MIMO communication

Non-orthogonal multiple access (NOMA) scheme has gained remarkable consideration from researchers as it is a favorable technique for the future release of 5G and beyond. Recently proposed beamspace MIMO NOMA for mmWave communication has shown further improvement in its spectrum efficiency by employing beamforming with the aid of instantaneous channel state estimation. But, practically the downlink and the uplink channel state information (CSI) are not identical as the channel reciprocity is no more valid in the fast-varying environment of mmWave communication. Thus, this increases the transmission overhead due to pilot transmission in both uplink and downlink communication. To overcome this issue, we propose a semi-blind technique to design beamforming in downlink power-domain NOMA for mmWave communication which only requires statistical CSI. In the first step, the sum outage probability is derived by using the exact characterization of ratio of the indefinite quadratic form (IQF). In the second step, a heuristic approach with the aid of the interior point (IP) algorithm is developed to find the optimal solution for beam vectors by minimizing the derived sum outage probability. Moreover, a closed-form statistical beamforming solution is derived which is established on statistical signal-to-leakage-noise-ratio (SLNR) maximization. These two proposed methods are compared with the classical principle eigenvector-based solution. Monte Carlo simulations are used to validate the derived analytical expression of outage probability. The results of optimization demonstrate that the performance of both proposed beamforming is higher than the classical eigenvector-based solution. However, the heuristic-based beamforming algorithm via interiorpoint optimization is significantly better than the SLNR-based solution.

Nonorthogonal multiple access (NOMA) communication presents a promising solution to the limitations of traditional orthogonal multiple access techniques, offering potential improvements in achievable rates. Multiple-input multiple-output (MIMO), when combined with NOMA (MIMO-NOMA), further enhances these benefits by leveraging the diversity advantages of multiple antennas. Looking ahead, the future of wireless communication hinges on deploying heterogeneous networks (HetNets), facilitating the coexistence of various wireless access networks in a hierarchical fashion. However, the advent of 5G and 6G communications brings shorter channel coherence times, rendering channel reciprocity unreliable. Consequently, conventional channel estimation methods relying on uplink (UL) pilots for downlink (DL) transmission become ineffective. To address this issue, we introduce a unique statistical beamforming technique that eliminates the necessity for channel reciprocity in channel estimation. This new technology eliminates the overhead associated with pilot broadcasts, increasing spectral efficiency. In our work, we have used the characterization of the indefinite quadratic form ratio to get the outage probability in closed form for the MIMO-NOMA network for 5G and beyond. Later on, a genetic algorithm (GA) was employed for the optimization of beamforming weights. Delivering a spectral efficient beamforming solution, providing an exact analytical characterization of outage probability, and an optimization framework based on GA to resolve constrained multiobjective optimization tasks are the key advantages of our proposed method. The simulation result validates the theoretical analysis and shows the supremacy of the proposed method over the classical statistical method.

The stacked intelligent metasurface (SIM), comprising multiple layers of reconfigurable transmissive metasurfaces, is a promising solution for future wireless communication systems. In this paper, we explore the integration of SIM in a multi-antenna base station for application to downlink multi-user communications. Also, a realistic power consumption model for SIM-assisted systems is presented. Specifically, we focus on maximizing the energy efficiency (EE) for hybrid precoding design, i.e., the base station digital precoding and SIM wave-based beamforming. Due to the non-convexity and high complexity of the formulated problem, we employ the quadratic transformation method to reformulate the optimization problem and propose an alternating optimization (AO)-based joint precoding framework. Specifically, a successive convex approximation (SCA) algorithm is adopted for the base station precoding design. For SIM wave-based beamforming, two algorithms are employed: the high-performance semidefinite programming (SDP) method and the low-complexity projected gradient ascent (PGA) algorithm. In particular, the results indicate that, while the optimal number of SIM layers for maximizing the EE and spectral efficiency differs, a design of 2 to 5 layers can achieve satisfactory performance for both. Finally, numerical results are illustrated to evaluate the effectiveness of the proposed hybrid precoding framework and to showcase the performance enhancement achieved by the proposed algorithm in comparison to benchmark schemes.

