It is practically accepted to
use a statistically equivalent ray whose envelope is Rayleigh distributed and whose phase is uniformly
distributed (assuming an omni directional receiving antenna). This is shown in Fig. 3.6 as a
bold dashed line.
Let us introduce the notion of vehicular movement into the channel. The faster the vehicle travels, the
more often the signal will encounter both peaks and nulls. On the contrary, the slower the vehicle travels,
the less often the signal will encounter both peaks and nulls. Moreover, when a null is encountered the
signal will actually reside there longer with a slower vehicle speed, as apposed to the faster vehicle speed.
The channel model discussion was presented from the point of view of the mobile station [8]. We
can apply the theorem of reciprocity and reverse the directions of the propagation arrows to arrive at
an uplink model. However, care must be taken when modeling multiple receive antennas on the
uplink due to the fact that the surrounding environment of the base station is different than that of the
mobile station [9].
122 CHAPTER THREE
s(t)
n(t)
R(t) = r(t)*s(t) + n(t)
r(t)
Rayleigh Probability Density Function
0
0 1 2 3 4 5
0.1
0.2
0.3
0.4
0.
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