Multiple-input Multiple-output Transmission Scheme Research Articles

Differential optical spatial modulation with pulse position modulation over atmospheric turbulence

Optical spatial modulation (OSM), a recent optical multiple-input multiple-output transmission scheme in wireless optical communication, has aroused great research interests. OSM scheme requires accurate channel state information (CSI) during transmitter and receiver sides, but it is difficult to accurately estimate CSI in OSM scheme. Therefore, a scheme named differential optical spatial modulation scheme with pulse position modulation (DOSM-PPM) based on the space-time mapping block of orthogonal design is proposed in order to completely avoid CSI estimation. The bit error rate (BER) performance of DOSM-PPM is analyzed under log-normal turbulent channel model and simulated using Monte Carlo method. The results show that the transmission rate of DOSM-PPM is improved effectively. Meantime, the proposed DOSM-PPM scheme outperforms DOSM scheme with spatial pulse amplitude modulation by 1 dB at 1 × 10 − 3 BER with the same spectrum efficiency.

Generalized Code Index Modulation and Spatial Modulation for High Rate and Energy-Efficient MIMO Systems on Rayleigh Block-Fading Channel

In this article, a high data rate and energy-efficient multiple-input multiple-output transmission scheme is considered by combining two popular and rational modulation techniques: spatial modulation (SM) and code index modulation-spread spectrum (CIM-SS). Since in the considered system, called generalized CIM-SM (GCIM-SM), incoming information bits determine modulated symbols, activated transmit antenna indices as well as their corresponding spreading code indices, data bits are conveyed not only by modulated symbols but also by the indices of the active antenna and spreading codes. Hence, a GCIM-SM scheme accommodates faster data rates while spending less transmission power and possessing better error performance compared to the conventional direct sequence spread spectrum (DS-SS), SM, quadrature SM (QSM), and CIM-SS systems. The mathematical expressions of the GCIM-SM system for bit error rate, throughput, energy efficiency, and the system complexity are derived to analyze the overall system performance. Besides, it has been shown via computer simulations that the GCIM-SM system has lower transmission energy, faster data transmission rate, and better error performance than DS-SS, SM, QSM, and CIM-SS systems. Performance analysis of the considered system was performed on Rayleigh block-fading channels for quadrature amplitude modulation technique.

Spatial-polarization diversity HAP-MIMO transmission system for emergency high-capacity mobile communications

The deployment of high-altitude platforms (HAPs) as an emergency communication system is a cost-effective method to deal with the decrease in channel capacity caused by shadows or multipath fading at low elevation angles. This study proposes a 4 × 4 multiple-input multiple-output (MIMO) scheme that employs spatial and polarization diversity to improve the channel capacity for HAP communication systems. This scheme utilizes the advantages of HAP size to install two pairs of dual-polarized antennas between HAP and mobile terminals to form a 4 × 4 spatial-polarized diversity MIMO system to counteract shadows and multipath fading. The polarization and spatial correlation matrices are obtained through the reasonable expansion of a 2 × 2 polarized parametric or spatial geometry MIMO channel model. Simulation results show that the proposed 4 × 4 MIMO transmission scheme can effectively improve the channel capacity by 1.5 times compared with the existing satellite 2 × 2 dual-polarization MIMO system at low elevation angles under typical scenarios.

Cooperative MIMO-OFDM based inter-vehicular visible light communication using brake lights

Inter-vehicular connectivity to enhance road safety and support highly autonomous driving is increasingly becoming popular. Despite the prevalent works on radio-frequency (RF) based vehicular communication schemes, visible light communication (VLC) is considered to be a promising candidate for vehicular communications due to its low complexity and RF interference-free nature. Deployment of multiple light emitting diodes (LEDs) enables multiple-input multiple-output (MIMO) transmission in the context of vehicular VLC. This paper investigates applicability of both point-to-point (direct) vehicular VLC and decode-and-forward relaying based cooperative vehicular VLC including relay terminals between source and destination terminals to enhance road safety based on real world measurements. We consider direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) based MIMO transmission scheme and evaluate the performances of different MIMO modes including repetition code (RC) and spatial multiplexing (SM), different modulation orders with different transmitter–receiver selection mechanisms to support line-of-sight (LoS) and beyond LoS multi-hop vehicular VLC. The results reveal that the selection of the closest transmitters to the receivers provides better performance due to high signal-to-noise-ratio requirements for RC mode whereas SM suffers from channel correlation. Usage of all possible transmitters does not always yield better performance due to the power division at the transmitter side. On the other hand, the performance of RC shows more degradation on higher-order modulations that are required to yield the same throughput with SM. Therefore, considering the higher order modulation requirement for RC based VLC, SM is concluded to be a favorable MIMO scheme for cooperative vehicular VLC. We further demonstrate the benefits of multi-hop transmission over direct transmission with respect to different number of relay vehicles as a consequence of varying inter-vehicular distances between source and destination vehicles.

