In 3G system power control is necessary to ensure that each mobile
user within a cell can receives and transmits the signal with enough power to correctly send the desired information while the signal is
interfering with the transmission from other mobile users within the cells. Efficient power control is very important for 3G system
performance. It is needed to minimise the interface in the system.
Thus reducing the interface directly results in increase in system capacity.

• Power control is very important to avoid low signal reception problem (near far effect) in 3G system. Signal strength decreases a distance between sender and receiver increases. Near and far terminal create problem in 3G system as signals received by the receiver have different signal strength. The power of the signal coming from the nearer terminal is much more than that the signal from far terminal. Thus mobile is will not be able to receive the signal coming from the far terminal as it appear as noise. Thus due to signal coming from near terminal the receiver cannot be able to receive the signal coming from far terminal. Therefore there is need to control power of the signal coming from all senders such that all the signals received by the receiver should have the equal strength of the signal at the receiver.

• If the mobile’s signal arrives at the base station with a lower power level than the required power level. Its error rate performance will be high while if the mobile’s signal is too high, it will interfere with other users with same radio channel. Power control minimizes interference to mobiles in same case station as well as mobiles in other base station by transmitting minimum required power.

• Power control adjusts the target signal to interference ratio in the base station according to the needs of the individual radio links and aims at a constant quality which is defined as a certain target bit error rate (BER) or frame error ratio (FER).Power control also improves quality of signal at the receiver by reducing effect of fading and shadowing with increase in transmission power.