By Dr. Ernest Simo
28.0 Let's look at an example of the Near-Far Problem.
Now, let's have mobile user M2 move half way toward the Base Station. Figure above shows relative distances of M1 and M2 with respect to the Base Station.
Let's assume that M1 and M2 continue to transmit the same power levels towards the Base Station (Pt1 = Pt2). Let's further assume a propagation loss model which indicates that the mean received power is inversely proportional, not to the square of distance, but to the fourth power of distance (d-4 law of distance).
Under these conditions, the received power level at the Base Station are such that :
At the Base Station, M2 acts as a powerful jammer to M1: The received power from M1 (Pr1) is totally swamped by the received power from M2.
It would take 16 users like M1 to produce the same power density as M2 at the Base Station. In other words, M2 can be replaced by 16 users like M1. This would significantly increase the overall system capacity.
© 2001 DR. ERNEST SIMO - SPACE2000