Multiple-input Multiple-output Scheme Research Articles

Design and Implementation of the MIMO-COOK Scheme Using an Image Sensor for Long-Range Communication.

Radio-frequency technologies are widely applied in many fields such as mobile systems, healthcare systems, television and radio broadcasting, and satellite communications. However, one major problem in wireless communication based on radio frequencies is its impact on human health. High frequencies adversely impact human health more than low frequencies if the signal power transgresses the permissible threshold. Therefore, researchers are investigating the use of visible light waves (instead of the radio-frequency band) for data transmission in three major areas: visible light communication, light fidelity, and optical camera communication. In this paper, we propose a scheme that upgrades the camera on–off keying (COOK) scheme by using it with the multiple-input multiple-output (MIMO) scheme; COOK has been recommended by the IEEE 802.15.7-2018 standard. By applying technologies, such as matched filter, region of interest, and MIMO, our proposed scheme promises to improve the performance of the conventional scheme by improving the data rate, communication distance, and bit error rate. By controlling the exposure time, the focal length in a single camera and using channel coding, our proposed scheme can achieve the communication distance of up to 20 m, with a low error rate.

Layered Division Multiplexing With Co-Located Multiple-Input Multiple-Output Schemes

The most recent standard for broadcast services, Advanced Television System Committee—Third Generation (ATSC 3.0), has adopted co-located multi-antenna schemes and Layered Division Multiplexing (LDM) in order to increase the capacity and reliability compared to former Digital Terrestrial Television (DTT) systems. ATSC 3.0 has adopted both technologies separately, but no combination of them is planned yet. Compared to baseline LDM case, use of several antennas allows for diverse parametrization for each layer. This paper analyzes the potential combination of co-located Multiple-Input–Multiple-Output (MIMO) schemes with LDM. A trade-off analysis between complexity constraints and performance benefits is evaluated.

On the Design of RD-MIMO: Spatial Multiplexing Versus Opportunistic Transmission Schemes

In this work, we focus on the implementation of reconfigurable distributed multiple-input multiple-output (RD-MIMO) schemes in practical communication environment. Considering RD-MIMO schemes, we raise an original research question, i.e., under what scenario whether we should recruit-then-transmit to multiple mobile receivers simultaneously or just recruit-then-transmit to one best selected mobile receiver. To address this question, we design a spatial multiplexing RD-MIMO (SM-RD-MIMO) scheme and an opportunistic RD-MIMO (O-RD-MIMO) scheme for the scenario of multiuser communication and that of one single best user communication, respectively. Aiming at the practical implementation of the RD-MIMO schemes, we choose zero-forcing (ZF) and maximal ratio transmitting (MRT) as beamforming strategies for the SM-RD-MIMO scheme and the O-RD-MIMO scheme, respectively. To evaluate the performance of the proposed schemes, we formulate sum rate maximization problems and solve the formulated problems analytically under some specific network settings. Through analytical and numerical examples, we show that the SM-RD-MIMO scheme outperforms the O-RD-MIMO scheme at moderate and high transmit signal-to-noise ratio (SNR) regimes, and vice versa at low transmit SNR regime. In addition, via numerical results, we provide a new finding that the ZF precoding under dynamic transmit power threshold-based per transmitter power constraint (PTPC) gives the same performance as that of the ZF precoding under sum power constraint (SPC).

Performance Analysis of MIMO Wavelet Packet Multicarrier Multicode CDMA System with Antenna Selection

Performance of Multicarrier Multicode Code-Division Multiple Access (MC/MCD-CDMA) systems can be improved significantly by using Wavelet Packets (WPs) as subcarriers instead of a~sinusoidal function. This is because WPs have much lower sidelobes and negligible sidelobe energy leakage compared to sinusoidal carriers; this property significantly decreases the intercarrier interference and improves the system performance. Further improvement can be achieved by utilizing multiple antennas at transmitter and receiver to construct a~Multiple-Input Multiple-Output (MIMO) system. Channel hardening is the main drawback of MIMO systems. Antenna selection can be employed to reduce this problem. In this paper, we use the antenna selection in MIMO WP-MC/MCD-CDMA system. These combinations of antenna selection, MIMO, and WP in MC/MCD-CDMA improve the system performance significantly and reduce the channel hardening. The performance of the system is tested according to the outage probability and bit error rate. Two MIMO schemes on Nakagami-m fading channel are considered, which are: selective transmit /selective receive and selective transmit /maximum ratio combining receive. The study includes the effects antennas' number, fading parameter-m, number of users, and the threshold signal to interferences plus noise ratio. The performance of the system is compared to that of MC/MCD-CDMA based on a~sinusoidal carrier. The results reveal that: by increasing antennas' number, the system performance is improved significantly, and MC/MCD-CDMA system based on WPs carriers outperforms MC/MCD-CDMA system based on a~sinusoidal carrier.

