Quantizing method for iterative decoder in communication system

PURPOSE: A quantizing method for an iterative decoder is provided to obtain optimum coding parameters by extending a quantization range to less or more than a transmission level in consideration of a metric calculation in a decoder. CONSTITUTION: A quantizing method extends a quantization range to less or more than a transmission level of an input signal. Each decoder built in an iterative decoder uses the map mode and the soft input/soft output mode. The iterative decoder may be a turbo decoder. A truncation value is at least more than 1 in the quantization range extension. The truncation value may be set to 4. The number of signal representation bits for the metric calculation of each decoder is the number obtained from the addition of the number of quantization bits and the number of two bits.