2.2.2 Cochannel
Interference
One of the primary forms of man-made signal degradation
associated with digital radio, co channel interference occurs when the same
carrier frequency reaches the same receiver from two separate transmitters.
Fig
2.5: Illustration of Co channel Interference in a Typical Cellular Grid
[8].
It could be seen that both broadcast antennas as well as more
focused antenna systems scatter signals across relatively wide areas. The
signals that miss an intended user can become interference for users on the
same frequency in the same or adjoining cells [8].
While sectorized antennas multiply the use of channels, they
do not overcome the
major disadvantage of standard antenna broadcast co channel
interference. Management of co channel interference is the number-one limiting
factor in maximizing the capacity of a wireless system. To combat the effects
of co channel interference, smart antenna systems not only focus directionally
on intended users, but in many cases direct nulls or intentional
noninterference toward known, undesired users [13].
| 
