Cellular technologies have advanced from first-generation (1G) analog technologies to advanced high-performance fourth-generation (4G) and fifth-generation (5G) systems in just about 4 decades. Nevertheless, cellular technologies do maintain a set of common principles that form the basis behind the design of cellular systems. This webinar reviews these basic principles. First, the composition of the network and multiple access techniques are summarized. The radio interface protocols implemented between the Base Station and the handset are discussed. Various processes or interactions between the base station and the handset (e.g., fining of a base station and handover) are illustrated. Finally, key points of the webinar are summarized.