Spatial Modulation Scheme Research Articles

Generalized Space-Code Index Modulation for High Rate and Energy-Efficient MIMO Transmission

In this paper, we propose a novel generalized space-code index modulation (GSCIM) scheme for spectrum-efficient and energy-saving transmission. In our proposed scheme, the input information bits are transmitted not only by modulated symbols, but also by the activated transmit antennas pattern and the selected spreading code patterns for the in-phase and quadrature components. Due to the increase of the index dimension, more information bits can be implicitly transmitted, which can improve energy efficiency and have a higher data rate compared with spatial modulation (SM), generalized SM (GSM), generalized CIM-aided SM (GCIM-SM) and CIM-aided quadrature spatial modulation (CIM-QSM). In order to further reduce the complexity of despreading-based maximum likelihood (ML) detection, we propose an enhanced low-complexity detector that can achieve near-ML error performance. An analytical upper bound on the average bit error probability associated with the optimal ML detection is derived, which is verified by simulation results. Simulation results also show that the proposed GSCIM scheme outperforms SM, GSM, GCIM-SM and CIM-QSM schemes in terms of error performance.

Double generalized spatial modulation

AbstractIn this article, motivated by the enhanced spatial modulation and quadrature spatial modulation (QSM) systems, we proposed a new design of double generalized spatial modulation (DGSM), which further exploits the spatial domain not only for the transmission of more extra information bits by increasing the number of antenna index (AI) vectors in an AI vector set, but also for the achievable transmit diversity gain. In DGSM system, we first design the in‐phase and quadrature AI vector sets, whose each AI vector having one or more than one nonzero element equaling to “1” is used for the activation of one or more than one transmit antenna. Then, a spatial antenna index vector (SIV) is generated by adding an AI vector from the in‐phase AI set and another AI vector from the quadrature AI set. Furthermore, a data symbol (eg, QAM/PSK) is modulated on the SIV for forming multiple versions of the data symbol and then transmitted, the maximum likelihood (ML) and sphere decoder (SD) algorithm are applied for the DGSM system. Finally, the performance analysis, including in the spectral efficiency, the computational complexity comparison between the DGSM system with SD algorithm and the diversity‐achieving QSM (DA‐QSM) with ML detector, are provided. Also, the average bit error probability is analyzed. Simulation results using Monte Carlo are presented to show the improvement of bit error ratio performance in comparison with DA‐QSM and other spatial modulation schemes.

Performance analysis of RIS-assisted SM with I/Q imbalance

The idea of utilizing reconfigurable intelligent surfaces (RISs) that employ an array of severally-controllable meta-material elements to scatter incoming data in a desirable way, in wireless communication systems has created new opportunities for transmission in various scenarios. For instance, RISs are envisioned as potential candidates to achieve smart radio environments in fifth generation (5G) network technology, which is usually described as incapable of controlling the environment. Nevertheless, existing studies analyzing RIS-empowered wireless networks generally discuss the cases with ideal hardware despite the fact that both physical transceiver and RISs suffer from unignorable hardware imperfections, which may exceedingly reduce the system performance in practical communication scenarios. This paper investigates the performance of an RIS-assisted spatial modulation (SM) scheme in the presence of in-phase/quadrature-phase imbalance (IQI) at the base station (BS) constituting a substantial impairment in direct-conversion transceivers. The concept of the RIS-assisted SM scheme is discussed by comparing three different implementation scenarios depending on the awareness of both the channel phases at the RIS and the severity of the IQI at the destination (D). The average bit error rate (ABER) is derived analytically by use of maximum likelihood (ML) detection method to tackle the distorting impact of the IQI taking the effects of path loss into account. Extensive computer simulation results, which verify theoretical findings, show that the performance of the traditional SM schemes with IQI can remarkably be improved by utilizing RISs, while having the knowledge of the adjusted phases at the receiver (Rx) provides substantial gain in terms of energy.

Successive-Coded Spatial Shift Keying Modulation for MIMO Wireless Communications

Spatial domain modulation employs spatial degree of freedom to convey information bits. Traditional spatial domain modulation schemes include spatial modulation, spatial shift keying (SSK), and variations of these two schemes. To fully make use of the spatial degree of freedom and improve the achievable data rate of traditional spatial domain modulation schemes, we propose a successive-coded SSK (SC-SSK) modulation scheme. The core of the proposed SC-SSK scheme is a multiple step coded modulation strategy, in which different information bits are mapped to the designed pattern in each step. The constellation of the transmit signals is designed. A QR decomposition based successive detection algorithm is proposed for this particular coded modulation strategy. The achievable rate, the error rate performance, and the computational complexity of the proposed SC-SSK scheme are analyzed in detail. Simulations are carried out to compare the proposed the SC-SSK scheme with the reference spatial domain modulation schemes, and reveal the advantages of the proposed SC-SSK scheme.

