Spatial index modulation, which utilizes the antenna spatial domain to exploit the additional information, is a promising technique for improving the spectral efficiency in next wireless communication network. In this paper, to exploit more additional information from the antenna spatial domain, with the dimensions of the three dimension (3D) signal constellation, Space Modulation with design of Expanded antenna Index Vectors (EIV) by modulating Two types of 3D signal Constellations (SM-EIV-T3DC) is developed. In the proposed SM-EIV-T3DC, with the aid of two types of 3D signal constellations, an extended antenna index (AI) vector set \(\Gamma\) is first designed, in which one part of vectors is used to modulate the conventional 3D signal constellation points (CPs) and another part of vectors is used to modulate the secondary 3D signal CPs. Then, on the basis of modulating three components of one 3D signal CP by the designed set \(\Gamma\) , four AI vector sets: \(\{\Upsilon _1, \Upsilon _2,\Upsilon _3,\Upsilon _4\}\) are designed to expand the number of AI vectors, whose vectors contain one or two non-zero elements equaling to ”j”. All vectors from two sets \(\{\Upsilon _1, \Upsilon _3\}\) are with two non-zero elements, while all vectors from two sets \(\{\Upsilon _2, \Upsilon _4\}\) only contain one non-zero element. Furthermore, the specified vector from the set \(\Gamma\) with one part of AI bits and the specified vector from the set \(\Upsilon _\ell , \ell \in \{1,2,3,4\}\) with the other one part of AI bits are constructed into one space vector to modulate one 3D signal CP symbol, resulting in one transmitted space vector (TSV). Furthermore, to increase the squared minimum Euclidean distance between the TSVs, the modified secondary 3D signal constellation is designed. Finally, the bit error probability is analyzed and experimental verifications are provided to prove that the proposed SM-EIV-T3DC outperforms the existing schemes such as signed quadrature spatial modulation (SQSM), spatial modulation with spatial constellation (SM-SC), quadrature index modulation with three dimension constellation (QIM-TDC) in terms of bit error rate (BER) performance.
