for each block is a number corresponding to a change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame, and the error correction is performed. The decoding unit subtracts the number of zero insertions from the same error correction code length as the OFDM transmitter for a part of the blocks in which the number of zero insertions is not 0, and the length of the subtraction result Inserting zero bits of the zero insertion number into the demodulated signal to generate a first demodulated signal having the same error correction code length as that of the OFDM transmitter, performing error correction decoding on the first demodulated signal, and after error correction decoding The original data is restored by deleting the zero bits of the number of zero insertions from the signal of, and the OFD of all the blocks in which the number of zero insertions is not 0 It performs error correction decoding on the demodulated signals of the same error correction code length and the transmission device, to restore the original data, characterized in that.

  As described above, according to the present invention, even when the pilot insertion ratio is changed, the head of the error correction code and the head of the OFDM frame can be matched to improve synchronization performance and transmission efficiency. be able to.

In the first embodiment, the number of segments N _seg = 12, M = 2 when the modulation multilevel number is 2 to the M power, and the number of symbols S _f per OFDM frame and the error when the parameter a = 24,48 It is a figure which shows the example of a combination of the correction code length L. FIG. In the second embodiment, the number of segments N _seg = 1, M = 2 when the modulation multilevel number is 2 to the M power, and the number of symbols S _f per OFDM frame and the error correction code when the parameter a = 1 It is a figure which shows the example of a combination of length L. FIG. In the third embodiment, the number of segments N _seg = 1, M = 2 when the modulation multi-level number is 2 to the M power, and the number of symbols S _f per OFDM frame and the error when the parameter a = 1/3 It is a figure which shows the example of a combination of the correction code length L. FIG. It is a figure which shows the segment parameter of the mode 3 of ISDB-T. In Example 1, it is a figure explaining the error correction encoding process etc. in the case of pilot insertion ratio 1/12. FIG. 6 is a diagram for explaining a first method in the first embodiment when the pilot insertion ratio is 1/6 without changing the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/12. It is. FIG. 6 is a diagram for explaining a second method in the case where the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/12 are not changed in the first embodiment and the pilot insertion ratio is 1/6. It is. In Example 3, it is a figure explaining the error correction encoding process etc. in the case of pilot insertion ratio 1/24. FIG. 10 is a diagram for explaining a first method in the third embodiment when the pilot correction ratio is 1/12 without changing the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/24. It is. It is a block diagram which shows the structural example of the OFDM transmitter by embodiment of this invention. It is a figure which shows the structural example of the table 14 at the time of using a 1st method. It is a figure which shows the structural example of the table 14 at the time of using a 2nd method. It is a block diagram which shows the structural example of the OFDM receiver by embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention performs shortening by inserting a predetermined number of zero bits into data to be transmitted at the time of error correction coding when the pilot insertion ratio is changed in the OFDM transmission apparatus. Further, according to the present invention, when the pilot insertion ratio is changed in the OFDM receiver, a process corresponding to the error correction coding on the transmission side is performed at the time of error correction decoding.

  As a result, even if the pilot insertion ratio is changed, the head of the error correction code and the head of the OFDM frame can be matched without changing the error correction code length, and synchronization performance and transmission efficiency can be improved. Can be improved.

  The error correction code length is n (a positive integer) with respect to the number of data carriers per OFDM frame (corresponding to the number of bits in the modulation signal of all transmission target data arranged in the OFDM frame) at a predetermined pilot insertion ratio. ) A value of 1 / n or a value of n times is used.

  For example, when the pilot insertion ratio is changed to a value larger than a predetermined pilot insertion ratio, the number of data carriers per OFDM frame decreases. The OFDM transmitter inserts zero bits into data to be transmitted, performs error correction coding with the same error correction code length, and then deletes the inserted zero bits (performs error correction coding with shortening).

  Since the number of data carriers in the OFDM frame has decreased, by performing reduction processing using zero bits during error correction coding, the length of the error correction code after error correction coding with shortening and the OFDM frame Corresponding to the number of data carriers. The OFDM receiver performs error correction decoding corresponding to error correction coding with shortening.

[Error correction code length and OFDM frame length]
First, an error correction code length and an OFDM frame length that can match the head of the error correction code with the head of the OFDM frame will be described. In the first embodiment described below, the same segment parameters as in ISDB-T mode 3 are applied, and the total number of carriers per segment and one OFDM symbol is 432, AC / TMCC is 12, and pilot insertion ratio is 1 /. An example in the case of 12, 1/6 is shown. The second embodiment shows an example in which the total number of carriers per segment and one OFDM symbol is 216, AC / TMCC is 6, and pilot insertion ratio is 1/24, 1/12, and 1/6. In the third embodiment, as in the second embodiment, the total number of carriers per segment and 1 OFDM symbol is 216, the AC / TMCC is 6, and the pilot insertion ratio is 1/24, 1/12, 1/6. In this case, an example in which an error correction code length longer than that in the second embodiment is used will be described.

  In the first and second embodiments, when the error correction code length is 1 / n (positive integer) with respect to the number of data carriers per OFDM frame, that is, a plurality of error correction codes are one OFDM. The case where it is stored in a frame is shown. In the third embodiment, when the error correction code length is n times the number of data carriers per OFDM frame, that is, one error correction code is divided and a plurality of divided error correction codes are obtained. The case where each is stored in a plurality of OFDM frames is shown.

[Example 1]
First, the error correction code length and the OFDM frame length in the first embodiment will be described. In the first embodiment, the same segment parameters as in ISDB-T mode 3 are applied, the total number of carriers per segment and one OFDM symbol is 432, the AC / TMCC is 12, the pilot insertion ratio is 1/12, 1 / An example in the case of 6 is shown. Here, an LDPC code of a block code is used as the inner code, and an example in which the head of the LDPC code matches the head of the OFDM frame is shown. The same applies to Example 2 and Example 3 described later.

FIG. 4 is a diagram showing segment parameters in ISDB-T mode 3, and shows a case where a GI (Guard Interval) ratio = 1/8. In Example 1, 432 as the total number of carriers per 125/126 = 0.99206 ··· kHz, 1 segment and 1OFDM symbol as carrier spacing shown in FIG. 4, 36, etc. as the number of 384, SP as the number of data carriers _{N d} Apply.

First, it is necessary to satisfy the following expression as a condition for matching the head of the error correction code with the head of the OFDM frame.
[Formula 1]
N _seg × M × N _d × S _f = a × L (1)
Here, the parameter a is a positive integer. Further, when the modulation multilevel number is expressed by a power of 2 (modulation multilevel number B = 2 ^M ), the index is M, that is, the number of bits allocated to each signal point corresponding to the modulation multilevel number on the IQ plane is M. . Furthermore, the number of data carriers per segment and one OFDM symbol is N _d , the number of symbols per OFDM frame is S _f , the code length of the error correction code (error correction code length) is L, and the number of segments used in the layer is N _seg And The left side and right side of Equation (1) indicate the number of data (number of bits) per OFDM frame.

By obtaining the number of data carriers N _d , the number of symbols S _f, and the error correction code length L that satisfy Equation (1), the head of the error correction code and the head of the OFDM frame can be matched. Here, in addition to the equation (1), other conditions are added as conditions for matching the head of the error correction code with the head of the OFDM frame.

First as other conditions, to unify the pilot arrangement in the first symbol of the OFDM frame, the symbol number S _f, it is necessary to be a multiple of the symbol interval D _y of the pilot. According to the ISDB-T and DVB-T2 standards, the pilot symbol interval Dy = 1, 2, 4 is considered as a candidate, so the number of symbols _Sf is a multiple of 4.

In addition, the time length of the OFDM frame is set to 200 ms to 300 ms, which is the same as that of conventional terrestrial digital broadcasting (ISDB-T), and the time required for synchronization establishment and channel switching is made comparable. Therefore, in the case of mode 3 and GI ratio = 1/8, it is necessary to satisfy 180 ≦ S _f ≦ 264.

  As another condition, secondly, in order to make the bit interleaving effect equal to the block of the error correction code, error correction is performed in the assumed multi-value number (QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM). It is necessary to arrange the beginning of the code at the beginning of the bit string assigned to the data carrier. Therefore, the error correction code length L needs to be a multiple of the least common multiple 120 of M = 2, 4, 6, 8, 10, 12 when the modulation multi-level number is 2 to the Mth power. As a result, DVB-T2 coding rate CR = 1/2, 3/5, 2/3, 4/5, 5/6, and advanced BS coding rate CR = xx / 120 are also supported. Can do. xx is a positive integer.

In summary, the conditions for matching the head of the error correction code with the head of the OFDM frame are the following <a> to <c>.
<a> Satisfying the above formula (1) <b> The number of symbols S _f is a multiple of 4 (in the case of mode 3 and GI ratio = 1/8, 180 ≦ S _f ≦ 264)
<C> The error correction code length L is a multiple of 120.

(Pilot insertion ratio 1/12: Example 1)
Under these conditions, when the pilot insertion ratio is 1/12, the error correction code length L and the number of symbols S _f for matching the beginning of the error correction code and the beginning of the OFDM frame are determined as follows. The

As shown in FIG. 4, when AC / TMCC is 12 and SP is 36 (= 432/12) out of a total of 432 carriers per segment and OFDM symbol, data carriers per segment and OFDM symbol the number _{N d} is the 384 (= 432-12-36). In addition, when M is an even number when the modulation multi-level number is 2 to the power of M, if the above equation (1) is satisfied when the modulation method is QPSK (M = 2), The mathematical formula (1) is satisfied.

Therefore, the mathematical formula (1) is expressed as follows.
[Formula 2]
N _seg × 2 (M) × 384 (N _d ) × 4 × S _f ′ = a × 120 × L ′ (2)
Here, the number of symbols S _f = 4 × S _f ′, and the error correction code length L = 120 × L ′. The parameter a is a positive integer.

