JP2961105B1 - OFDM receiver - Google Patents

Abstract

A mode and OFDM frame synchronization can be detected even when TMCC decoding cannot be performed, thereby enabling data decoding. SOLUTION: An inner code decoding unit 25 searches all modes of the number of segments of a hierarchy, detection, mapping, time interleave depth, and puncture rate, and determines a correct mode based on a simple error rate after Viterbi decoding. For example, the number of segments in the hierarchy, detection, mapping,
The time interleave depth and the puncture rate are set to certain parameters, the determination based on the simple error rate after Viterbi decoding is performed, and the determination based on the simple error rate is performed by changing the parameters until the simple error rate becomes smaller than a certain value. This is repeated to determine the correct mode. After the mode is determined, the outer code decoding unit 26 detects the synchronization of Reed-Solomon decoding. With the mode control described above, decoding can be performed even when TMCC cannot be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses OFDM (Orthogonal Frequency Division Multiplexing) modulation, which is a type of multicarrier modulation, and equally divides all carriers into a plurality of blocks (hereinafter referred to as segments) for transmission. OFD in the system
M receiver.

[0002]

2. Description of the Related Art In recent years, terrestrial digital broadcasting has been actively studied. Among them, OFDM modulation is regarded as a promising digital modulation method. Above all, a method of equally dividing all carriers and dividing them into a plurality of segments for transmission is being studied.

FIG. 9 shows an OFDM transmission frame structure currently under study. Here, the number of FFT points is 204
8 is assumed. Among them, 1404 carriers are used according to the bandwidth. 108 carriers are defined as one segment and divided into 13 segments so that different information can be transmitted for each segment.

[0004] One layer is transmitted using several segments, and a maximum of four layers can be transmitted. Although there are many combinations for distributing 13 segments to a maximum of four layers, operation is performed in limited combinations. At least one carrier called a TMCC called a parameter or a mode of a frame structure is arranged for each segment. Here, 1 [OFDM frame] = 204 [OFDM symbol]
And The number of information carriers per segment is 96
Book. FIG. 10 shows an example of a simple OFDM receiver that receives only one layer, which can be considered when the above method is adopted. In the following description, it is assumed that OFDM symbol synchronization has been established.
The display of the DM symbol synchronization signal in the drawing is omitted.

[0005] In FIG. 10, an OFDM reception signal is FF
After the signal is converted from the time axis direction to the frequency axis direction by the fast Fourier transform of the T processing unit 11, the signal is read out in the order of the segment in the OFDM frame decoding processing unit 12, and the delay detection or the synchronous detection is performed by the demodulation unit 13. Applied selectively. After that, the frequency and time deinterleaving section 14 performs frequency and time deinterleaving, and then the demapping section 15 performs QPS
Any of K, 16QAM, and 64QAM demapping is performed, and the bit deinterleave processing unit 16 performs deinterleaving in bit units.

[0006] Subsequently, the inner code decoder 17 receives the decoding process of depuncturing and Viterbi decoding, and is input to the outer code decoder 18. In the outer code decoding unit 18, after a descrambling process is performed along with deinterleaving process in units of bytes in an outer deinterleaving processing unit 181, a Reed-Solomon (hereinafter referred to as RS) decoding processing unit 183 passes through an energy spreading unit 182. After undergoing a decoding process, decoded data is obtained. Here, the RS code is a type of block code, and adds a 16-byte parity to a 188-byte transport stream to form a transmission packet in 204-byte units.

On the other hand, the OFDM frame decoder 12 detects a TMCC for controlling timing and parameters, and the TMCC is decoded by a TMCC decoder 21. In the decoded TMCC signal, the parameter indicating the modulation scheme is provided by the demodulator 13 and the demapping processor 1
5. Used for controlling the bit deinterleave processing unit 16. The convolutional coding rate is used for controlling the inner code decoder 17. The parameters of the interleave method are used for controlling the frequency and time deinterleave processing unit 14. The parameters of the layer structure indicating the layer number and the number of segments constituting the layer are stored in each processing unit 13.
-18 are used for control. OFDM frame synchronization is
It is used for controlling the frequency and time deinterleave processing unit 14 and the outer code decoding unit 18.

