Micro-cells

Micro-cells are prevalent in wireless mobility systems as the operators
strive to reduce the geographic area each cell site covers thus facilitating
more reuse in the network. Micro-cells are also deployed to provide coverage
in buildings, subway systems, tunnels, and resolve unique coverage
problems. The technology platforms that tend to be referenced as microcells
involve any communication system that is less than 1/2 kilometer in
radius. Typically 4 to 10 micro-cells comprise the footprint that a macro-cell
site might be able to perform.
There are currently several types of technology platforms that fall into
the general categorization called micro-cells:
�¡ Fiber-fed micro-cell
�¡ T1/E1 micro-cell
�¡ Microwave micro-cell
�¡ High-power ReRad
�¡ Low-power ReRad
�¡ Bi-directional amplifier
The choice of which technology platform to utilize is driven by a variety
of factors that are unique to that particular situation. One driving factor for
the technology platform chosen is the application that is being engineered
for, capacity, coverage, or private wireless PBX. Another important factor in
the technology platform decision is the configuration options available at
that location for providing radio capacity. A third factor in the decision for
which technology to utilize is driven by the overall cost of the solution for
the network.
A micro-cell typically uses an omni antenna for transmission and reception.
The micro-cell also has less Tx power and lower gain receive antennas
then does its counterpart the macro-cell site. In addition the micro-cell site
typically exhibits a lower elevation then the macro-cell site does helping to
contain its coverage area leading to selected trouble spot resolutions. The
use of the omni antenna for micro-cells facilitates a smaller, physical
appearance leading to installations in more difficult land use areas.
An example of a micro-cell is shown in Figure 14-5. The form factor of the
radio hardware is not shown and is assumed to be insignificant or located
in the utility box next to the traffic light shown.