The process of information transfer is shown schematically in the figure. It is assumed that there is a source and recipient of information. The message from the source to the recipient is transmitted through a communication channel (information channel).

Rice. 3. – Information transfer process

In this process, information is presented and transmitted in the form of a certain sequence of signals, symbols, signs. For example, during a direct conversation between people, sound signals are transmitted - speech; when reading a text, a person perceives letters - graphic symbols. The transmitted sequence is called a message. From the source to the receiver, the message is transmitted through some material medium (sound - acoustic waves in the atmosphere, image - light electromagnetic waves). If technical means of communication are used during the transmission process, they are called information transmission channels(information channels). These include telephone, radio, television.

We can say that human senses act as biological information channels. With their help, the informational impact on a person is conveyed to memory.

Claude Shannon, a diagram of the process of transmitting information through technical communication channels was proposed, shown in the figure.

Rice. 4. – Process of information transfer according to Shannon

The operation of such a scheme can be explained in the process of talking on the phone. The source of information is the person speaking. The encoding device is a telephone handset microphone, with the help of which sound waves (speech) are converted into electrical signals. The communication channel is the telephone network (wires, switches of telephone nodes through which the signal passes)). The decoding device is the handset (earphone) of the listening person - the receiver of information. Here the incoming electrical signal is converted into sound.

Communication in which transmission is in the form of a continuous electrical signal is called analog communication.

Under coding refers to any transformation of information coming from a source into a form suitable for its transmission over a communication channel.

Currently, digital communications are widely used, when the transmitted information is encoded in binary form (0 and 1 are binary digits), and then decoded into text, image, sound. Digital communication is discrete.

The term “noise” refers to various types of interference that distort the transmitted signal and lead to loss of information. Such interference, first of all, arises for technical reasons: poor quality of communication lines, insecurity of different streams of information transmitted over the same channels from each other. In such cases, noise protection is necessary.

First of all, technical methods are used to protect communication channels from noise. For example, using a screen cable instead of a bare wire; the use of various types of filters that separate the useful signal from noise, etc.

Claude Shannon developed a special coding theory that provides methods for dealing with noise. One of the important ideas of this theory is that the code transmitted over the communication line must be redundant. Due to this, the loss of some part of the information during transmission can be compensated.

However, the redundancy should not be too large. This will lead to delays and increased communication costs. K. Shannon's coding theory allows us to obtain a code that will be optimal. In this case, the redundancy of the transmitted information will be the minimum possible, and the reliability of the received information will be maximum.

In modern digital communication systems, the following technique is often used to combat the loss of information during transmission. The entire message is divided into portions - blocks. For each block, a checksum (the sum of binary digits) is calculated and transmitted along with the block. At the receiving site, the checksum of the received block is recalculated, and if it does not coincide with the original one, then the transmission of this block is repeated. This will happen until the source and destination checksums match.

Information transfer rate is the information volume of a message transmitted per unit of time. Units for measuring the speed of information flow: bit/s, byte/s, etc.

Technical information communication lines (telephone lines, radio communications, fiber optic cable) have a data transfer speed limit called information channel capacity. Transmission speed restrictions are physical in nature.

(Answers at the end of the test)

A1. Which science classifies organisms based on their relatedness?

1) ecology

2) taxonomy

3) morphology

4) paleontology

A2. What theory was formulated by the German scientists M. Schleiden and T. Schwann?

1) evolution

2) chromosomal

3) cellular

4) ontogeny

A3. The storage carbohydrate in an animal cell is

1) starch

2) glycogen

4) cellulose

A4. How many chromosomes are in the germ cells of the fruit fly Drosophila if its somatic cells contain 8 chromosomes?

A5. The integration of its nucleic acid into the DNA of the host cell is carried out

1) bacteriophages

2) chemotrophs

3) autotrophs

4) cyanobacteria

A6. Sexual reproduction of organisms is evolutionarily more progressive, since it

1) contributes to their wide distribution in nature

2) ensures a rapid increase in numbers

3) contributes to the emergence of a wide variety of genotypes

4) preserves the genetic stability of the species

A7. What are individuals called that form one type of gametes and do not produce splitting of characters into offspring?

