JPH06276108A - Variable length data transmission system by means of convoluting code - Google Patents

Abstract

PURPOSE:To efficiently transmit data in a variable length system while using a convoluting code by transmitting coded data of the variable length form by adding it with coded data size information of a fixed length form, and transmitting the data. CONSTITUTION:Original data D0 to Dn sent from the GPS receiver of a reference station are respectively sent to the number of data bytes integrating part 52 and a Hagelburger coding circuit 54 for data through the reception circuit 51 of the data transmission use modem equipment 5 of the reference station. The circuit 54 encodes sent original data D0 to Dn of K1 byte into Hagelburger code. On the other hand, the integrating part 52 counts the byte numbers of data and a coding circuit 53 for a data size converts it to the code of fixed length. Next, a transmission data preparing circuit 55 prepares transmission data from the outputs of the circuits 53 and 54 to transmit it to a moving station through an MKS modulation circuit 56. Data can efficiently be transmitted by the variable length system with this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable length data transmission system using a convolutional code.

[0002]

2. Description of the Related Art A problem that cannot be avoided in data transmission of digital communication is occurrence of data error during communication. Random errors and burst errors are the types of this data error. The random error is an error that occurs at each time point irrespective of other time points, and is an error that occurs discontinuously in isolation, and a burst error is an error that occurs in a continuous manner in time.

In order to correct such a code error, many error correction methods have been conventionally proposed. The error correction can be roughly classified into a block code and a convolutional code according to its code structure. The block code divides the data into blocks of a certain length and encodes each block. The convolutional code treats data as a series of data without dividing it into blocks of a fixed length, and sequentially performs coding while depending on data before that. Further, each code includes a code suitable for a random error and a code suitable for a burst error.

The block code has the following features. -The encoding structure is relatively simple. -Redundancy due to encoding is small and the number of parity bits for error correction is small. -Data is divided into blocks and processed, so variable-length data can be handled. -In general, error correction capability is not very high.

On the other hand, the convolutional code has the following features. -The encoding structure is rather complicated. -Redundancy due to coding is rather large, and many parity bits are required for error correction.・ High error correction capability. -Since data is not divided into blocks and processed, it cannot be used as it is for variable length data.

The convolutional code is, for example, a differential GPS (Grob) which is a positioning system using satellites.
transmission of differential data in al Positioning System), MCA (Multi Chan)
nel access) Used for data transmission in systems. This differential GPS system and M
In the CA system, the Hagelbarger code is used as the convolutional code. The Hagelberger code is a convolutional code for burst error correction, and is a convolutional code for the purpose of correcting a burst error when there is a relatively long error-free period between two burst errors.

The error correction capability of the Hagerberger code is shown below. In case of single burst error The error can be corrected regardless of where in the data the consecutive errors of 1 to 6 bits are included in the received Hagerberger code. In case of multiple burst errors (two or more errors at intervals)

[0008]

[Table 1]

Next, a conventional data transmission method using a convolutional code will be described with reference to FIGS. 9 and 10. FIG. 9 is an explanatory diagram of conventional encoding, and FIG. 10 is a diagram showing a conventional transmission format.

In the case of conventional data transmission using a convolutional code, as shown in FIG. 9A, the original data to be transmitted is divided into fixed-length data blocks, and the divided fixed-length block units are used. Then, as shown in FIG. 9 (B), encoding is performed using a predetermined convolutional code such as Hargelberger code, and the convolutionally encoded data, the bit synchronization signal BSINC, and the frame synchronization signal FSYNC are encoded.
And are used to form a fixed-length frame in accordance with the transmission format of FIG.
They were sequentially transmitted as shown in (C).

[0011]

As described above, in the conventional data transmission system using the convolutional code, the data is always transmitted in the fixed length format. Therefore, the conventional data transmission method has a problem in that it cannot cope with variable-length data whose data length changes.

