Spatial Modulation Multiple-input Multiple-output Research Articles

Low Complexity Optimal and Suboptimal Detection at Spatial Modulation MIMO Receivers

This paper develops three low-complexity detection schemes for the spatial modulation (SM) Multiple Input Multiple Output (MIMO) systems. We first propose a reduced complexity maximum likelihood (RC-ML) detection scheme. For the practical values of the modulation index, the proposed RC-ML method is simpler than the existing hard-limiting-based ML schemes. The two other proposals are based on a suboptimal Maximum Ratio Combining (MRC) detection method. We present a new analysis of the MRC detector in the uncorrelated Rayleigh fading channel and identify the system operational scenarios for which the MRC performance is nearly identical to the ML performance. Our proposals — a hybrid MRC-ML method and an MRC scheme with rank reduction — are inspired by this analysis. The analytical and simulation results show that the proposed MRC-based schemes can attain a near-optimal performance while reducing the complexity of the ML-based SM receiver.

Historical Development of Spatial Modulation and Massive MIMO Communication System with Implementation Challenges: A Review

: For wireless communication networks, massive MIMO (Multiple-Input Multiple- Output) technology has been considered a major achievement. MIMO Technology consists of equipping a base station with a large number of antennas to serve many active users. Through MIMO Technology, the ability to concentrate on transmitted signal energy in very short spaces would result in huge increases in system capacity. While this new concept provides some fascinating benefits, it creates a new tension that has drawn both academia and industry attention. Channel state information acquisition, channel feedback, instant reciprocity, statistical reciprocity, architecture and hardware impairments are few of them. This paper presents a survey on Spatially Modulated Massive MIMO's historical development.

A Two-Stage Clustering Detector for SM-MIMO Communications

In this letter, we propose a novel two-stage clustering detector for spatial modulation multiple-input multiple-output (SM-MIMO) systems. Firstly, the quality of the clustering result (i.e., cluster centroids) of the conventional KMC detector will be checked through the proposed rule in the first stage. Then, with the aid of the good cluster centroids of the bad clustering result and the symmetry property of the good cluster centroids, the bad cluster centroids are obtained from the first stage will be corrected to good cluster centroids in the second stage. Furthermore, a new two-stage clustering detector is proposed correspondingly. Our simulation results show that the proposed two-stage clustering detector outperforms other clustering detectors and is capable of achieving near maximum-likelihood (ML) performance with considerably low complexity.

Symmetry-Aided Clustering Blind Detection in Spatial Modulation Systems

This paper considers the blind detection of spatial modulation multiple-input multiple-output (SM-MIMO) systems based on clustering algorithms. Firstly, we propose a novel framework (framework 1) that can guarantee the excellent detection performance of clustering detectors to implement the signal detection even if in the case of short block length by considering the rotational symmetry of digital modulation constellations. Then, we propose a novel rule by defining the concept of pseudo rotational symmetry of cluster centroids, which can check the quality of the cluster centroids of clustering algorithms. Besides, based on the proposed rule, we investigate two scenarios and propose framework 2 and framework 3 for the problems in the scenarios. Specifically, the framework 2 can early terminate the clustering algorithms that are performed multiple times different initializations to avoid poor detection performance, and it significantly reduces computational complexity while maintaining excellent performance. The framework 3 can adjust the data length of clustering algorithms according to different environmental conditions that can improve the detection efficiency while improving performance. Moreover, the proposed framework 1 can be combined with proposed framework 2 or framework 3, which further enhances the detection performance. In addition, we conduct the performance analysis for the SM-MIMO systems when the perfect channel state information (CSI) is unavailable. Simulation results demonstrate the clustering detectors combined with proposed frameworks behave better than the clustering detectors without the proposed frameworks in terms of performance or complexity.

Transmit antenna selection for spatial modulation MIMO IoT networks with full-duplex relaying

Recent advances in 5G wireless technology, including multiple-input multiple-output (MIMO) systems and full-duplex communications, have opened the gate for Internet of Things (IoT) applications, especially for wireless sensor nodes to collect and transfer data between environment and control center. This study analyzes the deployment of transmit antenna selection (TAS) in spatial modulation (SM) MIMO full-duplex relaying (FDR) system (SM-MIMO-FDR), where relay uses decode-and-forward (DF) protocol. Due to the computational complexity, TAS was usually neglected in previous studies on SM-MIMO system, especially when FDR is employed in the system. Here, we derive the exact form of outage probability (OP) and symbol error rate (SER) to indicate the performance of SM-MIMO-FDR system with TAS over Rayleigh fading channel. A comparison between SM-MIMO-FDR with TAS and conventional SM-MIMO-FDR shows a significant performance enhancement. Also, this study includes the impact of antenna quantity, data transmission rate, and residual self-interference (RSI) on the OP and SER through derived mathematical expressions. Finally, the correctness of the analysis is verified by numerical results through Monte Carlo simulations.

