Patent ID: 8831123

Claim:
An apparatus configured to perform soft demapping, the apparatus comprising: a detector configured to detect a log likelihood ratio (LLR) value with respect to a quadrature amplitude modulation (QAM) signal, using a shifted table scheme, and set a shift step that is shifted by the shifted table scheme to zero to cancel detecting the LLR value using the shifted table scheme, and detect the LLR value using a reference LLR table, in response to at least one of two channels corresponding to an erasure channel; a decoder configured to decode the detected LLR value; a region selector configured to designate a sub-region of the QAM signal corresponding to bit information that is obtained from the decoded LLR value; and a calculator configured to calculate an LLR value of other bit information that is included in the designated sub-region, wherein the shifted table scheme assumes that a Q value of a received signal equals zero as a reference LLR value, and then shifts from the reference LLR value corresponding to an even bit value of the I channel by an LLR value that corresponds to each bit based on the Q value of the received signal.