The mathematical formula (2) is expressed as follows.
N _seg × 2 × 64 × S _f '= a × 5 × L ′
By reducing the parameter a, the error correction code length L can be set longer, and by increasing the parameter a, the error correction code length L can be set shorter.

According to the above equation, the parameter S _f ′ is a multiple of 5, and the symbol number S _f is 180 ≦ S _f ≦ 264 when the mode 3 and the GI ratio = 1/8, so the parameter S _f ′ is 45 ≦ S _f ′ ≦ 66. Therefore, there are five possible values of parameter S _f ′: 45, 50, 55, 60, 65.

FIG. 1 shows the number of symbols per OFDM frame when the number of segments N _seg = 12, M = 2 when the number of modulation multivalues is 2 to the Mth power, and parameter a = 24,48 in the first embodiment. It is a figure which shows the example of a combination of _Sf and error correction code length L. FIG.

As shown in FIG. 1, an example of a combination of the number of symbols S _f and the error correction code length L is as follows: (parameter number S _f , error correction code length L) = (180, 69, 120), ( 200, 76, 800), etc., and when parameter a = 48, (180, 34, 560), (200, 38, 400), etc. Further, the error correction code length L can be set longer by decreasing the parameter a, and the error correction code length L can be set shorter by increasing the parameter a.

(Pilot insertion ratio 1/6: Example 1)
Next, a case will be described in which the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/12 are not changed, and the pilot insertion ratio 1/6 is used. Here, when the pilot insertion ratio is changed from 1/12 to 1/6, the number of pilots increases and the number of data decreases in one OFDM frame. When the pilot insertion ratio is low, it means that the data ratio is high in one OFDM frame, and when the pilot insertion ratio is high, it means that the data ratio is low in one OFDM frame.

In FIG. 1, a case where the number of segments N _seg = 12, M = 2 when the modulation multilevel number is 2 to the Mth power, parameter a = 24, number of symbols S _f = 200, and error correction code length L = 76,800. explain. By pilot insertion ratio is changed from 1/12 to 1/6, 1 segment and 1OFDM the number of data carriers _{N d} per symbol, 348 384 (= 432-12-432 / 12) (= 432-12 -432/6). Then, the number of bits per OFDM frame decreases from 24 × 76,800 (= 12 × 2 × 384 × 200 = 1,843,200) to 24 × 69,600 (= 12 × 2 × 348 × 200 = 1,670,400).

  There are two methods in this case (methods corresponding to the pilot insertion ratio 1/6 without changing the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/12). The first method is to shorten all error correction code blocks at the time of error correction coding. In the second method, some error correction code blocks are shortened at the time of error correction encoding.

(First method)
First, the first method will be described. As described above, the first method shortens all error correction code blocks at the time of error correction coding. FIG. 5 is a diagram for explaining error correction coding processing and the like when the pilot insertion ratio is 1/12 in the first embodiment. FIG. 6 shows a first method in the first embodiment in which the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/12 are not changed, and the pilot insertion ratio is 1/6. FIG. The number of error correction code blocks per OFDM frame is 24.

  As shown in FIG. 5, when the pilot insertion ratio is 1/12, the OFDM transmitter converts the data D of a predetermined length into each of all (24) error correction code blocks at the time of error correction coding. On the other hand, error correction coding is performed (step S501). As a result, an error correction code having an error correction code length L = 76,800 bits composed of data D and parity is generated. The OFDM transmitter configures an OFDM frame of 76,800 × 24 = 1,843,200 bits based on the error correction codes of all (24) error correction code blocks (step S502).

  On the other hand, as shown in FIG. 6, when the pilot insertion ratio is 1/6, the OFDM transmitter performs 7,200 (= 76,800−69,600) for each of all error correction code blocks at the time of error correction coding. Shorten bits. The shortening refers to a process in which zero bits (zero bits) are inserted into predetermined data to perform error correction coding, and the inserted zero bits are not transmitted.

  Specifically, the OFDM transmitter inserts 7,200 zero bits at a predetermined position (for example, a rear position) of data D ′ having a predetermined length for each of all (24) error correction code blocks ( Step S601). Then, the OFDM transmitter performs error correction coding on the data D ′ and zero bits (step S602). As a result, an error correction code consisting of data D ′, zero bits and parity and having an error correction code length of 76,800 bits is generated. The data D 'is the number of bits determined according to the coding rate CR.

  The OFDM transmitter deletes the zero bit inserted in step S601 from the error correction code having the error correction code length L = 76,800 bits (step S603). As a result, an error correction code (error correction code after shortening) having a code length of 69,600 bits, which is composed of data D ′ and parity, is generated. In error correction coding accompanying such shortening, the position of the zero bit to be inserted is set in advance, so that the accuracy of error correction decoding in the OFDM receiver increases, and transmission characteristics can be improved.

  The OFDM transmitter configures an OFDM frame of 69,600 × 24 = 1,670,400 bits based on the error correction codes (error correction codes after shortening) of all (24) error correction code blocks (step S604).

  In this way, it is possible to correspond to the pilot insertion ratio 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/12. That is, even when the pilot insertion ratio is changed from 1/12 to 1/6, the head of the error correction code and the head of the OFDM frame can always be matched. All error correction coding and error correction decoding processes can be made uniform.

  Also, by using the first technique, error correction coding with the same shortening is performed for a plurality of error correction code blocks, so that a plurality of different processes are not required, and the processing load can be reduced.

  In addition, when performing hierarchical transmission, even if the pilot insertion ratio is set to 1/6 in one layer and the pilot insertion ratio in another layer is set to 1/12, the same error correction code is used in the two layers. A long error correction code can be used. And the head of an error correction code and the head of an OFDM frame can always be made to correspond.

  Note that the receiving-side OFDM receiving apparatus performs processing opposite to the processing shown in FIGS.

(Second method)
Next, the second method will be described. As described above, the second method shortens some error correction code blocks at the time of error correction coding. FIG. 7 shows a second method in the first embodiment in which the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/12 are not changed and the pilot insertion ratio is 1/6. FIG. The number of error correction code blocks per OFDM frame is 22.

  As shown in FIG. 7, when the pilot insertion ratio is 1/6, the OFDM transmitter performs error correction coding on 21 error correction code blocks among all (22) error correction code blocks. For each, normal processing is performed without shortening. Further, the OFDM transmission apparatus shortens 19,200 bits (= 76,800−57,600) for the remaining one error correction code block.

  Specifically, the OFDM transmitter performs error correction coding on data D having a predetermined length for each of 21 error correction code blocks (step S701). As a result, an error correction code having an error correction code length L = 76,800 bits composed of data D and parity is generated.

  The OFDM transmission apparatus inserts 19,200 zero bits at a predetermined position (for example, the rear position) of the data D ″ having a predetermined length for one error correction code block (step S702). Error correction coding is performed on the data D ″ and zero bits (step S703). As a result, an error correction code having an error correction code length L = 76,800 bits, which includes data D ″, zero bits, and parity, is generated.

  The OFDM transmitter deletes the zero bit inserted in step S702 from the error correction code having the error correction code length L = 76,800 bits generated in step S703 (step S704). As a result, an error correction code (shortened error correction code) having a code length of 57,600 bits, which is composed of data D ″ and parity, is generated.

  Then, the OFDM transmitter is based on the error correction code of 21 error correction code blocks and the error correction code (error correction code after shortening) of one error correction code block, 76,800 × 21 + 57,600 × 1. = 1,670,400 bits OFDM frame is constructed (step S705, step S706).

  In this way, it is possible to correspond to the pilot insertion ratio 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/12. That is, even when the pilot insertion ratio is changed from 1/12 to 1/6, the head of the error correction code and the head of the OFDM frame can always be matched.

  Moreover, since the number of error correction code blocks can be reduced by using the second method, the number of error correction encoding processes can be reduced, and the processing load can be reduced. In the above-described example, in the first method, the number of error correction code blocks per OFDM frame is 24, but in the second method, it can be 22 and the number can be reduced.

  In addition, when performing hierarchical transmission, even if the pilot insertion ratio is set to 1/6 in one layer and the pilot insertion ratio in another layer is set to 1/12, the same error correction code is used in the two layers. A long error correction code can be used. And the head of an error correction code and the head of an OFDM frame can always be made to correspond.

In the example of FIG. 7, the number of error correction code blocks to be shortened is 1, but the number is changed according to the coding rate CR of error correction coding, the number of segments N _seg , and the like. May be. Further, the receiving-side OFDM receiving apparatus performs a process reverse to the process shown in FIG. In addition, when using a small coding rate CR (for example, 1/5) such that the number of bits of data D is smaller than the number of zero bits to be inserted, an error correction code length shortened according to the coding rate CR, The number or the error correction code length to be shortened and the number of zero bits may be set.

[Example 2]
Next, the error correction code length and the OFDM frame length in the second embodiment will be described. The second embodiment shows an example in which the total number of carriers per segment and one OFDM symbol is 216, AC / TMCC is 6, and pilot insertion ratio is 1/24, 1/12, and 1/6.

  The condition for matching the head of the error correction code with the head of the OFDM frame is to satisfy the above formula (1) as in the first embodiment, and considering other conditions, the above <a> to < c>.

(Pilot insertion ratio 1/24: Example 2)
Under these conditions, when the pilot insertion ratio is 1/24, the error correction code length L and the number of symbols S _f for matching the head of the error correction code with the head of the OFDM frame are determined as follows. The

For pilot insertion ratio 1/24, 1 segment and because 1OFDM is set to six per the AC / TMCC of the total number 216 pieces of carrier symbols, the number of data carriers per segment and 1OFDM symbol _{N d} is 201 (= 216 −6−216 / 24 = 216−6−9). As in the first embodiment, when M is an even number when the modulation multilevel number is 2 to the Mth power, if the modulation method is QPSK (M = 2) and all of the equations (1) are satisfied, all In the even number M, the formula (1) is satisfied.