Cell-free (CF) massive multiple-input multiple-output (mMIMO) systems are emerging as promising alternatives to cellular networks, especially in ultra-dense environments. However, further capacity enhancement requires the deployment of more access points (APs), which will lead to high costs and high energy consumption. To address this issue, in this paper, we explore the integration of low-power, low-cost stacked intelligent metasurfaces (SIM) into CF mMIMO systems to enhance AP capabilities. The key point is that SIM performs precoding-related matrix operations in the wave domain. As a consequence, each AP antenna only needs to transmit data streams for a single user equipment (UE), eliminating the need for complex baseband digital precoding. Then, we formulate the problem of joint AP-UE association and precoding at APs and SIMs to maximize the system sum rate. Due to the non-convexity and high complexity of the formulated problem, we propose a two-stage signal processing framework to solve it. In particular, in the first stage, we propose an AP antenna greedy association (AGA) algorithm to minimize UE interference. In the second stage, we introduce an alternating optimization (AO)-based algorithm that separates the joint power and wave-based precoding optimization problem into two distinct sub-problems: the complex quadratic transform method is used for AP antenna power control, and the projection gradient ascent (PGA) algorithm is employed to find suboptimal solutions for the SIM wave-based precoding. Finally, the numerical results validate the effectiveness of the proposed framework and assess the performance enhancement achieved by the algorithm in comparison to various benchmark schemes. The results show that, with the same number of SIM meta-atoms, the proposed algorithm improves the sum rate by approximately 275% compared to the benchmark scheme.

A novel quasi-MLD solution denoted Directional Lattice Descent (DLD in short) is proposed in this paper to the MIMO and ISI detection problems, which exhibits quadratic time complexity. We formulate the detection problem as that of finding the closest point in a lattice. This is solved by a proposed discrete space analogy to the continuous-space gradient descent method: an initial lattice point is selected and subsequent lattice points are iteratively calculated so that each resides at a smaller distance from the received point than its predecessor, till a termination point. The problem and its solution are formulated within a broader general framework. Implementation aspects and comparative simulation results are presented.

Stacked intelligent metasurface (SIM) extends the concept of single-layer reconfigurable holographic surfaces (RHS) by incorporating a multi-layered structure, thereby providing enhanced control over electromagnetic wave propagation and improved signal processing capabilities. This study investigates the potential of SIM in enhancing the rate fairness in multiuser downlink systems by addressing two key optimization problems: maximizing the minimum rate (MR) and maximizing the geometric mean of rates (GMR). The former strives to enhance the minimum user rate, thereby ensuring fairness among users, while the latter relaxes fairness requirements to strike a better trade-off between user fairness and system sum-rate (SR). For the MR maximization, we adopt a consensus alternating direction method of multipliers (ADMM)-based approach, which decomposes the approximated problem into sub-problems with closed-form solutions. For GMR maximization, we develop an alternating optimization (AO)-based algorithm that also yields closed-form solutions and can be seamlessly adapted for SR maximization. Numerical results validate the effectiveness and convergence of the proposed algorithms. Comparative evaluations show that MR maximization ensures near-perfect fairness, while GMR maximization balances fairness and system SR. Furthermore, the two proposed algorithms respectively outperform existing related works in terms of MR and SR performance. Lastly, SIM with lower power consumption achieves performance comparable to that of multi-antenna digital beamforming.

In wireless distributed networks, cooperative relay and cooperative Multi-Input Multi-Output (MIMO) techniques can be used to exploit the spatial and temporal diversity gain in order to increase the performance or reduce the transmission energy consumption. The energy efficiency of cooperative MIMO and relay techniques is then very useful for the Infrastructure to Vehicle (I2V) and Infrastructure to Infrastructure (I2I) communications in Intelligent Transport Systems (ITS) networks where the energy consumption of wireless nodes embedded on road infrastructure is constrained. In this paper, applications of cooperation between nodes to ITS networks are proposed and the performance and the energy consumption of cooperative relay and cooperative MIMO are investigated in comparison with the traditional multi-hop technique. The comparison between these cooperative techniques helps us to choose the optimal cooperative strategy in terms of energy consumption for energy constrained road infrastructure networks in ITS applications.

