JP2000151550A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the out-of-synchronism in RS decoding processing in the case that a large burst error is produced after Viterbi decoding. SOLUTION: An RS decoding section 73 receives output data from a Viterbi decoding section 72 and an AGC output in an OFDM demodulation section 71, the AGC output discriminates a reception level to control a state counter to monitor a state of synchronization in RS decoding. In this case, a state transition of the counter in the synchronization locking is conducted when a reception level is high so as to reduce probability of mis-synchronization locking. Furthermore, mis-synchronization is easily caused when the reception level is higher by controlling number of forward protection stages after that depending on a reception level obtained from the AGC, and when the reception level is small, correct synchronization is not hardly unlocked thereby realizing the receiver where the out-of-synchronization of the RS decoding is hardly caused during mobile reception.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a receiving apparatus in a transmission system using FDM (Orthogonal Frequency Division Multiplexing) modulation and using a concatenated code of at least a Reed-Solomon code and a convolutional code as an error correction code.

[0002]

2. Description of the Related Art In recent years, digital broadcasting has been actively researched. In particular, terrestrial digital broadcasting is being developed for standardization in Japan. At the present stage, in establishing the standards for digital terrestrial broadcasting, OFDM modulation is considered as a modulation method, and a concatenated code of Reed-Solomon (hereinafter, RS) code and convolutional and punctured code is considered as an error correction code. I have. Note that R
The S code is a block code, and it is necessary to detect block synchronization at the time of decoding.

[0003] Here, transmission systems (modulation systems, error correction codes) in other broadcasting services will be briefly described.

First, as a first transmission method, ETS 300 42
The satellite broadcasting (DVB-S) in FIG. 1 is taken as an example. In this method, a concatenated code is used as an error correction code. The system configuration is as shown in FIG.

[0005] In FIG. 8, on the transmission side, an RS encoding unit 11 performs RS encoding for adding a 16-byte parity to a 188-byte transport (TS) packet. The first byte of the 204 bytes after the RS encoding is '47' HEX or its inverse ('B8' HEX). Thereafter, convolutional encoding is performed by the convolutional encoder 12, and QPSK modulation is performed by the QPSK modulator 13 before transmission.

On the other hand, on the receiving side, a QPSK demodulator 21
The Viterbi decoding unit 22 and the RS decoding unit 23 perform respective decoding processes in the reverse order of the transmitting side. Note that the RS decoding unit 23 includes outer interleaving. In this case, the BER (Bi
Assuming that (t Error Rate) = 2 × 10 ⁻⁴ , synchronization detection ('47' detection) necessary for RS decoding is performed.

As a second transmission method, a cable broadcast (DVB-C) in ETS 300 429 will be described as an example. In this method, only the RS code is used as the error correction code.
The system configuration is as shown in FIG.

In FIG. 9, on the transmitting side, an RS encoding unit 31 performs RS encoding for adding a 16-byte parity to a 188-byte transport (TS) packet. The first byte of the 204 bytes after the RS encoding is '47' HEX or its inverse ('B8' HEX). After that, the QAM modulator 32 performs QAM modulation and transmits.

On the other hand, on the receiving side, a QAM demodulator 41, R
The S decoding unit 42 performs each decoding process in the reverse order of the transmission side. Note that the RS decoding unit includes outer interleaving. In this case, as in satellite broadcasting, the BER (Bit Error
Rate) = 2 × 10 ^-4 , synchronization detection ('47' detection) necessary for RS decoding is performed.

FIG. 10 shows an example of a '47' synchronization detection method in RS decoding. In this example, using a 3-bit counter, '47' or 'B8' HEX is detected by matching all bits,
The number of rear protection steps is 2, and the number of front protection steps is 7.

First, the initial state of the counter is set to 7, "47"
or Start searching for 'B8' HEX. Once '47' or 'B8' HEX
Is detected, state 6 is entered. If state 6 is reached, 204
Detect '47' or 'B8' HEX after byte. If it cannot be detected, it will be in state 7 and '4
Look for 7 'or' B8 'HEX. '4 after 204 bytes from state 6
When the 7 'or' B8 'HEX is detected, the status becomes 0, and synchronization is performed.

After that, '47' or 'B8' H every 204 bytes
EX detection is performed. If no EX is detected, the number of states increases by one. If at least one '47' or 'B8' HEX is detected on the way, the number of states becomes 0 again. When the number of states reaches 7,
Regarding loss of synchronization, search for '47' or 'B8' HEX again regardless of 204 bytes.