Cooperative Time Successive SSK-M-ary Modulation for Decode-and-Forward Relay Systems

Space shift keying (SSK) is a single radio frequency (RF) chain multiple-input multiple-output (MIMO) scheme that uses the index of transmit antennas for information transmission. Time successive SSK- $ M$ -ary modulation (TSSM) and multi RF chain TSSM (MRF-TSSM) are recent MIMO techniques that achieve second order transmit diversity. We propose two cooperative relaying systems to attain distributed diversity in addition to transmit diversity of TSSM and MRF-TSSM. Cooperative-TSSM-1 (Coop-TSSM-1) uses multibranch relaying where TSSM is used in orthogonal time slots during the cooperative phase. Coop-TSSM-2 maps symbols to lower order constellations at multiple relays for simultaneous transmission of information using MRF-TSSM. We consider Decode-and-forward (DF) relaying where relays that correctly detect symbols forward it. We analyze the average number of relays that participate in cooperation, the end-to-end performance using a tight upper bound on the bit error rate (BER) and the asymptotic BER expressions to analyze diversity orders of both cooperative systems. We validate all analyzes using simulation results. From the analysis and results we show that Coop-TSSM-1 achieves better diversity order compared to Coop-TSSM-2 at the cost of higher number of time slots for completing the cooperative phase. Further in Coop-TSSM-2, results indicate that different constellation mappings used in MRF-TSSM during cooperative phase impact the BER performance. By applying spatial modulation based transmit diversity and $M$ -ary Modulation systems in the cooperative setups of Coop-TSSM schemes, performance comparison is given which highlights the significance of Coop-TSSM schemes.

Differential-Detection Aided Large-Scale Generalized Spatial Modulation is Capable of Operating in High-Mobility Millimeter-Wave Channels

A large-scale differential-detection aided generalized spatial modulation (GSM) system is proposed, which relies on a novel Gram–Schmidt basis set and an adaptive low-complexity detector, and is evidently suitable for high-mobility millimeter-wave (mmWave) channels. We consider nonstationary time-varying mmWave channels and assume that the beam-angles remain relatively fixed, while the channel coefficients vary rapidly. In this scenario, it is a challenging task to find the accurate estimates of channel coefficients for digital beamforming, which becomes an even more severe problem, as the numbers of subarrays and subcarriers increase. Our analog-beamforming-aided nonsquare differentially detected scheme achieves a higher transmission rate than the conventional coherent multiple-input multiple-output schemes because the pilot overhead and the complex-valued feedback are eliminated. Our simulation results following the IEEE 802.11ad specifications show that the performance of our proposed nonsquare differential GSM improved upon increasing the number of subarrays, where the maximum transmission rate of 16 b/s/Hz was considered.

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.

Investigation of error performance in network coded MIMO-VBLAST wireless communication systems

Abstract Paper aims to enhance the performance of bit error rate (BER) in wireless communication based on the multiple-input multiple-output (MIMO) system of vertical Bell laboratories layered space-time (VBLAST) algorithm. The VBLAST algorithm uses zero-forcing (ZF) and the minimum mean square error (MMSE) to evaluate the BER of wireless communication. MIMO VBLAST techniques function as an adaptive filter and can minimize the interference and multipath fading in the received signal of the channel. Physical layer network coding (PNC) is a new technique used to exploit the spatial diversity of the MIMO VBLAST system to improve the throughput and performance of wireless communication. The bit-error-rate (BER) of proposed VBLAST MIMO with PNC with binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulation over the additive white Gaussian noise and Rayleigh fading channel are analyzed. The performance of both BPSK and QPSK modulation in two and four antennas are compared. From the simulation results, it was found that the proposed scheme MIMO VBLAST PNC has a 45.2 % higher BER performance compared to the traditional MIMO scheme with an increase in the BER using MMSE and ZF respectively in both two and four antennas.

