JPH0964925A - Data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase transmission data capacity in the case of utilizing convolution coding/maximum likelihood decoding processing. SOLUTION: A multiplexer 13 of a transmitter multiplexes additional input data with synchronization data, the result is in time division multiplex processing with output data of a convolution coder 2 through switch circuits 14, 15, and a QPSK modulator 3 applies QPSK modulation to the resulting data and the modulated data are transmitted to a receiver. A QPSK demodulator 4 of the receiver demodulates the QPSK reception wave and a maximum likelihood decoder 5 obtains decoding output data. In this case, a synchronization data detector 17 detects synchronization data from the demodulation data, a timing generator 22 decides a separation timing and a data separator 18 provides an output of the additional data from the demodulated data separately. On the other hand, dummy data are added to the demodulated data in place of the additional data by the changeover control of switches 19, 20 and the result is given to the maximum likelihood decoder 5, by which characteristic deterioration is reduced in the case of maximum likelihood decoding.

Description

Detailed Description of the Invention

[0001]

The present invention is used in, for example, satellite / terrestrial communication / broadcasting systems, and particularly convolutional coding
The present invention relates to a data transmission system added with an error correction function by maximum likelihood decoding processing.

[0002]

2. Description of the Related Art Conventionally, in a communication system such as satellite broadcasting, a QPSK (four phase modulation) method has been adopted as a data transmission method. However, in a general QPSK method that does not include error correction, an error is likely to occur when the received signal is attenuated due to rainfall. Therefore, convolutional coding / maximum likelihood decoding usually improves the error rate by 3 to 5 dB. It is used after being designed.

FIG. 3 shows a coding rate of 1 in the conventional QPSK system.
2 shows a configuration of a data transmission system in which a convolutional coding of / 2 and a maximum likelihood decoding process are combined. In FIG. 3, in the transmitting device, the data input to the terminal 1 is encoded at a coding rate of 1/2.
The 1-bit input is converted into a 2-bit code by convolutionally coding the error correction code by inputting it to the convolutional encoder 2 of 1., and the QPSK modulator (MOD) 3 phase-modulates and outputs. In the receiving device, the QPSK received wave from the transmitting device is converted into 2-bit demodulated baseband data by the QPSK demodulator (DEM) 4, error correction is performed by the maximum likelihood decoder 5, and the decoded output data is output from the terminal 6. To get

However, in the conventional data transmission system as described above, the transmission bandwidth is QPS without error correction.
If it is the same as K, only half the information can be sent due to error correction.

[0005]

As described above, in the conventional data transmission system utilizing the convolutional coding / maximum likelihood decoding process, the error correction function is added, so that only half of the data amount that can be originally transmitted can be obtained. I can no longer send. An object of the present invention is to solve the above problems and to provide a data transmission system capable of increasing the transmission data capacity without widening the transmission bandwidth.

[0006]

DISCLOSURE OF THE INVENTION The present invention for solving the above problems is a convolutional encoder which adds an error correction code to input data and performs a convolutional encoding process to convert it into a plurality of bits of baseband data. A transmitter including a modulator that multiplexes and outputs a plurality of bits of data from an encoder, a demodulator that demodulates the modulated data from the transmitter, and a maximum likelihood decoding for the demodulated data of the demodulator. In a data transmission system including a receiving device including a maximum likelihood decoder for performing error correction on decoded data, the transmitting device includes a synchronous data generator for generating synchronous data, and a synchronous data generator for generating the synchronous data. A multiplexer that multiplexes the output synchronization data and additional data and distributes and outputs the multiplexed data according to the number of output bits of the convolutional encoder, and each bit output of this multiplexer. A time-division multiplexing means for time-division-multiplexing to the corresponding bit output of the convolutional encoder, wherein the receiving device is a synchronization data detector for detecting synchronization data from the demodulation output of the demodulation means; A timing generator that determines the data separation timing from the detection timing of the synchronous data detector, a data separator that separates additional data from the demodulation data based on the data separation timing determined by this timing generator, and the demodulation data And dummy data exchanging means for adding dummy data in place of the additional data and supplying the dummy data to the maximum likelihood decoder.

That is, in the data transmission system having the above structure, the transmitter multiplexes the additional data together with the synchronization data, and then time-divisionally multiplexes the convolutionally encoded data and outputs the modulated data.

On the other hand, in the receiving device, the synchronous data detector detects only the synchronous data added on the transmitting side,
In the timing generator, the detection timing of the synchronous data is used as the reference timing for determining the position of the additional data, and the actual separation timing is determined from this reference timing to control the data separator. This allows the data separator to separate and output the additional data that may have been input on the transmission side from the demodulated data.