As described above, when '47' or 'B8' HEX is detected twice in succession, synchronization is determined. This number of times 2 is referred to as the number of backward protection stages. In addition, '47' for 7 consecutive times from state 0
or'B8 'Synchronization is lost when HEX cannot be detected.
This number 7 is referred to as the number of forward protection stages.

As a third transmission method, a terrestrial broadcast (DVB-T) in ETS 300 744 will be described as an example. In this method, as shown in FIG. 11, RS encoding (5
1), convolutional coding (52), OFDM modulation (53)
And performs OFDM demodulation (61), Viterbi decoding (62), and RS decoding (63) on the receiving side. The Viterbi decoder (62) performs the inner interleaving and the RS decoder (63)
Includes outer interleaving.

However, especially in terrestrial digital broadcasting, when synchronous detection of RS decoding ('47' detection) is performed,
Due to the effects of fading and shadows of pedestrian bridges during mobile reception,
A burst error as shown in FIG. 12 occurs. As a countermeasure, inner interleaving is performed. However, when interleaving is insufficient, errors after Viterbi decoding become large bursts, and there is a problem that synchronization is easily lost in the synchronization detection method of FIG.

[0016]

As described above, R
In a conventional terrestrial digital broadcast receiving apparatus that performs the S decoding process, a large burst error occurs due to the effects of fading at the time of mobile reception and shadows of a pedestrian bridge. As a countermeasure, inner interleaving is performed. However, when interleaving is insufficient, errors after Viterbi decoding become large bursts, and there is a problem that synchronization is easily lost in the conventional synchronization detection method.

In order to solve the above-mentioned problems, the present invention provides a receiving apparatus suitable for terrestrial digital broadcasting which can reduce the loss of synchronization in RS decoding processing even if a large burst error occurs after Viterbi decoding. It is intended to provide a device.

[0018]

In order to achieve the above object, the present invention has the following characteristic configuration.

(1) In a receiving apparatus for receiving a transmission signal by a transmission method using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, a demodulation unit that inputs the transmission signal, demodulates the signal, and outputs the demodulated signal. A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output, and a Reed-Solomon decoding that receives the output of the Viterbi decoding unit, performs block synchronization by detecting correlation match between synchronization words, and performs Reed-Solomon decoding And a part,
The Reed-Solomon decoding unit detects the synchronization state of the block synchronization, performs state transition by increasing or decreasing the count value of a synchronization state counter according to the detection result, and the count value is a predetermined number of backward protection stages. When the number of forward protection stages is reached, synchronization is pulled in, synchronization determination means for determining loss of synchronization, reception level determination means for determining the reception level of the transmission signal, and determination results obtained by this means,
A protection stage number control means for controlling the number of front protection stages in accordance with a change in reception level, in such a manner that the number of front protection stages is increased when the reception level is high and the number of front protection stages is reduced when the reception level is low.

In the receiving apparatus having the above configuration, by controlling the number of forward protection stages according to the reception level of the transmission signal, it is easy to lose erroneous synchronization when the reception level is high, and correct when the reception level is low. Synchronization is less likely to occur, thereby realizing a receiver that is less likely to lose RS decoding block synchronization during mobile reception.

(2) In a receiving apparatus for receiving a transmission signal by a transmission method using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, a demodulation unit which inputs the transmission signal, demodulates the signal, and outputs the signal. A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output, and a Reed-Solomon decoding that receives the output of the Viterbi decoding unit, performs block synchronization by detecting correlation match between synchronization words, and performs Reed-Solomon decoding And a part,
The Reed-Solomon decoding unit detects the synchronization state of the block synchronization, performs state transition by increasing or decreasing the count value of a synchronization state counter according to the detection result, and the count value is a predetermined number of backward protection stages. When the number of forward protection stages is reached, synchronization is pulled in, synchronization determination means for determining loss of synchronization, reception level determination means for determining the reception level of the transmission signal, and determination results obtained by this means,
When the reception level is high, the state transition of the synchronization state counter is performed, and when the reception level is low, the state transition of the synchronization state counter is stopped. Transition control means.

In the receiving apparatus having the above configuration, the state transition of the synchronization state counter is controlled in accordance with the reception level of the transmission signal, so that when the reception level is high, erroneous synchronization is easily released, and the reception level is low. In this case, correct synchronization is hardly lost, thereby realizing a receiving apparatus in which the block synchronization of RS decoding during mobile reception is hardly lost.