Theoretical Performance of Coherent and Incoherent Detection for Zero-Forcing Receive Antenna Shift Keying

Receive antenna shift keying (RASK) is a multiple-input multiple-output transmission scheme that applies the spatial modulation concept at the receiver. Zero-forcing (ZF) precoding can be used at the transmitter side to steer the signal toward the targeted antenna. Different detection schemes can be implemented in order to detect the RASK information. Moreover, for the sake of low complexity and low power consumption, decreasing the number of RF chains by the use of switched antennas can also be implemented. In this paper, we lead a theoretical analysis of the transmission of spatial symbols in RASK, using the ZF precoding. Two detection schemes relying on maximum likelihood (ML) detection are presented and proved to be implemented as a simple single-tap detector. One, called coherent ML (CML), needs one RF chain per receive antenna and the other one, named incoherent ML (IML), is based on an envelope detector and needs only one RF chain for the entire antenna array. Theoretical expressions of the bit error rate (BER) are derived for each scheme and validated through simulation. The CML detector is demonstrated to obviously outperform the IML detector in terms of the BER but at the cost of higher complexity and power consumption. We then proposed to use switches to reduce the number of RF chains, thus trading off some performance against complexity. At some point, IML is shown to outperform CML, depending on the number of switches, RF chains, and system configuration. This turning point is analytically calculated and validated through simulations, and so can be used for further system comparison studies.

Performance Analysis of MMSE Pre-Coding Aided Spatial Modulation

Pre-coding aided spatial modulation (PSM) constitutes a flexible closed-loop multiple-input multiple-output transmission scheme, which attracts substantial research interest recently. In this paper, an upper bound of the average bit error probability (ABEP) for the PSM system based on the minimum mean square error (MMSE) pre-coding is investigated. In addition, a theoretical analysis is given based on the assumption that the numbers of transmit and receive antennas are large but their ratio $\theta $ is constrained. Furthermore, the theoretical analysis shows that the ABEP upper bound of the PSM system based on MMSE pre-coding depends only on ratio $\theta $ . Simulation results demonstrate that the upper bound is asymptotically tight as the signal-to-noise ratio increases, and the proposed system outperforms its benchmark that is based on zero-forcing pre-coding.

Performance Study of MIMO Transmissions with Joint Channel Allocation and Relay Assignment

Multiple-input multiple-output (MIMO) techniques have shown numerous benefits in improving communication reliability and spectrum efficiency in wireless communication. In this paper, performance of MIMO transmission schemes with joint channel allocation and relay assignment (JCARA) in MIMO cooperative cognitive radio network (CRN) is studied. The problem of maximizing the spectrum efficiency among multiple CR source–destination pairs under different number of antenna configurations is studied. In order to improve the spectrum efficiency, multiple antennas are exploited at cognitive radio (CR) sources, CR relays, and CR destinations in a cooperative CRN . In this concern, we obtain the spectrum efficiency for various settings of MIMO maximum ratio transmission (MIMO-MRT) and MIMO transmit antenna selection (MIMO-TAS) schemes, which are applied at CR transmitter (i.e., CR sourc/relay) and maximum ratio combining (MRC) is applied at CR receivers (i.e., CR relay/destination), with JCARA. Extensive numerical results are presented to show the effectiveness of the MIMO-MRT and MIMO-TAS schemes. It is also shown that as the number of transmit–receive antenna increases the spectrum efficiency of both the MIMO-MRT and MIMO-TAS schemes increases as compared to single transmit–receive antenna case. Moreover, it is shown that relay assignment offers more benefit of maximization of minimum transmission rate with the MIMO-TAS scheme than the MIMO-MRT scheme.

