Modulation Diversity for Spatial Modulation Using Complex Interleaved Orthogonal Design

In this paper, we propose modulation diversity techniques for Spatial Modulation (SM) system using Complex Interleaved Orthogonal Design (CIOD) meant for two transmit antennas. Specifically, we show that by using the CIOD for two transmit antenna system, the standard SM scheme, where only one transmit antenna is activated in any symbol duration, can achieve a transmit diversity order of two. We show with our simulation results that the proposed schemes offer transmit diversity order of two, and hence, give a better Symbol Error Rate performance than the SM scheme with transmit diversity order of one.Comment: 7 page

Hybrid beamforming in mm-wave MIMO systems having a finite input alphabet

Recently, there has been significant research effort toward achieving high data rates in the millimeter wave bands by employing large antenna systems. These systems are considered to have only a fraction of the RF chains compared with the total number of antennas and employ analog phase shifters to steer the transmit and receive beams in addition to the conventional beamforming (BF)/combining invoked in the baseband domain. This scheme, which is popularly known as hybrid BF, has been extensively studied in the literature. To the best of our knowledge, all the existing schemes focus on obtaining the BF/combining matrices that maximize the system capacity computed using a Gaussian input alphabet. However, this choice of matrices may be suboptimal for practical systems, since they employ a finite input alphabet, such as quadrature amplitude modulation/phase-shift keying constellations. Hence, in this paper, we consider a hybrid BF/combining system operating with a finite input alphabet and optimize the analog as well as digital BF/combining matrices by maximizing the mutual information (MI). This is achieved by an iterative gradient ascent algorithm that exploits the relationship between the minimum mean-squared error and the MI. Furthermore, an iterative algorithm is proposed for designing a codebook for the analog and digital BF/combining matrices based on a vector quantization approach. Our simulation results demonstrate that the proposed gradient ascent algorithm achieves an ergodic rate improvement of up to 0.4 bits per channel use (bpcu) compared with the Gaussian input scenario. Furthermore, the gain in the ergodic rate achieved by employing the vector quantization-based codebook is about 0.5 bpcu compared with the Gaussian input scenari

Structured Dispersion Matrices From Division Algebra Codes for Space-Time Shift Keying

We propose a novel method of constructing Dispersion Matrices (DM) for Coherent Space-Time Shift Keying (CSTSK) relying on arbitrary PSK signal sets by exploiting codes from division algebras. We show that classic codes from Cyclic Division Algebras (CDA) may be interpreted as DMs conceived for PSK signal sets. Hence various benefits of CDA codes such as their ability to achieve full diversity are inherited by CSTSK. We demonstrate that the proposed CDA based DMs are capable of achieving a lower symbol error ratio than the existing DMs generated using the capacity as their optimization objective function for both perfect and imperfect channel estimation

Antenna Selection in Spatial Modulation Systems

Novel transmit antenna selection techniques are conceived for Spatial Modulation (SM) systems and their symbol error rate (SER) performance is investigated. Specifically, low-complexity Euclidean Distance optimized Antenna Selection (EDAS) and Capacity Optimized Antenna Selection (COAS) are studied. It is observed that the COAS scheme gives a better SER performance than the EDAS scheme. We show that the proposed antenna selection based SM systems are capable of attaining a significant gain in signal-to-noise ratio (SNR) compared to conventional SM systems, and also outperform the conventional MIMO systems employing antenna selection at both low and medium SNRs