simplehiddenterminaldescription

一款用来进行网络模拟的软件

Hidden Terminal
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The problem of hidden terminal arises when 
two sender nodes out of range of each other transmit packets at the
same time, to the same receiver, resulting in collisions at the
receiver.
Since sender nodes are out of range of each other, they donot detect
carrier even though the other node is sending data, and if their
data packets reach the destination at the same time, these packets
are dropped due to collision at the receiver.

In our animation, we consider 4 cases :

Case 1 :
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When 2 nodes are in range of each other and they do carrier
sense at different times.
In this case, since sender nodes are in range of each other,
they are able to detect carrier and hence one node which
does carrier sense a little later than the other one, backs off,
thus deferring transmission.
As a result, their is no collision at the receiver.

Case 2 :
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When 2 nodes are in range of each other but they do carrier sense
at the same time. 
In this case, since sender nodes do carrier sense at the same time,
neither of the nodes is able to detect carrier, hence they both send
data packets to the receiver at the same time, thus causing a collision
at the receiver. Here we assume, data packets reach the destination
at the same time.

Case 3:
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When 2 nodes are out of range of each other and they do carrier sense
at different times.
In this case, since both nodes are out of range of each other, they 
donot detect carrier, but since they do carrier sense at different times,
thus sending data packets at different times, their data packets reach
the destination at different times, thus avoiding a collision at the
reciever.

Case 4:
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When 2 nodes are out of range of each other and they do carrier sense at
the same time
Here, since nodes are out of range of each other, they donot detect carrier,
and their data packets reach the destiantion at the same distance, thus
causing a collision and hence drop of packets.