A New Filter-Bank Multicarrier System With Two Prototype Filters for QAM Symbols Transmission and Reception

A filter-bank multicarrier-quadrature amplitude modulation (FBMC-QAM) system with two prototype filters for transmitting QAM symbol is proposed, and the orthogonality conditions for the FBMC-QAM system without the intrinsic interference is derived. The proposed transmitter performs the individual filtering for the even and odd-numbered sub-carrier symbols, respectively. In order to satisfy the derived orthogonality conditions, we perform a sub-block wise reverse ordering procedure for the outputs of the odd-numbered sub-carrier filter. Also, this paper shows that the proposed FBMC-QAM system satisfies the suggested orthogonality conditions and can use the multiple-input multiple-output transmission schemes as the conventional orthogonal frequency division multiplexing (OFDM) systems. The signal-to-interference power ratio and the bit error rate (BER) for the proposed FBMC-QAM system are evaluated. Numerical results show that the proposed FBMC-QAM system has almost the same BER performance compared with the FBMC-OQAM and OFDM systems.

Low‐complexity detection of quadrature spatial modulation

Quadrature spatial modulation (QSM) is a recently proposed multiple-input multiple-output transmission scheme which improves the spectral efficiency of classical spatial modulation (SM) by increasing the number of information bits transmitted by antenna indices. In QSM, a complex data symbol is decomposed into its real and imaginary components; then, these two components are independently transmitted using the SM principle. A low-complexity, near-maximum likelihood (ML) error performance achieving detection scheme is proposed for QSM to reduce the overall computational complexity of the ML detector. First, the proposed detector determines the set of most probable active transmit antennas and the corresponding possible transmission patterns. Then, ML-based detection is used to determine the transmitted complex data vector by performing a search over these transmission patterns and M-ary constellation symbols. It has been shown via computer simulations that the proposed detection algorithm exhibits near-ML bit error rate performance with considerably lower decoding complexity.

Capacity Performance of Overhead Transmission Multiple-Input Multiple-Output Broadband over Power Lines Networks: The Insidious Effect of Noise and the Role of Noise Models

Extending the analysis already presented in [1], this paper considers broadband potential of overhead (OV) transmission multiple-input multiple-output (MIMO) broadband over power lines (BPL) networks when different noise conditions occur and different well-proven noise models are adopted. The contribution of this paper is two-fold. First, the broadband potential of a great number of indicative OV high-voltage (HV) BPL topologies and of MIMO transmission schemes is studied in terms of appropriate capacity metrics. The relevant numerical results reveal the significant dependence of ΜΙΜΟ capacity metrics on noise conditions. Second, various well-known BPL noise models from the literature are compared on the basis of their achieved OV HV MIMO BPL capacity. Through the careful study of the capacity results of noise models, it is demonstrated that spectrally flat additive white Gaussian noise (AWGN) may be comfortably assumed as an efficient noise model in transmission MIMO BPL networks. Also in MIMO BPL networks, the comparative capacity analysis of noise models shows small differences among them in the 3-88MHz frequency range. Citation ：Lazaropoulos, A. G. (2016). Capacity Performance of Overhead Transmission Multiple-Input Multiple-Output Broadband over Power Lines Networks: The Insidious Effect of Noise and the Role of Noise Models. Trends in Renewable Energy, 2(2), 61-82. DOI: 10.17737/tre.2016.2.2.0023

Soft‐output space‐time block coded spatial modulation

Space-time block coded spatial modulation (STBC-SM) is a recently proposed multiple-input–multiple-output transmission scheme, which combines spatial modulation (SM) and Alamouti's space-time block code (STBC) in such a manner so as to retain the primary advantages of SM and STBC, while avoiding their drawbacks, resulting in an improved system error performance. In this study, the authors propose a soft-output maximum-likelihood (ML) detector (SOMLD) and a soft-output low-complexity near-ML detector (SOLCD) for STBC-SM transmission. Monte-Carlo simulations demonstrate that the error performance of the proposed schemes are able to closely match that of the hard decision ML detector for uncoded channel conditions, while significant improvement in error performance is demonstrated for coded systems. Furthermore, compared with SOMLD, SOLCD imposes a significantly lower computational complexity, while achieving near-ML error performance.