Structure Radio Beam Construction in Azimuthal Domain

Structure radio beams with diverse radiation patterns exhibit huge potentials in many applications. In this paper, we propose a plane spiral orbital angular momentum (PS-OAM) based structure radio beam construction scheme, in which several PS-OAM waves are superposed together to acquire the anticipated radiation pattern and phase distribution in azimuthal domain. Firstly, some typical shapes of the radiation patterns are demonstrated. Then, the properties of this kind of structure radio beam, for example diversity, periodicity, vorticity and directional gain are analysed in detail from mathematical analysis and simulation verification. Finally, a proof of principle experiment is carried out at 10 GHz using a multi PS-OAM antenna to further testify the feasibility of the structure radio beam construction. The interesting properties provided by structure radio beams would offer promising solutions to radar imaging, smart antenna, massive multiple input multiple output (MIMO) and spatial modulation multiple input multiple output (SM-MIMO).

Performance Analysis of Variant MIMO Systems Over 3-D Vehicular to Vehicular Channel

This article analyzes the performance of variant multiple-input multiple-output (MIMO) systems over three-dimensional (3D) vehicular to vehicular (V2V) wireless communication channel. In particular, quadrature spatial modulation (QSM), spatial multiplexing (SMX) and spatial modulation (SM) MIMO techniques are considered. A unified framework to analyze the average bit error rate (BER) for all considered MIMO techniques is developed while considering the 3D geometry dependent stochastic V2V channel model and substantiated through Monte Carlo simulation results. Reported results corroborate the accuracy of the derived formulas and the impact of different system and channel parameters is studied. Specifically, the encroachment of Doppler effect, channel estimation errors, 3D features and vehicle traffic density (VTD) on the BER performance of all systems are examined and discussed. It is revealed that QSM system achieves substantial gains as compared to its counterpart SM and SMX schemes. Gains of up to 2-4 dB in signal-to-noise-ratio are reported for different scenarios.

On the Performance of Full-Duplex Spatial Modulation MIMO System With and Without Transmit Antenna Selection Under Imperfect Hardware Conditions

Hardware impairments (HI) due to imperfect manufactured electronic parts degrade the performance of wireless systems. In this paper, we consider a bidirectional full-duplex (FD) spatial modulation (SM) multiple-input multiple-output (MIMO) system with non-ideal hardware and residual self-interference (RSI). We propose to use the transmission antenna selection (TAS) as a solution to mitigate this degradation. The performance of the considered system is analyzed using mathematical analysis. Specifically, we first derive the exact closed-form expressions of the outage probability (OP), symbol error probability (SEP), and achievable data rate (ADR) for two cases: with and without TAS. Given these expressions, we conduct a detailed evaluation of the system performance under various scenarios to gain insight into its behavior. Essential conclusions are then made on HI and RSI’s impacts, especially for the case with TAS and high transmission rates.

Adaptive Spatial Modulation MIMO Based on Machine Learning

In this paper, we propose a novel framework of low-cost link adaptation for spatial modulation multiple-input multiple-output (SM-MIMO) systems-based upon the machine learning paradigm. Specifically, we first convert the problems of transmit antenna selection (TAS) and power allocation (PA) in SM-MIMO to ones-based upon data-driven prediction rather than conventional optimization-driven decisions. Then, supervised-learning classifiers (SLC), such as the K -nearest neighbors (KNN) and support vector machine (SVM) algorithms, are developed to obtain their statistically-consistent solutions. Moreover, for further comparison we integrate deep neural networks (DNN) with these adaptive SM-MIMO schemes, and propose a novel DNN-based multi-label classifier for TAS and PA parameter evaluation. Furthermore, we investigate the design of feature vectors for the SLC and DNN approaches and propose a novel feature vector generator to match the specific transmission mode of SM. As a further advance, our proposed approaches are extended to other adaptive index modulation (IM) schemes, e.g., adaptive modulation (AM) aided orthogonal frequency division multiplexing with IM (OFDM-IM). Our simulation results show that the SLC and DNN-based adaptive SM-MIMO systems outperform many conventional optimization-driven designs and are capable of achieving a near-optimal performance with a significantly lower complexity.