Therefore, the mathematical formula (1) is expressed as follows.
[Formula 3]
N _seg × 2 (M) × 201 (N _d ) × 4 × S _f ′ = a × 120 × L ′ (3)
Here, the number of symbols S _f = 4 × S _f ′, and the error correction code length L = 120 × L ′. The parameter a is a positive integer.

The mathematical formula (3) is expressed as follows.
N _seg × 67 × S _f '= a × 5 × L'
By reducing the parameter a, the error correction code length L can be set longer, and by increasing the parameter a, the error correction code length L can be set shorter.

From the above equation, the parameter S _f ′ is a multiple of 5, and the symbol number S _f is 180 ≦ S _f ≦ 264 in the case of mode 3 and GI ratio = 1/8, so the parameter S _f ′ is 45 ≦ S _f ′ ≦ 66. Therefore, the possible values of the parameter S _f ′ are 45, 50, 55, 60, 65.

FIG. 2 shows a symbol number S _f per OFDM frame when the number of segments N _seg = 1, M = 2 when the modulation multilevel number is 2 to the Mth power, and the parameter a = 1 in the second embodiment. 4 is a diagram illustrating a combination example of error correction code length L. FIG.

As shown in FIG. 2, examples of combinations of the number of symbols S _f and the error correction code length L are (symbol number S _f , error correction code length L) = (180, 72, 360), (200, 80, 400), (220, 88,440), (240,96,480), etc.

(Pilot insertion ratio 1/12 / 1/6: Example 2)
Next, a case will be described in which the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/24 are not changed, and the pilot insertion ratios 1/12/1/6 are used.

In FIG. 2, a case where the number of segments N _seg = 1, M = 2 when the modulation multilevel number is 2 to the Mth power, parameter a = 1, number of symbols S _f = 200, and error correction code length L = 80,400 explain. By pilot insertion ratio is changed to 1/12 from 1/24, 1 segment and 1OFDM the number of data carriers _{N d} per symbol, from 201 (= 216-6-216 / 24 = 216-6-9) It decreases to 192 (= 216−6−216 / 12 = 216−6−18). Then, the number of bits per OFDM frame decreases from 80,400 × 1 (= 1 × 2 × 201 × 200) to 76,800 × 1 (= 1 × 2 × 192 × 200).

In addition, by pilot insertion ratio is changed to 1/6 from 1/24, 1 segment and 1OFDM the number of data carriers _{N d} per symbol, 201 (= 216-6-216 / 24 = 216-6-9 ) To 174 (= 216−6−216 / 6 = 216−6−36). Then, the number of bits per OFDM frame decreases from 80,400 × 1 (= 1 × 2 × 201 × 200) to 69,600 × 1 (= 1 × 2 × 174 × 200).

  The method in this case (a method of corresponding to the pilot insertion ratios of 1/12 and 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio of 1/24) is described above. There are the same first method and second method. The first method is to shorten all error correction code blocks at the time of error correction coding. In the second method, some error correction code blocks are shortened at the time of error correction encoding.

  When the pilot insertion ratio is 1/24, the OFDM transmitter on the transmission side performs error correction coding on the data D of a predetermined length for all (one) error correction code blocks at the time of error correction coding. And an error correction code having an error correction code length of 80,400 bits is generated. Then, the OFDM transmitter configures an OFDM frame of 80,400 bits based on the error correction codes of all (one) error correction code blocks.

  On the other hand, in the first method, when the pilot insertion ratio is 1/12, the OFDM transmitter performs 3,600 bits (= 80,400-76,800) for each of all error correction code blocks at the time of error correction coding. Shortening. When the pilot insertion ratio is 1/6, the OFDM transmission apparatus shortens 10,800 bits (= 80,400-69,600) for each of all error correction code blocks at the time of error correction coding.

  The processing of the OFDM transmitter when the first method is used is the same as that in the case where the number of error correction code blocks is one in FIG.

  Thus, it is possible to correspond to the pilot insertion ratios 1/12 and 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/24. That is, even when the pilot insertion ratio is changed from 1/24 to 1/12, 1/6, the head of the error correction code and the head of the OFDM frame can always be matched. All error correction coding and error correction decoding processes can be made uniform.

  In addition, when performing hierarchical transmission, the pilot insertion ratio in one layer is set to 1/6, the pilot insertion ratio in another layer is set to 1/12, and the other pilot insertion ratio is set to 1/24. Also, error correction codes having the same error correction code length can be used in the three layers. And the head of an error correction code and the head of an OFDM frame can always be made to correspond.

  In the above example, since the number of error correction code blocks is one, the processing in the second method is substantially the same as that in the first method. The second method is particularly applicable when there are a plurality of error correction code blocks.

Example 3
Next, the error correction code length and the OFDM frame length in the third embodiment will be described. In the third embodiment, as in the second embodiment, the total number of carriers per segment and one OFDM symbol is 216, the AC / TMCC is six, and the pilot insertion ratio is 1/24, 1/12, and 1/6. In this case, an example in which an error correction code length longer than that of the second embodiment is used will be described.

  The condition for matching the head of the error correction code with the head of the OFDM frame is to satisfy the above formula (1) as in the first embodiment, and considering other conditions, the above <a> to < c>.

(Pilot insertion ratio 1/24: Example 3)
Under these conditions, when the pilot insertion ratio is 1/24, the error correction code length L and the number of symbols S _f for matching the head of the error correction code with the head of the OFDM frame are determined as follows. The

For pilot insertion ratio 1/24, 1 segment and because 1OFDM is set to six per the AC / TMCC of the total number 216 pieces of carrier symbols, the number of data carriers per segment and 1OFDM symbol _{N d} is 201 (= 216 −6−216 / 24 = 216−6−9). As in the first embodiment, when M is an even number when the modulation multilevel number is 2 to the Mth power, if the modulation method is QPSK (M = 2) and all of the equations (1) are satisfied, all In the even number M, the formula (1) is satisfied.

Therefore, the mathematical formula (1) is expressed as follows.
[Formula 4]
N _seg × 2 (M) × 201 (N _d ) × 4 × S _f ′ = a × 120 × L ′ (4)
Here, the number of symbols S _f = 4 × S _f ′, and the error correction code length L = 120 × L ′. The parameter a is a positive integer.

The mathematical formula (3) is expressed as follows.
N _seg × 67 × S _f '= a × 5 × L'
By reducing the parameter a, the error correction code length L can be set longer, and by increasing the parameter a, the error correction code length L can be set shorter.

From the foregoing equation (4), the parameter _{S f} 'becomes a multiple of 5, and the symbol number _{S f,} because it is 180 ≦ _{S f} ≦ 264 when the mode 3, GI ratio = 1/8, the parameter _{S f} 'Is 45 ≦ S _f ′ ≦ 66. Therefore, the possible values of the parameter S _f ′ are 45, 50, 55, 60, 65.

FIG. 3 shows the number of symbols per OFDM frame when the number of segments N _seg = 1, M = 2 when the number of modulation levels is 2 to the Mth power, and parameter a = 1/3 in the third embodiment. It is a figure which shows the example of a combination of _Sf and error correction code length L. FIG.

As shown in FIG. 3, examples of combinations of the number of symbols S _f and the error correction code length L are (number of symbols S _f , error correction code length L) = (180, 217,080), (200, 241, 200), (220, 265,320), (240,289,440), etc.

(In case of pilot insertion ratio 1/12 / 1/6: Example 3)
Next, a case will be described in which the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/24 are not changed, and the pilot insertion ratios 1/12/1/6 are used.

In FIG. 3, M = 2 when the number of segments N _seg = 1, the modulation multi-level number is 2 to the Mth power, parameter a = 1/3, the number of symbols S _f = 200, and the error correction code length L = 241,200 The case will be described. By pilot insertion ratio is changed to 1/12 from 1/24, 1 segment and 1OFDM the number of data carriers _{N d} per symbol, from 201 (= 216-6-216 / 24 = 216-6-9) It decreases to 192 (= 216−6−216 / 12 = 216−6−18). Then, the number of bits per OFDM frame decreases from 80,400 × 1 (= 1 × 2 × 201 × 200) to 76,800 × 1 (= 1 × 2 × 192 × 200).

  Here, when the pilot insertion ratio is 1/24, when one error correction code having an error correction code length L = 241,200 is divided into three, the code length per one error correction code is 80,400 (= 241,200 / 3). Therefore, three error correction codes having a code length of 80,400 (= 241,200 / 3) may be stored in three OFDM frames having 80,400 bits.

  On the other hand, when the pilot insertion ratio is 1/12, the error correction code length L = 241,200 cannot be divided by the number of bits per OFDM frame of 76,800, and therefore it is necessary to shorten the error correction coding. Since the number of bits per OFDM frame is 76,800, assuming an OFDM frame with three bits of 76,800, the total is 230,400 (= 76,800 × 3). Therefore, it is necessary to shorten 10,800 (= 241,200−230,400) bits at the time of error correction coding.

In addition, by pilot insertion ratio is changed to 1/6 from 1/24, 1 segment and 1OFDM the number of data carriers _{N d} per symbol, 201 (= 216-6-216 / 24 = 216-6-9 ) To 174 (= 216−6−216 / 6 = 216−6−36). Then, the number of bits per OFDM frame decreases from 80,400 × 1 (= 1 × 2 × 201 × 200) to 69,600 × 1 (= 1 × 2 × 174 × 200).

