JPH0879221A - Data transmission system - Google Patents

Abstract

PURPOSE: To provide a data transmission system capable of transmitting data provided with an optional transmission speed and obtaining high line quality. CONSTITUTION: A timing information generation circuit 11 generates timing information for taking a value '1' when a generation timing pulse and a transmission timing pulse match when they are compared and taking the value '0' in the other case. An encoding circuit 13 convolution-encodes the transmission data and the timing information and outputs encoded signals, a transmitter 12 fetches and transmits the encoded signals based on the transmission timing pulse and a receiver 14 receives the encoded signals and supplies them to a most likelihood decoding circuit 15. The most likelihood decoding circuit 15 decodes the encoded signals and separates the transmission data and the timing information from the signals. A data timing generation circuit 16 extracts the generation timing pulse based on the timing that the timing information takes the value '1' and a retiming circuit 17 retimings the transmission data by using the generation timing pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system for transmitting transmission data having different transmission rates using the same transmission device having a constant transmission rate.

[0002]

2. Description of the Related Art In a conventional data transmission system for transmitting transmission data having different transmission rates using the same transmission device having a constant transmission rate, a plurality of encoding circuits having different transmission efficiencies and respective encoding circuits are provided. By preparing in advance a plurality of decoding circuits corresponding to, and selecting an encoding circuit and a decoding circuit suitable for the transmission rate of the transmission data, by using the same transmission device for transmission data having different transmission rates. It was transmitting.

FIG. 7 shows an example of the configuration of such a conventional data transmission system. In this figure, 1 ₁ and 1 ₂
Are transmission efficiency (N / M) and (N '/ M'), respectively.
Of the plurality of registers 2a and 2a, respectively.
, and registers 2b, 2b ,. 3 ₁ and 3 ₂ are coding circuit changeover switches.
Reference numeral 4 is a transmission device composed of a transmitter 5 and a receiver 6, and always transmits transmission data at the same transmission rate. Also,
Reference numerals 7 ₁ and 7 ₂ are decoding circuits corresponding to the encoding circuits 1 ₁ and 1 ₂ , respectively, and 8 ₁ and 8 ₂ are decoding circuit changeover switches.

Next, the operation of the data transmission system shown in FIG. 7 will be described. The transmission rate of the transmission data D _{0 to} D _n to be transmitted is compared with the transmission rate of the transmission device 4, and the set of the encoding circuit 1 ₁ and the decoding circuit 7 ₁ having the corresponding transmission efficiency, or the encoding circuit. 1 ₂ and decoding circuit 7 ₂
Is selected, and the encoding circuit changeover switches 3 ₁ and 3 ₂ and the decoding circuit changeover switches 8 ₁ and 8 ₂ are changed over accordingly. As a result, the transmission data D ₀ to
D _n is input to the encoding circuit 1 ₁ or 1 ₂ via the encoding circuit changeover switch 3 ₁ , is encoded by the input encoding circuit, and then is input via the encoding circuit changeover switch 3 _2. It is input to the transmission device 4. In the transmitter 4, which is input via the encoding circuit changeover switch 3 _2, after the transmission data encoded is transmitted by transmitter 5 and received by the receiver 6. The transmission data received by the receiver 6 is input to the decoding circuit 7 ₁ or 7 ₂ via the decoding circuit changeover switch 8 ₁ , and the original decoding data D _{0 to} D _n is input by the input decoding circuit. After being decrypted into, it is output via the decryption circuit changeover switch 8 ₂ .

[0005]

By the way, in the above-mentioned conventional data transmission system, the encoding circuits 1 ₁ ,
For 1 ₂ , for example, it is possible to select a transmission efficiency having an integer ratio such as 1/2, 2/3, but it is not possible to select a transmission efficiency that does not have an integer ratio. Therefore, there is a drawback that it is impossible to transmit the transmission data having an arbitrary transmission rate that does not match the above-mentioned transmission efficiency.
Further, in the above-mentioned conventional data transmission system,
Before transmitting the transmission data D _{0 to} D _n , the encoding circuit changeover switches 3 ₁ and 3 ₂ and the decoding circuit changeover switches 8 ₁ and 8 ₂ are transmitted.
Need to switch at the same time. However, usually
Encoding circuits 1 ₁ , 1 ₂ , encoding circuit changeover switches 3 ₁ , 3 ₂
The transmitter 5 and the transmitter 5, and the receiver 6 and the decoding circuits 7 ₁ and 7 ₂ and the decoding circuit changeover switches 8 ₁ and 8 ₂ are installed apart from each other. Therefore, there is a drawback that the switching signal for controlling the switching of the coding circuit changeover switches 3 ₁ and 3 ₂ and the decoding circuit changeover switches 8 ₁ and 8 ₂ must be transmitted by a transmission means different from the transmission device 4. there were. Further, when switching the encoding circuit changeover switches 3 ₁ and 3 ₂ and the decoding circuit changeover switches 8 ₁ and 8 ₂ , there is a problem that high line quality cannot be obtained because a momentary interruption occurs.

