| Popis: |
The clarification of the concept of information only slightly supplements the intuitive understanding of this term and does not provide anything for the construction of a quantitative theory of information that could be used in solving engineering problems. For such a theory, it is necessary to introduce an "operational" definition of this concept, which is based on an indication of the measurement method. To estimate the amount of information received, it is necessary to find a measure of the uncertainty of a particular situation. When transmitting information over a distance, at the output of the transmitting converter there is a finite system of signals that unambiguously correspond to the symbols and form the input alphabet of the communication channel. At the output of the receiving device, there is a finite system of signals that form the output alphabet of the communication channel. The process of transmitting information consists in selecting chips, sending them over the communication line and making a decision on the transmitted signal based on the received chip. It is obvious that the extraction of information about signals from signals is associated with the representation of the alphabets {X} and {Z} in the form of a combined set {XZ}. The transfer of information in communication systems is always associated with a change at the receiver of information about the actually transmitted signals. From the point of view of the receiver, the alphabet of the source has uncertainty, since he can only know a priori probabilities, but it is not known whether the signal was actually transmitted; this can be judged only by the magnitude of the posterior probabilities. From this point of view, setting some numerical characteristics of a random variable is not enough. This article analyzes the issues of reliability of events in the "ensemble" of received messages, depending on the a priori probabilities of events. The assessment of the amount of information in relation to the reliability of the received messages is made, the recommendations used in solving majority of the problems associated with the construction of information transmission and transformation systems are indicated. |
