3.5 MAN-MADE SYSTEM INTERFERENCE
Up until now the channel model has been developed based on natural phenomenon. By this we
mean the wave pattern generated due to buildings, hills, mountains, and so on. Now a component
of the channel model is presented whereby the source is from the communication system designer.
In particular this section will address co-channel interference (CCI) and adjacent channel interference
(ACI).
Here we see all cells operating on frequency fj will interfere with one another (given they transmit
at the same time). Smaller reuse factors exist, for example 3 or 1, where one would expect this interference
will increase. This is a typical scenario faced by time division multiple access (TDMA) systems.
In code division multiple access (CDMA) systems, however, a reuse factor of 1 is typically used
as well as usage of different PN codes for other cell separation.
Asimple model for CCI is given as follows, assuming the above cellular example with a frequency
flat fading channel.
(3.55)
where s(t) desired signal, h(t) channel response of desired signal, sk(t) kth interfering signal,
hk(t) channel response of the kth interfering signal, n(t) AWGN.
This simple model assumes a single modulated interferer or user present in the frequency reuse
cells.
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