Multi-input Multi-output Communication Systems Research Articles

AWOA: An Advanced Whale Optimization Algorithm for Signal Detection in Underwater Magnetic Induction Multi-Input–Multi-Output Systems

With the increasing exploitation and use of marine resources, the limitations of acoustic, optical, and radio frequency technologies for underwater communications have become increasingly apparent. Magnetic induction (MI) is a new communication technology that enables wireless data transmission via magnetic field coupling between transmitting and receiving coils. MI offers advantages such as channel stability, small antenna size, and no multi-path loss. Multi-input–multi-output (MIMO) is a multi-antenna technology that significantly increases system capacity and spectrum utilization without increasing bandwidth. The whale optimization algorithm (WOA) is a well-known bio-inspired algorithm that mimics the hunting behavior of whales to optimize swarm intelligence. This paper proposes a model for an underwater MIMO communication system based on magnetic induction. We then construct a signal detection algorithm for MI-MIMO systems using the advanced whale optimization algorithm (AWOA) and conduct simulation experiments to compare the performance and complexity of three standard signal detection algorithms: zero-forcing (ZF), minimum mean square error (MMSE), and maximum likelihood (ML). The experimental results show that AWOA achieves suboptimal results, as its bit error rate (BER) is close to that of the ML algorithm. Furthermore, the complexity of AWOA is comparable to that of the MMSE strategy. This work supports the development of a high-performance MI-based underwater communication system.

Interference Cancellation Based Spectrum Sharing for Massive MIMO Communication Systems.

Cellular network operators are predicting an increase in space of more than 200 percent to carry the move and tremendous increase of total users in data traffic. The growing of investments in infrastructure such as a large number of small cells, particularly the technologies such as LTE-Advanced and 6G Technology, can assist in mitigating this challenge moderately. In this paper, we suggest a projection study in spectrum sharing of radar multi-input and multi-output, and mobile LTE multi-input multi-output communication systems near m base stations (BS). The radar multi-input multi-output and mobile LTE communication systems split different interference channels. The new approach based on radar projection signal detection has been proposed for free interference disturbance channel with radar multi-input multi-output and mobile LTE multi-input multi-output by using a new proposed interference cancellation algorithm. We chose the channel of interference with the best free channel, and the detected signal of radar was projected to null space. The goal is to remove all interferences from the radar multi-input multi-output and to cancel any disturbance sources from a chosen mobile Communication Base Station. The experimental results showed that the new approach performs very well and can optimize Spectrum Access.

Achievable Capacity of Multipolarization MIMO With the Practical Polarization-Agile Antennas

In recent years, the polarization domain has attracted significant attention for the 4th and 5th generation (4G/5G) wireless communications owing to its benefit in channel capacity, symbol/bit error rate, and energy efficiency. One driving technology to fully utilize the polarization domain is the polarization-agile antennas that allow flexible reconfiguration of the transmitter (Tx) and receiver (Rx) polarization. The current state-of-the-art polarization-agile antennas can take several discrete polarization angles. This article proposes and analyzed a practical scheme to determine feasible optimal Tx and Rx polarization among the limited number of polarization angles to converge to theoretical channel capacity supported by the discrete polarization-agile antennas with single-RF front-end systems. Both the theoretical and simulation-based analyses for the capacity outage caused by adopting practical discrete polarization-agile antennas are provided in this article to complement communication system design in balancing channel capacity maximization and hardware cost. Comprehensive simulation results demonstrate that the multipolarization multi-input multi-output communication system toward the late revisions of 5G and beyond-5G, so called, 6G wireless communications can successfully reach the theoretically achievable channel capacity with the practical discrete polarization-agile antennas.

Two‐port ring‐shaped dielectric resonator‐based diversity radiator with dual‐band and dual‐polarized features

AbstractIn this article, a two‐port dielectric resonator (DR)‐based multi‐input multi‐output (MIMO) antenna is designed and examined. Some of the vital characteristics of designed antenna are: (a) modified plus shaped aperture fed ring DRA provides dual frequency bands, which can able to make proposed radiator useful for wireless LAN (2.4 GHz) and WiMAX frequency bands (3.3 GHz); (b) conversion of cylindrical to ring shaped DRA enhance the impedance bandwidth of both the operating band; (c) defected ground structure as well as using the idea of changing polarization at two different ports improves the isolation more than 20 dB in the working frequency range. For confirming the computer‐generated results, prototype of proposed two‐port radiator is fabricated. After observing the measured outcomes, it can be confirmed that the proposed antenna works over dual frequency ranges, that is, 2.3‐2.9 GHz/3.4‐4.0 GHz and it also creates CP waves in between 3.45 and 3.8 GHz. Far field and diversity parameters confirm that the designed radiator can be used in MIMO communication system.

