JPH07183862A - Error correcting method of frequency division multiplexing transmission and transmission system using same - Google Patents

Abstract

PURPOSE:To realize an error correcting method where the speed-up of transmission speed is easy and the degradation of the error ratio of a frequency selective phasing is small, in an FDM transmission system. CONSTITUTION:A transmitter 301 is composed of (n) error correction encoders 101-1 to 101-n (n is >=2) performing an error correction encoding for transmission data, a mapping circuit 102 outputting m of data arranged so as to disperse each of n encoded data sequence on a frequency axis or a time axis and an FDM modulator 103 outputting signal where m of data is modulated into each of m carrier waves and is multiplexed. Therefore, plural error correction encoders 101-1 to 101-n and a decoder are provided, the application of high transmission speed to a system is easy. Because the burst error by a selective fading is effectively dispersed by a mapping means, the reliability of decoded data is improved. When a user receives only part of data in a multiconnection and a broadcasting system, the miniaturization of a receiver and low power consumption is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error correction method in frequency division multiplex transmission for communicating or broadcasting digital data using a plurality of carrier waves of different frequencies, and a transmission system using the same.

[0002]

2. Description of the Related Art A method of transmitting digital data using a plurality of carriers of different frequencies is frequency division multiplexing (Fr
Frequency Division Multiplexing (FDM) Transmission method. Orthogonal frequency division multiplexing (Orth) in the FDM transmission system, especially when the carrier waves have mutually orthogonal frequencies.
Oganl Frequency Division Multiplexing (OFDM) transmission method. FIG. 24 shows a conceptual diagram of signal transmission in the FDM transmission system. In FIG. 24, the frequencies of m carriers are respectively f ₁ , f ₂ , ..., F _m, and the modulation symbols transmitted at time t are S ₁ (t), S ₂ (t),
,, S _m (t). The modulation symbol on each carrier is a symbol modulated by QPSK, 8PSK, or the like.

A general error correction method of the FDM transmission system is, for example, "Le Flocu et al.," Digital Sound Broa.
dcasting to Mobile receivers ”, IEEE TransactionCo
nsumer Electronics, Vol.35, Nomber 3, August 1989,
pp.493-530 ". FIG. 25 shows a schematic block diagram of the error correction method shown in this document. In FIG. 25A, in the transmitter 1, the data to be transmitted is input to the error correction encoder 2 at 168 kbps. The error correction encoder 2 encodes the input data with a convolutional code having a coding rate of 1/2 and outputs the encoded data at 336 kbps. The encoded data is interleaved by the interleaver 3 for 384 msec (129,024 bits), converted into a parallel signal of 894 bits by the serial / parallel conversion circuit 4, and then converted into 448 orthogonal carrier waves by the OFDM modulator 5. It is QPSK-modulated and transmitted through the communication path 6. Further, in FIG. 25B, the receiver 10 converts the received signal into the OFDM demodulator 1
The data is demodulated to 896-bit data by 1 and is de-interleaved for 384 msec (129,024 bits) by the dender lover 13 and is then error-corrected and decoded by the Viterbi decoder 14. With this error correction method, 44
One error correction encoder, error correction decoder, interleaver and deinterleaver are shared for all eight carriers.

As another error correction method of the FDM transmission system, for example, there is a system shown in "Orthogonal Frequency Division Multiplexing Digital Signal Transmission System and Coding Modulation Device and Demodulation Device Used Therefor" of Japanese Patent Laid-Open No. 5-219006. . In this document, as an error correction method, a trellis coded modulation method is used in which an error correction code and signal point mapping during modulation are performed together. FIG. 26 shows a schematic block diagram of the system shown in this document. In FIG. 26A, in the transmitter 1A, the data to be transmitted is encoded by one trellis encoder 2A. The data encoded by the trellis encoder 2A is interleaved by one interleaver 3, converted into a parallel signal by the serial / parallel conversion circuit 4, and then 8PSK or the like is applied to a plurality of orthogonal carrier waves by the OFDM modulator 5. Is modulated and transmitted. In addition, FIG.
In (b), the receiver 10A outputs the received signal as O
After demodulation by the FDM modulator 11 and parallel / serial conversion by the parallel / serial conversion circuit 12, deinterleaving is performed by one deinterleaver 13 and error correction decoding is performed by using one trellis encoder 14A. Also in this error correction system, one error correction encoder, error correction decoder, interleaver, and deinterleaver are shared for all carriers.

On the other hand, the method shown in the same document as a method considered from the prior art is a method of independently performing error correction coding on data transmitted on each carrier. FIG. 27 shows a schematic configuration diagram of this system. As shown in FIG. 27, in this system, the coding circuit 2B is provided with a plurality of trellis encoders and trellis decoders respectively corresponding to the number of carrier waves (m) in the error correction encoder and the error correction decoder. (FIG. 27A) and the decoding circuit 1
4B (FIG. 27 (b)), the circuit scale becomes large.

By the way, when the FDM transmission system is used in a transmission line in which frequency selective fading occurs, such as mobile communication, temporally continuous errors occur in data transmitted on a specific carrier. As shown in FIG. 28, an error caused by frequency-selective fading is a temporally continuous error (burst error) in a plurality of adjacent carriers. Generally, an error correction code such as a trellis code or a convolutional code is a burst error. Therefore, if the error correction method as shown in FIG. 27 is used under such a condition, the error rate after decoding of the data transmitted by the carrier wave that undergoes fading becomes significantly worse, and the overall It will deteriorate the reliability.