Linear Precoder Design for Doubly Correlated Partially Coherent Fading MIMO Channels

We consider the single-user multiple-input multiple-output (MIMO) precoder design problem for the doubly spatially correlated partially coherent Rayleigh fading channels with discrete inputs. The objective is to design a linear precoder to adapt to the degradation caused by the imperfect channel estimation at the receiver and the transmit-receive antenna correlation. The system is partially coherent so that the MIMO channel coefficients are estimated at the receiver and its error covariance matrix is fed back to the transmitter. We utilized the cutoff rate (CR) expression, an alternative to the mutual information (MI), and propose to use it as a design criterion to design the linear precoders. A linear precoder is obtained by numerically maximizing the CR with respect to the precoder matrix with a given average power constraint. Furthermore, the precoder matrix is decomposed using singular value decomposition (SVD) into the input shaping matrix, power loading matrix, and beamforming matrix. The beamforming matrix is found to coincide with the eigenvectors of the transmit correlation matrix. The power loading and input shaping matrices are solved numerically using the difference of convex (d.c.) functions programming algorithm and optimization under the unitary constraint, respectively. A 2-block alternating optimization (AO) algorithm is proposed to solve the input shaping matrix and power loading matrix iteratively. Precoders are designed to be used in conjunction with two MIMO transmission schemes: the spatial multiplexing (SM) and space-time (ST) block transmission modes. The frame error rate (FER) and average MI are used as the performance metrics to validate the performance of the newly designed CR-precoders in comparison with the conventional no-precoding case and cutoff rate optimized partially coherent constellations (PCCs). Numerical examples show that the performance gains of the designed precoders are significant compared to the CR-PCCs and conventional codewords.

Radio frequency electromagnetic field compliance assessment of multi‐band and MIMO equipped radio base stations

In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances.

Multilevel modulated chaos MIMO transmission scheme with physical layer security

Ensuring security at the physical layer in wireless communications is important and effective because it can omit upper-layer secure protocols in ad hoc or multi-hop relay transmissions, or it can enhance security together with upper-layer protocols. To realize this system, we have proposed a chaos-based multiple-input multiple-output (MIMO) transmis- sion scheme that enables both physical-layer security and a channel coding effect in a MIMO multiplexing transmission. However, the transmission rate is equivalent to binary phase shift keying (BPSK), that is, one bit/symbol, and multilevel modulations are needed to achieve higher-capacity communication. Moreover, the channel coding gain is limited, which needs to be improved. Therefore, in this paper, we propose a two- and four-bit/symbol chaos-MIMO scheme, equivalent to quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) rate-efficiency, with an adaptive chaos processing scheme enhancing the channel coding gain. The improved performances of the proposed scheme are shown in the numerical results. In addition, we describe the concept of identification modulation using this chaos transmission.

Spatially Modulated Orthogonal Space-Time Block Codes with Non-Vanishing Determinants

This paper proposes a multiple-input multiple-output (MIMO) transmission scheme for M-ary modulations, called Spatially Modulated Orthogonal Space-Time Block Coding (SM-OSTBC), based on the concept of Spatial Constellation (SC) codewords introduced by Le at el. . In the proposed scheme, transmit codeword matrices are generated by multiplying SC matrices with codewords constructed from Orthogonal Space-time Block Codes (O-STBC). The maximum spectral efficiency of the proposed scheme is equal to (n_T-2+ log_2 M) bpcu, where n_T is the number of transmit antennas and M is the modulation order. The SC matrices provide a means of carrying information bits together with the O-STBC codewords and allow the SM-OSTBC scheme to achieve second-order transmit diversity by satisfying the non-vanishing determinant property. A systematic method to design the SC codewords for an even number of transmit antennas greater than 3 is presented. A single-stream maximum-likelihood (ML) decoder, which requires a low computational complexity thanks to the structure of the SM-OSTBC codewords and to the orthogonality of the O-STBCs, and a sphere decoder with further reduced signal processing complexity are developed. The bit error rate (BER) performance of the proposed scheme is studied by using both theoretical union bound analysis and computer simulations. Finally, simulation results are presented in order to compare BER performance, energy efficiency and decoding complexity of the proposed scheme with those of several existing MIMO transmission schemes.

