Non-cooperative Systems Research Articles

Multi-Cell Sparse Activity Detection for Massive Random Access: Massive MIMO Versus Cooperative MIMO

This paper considers sparse device activity detection for cellular machine-type communications with non-orthogonal signatures using the approximate message passing algorithm. This paper compares two network architectures, massive multiple-input multiple-output (MIMO) and cooperative MIMO, in terms of their effectiveness in overcoming inter-cell interference. In the massive MIMO architecture, each base station (BS) detects only the users from its own cell while treating inter-cell interference as noise. In the cooperative MIMO architecture, each BS detects the users from neighboring cells as well; the detection results are then forwarded in the form of log-likelihood ratio (LLR) to a central unit where final decisions are made. This paper analytically characterizes the probabilities of false alarm and missed detection for both architectures. Numerical results validate the analytic characterization and show that as the number of antennas increases, a massive MIMO system effectively drives the detection error to zero, while as the cooperation size increases, the cooperative MIMO architecture mainly improves the cell-edge user performance. Moreover, this paper studies the effect of LLR quantization to account for the finite-capacity fronthaul. Numerical simulations of a practical scenario suggest that in that specific case cooperating three BSs in a cooperative MIMO system achieves about the same cell-edge detection reliability as a non-cooperative massive MIMO system with four times the number of antennas per BS.

Iterative greedy user clustering algorithm for D2D–relay in vehicular communication systems

Device-to-device (D2D) communications help in improving the performance of wireless services in cellular networks via enabling cooperation among mobile users. Further, compared to traditional pairwise cooperation, cluster-wise cooperation can achieve even higher spectral and power efficiency. D2D clustering certainly can be a great supporting technology for the future of intelligent transportation. In this study, the authors investigate the D2D–relay clustering network in the vehicular scenario and propose a new clustering scheme named iterative greedy user clustering (IGUC). By exploiting those vehicles with better channel state, system resources can be saved. Here, they mainly focus on the question which is by applying D2D–relay clustering among vehicles, how much bandwidth could be saved in the uplink. This problem is mathematically formulated into a non-linear binary programming problem with the goal being minimum spectrum usage. Due to the NP-hardness, the low-complexity suboptimal algorithm IGUC is introduced to tackle it. Simulation results show that compared to the non-cooperative uplink system, IGUC saves a considerable proportion of the spectrum. Furthermore, clusters in denser and further areas tend to produce a higher gain. Influence of the fast time-varying characteristic of vehicular wireless channels is also investigated, upon which an adaptive switch mechanism is proposed to further facilitate IGUC.

A robust modulation classification method using convolutional neural networks

Automatic modulation classification (AMC) is a core technique in noncooperative communication systems. In particular, feature-based (FB) AMC algorithms have been widely studied. Current FB AMC methods are commonly designed for a limited set of modulation and lack of generalization ability; to tackle this challenge, a robust AMC method using convolutional neural networks (CNN) is proposed in this paper. In total, 15 different modulation types are considered. The proposed method can classify the received signal directly without feature extracion, and it can automatically learn features from the received signals. The features learned by the CNN are presented and analyzed. The robust features of the received signals in a specific SNR range are studied. The accuracy of classification using CNN is shown to be remarkable, particularly for low SNRs. The generalization ability of robust features is also proven to be excellent using the support vector machine (SVM). Finally, to help us better understand the process of feature learning, some outputs of intermediate layers of the CNN are visualized.

Wave propagation for a class of non-local dispersal non-cooperative systems

AbstractThis paper is concerned with the travelling waves for a class of non-local dispersal non-cooperative system, which can model the prey-predator and disease-transmission mechanism. By the Schauder's fixed-point theorem, we first establish the existence of travelling waves connecting the semi-trivial equilibrium to non-trivial leftover concentrations, whose bounds are deduced from a precise analysis. Further, we characterize the minimal wave speed of travelling waves and obtain the non-existence of travelling waves with slow speed. Finally, we apply the general results to an epidemic model with bilinear incidence for its propagation dynamics.

On the Spectral Efficiency of Noncooperative Uplink Massive MIMO Systems

Massive multiple-input multiple-output (MIMO) systems have been drawing considerable interest due to the growing throughput demands on wireless networks. In the uplink, massive MIMO systems are commonly studied assuming that each base station (BS) decodes the signals of its user terminals separately and linearly while treating all interference as noise. Although this approach provides improved spectral efficiency which scales with the number of BS antennas in favorable channel conditions, it is generally sub-optimal from an information-theoretic perspective. In this paper, we characterize the spectral efficiency of massive MIMO when the BSs are allowed to jointly decode the received signals. In particular, we consider four schemes for treating the interference, and derive the achievable average ergodic rates for both finite and asymptotic number of antennas for each scheme. Simulation tests of the proposed methods illustrate their gains in spectral efficiency compared with the standard approach of separate linear decoding, and show that the standard approach fails to capture the actual achievable rates of massive MIMO systems, particularly when the interference is dominant.