Maximum PowerPoint (MPP) is a point in V-P characteristics where entire PV system can work with maximum efficiency and deliver maximum output .The factors affecting the efficiency of the solar systems are changes in irradiance ,shading ,temperature etc,. Though the MPP is varying continuously, there should be some algorithms to track the MPP changes and make sure the device work with maximum efficiency. The two famous algorithms, Perturb and Observe method and incremental conductance, has its own drawbacks at certain suddenly varying situations. In this project our aim is to develop and implement a new adaptive algorithm to track the Maximum PowerPoint at its varying conditions .Here we are using variable step size adaptive LMS algorithm .The advantages of this method are higher efficiency, better stabilized output, faster and true MPP tracking and long life of battery. The main application of this project is it can be used in solar charge controller and also this method can be exte...

Massive MIMO (Multiple Input Multiple Output) systems impose significant processing burdens along with strict latency requirements. The combination of large-scale antenna arrays and wide bandwidth requirements for next-generation wireless systems creates an exponential increase in frontend to backend data. Balancing the processing latency and reliability is critical for baseband processing tasks such as QAM detection. While linear detection algorithms have low computational complexity, their use in Massive MIMO scenario has heavy degradation in error performance. Nonlinear detection methods such as Maximum Likelihood and Sphere Decoding have good error performance, but they suffer from high, variable, and uncontrollable computational complexity. For such cases, the K-best QAM detection algorithm can provide required control over the system performance while maintaining near-ML error performance. In this paper, hard-output, as well as soft-output K-best QAM detection, is implemented in a CPU by utilizing the multiple cores combined with vector processing. Similarly, hard-output detection in a GPU is implemented by leveraging the SIMD (Single Instruction, Multiple Data) architecture and Warp-based execution model. The processing time per bit and the energy consumption per bit are compared for CPU and GPU implementations for QAM constellation density and MIMO array size. The GPU implementation shows up to 5× processing latency per bit improvement and up to 120× energy consumption per bit improvement over the CPU implementation for typical QAM constellations such as 4, 16, and 64 QAM. GPU implementation also shows up to 125× improvement over CPU implementation in energy consumption per bit for larger MIMO configurations such as 24 × 24 and 32 × 32. Finally, the soft-output detector is combined with a LDPC (Low-Density Parity Check) decoder to obtain the FER (Frame Error Rate) performance for CPU implementation. The FER is then combined with frame processing latency to form a Goodput metric to demonstrate the latency and reliability tradeoff.

The circularly polarized MIMO(multiple input multiple output ) antenna is used to improve the bandwidth.The antenna is based on coplanar waveguide (CPW)-fed monopole extension of an microstrip line. The orthogonal field components required by circular polarization are induced by using a modified left/right side ground plane. In specific, a stub extending from the ground plane along with the length of the microstrip line is vertical component and the current along the width of the ground plane is horizontal component. A coplanar waveguide feeding is used with asymmetrical ground planes along the longitudinal axis of the microstrip line. One side of the ground plane is etched to create a loop-like path for the current flow. The proposed MIMO antenna features |S11| ≤ 10 dB and |S21| ≤ 22 dB from 5.1 GHz to 6.4 GHz. The antenna can operate in either uni-directional or bi-directional characteristics. It also includes multiple commerical application band like WLAN,ISM higher bands and U-NII bands.

The theory of wireless information and power transfer in energy constrained wireless networks has caught the interest of researchers due to its potential in increasing the lifetime of sensor nodes and mitigate the environment hazards caused by conventional cell batteries. Similarly, the advancements in areas of cooperative spectrum sharing protocols has enabled efficient use of frequency spectrum between a licensed primary user and a secondary user. In this paper, we consider an energy constrained secondary user which harvests energy from the primary signal and relays the primary signal in exchange for the spectrum access. We consider Nakagami-m fading model and propose two key protocols, namely time-splitting cooperative spectrum sharing (TS-CSS) and power-sharing cooperative spectrum sharing (PS-CSS), and derive expressions for the outage probabilities of the primary and secondary user in decode-forward and amplify-forward relaying modes. From the obtained results, it has been sho...

