Efficient soft-in-soft-out sub-optimal decoding rule for singleparity check codes

The authors present an efficient, sub-optimal, soft-in-soft-out decoding rule for single parity check (SPC) codes, which requires only three addition-equivalent-operations per information bit. Its application is demonstrated by the simulation results of a rate 5/6 four-dimensional concatenated SPC code, for which performance of BER=10 ^-5 at E_h/N₀=3.5 dB is observed, which is only ~1.2 dB from the theoretical limit