Quadrature Spatial Modulation Research Articles

Joint switch controlling and subvectors permutation for quadrature index modulation with hybrid constellations

AbstractIn this paper, the switch and permutation index domains are developed for improving the spectral efficiency (SE) and the reliability of wireless communication. Firstly, a new schematic of quadrature index modulation with hybrid constellation (QIM‐HC) is proposed to exploit the switch index domain. In the QIM‐HC system, all transmit antennas (TAs) are divided into multiple groups. In each group, with the control of one Switch, the symbol index bits are fed into the specific modulator and mapped into a data symbol. Then, the real and imaginary parts of the data symbol are respectively modulated by two selected antenna index (AI) vectors with two blocks of AI bits, resulting in the transmit vector. Furthermore, another new design, jointing permutation index and hybrid constellation for the QIM system (JPQIM‐HC), whose each group transmits different number of data symbols with the control of different number of switches, is proposed to develop the permutation index domain for further improving the SE. Finally, the analysis of the SE and the bit error probability are analyzed. Simulation results show a close match with theoretical results at the high signal noise ratio (SNR) region, and show the improvement of the bit error rate (BER) performance for the the proposed systems as compared with the other schemes such as signed quadrature spatial modulation.

Deep learning based signal detection for quadrature spatial modulation system

Deep learning based signal detection for quadrature spatial modulation system

On the Capacity of Generalized Quadrature Spatial Modulation

On the Capacity of Generalized Quadrature Spatial Modulation

CNN-based automatic modulation recognition for index modulation systems

Automatic modulation recognition (AMR) has garnered significant attention in both civilian and military domains, with applications ranging from spectrum sensing and cognitive radio (CR) to the deterrence of adversary communication. Index modulation (IM) represents an innovative digital modulation technique that exploits the indices of parameters of communication systems to transmit extra information bits. This paper aims to examine the performance of a convolutional neural network (CNN)-based AMR across various IM systems, including spatial modulation (SM), quadrature spatial modulation (QSM), and generalized spatial modulation (GSM) with eight digital modulation schemes. In this study, we leverage confusion matrices, receiver operating characteristic (ROC) curves, and F1 scores to illustrate the recognition model’s outputs.

Physical Layer Security for Frequency Diverse Array-Based Dual-Hop Spatial Modulation

In this paper, we design the physical layer security of a dual-hop spatial modulation system provided the relay node transmits its own private information. Meanwhile, the quadrature virtual channel spatial modulation (QVCSM) is proposed to enhance the physical layer security in the second hop. To achieve system security in both angle and range dimensions, the frequency diverse array (FDA) is used in the relay node with a decode-and-forward (DF) protocol. Moreover, the baseband directional modulation (DM) and artificial noise (AN) are jointly utilized to suppress the received signal at the passive eavesdropper. Additionally, the Ergodic secrecy rate of the proposed system is analyzed, whereas the closed-form expressions for tight upper bounds on the bit error rates (BERs) of the source and relay are derived for both the destination and eavesdropper. The simulation results show that the proposed FDA relay design outperforms the traditional phase array (PA) relay system in terms of the system secrecy rate. In contrast to the quadrature spatial modulation (QSM) method, the proposed designs achieve an improved suppression performance of the eavesdropper.

RIS-Assisted Receive Quadrature Spatial Modulation With Low-Complexity Greedy Detection

RIS-Assisted Receive Quadrature Spatial Modulation With Low-Complexity Greedy Detection

Impact of channel imperfections on variant SMTs MIMO systems over revised Nakagami-[formula omitted] channel model

Recently, a revised model for the Nakagami-m multiple-input multiple-output (MIMO) channel has been proposed, yielding distinct results and conclusions compared to the existing model. This article focuses on evaluating and discussing the performance of MIMO space modulation techniques (SMTs) transmission schemes, namely space shift keying (SSK), quadrature space shift keying (QSSK), spatial modulation (SM), and quadrature spatial modulation (QSM), over the revised channel model. The evaluation considers spatial correlation, imperfect channel state information (CSI), and examines various performance metrics such as average bit error rate (ABER), mutual information, and capacity. Specifically, a closed-form expression for the ABER is derived under the assumption of a maximum-likelihood (ML) receiver. Additionally, formulas for mutual information and capacity are derived and thoroughly discussed. To validate the derived formulas, extensive Monte Carlo simulations are performed. Furthermore, the impact of system parameters on the ABER, mutual information, and capacity is investigated, providing a comprehensive analysis of their variations. A comparative study is conducted between different transmission schemes using the revised model, elucidating their relative performance. Moreover, a comparison is made between the reported results of the revised model and the existing Nakagami-m model, as well as other channel distributions such as Rayleigh and Rice fading channels. The findings clearly demonstrate the disparities between the existing and revised models, with the revised model exhibiting superior performance. Notably, when comparing the scenario of m=1 with a Rayleigh fading channel, an exact match is observed for the revised channel model, while some differences are detected for the existing model.

