Nanocell and Picocell:

Microcells These cells are used for densely populated areas. By splitting the existing areas into smaller cells, the number of channels available and the capacity of the cells are increased. The power level of the transmitters used in these cells is then decreased, reducing the possibility of interference between neighboring cells. Some of the microcells may be as small as .1 to 1 km,depending on the need. Oftentimes the cell splitting will use the reduced power and the greater coverage to satisfy hot spots or dead spots in the network.
Another need may well be a below−the−rooftop cell that satisfies a very close−knit group of people or varied users. The picocell will be in a building and is typically a smaller version of a microcell. The distances covered with a picocell are approximately .01 to 1 km. These are used in office buildings for "close in" calls, part of a private branch exchange (PBX) or a wireless local area network (LAN) application today. A small group of users will share this cell because of the close proximity to each other and larger cells around. Nanocells also fall into the below−the−rooftop domain where the
distances for this type of cell are from .01 to .001 km. These are just smaller and smaller segments that are built within a building as an example. Figure 21−6 shows a combination of a microcell and a picocell.