1) mutant

2) heterotic

3) heterozygous

4) homozygous

A8. How are the genotypes of individuals designated during dihybrid crossing?

A9. All leaves of one plant have the same genotype, but may differ in

1) number of chromosomes

2) phenotype

3) gene pool

4) genetic code

A10. What bacteria improve nitrogen nutrition of plants?

1) fermentation

2) nodule

3) acetic acid

A11. An underground shoot differs from a root in that it has

2) growth zones

3) vessels

A12. Plants of the angiosperm division, unlike gymnosperms,

1) have a root, stem, leaves

2) have a flower and a fruit

3) reproduce by seeds

4) release oxygen into the atmosphere during photosynthesis

A13. In birds, unlike reptiles,

1) unstable body temperature

2) cover of horny substance

3) constant body temperature

4) reproduction by eggs

A14. Which group of tissues has the properties of excitability and contractility?

1) muscular

2) epithelial

3) nervous

4) connecting

A15. The main function of the kidneys in mammals and humans is to remove them from the body.

2) excess sugar

3) metabolic products

4) undigested residues

A16. Human phagocytes are capable

1) capture foreign bodies

2) produce hemoglobin

3) participate in blood clotting

4) transfer antigens

A17. Bundles of long processes of neurons, covered with a connective tissue membrane and located outside the central nervous system, form

2) cerebellum

3) spinal cord

4) cerebral cortex

A18. What vitamin should be included in a person's diet to prevent scurvy?

A19. What species criterion should be used to classify the area of ​​distribution of reindeer in the tundra?

1) environmental

2) genetic

3) morphological

4) geographical

A20. An example of interspecies struggle for existence is the relationship between

1) an adult frog and a tadpole

2) a cabbage butterfly and its caterpillar

3) song thrush and fieldfare thrush

4) wolves of the same pack

A21. The tiered arrangement of plants in the forest serves as an adaptation to

1) cross pollination

2) wind protection

3) use of light energy

4) reducing water evaporation

A22. Which of the factors of human evolution is of a social nature?

1) articulate speech

2) variability

3) natural selection

4) heredity

A23. What is the nature of the relationships between organisms of different species that need the same food resources?

1) predator - prey

3) competition

4) mutual assistance

A24. In the biogeocenosis of a water meadow, decomposers include

1) cereals, sedges

2) bacteria and fungi

3) mouse-like rodents

4) herbivorous insects

A25. Can lead to global changes in the biosphere

1) increase in the number of individual species

2) desertification of territories

3) heavy rainfall

4) replacement of one community by another

A26. What percentage of nucleotides containing cytosine does DNA contain if the proportion of its adenine nucleotides is 10% of the total?

A27. Select the correct sequence of information transfer during the process of protein synthesis in the cell.

1) DNA → messenger RNA → protein

2) DNA → transfer RNA → protein

3) ribosomal RNA → transfer RNA → protein

4) ribosomal RNA → DNA → transfer RNA → protein

A28. With dihybrid crossing and independent inheritance of traits in parents with genotypes AABb and aabb, a split in the ratio is observed in the offspring

A29. In plant breeding, pure lines are obtained by

1) cross pollination

2) self-pollination

3) experimental mutagenesis

4) interspecific hybridization

A30. Reptiles are considered true terrestrial vertebrates because they

1) breathe atmospheric oxygen

2) reproduce on land

3) lay eggs

4) have lungs

A31. Carbohydrates in the human body are stored in

1) liver and muscles

2) subcutaneous tissue

3) pancreas

4) intestinal walls

A32. The secretion of saliva, which occurs when the receptors of the oral cavity are irritated, is a reflex

1) conditional, requiring reinforcement

2) unconditional, inherited

3) arising during the life of humans and animals

4) individual for each person

A33. Among the listed examples, aromorphosis is

1) flat body shape of the stingray

2) protective coloration in a grasshopper

3) four-chambered heart in birds

A34. The biosphere is an open ecosystem because it

1) consists of many diverse ecosystems

2) is influenced by the anthropogenic factor

3) includes all spheres of the earth

4) constantly uses solar energy

The answer to the tasks in this part (B1–B8) is a sequence of letters or numbers.