(3) In a receiving apparatus for receiving a transmission signal by a transmission system using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, a demodulation unit which inputs the transmission signal, demodulates the signal, and outputs the signal. A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output, and a Reed-Solomon decoding that receives the output of the Viterbi decoding unit, performs block synchronization by detecting correlation match between synchronization words, and performs Reed-Solomon decoding And a part,
The Reed-Solomon decoding unit includes: a reception level determination unit that determines a reception level of the transmission signal; and a determination result obtained by this unit. Bigger,
When the reception level is low, a correlation matching condition control means for controlling the correlation matching condition based on the fluctuation of the reception level is provided in such a manner that the number of bits of the correlation matching condition in the synchronization word detection is reduced.

In the receiving apparatus having the above configuration, the number of bits of the correlation matching condition in the synchronization word detection is controlled in accordance with the reception level of the transmission signal, so that when the reception level is high, erroneous synchronization is easily released. If is small,
It is possible to realize a receiving apparatus in which correct synchronization is hardly lost, and thereby block synchronization of RS decoding during mobile reception is hardly lost.

(4) Reception for selectively receiving transmission signals of at least a first transmission system using only Reed-Solomon codes as error correction codes and a second transmission system using concatenated codes of Reed-Solomon codes and convolutional codes. In the apparatus, a plurality of demodulators for demodulating a transmission signal according to each of the transmission schemes, a Viterbi decoder for Viterbi decoding a demodulation output of the transmission signal according to the second transmission scheme, and a decoding output of the Viterbi decoding unit, A selector for selecting any one of the demodulated outputs of the transmission signal according to the first transmission method;
A Reed-Solomon decoding unit for receiving the signal selected by the selector, performing block synchronization by detecting correlation coincidence of the synchronization word, and performing Reed-Solomon decoding, wherein the Reed-Solomon decoding unit performs synchronization of the block synchronization. State transition is performed by increasing or decreasing the count value of the synchronization state counter according to the detection result, and when the count value reaches a predetermined number of backward protection stages and a number of forward protection stages, synchronization is pulled in and synchronization is performed. A synchronization determination unit for determining a deviation, a reception level determination unit for determining a reception level of the transmission signal, and a determination result obtained by this unit. Is smaller, the number of protection stages is controlled in such a manner that the number of front protection stages is reduced by changing the reception level. Stage, detecting the synchronization state of the block synchronization, performing a state transition by increasing or decreasing the count value of the synchronization state counter according to the detection result, the count value to a predetermined number of rear protection stages, the number of front protection stages Synchronization pull-in at the time of arrival, synchronization determination means for determining loss of synchronization, reception level determination means for determining the reception level of the transmission signal, and determination results obtained by this means. State transition of the state counter is performed, and when the reception level is low, state transition control means for controlling the state transition of the synchronization state counter by a change in the reception level in a manner to stop the state transition of the synchronization state counter. Receiving level determining means for determining a receiving level; and a determination result obtained by this means. Correlation matching condition control for controlling the correlation matching condition by changing the reception level in such a manner that the number of bits of the correlation matching condition in the output is increased and the number of bits of the correlation matching condition in the synchronization word detection is reduced when the reception level is small Means, when a transmission signal according to the first transmission method is selected, a condition for detecting block synchronization is fixedly processed, and a transmission signal according to the second transmission method is selected. When the protection stage number control means, state transition control means,
At least one of the correlation matching condition control means is executed.

In the receiving apparatus having the above configuration, at least the first transmission method using only the Reed-Solomon code as the error correction code and the transmission signal using the second transmission method using the concatenated code of the Reed-Solomon code and the convolutional code are selectively used. When a transmission signal according to the first transmission method is selected, the condition for detecting block synchronization is fixedly processed, and when a transmission signal according to the second transmission method is selected, the number of protection stages is controlled. Executing at least one of the state transition control means and the correlation matching condition control means to variably control the block synchronization detection condition according to the reception level, so that any type of transmission signal can be moved. It is possible to realize a receiving apparatus in which block synchronization of RS decoding at the time of reception is hard to be lost.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a receiving apparatus in which the present invention is applied to a third transmission system as a first embodiment. Since the transmitting side is the same as that shown in FIG. 11, the same reference numerals as in FIG. 1 are assigned and the description is omitted.

