Consider the situation as ,A & B are both sending with the same transmission power .As the signal strength decreases proportionally to the square of distance between them,B s signal drowns A s signal.As a result ,C cannot receive A transmission.
Now think of C as being an arbiter for sending rights. In this case ,termiinal B would already drown ut terminal A on physcial layer .C in return would have no chance of applying a fair scheme as it would only hear B.
Then near/far effect is a sever problem of wireless networks using CDM.All sognals should arrive at receiver with more or less the same strength.Oherwise a person standing closer to somebody could always speak louder than a person further away .Even if the sender were seperated by code,the closest one would simply drown out others .Precise power control is needed to receive the senders with the strength as that of receiver.For eg ,the UMTS system presented in chapter adapts power 1500 times persecond
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