1. A broadcasting receiver, comprising: a demodulator for demodulating a received broadcasting signal, clipping a soft metric value corresponding to the demodulated signal to a certain number of bits, and outputting a first clipped soft metric value; a mapper for mapping the first clipped soft metric value to an index value with a resolution inversely proportional to a quantization level of the first clipped soft metric value; a deinterleaver for deinterleaving the index value; a demapper for demapping the deinterleaved index value to a second soft metric value determined from a range of soft metric values mapped to the index value; and a channel decoder for decoding the second soft metric value.