In tasks B1–B3, select three correct answers out of six, write down the selected numbers in the table.

IN 1. The biological significance of meiosis is

1) preventing the doubling of the number of chromosomes in the new generation

2) the formation of male and female gametes

3) formation of somatic cells

4) creating opportunities for the emergence of new gene combinations

5) increasing the number of cells in the body

6) multiple increase in the set of chromosomes

AT 2. What is the role of the pancreas in the human body?

1) participates in immune reactions

2) forms blood cells

3) is a mixed secretion gland

4) forms hormones

5) secretes bile

6) secretes digestive enzymes

AT 3. Factors of evolution include

1) crossing over

2) mutation process

3) modification variability

4) insulation

5) variety of species

6) natural selection

When completing tasks B4-B6, establish a correspondence between the contents of the first and second columns. Enter the numbers of the selected answers in the table.

AT 4. Establish a correspondence between a plant trait and the department for which it is characteristic.

AT 5. Establish a correspondence between the structural and functional features of the human brain and its department.

AT 6. Establish a correspondence between the nature of the mutation and its type.

When completing tasks B7–B8, establish the correct sequence of biological processes, phenomena, and practical actions. Write down the letters of the selected answers in the table.

AT 7. Establish the sequence of processes occurring in an interphase cell.

A) mRNA is synthesized on one of the DNA strands

B) a section of the DNA molecule is split into two chains under the influence of enzymes

B) mRNA moves into the cytoplasm

D) protein synthesis occurs on mRNA, which serves as a template.

AT 8. Establish the chronological sequence in which the main groups of plants appeared on Earth.

A) green algae
B) horsetails
B) seed ferns
D) rhiniophytes
D) gymnosperms

	Answer		Answer

	Answer		Answer

To better understand the process of information exchange and the conditions for its effectiveness, you should have an understanding of the elements and stages of the communication process.

Communication process

In the process of information exchange, one can distinguish four basic elements(Fig. 1.4):

• sender – a person who generates ideas or collects and transmits information;
• message – the actual information encoded using symbols;
• channel – a means of transmitting information;
• recipient – the person to whom the information is intended and who interprets it.

Rice. 1.4.

When exchanging information sender And recipient go through several interrelated stages. The main task of the sender– compose a message and use a channel to convey it in such a way that both parties understand and share the original idea. This is difficult, since at each stage the meaning of the message can be distorted or completely lost.

In the process of information movement, its advancement occurs, but the following stages:

• the birth of an idea;
• channel encoding and selection;
• broadcast;
• decoding;
• Feedback.

Let us consider the stages of the communication process in more detail in order to show what problems can arise at its different points (Fig. 1.5).

1. The birth of an idea. Information exchange begins with the formulation of an idea or the selection of information. In this case, the sender decides which idea or message should be the subject of exchange. Its role is to provoke and encode information with subsequent transmission to other participants in the process.

It is very important to correctly and carefully formulate your idea so that it becomes interesting and attractive to the recipient. It is important to remember that the idea has not yet been transformed into words or taken on another form in which it will serve the exchange of information. The sender only decided What exactly he wants to convey.

2. Encoding and channel selection. Before communicating an idea, the sender must encode it using symbols. For example, he may use words, intonation and gestures (body language) as symbols. This coding turns an idea into message.

The sender must also select channel compatible with character type, used for coding. Some commonly known channels include: speech, written materials, electronic communications including computer networks and email, video tapes and video conferencing. If the channel is not suitable for the physical embodiment of the symbols, transmission is not possible. If the channel is not very consistent with the idea, the exchange of information will be ineffective.

