Apparatus and method for decoding in portable communication system

A decoding apparatus and a decoding method of a mobile communication system are provided to improve the performance of a decoder by improving a decoding speed when correcting an error about a control signal in an LTE(Long Term Evolution). An ACS(Add Compare Select) unit(303) adds and compares a branch metric calculated by a branch metric calculation unit and the previously stored branch metric as an input. The ACS(Add Compare Select) unit selects the surviving path of each state closet to the transmitted code sequence and calculates the state quantity of the surviving path. A traceback unit decodes the path by performing the traceback operation of the path with high probability equal to the original path based on the information stored in a surviving path storage unit. An error decision part(308) includes a CRC block(309) and a reverse CRC block(311). The error decision part confirms the error state about the signal and performs the traceback operation about the received signal.