Perfect isolation performance among two-element MIMO antennas

A rectangular microstrip patch (RMSP) antenna is designed to be used in a two-element Multi-Input Multi-Output (MIMO) antennas at which they operate at 5.8 GHz. The two antennas are positioned opposite to each other with a separation of 10 mm (0.2 λ0) from their radiating edges. A novel uni-conductor electromagnetic bandgap (UC-EBG) periodic cells are introduced in this paper as effective barriers for surface waves compared to the conventional UC-EBG. Each unit cell has a compact size area 7.3 × 5.8 mm2 where it is 20% more compact than the conventional cell. Two of the proposed modified EBG periodic cells are placed in-between the two antennas causing an excellent reduction in the coupled power of 46 dB. This strong isolation definitely enhances the performance of antennas in MIMO communication systems, where 0.0001 and 0.03 values for correlation coefficient have obtained from S-parameters and far-field information, respectively, due to this strong isolation.

Successive Localization and Beamforming in 5G mmWave MIMO Communication Systems

Beamforming is an attractive technique to improve the system performance for multi-input multi-output (MIMO) communications. Previous works mainly focus on improving the data transmission quality. However, the potential of beamforming for improving the localization quality is not yet fully studied. In this paper, we focus on active beamforming to reduce the user equipment (UE) localization error for millimeter-wave MIMO systems. Such beamforming for localization is of challenge because its optimization cost function (e.g., the localization error bound) also depends on the actual UE location and instantaneous channel states, which are unknown in advance. To address this challenge, a novel successive localization and beamforming (SLAB) scheme is proposed, where the long-term UE location and the instantaneous channel state will be jointly estimated and then the beamforming vector will be successively optimized as per the obtained estimation results. The proposed SLAB scheme will yield a sequence of beamforming weights and UE location estimates, which will converge to the stationary point of the associated optimization problem. Simulation results show that the proposed SLAB scheme achieves a huge performance gain for UE localization compared with state-of-the-art baselines.

Non-orthogonal multi-carrier MIMO communication system using M-ary efficient modulation

In this paper, a wireless communication problem in Rayleigh fading channel is considered. A novel M-ary multi-carrier communication system is proposed to improve the communication performance, where both efficient modulation method and multi-input multi-output (MIMO) technique are combined. By using the time-hopping M-ary phase position shift keying (TH-MPPSK) in the multi-carrier MIMO system, we proposed two corresponding demodulation methods, including the one-by-one detection (OBD) and the improved OBD (IOBD), with low computational complexity. Additionally, we also propose a channel equalization method for the multi-carrier MIMO system. Simulation results demonstrate the effectiveness of the proposed efficient modulation and demodulation methods for MIMO systems with non-orthogonal multi-carrier signals.

16-QAM OFDM-Based K-Band LoS MIMO Communication System with Alignment Mismatch Compensation

This paper presents a novel K-band (18 GHz) 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM)-based 2 × 2 line-of-sight multi-input multi-output communication system. The system can deliver 356 Mbps on a 56 MHz channel. Alignment mismatches, such as amplitude and/or phase mismatches, between the transmitter and receiver antennas were examined through hardware experiments. Hardware experimental results revealed that amplitude mismatch is related to antenna size, antenna beam width, and link distance. The proposed system employs an alignment mismatch compensation method. The open-loop architecture of the proposed compensation method is simple and enables facile construction of communication systems. In a digital modem, 16-QAM OFDM with a 512-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs is used. Experimental results show that a bit error rate of 10−5 is achieved at a signal-to-noise ratio of approximately 18.0 dB.

