An improved adaptive modulation scheme for LDPC coded MIMO-OFDM system

In order to eliminate the spectral efficiency performance degradation caused by the rayleigh fading characters and channel correlations in MIMO-OFDM system, an improved adaptive modulation scheme based on low-density parity-check (LDPC) coding is proposed in this paper. In this improved scheme, the instantaneous average channel BER, which is obtained by estimating the bit sequences before and after the LDPC decoding, is used to set up two work modes for the system, in which different adaptive modulation strategies are adopted. Simulation results have shown that, over MIMI-OFDM rayleigh fading channels, the proposed transmission scheme may be well adapted to time-variant wireless channels, achieving a high spectral efficiency with a very low system complexity extra cost comparing with the single work mode adaptive modulation system.