JPH0865272A - Communication system - Google Patents

Abstract

PURPOSE: To provide the communication system with which transmission quality can be improved without increasing the number of redundant bits and increasing signal throughput while simplifying configuration as well. CONSTITUTION: A transmitter 7 respectively allocates a peculiar multiplexed/ demultiplexed code to an information signal and a control signal, multiplexes the information signal and the control signal with algebraic arithmetic using the multiplexed/demultiplexed code and transmits this multiplexed signal to a transmission line 9. On the other hand, a receiver 8 receives the multiplexed signal from the transmission line 9 and demultiplexes this multiplexed signal into the information signal and the control signal with algebraic arithmetic using the multiplexed/demultiplexed code. Then, waveform distortion caused by the transmission line 9 is calculated based on the demultiplexed control signal, and the demultiplexed information signal is compensated based on the calculated waveform distortion.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to communication systems.

[0002]

2. Description of the Related Art Generally, in a digital communication system, an equalizer is used in order to compensate for distortion generated on a transmission line and improve transmission quality. Further, in order to further improve the transmission quality, an error correction code may be used together.

FIG. 5 is a diagram showing the configuration of a communication system using an equalizer and an error correction code. As shown in the figure,
The transmitter 1 and the receiver 2 are connected via a transmission line 3, the transmitter 1 is provided with an encoder 4, and the receiver 2 is provided with an equalizer 5 and a decoder 6.

The equalizer 5 has an adaptive filter, estimates the characteristics of the transmission line 3, and compensates for the distortion of the signal that has passed through the transmission line 3. In addition, as a control algorithm of the equalizer 5,
The least squares method and the like are widely used.

In the error correction code, the encoder 4 is used at the time of transmission.
Thus, the redundant bits for error correction are added to the information bits as the transmission information for decoding, and at the time of reception, the decoder 6 corrects the code error of the information bits based on the redundant bits. For example, in the (7,4) Hamming code, 4
A redundant bit of 3 bits is added to the bit information to generate a transmission bit of 7 bits, and an error correction of 1 bit out of 7 bits is possible on the receiving side. The (7,4) Hamming code is described in detail, for example, in "Hideki Imai," Code Theory ", Chapter 4, Corona Publishing Co., Ltd. (1990)".

However, a communication system using such an equalizer and an error correction code has the following problems.

First, since the equalizer requires a higher degree of adaptive control algorithm as the characteristics of the transmission line change faster, the amount of signal processing increases when the equalizer is used in a communication system having a transmission path whose characteristics change rapidly. Then, there is a problem that the circuit is hindered.

Further, in the error correction code, the error correction capability increases as the number of redundant bits increases, but there is a problem that the bit rate increases and the amount of signal processing for decoding also increases.

[0009]

As described above, in the conventional communication system, the equalizer and the error correction code are used to improve the transmission quality, but the equalizer speeds up the response. As a result, the signal processing amount increases, and in the error correction code, the more the correction capability is improved, the more redundant bits increase and the signal processing amount also increases.

Therefore, an object of the present invention is to provide a communication system capable of improving the transmission quality without increasing the redundant bits and the signal processing amount, and with a simple structure.

[0011]

In order to solve such a problem, the invention according to claim 1 is a transmitter provided with means for multiplexing an information signal and a control signal and transmitting the multiplexed signal to a transmission line. And means for receiving a multiplexed signal from the transmission line and separating the multiplexed signal into an information signal and a control signal,
The receiver is provided with means for obtaining a waveform distortion due to the transmission line based on the separated control signal, and means for compensating the separated information signal based on the obtained waveform distortion.

According to a second aspect of the present invention, a unique demultiplexing code is assigned to each of the information signal and the control signal, and the information signal and the control signal are multiplexed by an algebraic operation using the demultiplexing code. And a means for receiving a multiplexed signal from the transmission path and separating the multiplexed signal into an information signal and a control signal by algebraic operation using the demultiplexing code. And a receiver including means for obtaining a waveform distortion due to the transmission line based on the separated control signal, and means for compensating the separated information signal based on the obtained waveform distortion.

