Data transmission device

Abstract: A data transmission device comprises a transmitter device and a receiver device. The transmitter device divides a data to be transmitted into an original data requiring protection against code error and a data requiring no protection. The transmitter device then carries out error detection code adding operation and error correction coding at a redundancy 1/N on the original data to generate a coded data. The transmitter device divides the coded data by N, and outputs the N divided coded data and the data requiring no protection on a communication line under a time division multiplexing control. The receiver device receives the N coded data and the data requiring no protection. The receiver device carries out error correction decoding on the N divided coded data and a mixed coded data obtained by mixing the divided coded data, and carries out error detection on decoded data obtained by the decoding. The receiver device then outputs one of the decoded data from which no code error is detected together with the data requiring no protection. The data transmission device can carry out a data transmission protecting the transmitted data from burst code errors and random code errors without increase of redundancy.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a data transmission device suitable for data transmission in a communication environment in which code errors easily occur. Background Art In data transmission using a communication line in which code errors easily occur, a data lack or a miss receiving due to code errors often occurs in a receiver device and this deteriorates quality of receiving. In order to overcome this problem, technical means such as a retransmission control method or an error correction decoding is used. These technical means are disclosed in detail, for example, in a printed material written by Shu Lin and Daniel J. Costello under the heading of "Error Control Coding Fundamentals and Applications" Prentice Hall 1983. A retransmission control method is a method in which a transmitter device transmits duplicate data in response to a receiving error report from a receiver device. The retransmission control method is significantly effective to a data communication in which many code errors occur at a burst. However, the retransmission control method requires a reverse channel through which the receiver device sends the receiving error report to the transmitter device, and therefore the method cannot be used in data transmission devices having no reverse channel. Error correction coding is a method in which a receiver device corrects code errors of received data and therefore the method does not require any reverse channel. However, there is a case in which many code errors occur at a burst in a communication line and the code errors exceed the error correction ability. In such a case, a part of the code errors are not corrected in the error correction decoding and some code errors are remained in the decoded data. In order to reduce the remaining error, use of interleave is expected. However, when using interleave in data transmission, error correction ability corresponding to the number of code errors which are expected to be included in a section on which the interleave is carried out. Therefore, a very high redundancy is necessary for the error correction coding. Furthermore, when a heavy burst error exceeding the error correction ability occurs in a part of a section on which the interleave is carried out, it is impossible to correctly decode all of the received data even if the other part of the section includes no code error. In order to protect transmitted data from code errors without using reverse channel, a method in which a data and a error detection code added to the data are repeatedly transmitted at discrete plural times is expected as an effective method. In this method, the receiver device receives same data at plural discrete times, and the receiver device carries out error detection on the all received data, which are the same data if having no code error, and decodes one of the received data from which no code error is detected. The conventional data transmission methods are as described above. In the conventional art, it is quite difficult to provide an effective data transmission in which transmitted data can be protected from burst code errors and random code errors without use of reverse channel. The reason is more specifically described as follows: In order to protect transmitted data from burst code errors, it may be effective to use the above-described method to transmit same data at plural discrete times. When same data are transmitted at plural times according to the method, a part of the data may be transmitted to the receiver device with no code error. Therefore, if such a data having no code error can be transmitted and the data thus transmitted is decoded, it is possible to prevent that the transmission quality is degraded by a data lacking due to code errors. In some cases, however, random code errors occur in the all data which are discretely transmitted at plural times according to the above method. In such cases, the receiver device can detect the code errors of the all received data because all the data have the error detection codes. However, the receiver device cannot correct the code errors. Therefore, in this case, a data having no code error is not obtained in the receiver device at all even if each received data include little random code error. In order to overcome this problem, an method in which error correction coding is carried out on all data discretely transmitted at plural times and the errors of the data are corrected in the receiver device, is expected. However, if this method is used, a very high redundancy is required to obtain enough error correction ability. The use of the method to duplicately transmit same data deteriorates the transmission efficiency to some extent. However, the use of error correction coding deteriorates the transmission efficiency to more heavy extent, and therefore the transmission efficiency is significantly deteriorated. Furthermore, this method has a problem that the control of the redundancy requires control of frequency at which same data are transmitted and there is no method except for the method controlling frequency, and therefore the method lacks flexibility of redundancy adjustment in that the redundancy can be adjusted to only integrals of that of the original data. In European Patent Application 0 680 034 A1, a mobile radio communication system is described, which uses a sound or voice activity detector and convolutional coding. In the transmitter section of this system, when a sound absent section is detected in sound data to be transmitted, transmission of the sound data is stopped and, instead, tail bits are transmitted. Convolutional encoding is performed on the sound data and on the tail bits prior to transmission. The decoding is employed for decoding the convolutional code. Summary of the Invention In the consideration of the above, it is a first object of the present invention to provide a data transmission device which can carry out data transmission protecting the transmitted data against code error occurring at a burst and code error occurring at a random with no increase of redundancy of coding. It is a second object of the present invention to provide a data transmission device which can achieve the first object and can transmit data at a desired redundancy which may be a redundancy defined by non-integer number. In accordance with a first aspect of the present invention, there is provided a data transmission device as recited in Claim 1. Second and third aspects of the invention relate to respective data transmission devices as set forth in independent Claims 10 and 18. Various realisations of these devices are covered in the sub-claims. Brief Description of the Drawings Fig. 1 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a first preferred embodiment of the present invention. Fig. 2 is a block diagram showing the configuration of a receiver device of the data transmission device according to the first preferred embodiment. Fig. 3 shows an example of data transmitted from the transmitter device. Fig. 4 shows data processing carried out in some sections of the transmitter device and of the receiver device. Fig. 5 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a second preferred embodiment of the present invention. Fig. 6 is a block diagram showing the configuration of a receiver device of the data transmission device according to the second preferred embodiment. Fig. 7 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a third preferred embodiment of the present invention. Fig. 8 is a block diagram showing the configuration of a receiver device of the data transmission device according to the third preferred embodiment. Fig. 9 shows data processing carried out in some sections of the transmitter device and of the receiver device. Fig. 10 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a fourth preferred embodiment of the present invention. Fig. 11 is a block diagram showing the configuration of a receiver device of the data transmission device according to the fourth preferred embodiment. Fig. 12 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a fifth preferred embodiment of the present invention. Fig. 13 is a block diagram showing the configuration of a receiver device of the data transmission device according to the fifth preferred embodiment. Fig. 14 shows data processing carried out in some sections of the transmitter device and of the receiver device. Fig. 15 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a sixth preferred embodiment of the present invention. Fig. 16 is a block diagram showing the configuration of a receiver device of the data transmission device according to the sixth preferred embodiment. Fig. 17 is a block diagram showing the configuration of a transmitter device of a data transmission device according to a seventh preferred embodiment of the present invention. Fig. 18 is a block diagram showing the configuration of a receiver device of the data transmission device according to the seventh preferred embodiment. Fig. 19 is a block diagram showing the configuration of a data decoder of the receiver device. Fig. 20 shows data processing carried out in some sections of the transmitter device and of the receiver device. Detailed Description of the Preferred Embodiments A. First Preferred Embodiment Fig. 1 is a block diagram showing the configuration of a transmitter device 101 of a data transmission device according to a first preferred embodiment of the present invention. Fig. 2 is a block diagram showing the configuration of a receiver device 102 of the data transmission device. Fig. 3 shows an example of data transmitted from the transmitter device 101. Fig. 4 shows data processing carried out in some sections of the transmitter device 101 and of the receiver device 102. First of all, the description will be given with respect to the transmitter device 101. A data inputted through an input terminal 111 is sent to a data separator 113 via a buffer 112 coding unit by coding unit. The data separator 113 divides the data from the buffer 