JP2003110538A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in the performance of synchronizing processing even when error-correcting encoding is implemented on a synchronizing code together with a main signal. SOLUTION: On a transmitter side, a main signal S1 and a synchronizing code S2 to be transmitted are multiplexed in time division manner by a synchronizing code multiplexing part 11 according to a frame structure, and error correction is implemented on the multiplexed synchronizing code + main signal by an error-correcting encoding part 12. Then, the signal and code are transmitted by applying modulating processing such as PSK, QAM or the like while changing a modulation system by a modulation part 13 corresponding to the part of the synchronizing code or main signal. On the receiver side, in a synchronizing detecting part 22, synchronizing is detected by utilizing a part to become unique after error correction for the synchronizing code. In such a case, by selecting a code having the unique part to become the code of high correlation in the signal after error-correcting encoding for the synchronizing code S2, erroneous synchronizing detection can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device used for digital broadcasting, for example, which receives a signal which is transmitted by error-correcting coding a synchronous code and a main signal together.

[0002]

2. Description of the Related Art In recent years, digital satellite television broadcasting has been realized and is becoming widespread. However, due to the limitation of the number of transmission paths, the need for hierarchical transmission by time division multiplexing has arisen.

Here, in time division multiplexing transmission, when the modulation method in time division can be changed, demodulation cannot be performed correctly without recognizing the frame structure, and therefore synchronization determination is essential.

In digital transmission, error correction is indispensable from the viewpoint of transmission line changes and improvement of transmission characteristics. Above all, from the viewpoint of easiness of operation of the error correction circuit, errors including synchronization codes are included. A method of correction coding is conceivable.

However, if the sync code changes due to error correction coding, the sync performance may deteriorate. Therefore, in the conventional digital transmission, after all, processing such as not encoding the synchronous portion is performed.

[0006]

As described above, in the conventional digital transmission, when the sync code is added to the main signal and the sync code is combined with the error correction code,
The performance degradation of the synchronization process becomes a problem.

The present invention solves the above problems, and suppresses the performance deterioration of the synchronization processing even when the synchronization code is added and error correction coded when the synchronization code is added to the main signal for digital transmission. An object of the present invention is to provide a receiving device for receiving a digital transmission signal by a synchronization method that can satisfy both the performance of the synchronization processing and the error correction processing capability.

[0008]

In order to achieve the above object, a receiving method according to the present invention adds a sync code to a main signal and combines the sync code and the main signal to form a polynomial G133 which is a non-systematic code. When a hexadecimal number 1B95h is used as a synchronization code when receiving a transmission signal by a synchronization method in which convolutional encoding is performed by 171 and then transmitted, 32 of the code after the convolutional encoding is obtained from the received signal of the transmission signal.
EC in the hexadecimal number from the last 20 bits of the bit signal
The feature is that D28h is detected and synchronization is determined based on the detection result.

Further, the receiving apparatus according to the present invention adds hexadecimal 1B95h as a synchronization code to the main signal, and the synchronization code and the main signal are combined to form a polynomial G13 which is a non-systematic code.
A receiving device used for a transmission system for performing convolutional coding according to 3, 171, and receiving the transmission signal, wherein a 32-bit signal of the code after the convolutional coding is received from the received transmission signal. It is characterized by comprising a detecting means for detecting the hexadecimal ECD 28h from the last 20 bits, and a synchronization determining means for determining synchronization based on the detection result of this detecting means.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a system configuration using the synchronization method according to the present invention. First, on the transmitter side, the synchronous code multiplexer 11 multiplexes the main signal S1 and the synchronous code S2 to be transmitted in time division according to the frame structure shown in FIG. The error correction coding unit 12 is a synchronous code multiplexing unit 11
Error correction is applied to the synchronous code + main signal obtained in step 1.
The modulation unit 13 performs a modulation process such as PSK or QAM on the signal error-correction-coded by the error-correction coding unit 12 while changing the modulation method according to the sync code or the main signal portion, and transmits the signal.

On the other hand, on the receiving device side, the demodulation section 21 performs a demodulation operation so as to enable signal processing and extracts a signal component. The synchronization detection unit 22 detects, from the signals extracted by the demodulation unit 21, a synchronization code or a difference between the synchronization codes. The synchronization determination unit 23 determines whether the signal detected by the synchronization detection unit 22 is a synchronization signal,
The frame structure is reproduced and returned to the demodulation unit 21.

In the synchronization detector 22, the synchronization code is detected by utilizing the unique portion after the error correction. At this time, it is possible to reduce erroneous synchronization detection by selecting, as the synchronization code S2, a code in which a unique portion in the signal after the error correction encoding has a high correlation. .

In the format of the sync code + main signal shown in FIG. 2, when error correction is continuously applied to the sync code and the main signal, the original signal component does not remain depending on the type of error correction, and synchronization judgment becomes difficult. Become. The types of error correction coding schemes will be described below.