Optimal Design Method of MIMO Antenna Directivities and Corresponding Current Distributions by Using Spherical Mode Expansion

This paper proposes a new methodology to design optimal antennas for MIMO (Multi-Input Multi-Output) communication systems by using spherical mode expansion. Given spatial channel properties of a MIMO channel, such as the angular profile at both sides, the optimal MIMO antennas should provide the largest channel capacity with a constraint of the limited implementation space (volume). In designing a conventional MIMO antenna, first the antenna structure (current distribution) is determined, second antenna directivity is calculated based on the current distribution, and thirdly MIMO channel capacity is calculated by using given angular profiles and obtained antenna directivity. This process is repeated by adjusting the antenna structure until the performance satisfies a predefined threshold. To the contrary, this paper solves the optimization problem analytically and finally gives near optimal antenna structure (current distribution) without any greedy search. In the proposed process, first the optimal directivity of MIMO antennas is derived by applying spherical mode expansion to the angular profiles, and second a far-near field conversion is applied on the derived optimal directivity to achieve near optimal current distributions on a limited surface. The effectiveness of the proposed design methodology is validated via numerical calculation of MIMO channel capacity as in the conventional design method while giving near optimal current distribution with constraint of an antenna structure derived from proposed methodology.

An enhanced multi-channel bacterial foraging optimization algorithm for MIMO communication system

ABSTRACTChannel estimation and optimisation are the main challenging tasks in Multi Input Multi Output (MIMO) wireless communication systems. In this work, a Multi-Channel Bacterial Foraging Optimization Algorithm approach is proposed for the selection of antenna in a transmission area. The main advantage of this method is, it reduces the loss of bandwidth during data transmission effectively. Here, we considered the channel estimation and optimisation for improving the transmission speed and reducing the unused bandwidth. Initially, the message is given to the input of the communication system. Then, the symbol mapping process is performed for converting the message into signals. It will be encoded based on the space–time encoding technique. Here, the single signal is divided into multiple signals and it will be given to the input of space–time precoder. Hence, the multiplexing is applied to transmission channel estimation. In this paper, the Rayleigh channel is selected based on the bandwidth range. This is the Gaussian distribution type channel. Then, the demultiplexing is applied on the obtained signal that is the reverse function of multiplexing, which splits the combined signal arriving from a medium into the original information signal. Furthermore, the long-term evolution technique is used for scheduling the time to channels during transmission. Here, the hidden Markov model technique is employed to predict the status information of the channel. Finally, the signals are decoded and the reconstructed signal is obtained after performing the scheduling process. The experimental results evaluate the performance of the proposed MIMO communication system in terms of bit error rate, mean squared error, average throughput, outage capacity and signal to interference noise ratio.

Blind channel equalization algorithm based on dual unscented Kalman filter for chaotic multi-input multi-output communication systems

To reduce channel noise, fading, and inter-user interference effectively in the chaotic communication systems with multi-user, a blind channel equalization algorithm based on dual unscented Kalman filter algorithm is proposed. Assuming that the coefficients of a multi-input multi-output (MIMO) channel can be described by an autoregressive model, two separate state-space representations are used for the signals and coefficients. Then two unscented Kalman filters are used to estimate chaotic signals and channel coefficients simultaneously. The simulation results indicate that the algorithm can effectively track the coefficients of the multi-path fading channel in chaotic MIMO communication systems at a fast convergence speed.

Polarization Control of Vertical-Cavity Surface-Emitting Lasers by Utilizing Surface Plasmon Resonance

We demonstrate polarization control of vertical-cavity surface-emitting lasers (VCSELs) to any desired directions by utilizing surface plasmon resonance at a metal nanohole array. A silver nanohole array is integrated on the p-type distributed Bragg reflector of an 850-nm AlGaAs-GaAs-based VCSEL. The metal nanohole array placed at rectangular lattices with orthogonally different two periods, one of which meets the resonaint condition, exhibits strong polarization preference in optical transmission. Integrated four VCSELs with different directions of the rectangular arrays of nanoholes demonstrate successful control of the polarization angles. The VCSELs are closely located onto a one chip so that the optical outputs are easily coupled to one optical fiber. The presented VCSEL array will open a new horizon of multi-input multi-output communication systems by using polarization multiplexing.

Statistical mechanical analysis of the linear vector channel in digital communication

A statistical mechanical framework to analyze linear vector channel models in digital wireless communication is proposed for a large system. The framework is a generalization of that proposed for code-division multiple-access systems in Takeda et al (2006 Europhys. Lett. 76 1193) and enables the analysis of the system in which the elements of the channel transfer matrix are statistically correlated with each other. The significance of the proposed scheme is demonstrated by assessing the performance of an existing model of multi-input multi-output communication systems.