Integrated Positioning for Connected Vehicles

In the era of autonomous cars, accurate vehicular positioning becomes very essential. The global navigation satellite systems (GNSS) suffer from signal blockage and severe multipath in urban canyons, which degrades the positioning accuracy and availability. Therefore, vehicles solely relying on positioning from GNSS receivers have limited performance. In this research, we present a novel unified cooperative positioning solution which enhances positioning accuracy and availability in urban canyons. The proposed system exploits the fact that vehicles have different positioning resources and is based on angle approximation, which artificially generates the hindered pseudorange by sharing angle information between vehicles using dedicated short-range communication. In addition, we propose a system that employs the proposed cooperative technique to assist the loose integration between the inertial navigation system (INS) and the GPS system (using extended Kalman filter) during partial GPS outages. Using raw data from inertial sensors and GPS receivers in the real road trajectories, we implement the cooperative INS/GPS loose integration and show that our cooperative integrated system outperforms the non-cooperative integrated system. The performance metrics used are the 2-D positioning root-mean-square error, the maximum 2-D positioning error, and the positioning accuracy gain (PAG). Specifically, the PAG gain is around 88%, 80%, and 60% when the number of blocked satellites is one, two, and three, respectively.

Multiple Solutions for a Non-cooperative Elliptic System of Kirchhoff Type Involving p$p$-Biharmonic Operator and Critical Growth

In this paper, we consider a class of non-cooperative elliptic systems of Kirchhoff type involving $p$-biharmonic operator and critical growth. With the help of the Limit index theory due to Li (Nonlinear Anal. TMA 30(7):4619–4627, 1997) and the concentration compactness principle, we establish the existence of infinitely many solutions for the problem under the suitable conditions on the nonlinearity.

Deep Learning Aided Method for Automatic Modulation Recognition

Automatic modulation recognition (AMR) is considered one of most important techniques in the non-cooperative wireless communication systems. Traditional algorithms, e.g., support vector machine (SVM) based on high order cumulants (HOC), are hard to achieve the reliable performance. In this paper, we propose an effective AMR algorithm based on deep learning (DL) with capabilities of automatically extracting representative and effective features. Our proposed method resorts to in-phase and quadrature (IQ) samples which are IQ components of received baseband signal, respectively. We adopt convolutional neural networks (CNN) and recurrent neural networks (RNN) to classify six types of signal modulations over additive white Gaussian noise (AWGN) channel and Rayleigh fading channel, respectively. Simulation results show that DL-AMR is much better than traditional algorithms under two fading channels.

Blind Reconstruction of Reed-Solomon Encoder and Interleavers Over Noisy Environment

Blind estimation of code and interleaver parameters is useful in smart storage systems and ubiquitous communication applications such as adaptive modulation and coding, reconfigurable radio systems, non-cooperative radio systems, etc. In this paper, we analyze Reed-Solomon (RS) encoded data stream and propose blind estimation algorithms to identify RS code parameters. We also provide algorithms to estimate block interleaver parameters from RS coded and block interleaved data stream. In addition, synchronization compensation through appropriate bit/symbol positioning is integrated with the proposed code and interleaver parameter estimation algorithms. Simulation results validating the proposed algorithms are given for various test cases involving both erroneous and non-erroneous scenarios. Moreover, the accuracy of estimation of RS code and block interleaver parameters are also given with detailed inferences for different modulation schemes, codeword length, and code dimension values. It has been inferred that the accuracy of parameter estimation improves with decrease in code dimension and codeword length values of RS codes. Further, the accuracy of estimation of lower modulation order schemes is better when compared to higher modulation order schemes as expected. It has also been noted that the proposed code and interleaver parameter estimation algorithms for noisy environment consistently outperform the algorithms proposed in the prior works.

Symmetry of components and Liouville-type theorems for semilinear elliptic systems involving the fractional Laplacian

In this paper, we study the symmetry of components of positive solutions for the fractional elliptic systems in the whole space RN. As an application, we prove the uniqueness of positive solutions for fractional Schrödinger type systems with critical exponents. We also prove the symmetry of components and some Liouville type theorems for a class of fractional noncooperative systems, which contains the systems arising in Bose–Einstein condensation and in biological models of Lotka–Volterra type.