Effect of Wiring and Cabling Topologies on the Performance of Distributed MIMO OFDM VLC Systems

Since most indoor spaces have multiple luminaires for illumination, for visible light communication (VLC) systems, multiple-input multiple-output (MIMO) communication emerges as a natural solution to improve the data rates and/or the link reliability. The existing works on MIMO VLC systems, however, overlook the characteristics of the lighting infrastructure and the luminaire design, which might have implications for the VLC system design. A luminaire typically consists of multiple LED chips. The wiring topology refers to how the LED chips are connected within the luminaire. The cabling topology, on the other hand, refers to how the luminaires are connected to the communication access point (AP). Based on the type and length of cabling and wiring, significant delays can be introduced, which should be taken into account in channel modeling. In this paper, we adopt the non-sequential ray tracing to model the distributed MIMO VLC channels for various practical wiring and cabling topologies. Based on the developed channel models, we provide a comparative performance analysis of repetition coding (RC), spatial multiplexing (SMUX), and spatial modulation (SMOD) MIMO modes. Our results quantify the effect of wiring/cabling delays and provide insights into the optimized design of lighting infrastructure and luminaires for the support of VLC as an add-on service.

Performance of Generalized Spatial Modulation MIMO Over Measured 60GHz Indoor Channels

In this paper, we study the capacity and symbol error probability (SEP) of generalized spatial modulation (GSM) multiple-input multiple-output (MIMO) using measured channels that are obtained by channel sounding in an indoor office environment at 60GHz. Spatial modulation (SM) and GSM are emerging low-complexity MIMO schemes that have been extensively researched for low-GHz (below 6GHz) communications. Recently, they have been considered and shown to be promising also for (mmWave) communications. In the simplest possible case, they require only one RF chain both at the transmitter (TX) and receiver (RX), and thus, are especially attractive for mmWave communications, in which the number of RF chains needs to be as low as possible. Despite of some early works on the theoretical analysis of SM/GSM for mmWave communications, there have been no investigations using real-world channel data. We focus on the office line-of-sight (LOS) scenario and investigate three problems: 1) the performance of GSM using the extracted LOS component of measured channels; 2) the impact of non-LOS NLOS components on the performance of GSM; and 3) possible simple modulation and reception algorithms for GSM that rely only on the LOS component of the channel. The results being reported in this paper not only validate the main claims of previous studies based on ideal pure LOS channels, but also lead to novel findings. One major conclusion is that NLOS components are harmful to the SEP of GSM and should be avoided. As another important outcome, our results strongly motivate the use of precoding in GSM systems to simultaneously improve the channel capacity and reduce the physical size of MIMO arrays (thus eliminating one major issue of LOS GSM).

Adaptive SM-MIMO for mmWave Communications With Reduced RF Chains

In this paper, a novel multiple-input multiple-output (MIMO) transmission scheme, termed as receive antenna selection (RAS)-aided spatial modulation MIMO (SM-MIMO), is proposed for millimeter-wave (mmWave) communications. It employs the spatial modulation (SM) concept and the RAS technique to tackle the costs of the multiple radio frequency (RF) chains at both link ends. Moreover, we develop a pair of RAS algorithms for the proposed mmWave RAS-SM scheme based on the capacity maximization (max-capacity) and the bit-error rate (BER) minimization criteria, which are formulated as two combinatorial optimization problems. The theoretical gradients of the capacity and the BER with respect to RAS variables are derived and the convexities of these problems are discussed. Furthermore, a novel iterative algorithm through jointly designing the log-barrier algorithm (LbA) and the simplified conjugate gradient method is proposed for RAS optimization. Our simulation results show that the proposed RAS-SM schemes are capable of achieving considerable performance gains over conventional norm-based and eigenvalue-based schemes in mmWave MIMO channels, while avoiding an overwhelming complexity imposed by exhaustive search.

