In a ray-tracing system, the reflective,
refractive and dispersive
properties of physical objects are modeled within a computer, along with their
three-dimensional position. Every possible path that could be taken by a signal passing
from transmitter to receiver is then traced by the computer, building up a picture of the
level, angle of arrival and time delay of each one. From this information, it is possible
to determine the frequency response of the channel, and to simulate the effects of the
multipath fading on actual modem performance. This technique is very similar to that used
to produce real-world lighting effects on virtual 3-D models created in a computer.
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