Optimal power adaptation for OFDM systems with ideal bit-interleaving and hard-decision decoding

We derive power adaptation strategies optimizing the error rates of broadband bit-interleaved coded OFDM systems performing hard-decisions after the demodulation and ideal interleaving. The adaptive subchannel power allocation is based on either perfect or outdated channel state information in a time-division duplex transmission. We find that for an average bit error rate level of 10^-6 a gain of up to 4 dB can be achieved by the proposed adaptation in Rayleigh fading channels.