RU2317642C2 - Method for encoding a digital signal for information transmission - Google Patents

Abstract

FIELD: devices for encoding a digital signal for information transmission, possible use in communications engineering.

SUBSTANCE: in accordance to the invention to the method for encoding a digital signal for information transmission purposes, digital signal is transformed to a form characterized by absence of constant component during transmission of long series of ones and zeroes by encoding the original information signal, where encoding is conducted according to signal level, during encoding each byte of the original digital signal is divided on two bytes - even one and odd one, where even byte is produced from byte of original digital signal by zeroing odd bits in it, and odd byte is produced by zeroing of all even bits in it, where in even byte each bit of information is conveyed by inverse value of even bit, recorded in place of neighboring zeroed odd bit of zeroing and direct value of even bit, and in odd byte every bit of information is conveyed through direct value of odd bit and inverse value of odd bit, recorded in place of adjacent zeroed even bit, where all manipulations are realized by programming means.

EFFECT: ensured encoding of digital signal for interference-resistant transmission of information by software means with relatively low load on processor.

2 dwg

Description

The invention relates to means for encoding a digital signal for transmitting information and can be used in communication technology.

It is known that digital data transmission requires several mandatory operations:

- synchronization of the clock frequency of the transmitter and receiver;

- converting a sequence of bits into an electrical signal;

- reducing the frequency of the spectrum of the electrical signal using filters;

- transmission of the truncated spectrum over the communication channel;

- amplification of the signal and restoration of its shape by the receiver;

- conversion of an analog signal to digital.

The relationship between the clock frequency and the bit sequence is as follows.

The bitstream is transmitted at a speed determined by the number of bits per unit time, where the number of bits per second is the number of discrete changes in the signal per unit time. The clock frequency in hertz is the number of sinusoidal changes in the signal per unit time.

A known encoding method for digital data transmission using the RZ code (see. Appendix to the application).

The known method is that they use a three-level code in which the signal is encoded with a return to zero (Return to Zero), where a positive impulse corresponds to a logical zero, and a negative impulse corresponds to a logical one. The information transition is carried out at the beginning of the bit, return to zero - in the middle of the bit. Since there is always a transition (positive or negative) in the center of the bit, each bit is indicated. The receiver can extract a clock (strobe) having a pulse repetition rate from the signal itself. The binding is made to each bit, which ensures the synchronization of the receiver with the transmitter. This is a self-synchronizing code, as it carries a strobe.

A disadvantage of the known code is that it does not give a gain in data transfer rate, requiring a high frequency (10 MHz requires 10 MHz for a speed of 10 Mbps). In addition, to distinguish between three levels, a better signal-to-noise ratio at the input to the receiver is needed than for two-level signals.

There is a known encoding method for digital signal transmission, described in p. RF No. 2205518 "Method for generating signals with quadrature phase modulation" according to class. H04L 27/20, c. 12/11/01, publ. 05/27/03. The known method consists in splitting the carrier oscillation into in-phase and quadrature oscillations, generating in-phase and quadrature harmonic signals by dividing the frequency of the in-phase and quadrature oscillations by (4k + 1) times, where k is an integer, shift the manipulating video signals by half the symbol duration so that the phases of the in-phase and quadrature harmonic signals coincide with the phases of the in-phase and quadrature oscillations, respectively, at the beginning and at the end of each symbol, the in-phase and quadrature are manipulated 180 phase oscillations by 180 ° manipulating video signals, produce a balanced modulation of in-phase and quadrature binary-manipulated oscillations in-phase and quadrature harmonic.

The disadvantage of this method is the complexity of the circuitry and hardware implementation.

There is a method of modulating a digital signal for transmitting data over narrowband telecommunication channels, described in the same patent of the Russian Federation No. 2210192 in class. H04L 27/20, H04B 14/04, s. 03/10/2001, publ. 08/10/2003. The known method consists in modulating a digital signal with a bi-pulse code, changing the phase of the carrier signal during the transition from encoding a logical 0 modulated digital signal to encoding a logical 1 modulated digital signal, and vice versa, and only two-bit and one-bit transmissions are present in the modulated signal, and the duration two-bit sending refers to the duration of a single-bit sending as 1.5: 1, and with each phase jump of the carrier signal, the phase changes by minus 90 °.