It should be remembered that the choice of communication medium should not be limited to a single channel. It is often desirable to use two or more means of communication in some combination. In this regard, the process becomes more complex, since the sender has to establish a sequence of use of these means and determine time intervals for transmitting information. However, it is believed that the simultaneous use of means of exchanging oral and written information is usually more effective than exchanging only written information. For example, if at a meeting of department heads, the head of the financial department has proposals to simplify mutual settlements, it would be more effective to present them in writing in the form of handouts, on a screen or flip chart in the form of graphs, diagrams, or videos, accompanying their demonstration with oral comments. At the same time, it is more likely that the information will be perceived, firstly, positively, secondly, completely (or to the maximum extent), and thirdly, the wishes and suggestions of interested colleagues will be promptly taken into account.

• 3. Broadcast. In the third stage, the sender uses a channel to deliver a message (an encoded idea or set of ideas) to the recipient. Here we are talking about the physical transmission of a message, which many people mistakenly take for the communication process itself. At the same time, communication is only one of the most important stages that must be passed through in order to convey an idea to another person.
• 4. Decoding. After the sender transmits a message, the recipient decodes it. Decoding is the translation of the sender’s symbols into the recipient’s thoughts. If the symbols chosen by the sender have exactly the same meaning to the recipient, the latter will know exactly what the sender had in mind when his idea was formulated. If no reaction to the idea is required, the information exchange process ends here.
• 5. Feedback. An exchange of information can be considered effective if the recipient demonstrates understanding of the idea through feedback. For example, he performed the actions that the sender expected from him.

Despite the apparent simplicity of the communication process, it rarely proceeds without interference. There are many potential barriers that stand in the way of effective communications. Factors that disrupt the purity of message transmission are commonly called “noise” in the communication process.

"Noise"- this is any factor that can disrupt the clarity of the transmission of the message at any moment in the communication process.

Sources of noise range from the complexity or imprecision of the message's language to differences in the perceptions of the people receiving it, which can alter the meaning of the encoding and decoding processes. For example, noise is said to occur when messages are poorly encoded (written unclearly) or poorly decoded (not understood), or when communication channels are ineffective (the recipient's attention is diverted from the message). The difference in organizational status between the manager and the subordinate can also be a hindrance, which also makes it difficult to convey information accurately.

Thus, noise in its essence is a barrier in the communication process.

There is always some noise in the communication process, so at each stage of the information exchange process some distortion of meaning occurs. If the noise level is high enough, there may be a noticeable loss of the meaning of the message or even a complete blocking of information exchange.

Rice. 1.5.

Thus, communication process is a sequence of actions when people communicate. Purpose of the communication process– ensuring understanding of the information being exchanged. The communication process has certain elements and occurs in stages. At each stage, “noise” (interference in communications) may occur, which can significantly reduce their effectiveness.

As noted above, the main goal of communication is the exchange of various types of information. Each enterprise is penetrated by a network of information channels that are designed to collect, analyze and systematize it. At the same time, in many cases, a manager can choose and use the most convenient channels of communication with other managers and subordinates. For example, you can discuss a problem in a personal conversation or over the phone; It is permissible to convey information to employees by writing a note or letter, or by posting a message on a notice board. The specific channel is largely determined by the nature of the message (Fig. 1.6).

Communication channels are classified according to their capacity.

Channel capacity is the amount of information that can be transmitted through it in one communication episode.

In general, communication becomes more effective when using a variety of channels, both written and oral.

The capacity of communication channels is affected by three factors:

• ability to process multiple signals simultaneously;
• the ability to provide fast, two-way feedback;
• ability to provide a personal approach to communications.

From the point of view of these possibilities, the best remedy is personal communication. Only it guarantees direct impact, transmission of multiple information signals, immediate feedback and personal approach.

Telephone communication or through other electronic means speeds up the communication process, but lacks the “presence effect”.

Personal written messages - notes, letters, comments - can also have a personal orientation, but they convey only words written on paper and cannot provide quick feedback.

Impersonal communication channels - bulletins, standard computer reports - are the smallest, their bandwidth is limited to the greatest extent.