The outer code decoder 18 needs to synchronize transmission packets. One OFDM frame includes an integer number of transmission packets, and the head of the OFDM frame matches the head of the transmission packet. For this reason, the outer code decoding unit 18 identifies the synchronization state of the transmission packet from the OFDM frame synchronization signal of TMCC and the convolutional coding rate, finds the synchronization error, and uses it for timing control.

[0009]

However, in an environment where multipaths occur in a transmission line, frequency selective interference in which the reception level of a specific carrier is reduced may occur. Therefore, as shown by the * mark in FIG.
May decrease the reception level of the carrier. When the TMCC carrier is disturbed in this way, the TMC
C decoding becomes impossible, various parameters and OFDM frame synchronization are not understood, and the simple OFDM receiver in FIG. 10 cannot decode data.

[0010] In order to solve the above-mentioned problems, the present invention provides a method for transmitting TM information from a carrier to which parameter information is transmitted.
An object of the present invention is to provide an OFDM receiving apparatus that can decode data even when CC decoding cannot be performed.

[0011]

In order to achieve the above object, an OFDM receiver according to the present invention is configured as follows.

(1) When transmitting a data signal using a Reed-Solomon code and a concatenated convolutional and punctured code as an error correction code by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, all carriers are equally divided. Can be divided into multiple segments and layer transmission is possible with any combination of segments. For each layer, the number of segments,
Receives an OFDM signal in which at least one of a modulation scheme , a time interleave depth (including zero, that is, no time interleave), and a puncture rate can take a plurality of types .
That the OFDM receiver, a demodulator for <br/> demodulating a received OFDM signal, frequency and time deinterleaving for performing time deinterleaving of the the depth specified with this applying frequency deinterleaving an output signal of the demodulator A processing unit, a demapping processing unit for demapping the output of the frequency and time deinterleaving processing unit with a specified type, a bit deinterleaving processing unit for performing bit deinterleaving on the output of the demapping processing unit, An inner code decoder that performs depuncturing and performs Viterbi decoding at a rate specified by the output of the bit deinterleave processor, performs synchronization detection on the output of the inner code decoder, and performs outer code decoding including Reed-Solomon decoding Estimating the error rate from the Viterbi decoding output of the outer code decoder and the inner code decoder Error rate estimating means, and at least one of the number of hierarchical segments in the demodulation unit, the time interleaving depth in the frequency and time deinterleaving processing unit, the mapping in the demapping processing unit, and the puncturing rate in the inner code decoding unit. Search means for searching for the type of the error rate estimating means to detect and determine the type in which the estimation result of the error rate estimation means is within an allowable range; and And a synchronous control means for performing detection control.

In this configuration, an OF having a segment structure
When the OFDM signal transmitted by the DM transmission system can take at least one of a plurality of types (modes) of at least one of the number of layers in the hierarchy, mapping, time interleaving depth, and puncturing rate, all modes or specific modes are considered. By estimating the error rate from the Viterbi decoding output of the inner code decoding unit, it is determined whether the reception mode is correct or not. Since the synchronization detection control is performed after the mode is determined, parameter information specifying the mode is transmitted. Even if the TMCC of a certain carrier cannot be detected, the mode can be detected and decoding can be performed.

(2) In the transmission method of (1), when the frequency interleaving is different for each OFDM symbol and the rule is determined for each OFDM frame, the frequency and time deinterleaving processing unit sets the first OFDM symbol in the OFDM frame. And performs frequency deinterleaving according to a specified rule, and the search means includes a search for a rule of a head OFDM symbol of an OFDM frame in the frequency and time deinterleaving processing unit.

In this configuration, the frequency interleave is O
Even when the rule is determined for each OFDM frame, which differs for each FDM symbol, the frequency and time deinterleave processing unit detects the first OFDM symbol of the OFDM frame, and searches for the rule, so that the frequency is determined according to the appropriate rule. Interleave processing is enabled.