  Here, when the pilot insertion ratio is 1/6, the error correction code length L = 241,200 is not divisible by 69,600 bits per OFDM frame, so it is necessary to shorten the error correction encoding. Since the number of bits per OFDM frame is 69,600, assuming an OFDM frame with three bits of 69,600, the total is 208,800 (= 69,600 × 3). Therefore, it is necessary to shorten 32,400 (= 241,200−208,800) bits in error correction coding.

  The method in this case (a method of corresponding to the pilot insertion ratios of 1/12 and 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio of 1/24) is described above. There are the same first method and second method.

  As described above, the first method shortens all error correction code blocks at the time of error correction coding. FIG. 8 is a diagram for explaining error correction coding processing and the like in the case of the pilot insertion ratio 1/24 in the third embodiment. FIG. 9 shows a first method in the third embodiment in which the error correction code length L and the OFDM frame length determined when the pilot insertion ratio is 1/24 are not changed and the pilot insertion ratio is 1/12. FIG. The number of OFDM frames per error correction code block is three.

  As shown in FIG. 8, when the pilot insertion ratio is 1/24, the OFDM transmitter performs error correction coding on data D of a predetermined length for one error correction code block at the time of error correction coding. This is performed (step S801). As a result, an error correction code consisting of data D and parity and having an error correction code length of 241,200 bits is generated.

  The OFDM transmitter generates three error correction codes (divided error correction codes) having a code length of 80,400 (= 241,200 / 3) by dividing the error correction code into three. Then, the OFDM transmission apparatus associates one error correction code (divided error correction code) with one OFDM frame, thereby three error correction codes (80,400 (= 241,200 / 3) error correction codes ( Based on the divided error correction code), three OFDM frames with 80,400 bits are constructed (step S802).

  On the other hand, as shown in FIG. 9, when the pilot insertion ratio is 1/12, the OFDM transmitter performs 10,800 (= 241,200-230,400) bits for one error correction code block at the time of error correction coding. Shortening.

  Specifically, the OFDM transmitter inserts 10,800 zero bits at a predetermined position (for example, a rear position) of data D1 having a predetermined length for one error correction code block (step S901). Then, the OFDM transmitter performs error correction coding on the data D1 and zero bits (step S902). As a result, an error correction code having an error correction code length L = 241,200 bits, which includes data D1, zero bits, and parity, is generated.

  The OFDM transmitter deletes the zero bits inserted in step S901 from the error correction code having the error correction code length L = 241,200 bits (step S903). As a result, an error correction code (error correction code after shortening) having a code length of 230,400 bits composed of data D1 and parity is generated.

  An OFDM transmission apparatus divides an error correction code having a code length of 230,400 bits (error correction code after shortening) into three, and thereby an error correction code having a code length of 76,800 (= 230,400 / 3) (after shortening and division). 3 error correction codes) are generated. Then, the OFDM transmitting apparatus associates one error correction code (error correction code after shortening and division) with one OFDM frame, thereby generating three code length 76,800 (= 230,400 / 3) errors. Based on the correction code (error correction code after shortening and division), three OFDM frames having 76,800 bits are formed (step S904).

  Thus, the pilot insertion ratio 1/12 can be accommodated without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/24. That is, even when the pilot insertion ratio is changed from 1/24 to 1/12, the head of the error correction code and the head of the OFDM frame can always be matched. All error correction coding and error correction decoding processes can be made uniform.

  The same applies to the case where the pilot insertion ratio is 1/6 without changing the error correction code length L and the OFDM frame length determined in the case of the pilot insertion ratio 1/24. In the above example, since there is one error correction code block, the processing in the second method is substantially the same as that in the first method. The second method is particularly applicable when there are a plurality of error correction code blocks.

  8 and 9, the OFDM transmitter uses the first OFDM frame (OFDM frame where the head of the error correction code exists) among the three OFDM frames corresponding to one error correction code block. An identifier indicating the presence is set in TMCC, AC, or the like of the first OFDM frame. In this case, the OFDM transmission apparatus may generate a header including the identifier and insert the header into the first bit of the error correction code. Thereby, the OFDM receiver on the receiving side can easily specify the head of the error correction code. Further, the OFDM receiving apparatus performs a process opposite to the process shown in FIGS.

[OFDM transmitter]
Next, an OFDM transmission apparatus according to an embodiment of the present invention will be described. FIG. 10 is a block diagram illustrating a configuration example of an OFDM transmission apparatus according to an embodiment of the present invention. The OFDM transmitter 1 includes an error correction coding unit 10, a carrier modulation unit 11, an OFDM framing unit 12, an IFFT (Inverse Fast Fourier Transform) unit 13, and a table 14. It should be noted that parts not directly related to the present invention, such as components to which GI is added, are omitted.

The error correction coding unit 10 inputs data to be transmitted, and also sets a pilot insertion ratio PR, an error correction code length L (hereinafter referred to as “code length L”), a coding rate CR, and the number of segments. N _seg and M (hereinafter referred to as “modulation multilevel exponent M”) when the modulation multilevel number is 2 to the Mth power are input. Further, the error correction encoding unit 10 includes an error correction code block number BN (hereinafter referred to as “number of blocks”) corresponding to the number of segments N _seg , the modulation multilevel exponent M, the code length L, the encoding rate CR, and the pilot insertion ratio PR. The number of zero insertions ZN for each error correction code block (hereinafter referred to as “block”) is read from the table 14.

  Here, the code length L is set so that the head of the error correction code output from the error correction coding unit 10 and the head of the OFDM frame formed by the OFDM framing unit 12 match. It is a value set by Further, in the table 14, various data set so that the head of the error correction code output from the error correction coding unit 10 and the head of the OFDM frame formed by the OFDM framing unit 12 match, Stored in advance.

  The error correction encoding unit 10 performs error correction encoding processing with a coding rate CR on data of a predetermined length for each block of the number of blocks BN read from the table 14 to generate an error correction code. Then, the error correction encoding unit 10 outputs an error correction code having a predetermined length to the carrier modulation unit 11 for each block.

  Here, the error correction code of a predetermined length is an error correction code having a code length L in the case of a block with a zero insertion number ZN = 0 in the zero insertion number ZN for each block read from the table 14, and the zero insertion number ZN. In the case of ≠ 0 block, it means an error correction code having a code length (L-ZN).

FIG. 11 is a diagram showing a configuration example of the table 14 in the case where the first method described above is used. As described above, the first method shortens all the blocks at the time of error correction coding. This table 14 is composed of various data such as the number of segments N _seg , the modulation multilevel index M, the code length L, the coding rate CR, the pilot insertion ratio PR, the number of blocks BN, and the number of zero insertions ZN for each block.

When the first method is used, for example, the table 14 includes (number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, zero for each block. Insertion number ZN) = (12,2,76,800, CR1,1 / 12,24, <0, ..., 0>), (12,2,76,800, CR1,1 / 6,24, <7,200, ... , 7,200>) and the like are stored. (12, 2, 76, 800, CR 1, 1/12, 24, <0,..., 0>) is data corresponding to FIG. 5, and (12, 2, 76, 800, CR 1, 1/6, 24, <7,200,..., 7,200>) is data corresponding to FIG.

FIG. 12 is a diagram illustrating a configuration example of the table 14 in the case where the second method described above is used. As described above, the second method shortens some blocks at the time of error correction coding. This table 14 is similar to FIG. 11 in that the number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, block number BN, and zero insertion number ZN for each block Consists of data.

When the second method is used, for example, the table 14 includes (number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, zero for each block. Insertion number ZN) = (12,2,76,800, CR1,1 / 12,24, <0, ..., 0>), (12,2,76,800, CR1,1 / 6,22, <0, ...) , 0, 19,200>) and the like are stored. (12, 2, 76, 800, CR1, 1/6, 22, <0,..., 0, 19,200>) is data corresponding to FIG.

Returning to FIG. 10, the case where the first method is used in the first embodiment will be described. The error correction coding unit 10 has a pilot insertion ratio PR = 1/12, a code length L = 76,800, a coding rate CR = CR1, a segment number N _seg = 12, and a modulation multi-valued index M = 2. input. Then, from the table 14 shown in FIG. 11, the error correction coding unit 10 determines the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1, and the pilot insertion. Corresponding to the ratio PR = _1/12 (number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = ( 12, 2, 76, 800, CR1, 1/12, 24, <0,..., 0>).

  The error correction encoding unit 10 determines that the zero insertion number ZN = 0 of all the blocks, and performs a normal encoding process that does not perform shortening, that is, the process of step S501 shown in FIG.

  Specifically, the error correction coding unit 10 performs error correction coding with the coding rate CR1 on the data D having a predetermined length for each block of the number of blocks BN = 24, and performs error correction with a code length L = 76,800 bits. Generate a code. Then, the error correction encoding unit 10 outputs an error correction code having a code length L = 76,800 bits to the carrier modulation unit 11 for each block.

When the pilot insertion ratio PR is changed from 1/12 to 1/6, the error correction encoding unit 10 performs the changed pilot insertion ratio PR = 1/6, the code length L = 76,800, and the encoding rate CR. = CR1, the number of segments N _seg = 12, and the modulation multilevel index M = 2. Then, from the table 14 shown in FIG. 11, the error correction coding unit 10 determines the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1, and the pilot insertion. Corresponding to the ratio PR = _1/6 (number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = ( 12, 2, 76,800, CR1, 1/6, 24, <7,200,..., 7,200>).

  The error correction encoding unit 10 determines that the zero insertion number ZN ≠ 0 of all the blocks, and performs an encoding process with shortening of the zero insertion number 7,200 bits, that is, steps S601 to S603 shown in FIG. Process.