According to a third aspect of the present invention, a unique demultiplexing code is assigned to each of the information signal and the control signal composed of the periodic signal, and the information signal and the control signal are multiplexed by algebraic calculation using the demultiplexing code. A transmitter equipped with means for transmitting the multiplexed signal to a transmission line, and an information signal and a control signal that receive the multiplexed signal from the transmission line and perform an algebraic operation on the multiplexed signal using the demultiplexing code. Means for separating, a means for generating a phase synchronization signal in phase with the separated control signal, a means for obtaining a difference between the separated control signal and the phase synchronization signal, and based on the obtained difference A receiver comprising means for compensating the separated information signal.

According to a fourth aspect of the present invention, the Chinese remainder theorem using the demultiplexing code for the information signal and the control signal, each of which is assigned a unique demultiplexing code composed of mutually prime integers. Multiplex by calculation based on
A transmitter having means for transmitting the multiplexed signal to a transmission line, and an information signal and a control signal which are received by the transmission line from the transmission line and which are modularly modulo the demultiplexing code. Means for separating into, and means for obtaining waveform distortion due to the transmission path based on the separated control signal,
A receiver having means for compensating the separated information signal based on the obtained waveform distortion.

According to a fifth aspect of the invention, a Chinese remainder theorem using the demultiplexing codes for the information signal and the control signal, and the demultiplexing codes for the information signal and the control signal are assigned to the respective demultiplexing codes. Multiplex by calculation based on
A transmitter having means for transmitting the multiplexed signal to a transmission line, and an information signal and a control signal which are received by the transmission line from the transmission line and which are modularly modulo the demultiplexing code. And means for generating a phase synchronization signal in phase with the separated control signal, means for obtaining a difference between the separated control signal and the phase synchronization signal, and based on the obtained difference And a receiver having means for compensating the separated information signal.

[0016]

According to the present invention, the transmitter allocates, for example, unique demultiplexing codes to the information signal and the control signal, respectively, and multiplexes the information signal and the control signal by algebraic operation using the demultiplexing code. The signal is transmitted to the transmission line.

On the other hand, the receiver receives the multiplexed signal from the transmission line and separates the multiplexed signal into an information signal and a control signal by algebraic calculation using a demultiplexing code. Then, the waveform distortion due to the transmission line is obtained based on the separated control signal,
The information signal separated based on the obtained waveform distortion is compensated.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

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

In the communication system shown in the figure, a transmitter 7 and a receiver 8 are connected via a transmission line 9.

The transmitter 7 is provided with a multiplexer 10 and a D / A converter 11.

The receiver 8 includes an A / D converter 12, a separator 13, a digital phase locked loop (DPLL) 14, and 90 °.
A phase shifter 15, a subtractor 16 and a subtractor 17 are provided. In the present embodiment, the demultiplexing by the multiplexer 10 and the demultiplexer 13 is performed by the demultiplexing method based on the Chinese Remainder Theorem and based on the algebraic operation of integers.

FIG. 2 is an explanatory diagram of this demultiplexing method.

In multiple operations, xj (n) (j = 1,2, ..., L,
n is the sample number and xj (n) is the nth sample signal. )
The L integer signals represented by are multiplexed.

First, the demultiplexing code pj (j = j) is added to xj (n).
1, 2, ..., L) are assigned respectively. Where pj is x
It is a relatively prime integer greater than j (n).

Then, the multiple signal X (n) is obtained by using the following conversion equations (1) to (6).

[0027]

[Equation 1] On the other hand, in the separation operation, xj (n)
Is separated.

[0028]

[Equation 2] The information signal x1 (n) which is a modulation signal such as PSK and the control signal x2 (n) which is a sine wave of a constant frequency are input to the multiplexer 10 shown in FIG. Note that x1 (n) and x2 (n)
Are both integerized signals. Further, in the multiplexer 10, the demultiplexing codes p1 and p2 which are mutually prime to x1 (n) and x2 (n) are assigned in advance.

The multiplexer 10 generates a multiplexed signal X (n) from x1 (n) and x2 (n) using the above-mentioned conversion formulas (1) to (6). Then, the D / A converter 11 converts the multiplexed signal X (n), which is a digital signal, into an analog signal and sends it to the transmission line 9.

