
72 Energy-Efficient Cooperative Wireless Communication and Networks
40200
X axis
Y axis
–20–40
40200
X axis
–20–40
–40
–30
–20
–10
10
20
30
40
α = 4α = 3
Numerical result
Simulation result
Numerical result
Simulation result
0
Y axis
–40
–30
–20
–10
10
20
30
40
0
FIGURE 6.2 Cooperative region specified by (6.2) and its ellipse approxima-
tion for
α =3and 4.
merical results for different α, b,and
out
, indicating that the approximation
of the cooperative region by an ellipse is very accurate.
From the above analysis as well as the s imulation results shown later in
Figure 6.4, we see that the cooperative region, which is a circle for
α =2,
gets elongated along the x-axis for α<2 and ...