Communication technology: from radio to 5G and satellites

Modern communication rests on one idea: information can be carried by waves. Radio, television, mobile phones, and satellite links all encode sound, pictures, or data onto electromagnetic waves, send them through air or space, and decode them at the other end. Different frequencies suit different jobs. Long waves travel far and bend around obstacles, which suited early radio; microwaves carry more data but travel in straighter lines, which suits satellite links and mobile networks that use many small cells. Fibre-optic cables carry the same principle by light: signals encoded as pulses of light bounce along glass threads, carrying enormous amounts of data with little loss.

Mobile networks work by dividing territory into cells, each served by a base station. Early mobile systems were analogue and carried only voice; second-generation systems digitised voice and added text messages; third and fourth generations brought mobile internet, with 4G fast enough for video streaming. Fifth-generation (5G) networks are designed for higher speeds, lower delay, and many more connected devices at once, supporting uses such as remote machinery and dense urban coverage. Each generation reuses the same basic physics — radio waves and cells — but with more efficient ways of packing data into the available spectrum and smaller cells in busy areas.

Satellites extend communication beyond the reach of ground networks. Geostationary satellites orbit above the equator at a height where they circle Earth once a day, appearing fixed in the sky — ideal for broadcasting and for communication links that must stay pointed at one spot. Lower-orbit satellites pass overhead quickly and work in constellations, handing signals from one to the next, which suits global internet coverage. Satellite navigation works differently: receivers on the ground calculate their position from timing signals sent by several satellites, a system pioneered by the United States' GPS and now including India's NavIC regional system and other global constellations.

The social consequences follow the technology. Cheap, instant communication has transformed commerce, education, journalism, and politics, and has also made rumour spread as fast as news. Access is uneven: a village without reliable connectivity cannot use telemedicine or online learning, whatever the technology promises. Communication policy is therefore about spectrum allocation, infrastructure investment, affordability, and digital literacy as much as about the waves themselves. The physics makes connection possible; institutions decide who gets connected.