In the receiver 8 which has received the multiplex signal X (n) from the transmission line 9, first, the A / D converter 12 converts the multiplex signal X (n), which is an analog signal, into a digital signal and converts it into an integer. The separator 13 performs the separation operation from the multiplex signal X (n) using the above-mentioned equation (7). In the demultiplexer 13, the demultiplexing codes p1 and p2 described above are already known.

Here, assuming that waveform distortion is generated in the transmission line 9, the signal x1 (n) 'separated by the separator 13 is
x2 (n) 'is when the product of p1 and p2 is odd

(Equation 3) Becomes

The above equations (9) and (11) are the dynamic range of processing.

However, D (n) is an integerized waveform distortion.

The signal x2 (n) 'separated by the separator 13 is D
It is input to the PLL 14.

The DPLL 14 is a feedback control loop that outputs a signal in phase with the input periodic signal and has a noise suppressing effect. That is, DPLL14
Can be said to be a narrow band tracking filter.

FIG. 3 is a diagram showing the configuration of such a DPLL 14.

As shown in the figure, the DPLL 14 comprises a phase comparator 18 composed of a multiplier, a loop filter 19 composed of a digital filter, and a voltage controlled oscillator 22 composed of a digital integrator 20 and a cosine wave ROM 21. Consists of

Here, the transfer function of the digital filter of the loop filter 19 is, for example, by Z conversion,

[Equation 4] It is expressed as

Similarly, the transfer function of the digital integrator 20 of the voltage controlled oscillator 22 is

(Equation 5) It is expressed as

When the input signal of the DPLL 14 is V1 (n),

(Equation 6) It is expressed as

At this time, the DPLL 14 outputs the input signal V1 (n).
When synchronized with the input signal V1 (n), the output signal V2 (t) becomes
And the angular frequency is equal

(Equation 7) Is obtained.

Here, if the perfect integral digital filter of the equation (12) is used as the loop filter 19,
Even when there is a constant angular frequency offset between the input signal and the output signal in the initial state, the output signal of the DPLL 14 is synchronized at the same angular frequency as the input signal when the phase relationship between the input signal and the output signal is 90 °. To do. Further, even when the input signal is not only a periodic signal but also includes distortion, noise, etc., if the DPLL 14 is designed to have a narrow band characteristic, a periodic signal with suppressed distortion and noise can be obtained.

In the present embodiment, since x2 (n) is a sinusoidal periodic signal, the DPLL 14 easily synchronizes with x2 (n) '. Therefore, the DPLL 14 outputs a signal in which the phase is shifted by 90 ° in synchronization with x2 ', distortion and noise are suppressed.

Here, the output level of the DPLL 14 is x
When the ROM of the voltage controlled oscillator 22 of the DPLL 14 is set to be equal to the level of 2 (n), if the output signal of the DPLL 14 is phase-shifted by 90 ° by the 90 ° phase shifter 15, x2 (n) will be obtained. Can be played.

Then, from the relation of the equation (10), the subtracter 1
The distortion D (n) generated in the transmission line 9 is obtained by the method 6.

Therefore, from the relation of the equation (8), the subtracter 17
Thus, the transmission signal x1 (n) whose distortion is suppressed is reproduced.

As described above, in the communication system of this embodiment,
Although the transmission signal band is expanded due to the multiplexing of the control signals, the magnitude of the transmission line fluctuation satisfies the dynamic range of the processing shown in the equations (9) and (11), and the DPLL is maintained during the fluctuation.
When the parameter is set so that 14 keeps the synchronization, the waveform distortion is compensated and the error correction becomes possible.

Therefore, in the communication system of this embodiment, it is possible to improve the transmission quality without increasing the redundant bits and the signal processing amount as in the conventional case, and with a simple structure. .

The present invention is not limited to the above embodiment.

For example, in the above-described embodiment, the transmission control signal is a sine wave, and the correct value of the transmission control signal is obtained from the output signal of the DPLL 14. However, when the sine wave is not used for the transmission control signal, FIG. As shown, the desired known transmission control signal value x2 (n) can be used to compensate for the distortion to obtain the correct information signal x1 (n). In that case, the timing of compensation is obtained from the DPLL 14 and the timing controller 2
It is also possible to control by 3.

