Antenna Index Research Articles

MIMO Hybrid Satellite-Terrestrial Cooperative Systems With Spatial Modulation

With the advent of the space industry, hybrid satellite-terrestrial cooperative systems (HSTCSs) have drawn significant attention due to their prominent advantages. Besides, a novel modulation technique called spatial modulation (SM), which uses transmit antenna indices as additional information conveying source, is another technology envisioned to be used for next-generation communication systems. In this article, we propose to use SM in an HSTCS scheme consisting of a satellite, multiple terrestrial relays with multiple-input and multiple-output configuration, and a destination node equipped with multiple antennas on the ground. We derive a union bound for the symbol error probability in a fairly exact form and diversity order to shed light on the significant system parameters on the performance. Our theoretical results are validated through Monte Carlo simulations, and it is shown that using the SM technique provides a better error performance in the considered HSTCS system when compared to vertical Bell Laboratories layered space-time and space-time Alamouti codes.

Integrated Spatial Modulation and STBC-VBLAST Design toward Efficient MIMO Transmission.

In this contribution, the concept of spatial modulation (SM) is firstly integrated into the structure of space-time block codes (STBC)-aided vertical Bell-labs layered space-time (VBLAST) systems, in order to strike a balanced tradeoff among bit error ratio (BER), spectral efficiency and computational complexity. First of all, in order to enhance the BER performance of STBC-VBLAST, we advocate an effective transmit power allocation (TPA) scheme with negligible implementation costs, while dividing the STBC and VBLAST layers with alleviated interference, so as to facilitate combination with SM. Then, we further utilize the unique structure of SM for enhancing the spectral efficiency of original STBC-VBLAST, wherein the information is conveyed by not only the amplitude/phase modulation (APM) symbols but also the antenna indices. In addition, constellation sets of STBC symbols are specifically designed to be rotated to make full use of the degrees of freedom. Finally, the performance advantages of the above-mentioned structures over traditional STBC-VBLAST are demonstrated by the theoretical derivation of a closed-form expression for the union bound on the bit error probability for various spectral efficiencies, and they are supported by simulation results.

Extended Space Index Modulation

In this letter, a new scheme called extended space index modulation (ESIM) is proposed and investigated. Different from previous works, both the signal constellation and index domains are exploited, and the performance of the spectral efficiency and the reliability can be further enhanced. Specifically, in the ESIM, an antenna index (AI) vector set is designed to convey more extra index bits, which consists of two AI vector subsets. The two AI vector subsets, which are respectively used to modulate the quadrature amplitude modulation (QAM) and secondary QAM (S-QAM) symbols, include the AI vectors having two non-zero elements from <inline-formula> <tex-math notation="LaTeX">$\{(1,1),(1,j),(j,1),(j,j)\}$ </tex-math></inline-formula> to activate two transmit antennas and the AI vectors having only one non-zero element equaling to &#x201C;1&#x201D; to activate one transmit antenna. Furthermore, the S-QAM constellation is designed to enhance the squared Minimum Euclidean Distance. Simulation results are provided to show a close match with analytical results particularly in the high signal-to-noise ratio (SNR) region and demonstrate that significant performance gain can be achieved in the proposed ESIM.

Space–time line coded spatial modulation

In this letter, a novel multiple-input multiple-output transceiver technique, named space–time line coded spatial modulation (STLC-SM) is proposed, where two modulation symbols are transmitted through one of the multiple transmit antennas determined by the incoming information bits after constellation-rotated STLC encoding. The receiver decodes the transmitted modulation symbols and the activated antenna index through an optimal joint maximum-likelihood detector. As a main result, the closed-form upper-bound of bit-error-rate of the proposed STLC-SM system in general antenna configurations is mathematically analysed. Finally, it is validated that the STLC-SM significantly outperforms the conventional STLC in terms of the bit-error-rate.

Performance Analysis of an Index Modulation-Based Receive Diversity RIS-Assisted Wireless Communication System

In this letter, a system model for beyond 5G communication networks utilizing the potential of both index modulation and reconfigurable intelligent surface (RIS) based communication schemes is investigated. An analytical framework for the performance evaluation of the considered system which does not involve complicated phase distributions is developed. The performance of RIS-space-shift keying (RIS-SSK) and RIS-spatial modulation (RIS-SM) schemes using a greedy detector is analyzed, and novel closed-form expressions for the probability of erroneous receive antenna index detection are obtained. It is observed that for both RIS-SSK and RIS-SM, the derived performance metric: (a) decreases with increase in signal-to-noise ratio (SNR); (b) tends to saturate with increasing SNR as well as with decreasing SNR; and (c) decreases with increase in the number of RIS elements.

