Reconfigurable Low Density Parity Check (LDPC) Code Interleaving for SIO and MIMO OFDM Systems

This contribution derives an algorithm for optimizing the mapping of irregular and systematic low density parity check (LDPC) code word bits onto orthogonal frequency division multiplexing (OFDM) carriers in the context of a frequency selective fading channel in both, a single-transmit single-receive (SISO channel) and multiple-transmit multiple-receive (MIMO channel) antennas scenario. The absolute values of the frequency domain channel coefficients are assumed to be known and the LDPC code to be given (contrary to existing proposals where the LDPC code is optimized with respect to a given propagation channel). The proposed solution can alternatively be interpreted as an adaptive interleaver (which is inherently available in software defined radio type of system implementations) optimized for a given channel impulse response. In a typical WLAN (IEEE802.11n) scenario, the proposed mapping technique improves the system performance by up to approx. 0.7 dB compared to a linear (direct) mapping