JPH0993295A - Code modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the error correction capability of coding modulation under a burst error environment such as fading. SOLUTION: A transmission data series 2 is distributed into two data series by a serial/parallel converter 3 and a data series is given to a convolutioned coder 4 and a Golay (1, 8, 6) coder 5. The convolution coder 4 and the Golay coder 5 respectively apply convolutional coder and Golay coding with a coding rate of 1/3 to the received data series and the result is given to a signal point mapping circuit 6. The signal point mapping circuit 6 arranges signal points on diagonal lines with respect to 0, 1 of convolutional coder output signals to maximize the Euclid distance and arranges signal points so as to select either of the two diagonal lines on the QPSK signal plane with respect to 0, 1 of the output of the golay coder 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding / modulating apparatus used for digital radio communication such as a car telephone and a mobile telephone.

[0002]

2. Description of the Related Art Coded modulation is a technique for improving error rate characteristics by integrating error correction coding technology and digital modulation / demodulation technology. Trellis coded modulation is a method in which a multi-valued modulation method and a convolutional code are combined and decoded by a Viterbi algorithm. In this method, the Euclidean distance between signal points is defined as the minimum free distance between codewords, and the maximum Euclidean distance between signal points is defined, in order to prevent the deterioration of transmission quality due to the decrease of signal point distance due to multi-valued. The signal-to-noise characteristics are improved by applying an error-correcting code that devises the signal point arrangement and data decision method so that the distance becomes equivalently large.

FIG. 5 shows a block diagram of an encoder in a conventional coded modulation system. A1, a2, a3 of the input data 17
Is coded at a coding rate of 3/4, and c1, c2,
The data 18 of c3 and c4 is output. A1 and a2 are encoded by a convolutional encoder composed of a three-stage shift register 19, and a3 is output as it is as c4 without adding redundancy. FIG. 6 shows the signal point arrangement of code words by the encoder of FIG. The number in parentheses of the signal point is (c4
, C3, c2, c1). To maximize the Euclidean distance between signal points by either 0 or 1 of c4, which has no redundancy and is not resistant to transmission path errors (for example, D30
And D31). On the receiving side, decoding is performed by the Viterbi algorithm after demodulating and determining the receiving point on the signal plane. As the branch metric, the Euclidean distance between the reception point and the transmission candidate point is used. Here, the path on the trellis diagram corresponding to the case where the signal point D30 is the transmission candidate is the same as the path for the signal point D31, and C4
Is different only when the value of is 0 or 1. This is called a parallel path. The parallel path is selected according to the distance between D30 and the receiving point and the distance between D31 and the receiving point, and the smaller distance is selected. By selecting the parallel path, it is remembered whether c4 was selected as 1 or 0 in the path, and at the same time when the decoding processing of a1 and a2 is performed in the traceback processing,
Decoding of a3 is performed by the selection information of c4 stored at each time of the final pass.

[0004]

However, the convolutional code used in the conventional trellis coded modulation has a high correction capability for random errors but a low correction capability for burst errors. Therefore, in a propagation environment in mobile communication, trellis coded modulation has a problem that the error correction capability is low with respect to fading, particularly burst errors due to slow fading. On the other hand, there is a method of temporally distributing error positions by interleaving, but it is not possible to set a large interleaving size in a system such as voice transmission in which tolerance for delay is small.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a coding / modulating apparatus having a high capability of correcting burst errors in a mobile communication environment or the like.

[0006]

In order to achieve the above-mentioned object, the present invention provides a coding / modulating device provided in a transmitter of a communication device for wirelessly transmitting information in a serial / parallel manner with respect to transmission data. A serial / parallel converter that performs conversion, a convolutional encoder that performs convolutional coding on one data string after serial / parallel conversion, and a block that performs block coding on the other data string after serial / parallel conversion An encoder, a signal point mapping circuit for arranging signal points for the code words of the outputs of both encoders so that the minimum Euclidean distance between the signal points on the signal plane is maximized, and the signal point mapping circuit is arranged. It is composed of a modulator that modulates the signal at the signal points, and is used for the signal data series that provides a parallel path in the Viterbi decoding processing of coded modulation. Te, and summarized in that the so performs encoding using a high block code having a burst error correcting capability as compared with the convolutional code.