In FIG. 1, this receiving apparatus is an OFDM
It comprises a demodulation unit 71, a Viterbi decoding unit 72, and an RS decoding unit 73. Note that the Viterbi decoding unit 72 sets the inner interleave to R
It is assumed that S decoding section 73 includes outer interleaving.
The RS decoding unit 73 compares the output data of the Viterbi decoding unit 72 with O
An AGC output from the FDM demodulation unit 71 is input, and a reception level is determined based on the AGC output.
Status counter (not shown) for monitoring the status of synchronization
Control.

The synchronization detection operation by the state counter will be described with reference to FIG. Here, a 4-bit counter is used as the state counter, and "47" or "B8" HEX is detected by matching all bits. The number of rear protection stages is 2, and the number of front protection stages is 15, 8, and 5. I do. Based on the output of the AGC, the reception level is determined in three ways, large, medium and small, with a certain threshold. When the reception level is high, the number of forward protection stages is 5, when the reception level is medium, the number of front protection stages is 8, and when the reception level is low, the number of front protection stages is 15.

First, the initial state of the counter is set to F, and '47'
or Start searching for 'B8' HEX. Once '47' or 'B8' HEX
Is detected, state E is set. When the state becomes E, 204
Detect '47' or 'B8' HEX after byte. If it cannot be detected, it will be in state F and '4
Look for 7 'or' B8 'HEX. '4 204 bytes after status E
When the 7 'or' B8 'HEX is detected, the state becomes 0, and the synchronization is completed. The state transition of the counter at the time of synchronization pull-in is performed only when the reception level is high.

When the reception level is low, the number of forward protection stages is one.
It becomes 5. After synchronization at this time, that is, state 0
The state transition of the counter after the transition will be described. First, 2
'47' or 'B8' HEX detection is performed every 04 bytes, and if not found, the number of states increases by one. If at least one '47' or 'B8' HEX is detected on the way, the number of states becomes zero again. When the number of states becomes F, it is regarded as out of synchronization, and '47' or 'B8' HEX is searched again regardless of 204 bytes.

When the reception level is medium, the number of forward protection stages is eight.
Becomes The state transition of the counter after the synchronization pull-in at this time, that is, after the state becomes the state 0 will be described. '47' or 'B8' HEX detection is performed every 204 bytes, and if not found, the number of states is increased by 2 as 0 → 2 → 4 → 6 → 8 → A → C → E → F. '47' or 'B8' HEX
Is detected, the number of states becomes zero again. When the number of states becomes F, it is regarded as out of synchronization, and '47' or 'B8' HEX is searched again regardless of 204 bytes.

When the reception level is high, the number of forward protection stages is 5
Becomes The state transition of the counter after the synchronization pull-in at this time, that is, after the state becomes the state 0 will be described. '47' or 'B8' HEX detection is performed every 204 bytes, and if not found, the number of states is increased by 4 as 0 → 4 → 8 → C → E → F. If at least one '47' or 'B8' HEX is detected on the way, the number of states becomes zero again. When the number of states becomes F, it is regarded as out of synchronization, and '47' or
Search for 'B8' HEX.

When the reception level judgment value changes while the counter is in a state other than the state 0 or the state F, for example, when the reception level changes to a high level when the reception level is low and the state is 5, 204 bytes later. When '47' or 'B8' HEX is not detected, control is performed in a manner to increase to state 8.

As described above, in the present embodiment, the state transition of the counter at the time of synchronization pull-in is performed only when the reception level is high, so that the probability of pull-in of erroneous synchronization can be reduced. Further, by controlling the number of forward protection stages thereafter, when the reception level is high, erroneous synchronization is easily lost, and when the reception level is low or medium, correct synchronization is hard to be lost. '47' can be easily received.

(Second Embodiment) FIG. 3 is a block diagram showing a configuration of a receiving apparatus in which the present invention is applied to a third transmission system as a second embodiment. Since the transmitting side is the same as that shown in FIG. 11, the same reference numerals as in FIG. 1 are assigned and the description is omitted.

In FIG. 3, this receiving apparatus is an OFDM
It comprises a demodulator 81, a Viterbi decoder 82, and an RS decoder 83. Note that the Viterbi decoding unit 82 sets the inner interleave to R
It is assumed that S decoding section 83 includes outer interleaving.
The RS decoder 83 outputs the output data of the Viterbi decoder 82,
The simple error rate of the Viterbi decoding unit 82 is input, and a state counter (not shown) for monitoring the state of '47' synchronization of RS decoding is controlled by the simple error rate.