112 into a data requiring protection against code error and a data not requiring protection. The data separator 113 then supplies the data requiring protection to a CRC coder 114 as an original data and supplies the data not requiring protection to a multiplexer 118. The illustration (a) of Fig. 4 shows the original data supplied to the CRC coder 114. Some methods may be used for dividing transmitted data into a data requiring protection and a data not requiring protection are to be determined. For example, in transmission of data and audio signals in time division multiplexing system, there is expected a method in which the data is treated as data requiring protection and the audio signal is treated as data not requiring protection. In the case where data and audio signal are transmitted in a predetermined pattern, the data separator 113 may be designed so as to divide the data and the audio signal supplied from the buffer 112 according to the pattern. In transmission of hierarchical data such as image coded data, a method to treat header information of the data as data requiring protection and to treat the other information as data not requiring protection may be used. In this case, it is possible to discriminate the header part of the data from the other part according to the coding syntax of the data. Therefore, this case assumes that the transmitter device has a data separator having a property for interpreting the coding syntax. The CRC coder 114 adds a CRC (Cyclic Redundancy Check) code to the original data supplied from the data separator 113 as shown in the illustration (b) of Fig. 4. A tail bit adder 115 adds tail bits to the output data of the CRC coder 114 to terminate convolutional coding, and outputs a data including the original data, the CRC code and the tail bits as shown in the illustration (c) of Fig. 4. The tail bits have bit length corresponding to restrictional length of convolutional decoding carried out by a convolutional coder 116 which provided in the output side of the tail bit adder 115. The convolutional coder 116 is means for carrying out error correction coding at a coding ratio 1/2 on the data supplied from the tale bit adder 115. More specifically, the convolutional coder 116 in the preferred embodiment is to carry out convolution on the data supplied from the tale bit adder 115, and outputs a convolutional coded data having a redundancy 1/2 as shown in the illustration (d) of Fig. 4. A code divider 117 divides the convolutional coded data by two. Some methods are expected with respect to the dividing operation. In a method of the preferred embodiment, the code divider 117 divides the convolutional coded data supplied from the convolutional coder 116 into two parts which respectively correspond to two generation polynomial expressions. That is to say, if the convolutional coder 116 carries out convolution using generation polynomial expressions A and B, the code divider 117 divides the convolutional coded data supplied from the convolutional coder into a part corresponding to the expression A and a part corresponding to the expression B as shown in the illustration (e) of Fig. 4. The multiplexer 118 multiplexes the coded data which correspond to the generation polynomial expressions A and B and are outputted from the code divider 117, and the data not requiring protection outputted from the data separator 113. The multiplexer 118 then outputs a data thus multiplexed to a communication line via an output terminal 119. The multiplexing is carried out so that the data not requiring protection is inserted between the coded data corresponding to the generation polynomial expressions A and B as shown in Fig. 3, and the coded data are separated from each other in a time axis not so as to meet a same burst error. Next, the description will be given with respect to the receiver device 102. The data outputted from the transmitter device 101 as described above is transmitted to an input terminal 121 of the receiver device 102. The data thus transmitted is supplied to a demultiplexer 123 via a buffer 122 decoding unit by decoding unit and the data is divided into the two coded data and the data not requiring protection by the demultiplexer 123. The data not requiring protection is sent to a data mixer 128. In the two coded data, one corresponds to the generation polynomial expression A and the other corresponds to the generation polynomial expression B. The coded data corresponding the the generation polynomial expression A is sent to a convolutional code decoder 125A. The coded data corresponding to the generation polynomial expression B is sent to a convolutional code decoder 125B. Furthermore, the two coded data corresponding to the generation polynomial expressions A and B are sent to a code mixer 124. The convolutional code decoder 125A carries out decoding corresponding to the generation polynomial expression A on the coded data sent from the demultiplexer 123, and then generates a decoded data corresponding to the original data which has not had the convolution using the generation polynomial expression A as shown in the illustration (f) of Fig. 4(f). A CRC decoder 126A carries out code error detection on the decoded data based on the CRC code included in the decoded data. Similarly, the convolutional code decoder 125B carries out decoding corresponding to the generation polynomial expression B on the coded data sent from the demultiplexer 123 to generate a decoded data as shown in the illustration (g) of Fig. 4. A CRC decoder 126B carries out code error detection on the decoded data based on the CRC code included in the decoded data. On the other hand, the code mixer 124 mixes the coded data corresponding to the generation polynomial expressions A and B to generate a coded data corresponding to the convolutional coded data which has not had division by the code divider 117 of the transmitter device 101 as shown in the illustrations (f)-(h) of Fig. 4. A convolutional code decoder 125C carries out decoding on the coded data generated by the code mixer 124 to generate a decoded data corresponding to the original data which has not had convolution as shown in the illustration (h) of Fig. 4. A CRC decoder 126C carries out code error detection on the decoded data based on the CRC code included in the decoded data. The results of code error detection of the CRC decoders 126A-126C are sent to a selector 127. The selector 127 selects one of the decoded data which is expected to have no code error or to have a least remaining code error based on the results of code error detection. More specifically, the selection is carried out according to the following method: a. If the coded data outputted from the convolutional code decoder 125A-125C includes a coded data, from which no code error is detected, the selector 127 selects such a decoded data having no code error and sends it to the data mixer 128. b. If code errors are detected from all of the decoded data outputted from the convolutional code decoders 125A-125C, the selector 127 selects the decoded data outputted from the convolutional code decoder 125C and sends it to the data mixer 128. Because, the decoded data outputted from the convolutional code decoder 125C is obtained from the the coded data having a redundancy 1/2 by error correction decoding and it is expected that the remaining error is less than the remaining errors of the other decoded data. The data mixer 128 multiplexes the decoded data selected by the selector 127 and the data not requiring protection sent from the demultiplexer 123. The data mixer 128 outputs the demultiplexed data via an output terminal 129 as a decoded data. If the decoded data and the data not requiring protection are to be used by different external devices, the decoded data and the data not requiring protection may be supplied to the external devices via different output terminals. As described above, the two coded data are sent at discrete times from the transmitter device to the receiver device and the decoded data is obtained from these coded data in the preferred embodiment. Therefore, it is possible to reduce the probability of that no decoded data is obtained due to code error having a relative long remaining time such as burst error. Furthermore, the coded data capable of error correction is generated from the two coded data and the decoding is carried out using the coded data thus generated in the preferred embodiment. Therefore, even if random errors are included in the two coded error, the random errors can be corrected. Furthermore, the two coded data are transmitted putting the data not requiring protection therebetween. Therefore, it is possible to reduce the probability of that the two coded data meet a same burst error and to make a good use of the communication line. The first preferred embodiment is as described above but the range of the present invention is not restricted in the range of the preferred embodiment. There are some modifications of the above-described first preferred embodiment, for example, as follows: (1) The selector 127 may be designed so as to not only select the decoded data, from which no code error is detected, but compare the decoded data in order to reduce the miss-detection of the CRC decoders using the comparison result. More specifically, the selector 127 of this modification checks the all results of error detection and compares the decoded data. In the check and the comparison, when plural decoded data, from which no code error are detected, are recognized and the decoded data are different from each other, or when a decoded data, from which a code error is detected, corresponds to another decoded data, from which no code error is detected, the selector 127 judges that these no error detection may be due to miss-detection of the CRC decoder. (2) The above-described preferred embodiment discloses the example in which the transmitter device carries out error correction coding at a redundancy 1/N=1/2 and transmits the two coded data which are obtained by dividing the coded data into two parts. That is to say, the above-described preferred embodiment discloses the example of the present invention corresponding to N=2. However, it is obviously understood that the preferred embodiment may be modified so as to correspond to the other N. (3) The above-described preferred embodiment discloses the example in which the coded data is divided into the two coded data and the two coded data are transmitted. Therefore, in this disclosed example, the code mixer 124 generates a coded data capable of error correction using the two coded data, i.e., the all coded data transmitted from the transmitter device 101. However, in the modified example corresponding to the other N which is more than three, the code mixer 124 may select plural coded data among the all coded data transmitted from the transmitter device 101, and generate a coded data capable of error correction using the selected coded data. In another modified example, the code mixer 124 may generate plural coded data capable of error correction using the code data transmitted from the transmitter device 101. (4) The above-described preferred embodiment discloses the example in which the coded data is divided into the two coded data having a same code length. This