(3) In the transmission method of (1), when the frequency interleaving is different for each OFDM symbol and the rule is determined for each OFDM frame, the frequency and time deinterleaving processing unit sets the head of the designated OFDM frame. And performs frequency deinterleaving according to a specified rule, wherein the search means includes:
The frequency and time deinterleave processing unit tentatively determines the first OFDM symbol of the OFDM frame and performs a search for sequentially switching the frequency interleaving rule, and the synchronization control unit tentatively determines by the search unit The OFDM frame synchronization is detected and determined from the relationship between the determined head of the OFDM frame and the synchronization position of the Reed-Solomon decoding.

In this configuration, the frequency interleave is O
Even when the rule is determined for each OFDM frame, which differs for each FDM symbol, the first OFDM frame OFDM frame is transmitted to the frequency and time deinterleave processing unit.
By tentatively designating the symbol and searching for the rule, the frequency interleaving process can be performed with an appropriate rule, and furthermore, the head of the tentatively determined OFDM frame and the synchronous position of the Reed-Solomon decoding are synchronized. By determining and determining OFDM frame synchronization from the relationship, it is possible to detect OFDM frame synchronization as well as the rules of mode and frequency interleaving.

(4) In the transmission method of (1), when the frequency interleaving is different for each OFDM symbol and the rule is determined for each OFDM frame, the frequency and time deinterleaving processing unit sets the head of the designated OFDM frame. , And performs frequency deinterleaving according to the specified rule, and further synchronizes the decoding of the transmission packet forming the Reed-Solomon code from the specified OFDM symbol position at the head of the OFDM frame and the amount of hard delay. The packet synchronization error estimating means for estimating the position shift (hereinafter, packet synchronization error) and the frequency and time interleave processing unit are temporarily
The position of the OFDM symbol at the head of the FDM frame is determined, the position of the OFDM symbol at the head of the OFDM frame is determined from the packet synchronization error estimated by the packet synchronization error estimating means, and the frequency and time interleave processing unit searches for the symbol. And a search control means for repeatedly executing a symbol search until the packet synchronization error estimating means eliminates an error.

In this configuration, the provisionally determined OFDM
For the position of the OFDM symbol at the head of the frame, a packet synchronization error is estimated from the position and the amount of hard delay, and a position considered to be correct from the estimation result is searched for.
By repeating this process, the true symbol position is obtained, whereby the symbol position at the head of the OFDM frame can be detected more accurately.

(5) In the configuration of (4), when the synchronization error continues in the packet synchronization error estimating means, the search control means may temporarily determine the OFDM head of the OFDM frame.
The DM symbol position is repeatedly shifted in units of one or more OFDM symbols to search for packet synchronization.

In this configuration, one or more OFDM symbol positions at the head of the provisionally determined OFDM frame are determined.
The packet synchronization can be easily and reliably searched for by repeatedly shifting each DM symbol.

(6) In the configuration of (4), the search control means includes a table indicating the relationship between the packet synchronization error estimated by the packet error estimation means and the OFDM symbol position at the head of the OFDM frame. To find the OFDM symbol position.

In this configuration, the speed and simplification of symbol position search are realized by referring to and using a table indicating the relationship between the estimated packet synchronization error and the OFDM symbol position at the head of the OFDM frame.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

(First Embodiment) FIG. 1 shows the configuration of a simple OFDM receiver for receiving only one layer as a first embodiment of the present invention. The input signal is an OFF that has been subjected to FFT processing and frame decoding processing by an FFT processing section and OFDM frame decoding processing section (not shown).
This is a DM decode signal. This OFDM decoded signal is selectively subjected to delay detection or synchronous detection by the demodulation unit 21 and then to the frequency and time deinterleave processing unit 2.
2, deinterleaving is performed in the frequency direction and the time direction, and QPSK, 16Q
Either AM or 64QAM demapping is performed, and the bit deinterleave processing unit 24 performs bit-wise deinterleaving.

Subsequently, the inner code decoding unit 25 receives the decoding process of depuncturing and Viterbi decoding and inputs the decoding process to the outer code decoding unit 26. The outer code decoding unit 26 performs an RS decoding process after performing a deinterleaving process, a descrambling process, and an energy spreading process on a byte basis, thereby obtaining decoded data. The main timing control uses OFDM symbol synchronization.