On the other hand, in the error correction system shown in FIGS. 25 and 26, the error rate can be suppressed to a low level because the burst error is spread by using the interleaver, but it is dense in both the time axis direction and the frequency axis direction. Since it is necessary to spread the burst error, the memory capacity required for one interleaver becomes large. Since the interleaver is usually composed of RAM, there is a problem that it is difficult to apply it to a high speed system if the memory capacity is large. In addition, these error correction methods have only one set of error correction encoder and decoder for all carriers, and therefore it is necessary to speed up these circuits. However, low circuit scale and low power consumption are required. Under these conditions, it is difficult to speed up these circuits. Especially when a Viterbi decoder is used as the error correction decoder, the processing speed of the Viterbi decoder is limited, so that it cannot be applied to a higher speed system.

Further, when the conventional error correction method shown in FIGS. 25 and 26 is also used, even if the receiver wants to receive only a part of the transmitted data, all the data including unnecessary data is received. There is a problem that the power consumption of the receiver becomes large because the necessary data cannot be obtained only after de-interleaving and error correction decoding.

[0009]

As described above, in the conventional error correction method of the frequency division multiplex transmission method, there are a method having an error correction encoder and a decoder as many as the number of carrier waves, and a method having all the carrier waves. On the other hand, there is a system having only one set of an error correction encoder and a decoder. The error correction encoder and decoder, which have the same number of carriers as the number of carriers, cannot sufficiently correct burst errors on a specific carrier when used in a channel where frequency selective fading occurs, so the reliability of the decoded data There was a problem of deterioration. On the other hand, a system having only one set of an error correction encoder and a decoder requires an interleaver with a large memory capacity and a high speed error correction decoder in order to correct a burst error due to frequency selective fading. There was a problem that it was difficult to apply to the system. Further, even when the receiver wants to receive only a part of the data, all the data must be de-interleaved and error-correction-decoded, resulting in a problem that the power consumption of the receiver increases.

The present invention has been made in view of the above problems, and is applied to a system in which the deterioration of the error rate is small even if frequency selective fading occurs in the frequency division multiplex transmission system and the transmission rate is high. It is an object of the present invention to provide an error correction method capable of Further, when the receiver needs only a part of the transmitted data, an error correction method capable of reducing the power consumption of the receiver by performing error correction decoding and de-interleaving of only the part corresponding to the data. The purpose is to provide.

[0011]

A first error correction method of the present invention is a method of frequency division multiplex transmission in which a digital signal output from one or a plurality of information sources is transmitted using a plurality of carriers of different frequencies. In the error correction method, on the transmission side, a step of performing error correction coding on the transmission data divided into a plurality of groups for each group, and a plurality of data transmitted in the same time by the same group of error correction coded data are transmitted. Mapping the data to multiple non-adjacent frequency carriers or to some non-adjacent frequency carriers.

The second error correction coding method of the present invention is
In an error correction method of frequency division multiplex transmission, in which a digital signal output from one or more information sources is transmitted by using carrier waves of different frequencies, in the transmission side, transmission data divided into a plurality of groups is divided into groups. Error-correction-encoding to a plurality of data that are transmitted on a carrier of the same frequency in the same group of error-correction-encoded data. Mapping the signals to a set of signals that are not continuous in time.

In the error correction method described in any of the above, it is desirable that the receiving side divides the demodulated data into a plurality of groups, and correct and decode at least one error of the divided groups. Steps to
You may comprise so that it may have.

In the error correction method described in any of the above, there is a step of interleaving corresponding to each error correction coding step, and each interleaving step is output in each error correction coding step. The encoded data to be input may be input, the order of the encoded data may be changed, and the encoded data may be output so that the data is mapped in the mapping step.

The transmission system of the present invention is a communication system in which a digital signal is transmitted from one transmitter to a plurality of receivers by using a plurality of carriers of different frequencies, and the transmitters are divided into a plurality of groups. A plurality of error correction coding means for performing error correction coding for each and a plurality of data transmitted in the same time by the same group of error-correction-coded data are stored in a plurality of carrier waves or one carrier whose frequencies are not adjacent to each other. A means in which all signals are not continuous in time, or means for mapping to multiple carriers whose frequencies are not adjacent to each other, or multiple data transmitted in the same group of error-correction-encoded data on the same carrier And / or at least one of the means for mapping to a set of signals in which some signals are not continuous in time. With obtaining, each receiving station is characterized in further comprising means for dividing the demodulated data into a plurality of groups, and means for error correction encoding at least one of the divided groups.

[0016]

In the error correction method of the present invention, the data to be transmitted is divided into a plurality of groups for error correction coding.
Each error correction encoder and decoder need only operate at a low speed, and can be easily applied to a system having a high transmission rate. Further, since the data encoded by one error correction encoder in the mapping step is distributed and transmitted in the frequency axis direction and the time axis direction, the deterioration of the error rate due to the selective fading is small. In addition, since error correction coding is performed independently for each group and interleaving is applied, when only some data is received, it is sufficient to have only an error correction decoder and deinterleaver corresponding to that data. It is possible to reduce the size and power consumption.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an error correction method of the present invention and a transmission system using the same will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. The data transmitted in FIG. 1A is divided into n groups 200-1, 200-2, ..., 200-n and input to the transmitter 301. At the transmitter,
As shown in (b), n error correction encoders 101-1,
Input data of each group is error-correction coded by 101-2, ..., 101-n. Error correction coded data 201-1, 20
1-2, ..., 201-n are input to the mapping circuit 102,
Signals are replaced based on a rule described later, and m pieces of parallel data 202-1, 202-2, ..., 202-m are output. These data are input to the FDM modulator 103, modulated on each of the m carriers by BPSK, etc., and the multiplexed FDM signal 203 is output from the transmitter to the communication path 104.
On the other hand, the received signal 204 is input to the receiver 302. In the receiver 302, the received signal 204 is m by the FDM demodulator 105.
Demodulated into parallel data 205-1, 205-2, ..., 205-m, and the demapping circuit 106 demodulates n groups 206-1,
Returned to 206-2, ..., 206-n. The data of each group is input to n error correction decoders 107-1, 107-2, ..., 107-n, respectively, and the error-corrected decoded data 207-1, 20-
7-2, ..., 207-n are output from the receiver.