  Specifically, the error correction encoding unit 10 inserts zero insertion number ZN = 7,200 bits at a predetermined position (for example, a rear position) of data D ′ having a predetermined length for each block having a block number BN = 24. To do. Then, the error correction coding unit 10 performs error correction coding of the coding rate CR1 on the data D ′ and zero bits for each block, and has an error of code length L = 76,800 bits composed of the data D ′, zero bits, and parity. A correction code is generated.

  The error correction coding unit 10 deletes the zero insertion number ZN = 7,200 bits from the error correction code of code length L = 76,800 bits for each block, and corrects the error of 69,600 bits of code length consisting of data D ′ and parity A code (error correction code after shortening) is generated. Then, the error correction encoding unit 10 outputs an error correction code having a code length of 69,600 bits (error correction code after shortening) to the carrier modulation unit 11 for each block.

Next, the case where the second method is used in the first embodiment will be described. When the pilot insertion ratio PR is changed from 1/12 to 1/6, the error correction encoder 10 performs the changed pilot insertion ratio PR = 1/6, the code length L = 76,800, and the coding rate CR = CR1. , The number of segments N _seg = 12 and the modulation multivalued index M = 2. Then, the error correction coding unit 10 determines from the table 14 shown in FIG. 12 that the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1 and the pilot insertion. Corresponding to the ratio PR = _1/6 (number of segments N _seg , modulation multivalued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = ( 12, 2, 76,800, CR1, 1/6, 22, <0,..., 0, 19,200>).

  The error correction encoding unit 10 determines that the zero insertion number ZN = 0 of the first to 21st blocks out of the block number BN = 22 and the zero insertion number ZN ≠ 0 of the 22nd block. The error correction encoding unit 10 performs a normal encoding process that does not perform shortening for the first to 21st blocks, that is, the process of step S701 illustrated in FIG. Further, the error correction coding unit 10 performs coding processing with shortening of the number of zero insertions of 19,200 bits, that is, the processing of step S702, step S703, and step S704 illustrated in FIG.

  Specifically, the error correction coding unit 10 performs error correction coding with a coding rate CR1 on the data D having a predetermined length for each of the first to 21st blocks, and performs error correction with a code length L = 76,800 bits. Generate a code. Then, the error correction encoding unit 10 outputs an error correction code having a code length L = 76,800 bits to the carrier modulation unit 11 for each of the first to 21st blocks.

  Further, the error correction encoding unit 10 inserts zero bits of zero insertion number ZN = 19,200 bits at a predetermined position (for example, a rear position) of data D ″ having a predetermined length for the 22nd block. The encoding unit 10 performs error correction encoding of the coding rate CR1 on the data D ″, zero bits, and the error correction code of the code length L = 76,800 bits including the data D ″, zero bits, and parity for the 22nd block. Generate.

  For the 22nd block, the error correction coding unit 10 deletes the zero insertion number ZN = 19,200 bits from the error correction code having the code length L = 76,800 bits, and the code length 57,600 bits including the data D ″ and the parity. An error correction code (an error correction code after shortening) is generated, and the error correction encoding unit 10 generates an error correction code (an error correction code after shortening) having a code length of 57,600 bits for the 22nd block. Output to the carrier modulation unit 11.

Returning to FIG. 10, the carrier modulation unit 11 inputs an error correction code from the error correction encoding unit 10 and also inputs a preset modulation multilevel exponent M. Then, the carrier modulation unit 11 performs modulation multilevel exponent M carrier modulation on the error correction code by a predetermined modulation method (modulation multilevel number ^2M carrier modulation), and the IQ axis constellation arrangement is performed. To generate a modulated signal. The carrier modulation unit 11 outputs the modulated signal to the OFDM framing unit 12.

The OFDM framing unit 12 receives a modulation signal from the carrier modulation unit 11 and also includes a TMCC including a pilot insertion ratio PR, a code length L, a coding rate CR, a segment number N _seg , a modulation multi-value index M, and the like. Input a control signal.

Here, a TMCC generation unit (not shown) inputs a pilot insertion ratio PR, a code length L, a coding rate CR, a segment number N _seg , a modulation multi-valued index M, etc., and generates a TMCC including these data, The TMCC is output to the OFDM framing unit 12.

  The OFDM framing unit 12 arranges a modulation signal and a control signal such as TMCC at a predetermined frequency position to form an OFDM frame. Then, the OFDM framing unit 12 outputs the OFDM signal to the IFFT unit 13.

The configuration content such as the size of the OFDM frame is set based on the number of data carriers N _d and the number of symbols S _f set in advance. The number of data carriers N _d may also be set based on the pilot insertion ratio PR.

  Specifically, in the example of FIG. 5, the OFDM framing unit 12 stores 76,800 × 24 = 1,843,200 bits of modulation signals corresponding to the error correction code having the number of blocks BN = 24 in the OFDM frame. One OFDM frame including an error correction code is configured. In the case of the example of FIG. 6, the OFDM framing unit 12 stores 69,600 × 24 = 1,670,400 bits of error correction code by storing a modulation signal or the like corresponding to the error correction code of the number of blocks BN = 24 in the OFDM frame. One OFDM frame including is constructed. In the case of the example in FIG. 7, the OFDM framing unit 12 stores 76,800 × 21 + 57,600 × 1 = 1,670,400 bits by storing a modulation signal or the like corresponding to the error correction code having the number of blocks BN = 22 in the OFDM frame. One OFDM frame including a plurality of error correction codes is configured.

  The IFFT unit 13 receives the OFDM signal from the OFDM framing unit 12, performs IFFT on the OFDM signal, and converts the signal on the frequency axis to the signal on the time axis. The OFDM signal converted by the IFFT unit 13 is subjected to a predetermined transmission process and transmitted from the transmission antenna.

  As described above, according to the OFDM transmitter 1 of the embodiment of the present invention, the start of the error correction code output from the error correction encoding unit 10 and the start of the OFDM frame configured by the OFDM framing unit 12 Are processed using a pilot insertion ratio PR, a code length L, a coding rate CR, a block number BN, a zero insertion number ZN, a modulation multi-value index M, and the like set in advance.

Specifically, the error correction coding unit 10 includes the number of segments N _seg , the modulation multi-valued index M, the code length L, the coding rate CR, and the number of blocks BN corresponding to the pilot insertion ratio PR and zero insertion for each block. The number ZN is read from the table 14. Then, the error correction coding unit 10 performs normal error correction coding or error correction coding with shortening for each block, and generates an error correction code. The carrier modulation unit 11 performs modulation multi-level exponent M carrier modulation (carrier modulation with a modulation multi-level number of 2 ^M ) on the error correction code by a predetermined modulation method to generate a modulation signal. The OFDM framing unit 12 transmits a modulation signal and a control signal such as a TMCC including a pilot insertion ratio PR, a code length L, a coding rate CR, a number of segments N _seg , a modulation multi-valued index M, and the like at predetermined frequency positions To configure an OFDM frame.

  Thereby, even if the pilot insertion ratio PR is changed, the head of the error correction code and the head of the OFDM frame can always be matched without changing the code length L and the OFDM frame length. Therefore, the OFDM receiving apparatus 2 to be described later does not require the process of matching these heads and can easily reproduce the synchronization signal, so that the synchronization performance can be improved.

  Further, the OFDM transmitter 1 does not need to transmit data for matching these heads. Therefore, the OFDM transmitter 1 does not need an extra function, and the OFDM receiver 2 does not need a corresponding decoding function. That is, synchronization performance and transmission efficiency similar to those of conventional terrestrial digital broadcasting (ISDB-T) can be realized, and functions can be reduced on the transmission side and reception side.

  Note that the processes of the error correction encoding unit 10 to the IFFT unit 13 of the OFDM transmitter 1 shown in FIG. 10 are the above-described second embodiment and the third embodiment (an example using a longer code length than the second embodiment). Also applies.

  In the case of the third embodiment, one error correction code corresponds to a plurality (three) of OFDM frames. Therefore, the OFDM framing unit 12 of the OFDM transmitter 1 divides the modulation signal sequence corresponding to one error correction code into three, and for each of the three modulation signal sequences, the modulation signal, and A control signal such as TMCC is arranged at a predetermined frequency position in the OFDM frame. Then, the OFDM framing unit 12 configures three OFDM frames as shown in step S802 shown in FIG. 8 and step S904 shown in FIG.

Further, the error correction coding unit 10 of the OFDM transmitter 1 has the segment number N _seg changed to m times (m is an integer of 2 or more), and the segment number N _seg after the change is not stored in the table 14 The number of blocks BN that has been read from the table 14 (the number of blocks BN corresponding to the number of segments N _seg before being changed to m times) may be multiplied by m. The error correction encoding unit 10 performs error correction encoding on each block of the block number BN multiplied by m. As the number of zero insertions in this case, the number of zero insertions read from the table 14 is used for each corresponding block. The same applies when the modulation multi-value index M is changed to m times.

Accordingly, even when only the segment number N _seg is changed, only when the modulation multi-value index M is changed, or when the segment number N _seg and the modulation multi-value index M are changed, Without changing the code length L and the OFDM frame length, the head of the error correction code and the head of the OFDM frame can always be matched, and the same effect as described above can be obtained.

[OFDM receiver]
Next, an OFDM receiving apparatus according to an embodiment of the present invention will be described. FIG. 13 is a block diagram illustrating a configuration example of an OFDM receiver according to an embodiment of the present invention. The OFDM receiver 2 includes an effective symbol period extraction unit 20, an FFT (Fast Fourier Transform) unit 21, an equalization unit 22, a TMCC extraction unit 23, a carrier demodulation unit 24, an error correction decoding unit 25, and a table 26. It has.

In FIG. 13, portions not directly related to the present invention are omitted. Moreover, the configuration contents such as the size of the OFDM frame, and is set based on a preset data carrier number N _d and the number of symbols S _f or the like. The number of data carriers N _d may also be set based on the pilot insertion ratio PR, which is extracted by the TMCC extraction unit 23 to be described later.