example may be modified so that a coded data generated by error correction coding at a redundancy 1/N is divided into M (N>M) coded data which have different code lengths, and the M coded data are transmitted. For example, if error correction coding at a redundancy 1/3 is carried out, the coded data generated by the coding is divided into a longer coded data having a twice code length of the original data and a shorter coded data having a code length equal to that of the original data, and the two coded data are transmitted from the transmitter device. In this case, if the longer data includes a code error, the code error can be corrected only using the coded data. Therefore, in the receiver device, error correction decoding is carried out on the longer coded data. The shorter coded data may be decoded when the code error of the longer coded data is a burst error and cannot be corrected. In this modification, priorities can be assigned to the divided coded data in the transmission and the decoding. (5) In the above-described preferred embodiment, the CRC coder 114 is placed in front of the convolutional coder 116. This embodiment may be modified so that the CRC coder is placed in the output side of the code divider and CRC codes are added to the two coded data obtained from the code divider. In this modification, the error detections of the two coded data are carried out based on the CRC codes included in the coded data in the receiver device. If no error is detected from any coded data, decoding is carried out on such a coded data. If errors are detected from the all coded data, error correction coding is carried out on a coded data which is obtained by mixing the plural coded data. In this modification, quantity of operation is reduced in comparison to the case in which error correction coding of a mixed coded data is always carried out. (6) In the above-described preferred embodiment, convolutional coding is used as error correction coding. However, the error correction coding used in the present invention is not restricted to the convolutional coding. For example, invertible coding disclosed in a printed material written by Shu Lin and Daniel J. Costello, Jr. under the heading of "Error Control Coding Fundamentals and Applications" Prentice Hall 1983 may be used as error correction coding of the present invention. Generally, convolutional decoding using a generation polynomial expression, which is used in the transmitter device of the above-described preferred embodiment, is to convert an original data to a coded data, the content of which is different from that of the original data.In contrast, invertible coding is to convert an original data to a coded data which includes the original data. Therefore, if the invertible coding is used in the transmitter device of the modification, the original data is transmitted as one of the divided coded data. (7) The tale bit adder 115 may be omitted from the above- described preferred embodiment if a relative low error correction ability is required with respect to the bits placed in the vicinity of the terminal portion of the data requiring protection. In this case, the redundancy corresponding to the tale bit can be rejected. B. Second Preferred Embodiment Fig. 5 is a block diagram showing the configuration of a transmitter device 201 of a data transmission device according to a second preferred embodiment of the present invention. Fig. 6 is a block diagram showing the configuration of a receiver device 202 of the data transmission device. As shown in Fig. 5, the transmitter device 201 is made up of an input terminal 211, a buffer 212, a data separator 213, a tale bit adder 215, a convolutional coder 216, a code divider 217, a multiplexer 218 and an output terminal 219. In the above-described first preferred embodiment, the transmitter device 101 is designed so that the original data outputted from the data separator 113 is added with a CRC code by the CRC coder 114 and the original data having the CRC code is supplied to the tale bit adder 115. In the transmitter device 201 of the second preferred embodiment, the original data outputted from the data separator 213 is directly supplied to the tale bit adder 215. The other configuration is same as the configuration of the transmitter device 101 of the first preferred embodiment. In the transmitter device 201, the coded data corresponding to the generation polynomial expressions A and B are generated, and the two coded data and a data requiring no protection are multiplexed so that the two coded data are separated in a time axis and putting the data requiring no protection therebetween. The data thus multiplexed is transmitted to a communication line. Next, the description will be given with respect to the receiver device 202. The data transmitted from the transmitter device 201 is transmitted to an input terminal 221 of the receiver device 202 via the communication line. This data is supplied to a demultiplexer 223 decoding unit by decoding unit via a buffer 222, and the data thus supplied is divided into the two coded data and the data requiring no protection. The data requiring no protection is supplied from the demultiplexer 223 to a data mixer 228. On the other hand, the two coded data, which are protected against code error, are respectively supplied to convolutional code decoders 225A and 225B. Furthermore, the two coded data are supplied to a code mixer 224. The convolutional code decoder 225A carries out decoding corresponding to the generation polynomial expression A on the coded data which is supplied from the demultiplexer 223 to generate a decoded data corresponding to the original data which has not had convolution using the generation polynomial expression A. The decoded data thus generated is supplied to a tale bit inspector 226A. The tale bit inspector 226A compares tale bits which are added in the convolutional code generation with tale bits included in the decoded data to judge whether or not the decoded data has a code error. Similarly, the convolutional code decoder 225B carries out decoding corresponding to the generation polynomial expression B on the coded data supplied from the demultiplexer 223, and a tale bit inspector 226B carries out code error detection on a decoded data outputted from the convolutional code decoder 225B by comparison of tale bits. On the other hand, the code mixer 224 mixes the coded data corresponding to the generation polynomial expressions A and B to generate a coded data corresponding to the original coded data which has not had division. A convolutional code decoder 225C carries out a Viterbi decoding on the coded data generated by the code mixer 224 to generate a decoded data corresponding to the original data which has nod had convolutional coding. A metric inspector 226C compares a metric of remaining path, which is calculated in the decoding by the convolutional code decoder 225C, with a predetermined reference value to carry out error detection of the decoded data generated by the convolutional code decoder 225C. A selector 227 selects one of the decoded data which is expected to have no code error or a least remaining code error based on the results of code error detection of the tale bit inspectors 226A and 226B, and of the metric inspector 226C. More specifically, the selection is carried out according to the following method: a. If the decoded data outputted from the convolutional code decoders 225A-225C include a decoded data, from which no code error is detected, the selector 227 select such a decoded data having no code error and sends it to the data mixer 228. b. If code errors are detected from all of the decoded data outputted from the convolutional code decoders 225A-225C, the selector 227 selects the decoded data outputted from the convolutional code decoder 225C and sends it to the data mixer 228. Because, it is expected that the remaining error of this decoded data is the least. The data mixer 228 multiplexes the decoded data selected by the selector 227 and the data requiring no protection sent from the demultiplexer 223, and outputs the data thus multiplexed as a decoded data via an output terminal 229. As described above, error detection of the decoded data is carried out using the tales added in the error correction coding and the metric calculated in the error correction decoding. Therefore, it is not necessary to add a redundancy bit to the coded data for error detection. Thus, the redundancy of transmission can be reduced. In the above-described preferred embodiment, error detection of the decoded data is carried out by the tale bit inspectors and the metric inspector without use of the other additional information except for the tale bit. However, this embodiment may be modified so that the other error detection code such as a CRC code is also used. This modification can improve the accuracy of error detection. Furthermore, the above-described preferred embodiment may be modified by applying the modifications corresponding to the modifications (1)-(4) of the first preferred embodiment. C. Third Preferred Embodiment Fig. 7 is a block diagram showing the configuration of a transmitter device 301 of a data transmission device according to a third preferred embodiment of the present invention. Fig. 8 is a block diagram showing the configuration of a receiver device 302 of the data transmission device. Fig. 9 shows data processing carried out in some sections of the transmitter device 301 and of the receiver device 302. First of all, the description will be given with respect to the transmitter device 301. Like the first preferred embodiment, a data inputted through an input terminal 311 is supplied to a data separator 313 via a buffer 312 coding unit by coding unit. The data thus supplied is divided into a data requiring protection against code error and a data requiring no protection based on the importance of each part of the data. The data requiring protection is supplied to a CRC coder 314 as an original data as shown in the illustration (a) of Fig. 9. The data requiring no protection is supplied to a multiplexer 318. The original data is added with a CRC code for error detection as shown in the illustration (b) of Fig. 9 by the CRC coder 314, and further added with tale bits for termination of convolutional coding as shown in the illustration (c) of Fig. 9 by a tale bit adder 315. Like the first preferred embodiment, this tale bits has bit length corresponding to restrictional length of convolutional coding carried out by a convolutional coder 316 which is placed in the output side of the tale bit adder 315. The convolutional coder 316 carries out error correction coding at a redundancy 1/3 on the data supplied from the tale bit adder 315. More specifically, the convolutional coder 316 in the preferred embodiment carries out convolution using a generation polynomial expression on the data supplied from the tale bit adder 315 to generate a convolutional code having a redundancy 1/3 as shown in the illustration (d) of Fig. 9. A code divider 317 divides the convolutional code thus generated by the convolutional coder 316 by two to generate two punctured codes X and Y having a redundancy 2/3 as shown in the illustration (e) of Fig. 9. Punctured code is an error correction code