An iterative decoder with a gain controller in a mobile communication system. In the iterative decoder, a first component decoder receives a first extrinsic information signal, a first parity signal, and a systematic code signal, decodes the systematic code signal out of the received signals, and generates a primary decoded signal including a second extrinsic information component. Here, the first and second extrinsic information signals remove noise in the input signals to the first and second component decoders. A second component decoder receives the primary decoded signal from the first component decoder and a second parity signal, decodes the decoded signal out of the received signals, and generates a secondary decoded signal and the first extrinsic information signal. One or more gain controllers are connected between the first and second component decoders, for attenuating either or both the first and second extrinsic information signals.