  The OFDM receiver 2 receives an OFDM signal via a reception antenna (not shown) and performs a predetermined reception process. The effective symbol period extraction unit 20 receives the OFDM signal subjected to the reception process, extracts the effective symbol period by the correlation process of the signal of the GI period in one OFDM symbol period, and converts the OFDM signal of the effective symbol period into the FFT unit To 21.

  The FFT unit 21 receives the OFDM signal of the effective symbol period from the effective symbol period extraction unit 20, performs FFT on the OFDM signal, converts the signal on the time axis to the signal on the frequency axis, and converts the signal on the frequency axis The data is output to the equalization unit 22 and the TMCC extraction unit 23.

  The equalization unit 22 receives a signal on the frequency axis from the FFT unit 21, extracts a SP at a predetermined position from the signal on the frequency axis, calculates a transmission line response, and equalizes the input signal on the frequency axis To do. Then, the equalization unit 22 outputs the equalized signal (the signal corresponding to the modulation signal output by the carrier modulation unit 11 illustrated in FIG. 10) to the carrier demodulation unit 24.

The TMCC extraction unit 23 receives a signal on the frequency axis from the FFT unit 21, extracts a TMCC at a predetermined position from the signal on the frequency axis, and extracts a pilot insertion ratio PR, a code length L, a coding rate CR, a segment from the TMCC The number N _seg , the modulation multilevel index M, and the like are extracted. Then, the TMCC extraction unit 23 outputs the modulation multilevel index M to the carrier demodulation unit 24, and obtains the pilot insertion ratio PR, the code length L, the coding rate CR, the number of segments N _seg , the modulation multilevel index M, etc. The data is output to the error correction decoding unit 25.

The carrier demodulating unit 24 receives the equalized signal from the equalizing unit 22 and also receives the modulation multilevel exponent M from the TMCC extracting unit 23. Then, the carrier demodulator 24 modulates the multi-valued signal with the same predetermined modulation method as that of the carrier modulator 11 shown in FIG. Exponential M carrier demodulation (modulation multilevel number 2 ^M carrier demodulation) is performed. The carrier demodulation unit 24 outputs the demodulated signal after carrier demodulation (a signal corresponding to the error correction code output by the error correction encoding unit 10 shown in FIG. 10) to the error correction decoding unit 25.

The error correction decoding unit 25 receives a demodulated signal (a signal corresponding to an error correction code) from the carrier demodulation unit 24, and also receives a pilot insertion ratio PR, a code length L, a coding rate CR, and a segment number N from the TMCC extraction unit 23. _seg , modulation multi-value index M, etc. are input. The error correction decoding unit 25 stores the number of segments N _seg , the modulation multi-valued index M, the code length L, the coding rate CR, and the number of zero insertions ZN for each block corresponding to the coding rate CR and the pilot insertion ratio PR. Read from.

  Here, in the table 26, the same various data as the table 14 shown in FIG. 10 are stored in advance. The OFDM transmitter 1 reads various data from the table 14 and transmits it as an OFDM signal to the OFDM receiver 2. The OFDM receiver 2 receives the OFDM signal from the OFDM transmitter 1, and stores the various data in the table 26. You may make it store in.

  The error correction decoding unit 25 performs error correction decoding processing of the coding rate CR on the demodulated signal (signal corresponding to the error correction code) for each block as many as the number of blocks read from the table 26, and converts the original data into Restore and output.

A case where the first method is used in the first embodiment will be described. The error correction decoding unit 25 obtains the pilot insertion ratio PR = 1/12, the code length L = 76,800, the coding rate CR = CR1, the number of segments N _seg = 12, and the modulation multilevel index M = 2 from the TMCC extraction unit 23. input. Then, the error correction decoding unit 25 determines from the table 26 that the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1, and the pilot insertion ratio PR = 1/12. (Number of segments N _seg , modulation multi-valued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = (12, 2, 76,800, CR1, 1/12, 24, <0,..., 0>) are read out. The table 26 stores the same various data as the table 14 shown in FIG.

  The error correction decoding unit 25 determines that the zero insertion number ZN = 0 of all the blocks, and performs normal error correction decoding without extension (processing corresponding to shortening), that is, step S501 shown in FIG. The reverse process is performed.

  Specifically, the error correction decoding unit 25 divides a signal (code length L × number of blocks = 76,800 × 24 = 1,843,200-bit signal) corresponding to one OFDM frame into the number of blocks BN = 24 and divides the signal. The signal is a signal for each block. The error correction decoding unit 25 performs error correction decoding with a coding rate CR1 on a signal having a code length L = 76,800 bits (an equalized signal, that is, a signal corresponding to the error correction code) for each block having the number of blocks BN = 24. To generate original data D having a predetermined length. A signal having a code length L = 76,800 bits is composed of data D and parity as shown in FIG. Then, the error correction decoding unit 25 outputs the data D for each block as the original data.

When the pilot insertion ratio PR is changed from 1/12 to 1/6, the error correction decoding unit 25 sends the pilot insertion ratio PR = 1/6, the code length L = 76,800 from the TMCC extraction unit 23, and the coding rate. Enter CR = CR1, the number of segments N _seg = 12, and the modulation multivalued index M = 2. Then, the error correction decoding unit 25 determines from the table 26 that the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1, and the pilot insertion ratio PR = 1/6. (Number of segments N _seg , modulation multi-valued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = (12, 2, 76,800, CR1, 1/6, 24, <7,200,..., 7,200>) are read out.

  The error correction decoding unit 25 determines that the zero insertion number ZN ≠ 0 of all the blocks, and performs error correction decoding with extension of the zero insertion number of 7,200 bits, that is, the reverse of steps S601 to S603 shown in FIG. Perform the process.

  Specifically, the error correction decoding unit 25 is a signal corresponding to one OFDM frame ((code length L−zero insertion number ZN) × number of blocks = (76,800−7,200) × 24 = 69,600 × 24 = 1,670,400 bits. Are divided into the number of blocks BN = 24, and the divided signals are used as signals for each block. The error correction decoding unit 25 subtracts the zero insertion number ZN = 7,200 bits from the code length L = 76,800 bits for each block having the block number BN = 24 to obtain a code length 69,600 (= 76,800-7,200). Then, the error correction decoding unit 25, for each block, has a predetermined position (for example, a position between the data D ′ and the parity) of a signal having a code length of 69,600 bits (an equalized signal, that is, a signal corresponding to the error correction code). ), A zero bit number ZN = 7,200 bits are inserted to generate a signal with a code length L = 76,800 bits consisting of data D ′, zero bits, and parity. This is the reverse process of step S603 shown in FIG.

  The error correction decoding unit 25 performs error correction decoding at a coding rate CR1 on a signal having a code length L = 76,800 bits for each block, and generates a signal composed of data D ′ and zero bits. This is the reverse process of step S602 shown in FIG. Then, the error correction decoding unit 25 deletes the zero bits from the signal composed of the data D ′ and the zero bits for each block, and generates the original data D ′. This is the reverse process of step S601 shown in FIG. The error correction decoding unit 25 outputs the data D ′ for each block as the original data.

Next, the case where the second method is used in the first embodiment will be described. When the pilot insertion ratio PR is changed from 1/12 to 1/6, the error correction decoding unit 25 transmits the pilot insertion ratio PR = 1/6, the code length L = 76,800, the coding rate CR = from the TMCC extracting unit 23. Enter CR1, the number of segments N _seg = 12, and the modulation multilevel index M = 2. Then, the error correction decoding unit 25 determines from the table 26 that the number of segments N _seg = 12, the modulation multivalued index M = 2, the code length L = 76,800, the coding rate CR = CR1, and the pilot insertion ratio PR = 1/6. (Number of segments N _seg , modulation multi-valued index M, code length L, coding rate CR, pilot insertion ratio PR, number of blocks BN, number of zero insertions ZN per block) = (12, 2, 76,800, CR1, 1/6, 22, <0,..., 0, 19,200>) are read out. The table 26 stores various types of data that are the same as the table 14 shown in FIG.

  The error correction decoding unit 25 determines that the zero insertion number ZN = 0 of the first to 21st blocks out of the block number BN = 22 and the zero insertion number ZN ≠ 0 of the 22nd block. The error correction decoding unit 25 performs normal error correction decoding without extension on the 1st to 21st blocks, that is, reverse processing of step S701 shown in FIG. Further, the error correction decoding unit 25 performs error correction decoding with extension of the number of zero insertions of 19,200 bits on the 22nd block, that is, reverse processing of step S702, step S703 and step S704 shown in FIG.

  Specifically, the error correction decoding unit 25 converts a signal corresponding to one OFDM frame (a signal of 1,670,400 bits) into a signal of 21 code lengths L = 76,800 bits in the first to 21st blocks, and This is divided into signals of one code length 57,600 (= code length L-zero insertion number = 76,800-19,200) bits in the 22nd block.

  The error correction decoding unit 25 performs error correction decoding with a coding rate CR1 on a signal having a code length L = 76,800 bits (an equalized signal, ie, a signal corresponding to an error correction code) for each of the first to 21st blocks. To generate original data D having a predetermined length. A signal having a code length L = 76,800 bits is composed of data D and parity as shown in FIG. Then, the error correction decoding unit 25 outputs the data D for each block as the original data.

  Further, the error correction decoding unit 25 subtracts the zero insertion number ZN = 19,200 bits from the code length L = 76,800 bits to obtain the code length 57,600 (= 76,800-19,200) for the 22nd block. Then, the error correction decoding unit 25, for the 22nd block, between a predetermined position (for example, data D ″ and parity) of a signal having a code length of 57,600 bits (the signal after equalization, ie, the signal corresponding to the error correction code) Of zero insertion number ZN = 19,200 bits is inserted at a position), a signal having a code length L = 76,800 bits composed of data D ″, zero bits, and parity is generated. This is the reverse process of step S704 shown in FIG.