Index modulation aided generalized space-time block coding: A unified MIMO framework

In this paper, Index Modulation (IM) aided Generalized Space-Time Block Coding (GSTBC) is proposed, which intrinsically exploits the benefits of IM concept, diversity gain and spatial multiplexing gain. Specifically, the information bits are partitioned into U groups, with each being modulated by IM symbols (i.e. Spatial Modulation (SM), Quadrature SM (QSM),etc). Next, the structure of GSTBC is invoked for each K IM symbol, and a total of μ = U/K GSTBC codes are transmitted via T time slots. A Block Expectation Propagation (B-EP) detector is designed for the proposed IM-GSTBC structure. Moreover, the theoretical Average Bit Error Probability (ABEP) is derived for our IM-GSTBC system, which is confirmed by the simulation results and helpful for performance evaluation. Simulation results show that our proposed IM-GSTBC system is capable of striking an efficient trade-off between spatial multiplexing gain, spatial diversity gain as well as implementation cost imposed for both small-scale and large-scale MIMO antenna configurations.

OFDM-based 2D generalized optical quadrature spatial modulation for MIMO-OWC systems

An innovative scheme, named orthogonal frequency division multiplexing (OFDM)-based two-dimensional (2D) generalized optical quadrature spatial modulation (GOQSM), is proposed for bandlimited multiple-input multiple-output optical wireless communication (MIMO-OWC) systems. In this scheme, by way of combining two consecutive time slots into one time block, 2D GOQSM mapping can be executed in spatial domain and time domain. Therefore, more spatial bits can be transmitted, resulting in the increase of system spectral efficiency. Furthermore, discrete Fourier transform (DFT) spreading is further introduced in OFDM-based 2D GOQSM systems, so as to substantially reduce the peak-to-average power ratio (PAPR) of the transmitted signals. To evaluate and compare the performance of OFDM-based 2D GOQSM systems with other traditional systems, numerical simulations are conducted under various spectral efficiencies. The obtained simulation results prove that the proposed OFDM-based 2D GOQSM scheme with DFT spreading can achieve better bit error rate performance and lower PAPR than other benchmark schemes.

Quadrature spatial modulation based orthogonal time frequency spatial system

In this paper, we take the spatial and delay-Doppler dimensions into account and propose a novel transmission scheme combining quadrature spatial modulation (QSM) and orthogonal time frequency space (OTFS) to improve the spectral efficiency, achieve the diversity gains, and resist strong Doppler effect in high-mobility scenes. The system model and the specific signal transmission process of the OTFS with QSM (QSM-OTFS) scheme are presented first. Then, the theoretical average bit error rate (ABER) analysis for QSM-OTFS system is provided. Additionally, a linear enhanced minimum mean square error (EMMSE) detection is investigated to reduce the detection complexity in the QSM-OTFS system. Numerical results illustrate that the QSM-OTFS system is able to obtain an improved ABER performance compared with the typical spatial modulation (SM) based OTFS (SM-OTFS) and that the proposed EMMSE detection outperforms the other linear detection algorithms under the same spectral efficiency.

Performance analysis of signed quadrature spatial modulation system over Nakagami-m fading channels with spatial correlation

Novel performance analysis of the recently proposed signed quadrature spatial modulation (SQSM) multiple-input–multiple-output (MIMO) system is presented in this paper. This study covers the effects of Nakagami-m fading channels for different m values and the impact of spatial correlation impairment. The pairwise error probabilities (PEP) of SQSM over Nakagami-m fading channel with and without spatial correlation effects are computed. Moreover, a tight upper bound of average bit error ratio (ABEP) is derived. Monte Carlo simulation results for a wide range of signal to noise ratios (SNR) are introduced to corroborate the accuracy of the theoretical analyses. The performance of SQSM is compared with the quadrature spatial modulation (QSM) system.

Flexible Quadrature Spatial Pulse Amplitude Modulation for VLC Systems

Quadrature-spatial modulation (QSM) offers high spectral efficiency (SE) without interchannel interference for both radio frequency and visible light communication (VLC) systems. In this article, a new QSM scheme called flexible quadrature spatial pulse amplitude modulation (FQSPAM) is proposed for VLC systems. In space modulation techniques (SMTs), the data bit stream is divided into two groups as the index bits and the signal bits. These grouped bits are mapped independently to modulation symbols and indices of light-emitting diodes (LEDs). However, this mapping strategy puts a constraint on the number of LEDs and the size of the signal constellation. FQSPAM jointly designs the signal and spatial components of the constellation to overcome these limitations. This approach removes the constraint on the number of LEDs and the size of the signal constellation. The constellation design problem is formulated as a convex optimization problem to identify power-efficient constellations with different <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula> values. A dimming-controlled optimization algorithm has also been proposed to take into account both illumination and communication at the same time. Analytical and numerical results show the improved bit error rate performance of the proposed FQSPAM compared to spatial pulse amplitude modulation and channel adaptive bit mapping.