On the Performance of Spatial Modulation MIMO for Full-Duplex Relay Networks

In this paper, we investigate, for the first time, the performance of a full-duplex (FD) relaying protocol, where a single-RF spatial modulation (SM) multiple-input multiple-output (MIMO) system is employed at the relay node. We refer to this protocol as SM-aided FD relaying (SM-FDR). At the destination, a demodulator that takes advantage of the direct connectivity between the source and destination is developed in order to maximize its performance. Based on this demodulator, we introduce a mathematical framework for computing the average error-probability of SM-FDR in the presence of residual self-interference (SI). Furthermore, we derive mathematical expressions for computing the achievable rate of SM-FDR. With the aid of these achievable rate expressions, we provide an estimate on the quality of SI cancellation required for the suitability of FD transmission. In addition, we develop and evaluate three relay selection policies specifically designed for the SM-FDR protocol. The mathematical analysis is substantiated with the aid of extensive Monte Carlo simulations. Finally, we also assess the performance of SM-FDR against traditional FD relaying protocols.

Performance Analysis of Massive Spatial Modulation MIMO in High-Speed Railway

For high-speed railway (HSR), an essential characteristic of the propagation channels is the specific spatial–temporal correlation caused by a dominant strong line-of-sight (LOS) component. Multiple-antenna gain is therefore far from being achieved due to this strong channel correlation. However, it is interesting to note that if the resulted intercarrier interference (ICI) is elaborately controlled, high mobility may decrease the channel correlation. Spatial modulation (SM) is one of the promising multiple-antenna technologies for wireless communication systems, which needs only the activation of one transmit antenna to convey information bits implicitly through the index of the active transmit antenna, in addition to conveying information bits through modulation symbols during transmission. In SM, ICI is avoided, which therefore helps in the implementation of the idea of decreasing channel correlation by increasing the velocity in an HSR scenario. In this paper, the performance of massive SM multiple-input multiple-output (MIMO) over a spatial–temporal correlated Rician fading channel is investigated under an HSR scenario. The impacts of velocity, Rician factor K, and signal-to-noise ratio (SNR) are discussed. In addition, the correlation factor and the correlation comparison function are defined as metrics of channel correlation. We theoretically find out that higher velocity makes the impact of temporal correlation more dominant, which weakens the influence of spatial correlation. In other words, spatial correlation can be weakened by high mobility. Our theoretical analysis and simulations further demonstrate that, with an appropriate scheme, massive SM MIMO outperforms Vertical Bell Laboratories Layered Space–Time (VBLAST), except at a lower SNR region with high velocity (usually more than 360 km/h). Consequently, massive SM MIMO is a promising solution within an appropriate range of velocity for HSR wireless communication systems.

Implementation of a Near-Optimal Detector for Spatial Modulation MIMO Systems

This brief presents a hardware implementation of a detector for spatial modulation multiple-input multiple-output (SM-MIMO) communication systems. The proposed detector employs the signal-vector-based list detection method, but the original method is modified to realize a low-complexity implementation. In addition, the proposed detector is designed based on the dual-data-path architecture, in which antenna selection and symbol detection are separately performed with different precision levels to reduce the hardware complexity while achieving a near-optimal error-rate performance. The proposed detector is implemented with 87.4-K logic gates in a 0.18- $\mu\text{m}$ CMOS technology, and its throughput is 858 Mb/s for 8 $\times$ 4 64 quadrature amplitude modulation SM-MIMO systems, where the operating frequency is 286 MHz, and the power consumption is 121.3 mW. This manifests that the proposed detector is very efficient with respect to the gate count as well as the energy consumption.

Impact of Cochannel Interference on the Performance of Quadrature Spatial Modulation MIMO Systems

Quadrature spatial modulation (QSM) was proposed recently as a viable multiple-input multiple-output (MIMO) communication technique for future wireless systems. QSM expands spatial modulation to include both real and imaginary spatial constellation symbols. In this letter, we consider an arbitrary QSM MIMO system operating over Rayleigh fading channels and in the presence of additive white Gaussian noise and cochannel interference (CCI). The performance of the system is analyzed mathematically and numerically. In particular, a closed-form expression for the pairwise error probability is derived assuming arbitrary number of CCIs and used to calculate an upper bound on the average error probability. As well, an asymptotic expression, which is shown to be tight at practical SNR values is derived. Analytical results are sustained through Monte Carlo simulations and impact of different system parameters is studied. In addition, performance comparison between QSM, spatial modulation, spatial multiplexing, and single antenna transmission schemes for the same spectral efficiency and in the presence of CCI is presented.

