CDMA is an interference limited system based on the number of user. Here each user is a noise source on shared cannel. Due to this CDMA system practically has a limit of users who can sustain, this is called soft capacity limit.
Near Far effect is basic feature of CDMA. If we assume that mobile transmit power is same for all user then mobile user near a cell jams a user that is distant from the cell. This problem may be present despite high processing gain. So an effective method to eliminate the near-far effect is necessary.
CDMA system uses power control technique to keep each MS at absolute minimum power level necessary to ensure acceptable service quality. Power control is essential for adjusting BTS and MS transmit power instantly according to communication distance (to overcome near far effect). Ideally the power received at the base station from each mobile station should be same (Minimum signal to interference).