Error performance analysis of generalized quadrature spatial modulation using H-8QAM

Motivated to enhance the error performance (EP) of generalised complex quadrature spatial modulation (GCQSM) systems, this study proposes a scheme that builds on GCQSM and uses hexagonal quadrature amplitude modulation (H-QAM) constellations which have the advantages of a maximised Euclidean distance with relatively low peak-to-average power ratio, compared to conventional QAM (C-QAM) systems. This in turn, leads to an enhancement of the EP of GCQSM schemes. The proposed scheme utilises a rotated hexagonal 8QAM (H-8QAM) set. Thus, the proposed scheme is herein named; Generalised QSM using H-8QAM (GQSM-H-8QAM). In this study, the EP of the proposed GQSM-H-8QAM scheme is investigated over Rayleigh frequency flat-fading channels with additive white Gaussian noise. Additionally, a theoretical average bit error probability (ABEP) expression of the GQSM-H-8QAM scheme is formulated and validated using Monte Carlo simulations. Compared to simulation results, the ABEP proves to be increasingly tight at high signal-to-noise ratio values. Obtained simulation results also show an improvement in the EP of the GQSM-H-8QAM scheme over various SM schemes like GCQSM, C-QSM and conventional-generalized spatial modulation (C-GSM), at the same spectral efficiency (SE). An improvement in the EP of 0.61 dB with SE of 8 bits/s/Hz is seen in 4times 4 GQSM-H-8QAM over 4times 4 GCQSM using C-8QAM, 2.58 dB over 4times 4 C-QSM-C-64QAM and a gain of 4.85 dB over 4times 4 C-GSM-C-64QAM.

Optimal Low Complexity Detector for Signed-Quadrature Spatial Modulation MIMO System

Very recently, signed quadrature spatial modulation (sQSM) is developed as a competent technique that expands the spatial constellation diagram of QSM system by adding a bipolar dimension. Despite the enhanced spectral efficiency, the existing optimal maximum likelihood (ML) presents a serious computational challenge for large scale sQSM systems. Therefore, developing a reduced complexity detector for sQSM schemes is of significant importance to enable implementing and enjoying the inherent advantages of this promising system. Toward this end, a Tree Search (TS) optimal low complexity detector, called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TSopt</i> , for sQSM Multiple Input Multiple Output (MIMO) system is proposed and analyzed in this paper. The proposed detector expands the computationally complex ML detector for sQSM into a tree-structure representation. The idea of the suggested algorithm is to employ an efficient searching strategy that can expeditiously find the branch corresponding to the minimum error without tracing the entire nodes as in the ML case. It is reported that the proposed TSopt algorithm achieves the exact error performance as ML detector but with substantial reduction in computational complexity. Besides, complexity analysis in terms of the number of visited nodes of the TSopt algorithm is analyzed and a closed-form expression for the expected complexity at high SNR values is derived. Reported results disclose agreement between simulation and expected analytical complexity with substantial gains of around 60–80% in complexity reduction for different system parameters.

Quadrature Spatial Modulation With the Fourth Order Transmit Diversity and Low-Complexity Sphere Decoding for Large-Scale MIMO Systems

A quadrature spatial modulation with the fourth order transmit diversity (FO-QSM) scheme is presented in this paper. In this scheme, two dispersion-matrix (DM) sets are assigned at the transmitter, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P$</tex-math></inline-formula> out of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> DMs are activated in each set to extend the real and imaginary parts of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P$</tex-math></inline-formula> QSM signals respectively, to large number of transmit antennas. The two DM sets are constructed by performing Kronecker product between two simple extension matrices and the DMs of Sezginer-Sari-Biglieri (SSB) code. The framework designs of FO-QSM and the two DM sets make FO-QSM possess the properties: 1) it guarantees the fourth order transmit diversity without requiring any parameter optimization; 2) it has higher spectral efficiency than the newly proposed generalized space-time block coded spatial modulation (GSTBC-SM) scheme. Furthermore, a repeated computation reduced sphere decoding (RCR-SD) is proposed. RCR-SD is very suitable for the schemes constructed by a large number of DMs, including FO-QSM. By sorting the index vectors, the RCR-SD detector can efficiently reduce the repeated computations in the SD searching, which significantly reduces the decoding complexity without sacrificing optimal decoding performance. Simulation results show that FO-QSM has obvious better bit error rate (BER) performance than GSTBC-SM.

