fact that the user capacity of cellular networks can be increased by reducing
cell sizes currently stimulates the development of micro- and pico- cellular
networks. In macro-cellular networks cell sizes usually range from 1 to 20 km.
Typically, micro-cellular networks have cell sizes of 400 metres to 2 km, and
pico-cellular nets have cell sizes of 4 to 200 metres. For pico- and micro-cellular
networks, the name 'personal' communication is often used: most macro-cellular
telephone nets are designed for use within cars and may be too bulky and power-consuming
to be conveniently portable. With micro- and pico-cellular networks, low transmit
powers, say less than 20 mW, can be used, allowing miniaturisation of the handheld
In summary, we distinguish between
Decreasing cell size gives
- Macro-cellular nets, with cell radius 1 - 30 km
- Micro-cellular net, with cell radius 200 - 2000 m
- Pico-cellular nets, with cell radius 4 - 200 meter
However, system design differs for macro, micro and pico cells:
- Increased user capacity
- Increased number of handovers per call
- Increased complexity in locating the subscriber
- Lower power consumption in mobile terminal:
so it gives longer talk time, safer operation
- Small cells have a different propagation environment
- Different cell layout, micro-cells are often confined to one block of an urban street grid.
Start page of video from Short Course
Video from Wireless Communications Networks Short Course
"Typical cell sizes for the cellular phone system are one to 30
kilometers with a tendency to
go to micro cellular systems.
This has several advantages. With an increased user capacity,
the transmit power that you have to use in a micro cellular system is also much smaller
because the distance that you need to cover is only a few hundred meters so the battery size
in your hand held is also smaller. You can have a more convenient device.
There are a lot of other issues, like if you make a cell smaller it is more likely that I move
from one cell to another, so it's more likely that the system has to perform a handover to
another cell. "
Embedded QuickTime Video
Hierarchical Cell Structures
To enhance user capacity in so called "hot spots",
small microcells can be used to complement macrocells.
This leads to a mixed cell
structure with macrocells for wide-are coverage and microcells for
This is often referred to as an Hierarchical Cell Structure.
Typically, the operator divides the available spectrum
between the two cell layers into a macrocell band and microcell