Interference Mitigation and Power Allocation Scheme for Downlink MIMO–NOMA HetNet

In this paper, a novel interference mitigation and power allocation (PA) scheme is investigated for downlink non-orthogonal multiple access (NOMA) with multiple input multiple output (MIMO) technology in heterogeneous networks (HetNets). The proposed scheme, named PA based interference alignment and coordinated beamforming (PA-IA-CB), consists of two stages. The first stage applies two steps of IA-CB; one step for canceling the inter-cluster and the co-tier interference among small cells, whereas the other step deals with the inter-cluster interference within the macro cell. In the second stage, the cross-tier interference is proposed to be managed by properly handling the allocated power to the macro base station (MBS) and the small base stations (SBSs). The PA problem is modeled as a non-cooperative game between the MBS and the SBS with the aim of increasing the system sum rate. Simulation results verify the efficiency of the proposed technique in terms of total system sum rate and outage probability compared to the conventional schemes.

Complexity analysis of FDE receivers for massive MIMO block transmission systems

This study considers massive multiple-input multiple-output (m-MIMO) schemes employing orthogonal frequency division multiplexing (OFDM) or single-carrier with frequency-domain equalisation (SC-FDE) modulation, concerning an uplink transmission. The authors study the performance and complexity for both conventional zero forcing (ZF) and minimum mean squared error (MMSE) (which require the inversion of channel matrix) and iterative frequency domain equalisation receivers based on equal gain combining (EGC) and maximum ratio combining (MRC) concepts, that do not require matrix inversions. It is shown that, although matrix inversions are generally the more complex operations for relatively balanced systems (i.e. with similar number of transmit and receive antennas), this is not generally true for systems where the channel matrix is `very tall' (i.e. much more receive than transmit antennas), at least in terms of the number of multiplications and sums. This means that the advantage on a reduced complexity of MRC/EGC-based equalisers with respect to ZF/MMSE is, in fact, limited. However, the performance advantages combined with the possibility of parallel receiver implementations, make those techniques particularly interesting for m-MIMO schemes, either employing OFDM or SC-FDE modulations.

Asymptotic capacity analysis under different adaptive transmission for TAS/MRC MIMO scheme subject to Weibull fading channels

This paper investigates a unified average channel capacity (ACC) analysis under different adaptive transmission of multiple-input multiple-output (MIMO) system, combining single transmit antenna selection (TAS) and maximal-ratio combining (MRC) receiver operating under independent flat Weibull multipath fading channels (WFCs). Based on a tight approximate probability density function expression of the signal-to-noise ratio (SNR) at the considered receiver output, we derive new accurate closed-form expressions of ACC for TAS/MRC system employing several rate adaptation techniques, namely optimal rate adaptation, optimal simultaneous power and rate adaptation, channel inversion with fixed rate (CIFR), truncated CIFR (TCIFR), and continuous power TCIFR (CTCIFR). Further, asymptotic expressions, in both high and low-SNR regimes, are investigated. The results show high accuracy for significant values of Lt×Lr TAS/MRC system. Indeed, the smaller Lt×Lr, the better the PDF’s accuracy, therefore, the better are the capacities. Numerical outcomes have been assessed by utilizing Mathematica and Matlab Software and corroborated via Monte-Carlo simulations.

Dynamic SSK-BPSK System Under Transmitter Correlated Nonidentical Rayleigh Fading

Space shift keying (SSK) is a recent multiple-input multiple-output (MIMO) modulation scheme where information is conveyed by the index of the activated antenna. An advantage of SSK transmitter is that it requires only one radio frequency (RF) chain. To achieve transmit diversity in such a single RF chain two antenna transmitter, modulation is dynamically changed between SSK and a modified form of binary phase shift keying (BPSK) based on channel condition in dynamic SSK-BPSK (DSB). DSB achieves second-order transmit diversity which is attributed to the statistical independence of sum and difference of independent and identically distributed complex Gaussian channel vectors. In order to study the impact of correlated and nonidentically distributed channel vectors on the transmit diversity of DSB, we consider transmitter correlated nonidentical Rayleigh fading in this work. We derive the bit error rate (BER) expression of DSB and the probability of using BPSK in DSB for the considered fading channel. Using asymptotic BER expressions, we study the diversity order of DSB. Results show that the transmit diversity of DSB is unaffected by the transmitter correlation when channel fading is identical, but nonidentical fading affects transmit diversity. Finally, we corroborate our analyses with simulation results.