On the Feasibility of Full-Duplex Large-Scale MIMO Cellular Systems

This paper concerns the feasibility of full-duplex large-scale multiple-input-multiple-output cellular systems. We first derive the analytic model of the ergodic achievable sum-rate for cell-boundary users. The model is derived by applying a simple linear filter, i.e., matched filter or zero-forcing filter, to the base-station (BS). In the analytic model, we consider large-scale fading, pilot contamination, transmitter noise, and receiver distortion. In addition, to solve the critical pilot overhead problem induced by self-interference channel estimation, we propose a pilot transmission scheme—the simultaneous pilot transmission (SPT)—and assess its performance, in terms of the ergodic sum-rate. In considering two multicell scenarios, cooperative and non-cooperative multicell systems, we obtain the ergodic achievable sum-rate by reflecting the characteristic of each scenarios, such as limited front-haul capacity and procedures of channel estimation. With all derived results, to investigate the feasibility, we observe the tradeoffs between the full- and half-duplex systems, between the SPT and conventional scheme, and between the two multicell scenarios with respect to various system parameters and environment. In the end, we confirm the tightness of our analytic model and advantages of full-duplex, SPT, and cooperation of BSs in our system model.

Optimal Operation of the Eastern Nile System Using Genetic Algorithm, and Benefits Distribution of Water Resources Development

The Eastern Nile Basin is facing a number of transboundary issues, including water resources development, and the associated impacts. The Nile Basin, particularly the Eastern Nile Sub-basin, is considered as one of a few international river systems of potential conflicts between riparian countries. The Eastern Nile is characterized by the high dependency of downstream countries on river water generated in upstream countries, with limited or no contribution to the runoff itself. The aim of this paper is to analyze optimal scenarios for water resources management in the Eastern Nile with regard to hydropower generation and irrigation development. A hydro-economic optimization model based on Genetic Algorithm has been used to determine the maximum benefits for two scenarios: (i) non-cooperative management of hydraulic infrastructure by the riparian countries (status quo), and (ii) cooperative water resources management among the riparian countries. The hydro-economic model is developed using a Genetic Algorithm and deterministic optimization approach covering all hydraulic infrastructures in the Eastern Nile, existing and planned, including the Grand Ethiopian Renaissance Dam (GERD). The results show that cooperative management yields an increase in hydro-energy returns for all countries compared to the status quo, with a very high increase in Ethiopian’s returns, as expected. Non-cooperative system management would negatively impact the hydro-energy of Egypt compared to the cooperative management (reduced by 11%), without a significant increase of hydro-energy for Ethiopia. For Sudan, the results show that hydropower generation benefits from the presence of GERD, in both management scenarios. Non-cooperative management of the system, along with the internal trade-off between irrigation and hydropower facilities, would negatively impact irrigation supply in Sudan. The findings support the argument of positive impact of GERD development on the three Eastern Nile riparian countries, Ethiopia, Sudan and Egypt, provided that the three countries agree to manage the system cooperatively.

Positive solutions for a class of non-cooperative [formula omitted]-Laplacian systems with singularities

We study the existence of positive solutions to the non-cooperative pq-Laplacian system −Δpu=λf(u,v)inΩ,−Δqv=λg(u,v)inΩ,with Dirichlet boundary conditions on a bounded domain Ω with smooth boundary ∂Ω, where f,g:(0,∞)×(0,∞)→R are allowed to have infinite semipositone structure at u=0 or v=0. Our approach is based on the Schauder fixed point theorem.

Non-cooperative Fisher–KPP systems: Asymptotic behavior of traveling waves

This paper is concerned with non-cooperative parabolic reaction–diffusion systems which share structural similarities with the scalar Fisher–KPP equation. In a previous paper, we established that these systems admit traveling wave solutions whose profiles connect the null state to a compact subset of the positive cone. The main object of this paper is the investigation of a more precise description of these profiles. Non-cooperative KPP systems can model various phenomena where the following three mechanisms occur: local diffusion in space, linear cooperation and superlinear competition.

Stable Downlinks for Wideband Radio Frequencies in Distributed Noncooperative System

A stable downlink transmission scheme for wideband anonymous microwave signals in distributed noncooperative system has been proposed and experimentally demonstrated based on an optical switch (OS) scanning. With the round-trip transmission of a pilot carrier, the delay variation of fiber induced by environment is obtained continuously, and can be canceled by controlling variable optical delay line. Furthermore, assisted by an OS, four stable optical downlinks can be realized by employing only one phase drift correction unit, leading to the significant reduction of the system cost increment. Experimental results show that target signals at frequencies of 2 and 18 GHz have been downlink transferred from four different remote ends with the phase fluctuation of only 3.6° and 8.4° at 2 hours through 0.5-km fiber. In addition, the stable phase value for channel can be adjusted from −150° to 150° individually.

