This is a nonrealistic scenario, hence Eq. (3.55) should be modified to include an average number
of users in each cell with proper power distribution. It is clear as the number of users increases in
each cell that the aggregate sum can approach a Gaussian distribution. In fact, some capacity analyses
have modeled this other user noise as Gaussian or Colored noise. Afew assumptions exist and are
given in [93].
A simplified model for this type of interference is given in Fig. 3.42 for the downlink communication.
Here we have chosen to show the top (or strongest in power) 6 interfering signals.
r(t) s(t) # h(t) a6
k1
sk(t) # hk(t) n(t)
148 CHAPTER THREE
7
5
2
1
6
4
3
6
1
3
6
4
2
5
6
4
5
3
5
4
3
1
1
7
7
2
FIGURE 3.41 Cell layout assuming a reuse pattern of 7.
3.5.1 Co-Channel Interference
CCI arises from another signal operating in the same frequency band, at the same time but with a different
transmitting waveform. This comes from frequency reuse in cellular systems. For example, let
us consider a cellular system (drawn with hexagonal shapes) with a frequency reuse pattern of 7 as
shown in Fig. 3.41.
These interfering signals are typically modeled as the aggregate sum of the transmitted signals
from that particular cell.
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