In FIG. 1A, the mapping circuit 102
Then, the data output from n error correction encoders is replaced with m parallel data according to the rule shown in FIG. FIG. 2 is a conceptual diagram showing the operation of the mapping circuit when n = 5 and m = 22. In FIG. 1, m parallel data 20 output from the mapping circuit 102.
2-1, 202-2, ..., 202-m are the FDs at each time shown in FIG.
It corresponds to each of the m carriers of the M signal. here,
If each carrier is modulated with BPSK, 1-bit encoded data is assigned to each modulated signal. Now
A mapping circuit 10 in which a set of data encoded by the error correction encoder 101-i (i = 1, 2, ..., N) is C _i.
In 2, the plurality of data encoded by the same error correction encoder and transmitted at the same time are mapped to carriers whose frequencies are not adjacent to each other. In addition, a plurality of pieces of data encoded by the same error correction encoder and transmitted on the same carrier are mapped to signals that are not continuous in time. For example, as shown in FIG. 2, the data C ₁ encoded by the error correction encoder 101-1 is
Are mapped so that they are not transmitted on carriers of adjacent frequencies at any time, and are not transmitted on consecutive times at any carrier.

When frequency selective fading occurs when the FDM transmission system is used, errors occur in bursts on the frequency axis and the time axis as shown in FIG. For this reason, in the conventional error correction method using a plurality of error correction encoders as shown in FIG. 26, errors on the frequency axis cannot be dispersed, and the error rate of data after decoding increases. On the other hand, the error correction system of the present invention uses a plurality of error correction encoders, but the data encoded by each encoder is distributed and transmitted on the frequency axis or the time axis. There is an effect that a burst error does not occur and an error is easily corrected correctly in each error correction decoder.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the present invention. In FIG. 3A, n groups of data are input to the transmitter 303, and n error correction encoders are input.
Error correction coding is performed with 101-1, 101-2, ..., 101-n.
The error-correction-encoded data of n groups are input to the n interleavers 108-1, 108-2, ..., 108-n, and the order is changed, and then input to the mapping circuit 102. In the mapping circuit, signals are replaced as in the first embodiment, and m pieces of parallel data are output. These data are input to the FDM modulator 103, modulated into m carrier waves, and the multiplexed FDM signal is output to the communication path 104. On the other hand, the received signal is input to the receiver 304. In the receiver 304, as shown in FIG.
The demodulator 105 demodulates the received signal into m pieces of parallel data, and the demapping circuit 106 returns them to n groups. The data of n groups includes n deinterleavers 10
After being input to 9-1, 109-2, ..., 109-n and returned to the original order, n error correction decoders 107-1, 107-2 ,.
It is input to each 7-n and the decoded data is output from the receiver.

In FIG. 3, n interleavers and deinterleavers are used to change the order of data encoded by one error correction encoder. The mapping circuit 102 performs mapping so that the data output from one encoder is dispersed on the frequency axis and the time axis as shown in FIG. 2, but in this way, interleaving is performed within each encoded sequence. By applying this, deterioration of the decoding error rate can be prevented even if a longer burst error occurs. In the conventional error correction methods shown in FIG. 25 and FIG. 26, the burst error is diffused by using interleaving. However, these methods have only one error correction encoder / decoder, and the frequency is not used on the communication path. Since it is necessary to spread errors occurring in a burst on both the axis and the time axis by a single interleaver, an interleaver with a large memory amount is required. On the other hand, the interleaver of the present invention is
Since the burst error is already distributed to each coded sequence by the mapping circuit, the interleaver of each sequence can be a small memory amount. Interleaver is usually RA
Since the RAM configured by M and having a small memory amount has a shorter access time, the error correction method of the present invention can be faster than the conventional error correction method.

FIG. 4 is a schematic block diagram showing the third embodiment of the present invention. In the transmitter 305 of FIG. 4A, the data output from the information source 110 is divided into two groups in the serial / parallel conversion circuit 111. These data are error correction encoders 112-1 and 112-1, respectively.
Error correction coded by 112-2, interleaver 113-1, 11
After being interleaved in 3-2, they are input to the mapping circuit 114. The mapping circuit 114 replaces the signals as shown in FIG. 5 and outputs m pieces of parallel data. These data are input to the FDM modulator 103, and m
The FDM signal that has been modulated into individual carrier waves and multiplexed is output to the communication path 104. On the other hand, the received signal is input to the receiver 306 of FIG. In the receiver 306, the FDM demodulator 105 demodulates the received signal into m pieces of parallel data, and the demapping circuit 115 returns them to two groups. These data are deinterleaver 116-1, 116-2
Error correction decoder 11
The data is input to 7-1 and 117-2, converted into serial data by the parallel / serial conversion circuit 118, and then passed to the reception purpose 119.

In this embodiment, if all the data output from the information source have the same conditions regarding the required reliability and the allowable delay time, the two error correction encoders 11 are used.
2-1 and 112-2 and the two interleavers 113-1 and 113-2 are
Circuits having the same configuration may be used for each. At this time,
Since the signals 208-1 and 208-2 output from the interleavers 113-1 and 113-2 have the same transmission rate, the mapping circuit 103 has one symbol on the frequency axis and one symbol on the time axis as shown in FIG. These signals may be arranged every other time.