Fast detection for spatial modulation MIMO based on cost estimation

Aiming at fast hardware processing, a detection algorithm for multiple-input multiple-output (MIMO) systems that employ spatial modulation (SM), or SM-MIMO, is proposed. Conventional SM-MIMO detection inherently suffers from the nearsightedness as it depends only on the cost of the preceding path that has been traversed. To overcome such a drawback, the proposed detection traverses the tree by taking into account not only the cost of the preceding path but also the estimated cost of the sub-tree that has not been visited yet. Compared to conventional methods, as a result, the proposed algorithm significantly reduces the number of visits that determines the latency in hardware, making it suitable to hardware implementation.

Low-complexity soft-decision aided detectors for coded spatial modulation MIMO systems

In this paper, we present an efficient transmission scheme for multiple-input multiple-output (MIMO) systems, i.e., coded spatial modulation (SM) systems with soft-decision aided detector. To exploit the powerful error correction of channel coding, the key challenge of coded SM systems is on designing a reliable but low-complexity soft-output detector. Fighting against this problem, we first propose two soft-output detection algorithms by exploiting the features of M-phase-shift keying (PSK) and M-quadrature amplitude modulation (QAM) constellations, namely, PSK-based soft-output detector (PBSD) and QAM-based soft-output detector (QBSD). Furthermore, to further enhance the performance of the two algorithms, we propose another two soft-output detection algorithms taking into account of counterpart maximum-likelihood (ML) estimate, namely, improved PSK-based soft-output detector (IPBSD) and improved QAM-based soft-output detector (IQBSD). The findings of this paper demonstrate that: (1) The computational complexity of PBSD and QBSD algorithms are much lower than that of Max-Log-LLR algorithm at the expense of error performance. (2) Both the IPBSD and IQBSD algorithms achieve the same performance as Max-Log-LLR algorithm with reduced computational complexity. In addition, a comprehensive performance and computational complexity comparison between the proposed algorithms and the Max-Log-LLR algorithm is provided to verify our proposed low-complexity soft-output detectors.

Low-Complexity ML Detection for Spatial Modulation MIMO With APSK Constellation

Spatial modulation (SM) is a promising multiple-input–multiple-output (MIMO) transmission technology, which exploits the indexes of the transmit antennas for encoding information into the spatial dimension and, thus, for increasing the transmission rate. Optimal demodulation is realized by using a maximum-likelihood (ML) detector, which jointly estimates the information bits encoded into the transmit antenna indexes and into the transmitted symbol. If a large number of transmit antennas and/or a large modulation size are used; however, the computational complexity of ML demodulation may not be affordable for some applications. Against this background, we propose two novel near-ML but low-complexity detection schemes for SM-MIMO systems, which use $\boldsymbol{M}$ -ary amplitude and phase-shift keying (APSK) digital modulation. The proposed algorithms exploit specific features of the $\boldsymbol{M}$ -ary APSK constellation diagram, in order to avoid searching among all constellation points. It is shown, in particular, that the complexity of the proposed detection schemes is independent of the constellation size and that it only depends on the number of rings that constitute the APSK constellation. Simulation results are also provided, which confirm that the proposed detection schemes provide bit error probability performance close to that of ML demodulation but with lower demodulation complexity.

PERFORMANCE ANALYSIS OF SPATIAL MODULATION IN MIMO- A SURVEY

Spatial modulation (SM) is a recently developed transmission technique that uses index of antenna in a multiple input multiple output (MIMO) antenna system, as additional means of data transmissions. The use of index of the active antennas at any time instant is the main idea behind spatial modulation. The information bits to be transmitted are divided into two parts. The first part is mapped to a symbol chosen from the signaling constellation, where depending on modulation scheme the number of bits per symbol varies. The second part determines the antenna index to be selected from a set of antennas available for data transmission. Thereby increases the spectral efficiency and decreases the complexity at receiver section. The rate of data transmission can much more increased by mapping into subsets of antennas in MIMO. The paper summarizes some of the recent works and issues of SM MIMO. The antenna selection in spatial modulation mainly depends on the incoming information data which is unlike the antenna selection in conventional MIMO system which depends on the channel state information (CSI) and the received signal strength.