Note that the simple error rate is obtained by comparing the hard decision value of the data obtained by reconvolution-encoding the data after Viterbi decoding and the data before Viterbi decoding. Here, by comparing the simple error rate with a certain threshold, the reception level is determined in two ways, large and small.

The synchronization detection operation by the state counter will be described with reference to FIG. Here, a 3-bit counter is used as a state counter, and '47' or 'B8' HEX is detected by matching all bits. The number of rear protection stages is 3, and the number of front protection stages is 7.

First, the initial state of the counter is set to 7, and "47" is set.
or Start searching for 'B8' HEX. Once '47' or 'B8' HEX
Is detected, state 6 is entered. If state 6 is reached, 204
Detect '47' or 'B8' HEX after byte. If it cannot be detected, the state changes to state 7, and the '47' or 'B8' HEX is searched again regardless of the 204 bytes. When the '47' or 'B8' HEX 204 bytes after the state 6 is detected, the state changes to the state 5. State 5
'47' or 'B8' HEX after 204 bytes
Is detected. If it cannot be detected, the state is changed to 7, and the '47' or 'B8' HEX is searched again regardless of the 204 bytes. When a '47' or 'B8' HEX 204 bytes after the state 5 is detected, the state becomes the state 0, whereby the synchronization pull-in is completed.
The state transition of the counter at the time of synchronization pull-in is performed only when the reception level is high.

When the reception level is high, after synchronization is pulled in, that is, after the state becomes 0, '47' is set every 204 bytes.
or 'B8' HEX detection is performed, and if not found, the number of states increases by one. If at least one '47' or 'B8' HEX is detected on the way, the number of states becomes 0 again. When the number of states becomes 7, it is regarded as out of synchronization, and '47' or 'B8' HEX is searched again regardless of 204 bytes. When the reception level is low, the operation of the counter after the synchronization is stopped.

As described above, in this embodiment, the state transition of the counter at the time of synchronization pull-in is performed only when the reception level is high, so that the probability of pull-in of erroneous synchronization can be reduced. Further, by controlling the number of forward protection stages thereafter, when the reception level is low, it is difficult to lose the correct synchronization, and it is possible to realize a receiving apparatus in which the '47' synchronization of RS decoding during mobile reception is hard to be lost.

(Third Embodiment) As a third embodiment, another RS decoding '47' synchronization detection method in the configuration of FIG. 3 will be described with reference to FIG. The RS decoding unit 83 in the present embodiment compares the simple error rate obtained by the Viterbi decoding unit 82 with a certain threshold to determine the reception level as four types of maximum, large, small, and minimum.

The synchronization detection operation by the state counter will be described with reference to FIG. Here, a 3-bit counter is used as the state counter, and '47' o
r 'B8' HEX is detected by matching all bits,
The number of front protection steps is 7.

First, the initial state of the counter is set to 7, and "47" is set.
or Start searching for 'B8' HEX. Once '47' or 'B8' HEX
Is detected, state 6 is entered. If state 6 is reached, 204
Detect '47' or 'B8' HEX after byte. If it cannot be detected, the state changes to state 7, and the '47' or 'B8' HEX is searched again regardless of the 204 bytes. When the '47' or 'B8' HEX 204 bytes after the state 6 is detected, the state changes to the state 5. State 5
'47' or 'B8'HEX after 204 bytes
Is detected. If it cannot be detected, the state changes to state 7, and the '47' or 'B8' HEX is searched again regardless of the 204 bytes. When a '47' or 'B8' HEX 204 bytes after the state 5 is detected, the state becomes the state 0, whereby the synchronization pull-in is completed. The state transition of the counter at the time of synchronization pull-in is performed only when the reception level is maximum, or when the reception level is maximum and maximum.

After synchronization pull-in, that is, after state 0, '47' or 'B8' HEX detection is performed every 204 bytes. If no HEX is detected, the number of states increases by one. On the way 1
If at least '47' or 'B8' HEX is detected, the number of states becomes 0 again. When the number of states becomes 7, it is regarded as out of synchronization and 2
Search for '47' or 'B8' HEX again regardless of 04 bytes. In this operation, the correlation matching condition of '47' or 'B8'HEX is that all bits match when the reception level is maximum, 7 bits match when the reception level is high, 6 bits match when the reception level is low, and when the reception level is minimum. Is determined by a 5-bit match.