Digital Upstream Crosstalk Cancellation for Future (T)WDM-PON Systems

We experimentally demonstrate a multiple-input multiple-output (MIMO) scheme for compensating upstream crosstalk in (T)WDM passive optical network (PON) systems in the electrical domain. The scheme relaxes the optical receiver filter isolation requirements by up to 9 dB, and thus enables narrower channel spacings. We show experimentally that in the case of no or low oversampling of 1 or 2 samples per symbol (Sps), the MIMO scheme can only be applied if all channels are fully symbol aligned, whereas by oversampling at 3 Sps or higher, operation is possible without symbol alignment.

Accurate Channel Estimation for Millimeter-Wave MIMO Systems

Channel estimation is of great challenge for millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems. The underlying reason can be attributed to two facts. One is the huge dimension of MIMO channel matrix, since mmWave systems typically employ large antenna arrays at both the transmitter and receiver to realize sufficient link margin. The other fact is the limited number of radio-frequency chains available for transmitter/receiver array, due to the power and cost limitations. This paper proposes a two-stage accurate channel estimation scheme for mmWave MIMO. Initially, we utilize sparse Bayesian learning to obtain a coarse channel estimate. Then we refine the channel estimate by iteratively maximizing the likelihood function of channel parameters. It is shown through simulations that the proposed scheme significantly outperforms the counterparts, and can achieve accurate channel estimation performance.

Downlink Signal-to-Interference Ratio and Spectral Efficiency of MIMO Cellular Networks Using Truncated Lognormal Approximation

This work focuses on analytical performance evaluation of a multiple-input multiple-output (MIMO) multicellular radio access network, while taking into account distance-dependent path loss, lognormal-distributed shadowing, and Rayleigh-distributed multipath fading. We propose a truncated moment-matching method for approximating the distribution of the sum of independent lognormal random variables in order to model the statistical behavior of the downlink signal-to-interference ratio (SIR) experienced by user equipment at a particular location in the presence of cochannel interference. The proposed method offers a good match with the simulated results in terms of the downlink SIR as well as mean and outage spectral efficiency for various MIMO schemes such as transmit and receive diversity, closed- and open-loop spatial diversity, and closed-loop multiuser MIMO. We compare the semianalytical results with that obtained from Monte Carlo simulations and quantify the relative error in terms of statistical metrics such as Kullback–Leibler divergence and Kolmogorov–Smirnov distance. In contrast to the existing works, the proposed model is useful for a wide range of shadowing standard deviation (4–12 dB) and activity of neighboring base stations (0.4–1). Moreover, the presented method is shown to achieve a comparable accuracy with the state of the art in spite of being less time consuming.

Group layer MU-MIMO for 5G wireless systems

Multiple-input multiple-output (MIMO) and nonorthogonal multiple access technologies are considered as fundamental components to meet the high spectral efficiency requirements of the forthcoming 5G wireless systems and beyond. In this context, group layer multiuser MIMO (GL-MU-MIMO) scheme has been proposed by the authors with linear group multiuser detection and receive antenna selection (RAS) to increase the number of simultaneously and reliably connected users more than the utilized number of radio frequency chains at the base station. In this paper, we derive the sum rate and capacity region expressions for GL-MU-MIMO uplink Rayleigh fading channels to demonstrate the impact of power allocation on the system performance and user-fairness. In addition, two low complexity RAS algorithms are proposed to maximize the sum rate of designed users’ groups and overall channel capacity. These techniques are utilized for new dynamic user grouping, RAS, and power allocation strategy to optimize the system performance under total received power and minimum user rate constrains. Compared with the generic MU-MIMO, numerical simulations demonstrate valuable tradeoffs between user overloading, complexity, and achieved performance through efficient utilization of groups’ power allocation. The new outcomes of GL-MU-MIMO extends the state-of-the-art towards diverse multi-antenna applications for future communications.

Design of MIMO-Visible Light Communication Transceiver Using Maximum Rank Distance Codes

This paper is aimed at comparing the performance of multiple-input multiple-output (MIMO) schemes applied to the indoor visible light communication (VLC) system. The MIMO schemes considered for this paper are repetition coding (RC), space-time block codes (STBCs), and spatial multiplexing (SMP). For MIMO design, the current system makes use of unique algebraic codes, i.e., maximum rank distance (MRD) codes in this connection. Two different configurations (2 × 1 and 2 × 2 ) are taken into consideration with distinct transmitters' spacing. Simulation results are presented and a comparative analysis of the current system with an existing system is given mainly in terms of bit error rate (BER), data-rate, and transmission range. The simulation results are validated by the physical implementation of the system using NI cDAQ module programmed in LabVIEW. The simulation and experimentation results indicate that the RC scheme with significant diversity gain provides more robustness as compared to other MIMO schemes; however, the RC exhibits poor multiplexing gain, and hence, it is not spectral efficient. As its counterpart, the STBC and SMP are used that can increase both the capacity and reliability at the cost of slightly reduced transmission range.