Spatial Modulation for RIS-Assisted Uplink Communication: Joint Power Allocation and Passive Beamforming Design

In this paper, we investigate the uplink communication of a reconfigurable intelligent surface (RIS) assisted system, in which an user equipment (UE) with single radio frequency (RF) chain delivers information to an access point (AP) by adopting the spatial modulation (SM). Specifically, we first investigate the transmit SM (TSM) scheme and jointly optimize the UE’s power allocation matrix and the RIS reflection coefficients to enhance the system reliability. We formulate a non-convex optimization problem to reduce the system symbol-error-rate (SER) and propose a novel penalty-alternative optimizing algorithm to obtain a near-optimal solution. Following this, we show that with the assistant of RIS, receive SM (RSM) scheme can also be performed even if the UE has only one RF chain. Based on this observation, a novel RIS-assisted RSM scheme is proposed, which can provide a low cost and complexity solution for system realization. The reflection coefficients of the RIS are also optimized for the proposed RSM. Numerical results show that the RIS-assisted TSM can achieve a lower SER than the conventional communication scheme (CTS) without SM and the proposed RSM scheme has lower detection complexity than that of CTS. It is also shown that the performance of the TSM and RSM schemes is more sensitive to the quantization accuracy of the phase of the RIS coefficients than that of the amplitude.

Differential STBC-SM Scheme for Uplink Multi-User Massive MIMO Communications: System Design and Performance Analysis

In this paper, a novel differential space-time block coded spatial modulation (differential STBC-SM) is proposed for uplink multi-user massive multiple-input multiple-output (MIMO) communications, which combines the concept of differential coding and STBC-SM to enhance the diversity benefits in the absence of the channel state information (CSI). The transmission structure of the proposed system is on a block basis, where each block contains two sub-blocks. More specifically, the first sub-block only conveys amplitude and phase modulation (APM) symbol bits, since its transmit antennas (TAs) obey a pre-designed activation pattern, which do not carry any information bit. For the second sub-block, the input bits are modulated to STBC-SM matrices, which are then differentially coded between two adjacent sub-blocks. Moreover, a novel block-by-block based non-coherent detector is presented. Finally, we derive an upper bound on the average bit error probability (ABEP) by using the moment generating function (MGF). Our simulation results show that the proposed differential STBC-SM transmission structure is able to acquire considerable bit error rate (BER) performance improvements compared to both the conventional differential spatial modulation (DSM) and differential Alamouti schemes.

Reconfigurable Intelligent Surface-Based Symbiotic Radio for 6G: Design, Challenges, and Opportunities

Energy efficiency (EE) and spectrum efficiency (SE) are two key performance metrics in the sixth generation (6G) wireless communication networks due to the ultra-massive connectivity requirements in future Internet of Things scenarios such as smart cities and factories. Reconfigurable intelligent surface (RIS)-based symbiotic radio (SR) is a promising technology to simultaneously achieve high EE and SE. In this article, a comprehensive review of the RIS-based SR system is presented including the system architectures, operating principles, technical advantages, application scenarios and state-of-the-art transceiver design. Moreover, a star-QAM-aid-ed joint spatial modulation scheme is proposed to realize RIS-based SR and simulation results are provided to illustrate the performance of the proposed scheme. Finally, the critical design challenges for the implementation of RIS-based SR and some promising future research directions are discussed.

Double Spatial Modulation with Transmit Antenna Group for Communication Signal Transmission

In this paper, to make use of the idle transmit antennas for the improvement of multiplexing gain and the spectral efficiency, a new design of double spatial modulation (DSM) with transmit antenna group (DSM-TG) is proposed. More specifically, all of transmit antennas are grouped into G groups, each group implements a DSM system independently. Then, by using the vector combiner, G groups of DSM symbol vectors are constructed into a transmitted spatial vector. Furthermore, the average bit error ratio is analyzed. Finally, to make a fair comparison, simulation results are presented for the transmission of same data rate, and show the proposed DSM-TG achieves the better bit error rate (BER) performance gain as compared with other spatial modulation schemes.