As described above, in the present embodiment, the state transition of the counter at the time of synchronization pull-in is performed only when the reception level is at the maximum, or at the maximum and maximum, so that the probability of pull-in of erroneous synchronization can be reduced. it can. Further, when the reception level is high due to the subsequent control of the correlation matching condition, erroneous synchronization is easily lost, and when the reception level is low, correct synchronization is hard to be lost.
It is possible to realize a receiving device in which synchronization is not easily lost.

(Fourth Embodiment) As a fourth embodiment, a receiving apparatus for receiving each of the first, second, and third transmission schemes will be described with reference to FIGS. .

FIG. 6 shows signal processing on the transmitting side of the first, second, and third transmission schemes. In FIG. 6, the same portions as those in FIGS. 8, 9, and 11 are denoted by the same reference numerals, and the description thereof will not be repeated. In FIG. 6, a transmission path A is a signal of the third transmission scheme, and performs RS coding, convolutional coding, and OFDM modulation on the transmission side. The transmission path B is a signal of the first transmission system, and performs RS coding, convolutional coding, and QPSK modulation on the transmission side. The transmission path C is a signal of the second transmission method, and performs RS encoding and QAM modulation on the transmission side.

FIG. 7 is a block diagram showing the configuration of a receiving apparatus for receiving and decoding the above three types of signals. In this receiver, the signal on the transmission line A is received by the demodulation circuit 91A and subjected to OFDM demodulation, the signal on the transmission line B is received by the demodulation circuit 91B and QPSK demodulated, and the signal on the transmission line C is received by the demodulation circuit 91C. And performs QAM demodulation. The selector 92 selects one of the signals of the demodulation circuit 91A and the demodulation circuit 91B, and the Viterbi decoding circuit 93 performs Viterbi decoding on the signal selected by the selector 92. The selector 94 selects one of the output of the Viterbi decoding circuit 93 and the output of the demodulation circuit 91C, and the RS decoding circuit 95 performs RS decoding on the signal selected by the selector 94. The demodulation circuit 91A includes the inner interleave, and the RS decoding circuit 95 includes the outer interleave.

The RS decoding circuit 95 includes a synchronization circuit 951,
An RS decoding unit 952 is provided. The synchronization circuit 951 includes two types of counters 9511 and 9512, and a selector 9513 that selects one of the counter outputs according to a transmission path. The counter 9512 is a counter that performs the state transition operation of FIG. 10 used for the transmission path B and the transmission path C. The counter 9511 is a counter used for the transmission line A, and performs a plurality of controls of one or more of a forward protection stage number, a state transition of a synchronization state counter, and a correlation matching condition in accordance with a change in a reception level. The control signal of the counter 9511 is controlled by the AGC output obtained by the demodulation circuit 91A or the simple error rate obtained by the Viterbi decoding circuit 93.

In the above configuration, when it is desired to view a broadcast using the third transmission method on the transmission line A, the selector 92 selects the output of the demodulation circuit 91A, the selector 94 selects the output of the Viterbi decoding circuit 93, and 9513 causes the output of the counter 9511 to be selected. As a result, FIG.
Alternatively, the configuration is the same as that of the receiving apparatus shown in FIG.

In this case, the counter 9511 uses FIG.
By executing one of the synchronization detection processes shown in FIGS. 4 and 5, the probability of pulling in false synchronization is reduced, false synchronization is easily lost when the reception level is high, and correct synchronization is obtained when the reception level is low. Can be hardly lost, and it is possible to realize a receiving apparatus in which the '47' synchronization of RS decoding during mobile reception is hardly lost.

Next, when it is desired to view a broadcast of the transmission line B in the first transmission system, the selector 92 sets the demodulation circuit 91B
Of the Viterbi decoding circuit 93
Of the counter 951
3 output is selected. Thereby, the configuration becomes the same as that of the receiving apparatus shown in FIG. When the user wants to view a broadcast using the second transmission method on the transmission line C, the selector 92 selects the output of the demodulation circuit 91C, the selector 94 selects the output of the demodulation circuit 91C, and the selector 9513 selects the output of the counter 9513. To select. Thereby, the configuration becomes the same as that of the receiving apparatus shown in FIG. In these cases, by performing the synchronization detection processing shown in FIG. 10 by the counter 9511, reception can be performed as usual.

With the above control, satellite (first transmission method), cable (second transmission method), terrestrial broadcasting (third transmission method) can be received, and RS decoding during mobile reception of terrestrial broadcasting. '47' can be easily received.

