The main objective of communication systems is to transmit high-quality voice, video, and data between users separated by a few meters or thousands of kilometers. The distance between the sites to be connected determines the type of transmission equipment, which can be metallic wires, optical fiber, microwave radio links, or satellite. At various stages along the route, numerous causes of distortion and additive noise under adverse conditions of propagation corrupt the signal and degrade the overall performance.
The purpose of this chapter is to describe the different steps of signal processing and to trade off basic parameters such as signal-to-noise ratio (SNR), signal distortion in amplitude and phase, group delay, coherence bandwidth, intermodulation, and interference in order to reach the system goals by optimizing the resources in terms of probability of error and bandwidth expenditure.
In an integrated services digital network (ISDN), the information to be transmitted passes through the following stages from one end to the other end: