基于LDPC频域编码MIMO-OFDM系统自适应调制算法研究

Research of Adaptive Modulation Algorithm in MIMO-OFDM Systems Based on LDPC Coding in Frequency Domain

提出了一种基于发射功率、发送比特和误码率均受限时规则和非规则LDPC频域编码MIMO-OFDM系统自适应调制算法。仿真比较了规则、非规则LDPC编码及未编码自适应调制MIMO-OFDM系统性能,比较了LDPC-SISO-OFDM、LDPC-MIMO-OFDM系统子载波数变化对系统BER性能的影响,比较了收发天线数变化对LDPC-MIMO-OFDM系统BER性能的影响。仿真表明自适应调制MIMO-OFDM系统比非自适应调制系统性能有所提高,规则、非规则LDPC编码自适应调制MIMO-OFDM系统比未编码系统性能有很大提高,非规则LDPC编码自适应调制MIMO-OFDM系统比规则码自适应调制系统性能有提高,但在高信噪比时有错误平层。结果证明,适当设计非规则LDPC频域编码自适应调制算法,可以大大改善MIMO-OFDM系统性能。

Based on transmitting power and transmitting bits and BER being limited, an adaptive modulation algorithm of irregular and regular LDPC coding in frequency domain MIMO-OFDM system was proposed. By simulating, a comparison among the performance of irregular ＆ regular LDPC coding and un-coding adaptive modulation MIMO-OFDM systems was made, the influence was compared that the change of the subcarriers numbers was on the BER performance of SISO-OFDM ＆ MIMO-OFDM systems, and the influence was compared that the change of the receiver ＆ transmitter antenna numbers was on the BER performance of MIMO-OFDM systems. The simulation results show that the performance of the MIMO-OFDM system with adaptive modulation algorithm is better than that without adaptive modulation algorithm, the performance of irregular ＆ regular LDPC coding MIMO-OFDM system with adaptive modulation algorithm is superior to un-coding system, and the performance of the irregular LDPC coding MIMO-OFDM system with adaptive modulation algorithm is better than the regular LDPC coding system, but there exists error layer on high SNR channel. The results prove that the proper design of the adaptive modulation algorithm with irregular LDPC coding in frequency domain can greatly improve the performance of MIMO-OFDM system.