Quadrature Spatial Modulation Aided Media-Based Modulation

In this work, we present the concept of quadrature spatial modulation aided media-based modulation (QSM-MBM), which combines QSM and MBM principles. The proposed two QSM-MBM schemes use dispersion matrices to generate QSM matrix and transmit it by designing two different channel state activation methods, which provides improved transmission rate, diversity gain as well as hardware simplicity. Simulations show that the proposed QSM-MBM schemes achieve remarkably better error performance than the existing MBM schemes.

Intelligent Reflecting Surface Assisted Transceiver Quadrature Spatial Modulation

In this letter, we employ quadrature spatial modulation (QSM) in both transmitter and receiver with the assistance of an intelligent reflecting surface (IRS), which we refer to as IRS-transceiver QSM (IRS-TQSM). In the compressive sensing (CS) framework, we cast the receiver processing as a sparsity recovery problem and propose a low-complexity algorithm by coupling the energy detector (ED) with convex programming (CP), referred to as ED-CP. The out-performance of the proposed IRS-TQSM with ED-CP compared to closely related works is demonstrated with numerical results.

Performance of modified generalized quadrature spatial modulation over correlated fading channels with imperfect channel information

AbstractA generalized version of the quadrature spatial modulation (QSM) scheme is called a modified generalized QSM (mGQSM), which is proposed to enhance the spectral efficiency of QSM by considering multiple radio frequency chains. In QSM, the in‐phase and quadrature dimensions are used to transmit the data symbols. Using the QSM transmission principle, the mGQSM scheme can transmit the data symbols on different antennas ranging from to . Moreover, the proposed scheme provides an additional one bit data rate when compared to generalized QSM (GQSM). This paper presents the performance of mGQSM under imperfect channel conditions over correlated Rayleigh, Rician, and Nakagami‐m fading channels. For the computer simulations, we assume and various fading parameters for the Rician and Nakagami channels. The error performances of the mGQSM, GQSM, and QSM schemes are evaluated using the maximum‐likelihood (ML) detector. Under imperfect channel conditions, the mGQSM and QSM schemes are examined and compared. Furthermore, a low complexity ordered block minimum mean‐squared error (OB‐MMSE) detector is employed for the reduced‐codebook mGQSM (RC‐mGQSM), which achieves near‐ML performance with reduced complexity.

The Achievable Rate Analysis of Generalized Quadrature Spatial Modulation and a Pair of Low-Complexity Detectors

Generalized quadrature spatial modulation (GQSM) seamlessly amalgamates the generalized spatial modulation (GSM), quadrature spatial modulation (QSM) and vertical Bell Laboratories layered space-time (V-BLAST) techniques. In contrast to traditional multiple-input multiple-output (MIMO) schemes transmitting information bits only through the constellation defined on the complex plane, GQSM transmits additional information bits implicitly by selecting the transmit antenna (TA) activation pattern. The philosophy of QSM is that of separating the indices of the real and the imaginary parts of the transmit symbols, which increases the attainable throughput. In this paper, we analyze the inherent benefits of GQSM in terms of throughput. More specifically, we first derive the achievable rate expression of the recent GQSM scheme and unveil the condition for GQSM to approach the maximum rate. Furthermore, we compare the rate of the GQSM scheme to that of other transmission schemes and reveal the conditions for the GQSM&#x2019;s maximum throughput to exceed that of the benchmark schemes. Simulation results show that when the number of TAs is 40 and quadrature phase shift keying (QPSK) is adopted, the rate of the GQSM scheme may reach 150&#x0025; of that of V-BLAST. Additionally, a pair of low-complexity detectors are conceived-one based on ordered successive interference cancellation (OSIC) and another one on the orthogonal matching pursuit (OMP) algorithm.

Hybrid Transmitter Hardware Models for Reliable Implementations of Space Modulation Techniques

Space modulation techniques (SMTs) are multiple-input multiple-output (MIMO) transmitter system implementations that have shown to achieve favorable properties compared to existing MIMO technologies. This includes properties such as lower power consumption, cost, and enhanced error performance. As modern wireless standards have come to demand also more reliability and less latency, in recent work analyzing the reliability of SMTs, it was shown that existing SMT implementations do not effectively perform under degraded system conditions. Essentially, under certain failure conditions, parts of SMT systems become unusable although still effectively operational. As a result, affecting the best achievable spectral efficiency, and thus system data rate of the system. In this work, novel SMT implementations are presented and referred to as hybrid SMTs (HSMTs). HSMTs are designed to degrade in a manner that keeps use of operational hardware and maintains a higher spectral efficiency for longer duration. Four different HSMTs are presented namely; hybrid space shift keying (HSSK), hybrid spatial modulation (HSM), hybrid quadrature space shift keying (HQSSK), and hybrid quadrature spatial modulation (HQSM). Additionally, a reliability analysis framework for HSMTs is presented using two different analytical tools and all introduced models are comparatively studied.