The present invention has been made under such a background, and an object thereof is to provide a data transmission system capable of transmitting transmission data having an arbitrary transmission rate and obtaining a high line quality.

[0007]

SUMMARY OF THE INVENTION The present invention provides a data transmission system for transmitting transmission data having different transmission rates by using the same transmission device having a constant transmission rate, the generation timing pulse of the transmission data, and The transmission timing pulse output from the transmission device is compared, and timing information having a first value when the generation timing pulse and the transmission timing pulse match, and a second value otherwise is generated. A timing information generating circuit, a coding circuit for convolutionally coding the transmission data and the timing information together and outputting a coded signal, and the transmission device, wherein the coded signal is based on the transmission timing. A transmitter for receiving and transmitting the encoded signal, the receiver constituting the transmitting device, receiving the transmitted encoded signal, and the code A maximum likelihood decoding circuit that performs maximum likelihood decoding of a signal and separates and outputs transmission data and timing information from the decoded signal, and the generation timing of the transmission data based on the timing when the timing information has a predetermined value A timing generation circuit that extracts and outputs a pulse,
And a retiming circuit for retiming the transmission data using the extracted generation timing pulse.

[0008]

According to the above construction, the timing information generation circuit compares the generated timing pulse with the transmission timing pulse, and takes the first value when they match, and takes the second value in other cases. Generate timing information.
As a result, the encoding circuit convolutionally encodes the transmission data and the timing information together and outputs the encoded signal, so that the transmitter acquires and transmits the encoded signal based on the transmission timing. On the other hand, when the receiver receives the coded signal transmitted from the transmitter, the maximum likelihood decoding circuit performs maximum likelihood decoding of the coded signal, and separates the transmission data and the timing information from the decoded signal and outputs them. The timing generation circuit extracts and outputs the generation timing pulse of the transmission data based on the timing when the timing information takes a predetermined value. As a result, the retiming circuit retimes the transmission data using the extracted generation timing pulse.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a data transmission system according to an embodiment of the present invention. In this figure,
The timing information generation circuit 11 generates timing pulses a ₀ , a ₁ , ..., A _k , ... A _n (0) of the transmission data D ₀ , D ₁ , ..., D _k , ... D _n to be transmitted. ≤k≤n), and transmission timing pulses b ₀ , b ₁ , ..., b _p , ... b _m (0 ≤ p ≤ m) output from the transmitter 12 constituting the transmission device.
And the parity signals P ₀ , P ₁ , ... Which take the value “1” when the generation timing pulse a _k and the transmission timing pulse b _p match, and take the value “0” in other cases.
, P _k , ... P _n are generated as timing information. The coding circuit 13 performs convolutional coding on the transmission data D _{0 to} D _n and the timing information (parity signals) P _{0 to} P _n together to code the signals S ₀ , S ₁ , ..., S _k ,. Output S _n . The transmitter 12 takes in the encoded signals S _{0 to} S _n based on the transmission timing pulses b _{0 to} b _m of the transmission device and transmits them to the receiver 14 which also constitutes the transmission device.

The receiver 14 receives the transmitted encoded signal S _0.
After receiving ~ S _n , the maximum likelihood decoding circuit 15 is supplied. The maximum likelihood decoding circuit 15 performs maximum likelihood decoding of the coded signals S _{0 to} S _n ,
From the decoded signal transmission data D _'0 to D' _n and timing information P _'0 to P' separates the _n outputs. Data timing generating circuit 16, timing information P _'0 ~P' _n is a value "
Based on the timing of taking 1 ", the transmission data D' _0-
D 'generation timing pulse of _{n a' 0, a '1} , ......, a' k,
... _a'n (0≤k≤n) is extracted and output. The retiming circuit 17 outputs the extracted generation timing pulse a ′ _0.
The ₀ to D _'n and retiming outputs the received data D ₀ to D _n' transmission data D with _n '~a.

