[12]
(3.33)
(3.34)
3.4 FREQUENCY SELECTIVE FADING
In the previous sections we have lumped the rays that arrive at or about the same time into a single
statistically equivalent multipath. This single multipath doesn??™t discriminate against carrier frequencies
and it is often called frequency flat fading. In this section we will discuss a frequency selective
fading channel or more specifically the bandwidth of the wireless channel.
3.4.1 Power Delay Profile Methodology
Figure 3.14 depicts a scenario whereby the signals received by the terminal??™s antenna have arrived by
propagating or traveling through distinct propagation paths. Here distinct is used with reference to the
multipaths time of arrival. This scenario shows local scatterers surrounding the Mobile Station
AFTD
(m, mr2)
fd # r2m1 # 22p2m1
# emr2
LCR fd # 22p # mm1/2
(m)
# r2m1 # emr2
WIRELESS MULTIPATH CHANNEL 129
FIGURE 3.14 Frequency selective fading scenario.
(MS) being illuminated by the signal transmitted by the BS. Also shown is the presence of large, distinct
reflectors that can essentially act as point sources with respect to the MS position.
The plot of signal power versus time of arrival is called the power delay profile (PDP).
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