Design of Multi-band Compatible Trigeminal Monopole Array Antenna for Unmanned Aerial Vehicle

Compared with the performance index of UAV system antenna, a compatible trigeminal monopole array antenna is proposed. This antenna uses photosensitive resin as the substrate material, and can be made with UAV shell using 3D printing technology, realizing the integration of the antenna system and UAV. The antenna uses a trigeminal monopole antenna as the basic radiation unit, which is arranged in accordance with the Sierpinski fractal structure to form fractal radiation array. While enhancing the radiation through the array, it ensures that the antenna has a larger working bandwidth. In radiation performance test, the antenna is operating over a frequency spectrum of 1.038-11.916 GHz, and the minimum S11 is -37.92 dB. The proposed antenna has multi-band compatibility, better radiation performance, and greater performance redundancy.

Distributed Reed-Muller Coded-Cooperative Spatial Modulation

This paper proposes distributed Reed-Muller coded spatial modulation (DRMC-SM) scheme based on Kronecker product (KP) construction. This special construction enabled an effective distribution of classical Reed-Muller (RM) code along source and relay nodes. The proposed DRMC-SM scheme not only offers resilience in bit error rate (BER) performance but also enhances the spectral efficiency due to additional antenna index transmission inculcated by spatial modulation (SM). The usefulness of KP construction over classical Plotkin (CP) construction in coded-cooperation is analysed with and without incorporating SM. An efficient criteria for selecting the optimum bits is adopted at relay node which eventually results in better weight distribution of the mutually constructed (source and relay) RM code. The numerical results show that proposed KP construction outperforms CP construction by 1 dB in signal to noise ratio (SNR) at bit error rate (BER) of $$\,7\times 10^{-7}$$ . Moreover, the proposed DRMC-SM scheme outperforms its non-cooperative Reed-Muller coded spatial modulation scheme as well as distributed turbo coded spatial modulation scheme. This prominent gain in SNR is evident due to the path diversity, efficient selection of bits at the relay node and joint soft-in-soft-out (SISO) RM decoding employed at the destination node.

Spatial Index Modulation With the Combination of Both Antenna Indexes and Two Constellations

In this paper, in order to further exploit the antenna index (AI) domain for increasing the spectral efficiency, we propose a new schematic of enhanced generalized spatial modulation with both three dimension constellation and QAM constellation (EGSM-3DQ) to enhance the active AI combinations with the construction of three dimension (3D) signal constellation. In the EGSM-3DQ, a transmit vector symbol (TVS) consists of two spatial vector symbols (SVS) with the aid of one vector index bit, one SVS of which is obtained by modulating three components of a 3D signal symbol on two or three active transmit antennas (TAs) through the 3D Signal Mapper and AI Vector Modulator, another SVS of which is obtained by modulating one or multiple mapped QAM symbols on one or multiple active TAs through the AI Vector Selector. In addition, by jointing the AIes and multiple constellations such as the 3D and QAM, PAM constellations, grouping EGSM (gEGSM) is proposed to develop the group index combinations to increase extra index information. Finally, the comparisons of squared minimum Euclidean distances (MED) and the average bit error probability are provided. Simulation results show that the proposed schemes improve the bit error rate performance as compared with conventional systems.

Generalized Quadrature Index Modulation With Multi-Index and Dimension-Extended Constellation

In this paper, in pursuit of enhancing the spectral efficiency and reliability of transmission in multiple-input multiple-output (MIMO) communication system, a new design method, named as the generalization of quadrature index modulation (GQIM), is proposed. In GQIM system, the key and vector indications are exploited by the design of the transmitted spatial vector (TSV). Also, the transmit diversity gain by transmitting two versions produced by a three dimension (3D) symbol is achieved. More specifically, in our proposed GQIM system, an extended dimension signal constellation, so called extended 3D constellation (E3DC), is designed for the employment in the GQIM framework. Then, for achieving the transmit diversity gain, combing with the antenna indexes, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> -axis, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Y$ </tex-math></inline-formula> -axis, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z$ </tex-math></inline-formula> -axis components of two versions of the E3D symbol are constructed into four spatial vectors that are considered as candidates of the real/imaginary part of a complex TSV. Furthermore, two possible TSVs are obtained by using two adders and two key controllers with two states of 1 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$j$ </tex-math></inline-formula> . With the aid of the vector indication, one out of two possible TSVs is selected for transmission. Finally, the spectral efficiency and squared MED, the spatial index bits and computational complexity, the upper bound on the average bit error probability are analyzed. The analytical and simulation results demonstrate the correctness of GQIM and show that GQIM achieves a higher data rate and the reliability of transmission in comparison to the existing classic systems.