The disadvantage of this method is the implementation complexity associated with the use for encoding a bi-pulse code and receiving packages of different durations, using hardware - a DAC microprocessor.

Closest to the technical nature of the claimed is the encoding method of Manchester, described in the attached description of encoding methods. The Manchester Code is characterized in that it does not have a constant component when transmitting a long sequence of ones or zeros. It is also a self-synchronizing code, but has two levels and provides better noise immunity. Each bit of information is encoded by a direct and inverse value - a logical zero corresponds to a transition to the upper level in the center of the bit interval, a logical unit corresponds to a transition to the lower level, i.e. encoding is carried out by the transition of a signal from one level ("0" or "1") to another. The Manchester code is obtained by generating a strobe, which is then summed modulo 2 with the encoded signal, receiving a signal for transmission.

A disadvantage of the known encoding method is that it is carried out, as a rule, by circuit means using additional strobe pulses. Since its decoding is carried out according to the transitions from “0” to “1” and from “1” to “0”, any interference, even of a very short duration, can lead to incorrect reception of the entire subsequent code. If you generate the Manchester code by software, then by encoding each bit of information with two bits, there is a large processor load and a long signal transmission time, since the processor must programmatically process each bit when transmitting data.

The objective of the invention is to provide the ability to encode a digital signal for noise-free transmission of information by software with a relatively small processor load. This goal is achieved by the fact that in the method of encoding a digital signal for transmitting information, namely, that the digital signal is converted to a form characterized by the absence of a constant component when transmitting a long sequence of ones and zeros by logically encoding each bit of the original information signal, according to the invention, the encoding by signal level, when encoding, each byte of the original digital signal is divided into two bytes - even and odd, while the even byte is the floor read from the original digital signal by zeroing out the odd bits in it, and odd by zeroing out the even bits in it, and in an even byte, each bit of information is transmitted with the inverse value of the even bit written to the place of the neighboring zeroed odd bit and the direct value of the even bit, and in the odd byte each bit of information is transmitted by the direct value of the odd bit and the inverse value of the odd bit recorded in the place of the neighboring zeroed even bit, while all signal manipulations are carried out by software.

Performing coding according to the signal level by dividing each byte into two even and odd, with zeroing in the even byte of odd bits, and in the odd byte of even bits, with subsequent transmission in the even byte of each bit of information with the inverse value of the even bit written to the place of the neighboring zeroed the odd bit, in the odd bit - by transmitting each bit with the direct value of the odd bit and the inverse value of the odd bit recorded in the place of the neighboring zeroed odd bit, it allows you to program encoding ohm with high noise immunity due to the transmission of each bit of data by two bits and, if necessary, the correction of errors in the transmission of information about the parity or oddness of the transmitted bytes in the data during simple manipulations with the signal that do not require a large processor load.

The signal is encoded and then decoded according to the level, and not according to the transition from “0” to “1” and from “1” to “0”. This ensures its higher immunity from impulse noise. Transmission is byte-by-byte and failure of one bit does not distort subsequent data. The noise immunity of the code is also enhanced by duplicating the transmission of each bit. Bytes encoded in this way can be transmitted and received using the standard serial interface, which is available in most existing microcontrollers. EFFECT: obtaining a code that does not have a constant component, in which the transmission of each bit by direct and inverse values is duplicated without special circuit solutions by software, simple signal manipulations that do not take much time and do not load the processor.

The inventive method has a novelty in comparison with the prototype, differing from it in such essential features as dividing the original digital signal into two bytes - even and odd, getting an even byte from the original, zeroing the odd bits in it, and odd - zeroing the even bits in the original byte , then duplicating each even bit in an even byte, writing it to the place of the neighboring zeroed odd bit and inverting it, duplicating each odd bit in the odd byte and writing it to the neighboring zeroed even bit and inverting it, providing a plurality of achieving the desired result.

The applicant is not aware of technical solutions that have the indicated distinguishing features, which together ensure the achievement of a given result, therefore, he believes that the claimed method meets the criterion of "inventive step".

The inventive method of encoding a digital signal for transmitting information can be widely used for data transmission over the air, transmission over the current loop, etc., therefore, meets the criterion of "industrial applicability".