Further, in the above-mentioned embodiment, as the demultiplexing codes p1 and p2, the mutually prime integers whose odd product is an odd odd number of the products of p1 and p2 are selected. . In that case, the dynamic range of the signal processing of equations (9) and (11) is

[Equation 8] Becomes

Further, in the above-described embodiment, one series of information signals and one series of control signals are demultiplexed, but both are 1
It is not limited to the series.

[0053]

As described above, according to the communication system of the present invention, it is possible to improve the transmission quality with a simple configuration without increasing the redundant bits and the signal processing amount. Can be planned.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining an algebraic demultiplexing method used in the present invention.

FIG. 3 is a diagram showing a configuration of the DPLL shown in FIG.

FIG. 4 is a diagram showing a configuration of a communication system according to another embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional communication system using an equalizer and an error correction code.

[Explanation of symbols]

 7 ... Transmitter 8 ... Receiver 9 ... Transmission line 10 ... Multiplexer 11 ... DA converter 12 ... AD converter 13 ... Separator 14 ... DPLL 15 ……… 90 ° phaser 16, 17 ……… Subtractor

Claims (5)

[Claims] 1. A transmitter having means for multiplexing an information signal and a control signal and transmitting the multiplexed signal to a transmission line, and a multiplexed signal received from the transmission line, the multiplexed signal being used as information. A signal and a control signal, means for obtaining the waveform distortion due to the transmission line based on the separated control signal, and means for compensating the separated information signal based on the obtained waveform distortion. A communication system comprising a receiver. 2. A unique demultiplexing code is assigned to each of the information signal and the control signal, the information signal and the control signal are multiplexed by an algebraic operation using the demultiplexing code, and the multiplexed signal is transmitted to the transmission line. A transmitter having means, means for receiving a multiplexed signal from the transmission path, and means for separating the multiplexed signal into an information signal and a control signal by algebraic operation using the demultiplexing code; and the separated control. A communication system comprising: a receiver including means for obtaining a waveform distortion due to the transmission line based on a signal; and means for compensating the separated information signal based on the obtained waveform distortion. 3. A unique demultiplexing code is assigned to each of the information signal and the control signal composed of a periodic signal, the information signal and the control signal are multiplexed by algebraic operation using the demultiplexing code, and the multiplexed signal is transmitted. A transmitter having means for transmitting to a path, means for receiving a multiplexed signal from the transmission path, and separating the multiplexed signal into an information signal and a control signal by algebraic operation using the demultiplexing code, Means for generating a phase synchronization signal whose phase is synchronized with the separated control signal, means for obtaining a difference between the separated control signal and the phase synchronization signal, and the separated information signal based on the obtained difference And a receiver having means for compensating the communication system. 4. An information signal and a control signal are each assigned a unique demultiplexing code composed of mutually prime integers, and the information signal and the control signal are multiplexed by an operation based on the Chinese Remainder Theorem using the demultiplexing code. A transmitter provided with means for transmitting the multiplexed signal to a transmission line, and receiving the multiplexed signal from the transmission line and controlling the multiplexed signal with an information signal by a remainder operation modulo the demultiplexing code. A receiver that includes means for separating into a signal, means for obtaining a waveform distortion due to the transmission line based on the separated control signal, and means for compensating the separated information signal based on the obtained waveform distortion. A communication system comprising: 5. The information signal and the control signal are each assigned a unique demultiplexing code composed of mutually prime integers, and the information signal and the control signal are multiplexed by an operation based on the Chinese Remainder Theorem using the demultiplexing code. A transmitter provided with means for transmitting the multiplexed signal to a transmission line, and receiving the multiplexed signal from the transmission line and controlling the multiplexed signal with an information signal by a remainder operation modulo the demultiplexing code. Means for separating into a signal, means for generating a phase synchronization signal in phase with the separated control signal, means for obtaining a difference between the separated control signal and the phase synchronization signal, and the obtained difference And a receiver having means for compensating the separated information signal on the basis of the communication system.