Here, the demodulation section 21 has one of two detection modes, synchronous detection and delay detection, for each segment. In the frequency and time deinterleave processing unit 22,
Time depth has multiple modes. Demapping processing unit 2
In No. 3, the modulation method has a plurality of modes. The control of the bit deinterleave processing unit 24 differs depending on the mode of a plurality of modulation schemes. In the inner code decoding unit 25, the puncture rate has a plurality of modes. In the outer code decoding unit 26, there is no particular mode, but it is necessary to synchronize transmission packets.

As shown in FIG. 2, the inner code decoding unit 25 includes a depuncturing unit 251, a Viterbi decoding unit 252,
It comprises a simple error rate estimator 253, a mode determiner 254, and a mode switching controller 255. That is, when the input signal is depunctured, subjected to Viterbi decoding, and output, the simple error rate estimating unit 253 compares the signal before depuncturing with the signal after Viterbi decoding to estimate the simple error rate, and the mode determining unit 254 It is determined from the simple error rate estimation result whether the current mode is correct. If the mode is not correct, the mode switching control unit 255 generates a mode switching signal for instructing a parameter change for the blocks 21 to 24 and outputs it to the corresponding block. This mode switching control is performed until a correct mode is obtained.

As for the frequency and time deinterleave processing unit 22, as shown in FIG. 3, a configuration and a method for performing a frequency deinterleave 221 and a time deinterleave 222 in this order have been studied. The frequency deinterleave 221 is used for the carrier randomization 22 in the segment.
11, intra-segment carrier rotation 2212,
It consists of inter-segment deinterleave 2213. FIG. 4 shows intra-segment carrier randomization 2211
This will be described with reference to FIG. One segment is composed of 104 carriers as shown in FIG. As shown in FIG. 4B, the 104 carriers include 96 information carriers excluding the TMCC and the pilot (P). The process of randomly changing the order of the 96 information carriers as shown in FIG. 4C is called intra-segment carrier randomization.

Intra-segment carrier rotation 22
12 will be described with reference to FIG. When a certain layer A is transmitted using N segments, the number of segments of the layer A in one OFDM frame is (204 × N). O
An index k is assigned from the head segment of the FDM frame as shown in FIG. The segment with k = 0 remains as it is, and the segment with k = 1 shifts the data carrier by one, and rotates one carrier at the end to the opposite end.
The segment with k = 2 shifts the data carrier by two and rotates the two carriers at the end to the opposite end. In this manner, the shift is performed for each segment (k mod 96).

The inter-segment interleave 2213 is
As shown in FIG. 6, all information carriers in N segments in one OFDM symbol are interleaved as blocks.

Intra-segment carrier randomization 221
1 and the inter-segment deinterleave 2213
Although control can be performed using FDM symbol synchronization, OFDM frame synchronization is required for the intra-segment carrier rotation 2212.

The time interleave 222 is a convolutional interleave having a plurality of time depth modes, and can be controlled by using time depth information and OFDM symbol synchronization.

The various interleaving orders in the frequency and time deinterleaving section 22 may be various combinations. If the intra-segment carrier rotation 2211 is not performed, the frequency and time deinterleave processing unit 22 does not need OFDM frame synchronization. Hereinafter, the case where intra-segment carrier rotation is not performed is referred to as transmission method 1, and the case where carrier rotation is performed is referred to as transmission method 2. In the present embodiment, the case of the transmission method 1 is assumed.

In the above configuration, the O
The mode control operation of the FDM receiver will be described.

First, the inner code decoding unit 25 searches for all modes of the number of segments in the hierarchy, detection, mapping, time interleave depth, and puncture rate, and determines the correct mode based on the simple error rate after Viterbi decoding. For example, the number of layers in the hierarchy, detection, mapping, time interleave depth, and puncture rate are set to certain parameters. If the simple error rate after Viterbi decoding is smaller than a certain value, the mode is determined to be correct. If the simple error rate after Viterbi decoding is larger than a certain value, the parameter is changed and the determination based on the simple error rate is performed. This is repeated to determine the correct mode. After the mode is determined, the outer code decoding unit 26 detects the synchronization of Reed-Solomon decoding.