which is generated by rejecting a part of a convolutional code. In transmission of such a punctured code, redundancy and error correction ability of the transmission can be controlled by changing the rejected part of the convolutional code. In this preferred embodiment, a part of original convolutional code is selected from the original code as a punctured convolutional code X, and a code different from the punctured convolutional code X is selected from the original code as a punctured convolutional code Y. Each one of the punctured codes X and Y has error correction ability. Therefore, it is possible to independently decode the original data, which has not had convolution coding, from each one of the punctured codes X and Y. In other word, the code selection for generating the punctured codes from the original convolutional code should be carried out so that the punctured codes having such an error correction ability are obtained. The multiplexer 318 multiplexes the two coded data (punctured codes X and Y) and the data requiring no protection outputted from the data separator 313, and outputs the data thus multiplexed to a communication line via an output terminal 319. Like the first preferred embodiment, the multiplexing is carried out so that the data requiring no protection is inserted between the coded data and the coded data are separated from each other in a time axis not so as to meet a same burst error (refer Fig. 3). Next, the description will be given with respect to the receiver device 302. The data outputted from the transmitter device 301 is transmitted to an input terminal 321 of the receiver device 302. The data thus transmitted is supplied to demultiplexer 323 via buffer 322 decoding unit by decoding unit and the data is divided into the two coded data (i.e., the punctured codes X and Y) and the data requiring no protection by the demultiplexer 323. The data requiring no protection is sent to a data mixer 328. The punctured code X is supplied to a convolutional code decoder 325A and the punctured code Y is supplied to a convolutional code decoder 325B. Furthermore, the punctured codes X and Y are supplied to a code mixer 324. The convolutional code decoder 325A carries out error correction decoding on the punctured code X sent from the demultiplexer 323 to generate a decoded data corresponding to the original data which has not had convolutional coding as shown in the illustration (f) of Fig. 9. A CRC decoder 326A carries out code error detection on the decoded data based on the CRC code included in the decoded data. Similarly, the convolutional code decoder 325B carries out error correction decoding on the punctured code Y sent from the demultiplexer 323 as shown in the illustration (g) of Fig. 9, and a CRC decoder 326B carries out code error detection on the decoded data based on the CRC code included in the decoded data. On the other hand, the code mixer 324 mixes the punctured codes X and Y to generate a convolutional code corresponding to the original convolutional code which has not had division as shown in the illustrations (f)-(h) of Fig. 9. A convolutional code decoder 325C carries out decoding operation, which corresponds to the above-described generation polynomial expression used by the convolutional coder 316, on the convolutional code generated by the code mixer 324, to generate a decoded data corresponding to the original data which has not had the convolutional coding using the generation polynomial expression as shown in the illustration (h) of Fig. 9. A CRC decoder 326C carries out code error detection on the decoded data based on the CRC code included in the decoded data. The results of code error detection of the CRC decoders 326A-326C are sent to a selector 327. The selector 327 selects one of the decoded data which is expected to have no code error or a least remaining code error based on the results of code error detection. More specifically, the selection is carried out according to the following method: a. If the decoded data outputted from the convolutional code decoder 325A-325C include a coded data, from which no code error is detected, the selector 327 selects such a decoded data having no code error and sends it to the data mixer 328. b. If code errors are detected from all of the decoded data outputted from the convolutional code decoders 325A-325C, the selector 327 selects the decoded data outputted from the convolutional code decoder 325C and sends it to the data mixer 328. Because, the decoded data outputted from the convolutional code decoder 325C is obtained from the the coded data having a redundancy 1/3 by error correction decoding and it is expected that the remaining error is less than the remaining errors of the other decoded data. The data mixer 328 multiplexes the decoded data selected by the selector 327 and the data requiring no protection sent from the demultiplexer 323. The data mixer 328 then outputs the multiplexed data via an output terminal 329 as a decoded data. If the decoded data and the data requiring no protection are used by different external devices, the decoded data and the data requiring no protection may be supplied to the external devices via different output terminals. The third preferred embodiment is as described above and the effects of the above-described first preferred embodiment are also obtained from the third preferred embodiment. There are following modifications with respect to the third preferred embodiment: (1) Like the first preferred embodiment, the selector 327 may be designed so as to not only select the decoded data, from which no code error is detected, but also compare the decoded data in order to reduce the miss-detection of the CRC decoders using the comparison result. (2) The above-described preferred embodiment discloses the example in which the transmitter device carries out error correction coding at a redundancy 1/N=1/3 and transmits the two coded data which are obtained by dividing the coded data into two parts. That is to say, the above-described preferred embodiment discloses the example in the case of N=3 and M=2. However, it is obviously understood that the preferred embodiment can be obviously embodied in the conditions of the other N and M. (3) The above-described preferred embodiment discloses the example in which the coded data is divided into the two coded data and the two coded data are transmitted. Therefore, in this disclosed example, the code mixer 324 generates a coded data capable of error correction using the two punctured codes, i.e., the all coded data transmitted from the transmitter device 301. However, in a modified example, the code mixer 324 may select plural coded data among the all coded data transmitted from the transmitter device 301, and generate a punctured code which has error correction ability higher than those of the transmitted code data. In another modified example, the code mixer 124 may generate plural punctured codes having error correction ability. (4) The above-described preferred embodiment discloses the example in which the coded data is divided into the two coded data having a same code length. This example may be modified so that a coded data generated by error correction coding at a redundancy 1/N is divided into M (N>M) coded data which have different code lengths, and the M coded data are transmitted. For example, if error correction coding at a redundancy 1/3 is carried out, the coded data generated by the coding is divided into a longer coded data having a twice code length of the original data and a shorter coded data having a code length equal to that of the original data, and the two coded data are transmitted from the transmitter device. In this case, if the longer data includes a code error, the code error can be corrected only using the coded data. Therefore, in the receiver device, error correction decoding is carried out on the longer coded data, and the shorter coded data is decoded when the code error of the longer coded data is a burst error and cannot be corrected. In this manner, priorities can be assigned to the divided coded data in the transmission and decoding. (5) In the transmitter device 301 of the above-described preferred embodiment, the CRC coder 314 is placed in front of the convolutional coder 316. This embodiment may be modified so that the CRC coder is placed in the output side of the code divider and CRC codes are added to the two coded data obtained from the code divider. In this modification, the error detections of the two coded data are carried out based on the CRC codes included in the coded data in the receiver device. If no error is detected from any coded data, decoding is carried out on such a coded data. If errors are detected from the all coded data, an error correction coding is carried out on a coded data which is obtained by mixing the plural coded data. In this modification, quantity of operation is reduced in comparison to the case in which error correction coding of a mixed coded data is always carried out. (6) In the above-described preferred embodiment, a convolutional coding is used as error correction coding. However, the other error correction coding such as an invertible coding may be used instead of the convolutional coding. The advantage of use of invertible coding has been already described in the first preferred embodiment. (7) The tale bit adder 315 may be omitted from the above- described preferred embodiment if a relative low error correction ability is required with respect to the bits placed in the vicinity of the terminal portion of the data requiring protection. In this case, the redundancy corresponding to the tale bit can be rejected. D. Fourth Preferred Embodiment Fig. 10 is a block diagram showing the configuration of a transmitter device 401 of a data transmission device according to a fourth preferred embodiment of the present invention. Fig. 11 is a block diagram showing the configuration of a receiver device 402 of the data transmission device. As shown in Fig. 10, the transmitter device 401 is made up of an input terminal 411, a buffer 412, a data separator 413, a tale bit adder 415, a convolutional coder 416, a code divider 417, a multiplexer 418 and an output terminal 419. In the above-described third preferred embodiment, the transmitter device 301 is designed so that the original data outputted from the data separator 313 is added with a CRC code by the CRC coder 314 and the original data having the CRC code is supplied to the tale bit adder 315. In the transmitter device 401 of the fourth preferred embodiment, the original data outputted from the data separator 413 is directly supplied to the tale bit adder 415. The other configuration is the same as the configuration of the transmitter device 301 of the third preferred embodiment. Next, the description will be given with respect to the receiver device 402. The data transmitted from the transmitter device 401 is transmitted to an input terminal 421 of the receiver device 402 via the communication line. This data is supplied to a demultiplexer 423 decoding unit by decoding unit via a buffer 422, and the data thus supplied is divided into two coded data and an data requiring no protection. The data requiring no protection is supplied from the demultiplexer 423 to a data