
270 Simulation Technologies in Networking and Communications
whose Fourier transform is a rectangular pulse:
Pf
Tf
T
f
()
=
≤
>
⎧
⎨
⎪
⎪
⎪
⎪
,
,
2
0
1
and which occupies the smallest possible bandwidth, W = 1/2T, but has the highest secondary lobes
(thus being very sensitive to synchronization errors and requiring long lters to achieve a good
performance). Good compromise solutions typically use 0.25 ≤ α ≤ 0.5. Figure 10.2 shows several
examples of the aforementioned shaping lters, both in the time and the frequency domains. For
the raised cosine lters, note the decrease in the amplitude of the side lobes as α increases and the
0
0
T/4
–T/4
T/2
3T/4
t
5T4