On the other hand, since the data added on the transmission side is unnecessary for the maximum likelihood decoder, dummy data is added instead of the additional data. As a result, it is possible to reduce characteristic deterioration in the original data decoding of the maximum likelihood decoder.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows the configuration of a data transmission system according to an embodiment of the present invention. The convolutional encoder 2 and the QPS of the transmitter
The K modulator 3, the QPSK demodulator 4 and the maximum likelihood decoder 5 of the receiving device are circuits having the same functions as those of the conventional system shown in FIG. In this embodiment, the convolutional encoder 2 and the QPS
It is characterized in that the following circuit is added between the K modulator 3 and between the QPSK demodulator 4 and the maximum likelihood decoder 5.

First, in the transmitter, the terminal 11 is supplied with additional data independent of the input data of the terminal 1. This additional data is supplied to the multiplexing circuit 13 together with the synchronization data generated by the synchronization data generator 12 based on the timing signal. The multiplexer 13 multiplexes the additional data and the synchronous data based on the timing signal and distributes and outputs them to two systems. Each distributed output is supplied to one input terminal of each of the switch circuits 14 and 15.

The switch circuits 14 and 15 input the output data of the convolutional encoder 2 to the other input terminals, and selectively lead one of the input data to the QPSK modulator 3 according to the timing signal. The synchronous data generator 1
2, the timing signal supplied to the multiplexer 13 and the switch circuits 14 and 15 is generated by the timing generator 16.

On the other hand, in the receiving apparatus, the two demodulated data obtained by the QPSK demodulator 4 are both supplied to the synchronous data detector 17 and the data separator 18, and are input to one input ends of the switch circuits 19 and 20, respectively. Supplied. Each of the switch circuits 19 and 20 inputs the dummy data output from the dummy data generator 21 to the other input terminal,
One of the input data is selectively derived to the maximum likelihood decoder 5 according to the timing signal.

The synchronous data detector 17 detects the synchronous data from the demodulated data of the two systems of the QPSK demodulator 4, and the detected synchronous data is supplied to the timing generator 22. The timing generator 22 generates a timing signal for separating data and a timing signal for switching switches from the synchronous data.

The data separator 18 separates and extracts additional data from the demodulated data of the two systems of the QPSK demodulator 4 according to the timing signal, and the additional data obtained here is output from the terminal 23.

The operation of the above arrangement will be described below. First, in the transmitter, the additional input data is multiplexed with the synchronization data by the multiplexer 13, and the switch circuit 1
4, and 15 and time-division-multiplexed with the convolutionally coded data and sent to the QPSK modulator 3. Therefore, from the QPSK modulator 3, the additional input data and the synchronization data are QPSK-modulated and transmitted together with the convolutionally encoded data.

On the other hand, in the receiving device, the demodulated baseband data demodulated by the QPSK demodulator 4 is the switch 1
It is sent to the maximum likelihood decoder 5 via 9 and 20. At this time, the synchronization data detector 17 detects only the synchronization data added on the transmission side and supplies it to the timing generator 22.

The timing generator 22 uses the detection timing of the synchronous data as the reference timing for determining the position of the additional data, determines the actual separation timing from this reference timing, and sends it to the data separator 18. As a result, the data separator 18 separates the additional data which may have been input on the transmission side, from the demodulated baseband data.
The separated additional data is output from the terminal 23.

On the other hand, the data added on the transmitting side is unnecessary for the maximum likelihood decoder 5. So switch 1
By adding the dummy data instead of the additional data by 9 and 20, the characteristic deterioration in the original data decoding of the maximum likelihood decoder 5 is reduced.

Therefore, the data transmission system having the above configuration can increase the transmission data capacity without increasing the bandwidth. Further, if the ratio of the amount of information of the additional data is set to be small, the main line data can be reproduced in the conventional system of FIG. 3 without any problem. It becomes possible.

In the above embodiment, the case of the QPSK transmission system by the convolutional coding / maximum likelihood decoding of the coding rate 1/2 has been described, but as shown in FIG. 2, the convolutional code of the coding rate 2/3. -Phase PSK with coding / maximum likelihood decoding
It is also applicable to transmission systems.

In FIG. 2, the transmitter 31 has a terminal 31.
The convolutional encoder 32 converts the data input to a and 31b.
2 by inputting to and convolutionally coding the error correction code
The bit input is converted into a 3-bit code, phase-modulated by an 8-phase PSK modulator (MOD) 33, and transmitted. In the receiving device, the 8-phase PSK received wave from the transmitting device is converted into 3-bit demodulated baseband data by the 8-phase PSK demodulator (DEM) 34, error correction is performed by the maximum likelihood decoder 35, and the terminal 36a, Decoded output data is obtained from 36b.

In the case of this system, in the transmitter,
Based on the timing signal generated by the timing generator 47, the additional input data supplied to the terminal 41 is added to the synchronization data generated by the synchronization data generator 42 and the multiplexer 43.
Are multiplexed by the switch circuit 44,
45 and 46 time-division-multiplexed with the convolutionally encoded data and send it to the 8-phase PSK modulator 33. Therefore, 8-phase PSK
From the modulator 33, additional input data and synchronization data are 8-phase PSK-modulated and transmitted together with the convolutionally encoded data.

