In recent years, orthogonal frequency division multiplexing with index modulation (OFDM-IM) has been proposed due to its extra diversity gain. Specially, OFDM with all index modulation (OFDM-AIM) was proposed, which removed symbol bits and enhanced the diversity order compared to typical OFDM. However, the security issue of OFDM-AIM has not been given full attention. This paper proposes an encrypted subblock design aided OFDM with all index modulation (ESD-OFDMAIM) scheme to enhance physical layer security. Firstly, an encryption process of subblock design was put forward, which creates a random look-up table and thus the mapping rule of ESD-OFDM-AIM between information bits and subblock realisations becomes random and time varying. Moreover, the scrambling and rotation encryption based on chaotic sequences from channel state information is utilised to prevent the eavesdropper from stealing the information via wireless channel. For eavesdroppers, parameters of ESD-OFDM-AIM such as spectral efficiency (SE), constellation points and the length of look-up table are concealed by the encryption. Finally, analyses of attack models and the information entropy of constellations are also provided to measure the security of ESD-OFDM-AIM. Simulation results show that ESD-OFDM-AIM can effectively improve the system security without the affecting bit error rate performance.

中文翻译：

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全索引调制的加密子块设计辅助OFDM

近年来，由于其额外的分集增益，已经提出了具有索引调制的正交频分复用（OFDM-IM）。特别地，提出了具有全索引调制的OFDM（OFDM-AIM），与典型的OFDM相比，该符号去除了符号位并增强了分集阶数。但是，OFDM-AIM的安全性问题尚未得到充分关注。本文提出了一种采用全索引调制（ESD-OFDMAIM）方案的加密子块辅助OFDM技术，以增强物理层的安全性。首先，提出了子块设计的加密过程，建立了一个随机的查找表，从而使ESD-OFDM-AIM在信息比特与子块实现之间的映射规则变得随机且随时间变化。此外，利用基于信道状态信息混沌序列的加扰和旋转加密技术，防止窃听者通过无线信道窃取信息。对于窃听者，加密隐藏了ESD-OFDM-AIM的参数，例如频谱效率（SE），星座点和查找表的长度。最后，还对攻击模型和星座信息熵进行了分析，以衡量ESD-OFDM-AIM的安全性。仿真结果表明，ESD-OFDM-AIM可以有效提高系统安全性，而不会影响误码率性能。加密隐藏了星座点和查找表的长度。最后，还对攻击模型和星座信息熵进行了分析，以衡量ESD-OFDM-AIM的安全性。仿真结果表明，ESD-OFDM-AIM可以有效提高系统安全性，而不会影响误码率性能。加密隐藏了星座点和查找表的长度。最后，还对攻击模型和星座信息熵进行了分析，以衡量ESD-OFDM-AIM的安全性。仿真结果表明，ESD-OFDM-AIM可以有效提高系统安全性，而不会影响误码率性能。