This work investigates an array antenna rotation (AAR) technique in order to minimize inter-user correlation for massive multiple-input-multiple-output (MIMO) in pure line-of-sight (LoS) environment. Traditional planar arrays have better signal separation performance than linear arrays and can create three dimensional beams. However, when the angular separation of some signals between the users from/to the base station (BS) are small, the interference suppression (i.e., signal separation) performance degenerates since the projection points onto horizontal and vertical axes of several antenna elements overlap and spatial resolution along each axis is degraded. The aim is to improve inter-user correlation performance via mechanical rotation angle optimization. We propose a recursive bisection algorithm for rotation angle optimization by finding the optimal antenna rotation angle. Simulation results show in particular that the rotation of antenna body at the BS has inter-user correlation impact on large number of antennas in both horizontal and vertical resolutions. The 5th percentile inter-user correlation values of 8 × 16, 16 × 32, 32 × 64, 64 × 128 and 128 × 136 AAR configurations are 0.96, 0.86, 0.53, 0.03, and 0.00, respectively. This means that inter-user correlation increases with decrease in number of antennas and can be achieved in practice. Finally, the spatial decorrelation of AAR is superior compared to parallelogram planar array (PPA) and uniform planar array (UPA) because of mechanical rotation of antenna body.

Multimedia Broadcast and Multicast Service (MBMS) as video broadcast or mobile television is intended to use spectrum-efficient multimedia services, by transmitting data over a common radio channel, where the bottleneck is placed to a large group of users. This book proposes and studies several advances in transmission techniques and receivers to support emergent wireless needs for MBMS requirements. These new services require extensive exploitation of advanced schemes as Multiple Input Multiple Output (MIMO), hierarchical constellations, multi-resolution transmission, macro-diversity principles and Multihop relay techniques. All of these principles are studied and advances are proposed for different environments, using both Wideband -Code Division Multiple Access (WCDMA) and Orthogonal Frequency Division Multiple Access (OFDMA). It is shown that OFDMA access technique associated to the identified techniques and receiver advancements make the wireless medium able to satisfy the current and emergent MBMS requirements.

This paper analyzes the relationship between throughput performance and CSI Type-I feedback in 5G NR. CSI Type-I, with its coarse feedback granularity, enables reduced overhead but limits beamforming precision. We evaluate how these constraints impact spectral efficiency, highlighting the trade-off between signaling simplicity and achievable throughput in realistic deployment scenarios.

Recent Advances in Wireless Communications and Networks 60 are available at the receiver. In fading channels, some samples are severely faded, while others are less attenuated; hence, in statistics, the probability of the signal strength of all samples being simultaneously below a given level becomes small, as compared with the case without applying diversity techniques. Consequently, we can overwhelm the channel fading by imposing an appropriate selection or combination of various samples, so as to dramatically improve the signal quality. Based on signal processing domains to obtain diversity gains, diversity techniques can be classified into time, frequency and space diversity. Here, we focus on space diversity techniques where multiple antennas are deployed at the transmitter or receiver sides. One category of space diversity schemes is to combine multiple signal replicas at the receiver, which is termed as receive diversity. The other category is to use multiple antennas at the transmitter, and this kind of diversity schemes is called transmit diversity . In this section, we first present various receive diversity schemes, including selection combining, switch combining, equal-gain combining (EGC), and MRC. The well-known Alamouti's transmit diversity scheme using two transmit antennas and one receive antenna is then introduced. The generalized case using two transmit antennas and multiple receive antennas is shown as well. Subsequently, space-time block codes (STBCs) with the number of transmit antennas larger than two are presented. Finally, a maximum ratio transmission (MRT) scheme is discussed to simultaneously achieve both transmit and receive diversity gains and maximize the output signal-to-noise ratio (SNR) . In cellular systems, receive diversity techniques have been widely applied at base stations for uplink transmission to improve the signal reception quality. This is mainly because base stations can endure larger implementation size, power consumption, and cost. In general, the performance of the receive diversity not only depends on the number of antennas but also the combining methods utilized at the receiver side. According to the implementation complexity and the extent of channel state information required at the receiver, we will introduce four types of combining schemes, including selection combining, switch combining, EGC, and MRC, in the following. Selection combining is a simple receive diversity combining scheme. Consider a receiver equipped with n R receive antennas. Fig. depicts the block diagram of the selection combining scheme. The antenna branch with the largest instantaneous SNR is selected to receive signals at every symbol period. In practical, since it is difficult to measure the SNR, one can implement the selection combining scheme by accumulating and averaging the received signal power, consisting of both signal and noise power, for all antenna branches, and selecting one branch with the highest output signal power.