In the conventional error correction system shown in FIG. 25 and FIG. 26, since one set of error correction encoder and error correction decoder is used, a circuit such as a Viterbi decoder which is difficult to speed up is used. When used, there is a problem that the processing speed of the decoding circuit becomes the upper limit of the transmission speed of the system. On the other hand, since the error correction method of the present invention operates a plurality of decoders in parallel, the circuit scale becomes large, but the system speed can be easily increased.

FIG. 6 is a schematic block diagram showing the fourth embodiment of the present invention. The fourth embodiment is similar to the third embodiment in that the information sources are divided into two groups and transmitted, but two error correction encoders and two error correction decoders in FIG. 4 are used. Respectively, one error correction encoder 120 (FIG. 6 (a)) and one error correction decoder 125 (FIG. 6).
(B)) and uses them in a time division multiplex.

In the transmitter 307 of FIG. 6A, the information source
The data output from 110 is input to the error correction encoder 120 as it is and is error correction encoded. The encoded data is input to the switch 121, and the data is output to the two interleavers 122-1 and 122-2 at regular intervals. Here, if the error correction code is a block code, the switch 121 switches the interleaver to be output at the break of the code word. By switching in this way, the sequences output to the two interleavers become equal to the independently encoded sequences. When the error correction code is a convolutional code, in order to make the two sequences output from the switch independent, the convolutional code is terminated at regular intervals, or
The contents of the encoder are saved in the buffer and the switch is changed. The data interleaved by the interleavers 122-1 and 122-2 are processed and transmitted in the same manner as in the third embodiment. On the other hand, in the receiver 308 of FIG.
The demodulated and demapped two-series data are input to two deinterleavers 123-1 and 123-2. The deinterleaved two series of data are alternately input to the error correction decoder 125 by the switch 124 at regular intervals, and are independently subjected to error correction decoding.

In this embodiment, since the error correction encoder and the error correction decoder are used in time division multiplexing, they are not suitable for a very high speed system, but for a low speed system the implementation shown in FIG. The circuit scale can be made smaller than the example.

FIG. 7 is a schematic block diagram showing the fifth embodiment of the present invention. In this embodiment, the information source 110 outputs data 210 such as image and sound, and the information source encoder
It is assumed that high efficiency coding, hierarchical coding, coding into multidimensional information, etc. are performed by 126. The plurality of data sequences output from the information source encoder may have the same required reliability or transmission rate in the same sequence, or may have different sequences. Highly efficient coded or hierarchically coded data often has different required reliability and transmission rate for each series, and stereo audio data and multidimensional image data often have the same required reliability and transmission rate. In FIG. 7A, it is assumed that the data source encoder 126 outputs two series of data 211-1 and 211-2, the data 211-1 has a higher required reliability than the data 211-2, and The transmission speed is low.

The data 211-1 and 211-2 are error correction coded by the error correction coders 127-1 and 127-2, respectively. Here, the error correction encoder 127-1 is
Data shall be encoded with a code having a higher error correction capability than 7-2. For example, the transmission rates of data 211-1 and data 211-2 are 1M (dps) and 3M (dps), respectively.
The error correction encoder 127-1 encodes with an error correction code having a coding rate of 1/2, and the error correction encoder 127-2 encodes with an error correction code having a coding rate of 3/4. At this time, the data 212-1, 21-2 output from the error correction encoder
The transmission rates of 2-2 are 2M (dps) and 4M (dp), respectively.
s). These data are interleaver 128-1,
The signals are interleaved at 128-2 and input to the mapping circuit 129. Data 213-1 and 21 input to the mapping circuit
Transmission rates of 3-2 are 2M (dps) and 4M (dps) respectively
Therefore, as shown in FIG. 8, the modulation signals are mapped at a ratio of 1: 2. At this time, the data 213-1 (C ₁ in FIG. 8) is mapped to a signal in which all bits are not continuous on the frequency axis or the time axis.
Bits 213-2 (C ₂ in FIG. 8) will be mapped to a locally continuous signal. Data output from the mapping circuit 129 214-1, 214-2, ..., 21
4-m is modulated by the FDM modulator 103 and transmitted via the communication path 104.

On the other hand, in the receiver 308 of FIG. 7B, the received signal 216 is demodulated by the FDM demodulator 105, and the demapping circuit 130 restores it to the two series of data 218-1 and 218-2. These are deinterleaved by the deinterleavers 131-1 and 131-2, subjected to error correction decoding by the error correction decoders 132-1 and 132-2, and passed to the information source decoder 133. Here, of the two series of data input to the information source decoder, the data 22
Since 0-1 is coded with a code having a high error correction capability, it is possible to obtain higher reliability than the data 220-2. In the information source decoder 133, information source decoding is performed from these data,
Output to receiving purpose 134. Here, the reception purpose corresponds to a monitor or the like for image information and a speaker or the like for voice.

In the error correction system of this embodiment, when a plurality of pieces of data to be transmitted have different required reliability levels, they can be coded with error correction codes having different correction capabilities. As a result, the error correction system of the present invention can improve the quality of the image and voice reproduced by the receiver, as compared with the conventional error correction system in which all data is encoded by a single error correction code. In addition, when the transmission rate after encoding is different in a plurality of sequences, the sequence having a very high transmission rate (see C in FIG. 8).
_{In 2} ), all data cannot be uniformly distributed on the frequency axis or time axis when mapping to the modulated signal. In this case, burst errors can be dispersed relatively efficiently by mapping to a plurality of signal points that are locally continuous but some signals are discontinuous.

FIG. 9 is a schematic configuration diagram showing the configuration of another receiver in the fifth embodiment. However, in the transmitter 307 of FIG. 7, the source data 210 is the source encoder.
Hierarchical coding is performed at 26, and it is assumed that an image or sound can be reproduced from only one (211-1) of the two source-coded data.

