3 at a distance of 10 m. These values
are chosen to adjust the correlation of the generated shadowing signal. Typical decorrelation lengths
are 5 m for urban and 300 m for suburban [91]. The application of the log-normal fading is shown
in Fig. 3.51.
Rxx(k) s2 # a
vT
D ZkZ
d
158 CHAPTER THREE
Transmitter Receiver
H(k) x(k)
n(k) Small
Scale
Fading
Large
Scale
Fading
FIGURE 3.51 Channel model including log-normal shadowing.
The slow fading generation model is shown in Fig. 3.52.
A question remains as to how long does one average the received signal power to determine the
local mean variations. Some work has been published showing keeping the averaging interval greater
than 20 wavelengths is fine [130].
Delay
1 ??“ ad
2
ad
N(0,1)
x(k)
s
FIGURE 3.52 Log-normal shadowing generation block diagram.
3.8 MULTIPATH FADING SIMULATION MODELS
In this section we will provide a few methods that are typically used to simulate (and in some cases
emulate in test equipment) the multipath, small scale fading. We will begin by discussing the classical
Jakes model [1], next we present a modified Jakes model [130??“134] to overcome potential short
comings of the model in certain applications, and lastly we present a probabilistic model to generate
the fading waveform.
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