There are considered problems of turbocode using in special telecommunication systems in the article. There are showed basic principles of turbocode building and they characteristics.Рассмотрены вопросы применения турбокодов в специальных телекоммуникационных системах. Указаны основные принципы построения турбокодов и их характеристики

In this paper, the problem of joint oscillator phase noise (PHN) estimation and data detection for multi-input multi-output (MIMO) systems using bit-interleaved coded modulation (BICM) is analyzed. A new MIMO receiver that iterates between the estimator and the detector, based on the expectation-maximization (EM) framework, is proposed. It is shown that at high signal-to-noise ratios, a maximum a posteriori estimator (MAP) can be used to carry out the maximization step of the EM algorithm. Moreover, to reduce the computational complexity of the proposed EM algorithm, a soft decision-directed extended Kalman filter-smoother (EKFS) is applied instead of the MAP estimator to track the PHN parameters. Numerical results show that by combining the proposed EKFS based approach with an iterative detector that employs low density parity check (LDPC) codes, PHN can be accurately tracked. Simulations also demonstrate that compared to existing algorithms, the proposed iterative receiver can significantly enhance the performance of MIMO systems in the presence of PHN.

This paper presents a compact penta-band Multiple Input Multiple Output (MIMO) Dielectric Resonator Antenna (DRA). The proposed MIMO DRA consists of two rectangular DRs incorporating complementary split ring resonators (CSRRs) and an inverted T-shaped slot. The MIMO DRA achieves low impedance matching through simple microstrip feedlines, which is further enhanced by integrating a microstrip line with the DRA itself. Remarkably, the introduction of CSRRs enables the design to resonate at five distinct frequency bands, namely 2.8 GHz, 4.4 GHz, 5.8 GHz, 6.4 GHz, and 6.9 GHz. The simulated properties of the MIMO DRA were validated through over-the-air measurements performed on a fabricated prototype. The proposed MIMO design demonstrates impedance bandwidths of 2.09 %, 2.43 %, 2.17 %, 2.55 %, and 4.91 % at the above respective resonance frequencies. The proposed design exhibits exceptional stability in radiation pattern, featuring a noteworthy peak gain of 6.08 dBi and an efficiency of 91.35 %. Notably, the incorporation of an inverted T-shaped slot effectively enhances isolation between the MIMO elements, achieving a maximum diversity gain of 10 dB and an envelope correlation coefficient of 0.005 over 20 dB isolation. A good agreement between the simulation and measured results is obtained, which underscores the suitability of the CSRR-based MIMO DRA for multiband wireless applications (blue tooth, radio astronomy, remote sensing, WIFI, satellite television and 6G), making it a very valuable contribution to the field.

This article introduces a dual-functional low-profile compact multiple input multiple output (MIMO) antenna array for multi-band communication in 5G smartphones. The proposed eight elements of the antenna array form two different 4×4 MIMO systems. The first four elements are placed at the four mobile corners and operate in a single band of 3.445-3.885 GHz for 5G n77 and n78 applications. The other system, in which four antennas are positioned in the middle of the terminal board, supports two wide bands of 1.684-2.300 GHz and 4.432 .638 for n2, n3, n39, n65, n66, n79, and WLAN applications. The second iteration of a modified Peano-type fractal geometry served as the design foundation for the proposed antenna element. The system's ground plane design is based on self-isolated and spatial diversity methods. The single-band MIMO system's isolation is better than 23 dB. In the dual-band MIMO system that is based on self-isolation, isolation equals approximately 16 dB in the higher band and 10 dB in the lower band. To evaluate performance, radiation-related and total antenna efficiencies, scattering parameters and gains were investigated. Additionally, ECCs have been considered to evaluate MIMO performance. According to the results, such design constitutes a valuable option for MIMO applications in 5G smartphones.