multiplexer 428. On the other hand, the two coded data, which are punctured codes X and Y protected from code error, are respectively supplied to convolutional code decoders 425A and 425B. Furthermore, the punctured codes X and Y are supplied to a code mixer 424. The convolutional code decoder 425A carries out error correction decoding on the punctured code X to generate a decoded data corresponding to the original data which has not had convolution. The decoded data thus generated is supplied to a tale bit inspector 426A. The tale bit inspector 426A compares tale bits which are added in the generation of the punctured code with the decoded tale bit to judge whether or not the decoded data has a code error. Similarly, the convolutional code decoder 425B carries out error correction decoding on the convolutional code Y, and a tale bit inspector 426B carries out code error detection on a decoded data outputted from the convolutional code decoder 425B by comparison of tale bits. On the other hand, the code mixer 424 mixes the punctured codes X and Y to generate a convolutional code corresponding to the original convolutional code which has not had division. A convolutional code decoder 425C carries out a Viterbi decoding on the convolutional code thus generated by the code mixer 424 to generate a decoded data corresponding to the original data which has not had convolution coding. A metric inspector 426C compares a metric of remaining path, which is calculated in the decoding by the convolutional code decoder 425C, with a predetermined reference value to carry out error detection of the decoded data generated by the convolutional code decoder 425C. A selector 427 selects one of the decoded data which is expected to have no code error or a least remaining code error based on the results of code error detection of the tale bit inspectors 426A and 426B, and of the metric inspector 426C according to the method as described in the second preferred embodiment. A data mixer 428 multiplexes the decoded data selected by the selector 427 and the data requiring no protection sent from the demultiplexer 423, and outputs the data thus multiplexed as a decoded data via an output terminal 429. As described above, error detection of the decoded data is carried out using the tale bits which are added in the error correction coding and the metric which is calculated in the error correction decoding. Therefore, it is not necessary to add redundancy bits to the coded data for error detection. Thus, the redundancy of transmission can be reduced like the second preferred embodiment. In the above-described preferred embodiment, error detection of the decoded data is carried out by the tale bit inspectors and the metric inspector without use of the other additional information except for the tale bit. However, this embodiment may be modified so that the other error detection such code as a CRC code is also used. This modification can improve the accuracy of error detection. Furthermore, the above-described preferred embodiment may be modified by applying the modifications corresponding to the modifications (1)-(4) of the third preferred embodiment. E. Fifth Preferred Embodiment Fig. 12 is a block diagram showing the configuration of a transmitter device 501 of a data transmission device according to a fifth preferred embodiment of the present invention. Fig. 13 is a block diagram showing the configuration of a receiver device 502 of the data transmission device. Fig. 14 shows data processing carried out in some sections of the transmitter device 501 and of the receiver device 502. First of all, the description will be given with respect to the transmitter device 501. A data inputted through an input terminal 511 is supplied to a data separator 513 via a buffer 512 coding unit by coding unit. The data thus supplied is divided into a data requiring protection and a data requiring no protection based on the importance of each part of the data. The data requiring protection is supplied to a CRC coder 514 as an original data as shown in the illustration (a) of Fig. 14. The data requiring no protection is supplied to a multiplexer 518. The original data is added with a CRC code for error detection as shown in the illustration (b) of Fig. 14 by the CRC coder 514, and further added with tale bits for termination of convolutional coding as shown in the illustration (c) of Fig. 14 by a tale bit adder 515. This tale bits has bit length corresponding to restrictional length of convolutional coding carried out by a convolutional coder 516. The convolutional coder 516 carries out error correction coding at a redundancy 2/3 on the data supplied from the tale bit adder 515. More specifically, the convolutional coder 516 in the preferred embodiment carries out convolution on the data supplied from the tale bit adder 515 to generate a convolutional code having a redundancy 1/3, and generates a punctured convolutional code having a redundancy 2/3 based on the convolutional code as shown in the illustration (d) of Fig. 14. A code divider 517 divides the convolutional code thus generated by the convolutional coder 516 by three to generate three punctured codes X, Y and Z as shown in the illustration (e) of Fig. 14. Each one of the punctured codes X, Y and Z has a shorter code length than the original data which has not had convolution. However, if generating coded data having a code length which is equal to or more than the code length of the original data by combinations of two or more convolutional codes selected from the convolutional codes X, Y and Z, i.e., combinations of X and Y, and of Y and Z, and of Z and X, and of X, Y and Z, the original data can be decoded from each one of the generated code data. In this preferred embodiment, the code selection for generating the punctured codes X, Y and Z from the original convolutional code should be carried out so that the punctured codes having such an ability are obtained. The multiplexer 518 multiplexes the three coded data (the punctured codes X, Y and Z) and the data requiring no protection outputted from the data separator 513, and outputs the data thus multiplexed to a communication line via an output terminal 519. As described in the first preferred embodiment, the multiplexing is carried out so that the data requiring no protection is inserted between the coded data and the coded data are separated from each other in a time axis not so as to meet a same burst error (refer Fig. 3). Next, the description will be given with respect to the receiver device 502. The data outputted from the transmitter device 501 is transmitted to an input terminal 521 of the receiver device 502. The data thus transmitted is supplied to demultiplexer 523 via a buffer 522 decoding unit by decoding unit. The data is then divided into the three coded data (i.e., punctured codes X, Y and Z) and the data requiring no protection by the demultiplexer 523. The data requiring no protection is sent to a data mixer 528. The three coded data protected from code error, i.e., the punctured convolutional codes X, Y and Z are supplied to code mixers 524A-524D. The code mixer 524A mixes the punctured codes X and Y to generate a punctured code XY, and the code mixer 524B mixes the punctured codes Y and Z to generate a punctured code YZ, the code mixer 524C mixes the punctured codes Y and Z to generate a punctured code YZ, and the code mixer 524D mixes the punctured codes X, Y and Z to generate a punctured convolutional code XYZ which is the original punctured convolutional code before the division. A convolutional code decoder 525A carries out error correction decoding on the punctured convolutional code XY generated by the code mixer 524A to generate a decoded data corresponding to the original data before the convolutional coding as shown in the illustration (f) of Fig. 14. Similarly, a convolutional code decoder 525B carries out error correction decoding on the punctured code YZ generated by the code mixer 524B to generate a decoded data corresponding to the original data before the convolutional coding as shown in the illustration (g) of Fig. 14. A convolutional code decoder 525C carries out error correction decoding on the punctured code ZX generated by the code mixer 524C to generate a decoded data corresponding to the original data before the convolutional coding as shown in the illustration (h) of Fig. 14. Furthermore, a convolutional code decoder 525D carries out error correction decoding on the punctured convolutional code XYZ generated by the code mixer 524D to generate a decoded data corresponding to the original data before the convolutional coding as shown in the illustration (i) of Fig. 14. CRC decoders 526A-526D respectively carry out code error detection on the decoded data obtained from the convolutional code decoders 525A-525D based on the CRC codes included in the decoded data. The results of code error detection of the CRC decoders 526A-526C are sent to a selector 527. The selector 527 selects one of the decoded data which is expected to have no code error or a least remaining code error based on the results of code error detection. More specifically, the selection is carried out according to the following method: a. If the coded data outputted from the convolutional code decoders 525A-525D include a coded data, from which no code error is detected, the selector 527 select such a decoded data having no code error and sends it to a data mixer 528. b. If code errors are detected from all of the decoded data outputted from the convolutional decoding code decoder 525A- 525D, the selector 527 selects the decoded data outputted from the convolutional code decoder 525D and sends it to the data mixer 528. Because, the decoded data outputted from the convolutional code decoder 525D is obtained from the the coded data having a redundancy 2/3 and it is expected that the remaining error is less than those of the other decoded data. The data mixer 528 multiplexes the decoded data selected by the selector 527 and the data requiring no protection sent from the demultiplexer 523 and output the multiplexed data via an output terminal 529 as a decoded data. If the decoded data and the data requiring no protection are used by different external devices; the decoded data and the data requiring no protection may be supplied to the external devices via different output terminals. The fifth preferred embodiment is as described above and the effects of the above-described first preferred embodiment are also obtained from the fifth preferred embodiment. There are following modifications with respect to the fifth preferred embodiment: (1) Like the first preferred embodiment, the selector 527 may be designed so as to not only select the decoded data, from which no code error is detected, but also compare the decoded data in order to reduce the miss-detection of the CRC decoders using the comparison result. (2) In the above-described preferred embodiment, the redundancy of error correction decoding of the transmitter device is 2/3, and the convolutional code obtained by error correction coding is divided by three, and the three coded data thus divided are transmitted. However, in a modification, the other redundancy and dividing number may be selected. (3) The above-described preferred