Essentially, the effectiveness of a communication method depends on how suitable it is for the information that needs to be conveyed. In particular, research has shown that when information is ambiguous (i.e., needs clarification), oral communication is more effective than written communication. However, written communication is more effective when the information is obvious, simple and straightforward. For example, communicating work assignments to employees, informing them about decisions made, or consolidating previously reached agreements in writing.

In any case, the important question is not only which form of communication to choose, but also how to use it correctly. In table 1.1 provides some useful tips for using traditional means of communication.

Means of communication	Best Application	Terms of use
Email	Sending key information, registration confirmation	Keep your presentation concise Words last forever, so avoid sarcastic or offensive remarks
	Sending a finished document that requires a signature, a draft for approval, or a message to someone who doesn't have email access	Call ahead and let them know about sending a fax. Call after sending the fax to make sure in receiving it Avoid sending personal or confidential information that others may see
	Sending lengthy and complex material or thank-you notes	Make sure there are no errors Highlight key points at the beginning of the document Avoid long paragraphs, highlight them graphically Stay focused, avoid too many tasks
	Transferring information that carries an emotional charge (if a personal meeting is not possible)	Agree on the time of important calls in advance Listen to the other person without interrupting Keep the conversation brief, clearly highlighting important points Ensure that discussions of private matters cannot be overheard
	Conveying more sensitive and sensitive information	Schedule a meeting and come prepared to discuss issues

• Cm.: Daft R.L. Leadership lessons.
• Cm.: Daft R.L. Leadership lessons.
• Greenberg J., Baron R. Organizational behavior: from theory to practice. M., 2004. P. 441.

There are three main ways of transmitting information; each is used in the cage for a different purpose (see pictures below).

The transmission of genetic information consists of duplication (left), transcription (right) and translation (see pictures below). Genetic information is recorded in giant chains of deoxyribonucleic acid (DNA) molecules. The coding “letters” are four bases: adenine (A), thymine (T), guanine (G) and cytosine (C). Ordinary DNA consists of two complementary strands, in which A pairs with T, and G pairs with C. During duplication, a new complementary DNA strand is synthesized on each of the parent strands using an unknown mechanism. During transcription, only one strand of DNA serves as a template, on which a ribonucleic acid (RNA) molecule is formed. In the RNA molecule, instead of adenine, it is not thymine, but uracil (U). RNA molecules are divided into “translatable” (information) and “untranslatable”.

The process of translation involves translating genetic information from the four-letter “language” of nucleic acids (DNA and RNA) into the twenty-letter “language” of proteins. The “letters” of the protein “language” are 20 amino acids that are connected into protein chains. The DNA code is “rewritten” into the structure of messenger RNA, which binds to one or more particles, the so-called ribosomes, where protein synthesis occurs. Ribosomes consist of protein and two types of non-messenger RNA (16 S-RNA and 23 S-RNA). There is also soluble, or transport, RNA; its function is to transport amino acids to the site of protein synthesis. Apparently, each amino acid is encoded in messenger RNA by a group of three bases. According to the generally accepted hypothesis, the coding group is “recognized” by a complementary set of bases in the transfer RNA. Ribosomes apparently serve as a kind of clamping device for adding amino acids to the growing protein chain as the “tape” of messenger RNA is pulled through.

The first method is duplication, or doubling, that is, the formation of exact copies of a DNA molecule for transmission to the next generation of cells. During the copying process, the “language” and “alphabet” remain unchanged.

The second method, transcription, or rewriting, uses the same language but a slightly modified alphabet. At this stage, the DNA molecule is “rewritten” into a ribonucleic acid (RNA) molecule; its chains are built, like DNA chains, from four coding units. Three of them (A, G and C) are the same as in DNA, but instead of the fourth - thymine (T) - there is uracil (U). One specific type of RNA carries all the necessary programs for protein synthesis. This RNA is often called “messenger RNA,” but I prefer the terms “translated” or “information” RNA: information can be translated, but “messenger” cannot.