According to the present invention, the above configuration maximizes the Euclidean distance of a signal point with respect to a signal after convolutional coding, and compares it with a convolutional code with respect to a signal data sequence that gives a parallel path in the Viterbi decoding process of coded modulation. By performing the encoding using the block code having the high burst error correction capability, the error correction capability can be enhanced even in the burst error environment.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the configuration of a coding and modulating apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a transmitter, 2 is a transmission data series, and this transmission data series 2 is input to a serial / parallel converter 3. The output of the serial / parallel converter 3 is a convolutional encoder 4 and a Golay (18,
6) The encoder 5 encodes each at a coding rate of 1/3, and inputs the signal point mapping circuit 6. The output of the signal point mapping circuit 6 is interleaved by the interleave circuit 7 and is further input to the modulator 8. The output of the modulator 8 is transmitted from the transmitting antenna 9.

Reference numeral 15 denotes a receiver. In this receiver 15, the signal received by the receiving antenna 10 is demodulated by the demodulator 11.
Is input to The output of the demodulator 11 passes through the deinterleave circuit 12, the metric operation circuit 13, and the Viterbi decoder 14, and the reception data series 16 is obtained. And the transmitter 1
The receiver 15 and the receiver 15 together constitute a communication device that wirelessly transmits information.

The operation of the communication device having the above configuration will be described below. In the transmitter 1, the transmission data series 2 is input to the serial / parallel converter 3. The serial / parallel converter 3 divides the data series into two data series and inputs the respective data series to the convolutional encoder 4 and the Golay (18,6) encoder 5. In the convolutional encoder 4 and the Golay encoder 5, the input data series is subjected to convolutional coding and Golay coding (one type of block coding) with a coding rate of 1/3, and both are input to the signal point mapping circuit 6. To do. The Golay (18,6) code is a code that outputs 18 bits (6 bits input + 12 bits check) for a 6-bit input. The signal point mapping circuit 6 determines the signal point arrangement for the input 1 bit of the convolutional code and 1 bit of the Golay code as shown in FIG. In this embodiment, the modulation method is QPSK.
Method is used. From FIG. 2, the Euclidean distance is maximized by arranging the signal points of 0 and 1 of the signal on the output side of the convolutional encoder on the diagonal line. For the signals 0 and 1 of the output of the Golay encoder, it is determined which one of the two diagonal positions existing on the QPSK signal plane is selected. The interleave circuit 7 interleaves the in-phase component (I) and the quadrature component (Q) of the transmission signal point as a pair, and outputs them to the modulator 8. Modulator 8
Then, QPSK modulation is performed by the signal point arrangement determined in the signal point mapping circuit 6, and the output of the modulator 8 is transmitted from the transmission antenna.

In the receiver 15, the signal received by the receiving antenna 10 is input to the QPSK demodulator 11. In the demodulator 11, the received signal is separated into I and Q components of the carrier wave, extracted as a soft decision value for each received bit, and output to the deinterleave circuit 12. The deinterleave circuit 12 performs deinterleave as an I, Q pair and inputs it to the metric calculation circuit 13. The operations of the metric operation circuit 13 and the Viterbi decoder 14 will be described below. In this embodiment, a convolutional code with a constraint length of 7 is used as the convolutional code. FIG. 3 shows a trellis diagram in Viterbi decoding, and FIG. 4 shows a branch metric giving method. In FIG. 3A, Golay codeword (G0
, G63) as a received codeword, and for a path with a 6-branch length (codeword length of Golay (18,6)), the path with the highest likelihood to reach each state and its path metric are G = G0 ~ G63 is calculated for each.

