Signal Vector Design for Quadrature Index Modulation

Abstract

In this paper, we propose a new technique of quadrature index modulation with signal vector design (QIM-SSD), which can directly transmit a three-dimensional (3D) constellation symbol and expand an antenna index (AI) bit. The basic principle of QIM-SSD is as follows: two components of a mapped 3D signal symbol are first modulated on the upper and lower parts of transmit antennas (TAs) by two specific AI vectors with two blocks of AI bits, respectively, resulting in a space vector symbol. The remaining one component is modulated on one TA activated by the specific AI vector with one block of AI bits, then forming another space vector symbol. Furthermore, based on the resulted two space vector symbols, an additional bit is used to determine the real and imaginary parts of a complex transmit vector. The research of this paper is summarized as follows: firstly, the system model of QIM-SSD is introduced in detail. Then, the minimum Euclidean distance and the average bit error probability (BEP) are analyzed. With assumption of perfect channel estimation and maximum likelihood (ML) detection, simulation results demonstrate that the average BEP performance of QIM-SSD is better than that of the conventional QIM with three dimensional constellation and QSM at the same spectral efficiency by MATLAB simulator.