Gugrajah_Yuvaan_ Ramesh_2003.pdf

Simulation ofa Load Balancing Routing Protocol Chapter 3
not acknowledged by their recipients but they are only sent when physical carrier
sensing indicates that the medium is clear.
Maximum range of node A
Figure 3-3. RTS/CTS transmissions avoid hidden terminal problem
3.4. Physical Layer Model
In contrast to wired networks, the properties of wireless channels are highly
unpredictable and time varying. The propagation of the radio signal is strongly
influenced by such factors as the distance between the transmitter and the receiver,
the geographical obstructions and terrain over and through which the signal traverses
resulting in fading, multi-path distortion due to reflection, refraction and shadowing,
and interference from adjacent signals operating in the same frequency band.
An important consideration in radio networks is the distribution of received signal
energies as a result of the fact that terminals are spatially separated with different and
varying distances. An important phenomenon related to the aforementioned fact is
the near-far effect, a process that favours signal reception from transmitting terminals
that are closer to a receiving terminal.
Radio propagation is a complex topic and implementing a complete physical layer
model is beyond the scope of this work. The physical layer model is therefore limited
to supporting propagation delay and attenuation and includes a free space model with
a two-ray ground reflection model.
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