In FIG. 9, the receiver 309 is shown in FIG.
It is assumed that the FDM signal 216 transmitted from the transmitter 307 is received. The received signal 216 is demodulated by the FDM demodulator 105 and input to the demapping circuit 130. The demapping circuit 130 selects only the signal corresponding to the data 218-1 in FIG. 7 from the demodulated data and inputs it to the deinterleaver 131-1. The data 219-1 de-interleaved by the deinterleaver 131-1 is the error correction decoder 132-
It is error-corrected and decoded in 1 and passed to the information source decoder 135.
Here, the information source decoder 135 reproduces the information source data from only the data 220-1 and outputs it to the receiving purpose 134.

As shown in this embodiment, when the information source is hierarchically coded, the quality of the generated image (or sound) is slightly deteriorated, but the original image ( Or voice) can be played. In the conventional error correction system shown in FIG. 25 or FIG. 26, even if the receiver wants to use only a part of the received signals, it is necessary to perform deleave and error correction decoding for all data, so that the circuit scale is large. There was a problem of becoming.
On the other hand, when the error correction system of the present invention is used, in a terminal that does not require high-definition reproduction information, only a part of the information needs to be de-interleaved and error-corrected and decoded. The circuit scale of can be reduced.

FIG. 10 is a schematic block diagram showing a sixth embodiment of the present invention. In this embodiment, it is assumed that one transmitter transmits two or more types of information. Figure 10 (a)
At 310, the transmitter 310 has two sources, 136-1 and 136-2.
, And data 221-1 and 221-2 are output from each. For example, the information source 136-1 outputs computer data and the information source 136-2 outputs image data. Each piece of information has different required reliability, transmission speed, and allowable delay time. For example, computer data is
The required reliability is high, but the allowable delay time is often long. Therefore, the error correction encoder 137-1 encodes the data with a code having a higher error correction capability than 137-2, and the interleaver 13
8-1 uses a RAM with a larger memory than 138-2. Each interleaved sequence has a mapping circuit 139.
Is input to, is mapped so as to be dispersed on the frequency axis or the time axis as much as possible, is modulated by the FDM modulator 103, and is transmitted via the communication path 104.

On the other hand, the receiver 311 of FIG. 10B demodulates the received signal 222 by the FDM demodulator 105 and returns it to the two series of data 223-1 and 223-2 by the demapping circuit 140. These are deinterleaved by the deinterleavers 141-1 and 141-2, subjected to error correction decoding by the error correction decoders 142-1 and 142-2, respectively, and output to the reception purposes 143-1 and 143-2. Here, the reception purpose 143-1 is, for example, a computer terminal, and the reception purpose 143.2 is, for example, a monitor.

In the error correction system of this embodiment, even if the required reliability and the allowable delay time of the two types of data to be transmitted are different, by using the error correction code of different correction ability and the interleaving of different depth, respectively. A suitable error correction coding or interleaving method can be used for As a result, it can be applied to a system for transmitting multimedia information.

FIG. 11 is a schematic configuration diagram showing the configuration of another receiver in the sixth embodiment. However, it is assumed that the receiver 312 in FIG. 11 is a receiver that requires only the data output from the information source 136-1 in the transmitter 310 in FIG.

In FIG. 11, the receiver 312 is shown in FIG.
The FDM signal 222 output from the transmitter 310 in (a) is received. The received signal 222 is demodulated by the FDM demodulator 105 and input to the demapping circuit 140. The demapping circuit 140 selects only the signal corresponding to the data 223-1 in FIG. 10 from the demodulated data and inputs it to the deinterleaver 141-1. The data de-interleaved by the deinterleaver 141-1 is subjected to error correction decoding by the error correction decoder 142-1 and passed to the reception purpose 143-1.

As shown in this embodiment, in a multimedia information system in which a plurality of types of information are transmitted, a multifunctional receiver that needs all information and a single receiver that needs only some information are used. It is expected that functional receivers will coexist. In the conventional error correction method shown in FIGS. 24 and 25, even if the single-function receiver uses only a part of the received signals, all the data needs to be de-interleaved and error-corrected and decoded. There was a problem that the scale became large. On the other hand, if the error correction system of the present invention is used, only a part of the information can be de-interleaved and error correction decoded in the receiver having a single function, so that the circuit scale of the receiver can be reduced.

FIG. 12 is a schematic configuration diagram showing the configuration of another receiver in the sixth embodiment. However, although it is assumed that the transmitter has the configuration shown in FIG.
The sources in shall output all the same kind of different content. For example, it is assumed that all of these information sources are image information having the same transmission rate, but there are a plurality of contents to be transmitted.

In FIG. 12, the receiver 313 is shown in FIG.
The FDM signal 222 output from the transmitter 310 in (a) is received. The received signal 222 is demodulated by the FDM demodulator 105 and input to the demapping circuit 140. The demapping circuit 140 converts the demodulated data into two series of data 223-1.
, 223-2 are output separately. These data 223-1, 2
23-2 is input to the switch 144, one of them is selected by the control signal 224, and is input to the deinterleaver 145. The data de-interleaved by the deinterleaver 145 is error-correction-decoded by the error-correction decoder 146 and passed to the reception purpose 147.

As shown in this embodiment, in a multi-channel image broadcasting system in which a plurality of information of the same type is transmitted, the receiver needs only one channel of information. In the conventional error correction system shown in FIGS. 25 and 26, there is a problem that the circuit scale becomes large because the receiver needs to perform de-interleave and error correction decoding on the data of all channels. On the other hand, when the error correction method of the present invention is used, the receiver only needs to de-interleave and error-correct decoding only the data for one channel, so that the circuit scale of the receiver can be reduced. Such a system includes, in addition to a multi-channel image broadcasting system, a downlink channel (a channel for transmitting information from a base station to a mobile station) of a mobile communication system in which one transmitter transmits information to a plurality of users. Can be given.