Joint Blind Identification of the Number of Transmit Antennas and MIMO Schemes Using Gerschgorin Radii and FNN

Blind enumeration of the number of transmit antennas and blind identification of multiple-input multiple-output (MIMO) schemes are two pivotal steps in MIMO signal identification for both military and commercial applications. Conventional approaches treat them as two independent problems, namely the source number enumeration and the presence detection of space-time redundancy, respectively. In this paper, we develop a joint blind identification algorithm to determine the number of transmit antennas and MIMO scheme simultaneously. By restructuring the received signals, we derive three subspace-rank features based on the signal subspace-rank to determine the number of transmit antennas and identify space-time redundancy. Then, a Gerschgorin radii-based method and a feed-forward neural network are employed to calculate these three features, and a minimal weighted norm-1 distance metric is utilized for decision making. In particular, our approach can identify additional MIMO schemes, which most previous works have not considered, and is compatible with both single-carrier and orthogonal frequency division multiplexing (OFDM) systems. Simulation results verify the viability of our proposed approach for single-carrier and OFDM systems and demonstrate its favorable identification performance for a short observation period with acceptable complexity.

Adaptive Modulation and Superposition Coding for MIMO Data Transmission Using Unequal Error Protection and Ordered Successive Interference Cancellation Techniques

This paper proposes and discusses an efficient multiple input multiple output (MIMO) system for adaptive modulation coding (AMC) based on unequal error protection (UEP) and superposition coding (SPC) by exploiting the features of sub channel partitioning. Using AMC, an appropriate order of modulation and code rate to suit the channel state information (CSI) can be selected. The realization of UEP is achieved through adaptive allocation and transmission of high and low-priority data signals over high and low quality sub channels respectively. A multistage decoding (MSD) receiver with the ordered successive interference cancellation (OSIC) technique is employed in the receiver by using two linear receiver signal combiner (RSC) techniques: zero-forcing (ZF) and minimum mean square error (MMSE). The data priority can be distinguished by the signal-to-noise ratio (SNR) and can be categorized as mode-B and mode-G. The simulation results show that the SNR performance enhancement for the UEP- MIMO scheme is approximately 9.4 dB compared to the others schemes. In addition, for the UEP-MIMO scheme, the overall data system transmission from mode-B outperforms that of mode-G with SNR gains of 8.2 dB compared to the 7.5 dB for the UEP-SISO scheme. Also, MMSE-SPC also outperforms the ZF-SPC with a 3 dB SNR at a bit error rate (BER) of 10-3.

A Novel Tensor CS-Based NOMA MIMO System for the Downlink of Massive Mission-Critical MTC in 5G and Beyond

The introduction of 5G and beyond systems brings new challenges for efficiently supporting the random access of a massive number of users with ultra-reliable low-latency requirements. To address these challenges, we propose a novel compressed sensing (CS)-based nonorthogonal multiple access (NOMA) multiple-input multiple-output (MIMO) scheme, called the CS-NOMA MIMO scheme, for the downlink of massive mission-critical machine-type communication (mmcMTC). By taking advantage of tensor CS techniques, a novel tensor CS-based packet (frame) structure, called TCS packet (frame), is proposed for the CS-NOMA MIMO scheme to further reduce the transmit time intervals (TTIs), resulting in smaller latency than that using the conventional packet (frame) structure. In the TCS packet (frame) structure, the CS signatures are assigned not only to different users but also to different time slots and different symbols of a time slot, thus achieving a user, time slot, and symbol overload system. We present a sufficient condition for the construction of the CS signatures that ensure effective deployment of tensor CS-based multiuser detection (CS-MUD) in user receivers. Furthermore, we consider the case of imperfect channel state information (CSI) and present an upper bound for the performance of the proposed scheme. Finally, the simulation results show that the proposed scheme can achieve high user overload (up to 5) and time slot overload (up to 3) when the activity ratio of users is 1%. When the time slot overload is 3, the proposed scheme with the TCS packet (frame) shortens time slots by at least 2/3 times that of the typical grant-based NOMA schemes. In addition, the block error rate (BLER) of the proposed scheme with the TCS packet (frame) is much lower than that with the conventional packet (frame), even less than 10−9 by repeat transmission when the time slot overload is 3.