TR-MIMO detection of a small target in a shallow water waveguide environment

A kind of multiple-input multiple-output (MIMO) sonar model is presented for enhancing detection of small targets in an underwater acoustic waveguide. A co-located vertical linear array is partitioned into several sub-arrays illuminating orthogonal waveforms at a target of interest. When the target is modeled as an extended target consisting of multiple scatterers, time reversal is utilized in the MIMO transmission scheme for capturing target diversity. The feasibility of time-reversal beams simultaneously esonifying the target’s scatterers is verified by the analysis of spatial–temporal focusing in simulations. The tank experimental results have further demonstrated the effectiveness of the TR-MIMO sonar model.

Generalised Pre-Coding Aided Spatial Modulation

A new Multiple Input Multiple Output (MIMO) transmission scheme termed as Generalised Pre-coding aided Spatial Modulation (GPSM) is proposed, where the key idea is that a particular subset of receive antennas is activated and the activation pattern itself conveys useful information. This is in contrast to the previously proposed Spatial Modulation (SM) schemes, which operated by activating a specific subset of transmit antennas. We provide both analytical and numerical results characterizing the GPSM scheme proposed for both conventional as well as for large-dimensional MIMO configurations subject to both realistic imperfect Channel State Information at the Transmitter (CSIT) and to the low-rank approximation invoked for large-dimensional MIMO configurations. We also design a so-called reinforcement matrix for attaining substantial performance improvements for our proposed GPSM scheme. Our investigations show that the GPSM scheme constitutes a flexible alternative to the state-of-the-art MIMO transmission schemes, especially because it is capable of achieving a high throughput. Moreover, the benefits of mapping information to the spatial domain rather than relying on conventional modulation has substantial benefits in the medium to high Signal to Noise Ratio (SNR) region. Quantitatively, GPSM is capable of supporting the same throughput as the conventional full-multiplexing gain based MIMO arrangements at an SNR gain of about 1dB at the same receiver complexity. Furthermore, the reinforcement matrix aided GPSM scheme attains a further 3-4dB performance improvement as compared to the conventional GPSM scheme.

무선 중계 시스템에서 선택적 MIMO 전송에 대한 아웃티지 성능 연구

In this paper, a selective multiple-input multiple-output(MIMO) transmission scheme is proposed in dual-hop MIMO relaying systems, in which orthogonal space-time block code(OSTBC) transmission and transmit antenna selection(TxAS) transmission are selectively used. Assuming independent Rayleigh fading channels, the outage probability is analyzed for a decode-and-forward(DF) relaying system using the selective MIMO transmission scheme. Also, through numerical investigation, the outage performance for the DF relaying system using the selective MIMO transmission scheme is compared with that for the conventional DF relaying system using OSTBC or TxAS. Moreover, from the performance comparison, it is shown that the proposed scheme can reduce the system overhead without outage performance degradation.

Feasible load modulation technique using multiple antenna systems

In the passive multiple-input multiple-output transmission scheme, load modulation is applied to the multi-antenna, and a number of signals can be transmitted in parallel. The tag is defined as the multi-antenna that has load impedance, and it can control the reflective wave by switching its load impedance independently. The termination impedance pattern of the tag antennas is determined such that its reflection coefficients are to be distant from each other in a complex number plane. This technique can achieve multi-level modulation and high-speed data transmission without using the transmitter at the tag antenna.

Generalized Framework for the Analysis of Linear MIMO Transmission Schemes in Decentralized Wireless Ad Hoc Networks

We develop a general framework for the analysis of a broad class of point-to-point linear multiple-input multiple-output (MIMO) transmission schemes in decentralized wireless ad hoc networks. New general closed-form expressions are derived for the outage probability, throughput and transmission capacity. For the throughput, we investigate the optimal number of data streams in various asymptotic regimes, which is shown to be dependent on different network parameters. For the transmission capacity, we prove that it scales linearly with the number of antennas, provided that the number of data streams also scales linearly with the number of antennas, in addition to meeting some mild technical conditions. We also characterize the optimal number of data streams for maximizing the transmission capacity. To make our discussion concrete, we apply our general framework to investigate three popular MIMO schemes, each requiring different levels of feedback. In particular, we consider eigenmode selection with MIMO singular value decomposition, multiple transmit antenna selection, and open-loop spatial multiplexing. Our analysis of these schemes reveals that significant performance gains are achieved by utilizing feedback under a range of network conditions.