What are the four main types of communication considered in classical information theory?
Consider a simple telephone conversation: A person (message source) speaks into a telephone receiver (encoder), which converts the sound of the spoken word into an electrical signal. This electrical signal is then transmitted over telephone lines (channel) subject to interference (noise). When the signal reaches the telephone receiver (decoder) at the other end of the line it is converted back into vocal sounds. Finally, the recipient (message receiver) hears the original message.
In classical information theory, communication is categorized based on the nature of the signals used and the presence of interference. There are four main types of communication considered:1
- Discrete, noiseless communication: Involves signals that represent a finite number of recognizable states, transmitted without interference.1
- Discrete, noisy communication: Involves discrete signals transmitted in the presence of noise, which is anything that interferes with the signal.12
- Continuous, noiseless communication: Involves analog signals that can vary over an infinite set of values, transmitted without interference.1
- Continuous, noisy communication: Involves continuous signals transmitted in the presence of noise.1
While discrete cases are generally easier to analyze than continuous ones, and noiseless cases are simpler than noisy ones, these categories provide the framework for understanding how information is transmitted accurately and efficiently across various channels.1