The third method of transmitting information, rightly called translation, or translation, is to translate from the language of messenger RNA (a four-letter alphabet) into the language of proteins (a twenty-letter alphabet). Every translation requires a dictionary; The cage also has its own dictionary. It consists of a set of relatively small molecules called transport (or soluble) RNA; their task is reduced to the transfer of specific amino acids to the site of protein synthesis. The connection of each amino acid with a transfer RNA molecule is catalyzed by a specific activating enzyme.

"Molecules and Cells", ed. G.M. Frank

Efficient encoding solves the problem of more compact recording of messages generated by the source due to their recoding. And it is used in almost all archivers such as Rar, Zip, etc. The peculiarity of these archivers is that they allow you to compress information a relatively small number of times (2-3, max 4 times), but at the same time, complete recovery of the compressed information occurs “ bit to bit." If you do not need to restore bit-to-bit information, then other transcoding methods are used that allow you to achieve compression tens of times. They are based on studying the patterns of creation of messages by the source, studying the properties of the source itself and understanding how necessary it is to preserve the initial information for the consumer. For example, when transmitting speech, you can not transmit it “bit for bit”, but allow distortions that the recipient of the voice message simply will not notice due to the insensitivity of the human hearing aid to these changes. At the same time, speech intelligibility, voice recognition, and its emotional coloring will be preserved. Partial loss of these qualities increases its compression. Let us emphasize once again that effective coding is the compression and restoration of information “bit for bit”.

General definition of coding and code. Coding tasks

Coding - in the broadest sense of the word - is the representation of messages in a form convenient for transmission over a given channel.

The inverse operation of encoding is called decoding.

Let us return again to the consideration of the general scheme of the information transmission system.

Rice. 3.1. General diagram of the information transmission system

Message X At the output of the information source (AI), it is necessary to match a certain signal. Since the number of messages tends to infinity with an unlimited increase in time, it is clear that creating your own signal for each message is almost impossible.

Since discrete messages are composed of letters, and continuous messages can be represented by a sequence of numbers at each counting moment, it is fundamentally possible to make do with a finite number of sample signals corresponding to individual letters of the source alphabet.

When the alphabet is large, they resort to representing letters in another alphabet with a smaller number of letters, which we will call symbols.

To denote this operation, the same term is used - coding, now understood in a narrow sense.

Since the alphabet of symbols is smaller than the alphabet of letters, each letter corresponds to a certain sequence of symbols, called a code combination. The number of characters in a code combination is called its value.

The process of converting letters into symbols can serve several purposes:

1. The first of them is to convert information into such a symbol system (code) so that it ensures the simplicity and reliability of the hardware implementation of information devices, i.e.:

• simplicity of equipment for distinguishing individual characters;
• minimum transfer time;
• minimum storage capacity during storage;
• ease of performing arithmetic and logical operations in the adopted system.

The statistical properties of the source of messages and interference in the communication channel are not taken into account.

The technical implementation of the encoding process in this simplest form with a continuous input signal is carried out by analog-to-code (digital) converters.

2. The second purpose of coding is, based on Shannon’s theorems, to harmonize the properties of the message source with the properties of the communication channel.

The so-called source encoder (SC) aims to provide coding in which, by eliminating redundancy, the average number of symbols required per message letter is significantly reduced.

In the absence of interference, this directly results in a gain in transmission time or storage space, i.e. increases system efficiency. http://peredacha-informacii.ru/ This coding is called effective coding.

In the presence of interference in the channel, effective coding allows you to convert the input information into a sequence of symbols that is best prepared for further conversion (maximally compressed).

The so-called channel encoder (CC) aims to ensure a given reliability when transmitting or storing information by additionally introducing redundancy, but using simple algorithms and taking into account the statistical patterns of interference in the communication channel. This type of coding is called noise-resistant coding.

The advisability of eliminating message redundancy using efficient coding methods followed by recoding with an error-resistant code is due to the fact that the redundancy of the message source in most cases is not consistent with the statistical patterns of interference in the communication channel and therefore cannot be fully used to increase the reliability of the received message, whereas it is possible to select a suitable one for this interference is a noise-resistant code.

In addition, message redundancy is often a consequence of very complex probabilistic dependencies and allows errors to be detected and corrected only after decoding the entire message, using highly complex algorithms and intuition.

