6. Radiosurveillance history and trends

6.1 System complexity

For several decades, radiocommunications have made a major contribution to industrial growth and economic development. They have developed by occupying an ever-wider spectrum, from VLF (Very Large Frequency – a few kilohertz) to EHF (Extremely High Frequency – a few tens of gigahertz), then by developing radio access technologies (RATs) and increasingly efficient, frequency-saving network topologies, such as cellular radio networks whose architecture is optimized for spatial reuse of spectrum resources.

• The radio-cell topology model and the normative and technical innovations that underpin it (roaming and mobility management during communications, for example) have largely influenced the evolution of other radiocommunications...