Further, if the above-mentioned conventional data transmission method is to be applied to variable-length data as well, processing such as insertion of dummy data for converting variable-length data into fixed-length data must be performed, Even if variable-length data could be transmitted, there was a problem that the transmission efficiency would drop significantly.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a data transmission system capable of efficiently transmitting data in a variable length format while using a convolutional code. It is to be.

[0014]

In order to achieve the above-mentioned object, the transmission system of the present invention encodes original data consisting of variable-length data into data of variable-length format by using a convolutional code, and The data size of the data is encoded into a fixed-length format data size information using a convolutional code, and the encoded fixed-length format data size information is added to the encoded variable-length format data and transmitted. It is something that is done.

[0015]

In the transmission system of the present invention having the above-mentioned structure, the data size information is transmitted together with the convolutionally encoded variable length data. Therefore, the receiving side can accurately know the data size of the received variable length data from this data size information, so that even if the variable length data is convolutionally encoded and transmitted, the original data can be accurately reproduced. You can

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below when it is applied to a differential GPS system. Before describing the embodiment of the present invention, first, what kind of differential GPS system is will be briefly described with reference to FIG.

What is the differential GPS system?
As shown in the conceptual diagram of FIG. 2, it is one of the GPS positioning methods for more accurately positioning the current position of a moving body such as a ship, and accurate position data such as latitude, longitude and altitude can be obtained. One GPS receiver is installed in the known land-based reference station 1 (fixed point), and the other is installed in the mobile station 2 such as a ship whose position is to be measured. Then, the same GP is used by the GPS receivers of the base station 1 and the mobile station 2, respectively.
It receives a plurality of GPS signals from S satellites S _{1 to} S _n (4 in 3D positioning, 3 in 2D positioning).

In the reference station 1, the difference between the positioning value of the reference station 1 calculated from the received GPS signal and the known accurate position data of the reference station is obtained, and this difference is used as correction differential data to move by wireless communication or the like. Send to station 2. On the other hand, the mobile station 2 subtracts the correction value of the differential data from the positioning value of the current position obtained by the installed GPS receiver so as to obtain the extremely accurate positioning data of the current position with the error corrected. It was done.

FIG. 3 shows the above-mentioned differential GP.
The block diagram of S system is shown. In FIG. 1, the reference station 1 on land includes a GPS receiving antenna 3, a GPS receiver 4, a data transmitting modem device 5, a wireless transmitter 6, and a data transmitting antenna 7. The mobile station 2 such as a ship includes a data receiving antenna 8, a wireless receiver 9, a data receiving modem device 10, a GPS receiving antenna 11, and a GPS receiver 12.

The GPS receiver 4 of the reference station 1 receives the GPS signal from the GPS satellite to calculate the position of the reference station, compares the calculated value with the known accurate position data of the reference station, and the difference value thereof. Ask for. Then, the obtained difference value is wirelessly transmitted to the mobile station 2 via the data transmission modem device 5, the wireless transmitter 6, and the data transmission antenna 7 as differential data for correction.

The GPS receiver 12 of the mobile station 2 is the base station 2
It receives a GPS signal from the same GPS satellite as the above and determines its own position. On the other hand, the wireless receiver 9 receives the differential data sent from the reference station 2, and sends it to the GPS receiver 12 via the data receiving modem device 10. The GPS receiver 12 corrects the positioning error by subtracting the correction value of the differential data from the positioning value calculated from the GPS signal. As a result, the mobile station 2 obtains extremely accurate positioning data of the current position with the error corrected.

Next, an embodiment of the present invention will be described.
The present invention is realized by applying the data transmission modem device 5 of the reference station 1 and the data reception modem device 10 of the mobile station 2 in the differential GPS system shown in FIG. That is, FIG. 4 is a block diagram showing an embodiment of the data transmission modem device 5 of the reference station 2 configured by applying the method of the present invention, and FIG. 5 is a block diagram of the mobile station 2 configured by applying the method of the present invention. 1 is a block diagram showing an embodiment of a data receiving modem device 10. FIG.