So, the choice of encoding and decoding devices depends on the statistical properties of the message source, as well as the level and nature of interference in the communication channel.

If there is virtually no message source redundancy and no interference in the communication channel, then introducing both a source encoder and a channel encoder is impractical.

When message source redundancy is high and interference is low, it is advisable to introduce only a source encoder.

When the source redundancy is small and the interference is large, it is advisable to introduce a channel encoder.

If there is a lot of redundancy and a high level of interference, it is advisable to introduce both additional encoding and decoding devices.

After the channel encoder KK, the encoded signal enters the device for encoding symbols with signals - modulator M. The signal received at the output of the modulator Y prepared for transmission over a specific LAN communication line.

The device for decoding signals into symbols (DM demodulator) receives a signal from the communication line, distorted by noise, which is indicated in the diagram - Z.

The noise-resistant code decoding device (DC channel decoder) and the message decoding device (DI source decoder) produces a decoded message W to the recipient P (person or machine).

Efficient coding of information when transmitted over communication channels

1.7. Transmission of information over the channel without interference

If a sequence of discrete messages of duration is transmitted through a communication channel without interference, then the limit of the ratio

where is the amount of information contained in a sequence of messages (the speed of information transmission over the communication channel). The limiting value of information transmission speed is called the communication channel capacity:

As is known, the amount of information in messages is maximum when the probability of states is equal. Then

The speed of information transfer generally depends on the statistical properties of the message and parameters

communication channel. Bandwidth is a characteristic of a communication channel that does not depend on the speed of information transmission. Quantitatively, the throughput of a communication channel is expressed by the maximum number of binary units of information that a given communication channel can transmit in one second.

For the most efficient use of a communication channel, it is necessary that the information transfer rate be as close as possible to the throughput of the communication channel.

If the rate at which information arrives at the input of the communication channel exceeds the channel capacity, then not all information will be transmitted through the channel, i.e. the condition must be met

This is the main condition for coordinating the source of information and the communication channel. Negotiation is accomplished by appropriate message encoding. It has been proven that if the speed of information generated by the source of messages is sufficiently close to the channel capacity, i.e., where the value is arbitrarily small, it is always possible to find a coding method that will ensure the transmission of messages generated by the source, and the speed of information transfer will be very close to the channel capacity.

The converse statement is that it is impossible to ensure long-term transmission of all messages if the flow of information generated by the source exceeds the channel capacity.

If a message source with entropy per symbol equal to the communication channel capacity is connected to the channel input, the source is considered to be consistent with the channel. If the entropy of the source is less than the channel capacity, which may be the case if the source states are unequal, then the source did not agree

connected with the communication channel, i.e. the channel is not fully used.

Agreement in the statistical sense is achieved using so-called statistical coding. To understand the principle of statistical coding, consider two sequences of messages representing, for example, the state signal of a two-position controlled object (on or off) recorded at regular intervals:

Character 1 corresponds to the signal “object is on”, symbol 0 is “object is off”. We will assume that the symbols appear independently of one another.

For the first sequence, the symbols 1 and 0 are equally probable, for the second - the probability of the first symbol of the second symbol

Entropy of the first sequence Entropy of the second sequence Therefore, the amount of information per symbol in the second sequence is half that in the first.

When transmitting sequences through a binary communication channel, the first sequence will be consistent with the channel, while when transmitting the second sequence, the capacity of the binary channel per symbol is twice the entropy of the source, i.e. the channel is underloaded and, in a statistical sense, is not consistent with the source

Statistical coding makes it possible to increase the entropy of transmitted messages up to the limit that is obtained if the symbols of the new sequence are equally probable. In this case, the number of characters in the sequence will be reduced. As a result

the source of information is consistent with the communication channel. The technique of such encoding is described in § 2.9.

Chapter 1. GENERAL INFORMATION

1.7. Transmission of information over the channel without interference

Chapter 2. Non-redundant codes

Chapter 5. EVALUATION AND SELECTION OF CODES

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