This article introduces a dual-functional low-profile compact multiple input multiple output (MIMO) antenna array for multi-band communication in 5G smartphones. The proposed eight elements of the antenna array form two different 4×4 MIMO systems. The first four elements are placed at the four mobile corners and operate in a single band of 3.445-3.885 GHz for 5G n77 and n78 applications. The other system, in which four antennas are positioned in the middle of the terminal board, supports two wide bands of 1.684-2.300 GHz and 4.432 .638 for n2, n3, n39, n65, n66, n79, and WLAN applications. The second iteration of a modified Peano-type fractal geometry served as the design foundation for the proposed antenna element. The system's ground plane design is based on self-isolated and spatial diversity methods. The single-band MIMO system's isolation is better than 23 dB. In the dual-band MIMO system that is based on self-isolation, isolation equals approximately 16 dB in the higher band and 10 dB in the lower band. To evaluate performance, radiation-related and total antenna efficiencies, scattering parameters and gains were investigated. Additionally, ECCs have been considered to evaluate MIMO performance. According to the results, such design constitutes a valuable option for MIMO applications in 5G smartphones.

In this paper, a novel approach is proposed for the orthogonal frequency-division multiplexing (OFDM) SAR imaging, where a sufficient cyclic prefix (CP) is added to each OFDM pulse. As the key in a wireless communications system, the sufficient CP insertion converts an inter symbol interference (ISI) channel from multi paths into multiple ISI-free sub channels. Analogously, it provides an inter-range-cell interference (IRCI)-free (high range resolution) SAR image in a SAR system. In the past secondand third-generation wireless communications, the existing linear-frequencymodulated (or step frequency) and random noise synthetic aperture radar (SAR) systems are corresponds to the frequency-hopping and direct-sequence spread spectrum systems. The sufficient CP insertion along with our newly proposed SAR imaging algorithm, particularly for the OFDM signals differentiates all the existing studies in the literature on OFDM radar signal processing. Simulation results are presented to illus...

A triple‐band multi‐input multi‐output (MIMO) antenna is presented.The proposed antenna consists of a C‐shaped monopole antenna that provides dual‐band resonant antenna. By protruding an L‐shaped parasitic strip on the ground plane, a third band as well as enhancement of the isolation between two ports in MIMO array is achieved. The proposed antenna can cover 2.1–2.6, 3.3–4, and 5.4–6 GHz, which are allocated for WLAN and WiMAX applications. The proposed triple‐band antenna structure is used in different two‐element MIMO arrays. Simulation results show that the S11, S12, and S22 of the MIMO arrays are independent of the position of the two‐element. The results show good S‐parameters, high peak gain and radiation efficiency, and stable radiation patterns among the triple‐band coverage. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1321–1325, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26799

We consider a millimeter-wave communication system where the fading channel follows the Nakagami-m distribution. We derive performance limits of such a system in terms of the diversity and coding gains. First, we argue that although traditional design criteria for space-time codes (STCs) are optimal for Rayleigh and Rician fading channels, they fail to capture the optimal diversity and coding gains for Nakagami-m fading channels. Then, we derive a tight upper bound on the average pair-wise error probability at high signal-to-noise ratios. From such a bound, we obtain upper and lower bounds on the diversity and coding gains of any STC over the Nakagami-m fading channel. We then identify necessary and sufficient conditions for STCs to achieve the upper bounds, leading to a fundamental trade-off between maximizing the diversity and coding gains. We also investigate the effect of blockage using stochastic geometry. We show that the diversity and coding gains are limited by the non-line-of-sight link. Numerical simulations assuming different fading scenarios further illustrate that STCs that satisfy the new design achieve full diversity. Whereas, STCs that are otherwise optimal for Rayleigh and Rician channels do not. Furthermore, in a typical indoor environment, blockage reduces the coding gain by 1.5 dB for BERs less than 10^{-3} .