With the mode control described above, decoding is possible even when TMCC cannot be detected. However, if the mode is limited in terms of service operation, it is sufficient to search only for the limited mode.

(Second Embodiment) The configuration of this embodiment is as follows.
This is basically the same as the configuration of the first embodiment shown in FIG. Therefore, the configuration diagram and its operation description are omitted.

The difference from the first embodiment lies in the control method in mode determination. That is, in the present embodiment,
The inner code decoding unit 25 tentatively determines the first OFDM symbol of the mode determination OFDM frame, sets the number of layers in the hierarchy, detection, mapping, time interleave depth, and puncture rate to certain parameters, and sets a simple parameter after Viterbi decoding. If the error rate is smaller than a certain value, the mode is determined to be correct. If the simple error rate after Viterbi decoding is larger than a certain value, the parameter and the OFDM
The OFDM symbol at the head of the frame is changed to make a determination based on the simple error rate. This is repeated to determine the correct mode.

The above mode control enables decoding even when TMCC cannot be detected. However, if the mode is limited in terms of service operation, it is sufficient to search only for the limited mode.

(Third Embodiment) FIG. 7 shows the configuration of an OFDM receiver according to the above-mentioned transmission system 2 as a third embodiment of the present invention. In FIG. 7, FIG.
The same parts as those described above are denoted by the same reference numerals, and different parts will be described here.

In the present embodiment, similarly to the second embodiment, the inner code decoding unit 25 tentatively determines the first OFDM symbol of the OFDM frame, and determines the number of segments in the hierarchy, detection, mapping, and time interleave depth. The puncture rate is set to a certain parameter, and if the simple error rate after Viterbi decoding is smaller than a certain value, the mode is determined to be correct. If the simple error rate after Viterbi decoding is larger than a certain value, the parameter is changed and the determination based on the simple error rate is performed. This is repeated to determine the correct mode.

A feature of the present embodiment is that, in the mode control, a value to be compared with the simplified error rate after Viterbi decoding when determining the correct mode is set to be relatively large. As a result, even if the tentatively determined OFDM symbol position at the beginning of the OFDM frame is incorrect, packet synchronization may be detected in some cases. At this time, from the tentatively determined OFDM symbol position and the packet synchronization of the head of the OFDM frame, the correct OFDM frame head
An FDM symbol position can be determined.

Specifically, in the outer code decoding unit 26,
Estimate the packet synchronization from the provisionally determined OFDM symbol position at the beginning of the OFDM frame and the amount of hard delay,
It is sufficient to have a table or the like for determining the OFDM symbol position at the head of the OFDM frame from the deviation from the detected packet synchronization. In this case, the frequency and time deinterleave processing unit 22 is controlled so that the frame starts from the first OFDM symbol position of the OFDM frame obtained from this table.

However, there is a case where the detection of the packet synchronization cannot be detected by the above control. Therefore, it is noted that the smaller the difference between the provisionally determined head of the OFDM frame and the position of the head of the correct OFDM frame is, the higher the possibility that packet synchronization can be detected. That is, a search for the head OFDM symbol position of the provisionally determined OFDM frame is performed by a plurality of OFDM symbols or one OFD symbol.
By shifting by M symbols, it is possible to reduce the average time required for detecting packet synchronization.

FIG. 8 shows a specific configuration of the outer code decoding unit 26. 8, an outer deinterleave processing unit 261, an energy spreading unit 262, an RS decoding processing unit 26
3 is an outer deinterleave processor 181 of the outer code decoder 18 shown in FIG.
It has the same configuration as the decryption processing unit 183. The outer code decoding unit 26 further includes a packet synchronization error estimation unit 264 and a frame head search control unit 265.

The packet error estimator 264 calculates the packet synchronization error (the transmission packet constituting the Reed-Solomon code) from the tentatively determined OFDM symbol position of the OFDM frame and the amount of hard delay (the time required for processing each processing block). (A shift of the synchronization position at the time of decoding), and the estimation result is sent to the frame head search control unit 265.