The data transmission modem device 5 shown in FIG.
An RS232C receiving circuit 51 for exchanging data with the S receiver 4 in the RS232C format, a data byte number integrating section 52 for counting the number of data bytes of variable length data,
Data size Hargelberger encoding circuit 53 for convolutionally encoding the accumulated number of bytes of variable length data into fixed length data size information, and data Hargelberger encoding circuit for convolutionally encoding variable length data 54,
It is composed of a transmission data creation circuit 55 and an MSK modulation circuit 56 for assembling the obtained data size information and encoded data into a frame of a predetermined format as shown in FIG.

The data receiving modem device 10 shown in FIG.
Is an MSK demodulation circuit 101, a data size Hagerleburger decoding circuit 102 for decoding encoded data size information, and a data acquisition circuit for acquiring data corresponding to the data size according to the decoded data size information. 103, a data Hagerberger decoding circuit 104 for decoding encoded variable data, and an RS232C transmission circuit 105 for exchanging data with the GPS receiver 12.

Next, the operation of the data transmitting modem device 5 of FIG. 4 will be described with reference to the coding explanatory diagram of FIG. Now, it is assumed that original data having various byte configurations as shown in FIG. 1A is sent from the GPS receiver 4 of the reference station 2 as differential data. The original data shown in FIG. 1A is the RS232C receiving circuit 51.
Via the data byte number integration unit 52 and the data Hagerberger encoding circuit 54, respectively.

Hagelberger coding circuit 54 for data
Is the _{first of} FIG. 1 (A) consisting of K ₁ bytes sent
The th original data is Hagerberger encoded as shown in FIG. On the other hand, the data byte number integration unit 52
The number of bytes K ₁ of the first original data of FIG. 1 (A) sent is counted. The counted number of bytes K ₁ of the original data is sent to the data size Hargelberger encoding circuit 53 and converted into a fixed length Hargelberger code.

The encoded data shown in FIG. 1C and the data size information K shown in FIG. 1B obtained as described above.
₁ is sent to the transmission data creation circuit 55. The transmission data creation circuit 55, in accordance with the transmission format shown in FIG. 6, the encoded data of FIG. 1C, the data size information K ₁ of FIG. 1B, the bit synchronization signal BSYNC, and the frame synchronization signal FSYNC. From this, transmission data of one frame as shown in FIG. 1D is generated.

The above process is repeated for each of the variable length data K ₁ , K ₂ , K ₃ , ... Of FIG. 1 (A), so that a series of transmissions having a frame structure as shown in FIG. 1 (D). Get the data. The transmission data shown in FIG. 1 (D) is MSK-modulated by the MSK modulation circuit 56, then sent to the wireless transmitter 6, and wirelessly transmitted from the data transmitting antenna 7 to the mobile station 2 such as a ship. .

Next, the data receiving modem device 10 shown in FIG.
The operation will be described with reference to the decoding explanatory diagram of FIG. 7. The transmission data wirelessly transmitted from the reference station 1 is received by the radio receiver 9 of the mobile station 2 and is MSK demodulated by the MSK demodulation circuit 101, and then as reception data as shown in FIG. It is input to the Burger decoding circuit 102.

The data size Hargelberger decoding circuit 102 fetches the data size information K ₁ of the first frame from the input received data of FIG. 7A,
This data size information K ₁ is decoded to obtain the data size K ₁ for the _first frame shown in FIG. 7 (B).

The data receiving circuit 103 selects the received data from the received data according to the decoded data size K ₁ .
As shown in (C), the encoded data corresponding to the data size is fetched and sent to the data Hagelberger decoding circuit 104. The data Hagerberger decoding circuit 104 decodes the captured coded data,
Original original data consisting of K ₁ bytes as shown in FIG. 7D is obtained.

