Modulation

In the modulation process, one characteristic of a high‐frequency carrier signal is modified according to the instantaneous amplitude of the signal to be processed. Basic modulation types are as follows: amplitude modulation, frequency modulation, and phase modulation. The radiofrequency spectrum is aimed at many users and communication services are only growing. Digital modulation has greater capacity to propagate large quantities of information than analog. Digital transmission systems broadcast information between a source and a receiver or an intended recipient using a physical support such as a cable, optical fiber or propagation along a radioelectric channel. The probability of error Pe per bit transmitted is an important criterion for the quality of a transmission system. It depends on the transmission technique used, as well as the channel on which the signal is transmitted.