Group-Based LED Selection for Generalized Spatial Modulation in Visible Light Communication

Visible light communication (VLC) systems have attracted considerable attention in recent years. However, it still faces the challenges of user mobility and random device orientation, which will result in unreliable connection and performance degradation. In this letter, we propose a group-based LED selection aided generalized spatial modulation (GLS-GSM) scheme to tackle this issue by preventing some poor LEDs from communication. Firstly, the LEDs are divided into several equal-sized groups. Then, each group conducts Euclidean distance-based LED selection (ED-LS) and spatial modulation (SM) independently. Moreover, an ED-based grouping criterion is exploited to search for an optimal grouping strategy. The bit error rate (BER) performance of the proposed scheme is evaluated for sitting and walking activities. Numerical simulation results demonstrate the effectiveness of the proposed method.

Modified generalized quadrature spatial modulation performance over Nakagami‐m fading channel

SummaryThe modified generalized quadrature spatial modulation (mGQSM) scheme is introduced to improve the transmission rate of the spatial modulation (SM) and quadrature SM (QSM). In mGQSM, the information symbols are separated as real and imaginary coefficients, which are modulated on in‐phase and quadrature dimensions, respectively. In addition, this scheme presented a novel codebook design to enhance the rate of 1 bit per channel use over generalized QSM (GQSM). In this paper, we present mGQSM and reduced codebook mGQSM (RC‐mGQSM) system performances over Nakagami‐m, Rayleigh, and Rician fading channels. However, the Rayleigh fading is a special case of Nakagami‐m fading when m = 1. For the computer simulations, we use several values for the Nakagami parameter, m, and Rician factor, K. We present the mGQSM and RC‐mGQSM system performances and compare them to the GQSM, QSM, and SM system performances, using the maximum‐likelihood (ML) detection. For the RC‐mGQSM scheme, we present a low‐complexity detection method. We also present the performances of mGQSM and SM systems in the presence of imperfect channel conditions.

A Differential Modulation Scheme for Metasurface-Based Terahertz Communications

Metasurface-based terahertz (THz) modulators, which carry information by changing the spatial pattern of the metasurface at every symbol time, are an important component to establish low-cost low-energy–consuming THz communication systems. This paper proposes a differential spatial THz modulation (DSTM) scheme for metasurface-assisted THz communications. In DSTM, the metasurface pattern activation orders are employed to carry information, instead of the metasurface patterns themselves. In this way, the DSTM receiver can perform differential detection without knowing the metasurface response to incident THz signals and the channel state information. The proposed DSTM scheme is applicable to all kinds of metasurfaces enabling THz communications, including transmissive metasurfaces and reflective metasurfaces. For high-rate DSTM systems, we propose an efficient bits-to-activation-order mapping method and a low-complexity detection method. Simulations are conducted to demonstrate the performance of the proposed scheme. It is shown that the proposed scheme pays acceptable penalty compared to the non-differential modulation scheme with coherent detection, which needs to know the metasurface response to the incident signals as well as all the channel state information.

Channel Estimation for Spatial Modulation Schemes in Spatially Correlated Time Varying Channels

In this paper, we propose a channel estimation scheme for spatial modulation (SM) systems. In general, SM systems require each transmit antenna to separately send pilot symbols for channel estimation. This is a lengthy process, which may incur significant channel estimation errors in a time varying channel. Thus, we propose correlation-based channel estimation (CBCE) scheme, which exploits the correlation between transmit antennas to estimate channels of inactive antennas using the pilot-based estimate of the active antenna. The change in the active channel from the last pilot-based estimate is calculated, and a time-proportionate amount of that change is scaled according to the channel correlation coefficients to estimate the channel state of the inactive channels. With pilot slots designed to spread out in a data frame, the estimation process for every channel is carried out N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> times in a data frame with N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> denoting the number of transmit antennas. We observe that in a high signal-to-noise ratio (SNR) regime, our proposed scheme provides about 2 dB and 5 dB gains compared to conventional channel estimation (CCE) method for moderately correlated and highly correlated antennas, respectively. Through Monte Carlo simulations with different correlation ρ and user speeds, we validate our analysis and show that the proposed scheme outperforms CCE when ρ ≥ 0.3, while it provides comparable performance for small ρ.

