Macro, Micro, Pico, Femto and Umbrella are all types of what?

Macro, Micro, Pico, Femto and Umbrella are all types of what?

• Cell sizes in a GSM network
• GSM filters
• GSM interfaces
• Uplink and downlink channels 

EXPLANATION

GSM mobile phone networks are "cellular," which means that mobile phones connect to it by nearest cell.
MACRO cells can be regarded as cells where the base station antenna is installed on a mast or larger building structures that are taller than an average roof-top level. Cell radius is typically from 1 up to 35 km.
MICRO cells are cells whose antenna height below average rooftop level and are typically used in urban areas. Size is from 400 m to 2 km. 
PICO cells are small cells whose diameter is only few dozen meters; they are used mainly in indoor applications.
UMBRELLA cells: A layer with micro cells is covered by at least one macro cell, and a micro cell can in turn cover several pico cells. A covering cell is called an umbrella cell.

SOURCE

https://en.wikipedia.org/wiki/Cellular_network