FIGS. 13, 14 and 15 are schematic configuration diagrams showing the circuit configuration of the mapping circuit according to the present invention.

In FIG. 13, the parallel signals 201-1, 201-2, ..., 201-n input to the mapping circuit are shown in FIG.
Corresponding to the outputs of the n error correction encoders in. These parallel signals are processed by the parallel / serial conversion circuit 148.
Is input to the serial / parallel conversion circuit 149. M parallel signals 202-1, 202-2 output from this circuit,
, 202-m corresponds to the input to the FDM modulator 103 in FIG. In FIG. 13, assuming that the transmission rates of the n input series are all equal, data of the same series of data transmitted at the same time can be mapped to carriers that are not continuous on the frequency axis. Further, when m is not divisible by n, a plurality of data transmitted in the same carrier with the same series of data can be mapped to a modulation signal that is not continuous on the time axis. For example, n = 5,
When m = 22, the input data of each series can be dispersed and mapped on the time axis and the frequency axis as shown in FIG.

FIG. 14 shows the mapping circuit of FIG. 13 in which the serial data 219 is interleaved and then input to the serial / parallel conversion circuit 152. In the interleaver 151, the output data 202-1, 202-2, ...,
In 202-m, replacement is performed so that the data of each input series is dispersed as much as possible on the time axis and the frequency axis. By this means, it is possible not only to disperse the burst error in each sequence but also in each sequence, so that it is possible to effectively disperse a long burst error due to deep fading.

FIG. 15 shows another mapping circuit construction method. 15, parallel signals 201-1, 201-2, ..., 201-n input to the mapping circuit are serial / parallel conversion circuits 153-1, 153-2, 153-n, respectively.
n parallel signals 221-1 and 221-
2, 221-m is output. In the rearrangement circuit 154, these parallel signals are rearranged within one modulation time or within a plurality of modulation times, and m parallel signals 202-1, 202-2, 20
Output 2-m. According to the configuration of this mapping circuit,
Since the input information is not converted into serial data, it can be easily realized even in a high transmission system.

In the error correction system of the present invention, coded modulation can be applied as an error correction coding method for the modulated signal of each carrier. As a seventh embodiment of the present invention, FIG. 16A shows a schematic block diagram in the case where an encoder for trellis coded modulation is used as an error correction encoder. Here, the coded modulation is higher than the normal error correction coding by considering the error correction coding and the bit mapping to the modulation signal together when performing multi-level modulation such as 8-phase PSK or QAM. It aims to perform data transmission with reliability, and "G. Ungerboeck," Trelis-coded Modulation with
Redundant Signal Sets, Part I: Introduction and P
art II: State of the Art ”, IEEE Communications
Magazine, Vol.25, No.2, February 1987, pp.5-21 ”.

In FIG. 16, each carrier is assumed to be modulated by 8PSK. At this time, the transmitter 314 inputs n sets of 2-bit parallel signals, and trellis encoders 155-1, 155-2, ... These trellis encoders are configured as shown in FIG. 17, for example. However, the circuit T in FIG. 17 represents a 1-bit delay element (for example, a D flip-flop). The 3 bits output from each of the n trellis encoders are input to the mapping circuit 156. The mapping circuit 156 maps n sets of 3-bit data to m sets of 3-bit data. At this time, the input 3-bit data is not divided but directly corresponds to the output 3-bit data. Further, if the series of n pieces of 3-bit data to be input are C ₁ , C ₂ , ..., C _n , the correspondence to the output m pieces of 3-bit data is, for example,
The mapping may be performed as shown in FIG. The output of the mapping circuit 156 is input to the FDM modulator 157, and each 3
Bit data is modulated into an 8PSK signal for each carrier.
At this time, the mapping from the 3-bit data to the 8PSK signal is performed by set partitioning as in the ordinary coded modulation. The signal modulated and multiplexed by the FDM modulator is transmitted through the communication path 104.

On the other hand, the receiver 315 of FIG. 16B demodulates the received signal by the FDM demodulator 158 and outputs m pieces of k-bit data. Here, k is an integer of 3 or more and is determined by the number of soft decision levels in the demodulator. These data are returned to the original n sets of data by the demapping circuit, and each of them is trellis encoder 160-1, 160-2, ..., 160-.
The data is input to n, subjected to error correction decoding, and n sets of 2-bit data are output.

When each carrier is multi-valued modulated as in this embodiment, the reliability of the transmission data can be improved by using coded modulation as the error correction code. FDM
A method using coded modulation as a transmission method is also proposed in the conventional error correction method shown in FIG. 26. However, this method uses a single trellis encoder and decoder, which makes it difficult to apply it to a high-speed system. There was such a problem. Also,
A system having a trellis encoder and a decoder for each carrier, such as the conventional error correction system shown in FIG. 27, can be applied to a high-speed system, but with respect to frequency selective fading. There was a problem that the effect was small. The error correction system of the present invention is easy to increase in speed and can spread the burst error due to fading by the mapping circuit, so that high reliability can be secured even if frequency selective fading occurs.

The error correction method of the present invention can also be applied as an inner coding method of an FDM transmission method using a concatenated code. 18 and 19 show the eighth and ninth aspects of the present invention.
As an example of, a schematic configuration diagram in the case of being applied to inner coding of a concatenated code is shown. Here, the concatenated code means that after the transmission data is error-correction-encoded by a Reed-Solomon multi-dimensional code (this is called an outer code), symbol interleaving is performed, and a binary code such as a convolutional code (this is It is a method of transmitting after error-correction coding with an inner code). By using the concatenated code, it is possible to perform data transmission with extremely high reliability.