Multi-Antenna Selection for Double Spatial Modulation

In this paper, to exploit the spatial domain of transmit antennas (TAs) for the transmit diversity gain in the double spatial modulation (DSM) system, a new scheme of multi-antenna selection for DSM (MAS-DSM) is designed. In the MAS-DSM system, the number of TAs are grouped into n groups, each of which corresponds to an sub-system of DSM. More specifically, a transmitted spatial vector is constructed by two spatial vectors (SVs). For the achievability of transmit diversity gain, one of the two SVs is obtained by using n antenna index (AI) vectors to modulate a data symbol, another of them is obtained by multiplying with a rotation angle after another n AI vectors to modulate another data symbol. Finally, the spectral efficiency and the average bit error ratio (BER) are analyzed. Simulation results by using Monte Carlo demonstrate that the proposed MAS-DSM system has better BER performance compared with the conventional spatial modulation schemes in wireless communication network.

Performance evaluation of RIS-based SSK and SM schemes with perfect and imperfect channel phase estimation over Weibull fading channels

In this paper, we present the re-configurable intelligent surfaces (RIS) based space shift keying (SSK) and spatial modulation (SM) schemes with both perfect and imperfect channel phase knowledge over Weibull fading environments. At the receiver, we consider the sub-optimal Greedy Detection (GD) for proposed RIS-based SSK and SM schemes. Central Limit Theorem (CLT) caused by RIS schemes facilitates to adopt of a unified framework for error performance analysis of Weibull fading channels without loss of generality. In this study, it has been obtained the theoretical bit error probability (BEP) of the proposed schemes. It should be underlined that unlike the literature, the BEP of the proposed schemes is formulated in the presence of a Gaussian imperfect phase estimation at RIS. These analytical results were then validated with Monte-Carlo Simulations under the various system settings (e.g., the severity of fading parameters, number of reflectors, different antenna numbers).

A deep learning-based concept for high throughput image flow cytometry

We propose a flow cytometry concept that combines a spatial optical modulation scheme and deep learning for lensless cell imaging. Inspired by auto-encoder techniques, an artificial neural network mimics the optical transfer function of a particular microscope and camera for certain types of cells once trained and reconstructs microscope images from simple waveforms that are generated by cells in microfluidic flow. This eventually enables the label-free detection of cells at high throughput while simultaneously providing their corresponding brightfield images. The present work focuses on the computational proof of concept of this method by mimicking the waveforms. Our suggested approach would require a minimum set of optical components such as a collimated light source, a slit mask, and a light sensor and could be easily integrated into a ruggedized lab-on-chip device. The method is benchmarked with a well-investigated dataset of red blood cell images.

Fully Generalized Spatial Modulation utilizing Transmit Antenna Grouping

One of the recently modified multiple-input multiple-output (MIMO) systems is the spatial modulation (SM). Although SM is considered as MIMO in its composition, a single antenna at the transmitting side is activated at any time instant. Among all transmitting antenna, the selection of this active antenna isn't random but rather chosen based on extra bits, called spatial bits, transmitted besides the conventional digitally modulated bits. In addition to the transmission of additional bits, SM wireless communication system achieves an enhanced power efficiency, low error rate, low complexity at receiver, and completely inter-channel interference (ICI) elimination. On the other side, SM suffers from the dramatic increase in the number of required transmit antennas to achieve a small improvement in data rate and low spectral efficiency when compared with multiplexing MIMO (Mux-MIMO). The exponential increase in the data rate of the SM scheme became linear thanks to the fully generalized spatial modulation scheme (F-Gen-SM). Although the F-Gen-SM scheme overcame one of the SM disadvantages, the achievable data rate still low when compared with Mux-MIMO. Grouping generalized spatial modulation scheme (Gr-Gen-SM) tries to find a compromise between the advantage of SM and the high spectral efficiency of Mux-MIMO. Gr-Gen-SM achieves high spectral efficiency but loses most of the SM advantages. This paper introduces a new F-Gen-SM scheme utilizing the idea of dividing transmit antennas into groups (F-Gr-Gen-SM). This proposed scheme provides an improvement on data rate while preserving the advantages of SM as much as possible.