Here, FIG. 2 shows a diagram for explaining an example of an algorithm for generating the timing information P _{0 to} P _n in the timing information generating circuit 11. As can be seen from FIG. 2, the timing information P _{0 to} P _n is the transmission data D.
₀ and to D _n generated timing pulse a ₀ ~a _n of takes a value "1" only if the transmission timing pulses b ₀ ~b _m matches, one parity takes a value "0" in other cases It is a signal.

Next, FIG. 3 shows a convolutional code (r = 3 /
4, k = 2, (40 56 63 74)). In this figure, 21 is each state of the encoding circuit 13. Further, FIG. 4 shows the state transitions of the coded signals S _{0 to} S _{n obtained} by simultaneously coding the timing information P _k and the transmission data D _k in the coding circuit 13. When the timing information P _k takes the value “0”, the transmission data D _k does not change, and it can be seen from FIG. 4 that the state transition of the code is restricted (state transition is deleted). As a result, according to this embodiment, the error correction effect is increased, and the error correction effect according to the timing period ratio can be obtained.

As described above, according to the data transmission system of the present embodiment, it is possible to transmit the transmission data having an arbitrary transmission rate, and the line can be transmitted without any interruption depending on the importance of the transmission data. You can get quality.

By the way, the error correction capability increases as the transmission speed becomes slower than the transmission timing speed. Therefore, by delaying the transmission timing of a portion of the transmission data where the importance of information is high, efficient signal transmission becomes possible. FIG. 5 shows a configuration example of a data transmission system in which the transmission timing speed is changed according to the importance of information. In FIG. 5, 31 is a data transmission terminal, 32 is a data importance detection circuit, 33 is a transmission rate control circuit, b _p is a transmission timing pulse, 34 is the data transmission system according to the above-described embodiment, and D ″ _k is transmission. It is transmission data that has been improved in line quality according to the importance of data. Further, FIG. 6 shows the relationship between the importance of the transmission data D _k and the transmission timing b _p in FIG. 5, and in this figure, reference numeral 35 indicates a portion of the transmission data D _k where important data is present. Shows. As can be seen from FIG. 6, by delaying the transmission timing for transmission data having important information, the error correction capability is increased and the line quality is improved.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and the design is modified within the scope not departing from the gist of the present invention. Even so, it is included in the present invention. For example, the data transmission system according to the above-described embodiment can make the transmission rate of transmission data asynchronous with the transmission rate of the transmission device, and thus can be applied to a transmission system that easily performs start-stop synchronization.

[0016]

According to the present invention, transmission data having an arbitrary transmission rate can be transmitted and high line quality can be obtained. In addition, since there is no switching portion, instantaneous interruption due to switching does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a data transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a timing information generation algorithm of the timing information generation circuit 11 shown in FIG.

FIG. 3 is a diagram showing an example of a state transition of a convolutional code in the data transmission system shown in FIG.

FIG. 4 is a diagram showing an example of a state transition of an encoded signal when timing information and transmission data are encoded at the same time in the data transmission system shown in FIG.

5 is a block diagram showing an application example of the data transmission system shown in FIG.

6 is a diagram showing the relationship between the importance of transmission data and transmission timing in the data transmission system shown in FIG.

FIG. 7 is a block diagram showing a configuration example of a conventional data transmission system.

[Explanation of symbols]

 11 timing information generation circuit 12 transmitter 13 encoding circuit 14 receiver 15 maximum likelihood decoding circuit 16 data timing generation circuit 17 retiming circuit

Claims (1)

[Claims] 1. A data transmission system for transmitting transmission data having different transmission rates by using the same transmission apparatus having a constant transmission rate, wherein a generation timing pulse of the transmission data and a transmission timing output from the transmission apparatus. The pulse is compared, and the first value is obtained when the generation timing pulse and the transmission timing pulse match, and the second value is obtained in other cases.
A timing information generation circuit that generates timing information that takes a value of; a coding circuit that convolutionally codes the transmission data and the timing information together and outputs a coded signal; A transmitter that takes in and transmits a coded signal based on the transmission timing, a receiver that configures the transmission device, receives the transmitted coded signal, and performs maximum likelihood decoding of the coded signal and decodes the coded signal. A maximum likelihood decoding circuit that separates and outputs transmission data and timing information from a signal, and a timing generation circuit that extracts and outputs a generation timing pulse of the transmission data based on the timing when the timing information takes a predetermined value And a retiming circuit for retiming the transmission data using the extracted generation timing pulse. Over data transmission system.