Recent Advances in RF Propagation Modeling for 5G Systems

Stefanovic, M.; Panic, SR.; De Souza, RAA.; Reig, J. (2017). Recent Advances in RF Propagation Modeling for 5G Systems. International Journal of Antennas and Propagation (Online). 2017(4701208):1-5. doi:10.1155/2017/4701208S152017470120

The complex α-μ fading channel with OFDM application

The aims of this paper are threefold: (i) to present a model for the complex - fading channel; (ii) to propose an efficient, simple, and general method to generate complex - samples; (iii) to make use of this channel in order to assess the bit error rate performance of an OFDM system. An analytical framework is then used, whose output is validated through Monte Carlo simulation. Several important conclusions concerning the system performance as a function of the channel parameters, namely, nonlinearity, clustering, and power imbalance of in-phase and quadrature components, are drawn2017Recent advances in RF propagation modeling for 5G systemsFINANCIADORA DE ESTUDOS E PROJETOS - FINEP01.14.0231.0

Low-Complexity Dynamic Directional Modulation: Vulnerability and Information Leakage

In this paper, the privacy of wireless transmissions is improved through the use of an efficient technique termed dynamic directional modulation (DDM), and is subsequently assessed in terms of the measure of information leakage. Recently, a variation of DDM termed low-power dynamic directional modulation (LPDDM) has attracted significant attention as a prominent secure transmission method due to its ability to further improve the privacy of wireless communications. Roughly speaking, this modulation operates by randomly selecting the transmitting antenna from an antenna array whose radiation pattern is well known. Thereafter, the modulator adjusts the constellation phase so as to ensure that only the legitimate receiver recovers the information. To begin with, we highlight some privacy boundaries inherent to the underlying system. In addition, we propose features that the antenna array must meet in order to increase the privacy of a wireless communication system. Last, we adopt a uniform circular monopole antenna array with equiprobable transmitting antennas in order to assess the impact of DDM on the information leakage. It is shown that the bit error rate, while being a useful metric in the evaluation of wireless communication systems, does not provide the full information about the vulnerability of the underlying system

Semantic-Functional Communications in Cyber-Physical Systems

This paper explores the use of semantic knowledge inherent in the cyber-physical system (CPS) under study in order to minimize the use of explicit communication, which refers to the use of physical radio resources to transmit potentially informative data. It is assumed that the acquired data have a function in the system, usually related to its state estimation, which may trigger control actions. We propose that a semantic-functional approach can leverage the semantic-enabled implicit communication while guaranteeing that the system maintains functionality under the required performance. We illustrate the potential of this proposal through simulations of a swarm of drones jointly performing remote sensing in a given area. Our numerical results demonstrate that the proposed method offers the best design option regarding the ability to accomplish a previously established task -- remote sensing in the addressed case -- while minimising the use of radio resources by controlling the trade-offs that jointly determine the CPS performance and its effectiveness in the use of resources. In this sense, we establish a fundamental relationship between energy, communication, and functionality considering a given end application

Simple and Efficient Algorithm for Improving the MDL Estimator of the Number of Sources

We propose a simple algorithm for improving the MDL (minimum description length) estimator of the number of sources of signals impinging on multiple sensors. The algorithm is based on the norms of vectors whose elements are the normalized and nonlinearly scaled eigenvalues of the received signal covariance matrix and the corresponding normalized indexes. Such norms are used to discriminate the largest eigenvalues from the remaining ones, thus allowing for the estimation of the number of sources. The MDL estimate is used as the input data of the algorithm. Numerical results unveil that the so-called norm-based improved MDL (iMDL) algorithm can achieve performances that are better than those achieved by the MDL estimator alone. Comparisons are also made with the well-known AIC (Akaike information criterion) estimator and with a recently-proposed estimator based on the random matrix theory (RMT). It is shown that our algorithm can also outperform the AIC and the RMT-based estimator in some situations

Cooperative Spectrum Sensing Using Eigenvalue Fusion for OFDMA and Other Wideband Signals

In this paper, we propose a new approach for the detection of OFDMA and other wideband signals in the context of centralized cooperative spectrum sensing for cognitive radio (CR) applications. The approach is based on the eigenvalues of the received signal covariance matrix whose samples are in the frequency domain. Soft combining of the eigenvalues at the fusion center is the main novelty. This combining strategy is applied to variants of four test statistics for binary hypothesis test, namely: the eigenvalue-based generalized likelihood ratio test (GLRT), the maximum-minimum eigenvalue detection (MMED), the maximum eigenvalue detection (MED) and the energy detection (ED). It is shown that the eigenvalue fusion can outperform schemes based on decision fusion and sample fusion. A tradeoff is also established between complexity and volume of data sent to the fusion center in all combining strategies

Maximum likelihood estimator for the α-κ-μ fading environment

In this Paper, an estimator of the α-κ-μ distribution, based on the maximum likelihood (ML) estimation method, is proposed and verified. The technique is applied in samples generated by the Smith spectrum method, which is also a contribution in this paper. This distribution has been recently proposed to model the received field strength in a nonlinear environment with line-of-sight condition. Hence, efficient estimators are required to infer the parameters of the received signal amplitude distribution in propagation mediums modeled by it. The ML estimator for the α-κ-μ distribution is derived and verified against chosen true values of the parameters by means of a simulation. We verify that, for a large sample size, the estimators are unbiased, from a practical point of view, for the useful range of α, κ and μ. The results conclude that the estimator variations about its sample mean are smaller for the α parameterIEEE Wireless Communications and Networking Conference (WCNC

Maximum likelihood estimator for the α-η-μ fading environment

In this paper, an estimator of the α-η-μ distribution is proposed based on the maximum likelihood (ML) estimation method, and verified with samples generated by three different random number generators: i) by the definition, ii) by the rejection method and iii) by the Smith Spectrum method. This distribution has been recently proposed to model the received field strength in a non-linear and non-line-of-sight scenario. Hence, efficient estimators are required to infer the parameters of the received signal amplitude distribution in propagation mediums modeled by it. The ML estimator for the α-η-μ distribution is derived and verified against chosen true values of the parameters by means of a simulation133136FINANCIADORA DE ESTUDOS E PROJETOS - FINEP01.14.0231.00IEEE Radio and Wireless Symposium (RWS