Apparatus and method for computing soft decision input metric, and apparatus and method for demodulating received symbol

摘要

An apparatus and a method for computing soft decision input metric, and an apparatus and a method for demodulating a received symbol using the same are provided to implement computation of a bit LLR(Long Likelihood Ratio) of a 16-QAM(Quadrature Amplitude Modulation) modulated symbol in a simple hardware and improve accuracy. An apparatus for computing soft decision input metric includes a first scaler(600), a second scaler(620), an absolute value computing unit(640), and a linear calculating unit(660). The first scaler scales a real number part y1 and an imaginary number part yQ of a received code symbol by a constant g1. The second scaler computes input metric of a partial code bit by scaling values scaled in the first scaler by a constant alpha minimizing an error. The absolute value computing unit computes absolute values of the values scaled in the first scaler. The linear calculating unit computes input metric of the rest code bit by linearly mixing the absolute values and an input parameter g2(k).