FIG. 18 is a schematic block diagram showing the eighth embodiment of the present invention. Here, a concatenated code is used, and as shown in FIG.
Reed-Solomon encoder 161-1, 161-on F (256)
, ..., 161-n, and n binary encoders 164-1, 164-2, ..., 164-n are used for inner coding. If they match, the receiver 317 of FIG. 18B is used.

FIG. 19 is a schematic block diagram showing the ninth embodiment of the present invention. In the concatenated code used here, FIG.
As shown in 9 (a), one GF (256) is used for outer coding.
The above Reed-Solomon encoder 171 is used, and n binary encoders 164-1, 164-2, ..., 164-n are used for inner encoding. Therefore, the outer coded data is converted to n parallel data by the demultiplexer 173 and then inner coded. Regarding the code, the receiver 319 of FIG. 19B is used.

In the conventional error correction method shown in FIG.
Since there is only one encoder and decoder, there is a problem that it is difficult to increase the speed. In particular, when the Viterbi decoding is used for the decoder for the inner code, the processing speed of the Viterbi decoder is slower than that of the decoder for the multiple code (outer code), so that it cannot be applied to a system of higher speed. On the other hand, by providing a plurality of inner code encoders and decoders (for example, a convolutional encoder and a Viterbi decoder) as in this embodiment,
The present invention can be applied to a system having a transmission speed n times the processing speed of the inner code decoder.

The error correction method of the present invention is suitable for a system for transmitting information from one transmitting station to one or a plurality of receiving stations. 20, 21, 22, and 23 are conceptual diagrams showing the tenth to thirteenth embodiments of the transmission system using the error correction method of the present invention.

FIG. 20 shows a tenth embodiment as the first embodiment of the transmission system using the error correction method of the present invention. This embodiment can be applied to, for example, a digital image broadcasting system. In FIG. 20, the broadcasting station is configured like the transmitter 307 of FIG. 7A, and the moving image to be transmitted is hierarchically encoded. A signal transmitted from a broadcasting station is simultaneously received by a plurality of users. As shown in FIG. 20, the user 1 receives at the high definition image terminal and the user 2 receives at the low definition image terminal. The terminal of the user 1 is configured like the receiver 308 of FIG. 7B, and reproduces a high-definition image by using all the received signals. on the other hand,
The terminal of the user 2 is configured like the receiver 309 of FIG. 9 and decodes only a part of the hierarchically encoded information and reproduces low definition image information with a small circuit.

FIG. 21 shows an eleventh embodiment as the second embodiment of the transmission system using the error correction method of the present invention. This embodiment can be applied to, for example, a communication system for multimedia information. In FIG. 21, the transmitting station is configured like the transmitter 310 of FIG.
It is assumed that a plurality of different types of information (for example, computer data and image data) are transmitted. The signal transmitted from the transmitting station is received by a plurality of users at the same time. As shown in FIG. 21, the user 1 receives at the multi-function terminal, and the user 2 receives at the single-function terminal. The terminal of the user 1 is shown in FIG.
The receiver 311 is configured to decode all data of a plurality of types, and the user 1 uses it. On the other hand, the terminal of the user 2 is configured like the receiver 312 of FIG.
Only the type information is decrypted and the user 2 uses it.

As shown in FIGS. 20 and 21, in the transmission system using the error correction method of the present invention, when the receiving terminal has a low function provided to the user, the receiver circuit is downsized and low. Can consume power.

FIG. 22 shows a twelfth embodiment as the third embodiment of the transmission system using the error correction method of the present invention. This twelfth embodiment is, for example, a downlink channel of a mobile communication system (channel from a base station to a mobile station).
Can be applied to. In FIG. 22, the transmitting station is
The oscillated information is received from the users 1 and 2 and transmitted to the users 3 and 4, respectively. Here, it is assumed that the transmission station and the users 1 and 2 are connected by wire or wirelessly, and the users 3 and 4 that are mobile stations are connected by wireless. The transmitter included in the transmitting station is the transmitter 310 in FIG.
The information oscillated from the users 1 and 2 is multiplexed with the FDM signal and transmitted. The transmitted signal is
At the same time, user 3 and user 4 receive. The receiving terminals of the users 3 and 4 are configured like the receiver 313 of FIG. 12, and each selects and decodes the data oscillated from its communication partner.

FIG. 23 shows a thirteenth embodiment as a fourth example of the transmission system using the error correction method of the present invention. This embodiment can be applied to, for example, a multi-channel digital broadcasting system. In FIG. 23, the transmitting station is configured like the transmitter 310 of FIG. 10A, and multiplexes image data or audio data of a plurality of channels with an FDM signal and transmits it. The transmitted signal is simultaneously received by a plurality of users. The receiving terminal of each user is configured like the receiver 313 of FIG. 12, and each selects and decodes only the channel information that the user wants to use.

In the system shown in FIGS. 22 and 23, F
Each receiving terminal needs only one piece of information of the same kind of information multiplexed with the DM signal. In such a system, if a conventional error correction method having only one error correction encoder, decoder, interleaver, and deinterleaver for all frequencies is used, the power consumption of each receiving terminal will increase. There was a problem. On the other hand, when the error correction system of the present invention is used, each receiver only needs to de-interleave and error-correction-decode only necessary data, which has an effect of reducing power consumption of the receiver.

The error correction method of the present invention is an error correction method used for frequency division multiplexing (FDM) transmission.
Orthogonal Frequency Division Multiplexing (OF), which is a special case of DM transmission
It goes without saying that it can be applied to DM) transmission.

[0065]

As described above, since the error correction method of the present invention has a plurality of error correction encoders and decoders, it can be easily applied to a system having a high transmission rate and the mapping means is used. As a result, even if selective fading occurs, the deterioration of the error rate is small. Further, since error correction coding is independently performed for each group and interleaving is performed, the receiver can be downsized and the power consumption can be reduced when only a part of data is received.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an error correction method of the present invention.