Branch-and-Bound Search and Machine Learning-Based Transmit Antenna Selection in MIMOME Channels

The studies on the conventional transmit antenna selection (TAS) in multiple-input, multiple-output, multiple-antenna eavesdropper (MIMOME) channel have been focused on determining the optimal number of transmit antennas or selecting the optimal transmit antenna indices. To maximize the secrecy capacity, we need to develop a novel TAS scheme to simultaneously determine the optimal number of transmit antennas and select the corresponding optimal transmit antenna indices. In this paper, we propose the iterative branch-and-bound search-based TAS (IB-TAS) scheme to determine the optimal transmit antenna set in MIMOME channel. To reduce the computational complexity caused by TAS, we also propose the machine learning-based TAS (ML-TAS) schemes utilizing neural network (NN), support vector machine (SVM), and naive-Bayes (NB). Through the simulation and numerical results, it is demonstrated that the IB-TAS scheme achieves the optimal secrecy capacity. In addition, through comparative analysis of the proposed ML-TAS schemes, it was shown that the NN-based TAS scheme minimizes the computational complexity while minimizing the loss of secrecy capacity compared to other ML-TAS schemes.

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.

Single-RF MIMO: From Spatial Modulation to Metasurface-Based Modulation

In multiple-input multiple-output (MIMO) systems, multiple radio frequency (RF) chains are usually required to simultaneously transmit multiple data streams. As a special MIMO technology, spatial modulation (SM) activates one transmit antenna by requiring one RF chain and exploits the index of the active antenna for information transfer at each time slot. Recently, reconfigurable metasurfaces have emerged as a promising technology that is able to reconfigure the wireless propagation environment by altering the amplitude and/or phase of the incident signal. In this article, we aim for the implementation of single-RF MIMO by shifting the focus from SM to metasurface-based modulation. Specifically, the principles of SM and metasurfaces are first presented. After reviewing the evolution of SM, we elaborate on the idea of metasurface-aided single-RF MIMO and discuss some implementations for it in line with notable variants of SM. A comparison between antenna-based and meta-surface-based modulation is made to highlight the advantages of using metasurfaces. We finally investigate the research challenges and opportunities in the context of metasurface-based modulation.

Sum Rate Analysis of Generalized Space Shift Keying-Aided MIMO-NOMA Systems

We investigate the sum rate performance of a generalized space shift keying (GSSK)-aided, non-orthogonal multiple access (NOMA) network. In particular, we consider a multiple-input multiple-output (MIMO) NOMA downlink channel, where the base station employs GSSK modulation to transmit additional information to the NOMA users. We present a novel energy-based maximum likelihood (ML) detection strategy at the NOMA users to decode the active antenna indices. We derive a closed-form expression for the average pairwise error probability of the energy-based ML strategy to find a union bound on the bit error probability. Further, we derive the expression for the overall sum rate of the proposed GSSK-aided MIMO-NOMA system. Through numerical evaluations, we show that the proposed system outperforms the conventional MIMO-NOMA system, in terms of spectral efficiency.

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.

Secrecy Analysis of SSK Modulation: Adaptive Antenna Mapping and Performance Results

In this paper, we investigate the physical layer security based on space shift keying (SSK) in which bit-to-spatial mapping of antenna indices dynamically adapts according to the partial channel state information (CSI) of the legitimate channel at the transmitter (Tx). Further, the Tx also adapts transmit power allocation to each transmit antenna according to partial CSI. Since an eavesdropper (Eve) is not (usually) aware of the legitimate CSI, it cannot successfully decode the antenna index; thus, transmission over the legitimate channel is secured from the wiretapping of Eve. An important virtue of the proposed scheme is that the Tx does not require full CSI of the legitimate and eavesdropper channels to secure the confidential information. The proposed work focuses on the secrecy rate (SR) and bit error rate (BER) of the considered multiple-input single-output system over Rayleigh fading channels. Approximate expressions of Bob's data rate for 2-ary and 4-ary SSK modulations are derived in closed-form. Furthermore, an upper-bound of Bob's data rate for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> -ary SSK modulation is also derived. In order to obtain the secrecy rate for the proposed scheme, we also evaluate Eve's data rate. Analytical results of SR and BER demonstrate the robustness of the proposed scheme. All numerical results are thoroughly verified by using extensive Monte Carlo simulations.

Soft-Input Soft-Output Detection via Expectation Propagation for Massive Spatial Modulation MIMO Systems

In this letter, we propose to utilize the expectation propagation (EP) framework for soft-input soft-output (SISO) signal detection in massive spatial modulation (SM) multiple-input multiple-output (MIMO) systems. By using a multivariate complex Gaussian approximation approach, the symbol beliefs of the transmitted symbol vectors are constructed based on the propagation of the mean vectors and covariance matrixes. The log-likelihood ratios (LLRs) of the antenna index bits and the modulation index bits are computed by partitioning the symbol beliefs into different regions. Simulation results illustrate that the proposed SISO EP detector outperforms the state-of-the-art soft-decision algorithms and strikes a desirable performance-complexity tradeoff.

