基于三级LLR检测的广义零填充三模OFDM索引调制系统研究

Generalization of Zero⁃Padded Tri⁃Mode OFDM with Index Modulation Based on Three⁃Stage LLR Detection

本文提出了一种基于对数似然比(LLR)检测算法的广义零填充三模正交频分复用(OFDM)索引调制(GZTM⁃OFDM⁃IM)系统,目的在于提高传统ZTM⁃OFDM⁃IM系统的频谱效率(SE).在提出的系统发送端,更多的OFDM子载波激活样式有效提高了系统的SE,并且一种新的双模信号星座图被采用.为了降低接收端检测过程的复杂度,设计了基于LLR算法的三级检测器.仿真结果表明:利用设计的低复杂度检测器,GZTM⁃OFDM⁃IM在实现了高SE的同时,系统的误比特率(BER)性能在高信噪比(SNR)范围与传统ZTM⁃OFDM⁃IM相比没有降低,且BER性能与理论差错性能上边界非常接近.

In this paper,we propose a generalization of zero⁃padded tri⁃mode orthogonal frequency division multi⁃plexing with index modulation(GZTM⁃OFDM⁃IM)system based on the log⁃likelihood ratio(LLR)detection.In the pro⁃posed system,a dual⁃mode signal constellation is designed and applied,and a three⁃stage detector based on LLR algorithm is applied for the receiver.Due to more index activation patterns produced in the transmitter,spectral efficiency(SE)of the proposed system is efficiently improved compared with the traditional ZTM⁃OFDM⁃IM system.Simulation results show that the GTM⁃OFDM⁃IM system has higher SE than the corresponding ZTM⁃OFDM⁃IM,and maintains the bit error rate(BER)performance depending on the proposed detection algorithm with low computational complexity.And theoretical BER upper bound of the proposed system is fit to the simulation results at the high signal⁃to⁃noise ratio(SNR)region.