Small cell
A short-range base station filling in where the big masts fall short — on lampposts, in ceilings, in tunnels.
Capacity in a mobile network is determined not just by technology but by how many users share each cell. Making cells smaller and more numerous is therefore the most direct way to raise capacity in dense areas. Range is measured in tens to hundreds of metres rather than kilometres.
The need grew with 5G, since higher frequencies have worse range and worse penetration. Deployment is slowed by practical rather than technical questions: each site needs power, backhaul and permission from a property owner or council. Indoors, distributed antenna systems are often used instead, where one signal source feeds many small antennas.