Multidimensional Index Modulation for 5G and Beyond Wireless Networks

Index modulation (IM) provides a novel way for the transmission of additional data bits via the indices of the available transmit entities compared with classical communication schemes. This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency-division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of 1-D IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely, enhanced mobile broadband (eMBB), massive machine-type communications (mMTCs), and ultrareliable low-latency communication (URLLC). In addition, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks.

Device-to-Device Aided Cooperative Relaying Scheme Exploiting Spatial Modulation: An Interference Free Strategy.

In this paper, a novel interference free dual-hop device-to-device (D2D) aided cooperative relaying strategy (CRS) based on spatial modulation (SM) (termed D2D-CRS-SM) is proposed. In D2D-CRS-SM, two cellular users (e.g., a near user (NU) and a relay-aided far user (FU)) and a pair of D2D transmitter (D)-receivers (D) are served in two time-slots. Two different scenarios are investigated considering information reception criteria at the NU. Irrespective of the scenarios, the base station (BS) exploits SM to map information bits into two sets: modulation bits and antenna index, in phase-1. In the first scenario, the BS maps FU information as the modulation bits and NU information as antenna index, whereas modulation bits correspond to NU information and the antenna index carries FU’s information in scenario-2. The iterative-maximum ratio combining (i-MRC) technique is then used by NU and D to de-map their desired information bits. During phase-2, D also exploits SM to forward FU’s information received from BS and its own information bits to the D2D receiver D. Then, FU and D retrieve their desired information by using i-MRC. Due to exploiting SM in both phases, interference free information reception is possible at each receiving node without allocating any fixed transmit power. The performance of D2D-CRS-SM is studied in terms of bit-error rate and spectral efficiency considering M-ary phase shift keying and quadrature amplitude modulation. Finally, the efficiency of D2D-CRS-SM is demonstrated via the Monte Carlo simulation.

Low complexity detector for amplitude phase shift keying‐based differential spatial modulation

Differential spatial modulation (DSM) involves the transmission of information through a combination of phase-modulated symbols and transmit antenna index. For efficient use of the wireless system resources, the amplitude information is also utilised as a part of the transmitted data in amplitude-phase shift keying-DSM (APSK-DSM). Here some of the information bits get encoded as differential amplitude in each of the transmit antennas, whenever they are activated resulting in better bandwidth efficiency than conventional DSM. However, prevailing detectors for APSK-DSM have high computational complexity. In this work, the authors proposed a low complexity detector for APSK-based DSM schemes using compressive sensing and an ℓ 2 -norm minimisation for detecting the differential amplitude. To decode this amplitude information, the authors have formulated a column by column decomposition of the received symbol in terms of the amplitude- and phase-modulated symbols received from each transmit antenna. The error performance of the proposed detector is nearly identical to that of existing APSK-based DSM receivers, which use maximum-likelihood detection but with much lower computational complexity than the latter.

Precoding and Transmit Antenna Subarray Selection for Secure Hybrid Spatial Modulation

Spatial modulation (SM) is a particularly important form of multiple-input multiple-output (MIMO), which uses both modulation symbols and antenna indices to carry information. In this paper, to avoid the high cost and circuit complexity of SM, we consider the hybrid SM system with a hybrid precoding transmitter architecture, combining a digital precoder and an analog precoder. In such a system, we carried out secure hybrid precoding and transmit antenna subarray selection (TASS) methods. Two hybrid precoding methods, called maximizing approximate secrecy rate (SR) via gradient ascent (Max-ASR-GA) and maximizing approximate SR via alternating direction method of multipliers (Max-ASR-ADMM), are proposed to improve the SR performance. As for TASS, a high-performance method of maximizing the approximate SR (Max-ASR) is first presented. To reduce its high complexity, two low-complexity TASS methods, namely maximizing eigenvalue (Max-EV) and maximizing product of signal-to-interference-plus-noise ratio and artificial noise-to-signal-plus-noise ratio (Max-P-SINR-ANSNR), are proposed. Simulation results demonstrate that the proposed Max-ASR-GA and Max-ASR-ADMM hybrid precoders harvest substantial SR performance gains over existing method. For TASS, the proposed three methods Max-ASR, Max-EV, and Max-P-SINR-ANSNR perform better than existing leakage method. Particularly, the proposed Max-EV and Max-P-SINR-ANSNR are of low-complexity at the expense of a little performance loss compared with Max-ASR.