Double Antenna-Transitions Spatial Modulation Performance Evaluation Over Nakagami- m Wireless Fading Channels

Recently, a novel spatial modulation (SM) scheme; termed Mid-symbol Antenna transition (MAT) spatial modulation, was developed to reduce the number of utilized transmitting antennas and improve the average bit error rate (ABER) performance. In this paper, the structure of the original MAT is extended to adapt Double-antenna transitions (DAT) during the symbol's transmission duration. Compared to the mid-symbol antenna-transition (MAT), the DAT scheme allows more reduction in the number of required transmitter antennas (TAs) and more enhancement of ABER performance, while achieving the same spectral efficiency (SE). DAT scheme reduces receiver complexity in comparison with generic SM, generalized SM (GSM), variable generalized SM (VGSM), and MAT schemes. The detailed DAT system design is presented. Furthermore, the theoretical closed-form of the ABER upper bound of the DAT system is quantified. The validity of the derived ABER upper bound is proved by contrasting it with the simulated ABER. Monte-Carlo simulations are utilized to evaluate the ABER of the DAT scheme over nakagami-m fading channels with respect to competing schemes. Furthermore, we study the impact of the spatial correlation on the considered schemes and the impact of varying nakagami-m factor on the performance of the DAT scheme. Our simulations demonstrate that DAT significantly outperforms the aforementioned rival schemes in terms of the average bit error rate (ABER) performance.

Norm-based user selection algorithm for single-RF space modulation techniques with geometric mean decomposition based precoding scheme

Joint user selection algorithm and fully digital geometric mean decomposition (GMD)-based precoding scheme is considered in this paper for single radio frequency (RF) space modulation techniques (SMTs), namely, spatial modulation (SM) and space shift keying (SSK) schemes. The objective is to jointly perform the Frobenius norm-based user selection algorithm and design GMD-based precoded SMTs with single-RF chain in order to reduce the cost and the power consumption in multiple input multiple output (MIMO) systems, and to avoid the complicated bit-allocation problem of singular value decomposition (SVD)-based precoding technique. Based on these schemes, the GMD-based precoding transmission carried out in the context of a single-user SMTs can readily be extended to the multi-user (MU) case. Simulation results demonstrate that single-RF SMTs with GMD-based precoding scheme is capable of outperforming SMTs with SVD-based precoding technique. Meanwhile, MU-SMTs with GMD-based precoding scheme provide significant performance gains over the conventional SM- and SSK-MIMO counterparts and single-user SMTs with GMD-based precoding algorithm, which increase the energy efficiency and the reachability using these schemes. Furthermore, better error performance in MU-SMTs with fully digital GMD-based precoding technique is obtained by selecting any number of users. Therefore, MU-SMTs with GMD-based precoding scheme can be effectively used in various 5G wireless networks.

Optical Improved Quadrature Spatial Modulation for Cooperative Underwater Wireless Communication under Weak Oceanic Turbulence Conditions

Amplify-and-forward cooperative underwater optical wireless communication employing optical improved quadrature spatial modulation (OIQSM) is proposed in this study. It uses multiple signal constellations, thereby improving the system performance. It uses multiple lasers but it activates only a few of them depending on the message bits and can transmit double modulated symbols in a single symbol interval. The OIQSM system performance is compared in terms of bit error rate (BER) with other existing schemes in the literature. The analysis is conducted for weak oceanic turbulence conditions, which is generally prevalent in deep oceans. The cost and power consumption analysis of OIQSM is performed to highlight its benefits over other schemes. It is observed that OIQSM yields a signal-to-noise ratio gain of at least 5.5 dB over the conventional optical spatial modulation scheme for any BER value between and .

Downlink Multi-User Massive MIMO Transmission Using Receive Spatial Modulation

In this paper, we consider the downlink of a multi-user multiple-input-multiple-output system operating at the millimeter wave band in an outdoor environment. In this band, receive spatial modulation (RSM) schemes have been shown to achieve good spectral efficiency-energy consumption trade-off for the single-user case by exploiting new transceiver architectures that use a single radio-frequency (RF) chain at the user terminal (UT). In this work, we propose a novel RSM scheme for multiple RF chains at the UT. With the goal of maximizing the spectral efficiency (SE), we consider analog switches at the UT that select which antennas are active. To minimize the power consumption at the BS, we include analog switches that control the ON/OFF status of RF chains such that the SE is higher than a given threshold. Moreover, we extend the RSM concept to multiple users transmission. Specifically, we propose an algorithm that jointly optimizes the number of users, set of antennas and transmit power allocated to each user to maximize the sum SE. Simulation results show that RSM outperforms conventional modulation (no spatial symbols are transmitted) in terms of spectral and energy efficiency. Moreover, the proposed algorithms tightly approach the exhaustive search and outperform the prior art in terms of performance and convergence.