When object production tunes the efficiency of membrane systems

P systems with active membranes is one of the most studied models within the field of Membrane Computing. Simulating the organization and behavior of the living cells through a tree-like structure and abstracting the mechanisms that help the cell to keep alive into rules (evolution, communication, dissolution and division rules), they have been used to solve several computationally hard problems. We are dealing with non-cooperative systems here, that is, the number of reactives in a rule is always one. Even then, it has been proven that problems from the class PSPACE can be solved, so in order to acquire a minimal model that can solve computationally hard problems, polarizations are removed. In this paper we find the relevance of the length of the right-hand side of the rule, being necessary when using separation rules and being irrelevant when division rules are used, improving some solutions previously presented, restricting the right-hand side of the rules, obtaining new frontiers of efficiency in this framework. The state of the art of these systems is presented in a graphical way.

Rabinowitz Alternative for Non-cooperative Elliptic Systems on Geodesic Balls

Abstract The purpose of this paper is to study properties of continua (closed connected sets) of nontrivial solutions of non-cooperative elliptic systems considered on geodesic balls in S n {S^{n}} . In particular, we show that if the geodesic ball is a hemisphere, then all these continua are unbounded. It is also shown that the phenomenon of global symmetry-breaking bifurcation of such solutions occurs. Since the problem is variational and SO ⁡ ( n ) {\operatorname{SO}(n)} -symmetric, we apply the techniques of equivariant bifurcation theory to prove the main results of this article. As the topological tool, we use the degree theory for SO ⁡ ( n ) {\operatorname{SO}(n)} -invariant strongly indefinite functionals defined in [A. Gołȩbiewska and S. A. Rybicki, Global bifurcations of critical orbits of G-invariant strongly indefinite functionals, Nonlinear Anal. 74 2011, 5, 1823–1834].

Research on effect of rough surface on FMCW laser radar range accuracy

The non-cooperative targets large scale measurement system based on frequency-modulated continuous-wave (FMCW) laser detection and ranging technology has broad application prospects. It is easy to automate measurement without cooperative targets. However, the complexity and diversity of the surface characteristics of the measured surface directly affects the measurement accuracy. First, the theoretical analysis of range accuracy for a FMCW laser radar was studied, the relationship between surface reflectivity and accuracy was obtained. Then, to verify the effect of surface reflectance for ranging accuracy, a standard tool ball and three standard roughness samples were measured within 7 m to 24 m. The uncertainty of each target was obtained. The results show that the measurement accuracy is found to increase as the surface reflectivity gets larger. Good agreements were obtained between theoretical analysis and measurements from rough surfaces. Otherwise, when the laser spot diameter is smaller than the surface correlation length, a multi-point averaged measurement can reduce the measurement uncertainty. The experimental results show that this method is feasible.

Improving the Performance of Cell-Edge Users in MISO-NOMA Systems Using TAS and SWIPT-Based Cooperative Transmissions

In this paper, we study the performance of a cell-edge user in a two-user multiple-input single-output non-orthogonal multiple access (MISO-NOMA) system. Since the outage performance and fairness data rate of cell-edge users are essential issues in NOMA systems, we focus on how to resolve such problems. To this end, we propose three cooperative downlink transmission schemes utilizing hybrid simultaneous wireless information and power transfer (SWIPT) and transmit antenna selection (TAS) protocols. Particularly, in each scheme, a cell-center user acts as a relay to assist the cell-edge user and its relaying operation is powered by a hybrid time-switching/power-splitting SWIPT protocol. Additionally, each scheme employs a different TAS criterion to exploit the spatial diversity gain of a multiple antennas base station. In particular, we derive tight closed-form approximate expressions for the outage probabilities (OPs) and the corresponding asymptotic OPs to provide significant insights into the impact of our proposed schemes on the system performance. Our numerical results demonstrate the achievable performance improvements of the proposed schemes in comparison to that of the orthogonal multiple access and non-cooperative NOMA systems. In addition, the proposed schemes achieve various level of diversity gains accompanying with different complexity requirements.

Acoustic Detection of a Fixed-Wing UAV

The following paper presents results obtained from experiments conducted to investigate the viability of acoustic sensing to form the basis of a non-cooperative aircraft collision avoidance system. An unmanned aerial vehicle (UAV) fitted with two microphones was flown in the vicinity of another airborne UAV to determine the maximum distance at which the intruding aircraft could be detected. A two-dimensional analytical model to approximate the minimum detection distance required to facilitate an avoidance maneuver for a given spatial configuration is presented. A method to increase detection distances by exploiting the harmonic nature of acoustic signals generated by propeller-driven aircraft is also presented. The method significantly increases the detection distances compared to the commonly used incoherent spectral mean. It was found that a small gasoline-powered UAV could be detected at distances up to 678 m, which is more than double the minimum required to avoid a head-on collision.