An important part of radio resource management is controlling the power levels used by transmitters. This power control is important because even in the best conditions the received power level is inversely proportional to the distance from the transmitter. Without power control, nearby mobiles could overwhelm transmissions from distant mobiles at the base station transceivers.
The domination by a nearby transmitter can prevent distant transmitter signals from ever being detected at the receiver. Even more pernicious is the so-called near-far or hidden terminal problem. This occurs when one transmitter is much closer to a receiver than another transmitter. If the nearby transmitter signal is captured successfully by the receiver, the receiver might acknowledge the successful reception of the signal. The distant transmitter might then incorrectly conclude that its signal was successfully received. Undetected errors are quite undesirable.
A base station must prevent nearby mobiles from transmitting with power levels that overwhelm other mobiles in the cell. The received signal strength (RSS) at the base station should be approximately the same for all mobiles in the cell. Often power control algorithms are based on the so-called reciprocity of RF signals (i.e., the RSS in one direction is the same as in the other direction if both transmitters are at the same power level).2.23 Of course, the base station can always direct individual mobiles to use another power level. Power control is especially important at cell boundaries, to reduce the number of unnecessary handoffs and avoid interference.