embodiment discloses the example in which the coded data is divided into the three coded data having a same code length. This example may be modified so that the coded data is divided into coded data which have different code lengths. In the general transmission of data including synchronous information, probability of generation of code error is relative low with respect to the portion of data which is right after the synchronous information. Therefore, a modification in which a leading part of an original data which is right after the synchronous information is transmitted as coded data having a long code length and the other part is transmitted as code data having a shorter code length than that of the leading part. In another modification, the original convolutional code may be divided into a plurality of coded data having different code lengths including not only code length shorter than that of the original data but also code length equal to or more than that of the original data. In the receiver device of this modification, when a received coded data, which can be independently decoded, has no code error, the coded data is decoded and the decoded data is outputted. When a code error is detected from such a code data, a coded data and the other code data are mixed to generate a coded data having error correction ability, and error correction coding is carried out using the coded data thus generated. In this manner, priorities can be assigned to the divided coded data in the transmission and decoding. Therefore, the modification gives an advantage that effective decoding can be carried out in the receiver device. (5) In the transmitter device 501 of the above-described preferred embodiment, the CRC coder 514 is placed in front of the convolutional coder 516. This embodiment may be modified so that the CRC coder is placed in the output side of the code divider and CRC codes are added to the two coded data obtained from the code divider. In this modification, the error detections of the two coded data are carried out based on the CRC codes included in the coded data in the receiver device. If no error is detected from a coded data which can be independently decoded or a coded data obtained by mixing coded data, decoding is carried on such a coded data. If errors are detected from the all coded data, error correction coding is carried out on a coded data which is obtained by mixing coded data. In this modification, quantity of operation is reduced in comparison to the case in which error correction coding of a mixed coded data is always carried out. (6) In the above-described preferred embodiment, convolutional coding is used as error correction coding. However, the other error correction coding such as an invertible coding may be used instead of the convolutional coding. (7) The tale bit adder 515 may be omitted from the above- described preferred embodiment if a relative low error correction ability is required with respect to the bits placed in the vicinity of the terminal portion of the data requiring protection. In this case, the redundancy corresponding to the tale bit can be rejected. F. Sixth Preferred Embodiment Fig. 15 is a block diagram showing the configuration of a transmitter device 601 of a data transmission device according to a sixth preferred embodiment of the present invention. Fig. 16 is a block diagram showing the configuration of a receiver device 602 of the data transmission device. As shown in Fig. 15, the transmitter device 601 is made up of an input terminal 611, a buffer 612, a data separator 613, a tale bit adder 615, a convolutional coder 616, a code divider 617, a multiplexer 618 and an output terminal 619. In the above-described fifth preferred embodiment, the transmitter device 501 is designed so that the original data outputted from the data separator 513 is added with a CRC code by the CRC coder 514 and the original data having the CRC code is supplied to the tale bit adder 515. In the transmitter device 601 of the sixth preferred embodiment, the original data outputted from the data separator 613 is directly supplied to the tale bit adder 615. The other configuration is same as the configuration of the transmitter device 501 of the fifth preferred embodiment. Next, the description will be given with respect to the receiver device 602. The data transmitted from the transmitter device 601 is transmitted to an input terminal 621 of the receiver device 602 via the communication line. This data is supplied to a demultiplexer 623 decoding unit by decoding unit via a buffer 622, and the data thus supplied is divided into three coded data and an data requiring no protection. The data requiring no protection is supplied from the demultiplexer 623 to a data multiplexer 628. On the other hand, the three coded data, which are punctured codes X, Y and Z protected from code error, are supplied to code mixers 624A-624D. Like the above-described fifth preferred embodiment, the code mixer 624A generates a punctured code XY using the punctured codes X and Y, and the code mixer 624B generates a punctured code YZ using the punctured codes Y and Z, and the code mixer 624C generates a punctured code ZX using the punctured codes Z and X, and the code mixer 624D generates a punctured convolutional code XYZ, which corresponds to the original convolutional code before division, using the punctured codes X, Y and Z. The convolutional code decoders 625A-625D respectively carry out a Viterbi decoding on the punctured codes generated by the code mixers 624A-624D to respectively generate decoded data. Furthermore, the convolutional decoders 625A-625D calculates the metrics of the remaining paths in the Viterbi decoding thereof and respectively send the calculated metrics to metric inspectors 626A-626D. The metric inspectors 626A- 626D respectively carry out code error detection on decoded data outputted from the convolutional decoders 625A-625D by respectively comparing the calculated metrics with a predetermined reference value. A selector 627 selects one of the decoded data based on the results of code error detection as follows: a. If the decoded data generated by the convolutional code decoders 625A-625D include a decoded data having no error, the selector selects such a decoded data and outputs it to a data mixer 628. b. If code errors are detected from the all coded data generated by the convolutional code decoders 625A-625D, the selector selects the decoded data generated by the convolutional code decoder 625D and outputs it to the data mixer 628. The data mixer 628 multiplexes the decoded data selected by the selector 627 and the data requiring no protection sent from the demultiplexer 623, and outputs the data thus multiplexed as a decoded data via an output terminal 629. As described above, error detection of the decoded data is carried out using metrics which are calculated in the error correction decoding. Therefore, it is not necessary to add redundancy bits to the coded data for error detection. Thus, the redundancy of transmission can be reduced like the second preferred embodiment. This embodiment may be modified so that the other error detection code such as a CRC code is also used. This modification can improve the accuracy of error detection. Furthermore, the above-described preferred embodiment may be modified by applying the modifications corresponding to the modifications (1)-(3) of the fifth preferred embodiment. G. Seventh Preferred Embodiment In the first and second embodiments, a coded data having a redundancy 1/N is divided by N and the divided coded data are transmitted as leading and trailing portions of a frame. Thus, in the case where a burst error having a long burst length (remaining time of burst error) occasionally appears, one of the divided coded data received by the receiver device may include a code error but the other divided coded data may include no code error. In such a case, it is therefore expected that accurate decoding can be carried out in the receiver device using the coded data having no code error. However, if the preferred embodiments are used in a condition in which burst errors having a short burst length appear at short intervals, such a use of the preferred embodiment increases a probability of that each one of the divided coded data received by the receiver device includes a code error. In this case, each one of the divided coded data does not have error correction ability. Therefore, the receiver device cannot carry out error correction decoding independently using each one of the divided coded data. Furthermore, even if the divided coded data are mixed, the use of the mixed coded data increases a probability of that the original data is not accurately decoded because the mixed coded data includes code errors which have been included in the divided coded data. In the third and fourth preferred embodiment, a coded data having a redundancy 1/N is divided by M (M<N) and therefore the code length of each one of the divided coded data is longer than the code length of the original data before the coding. Thus, in a condition in which a burst error having a long burst length occasionally appears, the use of the preferred embodiments increases a probability of that the coded data transmitted have burst errors, and therefore the transmission characteristics is not improved. However, the coded data transmitted in the preferred embodiments respectively have error correction ability. In the case where the preferred embodiments are used in a condition in which burst errors having a short burst length appear at short intervals, the receiver device can respectively decode the received coded data by error correction decoding using the error correction abilities of the decoded data. Even if the coded data received by the receiver device have code errors, the coded data having no code error can be obtained as long as the code errors are slight errors which can be corrected by the error correction abilities. Therefore, the preferred embodiments are effective as means for improving the error correction ability of the communication in a condition that burst errors having a short burst length appear at short intervals. The use of the fifth and sixth preferred embodiment provides a good transmission characteristics in a condition in which a burst error having a long burst error occasionally appears like the first and second preferred embodiments. However, if the preferred embodiments are used in a condition in which burst errors having a short burst length appear at short intervals, the transmission characteristics are not improved. Considering the advantage and disadvantage of the above-described preferred embodiments, it is effective to change the method for dividing the coded data in response to the condition of code error appearance in order to carry out high quality coding transmission in every condition. The seventh preferred embodiment is based on the consideration as described above. In the preferred embodiment, in a condition in which a burst error having a long burst length appears, the coded data is divided into coded data having a code length shorter than that of the original data before the coding in order to reduce the probability of that the coded data transmitted include a code error. In contrast, in