[0057]

As described above, according to the present invention, even if a large burst error occurs after Viterbi decoding, a receiving apparatus suitable for terrestrial digital broadcasting, which can reduce loss of synchronization in RS decoding processing. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration including a receiving device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state transition of a synchronization detection operation of RS decoding according to the first embodiment.

FIG. 3 is a block diagram showing a system configuration including a receiving device according to second and third embodiments of the present invention.

FIG. 4 is a diagram showing a state transition of a synchronization detection operation of RS decoding according to the second embodiment.

FIG. 5 is a diagram showing a state transition of a synchronization detection operation of RS decoding according to the third embodiment.

FIG. 6 is a block diagram showing a signal processing configuration on a transmission side according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a receiving device according to a fourth embodiment.

FIG. 8 is a block diagram showing a system configuration example of a conventional satellite digital broadcast (first transmission system).

FIG. 9 is a block diagram showing a system configuration example of a conventional cable digital broadcast (second transmission system).

FIG. 10 is a diagram showing a state transition of a synchronization detection operation of the conventional RS decoding.

FIG. 11 is a block diagram showing a system configuration example of a conventional terrestrial digital broadcast.

FIG. 12 is a diagram illustrating a state of a burst error at the time of mobile reception in OFDM transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... RS encoding part 12 ... Convolution encoding part 13 ... QPSK modulation part 21 ... QPSK demodulation part 22 ... Viterbi decoding part 23 ... RS decoding part 31 ... RS encoding part 32 ... QAM modulation part 41 ... QAM demodulation part 42 ... RS decoder 51 ... RS encoder 52 ... convolution encoder 53 ... OFDM modulator 61,71,81 ... OFDM demodulator 62,72,82 Viterbi decoder 63,73,83 ... RS decoder 91A, 91B , 91C ... demodulation circuit 92 ... selector 93 ... Viterbi decoding circuit 94 ... selector 95 ... RS decoding circuit 951 ... synchronization circuit 9511, 9512 ... counter 9513 ... selector 952 ... RS decoding section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masami Aizawa 5-2-2 Akasaka, Minato-ku, Tokyo Inside the Next Generation Digital Television Broadcasting System Laboratory (72) Inventor Hidenori Tsuboi Shinsugita, Isogo-ku, Yokohama-shi, Kanagawa 8 Town No. F-Terminator of Toshiba Multimedia Technology Research Laboratories (reference)

Claims (8)

