Circular Space-Time Block Code Design for Ultra-Reliable Index Modulation Schemes

In this paper, a novel circular space-time block coding (CSTBC)-based index modulation (IM) technique, which achieves various orders of transmit diversity gains, is introduced. In the proposed system, a promising IM concept, media-based modulation (MBM), which carries additional information bits through the available radio frequency (RF) mirrors of transmit antennas, is considered. Unlike traditional STBC-based IM concepts, the proposed technique provides various orders of transmit diversity gains and attains higher spectral efficiency values with a single RF chain. The bit error rate (BER) performance of the proposed system is theoretically analyzed and an upper bound expression for the average bit error probability (ABEP) is derived. Moreover, via comprehensive computer simulations, the improved BER performance of the proposed CSTBC-IM is demonstrated over the-stateof-the-art IM schemes.