Variable LDPC coding rate performances for multicarrier systems using HD decoding

An adaptive coding scheme minimising the BER of a bit-interleaved coded modulation OFDM system performing hard-decisions (HD) after the demodulation and ideal interleaving is proposed. The subcarrier code rate levels subject to a rate constraint are varied according to perfect channel state information at the transmitter. The derived adaptive scheme uses low-density parity-check codes. A modified bit-flipping algorithm provides HD decoding and can be applied either alone or combined with a power loading scheme. It is shown by Monte Carlo simulations that, for broadband systems with Rayleigh fading, the loading procedure provides a signal-to-noise ratio gain up to 3dB for an average BER level of 10^-5.