基于编码的OFDM系统性能仿真

Performances simulation of coded OFDM systems

OFDM在多径衰落信道中,一些子载波由于深衰落会完全被丢失,从而影响整个系统的误码性能因此,必须将OFDM系统与信道编码结合起来以提高整系统的误码性能。构建了基于编码的OFDM仿真系统,通过仿真比较了基于LDPC码、乘积积累码(PA)和卷积码的OFDM系统在多径衰落信道下的BER性能。研究了信道块衰落长度与编码性能之间的关系,仿真结果分析表明,LDPC码和PA码在不引入交织的情况下,均可获得比引入交织的卷积码更大的性能增益,表明LDPC码和PA码在无线信道环境下具有很好的适应性。

Some subcarriers are lost because of deep fading when orthogonal frequency division multiplexing （OFDM） applying to muhipath fading channel, which influences the BER performance of the whole system. Hence, the OFDM system must be combined with the channel coding to improve the system BER performance. A coded OFDM system was built, and the BER performances of OFDM systems based on low density parity-check codes （LDPC）, product accumulate （PA） codes and convolutional codes were compared by simulation. In addition, the relationship between the coding performances and blocking fading channel lengths was studied. Simulation result shows that the performances of LDPC codes and PA codes , which are non-interleaved, outperform that of interleaved eonvolutional codes. It indicates that the LDPC codes and PA codes are more adaptive in multipath fading channels.