The frame head search control section 265 determines the detected packet synchronization error and the head ODM of the OFDM frame.
A table showing the relationship with the FDM symbol position is provided. With reference to this table, the first OFDM symbol position of the OFDM frame corresponding to the packet synchronization error estimation result is obtained, and the frequency and time deinterleaving is performed so that the frame starts from that position. The processing unit 22 is controlled. As a result of this control, if the packet synchronization error continues, the search for the head OFDM symbol position of the provisionally determined OFDM frame is performed for each of a plurality of OFDM symbols or one OFDM symbol.
By shifting symbols one by one, the average time required for detecting packet synchronization is reduced.

After detecting packet synchronization in this way, the first OFDM frame of the provisionally determined OFDM frame
From the symbol position and the packet synchronization, a correct OFDM symbol position at the beginning of the OFDM frame can be obtained. The above control enables decoding even when TMCC cannot be detected.

In the present embodiment, if the mode is limited in terms of service operation, only the limited mode needs to be searched.

[0051]

As described above, according to the present invention, even when the TMCC decoding cannot be performed from the carrier to which the parameter information is transmitted, the mode (and the OFDM frame synchronization) can be obtained.
Can be detected, and an OFDM receiver capable of decoding data can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an OFDM receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of an inner code decoding unit according to the first embodiment.

FIG. 3 is a block diagram illustrating a specific configuration of a frequency and time deinterleave processing unit according to the first embodiment;

FIG. 4 is a diagram for explaining an example of intra-segment carrier randomization of the frequency and time deinterleave processing unit.

FIG. 5 is a diagram for explaining an example of intra-segment carrier rotation of the frequency and time deinterleave processing unit.

FIG. 6 is a diagram for describing an example of inter-segment interleaving of the frequency and time deinterleaving processing unit.

FIG. 7 is a block diagram illustrating a configuration of an OFDM receiver according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing a specific configuration of an outer code decoding unit according to the third embodiment.

FIG. 9 is a diagram showing an OFDM transmission frame structure that is being studied in a research stage of digital terrestrial broadcasting.

FIG. 10 is a diagram illustrating an OFDM transmission frame structure of FIG. 9;
Simple O to receive only one layer signal from FDM transmission signal
FIG. 2 is a block diagram illustrating a configuration of an FDM receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... FFT processing part 12 ... OFDM frame decoding processing part 13 ... Demodulation part 14 ... Frequency and time deinterleave processing part 15 ... Demapping processing part 16 ... Bit deinterleave processing part 17 ... Inner code decoding part 18 ... Outer code decoding part 181, outer deinterleave processor 182, energy spreader 183, Reed-Solomon decoder 21, demodulator 22, frequency and time deinterleaver 221, frequency deinterleave 2211, carrier randomization in segment 2212, carrier rotation in segment 2213 ... inter-segment deinterleave 222 ... time deinterleave 23 ... demapping processing unit 24 ... bit deinterleave processing unit 25 ... internal code decoding unit 251 ... depuncturing unit 252 ... Viterbi decoding unit 25 ... Simplified error rate estimating unit 254 ... Mode judging unit 255 ... Mode switching control unit 26 ... Outer code decoding unit 261 ... Outer deinterleave processing unit 262 ... Energy spreading unit 263 ... RS decoding processing unit 264 ... Packet synchronization error estimating unit 265 ... Frame head search control unit

Continued on the front page (72) Inventor Masami Aizawa 5-2-2 Akasaka, Minato-ku, Tokyo Inside the Next Generation Digital Television Broadcasting System Research Laboratories (72) Inventor Hidenori Tsuboi Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa 8 Toshiba Multimedia Engineering Laboratory Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) H04J 11/00

Claims (6)

