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EXPOSED TERMINAL PROBLEM

By isek ·
if a station hears no response to an overheard RTS, then it may assume that the intended recipient of the RTS is either down or out of range. An example is shown in figure 4. Station X is within range of Y, but not Z. When Y sends traffic to Z, X will hear Y?s RTS packets but not Z?s CTS responses. X may therefore transmit on the channel without fear of interfering with Y?s data transmissions to Z even though it can hear them. In this case MACA allows a transmission to proceed when ordinary CSMA would prevent it unnecessarily, thus relieving the exposed terminal problem.

Since X can hear the transmission from Y to Z, Y can also hear the transmission from X to another station. X and Y are inside the communication ranges of each other. When they send data to their receivers respectively, don't the signals interfere each other in the middle of each sender and receiver? The following figure illustrates the scenario.

A capital letter stands for a station.
n stands for the border of the communication range of station N.
The communication range of a station is the width of 6 characters.

w----xW---yXw--zYx---Zy----z

As shown in the figure,
(1)X cannot hear z.
(2)X can hear y.
(3)Y can hear x.
(4)Since all signals go through the same channel, x and y collide between the right x and the left y so that W and Z receive corrupt signals.

Does radio communication work as (4)? Or, is a signal corrupt for a receiver only when there is another signal in the same channel at the same time?

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by seanferd In reply to EXPOSED TERMINAL PROBLEM

Seeing as you didn't even try to hide the fact that this is homework, good luck getting any sort of positive response.

There are at least a few people here with radio experience, but they don't hang about answering questions much.

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