FIG. 2 is a conceptual diagram for explaining the operation of the mapping circuit in the first embodiment of the error correction method of the present invention.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the error correction method of the present invention.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the error correction method of the present invention.

FIG. 5 is a conceptual diagram for explaining the operation of the mapping circuit in the third embodiment of the error correction method of the present invention.

FIG. 6 is a schematic configuration diagram showing a fourth embodiment of the error correction method of the present invention.

FIG. 7 is a schematic configuration diagram showing a fifth embodiment of the error correction method of the present invention.

FIG. 8 is a conceptual diagram for explaining the operation of the mapping circuit in the fifth embodiment of the error correction method of the present invention.

FIG. 9 is a schematic configuration diagram showing the configuration of another receiver in the fifth embodiment of the error correction method of the present invention.

FIG. 10 is a schematic configuration diagram showing a sixth embodiment of the error correction method of the present invention.

FIG. 11 is a schematic configuration diagram showing the configuration of another receiver in the sixth embodiment of the error correction method of the present invention.

FIG. 12 is a schematic configuration diagram showing the configuration of another receiver in the sixth embodiment of the error correction method of the present invention.

FIG. 13 is a schematic configuration diagram showing a configuration of a mapping circuit in the embodiment of the error correction method of the present invention.

FIG. 14 is a schematic configuration diagram showing another configuration of the mapping circuit in the embodiment of the error correction method of the present invention.

FIG. 15 is a schematic configuration diagram showing another configuration of the mapping circuit in the embodiment of the error correction method of the present invention.

FIG. 16 is a schematic configuration diagram showing a seventh embodiment of the error correction method of the present invention.

FIG. 17 is a schematic configuration diagram of a trellis encoder.

FIG. 18 is a schematic configuration diagram showing an eighth embodiment of the error correction system of the present invention.

FIG. 19 is a schematic configuration diagram showing a ninth embodiment of the error correction system of the present invention.

FIG. 20 is a conceptual diagram showing a tenth embodiment of a transmission system using the error correction system of the present invention.

FIG. 21 is a conceptual diagram showing an eleventh embodiment of a transmission system using the error correction system of the present invention.

FIG. 22 is a conceptual diagram showing a twelfth embodiment of a transmission system using the error correction system of the present invention.

FIG. 23 is a conceptual diagram showing a thirteenth embodiment of the transmission system using the error correction system of the present invention.

FIG. 24 is a conceptual diagram of signal transmission in frequency division multiplex transmission.

FIG. 25 is a schematic configuration diagram showing a conventional error correction method in frequency division multiplex transmission.

FIG. 26 is a schematic configuration diagram showing another conventional error correction method in frequency division multiplex transmission.

FIG. 27 is a schematic configuration diagram showing another conventional error correction method in frequency division multiplex transmission.

FIG. 28 is a conceptual diagram showing an error state caused by frequency selective fading.

[Explanation of symbols]

101-1, 101-2, ..., 101-n Error correction coding means (encoder) 102 Mapping means (circuit) 106 Dividing means (demapping circuit) 107-1, 107-2, ..., 107- n Error correction decoding means (decoder) 112-1, 112-2, 120 Error correction coding means (encoder) 114 Mapping means (circuit) 115 Dividing means (demapping circuit) 117-1, 117- 2, 125 Error correction decoding means (decoder) 127-1, 127-2 Error correction coding means (coder) 129 Mapping means (circuit) 130 Dividing means (demapping circuit) 132-1, 132- 2 Error correction decoding means (decoder) 137-1, 137-2 Error correction coding means (encoder) 139 Mapping means (circuit) 140 Dividing means (demapping circuit) 142-1, 142-2 Error Correction decoding means (decoder)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyasu Nakajima 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center

Claims (3)

[Claims] 1. An error correction method for frequency division multiplex transmission for correcting an error in frequency division multiplex transmission, wherein a digital signal output from one or a plurality of information sources is transmitted using a plurality of carriers of different frequencies. Side, the step of error-correcting coding the transmission data divided into a plurality of groups for each group, and the multiple data transmitted in the same time with the same group of error-correcting coded data are transmitted at all frequencies. A plurality of non-adjacent carriers or some frequencies are mapped to non-adjacent carriers, the error correction method in frequency division multiplex transmission. 2. An error correction method for frequency division multiplex transmission for correcting an error in frequency division multiplex transmission, wherein a digital signal output from one or a plurality of information sources is transmitted using a plurality of carriers having different frequencies. Side, the step of error-correcting coding the transmission data divided into a plurality of groups for each group, and the plurality of data transmitted by the same frequency carrier in the same group of error-correcting coded data Error-correcting method for frequency division multiplex transmission, the method comprising: mapping a signal in which the signals are not continuous in time or a part of the signals to a set of signals in which the signals are not continuous in time. 3. A transmission system for transmitting a digital signal from one transmitter to a plurality of receivers using a plurality of carriers of different frequencies, wherein the transmitter is error-corrected for each group divided into a plurality of groups. A plurality of error correction encoding means for encoding and a plurality of data transmitted in the same time in the same group of error correction encoded data at a same time are not included in a plurality of carrier waves or some frequencies A means for mapping to a plurality of carriers that are not adjacent to each other, or a plurality of data transmitted in a carrier of the same frequency in the same group of error-correction-coded data, is used as a set or a set of signals in which all signals are not continuous in time. Means for mapping a signal of a part to a set of signals that are not continuous in time, and at least one of the mapping means, and A transmission system, characterized in that each receiving station comprises means for dividing demodulated data into a plurality of groups, and error correction decoding means for at least one of the divided groups.