(57) [Claims] When transmitting a data signal using a Reed-Solomon code and a concatenated concatenated and punctured code as an error correction code by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, all carriers are equally divided. are possible hierarchical transmission in any combination of segments divided into a plurality of segments, each hierarchy, the number of segments, modulation side
OF receiving a OFDM signal in which at least one of a formula , a time interleaving depth (including zero, that is, no time interleaving), and a puncturing rate can take a plurality of types.
A demodulation unit for demodulating the received OFDM signal in the DM receiving apparatus; a frequency and time deinterleaving processing unit for performing frequency deinterleaving on an output signal of the demodulation unit and performing time deinterleaving at a specified depth; A demapping processing unit for demapping the output of the frequency and time deinterleaving processing unit in a specified type; a bit deinterleaving processing unit for performing bit deinterleaving on the output of the demapping processing unit; and a bit deinterleaving processing unit An inner code decoder that performs depuncturing and Viterbi decoding at a rate specified for the output of the inner code decoder; and an outer code decoder that performs synchronization detection on the output of the inner code decoder and performs outer code decoding including Reed-Solomon decoding. Error in estimating the error rate from the Viterbi decoding output of the inner code decoding unit. Rate estimating means, at least one of the number of segments in the hierarchy in the demodulation section, the time interleaving depth in the frequency and time deinterleaving section, the mapping in the demapping section, and the puncturing rate in the inner code decoding section. A search means for searching for a type and detecting and determining a type in which an estimation result of the error rate estimating means is within an allowable range; and detecting and controlling the synchronization of Reed-Solomon decoding in the outer code decoding unit after the type is determined by the search means. OFDM receiving apparatus, comprising: a synchronization control unit for performing 2. In the OFDM transmission method, when frequency interleaving is different for each OFDM symbol and a rule is determined for each OFDM frame, the frequency and time deinterleaving processing unit performs OFD processing.
Detecting the first OFDM symbol of the M frame and performing frequency deinterleaving according to a specified rule, wherein the search means includes a search for a rule of the first OFDM symbol of the OFDM frame in the frequency and time deinterleaving processing unit. Claim 1 characterized by the following:
5. The OFDM receiver according to claim 1. 3. In the OFDM transmission method, when frequency interleaving is different for each OFDM symbol and rules are determined for each OFDM frame, the frequency and time deinterleaving processing unit is configured to: And performs frequency deinterleaving according to a specified rule. The search means sends a first OFD of the OFDM frame to the frequency and time deinterleave processing unit.
M symbols are provisionally determined, and a search for sequentially switching the frequency interleaving rule is performed. The synchronization control unit determines a relationship between a head of the OFDM frame provisionally determined by the search unit and a synchronization position of the Reed-Solomon decoding. 2. The OFDM receiving apparatus according to claim 1, wherein the OFDM frame synchronization is detected and determined from. 4. In the OFDM transmission method, when frequency interleaving is different for each OFDM symbol and rules are determined for each OFDM frame, the frequency and time deinterleaving processing unit performs the first OFDM symbol of the designated OFDM frame. And performs frequency deinterleaving according to the specified rule, and furthermore, the OFD at the head of the specified OFDM frame
A packet synchronization error estimating means for estimating a shift of a synchronization position (hereinafter, a packet synchronization error) at the time of decoding of a transmission packet forming the Reed-Solomon code from the M symbol position and the amount of hard delay; On the other hand, the position of the OFDM symbol head at the head of the OFDM frame is tentatively determined, and the position of the OFDM symbol at the head of the OFDM frame is obtained from the packet synchronization error estimated by the packet synchronization error estimating means. 2. The OFDM receiving apparatus according to claim 1, further comprising: search control means for causing the symbol to be searched and repeatedly performing a symbol search until the packet synchronization error estimating means eliminates an error. 5. The search control means, when the packet synchronization error estimating means continues the synchronization error, tentatively determines an OF.
5. The OFDM according to claim 4, wherein the OFDM symbol position at the head of the DM frame is repeatedly shifted in units of one or more OFDM symbols to search for packet synchronization.
Receiver. 6. The search control means includes a table indicating a relationship between a packet synchronization error estimated by the packet error estimating means and an OFDM symbol position at the head of an OFDM frame, and refers to the table to determine an OFDM symbol position. 5. The OFDM receiver according to claim 4, wherein the value is obtained.