The inventive method is illustrated by the diagrams shown in figure 1 and 2, which presents respectively the odd and even bytes of the signal (in digital and analog form).

The inventive method of encoding a digital signal for transmitting information is as follows.

The digital signal is converted to a form characterized by the absence of a constant component when transmitting a long sequence of ones and zeros by logical coding of the signal level of each bit of the original information signal with two bits - the original and its inverse value. To do this, the original digital signal is divided into two bytes - even and odd, in one of which each bit of information is represented by direct and inverse values, and in the other by inverse and direct values. In this case, an even byte is obtained from the original by zeroing out the odd bits in it, and an odd byte - by zeroing out the even bits in the original byte. In an even byte, each bit of information is transmitted with the inverse value of the even bit written to the place of the neighboring zeroed odd bit and the direct value of the even bit, and in the odd byte, each bit of information is transmitted with the direct value of the odd bit and the inverse value of the odd bit written to the place of the neighboring zeroed even bit . In this case, all manipulations with the signal are carried out by software. The inventive method of encoding a digital signal for transmitting information is carried out, for example, as follows. The original byte is separated by masking the even and odd bytes. For the convenience of illustration, we denote all the digits of the 8-bit number from the smaller digit “0” and then the Arabic numerals as “76543210”. Then the odd byte will include the following bits "7531", and the even - "6420"

Next, with each of them, the following manipulations are performed.

In the odd byte "7531":

1) even bits are zeroed out, getting "70503010";

2) shift the received signal by 1 bit to the right, receiving "x7050301";

3) invert the received signal, receiving

4) reset all odd bits, getting

5) summarize the signal obtained in paragraph 4) with the signal according to claim 1), receiving a signal for transmission

In this byte, each bit of information is transmitted first without inversion, then with inversion, i.e. duplicated.

In the even byte "6420":

1) nullify the odd bytes, getting "0604020";

2) shift the received signal by 1 bit to the left, receiving "6040200x";

3) invert the received signal, receiving

4) zero out even bits, getting

Таким образом, и в данном байте каждый бит информации передается дважды - как инверсный и как прямой.5) summarize the signals obtained in paragraph 1 and paragraph 4), receiving

Thus, in this byte, each bit of information is transmitted twice - as inverse and as direct.

When receiving information, the decoding of the signal is, for example, as follows.

1) in the odd byte "7531" nullifies the even bits, receiving "70503010";

2) in the even byte "6420" nullifies the odd bits, getting "06040200";

3) sum the even and odd bits, resulting in the original byte "76543210".

If the forward bit contains an error, then the byte can be recovered from the inverse bits.

An example of encoding a byte according to the claimed method (see figure 1 and figure 2).

As the encoded byte we take, for example, the number "10000010" (82h)

1. Programmatically, we divide the original byte into bytes with even and bytes with not even bits.

Odd byte 1_0_0_1_

Even byte 0_0_0_0_

2. We write in the passes marked "_" the inverse value of the previous bit for the odd byte and the inverse value of the next bit for the even byte.

The result is two bytes: the odd byte 10010110 and the even byte 10101010, in which each bit is represented twice: in the first case (for the odd byte) direct and inverse values, and in the second case (for the even byte) - inverse and direct values.

Compared with the prototype, the inventive method can be implemented by software with simple signal manipulations with a small processor load.

Claims (1)

A method of encoding a digital signal for transmitting information, namely, that the digital signal is converted to a form characterized by the absence of a constant component when transmitting a long sequence of ones and zeros by encoding the original information signal, characterized in that the encoding is carried out according to the signal level, each byte is encoded the original digital signal is divided into two bytes - even and odd, while the even byte is obtained from the byte of the original digital signal by zeroing in it odd x bit, and the odd byte - zeroing even bits in it, and in the even byte, each bit of information is transmitted with the inverse value of the even bit written to the place of the neighboring zeroed odd zeroing bit and the direct value of the even bit, and in the odd byte each bit of information is transmitted with the direct value the odd bit and the inverse value of the odd bit recorded in the place of the neighboring zeroed even zeroing bit, while all manipulations with the signal are carried out by software.

Images