基于自适应排序LDPC码的OFDM系统及其性能分析

为了在正交频分复用(OFDM)系统中充分利用非正则低密度奇偶校验(LDPC)码编码比特错误概率不同的特性,提出了一种新的基于自适应排序LDPC码的OFDM传输技术.假设发射机已知信道状态信息(CSI),非正则LDPC码的编码比特根据度进行排序,并被分配到相应的子载波上,度高的比特分配到轻度衰落的子载波,度低的节点分配到深度衰落的子载波.为了降低反馈信道的开销,可以对反馈的CSI进行量化.该传输技术的性能可以由密度演进算法进行分析.分析和仿真结果表明,相对于传统的无排序LDPC码编码OFDM系统,所提出的基于自适应排序LDPC码的OFDM系统可以获得1 ~1.5dB的性能增益,并且对CSI的量化具有鲁棒性.

Design and performance analysis of adaptive ordered LDPC coded OFDM system

A novel adaptive ordered LDPC (low-density parity-check) coded OFDM (orthogonal frequency-division multiplexing) transmission technique is proposed to exploit different error probabilities of irregular LDPC coded bits in OFDM systems.Assuming that the CSI (channel state information) is known at the transmitter,the irregular LDPC coded bits are ordered according to their degrees and then allocated into subcarriers adaptively.Bits with higher degrees are allocated into less attenuated subcarriers and bits with lower degrees are allocated into deep attenuated subcarriers.Quantization on CSI feedback can be applied to minimize the signaling overhead.Performance of this strategy is analyzed by density evolution and numerical simulation.Simulation results show that about a 1 to 1.5 dB gain in terms of SNR (signal to noise ratio) can be achieved over frequency-selective fading channels compared to conventional LDPC coded OFDM systems without ordering, and the proposed scheme is robust to CSI quantization.