Digital Communication Techniques

Introduction

The word “communication” is now a catch-all in modern society; in its most basic sense, it makes it possible to share information. A department that in any French university or technical school might historically have been labeled as “humanities” (at the end of the 1960s, particularly focused on human resources or sociology); was often later reduced to “communication and humanities”, both terms having become interchangeable in the meantime. Perhaps, now devoid of a clear meaning, nothing will be left apart from the term communication?

This word must not be amalgamated into others: information (transport), (en)coding. Perhaps later semantics are involved in this book, in a strict, technical sense, certainly not in any modernistic sense.

I.1. Why digitize the world?

For broadband communications, transmissions are limited by physical constraints, such as noise or interference, resulting from system imperfections and physical components modifying the transmission of the signal sent. Distortion of the signal over the course of the broadcast is, similarly, a concern. Hence, there is a need for a clear separation of the signals sent, so that, in practice, they remain distinct when they are received.

The transmission of a set of signals undergoes data dispersion over time, leading to intersymbol interference. Signals reflected from buildings, the ground or vehicles cause this dispersion, depending on the length of the paths traveled. The significance of this phenomenon ...