An Ordered LDPC Coded OFDM System with Power Allocation

A novel adaptive LDPC coded OFDM transmission technique is proposed in this paper. Assuming the channel state information (CSI) is known to the transmitter, the irregular LDPC coded bits are ordered and allocated into subcarriers adaptively. Then two power allocation schemes, fixed ratio truncating (FRT) and fixed ratio inverse water-filling (FRIWF), are proposed to reallocate the power of each subcarrier. Performance of the strategy is analyzed by density evolution and numerical simulation. "Equal SNR search" (ESS) algorithm is also proposed to evaluate the performance of FRIWF scheme. Noticeable gain in terms of SNR can be achieved over frequency-selective fading channels.