Enhanced Coordinate Interleaved OFDM Index Modulation
Enhanced Coordinate Interleaved OFDM Index Modulation
复制标题
带索引调制的增强型坐标交错 OFDM
DOI：
10.1109/access.2017.2777805
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
Zheng Beixiong
中科院分区：
文献类型：
--
作者：
Liu Yun;Ji Fei;Yu Hua;Chen Fangjiong;Wan Dehuan;Zheng Beixiong
具有折射率调制的正交频分复用（OFDM-IM）近年来引起了广泛的关注。在OFDM-IM中，块的信息比特通常被划分为若干子块，每个子块被进一步划分为两个部分，即，索引比特和符号比特。现有的OFDM-IM方案通过对每两个星座符号进行坐标交织操作，可以显着提高符号比特的误比特率（BER）性能，称为坐标交织OFDM-IM（CI-OFDM-IM）。在本文中，我们提出了一种新的OFDM-IM方案称为增强CI-OFDM-IM（ECI-OFDM-IM）。在ECI-OFDM-IM中，为了提高索引比特的误码性能，我们采用了一种特殊的子载波激活模式（SAP）查找表，其中任何一对SAP的汉明距离至少为4。为了改善由活动子载波传送的符号比特的BER性能，在每四个星座符号上进行两次旋转和坐标交织的操作。基于最大似然（ML）检测，推导了ECI-OFDM-IM系统平均误比特率的理论上界。利用对数似然比检测SAP，提出了一种半ML检测方案。理论和仿真结果表明，在频率选择性瑞利衰落信道下，ECI-OFDM-IM比CI-OFDM-IM具有更好的分集增益。
Orthogonal frequency-division multiplexing with index modulation (OFDM-IM) has attracted much attention in recent years. In OFDM-IM, the information bits of a block are generally divided into several subblocks, each of which is further split into two parts, i.e., the index bits and the symbol bits. By performing a coordinate interleaving operation over each two constellation symbols, the bit-error-rate (BER) performance of the symbol bits is significantly improved in an existing OFDM-IM scheme, which is called coordinate-interleaved OFDM-IM (CI-OFDM-IM). In this paper, we propose a novel OFDM-IM scheme termed enhanced CI-OFDM-IM (ECI-OFDM-IM). In ECI-OFDM-IM, to improve the BER performance of the index bits, we adopt a special subcarrier-activation pattern (SAP) lookup table in which the Hamming distance of any pair of SAPs is at least four. To improve the BER performance of the symbol bits conveyed by the active subcarriers, the operations of rotating and coordinate interleaving are conducted twice over each four constellation symbols. Based on the maximum likelihood (ML) detection, a theoretical upper bound on the average bit-error probability of ECI-OFDM-IM is derived in closed form. By using the log-likelihood ratio method for SAP detection, a semi-ML detection scheme is proposed. Both the theoretical and simulation results show that ECI-OFDM-IM outperforms CI-OFDM-IM with additional diversity gains over frequency-selective Rayleigh fading channels.