First, there are many systematic codes (the ones to which the original signal + correction code is added) in the block codes and the like.
In particular, since many convolutional codes are non-systematic codes (not the same as the original signal), even if the correlation is selected to be high before encoding, compensation that the synchronous code after encoding is highly correlated There is no. Example) Systematic code (for example, block code) 135Ah → 135A7932h (= the first half is the same code) Non-systematic code (for example, convolutional code) 1B95h → ××× ECD28h (xx × is indefinite, no matching part) Synchronous code in FIG. An example of a + header + main signal multiplexing format is shown. As shown in the figure, synchronization is established especially when header information indicating each modulation method is included after synchronous encoding, or when the modulation method is time-division multiplexed and demodulation operation according to the modulation method is performed. Only after that, the error correction itself does not work. For this reason, it is necessary to perform the synchronization determination before the error correction, but since the synchronization code is error correction coded, there is a problem that the coded signal cannot guarantee the synchronization performance.

When synchronization is performed by a synchronization code having a low correlation, pseudo synchronization and loss of synchronization are repeated at the time of pulling in, the pull-in time increases, unstable sync pull-in occurs, and data reproduction cannot be expected.

Therefore, in the synchronization system of the present invention, not only a code having a high correlation is selected as a synchronization code, but also a code of a portion which is unique after the error correction encoding processing is independent of the preceding and following signals. , A code having autocorrelation is selected before and after the error correction coding process. This makes it possible to improve the synchronization performance.

In this case, in the demodulation processing in the receiving device, by detecting the unique known part, it is possible to determine the synchronization without performing the correction operation, and further by reflecting the demodulation operation, the demodulation operation can be performed. It becomes possible to stabilize. Of course, the number of sync codes is not limited to one as shown in FIG. 3, and the same applies to a plurality of cases.

Here, the autocorrelation will be described with an example.

As an example, when considering the correlation of an 8-bit code, the code is regarded as a cyclic code (one cycle is made when the code is shifted, and the back bit is brought to the front), and the bit sequence shifted with itself is compared. , Count the number of matching bits. As an example, an 11-bit 11101011 code string is shown in FIG.

In this case, the same bit is 4 out of 8 bits.
It becomes a bit, and the smaller this is, the more it can be determined that the synchronization is deviated (incorrect), and thus the possibility of false synchronization is reduced. Therefore, a bit string having a small number of matching bits in the bit sequence shifted by itself is preferable as the synchronization code.

The same operation is performed for all 8-1 = 7 bit shift amounts except for itself, the number of matching bits is counted, and the smaller number is regarded as a code having a high autocorrelation.

When the synchronous code 1B95h (16 bits) is convolutionally coded by the polynomials G133 and 171, the code becomes a XXXECD28h (32 bits) code.
However, in the convolutional encoding, some values are uncertain depending on the values of the data string before and after (concerning the above XXX portion). for that reason,
Only the unique ECD 28h (20 bits) portion is focused on, regardless of the preceding and succeeding codes.

Therefore, when the unique code ECD28h after the convolutional coding of 1B95h of the present invention is analyzed, when there is a 1,2,10,18,19 bit shift, the matching code is 8 bits, and other than that. It became 10 bits, and it was verified that there is a high correlation that is unlikely to cause false synchronization.

[0025]

As described above, according to the present invention, the performance of the synchronization process is deteriorated even when the sync code is combined with the error correction code when the sync signal is added to the main signal for digital transmission. It is possible to provide a receiving device that suppresses noise and that receives a digital transmission signal by a synchronization method that can satisfy both the synchronization processing performance and the error correction processing capability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a system using a synchronization method according to the present invention.

FIG. 2 is a diagram showing an example of a transmission format of the present invention.

FIG. 3 is a diagram showing an example of another transmission format of the present invention.

FIG. 4 is a diagram for explaining autocorrelation in the synchronization method of the present invention.

[Explanation of symbols]

11 ... Synchronous code multiplexing unit, 12 ... Error correction coding unit, 13
Modulation unit, 21 demodulation unit, 22 synchronization detection unit, 23 synchronization determination unit.

Claims (2)

[Claims] 1. A polynomial G133,1 which is a non-systematic code in which a synchronization code is added to a main signal and the synchronization code and the main signal are combined.
When a hexadecimal number 1B95h is used as a synchronization code when receiving a transmission signal by a synchronization method in which convolutional encoding is performed by 71, the 32 bits of the code after the convolutional encoding from the reception signal of the transmission signal. In the reception method, the ECD 28h of hexadecimal number is detected from the last 20 bits of the signal of 1. and the synchronization is determined based on the detection result. 2. A hexadecimal 1B as a sync code for the main signal.
A receiving device used for a transmission system which adds 95h and performs convolutional coding by combining polynomials G133 and 171 which are non-systematic codes by combining a synchronization code and a main signal, and which receives the transmission signal. Detecting means for detecting the hexadecimal ECD 28h from the last 20 bits of the 32-bit signal of the code after the convolutional encoding from the received transmission signal, and a synchronization determining means for determining synchronization based on the detection result of this detecting means. And a receiver.