Patent ID: 7876846

Claim:
A method of demapping in a receiver wherein the input signal is a) demodulated into I real and Q imaginary data pairs which was mapped using a constellation having M data bits for the I and Q pairs, b) demapped, c) deinterleaved and d) decoded, the method of demapping comprising: deriving M intermediate soft bit values y j for the I and Q data pairs as a function of the spacing in the constellation; limiting the range of the M values y j ; deriving a look-up table index for each of the limited M values y j ; indexing a look-up table, having 2 N+1 entries for supporting up to N soft bits, for each M data bit using the derived indices; and outputting K soft bits for each data bit of the I and Q data pairs where K<=N wherein the range is limited to ±1 and the indices are derived by 2 K −(2 K −1)*y j .