By Dr. Ernest Simo
27.0 What is the Near-Far problem and how does Power Control affect it?
Power Control is required in CDMA systems, in part, to resolve the Near-Far problem. Let's define the Near-Far problem:
- Consider two Mobile users M1 and M2, distance d from the Base Station, and transmitting equal power levels Pt1 and Pt2 respectively. Assuming same propagation impacts on both paths, the received power levels at the Base Station, from M1 and M2 are equal. That is: Pr1 = Pr2.
- Let's assume that the received signal, Pr1, from Mobile user M1 is the wanted signal at the Base Station. In this case, the received signal, Pr2, from mobile user M2 represents interference. Therefore, C/I = Pr1/Pr2 = 1 (since Pr1 = Pr2).
© 2001 DR. ERNEST SIMO - SPACE2000