  The error correction decoding unit 25 performs error correction decoding of the coding rate CR1 on the signal of the code length L = 76,800 bits for the 22nd block, and generates a signal composed of data D ″ and zero bits. The error correction decoding unit 25 deletes the zero bit from the signal composed of the data D ″ and the zero bit for the 22nd block, and generates the original data D ″. This is the reverse process of step S702 shown in Fig. 7. The error correction decoding unit 25 outputs data D "as original data for the 22nd block.

  As described above, according to the OFDM receiver 2 of the embodiment of the present invention, the data received from the OFDM transmitter 1 and various data set in advance so that the head of the error correction code matches the head of the OFDM frame. Processing is performed using a pilot insertion ratio PR, a code length L, a coding rate CR, a block number BN, a zero insertion number ZN, a modulation multilevel exponent M, and the like.

Specifically, the TMCC extracting unit 23 extracts a TMCC at a predetermined position from the signal on the frequency axis in the received OFDM signal, and from the TMCC, the pilot insertion ratio PR, the code length L, the coding rate CR, and the number of segments N _seg Then, the modulation multi-value index M and the like are extracted. The carrier demodulating unit 24 performs carrier demodulation (modulation multilevel modulation) of the modulation multilevel index M on the equalized signal (signal on the constellation arrangement on the IQ axis) by the same predetermined modulation method as that on the transmission side. 2 ^M carrier demodulation).

The error correction decoding unit 25 transmits the number of segments N _seg , the modulation multi-valued index M, the code length L, the coding rate CR, and the number of zero insertions ZN for each block corresponding to the coding rate CR and the pilot insertion ratio PR to the transmission side. Are read from the table 26 in which the same data as the table 14 is stored. Then, for each block, the error correction decoding unit 25 performs normal error correction decoding when the zero insertion number ZN = 0, and performs error correction decoding with extension when the zero insertion number ZN ≠ 0, Restore the data.

  Thereby, even if the pilot insertion ratio PR is changed, the head of the error correction code and the head of the OFDM frame always coincide with each other without changing the code length L and the OFDM frame length. Therefore, in the OFDM receiving apparatus 2, the process of matching these heads becomes unnecessary, and the synchronization signal can be easily reproduced, so that the synchronization performance can be improved. Further, the OFDM transmitter 1 does not need to transmit data for matching these heads. Therefore, the OFDM transmitter 1 does not need an extra function, and the OFDM receiver 2 also does not need a corresponding decoding function. That is, synchronization performance and transmission efficiency similar to those of conventional terrestrial digital broadcasting (ISDB-T) can be realized, and functions can be reduced on the transmission side and reception side.

  The processing from the effective symbol period extraction unit 20 to the error correction decoding unit 25 of the OFDM receiver 2 shown in FIG. 13 is also applied to the above-described second embodiment and the above-described third embodiment.

  In the case of the third embodiment, one error correction code corresponds to a plurality (three) of OFDM frames. Accordingly, the error correction decoding unit 25 of the OFDM receiving apparatus 2 combines the signals corresponding to the three OFDM frames to generate one signal. This is the reverse process of step S802 shown in FIG. 8 and the reverse process of step S904 shown in FIG. Then, the error correction decoding unit 25 performs normal error correction decoding in the case of FIG. 8, and performs error correction decoding with extension in the case of FIG.

When the error correction decoding unit 25 of the OFDM receiver 2 determines that the segment number N _seg input from the TMCC extraction unit 23 has been changed to m times (m is an integer of 2 or more), the segment number N after the change _{When seg} is not stored in the table 26, the number of blocks BN read from the table 26 (the number of blocks BN corresponding to the number of segments N _seg before being changed to m times) may be multiplied by m. . The error correction decoding unit 25 performs error correction decoding on each block of the block number BN multiplied by m. In this case, the number of zero insertions read from the table 26 is used for the corresponding block. The same applies when it is determined that the modulation multivalued index M has been changed to m times.

Accordingly, even when only the segment number N _seg is changed, only when the modulation multi-value index M is changed, or when the segment number N _seg and the modulation multi-value index M are changed, Without changing the code length L and the OFDM frame length, the head of the error correction code and the head of the OFDM frame can always be matched, and the same effect as described above can be obtained.

  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. For example, in FIGS. 6, 7, and 9, the OFDM transmitter 1 performs error correction coding by inserting zero bits after data when performing error correction coding with shortening. The zero bit is deleted between the end of the data and the parity. In addition, the OFDM receiver 2 performs error correction decoding by inserting zero bits between the back of the data and the parity, and deletes the zero bits from the back of the data. The present invention does not limit the position of the zero bit to be inserted and deleted after the data. For example, the position of the zero bit may be set before the data, or when the data is divided into a plurality of pieces, it may be between the divided data.

  Further, in FIG. 6, when the pilot insertion ratio is changed from 1/12 to 1/6, the OFDM transmitter 1 performs error correction coding with 7200 bit shortening for each of the 24 blocks, An error correction code having a code length of 69,600 bits is generated. Thereby, an OFDM frame of 69,600 × 24 = 1,670,400 bits corresponding to the pilot insertion ratio 1/6 is formed. When the pilot insertion ratio is 1/6, the number of bits per OFDM frame is 1,670,400, which is a value divisible by 24. For this reason, the number of blocks is the same as in the case where the pilot insertion ratio shown in FIG. 5 is 1/12.

  On the other hand, depending on the code length L, the number of bits per OFDM frame when the pilot insertion ratio is 1/6 may not be divisible by a positive integer. In this case, different zero insertion numbers are used between blocks. That is, the table 14 may store a different number of zero insertions for each block.

  Further, in the above embodiment, the error correction coding unit 10 of the OFDM transmitter 1 performs normal error correction coding when the pilot insertion ratio is 1/12, and changes the pilot insertion ratio to 1/6, which is higher than this. In such a case, error correction encoding with shortening is performed. On the other hand, the error correction coding unit 10 performs normal error correction coding when the pilot insertion ratio is 1/12, and is shortened when the pilot insertion ratio is changed to a lower pilot insertion ratio 1/24. Error correction coding may be performed.

  For example, when the pilot insertion ratio is PR1, PR2, PR3 (PR1 <PR2 <PR3), and the error correction coding unit 10 of the OFDM transmitter 1 has the lowest pilot insertion ratio PR1, this is used as a standard error correction. Encoding is performed. Then, when the pilot insertion ratio is changed from PR1 to PR2 and PR3 to a high ratio, error correction encoding section 10 performs error correction encoding with shortening.

  The error correction coding unit 10 performs normal error correction coding on the basis of the highest pilot insertion ratio PR3, and shortens it when the pilot insertion ratio is changed from PR3 to PR2 and PR1 to a lower ratio. Error correction coding with encoding is performed.

  In the case of the pilot insertion ratio PR2, the error correction coding unit 10 performs normal error correction coding on the basis of this, and when the pilot insertion ratio is changed from PR2 to PR1 and PR3, the error correction code with shortening is performed. You may make it perform.

  In addition, in the tables 14 and 26, information (modulation multi-value information) regarding the modulation multi-value such as the modulation multi-value number may be stored instead of the modulation multi-value index M. The modulation multilevel information has a relationship in which, for example, the modulation multilevel number is uniquely determined corresponding to the modulation multilevel index M. Therefore, the error correction encoding unit 10 of the OFDM transmission apparatus 1 may convert other modulation multilevel information such as the modulation multilevel number into a modulation multilevel index M and perform the above-described processing. The processing may be performed using other modulation multilevel information such as the modulation multilevel number. The same applies to the carrier modulation unit 11 and the OFDM framing unit 12. The same applies to the TMCC extraction unit 23, the carrier demodulation unit 24, and the error correction decoding unit 25 of the OFDM receiver 2.

DESCRIPTION OF SYMBOLS 1 OFDM transmitter 2 OFDM receiver 10 Error correction encoding part 11 Carrier modulation part 12 OFDM frame conversion part 13 IFFT part 14, 26 Table 20 Effective symbol period extraction part 21 FFT part 22 Equalization part 23 TMCC extraction part 24 Carrier demodulation 25 Error correction decoding unit

Claims (9)

