In this paper coded diversity schemes over block fading channels are considered. The performance of radio communication systems over fading channels is commonly improved by using diversity techniques; we consider an adaptive modulation and coding scheme for bit-interleaved coded Modulation. Adaptive modulation is most effective when the channel diversity orders are small (L=3-5). Two adaptation algorithms are proposed for improving the power efficiency of coded orthogonal frequency division multiplexing (OFDM) on fading channels. A bit-loading technique for maximizing the throughput at a fixed bit error probability is described. A power loading technique for minimizing the bit error probability at a fixed rate with minimal transmitter power is also discussed.