改善误码性能的索引调制正交频分复用混合映射方案

A Hybrid Mapping Scheme to Improve Bit Error Rate Performance of Orthogonal Frequency Division Multiplexing with Index Modulation System

为进一步提升索引调制正交频分复用(OFDM-IM)系统在高信噪比(SNR)条件下的误比特率(BER),该文提出一种混合映射方案。该方案利用高信噪比时索引比特比数据比特错误率更低的特性,混合使用两种不同位数的索引比特分配策略,提高了索引比特的占比。相应地,将子载波激活模式(SAPs)分为超级SAPs和普通SAPs,相比于普通SAPs,超级SAPs对应的索引比特和数据比特分别增加1 bit和减少1 bit。将超级SAP对应的数据比特采用奇偶校验的方式补齐,然后映射为数据符号,提高了系统的分集度,增大了数据符号间的最小欧氏距离。仿真结果表明,相比于以往的映射方案,混合映射方案在误比特率为10^(-4)时可取得1~3 dB的性能增益,有效改善索引调制OFDM系统的误码性能。

A hybrid mapping scheme is proposed in this paper to improve further the Bit Error Rate(BER)performance of Orthogonal Frequency Division Multiplexing with Index Modulation(OFDM-IM)system for high Signal-to-Noise Ratio(SNR).By taking advantage of the fact that the BER of index bits is lower than that of data bits in the high SNR region,the scheme uses two allocation strategies of index bits with different numbers,which increases the proportion of index bits.Correspondingly,the Subcarrier Activation Patterns(SAPs)are divided into super SAPs and normal SAPs.Compared with normal SAPs,super SAPs have seen increased index bits and decreased data bits by 1 bit respectively.The decreased data bits corresponding to a super SAP are supplemented with a parity-check bit and then mapped into symbols,which improves the diversity order of OFDM-IM system and increases the minimum Euclidean distance between symbols.The simulation results show that,compared with the previous mapping scheme,the hybrid mapping scheme can gain about 1~3 dB when BER is 10^(-4),and improve effectively the BER performance of OFDM-IM system.