The basic elements make up the communication system including transmitter, channel and receiver.
The transmitter is responsible for the information is encoded or converted into a signal suitable for transmission. Signal transmission through the channel to the receiver. During transmission due to the presence of noise, signal the inevitable will be subject to change. Receiver-side trying to apply the appropriate decoding means to recover information from the degradation of the signal intact. Describe the channel of an important indicator of the bandwidth.
The structure of the communication system can be point to point, it can be a point-to-multipoint, broadcast is a special multi-point form of communication.
1948, then working at Bell Labs, Shannon published a paper, "Communication Principia Mathematica", this landmark paper to create a mathematical theory methods for the analysis of communication systems, and that information theory. Information theory allows us to derive the capacity according to the channel bandwidth and SNR characteristics.
Published in the paper era, the telecommunication system is mainly based on analog circuitry. Since then, with the increasing popularity of digital integrated circuits, telecommunications system design can take full advantage of information theory and theoretical guidance to improve performance. As a result, the digital signal processing has also become a new field.
The actual communication channel the inevitable existence of various defects, including: the shot noise, thermal noise, delay, non-linear transfer function, for fast fading, bandwidth limitations and signal reflections. In the current telecommunications systems design, these flaws can be exploited to improve the quality of the transmission channel.