Multidimensional Index Modulation in Wireless Communications

In index modulation schemes, information bits are conveyed through indexing of transmission entities such as antennas, subcarriers, times slots, precoders, subarrays, and radio frequency (RF) mirrors. Index modulation schemes are attractive for their advantages such as good performance, high rates, and hardware simplicity. This paper focuses on index modulation schemes in which multiple transmission entities, namely, {\em antennas}, {\em time slots}, and {\em RF mirrors}, are indexed {\em simultaneously}. Recognizing that such multidimensional index modulation schemes encourage sparsity in their transmit signal vectors, we propose efficient signal detection schemes that use compressive sensing based reconstruction algorithms. Results show that, for a given rate, improved performance is achieved when the number of indexed transmission entities is increased. We also explore indexing opportunities in {\em load modulation}, which is a modulation scheme that offers power efficiency and reduced RF hardware complexity advantages in multiantenna systems. Results show that indexing space and time in load modulated multiantenna systems can achieve improved performance

Multidimensional Generalized Quadrature Index Modulation for 5G Wireless Communications

Multidimensional generalized quadrature index modulation scheme is proposed in this paper for conveying extra digital information with the aid of the space, radio frequency (RF) mirrors, and time indices. Explicitly, this proposed scheme cleverly combines another proposed time-indexed generalized quadrature spatial modulation (TI-GQSM) system with media-based modulation (MBM) transmission principle using RF mirrors, and it is referred to as TI-GQSM-MBM scheme. This scheme is attractive because of both the high data rate and the significant performance improvements that can be achieved. The system performance of the proposed schemes in terms of the bit error rate (BER) is evaluated and compared to the performance of the conventional schemes. Simulation results showed that a significant improvement is achieved by the TI-GQSM-MBM scheme as compared to that of TI-GQSM, time-indexed media-based modulation (TI-MBM) and the conventional generalized quadrature spatial modulation (GQSM) schemes for the same rate. It is also demonstrated that the proposed schemes are robust to channel estimation errors (CEEs) as compared to multidimensional generalized spatial modulation (GSM) schemes. Therefore, the proposed schemes can be effectively used as an alternative solution for various 5G and beyond wireless networks

Time-indexed Media-based Modulation

Media-based modulation (MBM) is a promising modulation scheme which is attracting recent research attention. In MBM, radio frequency (RF) mirrors are used to create a channel modulation alphabet based on the ON/OFF (i.e., transparent/opaque) status of these mirrors. The index of the mirror activation pattern in a channel use conveys information bits in addition to the bits conveyed through conventional modulation symbols. MBM has been shown to achieve improved performance compared to conventional modulation schemes. In this paper, we introduce time-slot indexing to MBM, which further improves the performance. The proposed time-indexed MBM (TI-MBM) is a block transmission scheme, where a time slot in a given frame can be used or unused, and the choice of the slots used for transmission conveys time-index bits. We study the proposed TI-MBM scheme in frequency-selective channels and show that TI-MBM achieves better performance compared to conventional MBM. Further, recognizing that the TI-MBM signal structure promotes sparsity, we exploit the use of sparse recovery algorithms for the detection of TI-MBM signals. We show that compressive sampling matching pursuit (CoSaMP) and subspace pursuit (SP) based TI-MBM signal detection can achieve significantly improved performance compared to conventional minimum mean square (MMSE) detection