Here, how to obtain the branch metric will be described below. As shown in FIG. 4, when it is assumed that the Golay coded bits are 0, the one having the smaller Euclidean distance between the received signal point and (0,0) and (1,0) is the Golay coded bit. Assuming that, the smaller one of the Euclidean distances between the received signal point and (0,1) and (1,1) is given as a branch metric. From the above results, for each path leading to each state, which Golay code is used as the received codeword to obtain the highest likelihood when the metric assigning method is given, the path at this time,
The Golay codeword and path metric are stored as shown in FIG. The above processing is repeated until the end of the predetermined convolutional code, and further, traceback is performed from the end of the convolutional code as shown in FIG. 3C, and the data on the convolutional encoder side is decoded from the path transition. Further, the Golay encoder side data is decoded by the Golay code word number (any of G0 to G63) stored in the selected path to obtain the received data sequence 16.

By performing the above processing, maximum likelihood decoding is realized. Here, since the Euclidean distance of the signal point by the signal of the convolutional code is maximized, the error correction capability is enhanced by this effect in the decoding of the convolutional code. In addition, since the redundancy of the block code is provided in the selection of the parallel path, the error correction capability with respect to the burst error is high. Further, not only the convolutional code but also the Golay code is decoded by soft decision, which improves the coding gain.

Further, in this embodiment, since the error characteristic of the convolutional code in which the distance between signal points is expanded or the signal distance is expanded is good, a data sequence having a high required transmission quality is used instead of the serial / parallel converter. A data selection circuit for inputting a data sequence having a relatively low required transmission quality to a block encoder is used to easily realize data transmission having different required quality.

[0015]

As is apparent from the above embodiments, according to the present invention, the signal data which maximizes the Euclidean distance of the signal point with respect to the signal after the convolutional coding and gives a parallel path in the Viterbi decoding process of the coded modulation. By performing coding on a sequence using a block code having a higher burst error correction capability than a convolutional code, a coding and modulation device having a high error correction capability even in a burst error environment is provided. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a code modulation circuit according to an embodiment of the present invention.

FIG. 2 is a signal point arrangement diagram according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram of trellis transition in the decoding algorithm according to the embodiment of the present invention.

FIG. 4 is a conceptual diagram of branch metrics in the embodiment of the present invention.

FIG. 5 is a block diagram showing an encoder of an encoding / modulating apparatus in a conventional example.

FIG. 6 is a signal point arrangement diagram in a conventional example.

[Explanation of symbols]

 1 Transmitter 2 Transmission Data Sequence 3 Serial / Parallel Converter 4 Convolutional Encoder 5 Golay (18,6) Encoder 6 Signal Point Mapping Circuit 7 Interleave Circuit 8 Modulator 9 Transmit Antenna 10 Receive Antenna 11 Demodulator 12 Deinterleave Circuit 13 metric calculation circuit 14 Viterbi decoder 15 receiver 16 decoded data sequence

Claims (4)

[Claims] 1. A transmitter and a receiver for wirelessly transmitting information, wherein the transmitter is a serial / parallel converter for performing serial / parallel conversion on transmission data, and one of serial / parallel conversion. A convolutional encoder that performs convolutional coding on the data sequence of, a block encoder that performs block coding on the other data sequence after serial / parallel conversion, and a minimum Euclidean distance of the signal points on the signal plane is the maximum. A signal point mapping circuit for arranging signal points for the code words of both encoder outputs,
An encoding / modulating apparatus comprising: a modulator that modulates a signal by a signal point arranged by the signal point mapping circuit. 2. A block encoder having the same coding rate as a convolutional code is provided as a block encoder, and a QPS is provided as a modulator.
A modulator using a K (4-phase phase shift keying) system is provided, and 1 is selected from 2 points of diagonal positions existing on the signal plane of QPSK for 0 and 1 of the block encoder output.
2. The coding and modulation apparatus according to claim 1, further comprising a signal point mapping circuit that selects a set and further arranges signal points on any one of diagonals with respect to 0 and 1 of the output of the convolutional encoder. 3. A data selection circuit for inputting a data sequence having a high required transmission quality to a convolutional encoder and inputting a data sequence having a relatively low required transmission quality to a block encoder instead of the serial / parallel converter. The coded modulation device according to claim 1. 4. A data selection circuit for inputting a data sequence having a high required transmission quality to a convolutional encoder and inputting a data sequence having a relatively low required transmission quality to a block encoder instead of the serial / parallel converter. The coded modulation device according to claim 2.