a condition in which burst errors having a short burst length appear, the coded data is divided into coded data having a code length longer than that of the original data before the coding so that the receiver device can decode the coded data by error correction coding using the error correction abilities of the coded data. The preferred embodiment requires means for changing the method for dividing the coded data in response to a burst length of a burst error generated in the communication line. In order to carry out the changing, it is necessary to assume a burst length of a burst error generated in the communication line. In mobile communication, a method using measurement of Doppler frequency can be used as means for assuming burst length. More specifically, it is known in mobile communication that the burst length of burst errors are in inverse proportion to Doppler frequency of a phasing generated due to the movement of a terminal equipment. Therefore, the burst length can be assumed from the measurement of Doppler frequency by using this characteristics of the mobile communication. Figs. 17-20 shows the seventh preferred embodiment based on a technical thought as described above. The preferred embodiment is made up by mixing the first and third preferred embodiments. Fig. 17 is a block diagram showing the configuration of a transmitter device 701 of a data transmission device according to the seventh preferred embodiment. Fig. 18 is a block diagram showing the configuration of a receiver device 702 of the data transmission device. Fig. 19 is a block diagram showing the configuration of a data decoder provided in the receiver device 702. Fig. 20 shows data processing carried out in some sections of the transmitter device 701 and of the receiver device 702. First of all, the description will be given with respect to the transmitter device 701 with reference to Fig 17. A data inputted through an input terminal 711 is supplied to a data separator 713 via a buffer 712 coding unit by coding unit. The data thus supplied is divided into a data requiring protection and a data requiring no protection based on the importance of each part of the data. The data requiring protection is supplied to a CRC coder 714 as an original data as shown in the illustration (a) of Fig. 20. The data requiring no protection is supplied to multiplexers 718A and 718B. The original data is added with a CRC code for error detection by the CRC coder 714, and further added with tale bits for termination of convolutional coding by a tale bit adder 715 as shown in the illustration (b) of Fig. 20. The tale bits has a bit length corresponding to a restrictional length of convolutional coding carried out by a convolutional coder 716. The convolutional coder 716 carries out error correction coding at a redundancy 1/3 on the data supplied from the tale bit adder 715. As a result, a convolutional code having a redundancy 1/3 is generated by the convolutional coder 716 as shown in the illustration (c) of Fig. 20. On the other hand, a burst length assuming device 703 assumes a burst length in a method by measurement of Doppler frequency for example. If the assumed burst length is shorter than a predetermined threshold value, the burst length assuming device 703 supplies the convolutional code generated by the convolutional coder 716 to a code divider 717A. If the assumed burst length is longer than the threshold value, the burst length assuming device 703 supplies the convolutional code to a code divider 717B. The code divider 717A divides the input convolutional code by two. Therefore, when the burst length is short, the convolutional code having a redundancy 1/3 generated by the convolutional coder 716 is divided by two by the code divider 717A. As a result, two coded data having a redundancy 2/3 are obtained like the third preferred embodiment (refer the illustrations (d) and (e) of Fig. 9). In contrast, the code divider 717B divides the input convolutional code by three. Therefore, when the burst length is long, the convolutional code having a redundancy 1/3 generated by the convolutional coder 716 is divided by three by the code divider 717B as shown in the illustrations (c) and (d) of Fig. 20. In this manner, the convolutional code is divided into coded data having a redundancy 1 like the first preferred embodiment. When coded data are generated by the code divider 717A, the multiplexer 718A multiplexes the coded data thus generated with the data requiring no protection supplied from the data separator 713. Similarly, when coded data are generated by the code divider 717B, the multiplexer 718B multiplexes the coded data thus generated with the data requiring no protection supplied from the data separator 713. When the burst length is short and the burst length assuming device 703 supplies the convolutional code to the code divider 717A, the burst length assuming device 703 reports it to an identification bit adder 704 and selects the output signal of the multiplexer 718A to supply the output signal to the identification bit adder. As a result, an identification bit which indicates that the convolutional code is divided by two is added with the output signal of the multiplexer 718A by the identification bit adder 704, and the output signal attaching with the identification bit is outputted to the communication line via an output terminal 719. On the other hand, when the burst length is long and the burst length assuming device 703 supplies the convolutional code to the code divider 717B, the burst length assuming device 703 reports it to the identification bit adder 704 and selects the output signal of the multiplexer 718B to supply the output signal to the identification bit adder. As a result, an identification bit which indicates that the convolutional code is divided by three is added with the output signal of the multiplexer 718B by the identification bit adder 704, and the output signal attaching with the identification bit is outputted to the communication line via the output terminal 719. Next, the description will be given with respect to the receiver device 702 with reference to Fig. 18. The receiver device 702 has an identification bit judging device 705, a buffer 706, and a data decoders 707A and 707B. The data outputted from the transmitter device 701 are accumulated in the buffer 706 via an input terminal 721. The accumulated data are outputted from the buffer 706 decoding unit by decoding unit. The identification bit judging device 705 judges identification bits of the data thus outputted decoding unit by decoding unit, and supplies the output data to the data decoder 707A or 707B according to the result of the judgement regarding to the identification bit. That is to say, if the output data of the buffer 706 is a data obtained by dividing the convolutional code by two (i.e., the data which has had the operation by the code divider 717A), the identification bit judging device 705 supplies the data to the data decoder 707A. In contrast, if the output data of the buffer 706 is a data obtained by dividing the convolutional code by three (i.e., the data which has had the operation by the code divider 717B), the identification bit judging device 705 supplies the data to the data decoder 707B. The data decoder 707A has the same configuration as the demultiplexer 323 and the elements following to the demultiplexer of the receiver device 302 of the third preferred embodiment. When the output data of the buffer 706 is supplied to the data decoder 707A, the data is divided into the data requiring protection and the data requiring no protection. The data requiring protection includes two coded data having a redundancy 2/3. In the data decoder 707A, error correction decoding using each one of the two coded data and error correction decoding using a mixed coded data made up of the two coded data are carried out, and the decoded data which has the least remaining error is selected and is outputted as shown in the illustrations (f)-(h) of Fig. 9. On the other hand, the data decoder 707B has a configuration as shown in Fig. 19. The output data of the buffer 706 is supplied to a demultiplexer 823 via an input terminal 821 and is divided into the data requiring protection and the data requiring no protection. The data requiring protection includes three coded data corresponding to generation polynomial expressions A, B and C. Convolutional code decoders 825A-825C respectively decode the three coded data as shown in the illustrations (e)-(g) of Fig. 20. Code mixers 824A-824C respectively generate mixed coded data by combining two of three coded data. The convolutional code decoders 825A-825C respectively carry out error correction decoding on the mixed coded data generated by the code mixers 824A-824C as shown in the illustrations (h)-(j) of Fig. 20. A code mixer 824D mixes the three coded data to generate a mixed coded data. A convolutional code decoder 825G carries out error correction decoding on the mixed coded data as shown in the illustration (k) of Fig. 20. CRC decoders 826A-826G carry out code error detection on the decoded data generated by the convolutional code decoder 825A-825G. A selector 827 selects one of the decoded data based on the result of the code error detection according to the same method as the first preferred embodiment, and supplies the selected decoded data to a data mixer 828. The data mixer 828 multiplexes the decoded data with the data requiring no protection and outputs the data thus multiplexed via an output terminal 829. As described above, the same operation as the first preferred embodiment is carried out except for the use of the three coded data. The identification bit judging device 705 shown in Fig. 18 selects one of the output terminals of the data decoder 707A and 707B based on the result of the judgement regarding to the identification bit. As a result, the output data of the selected data decoder is outputted via an output terminal 729. The seventh preferred embodiment is as described above using the example of the combination of the first and third preferred embodiments. However, the range of the present invention is not restrict within the example and there are modifications of the preferred embodiment. For example, a data transmission device which provides the same advantage as the above-described seventh preferred embodiment can be provided by using means for dividing the coded data into coded data having a shorter code length than the code length of the original data which has not had coding, and means for dividing the coded data into coded data having a longer code length than the code length of the original data. Furthermore, in the above-described preferred embodiment, the range of burst length is divided into two ranges, i.e., a shorter burst length range and a longer burst length range, and the method for dividing the coded data is selected based on the range which includes the assumed burst length. However, the range of burst length may be divided into three or more burst length ranges, and the different methods for dividing the coded data may be defined for the different burst length ranges. In this case, one of the methods corresponding to the range including the assumed burst length may be selected for dividing the coded data.