[Claims] 1. A receiving apparatus for receiving a transmission signal by a transmission method using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, comprising: a demodulation unit that inputs the transmission signal, demodulates the signal, and outputs the demodulated signal; A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output; and a Reed-Solomon decoding unit that receives the output of the Viterbi decoding unit, performs block synchronization by detecting a correlation match between synchronization words, and performs Reed-Solomon decoding The Reed-Solomon decoding unit detects a synchronization state of the block synchronization, performs state transition by increasing or decreasing the count value of a synchronization state counter according to the detection result, and the count value is defined in advance. Synchronization determination means for pulling in the synchronization when the number of the rear protection stages and the number of the front protection stages have been reached, and determining the loss of synchronization; A reception level determining means for determining the reception level of a signal, from the determination results obtained in this way,
A protection stage number control means for controlling the number of front protection stages by a change in reception level in such a manner that the number of front protection stages is increased when the reception level is high and the number of front protection stages is reduced when the reception level is low. A receiving device characterized by the above-mentioned. 2. A receiving apparatus for receiving a transmission signal by a transmission method using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, comprising: a demodulation unit that inputs the transmission signal, demodulates the signal, and outputs the demodulated signal; A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output; and a Reed-Solomon decoding unit that receives the output of the Viterbi decoding unit, performs block synchronization by detecting a correlation match between synchronization words, and performs Reed-Solomon decoding The Reed-Solomon decoding unit detects a synchronization state of the block synchronization, performs state transition by increasing or decreasing the count value of a synchronization state counter according to the detection result, and the count value is defined in advance. Synchronization determination means for pulling in the synchronization when the number of the rear protection stages and the number of the front protection stages have been reached, and determining the loss of synchronization; A reception level determining means for determining the reception level of a signal, from the determination results obtained in this way,
When the reception level is high, the state transition of the synchronization state counter is performed, and when the reception level is low, the state transition of the synchronization state counter is stopped. A receiving device comprising: a transition control unit. 3. A receiving apparatus for receiving a transmission signal by a transmission method using at least a concatenated code of a Reed-Solomon code and a convolutional code as an error correction code, comprising: a demodulation unit that inputs the transmission signal, demodulates the signal, and outputs the demodulated signal; A Viterbi decoding unit that receives the output of the demodulation unit, performs Viterbi decoding, and outputs the output; and a Reed-Solomon decoding unit that receives the output of the Viterbi decoding unit, performs block synchronization by detecting a correlation match between synchronization words, and performs Reed-Solomon decoding The Reed-Solomon decoding unit includes: a reception level determination unit that determines a reception level of the transmission signal; and a determination result obtained by this unit. Increase the number of bits in the condition,
A receiving apparatus comprising: a correlation matching condition control unit that controls the correlation matching condition by a change in the reception level in a manner that the number of bits of the correlation matching condition in the synchronization word detection is reduced when the reception level is low. 4. A receiving apparatus for selectively receiving a transmission signal according to each of a first transmission method using at least a Reed-Solomon code as an error correction code and a second transmission method using a concatenated code of a Reed-Solomon code and a convolutional code. A plurality of demodulators for demodulating a transmission signal according to each of the transmission schemes; a Viterbi decoder for Viterbi decoding a demodulation output of a transmission signal according to the second transmission scheme; a decoding output of the Viterbi decoder; A selector for selecting one of the demodulation outputs of the transmission signal according to the transmission method of the above, and a Reed-Solomon decoding unit for inputting the signal selected by the selector, performing block synchronization by detecting correlation match of the synchronization word, and performing Reed-Solomon decoding The Reed-Solomon decoding unit detects a synchronization state of the block synchronization, and detects the synchronization state. A state transition is performed by increasing or decreasing the count value of the synchronization state counter according to the result, and when the count value reaches a predetermined number of rearward protection stages and a number of frontal protection stages, synchronization is pulled in.
Synchronization determination means for determining loss of synchronization, reception level determination means for determining the reception level of the transmission signal, and from the determination results obtained by this means, when the reception level is high, increase the number of forward protection stages and When the level is small, the number of protection stages is controlled in such a manner that the number of front protection stages is reduced in the manner of reducing the number of front protection stages. The synchronization state of the block synchronization is detected, and the synchronization state is determined in accordance with the detection result. State transition is performed by increasing / decreasing the count value of the counter, and when the count value reaches a predetermined number of backward protection stages, the number of forward protection stages, synchronization is pulled in.
Synchronization determination means for determining loss of synchronization, reception level determination means for determining the reception level of the transmission signal, and from the determination result obtained by this means, when the reception level is high, perform a state transition of the synchronization state counter. State transition control means for controlling the state transition of the synchronization state counter by a change in the reception level when the reception level is low, in a manner to stop the state transition of the synchronization state counter; and a reception level for determining the reception level of the transmission signal. From the determination means and the determination result obtained by this means, when the reception level is high, the number of bits of the correlation matching condition in the synchronization word detection is increased, and when the reception level is low, the correlation matching condition in the synchronization word detection is A correlation matching condition control means for controlling the correlation matching condition based on the fluctuation of the reception level in a manner of reducing the number of bits. Comprising at least one of the means, when a transmission signal according to the first transmission method is selected,
The detection condition of the block synchronization is fixedly processed, and when a transmission signal according to the second transmission method is selected, at least one of the protection stage number control means, the state transition control means, and the correlation matching condition control means is controlled. A receiving device characterized in that the receiving device is executed. 5. The Reed-Solomon decoding unit according to claim 1, wherein the correlation matching condition of the synchronization word at the time of synchronization pull-in is set to match all bits, and the number of backward protection stages is set to three or more. The receiving device according to any one of the above. 6. The receiving apparatus according to claim 1, wherein said Reed-Solomon decoding unit performs synchronization pull-in when a reception level is high. 7. The demodulation unit includes an automatic gain control unit that controls an input level of a transmission signal to be constant, and the reception level determination unit includes a gain control unit that is obtained by the automatic gain control unit of the demodulation unit. 7. The receiving device according to claim 1, wherein the receiving level is determined from the signal. 8. The reception level determination unit according to claim 1, wherein the reception level determination unit determines a reception level from a simple error rate after Viterbi decoding of the Viterbi decoding unit.
7. The receiving device according to any one of 6.