On the other hand, in the receiving device, the 3-bit demodulated baseband data demodulated by the 8-phase PSK demodulator 34 is passed through the switches 50, 51 and 52 to the maximum likelihood decoder 35.
However, at this time, the synchronous data detector 48 detects only the synchronous data added on the transmitting side and supplies it to the timing generator 54.

The timing generator 54 uses the detection timing of the synchronous data as the reference timing for determining the position of the additional data, determines the actual separation timing from this reference timing, and sends it to the data separator 49. As a result, the data separator 49 separates the additional data that may have been input on the transmission side from the demodulated baseband data.
The separated additional data is output from the terminal 55.

On the other hand, the data added on the transmitting side is unnecessary for the maximum likelihood decoder 35. So switch 5
By adding the dummy data generated by the dummy data generator 53 in place of the additional data by 0, 51, 52, the characteristic deterioration in the original data decoding of the maximum likelihood decoder 35 is reduced. The decrypted data is the terminals 36a and 36b.
Output.

Therefore, even in the data transmission system having the above configuration, the data transmission capacity can be increased without increasing the bandwidth. Further, it is needless to say that the present invention can be applied to a multi-phase PSK transmission system or a system using another data multiplex transmission method.

[0028]

As described above, according to the present invention, the data transmission capacity can be increased without widening the transmission bandwidth.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention in which a coding rate of 1 /
FIG. 3 is a block diagram showing the configuration of a QPSK transmission system by 2 convolutional coding / maximum likelihood decoding.

FIG. 2 shows another embodiment of the present invention as a coding rate 2
FIG. 3 is a block diagram showing the configuration of an 8-phase PSK transmission system based on 3/3 convolutional coding / maximum likelihood decoding.

FIG. 3 is a block diagram showing a configuration of a conventional QPSK transmission system by convolutional coding / maximum likelihood decoding with a coding rate of 1/2.

[Explanation of symbols]

 1 ... Data input terminal 2 ... Code rate 1/2 convolutional encoder 3 ... QPSK modulator 4 ... QPSK demodulator 5 ... Maximum likelihood decoder 6 ... Data output terminal 11 ... Additional data input terminal 12 ... Synchronous data Generator 13 ... Multiplexer 14, 15 ... Switch circuit 16 ... Timing generator 17 ... Synchronous data detector 18 ... Data separator 19, 20 ... Switch circuit 21 ... Dummy data generator 22 ... Timing generator 23 ... Additional data Output terminals 31a, 31b ... Data input terminal 32 ... Coding rate 2/3 convolutional encoder 33 ... 8-phase PSK modulator 34 ... 8-phase PSK demodulator 35 ... Maximum likelihood decoder 36 ... Data output terminal 41 ... Addition Data input terminal 42 ... Synchronous data generator 43 ... Multiplexer 44, 45, 46 ... Switch circuit 47 ... Timing generator 48 ... Synchronous data detector 9 ... data separator 50, 51, 52 ... switching circuit 53 ... dummy data generator 54 ... timing generator 55 ... additional data output terminal

Claims (4)

[Claims] 1. A convolutional encoder that adds an error correction code to input data, performs convolutional coding processing, and converts the input data into a plurality of bits of baseband data, and multiplexes and modulates data of a plurality of bits of the convolutional encoder. Transmitting device having modulating means for outputting, demodulating means for demodulating modulated data from this transmitting device, maximum likelihood decoding for performing maximum likelihood decoding on demodulated data of this demodulating means to perform error correction on the decoded data In a data transmission system including a receiving device including a synchronizing device, the transmitting device multiplexes a synchronizing data generator that generates synchronizing data, and the synchronizing data and additional data output from the synchronizing data generator. A multiplexer for distributing and outputting the number of output bits of the convolutional encoder and each bit output of the multiplexer corresponding to the bit output of the convolutional encoder. And a time division multiplexing means for time division multiplexing, wherein the receiving device detects a synchronization data from the demodulation output of the demodulation means, and a data separation timing from the detection timing of the synchronization data detector. , A data separator for separating additional data from the demodulated data based on the data separation timing determined by the timing generator, and dummy data for the demodulated data instead of the additional data. A data transmission system, further comprising: a dummy data exchange unit which additionally supplies the data to the maximum likelihood decoder. 2. The data transfer system according to claim 1, wherein the modulation means and the demodulation means use a polyphase modulation method. 3. The data transmission system according to claim 1, wherein the modulation means and the demodulation means use a 4-phase phase modulation method. 4. The data transmission system according to claim 1, wherein the modulation means and the demodulation means use an 8-phase phase modulation method.