By sequentially repeating the above process for each frame of the received data of FIG.
The original original data is reproduced as shown in (E). The reproduced data of FIG. 7E (differential data) is sent to the GPS receiver 12 via the RS232C transmission circuit 105.

The GPS receiver 12 subtracts the correction value given by the differential data from the positioning value calculated by its own GPS receiver 12. As a result, the mobile station 2 can obtain extremely accurate positioning data of the current position with the error corrected.

Although the above-mentioned embodiment illustrates the case where the present invention is applied to the differential GPS system, the application of the present invention is not limited to this.
It is applicable to any digital communication using a convolutional code, and is particularly useful in one-way communication.

Other target fields to which the present invention can be applied include, for example, commercial MCA wireless data transmission, personal computer communication, and wired / wireless (telephone, ship telephone, aircraft telephone, etc.) analog telephone lines. There are data communication used, teletype communication of Inmarsat C, telemeter communication, printing telegraph communication, various control communication (command transmission of television transmission device for helicopter, etc.), tracking data communication of tracking type optical wave range finder, and the like.

Further, although the transmission format as shown in FIG. 6 is adopted in the above embodiment, the transmission format as shown in FIG. 8 is also possible. In the case of the transmission format of FIG. 8, since the data size information K is located behind the encoded data, the received data cannot be processed sequentially in the order in which they are received. This can be realized by reading the coded data to be decoded according to the data size information K while storing it in the memory.

Furthermore, although the above embodiment uses the Hagelberger code as the convolutional code, it goes without saying that the same can be applied to other convolutional codes.

[0038]

As described above, according to the present invention, original data consisting of variable length data is encoded into variable length format data using a convolutional code, and the data size of the original data is convolved. Since it is encoded into fixed-length format data size information using an embedded code, and the encoded fixed-length format data size information is added to the encoded variable-length format data for transmission. It is possible to realize strong error correction by convolutional code and at the same time
It has an excellent effect that data can be efficiently transmitted in a variable length format.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of encoding according to the method of the present invention.

FIG. 2 is a conceptual explanatory diagram of a differential GPS system.

FIG. 3 is a block diagram of a differential GPS system.

FIG. 4 is a block diagram showing an embodiment of a data transmission modem device of a reference station configured by applying the method of the present invention.

FIG. 5 is a block diagram showing an embodiment of a data receiving modem device of a mobile station configured by applying the method of the present invention.

FIG. 6 is a diagram showing a data transmission format adopted in the embodiment.

FIG. 7 is an explanatory diagram of decoding according to the method of the present invention.

FIG. 8 is a diagram showing another example of the transmission format of the present invention.

FIG. 9 is an explanatory diagram of conventional encoding.

FIG. 10 is a diagram showing a transmission format of a conventional system.

[Explanation of symbols]

 1 Reference Station 2 Mobile Station 3 GPS Reception Antenna 4 GPS Receiver 5 Data Transmission Modem Device 6 Radio Transmitter 7 Data Transmission Antenna 8 Data Reception Antenna 9 Radio Receiver 10 Data Reception Modem Device 11 GPS Reception Antenna 12 GPS receiver 51 RS232C receiver circuit 52 Data byte number integration unit 53 Data size Hargelberger encoding circuit 54 Data Hargelberger encoding circuit 55 Transmission data creation circuit 56 MSK modulation circuit 101 MSK demodulation circuit 102 Data size hardware Gelberger Decoding Circuit 103 Data Acquisition Circuit 104 Data Hagelberger Decoding Circuit 105 RS232C Transmission Circuit

Claims (1)

[Claims] 1. Data size information of a fixed-length format is encoded by using a convolutional code, while encoding original data composed of variable-length data into data of a variable-length format by using a convolutional code. And transmitting the encoded variable length format data by adding the encoded fixed length format data size information to the encoded variable length format data.