Claims: A data transmission device comprising: a transmitter device for carrying out error-correction coding on an original data, which is to be transmitted, to generate a coded data and for outputting data relating to said coded data on a communication line, and a receiver device for receiving the data relating to said coded data through the communication line and for carrying out error-correction decoding, characterised in that : the transmitter device (101, 201, 301, 401) is arranged to generate the coded data with a coding ratio 1/N and to divide the coded data into M parts, M ≤ N, and to output the M coded data parts onto the communication line, such that the M coded data parts are temporally separated from each other; and the receiver device (102, 202, 302, 402) is arranged to receive the M coded data parts and to carry out the error-correction decoding (125, 225, 325, 425) on each one of a plurality of coded data, the plurality of coded data comprising the M coded data parts and a combined coded data (124, 224, 324, 424) obtained by combining the M coded data parts, and to select one of the plurality of decoded data which is expected to have no code error or to have a least remaining code error, and to output the selected decoded data. Data transmission device as claimed in Claim 1, wherein the transmitter device is further arranged to divide the data to be transmitted into the original data requiring protection against code error and data requiring no protection and to multiplex the M coded data parts and the data requiring no protection to generate a multiplexed data which is output on the communication line, and the receiver device is arranged to divide the multiplexed data into the M divided coded data and the data requiring no protection. Data transmission device as claimed in Claim 1 or Claim 2, wherein the transmitter device is further arranged to carry out an error detection code adding operation on the original data and the receiver device is arranged to carry out code error detection on the plurality of coded data. Data transmission device as claimed in Claim 1 or Claim 2, wherein the transmitter device is arranged to generate coded data by convolution, and the receiver device is arranged to detect code errors of the decoded data parts by comparing tail bits included in the decoded data parts with tail bits used in the generation of the convolutional coded data and to carry out error-correction decoding by a Viterbi decoding operation on said combined coded data, the receiver device detecting a code error of the Viterbi-decoded data by comparing a metric of a remaining path calculated in the error-correction Viterbi decoding operation with a predetermined reference value. Data transmission device as claimed in any one of the preceding claims, wherein M = N. Data transmission device as claimed in any one of Claims 1 to 4, wherein M<N and the M coded data have different code lengths. Data transmission device as claimed in any one of Claims 1 to 4, wherein N=3 and M=2. Data transmission device as claimed in Claim 7, wherein the M coded data have different code lengths. Data transmission device as claimed in Claim 8, wherein the different code lengths are a code length equal to that of the original data and a code length equal to twice that of the original data. A data transmission device comprising: a transmitter device for carrying out error-correction coding on an original data, which is to be transmitted, to generate a coded data, and for outputting data relating to said coded data on a communication line, and a receiver device for receiving the data relating to said coded data through the communication line and for carrying out error-correction decoding, characterised in that the transmitter device (501, 601) is arranged to generate the coded data with a coding ratio M/N, where M < N, and to divide the coded data into N parts, and to output the N coded data parts onto the communication line, such that the N coded data parts are temporally separated from each other; and the receiver device (502, 602) is arranged to receive the N coded data parts and to carry out the error-correction decoding (525, 625) on each one of a plurality of coded data, the plurality of coded data comprising combinations (524, 624) of the N coded data parts, and to select one of the plurality of decoded data which is expected to have no code error or to have a least remaining code error, and to output the selected decoded data. Data transmission device as claimed in Claim 10, wherein the transmitter device is further arranged to divide the data to be transmitted into the original data requiring protection against code error and data requiring no protection and to multiplex the N coded data parts and the data requiring no protection to generate a multiplexed data which is output on the communication line, and the receiver device is arranged to divide the multiplexed data into the N coded data parts and the data requiring no protection. Data transmission device as claimed in Claim 10 or Claim 11, wherein the transmitter device is further arranged to carry out an error detection code adding operation on the original data and the receiver device is arranged to carry out code error detection on the plurality of coded data. Data transmission device as claimed in Claim 10 or Claim 11, wherein the receiver device is arranged to carry out error-correction decoding by a viterbi decoding operation on each one of said plurality of coded data, the receiver device detecting for each one of said plurality of coded data, a code error of the Viterbi-decoded data by comparing a metric of a remaining path calculated in the error-correction Viterbi decoding operation with a predetermined reference value. Data transmission device as claimed in any one of Claims 10 to 13, wherein the N coded data parts are all of the same code length. Data transmission device as claimed in any one of Claims 10 to 13, wherein the N coded data parts are of a code length shorter than or equal to that of the original data. Data transmission device as claimed in any one of Claims 10 to 15, wherein M=2 and N=3. Data transmission device as claimed in Claim 15, wherein the transmitter device is arranged to carry out error correction coding by generating a coded data with a coding ratio of 1/3 and by generating a punctured convolutional code having a coding ratio of 2/3. A data transmission device comprising: a transmitter device for carrying out error-correction coding on an original data, which is to be transmitted, to generate a coded data, and for outputting data relating to said coded data on a communication line, and a receiver device for receiving the data relating to said coded data and for carrying out error-correction coding, characterised in that the transmitter device (701) is arranged to generate the coded data with a coding ratio of 1/N, and to divide the coded data selectively into one of a plurality of sets (717A, 717B) of parts, the selection being on the basis of an estimation (703) of the burst length of a burst error, the various sets having different numbers of parts (divide-by-2; divide-by-3), the transmitter device being further arranged to output the selected set of coded data parts on a communication line, such that the N coded data parts are temporally separated from each other; and the receiver device is arranged to detect the estimated burst length, to receive the selected set of coded data parts through the communication line and to carry out the error-correction decoding on each one of a plurality of coded data, the plurality of coded data selectively comprising, in dependence on the detected burst length, the corresponding number of coded data parts employed in the transmitter device and a combined coded data (824) obtained by combining the corresponding number of coded data parts, the receiver device being also arranged to select one of the plurality of decoded data which is expected to have no code error or to have a least remaining code error, and to output the selected decoded data.

Inventors: ADACHI SATORU, KAWAHARA TOSHIRO, MIKI TOSHIO, OHYA TOMOYUKI, SUZUKI TAKASHI, ADACHI, SATORU, KAWAHARA, TOSHIRO, MIKI, TOSHIO, OHYA, TOMOYUKI, SUZUKI, TAKASHI
Applicants: NIPPON TELEGRAPH & TELEPHONE, NTT MOBILE COMMUNICATIONS NETWORK INC.
Application year: 1997
Main classification: H03M13
IPC codes: H03M13, H04L1