In an OFDM transmission apparatus that performs error correction encoding on data to be transmitted, carrier-modulates the error correction code, converts the modulated signal into an OFDM frame, IFFTs the OFDM frame signal, and transmits the OFDM signal.
The error correction code length is set to a positive integer ratio so that the relationship between the error correction code length and the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame is a positive integer ratio. Preset,
For each block of the number of blocks corresponding to the pilot insertion ratio, by performing error correction coding on predetermined data, normal error correction coding for generating the error correction code of the error correction code length is performed, or Error correction coding is performed by inserting zero bits of a predetermined number of zero insertions into predetermined data to generate a code of the error correction code length, and deleting the zero bits of the predetermined number of zero insertions from the code An error correction encoding unit for performing error correction encoding with shortening to generate the error correction code;
A carrier modulation unit that performs carrier modulation in accordance with preset modulation multilevel information and generates the modulation signal for the error correction code generated by the error correction coding unit;
An OFDM framing unit that arranges the modulation signal generated by the carrier modulation unit at a predetermined position and constitutes the OFDM frame;
The error correction encoder is
In the case of a preset pilot insertion ratio, the normal error correction coding is performed for all blocks,
When the preset pilot insertion ratio is changed, error correction coding with the shortening is performed for all the blocks, or the shortening is performed for some of the blocks. An OFDM transmitter characterized by performing error correction coding with encoding and performing the normal error correction coding for the remaining blocks. In an OFDM transmission apparatus that performs error correction encoding on data to be transmitted, carrier-modulates the error correction code, converts the modulated signal into an OFDM frame, IFFTs the OFDM frame signal, and transmits the OFDM signal.
Corresponding to the number of segments, modulation multilevel information, error correction code length, coding rate and pilot insertion ratio, a table storing the number of blocks and the number of zero insertions for each block;
For each block of the number of blocks corresponding to a preset number of segments, modulation multilevel information, error correction code length, coding rate and pilot insertion ratio, perform error correction coding processing on the transmission target data, An error correction encoding unit for generating the error correction code;
A carrier modulation unit that performs carrier modulation in accordance with preset modulation multilevel information and generates the modulation signal for the error correction code generated by the error correction coding unit;
An OFDM framing unit that arranges the modulation signal generated by the carrier modulation unit at a predetermined position and constitutes the OFDM frame;
The error correction encoder is
From the table, read the number of blocks corresponding to the preset number of segments, modulation multilevel information, error correction code length, coding rate and pilot insertion ratio, and the number of zero insertions for each block,
Perform error correction coding on predetermined data for the block with zero insertion number of 0, and generate the error correction code of a preset error correction code length,
For the block whose number of zero insertions is not 0, the first data is generated by inserting zero bits of the number of zero insertions into predetermined data, error correction coding is performed on the first data, and the preset error An OFDM transmission apparatus, wherein a first code having a correction code length is generated, and the error correction code is generated by deleting zero bits of the number of zero insertions from the first code. The OFDM transmitter according to claim 2,
When the number of segments is N _seg and the modulation multilevel information is the modulation multilevel number, the index when the modulation multilevel number is expressed as a power of 2 is M, and the number of data carriers per symbol of the OFDM frame Is N _d , the number of symbols of the OFDM frame is S _f , the error correction code length is L, and a predetermined positive integer or a number of positive integers is a,
Formula: N _seg × M × N _d × S _f = a × L
An OFDM transmitter characterized by satisfying: The OFDM transmitter according to claim 2,
As the preset error correction code length, a positive integer multiple or a positive integer fraction with respect to the number of bits of data to be transmitted corresponding to all the modulation signals arranged in the OFDM frame Value of
In the case of the preset pilot insertion ratio,
The error correction encoder is
For all the blocks of the number of blocks, perform error correction encoding on the predetermined data, and generate the error correction code of the preset error correction code length,
When the preset pilot insertion ratio is changed,
As the number of zero insertions for each block, a number according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame is used,
The error correction encoder is
For all the blocks of the number of blocks, the first data is generated by inserting zero bits of the number of zero insertions into the predetermined data, error correction coding is performed on the first data, and the preset An OFDM transmitting apparatus, wherein the first code having an error correction code length is generated, and the error correction code is generated by deleting the zero bits of the number of zero insertions from the first code. The OFDM transmitter according to claim 2,
As the preset error correction code length, a positive integer multiple or a positive integer fraction with respect to the number of bits of data to be transmitted corresponding to all the modulation signals arranged in the OFDM frame Value of
In the case of the preset pilot insertion ratio,
The error correction encoder is
For all the blocks of the number of blocks, perform error correction encoding on the predetermined data, and generate the error correction code of the preset error correction code length,
When the preset pilot insertion ratio is changed,
As the number of zero insertions for each block, a number according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame is used,
The error correction encoder is
Of all the blocks of the number of blocks, the first data is generated by inserting zero bits of the number of zero insertions into the predetermined data for some of the blocks where the number of zero insertions is not 0, and the first data Perform error correction coding on the data, generate the first code having the preset error correction code length, and delete the zero bits of the zero insertion number from the first code to generate the error correction code And
Among all the blocks of the number of blocks, error correction coding is performed on the predetermined data for other blocks where the zero insertion number is not 0, and the error correction code having the preset error correction code length is generated. An OFDM transmitter characterized by that. An OFDM signal is received from the OFDM transmitter according to claim 1, the OFDM signal is subjected to FFT, the signal after FFT is equalized, the equalized signal is carrier demodulated, and the signal after carrier demodulation is subjected to error correction decoding. In the OFDM receiver that restores the original data,
A carrier demodulation unit that performs carrier demodulation in accordance with the same modulation multilevel information as the OFDM transmitter, and generates a demodulated signal for the equalized signal,
Whether normal error correction decoding is performed to restore the original data by performing error correction decoding on the demodulated signal having the same error correction code length as that of the OFDM transmitter for each block corresponding to the pilot insertion ratio. Or subtracting a predetermined number of zero insertions from the same error correction code length as that of the OFDM transmitter, and inserting the zero bits of the predetermined number of zero insertions into the demodulated signal having the length of the subtraction result, A first demodulated signal having the same error correction code length is generated, error correction decoding is performed on the first demodulated signal, and zero bits of the predetermined number of zero insertions are deleted from the signal after error correction decoding. An error correction decoding unit that performs error correction decoding with extension to restore
The error correction decoding unit
In the case of the same pilot insertion ratio as that of the OFDM transmitter, the normal error correction decoding is performed for all blocks,
When the same pilot insertion ratio as that of the OFDM transmitter is changed, error correction decoding with the extension is performed for all the blocks, or some of the blocks An OFDM receiving apparatus, wherein error correction decoding with extension is performed on the remaining blocks, and the normal error correction decoding is performed on the remaining blocks. An OFDM signal is received from the OFDM transmitter according to claim 2, the OFDM signal is subjected to FFT, the signal after FFT is equalized, the equalized signal is carrier-demodulated, and the signal after carrier demodulation is error-correction decoded Then, in the OFDM receiver that restores the original data,
Corresponding to the number of segments, modulation multilevel information, error correction code length, coding rate and pilot insertion ratio, a table storing the number of blocks and the number of zero insertions for each block;
A carrier demodulation unit that performs carrier demodulation in accordance with the same modulation multilevel information as the OFDM transmitter, and generates a demodulated signal for the equalized signal,
For each block of the number of blocks corresponding to the same number of segments, modulation multilevel information, error correction code length, coding rate, and pilot insertion ratio as in the OFDM transmitter, an error occurs with respect to the demodulated signal generated by the carrier demodulator. An error correction decoding unit that performs correction decoding processing and restores the original data,
The error correction decoding unit
From the table, read the same number of segments, modulation multi-value information, error correction code length, coding rate and pilot insertion ratio as the OFDM transmitter, and the number of zero insertions for each block,
For the block where the number of zero insertions is 0, error correction decoding is performed on the demodulated signal having the same error correction code length as that of the OFDM transmitter, and the original data is restored,
For the block where the number of zero insertions is not 0, subtract the number of zero insertions from the same error correction code length as the OFDM transmitter, insert zero bits of the number of zero insertions into the demodulated signal of the length of the subtraction result, and A first demodulated signal having the same error correction code length as that of the OFDM transmitter is generated, error correction decoding is performed on the first demodulated signal, and zero bits of the zero insertion number are deleted from the signal after error correction decoding. An OFDM receiver characterized in that the data is restored. The OFDM receiver according to claim 7,
The OFDM receiver receives an OFDM signal from the OFDM transmitter of claim 4 instead of the OFDM transmitter of claim 2 or 3,
A value that is a positive integer multiple or a positive integer fraction of the number of bits of data to be transmitted corresponding to all modulated signals arranged in an OFDM frame, with the same error correction code length as that of the OFDM transmitter Is used,
In the case of the same pilot insertion ratio as that of the OFDM transmitter,
The error correction decoding unit
For all blocks, perform error correction decoding on the demodulated signal with the same error correction code length as the OFDM transmitter, and restore the original data,
If the same pilot insertion ratio as the OFDM transmitter is changed,
As the number of zero insertions for each block, a number according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame is used,
The error correction decoding unit
For all the blocks, the number of zero insertions is subtracted from the same error correction code length as that of the OFDM transmitter, and the zero bits of the number of zero insertions are inserted into the demodulated signal having the length of the subtraction result. A first demodulated signal having the same error correction code length is generated, error correction decoding is performed on the first demodulated signal, and zero bits of the zero insertion number are deleted from the signal after error correction decoding to restore the original data An OFDM receiver characterized by: The OFDM receiver according to claim 7,
The OFDM receiver receives an OFDM signal from the OFDM transmitter of claim 5 instead of the OFDM transmitter of claim 2 or 3,
A value that is a positive integer multiple or a positive integer fraction of the number of bits of data to be transmitted corresponding to all modulated signals arranged in an OFDM frame, with the same error correction code length as that of the OFDM transmitter Is used,
In the case of the same pilot insertion ratio as that of the OFDM transmitter,
The error correction decoding unit
For all blocks, perform error correction decoding on the demodulated signal with the same error correction code length as the OFDM transmitter, and restore the original data,
If the same pilot insertion ratio as the OFDM transmitter is changed,
As the number of zero insertions for each block, a number according to the change in the number of bits of the transmission target data corresponding to all the modulation signals arranged in the OFDM frame is used,
The error correction decoding unit
Of the all blocks, the zero insertion number is subtracted from the same error correction code length as that of the OFDM transmitter for a part of the blocks where the zero insertion number is not 0, and the demodulated signal of the length of the subtraction result A first demodulated signal having the same error correction code length as that of the OFDM transmitter is generated by inserting zero bits of the number of zero insertions, error correction decoding is performed on the first demodulated signal, and the signal after error correction decoding is Delete the zero bit of the zero insertion number to restore the original data,
Of all the blocks, the other blocks whose zero insertion number is not 0 are subjected to error correction decoding on the demodulated signal having the same error correction code length as that of the OFDM transmitter, and the original data is restored. An OFDM receiver.

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