Diversity mdir receiver for space-time dispersive channels

A particular property of the cellebrated MDIR receiver is introduced in this communication, namely, the fact that full exploitation of the diversity is obtained with multiple beamformers when the channel is spatially and timely dispersive. Therefore a new structure is developped which provides better performance. The hardware need for this new receiver may be obtained through reconfigurability of the RAKE architectures available at the base station. It will be tested in the FDD mode of UTRA.Peer ReviewedPostprint (published version

CMA algoritmos de módulo constante en ecualización adaptativa

An adaptative digital filtering algorithm that can compensate for both frequency-selective multipath and interference on constant envelope modulated signals is presented. The reported algorithm adapts the coefficients of a finite- imoulse-response (FIR) digital filter. The main advantage of the CMA algorithm resides that it doesn't need trainig or reference signal in order to perfom. The adquisition or tracking; thus, it is continuosly adapted without further needs as DFE methods and references which fardly constraint the nobiastress of the Wiener approach.Peer ReviewedPostprint (published version

Rayleigh estimates: performing like SVD

This paper describes the structure of the so- called Rayleigh estimates and the features they share with indirect SVD like procedures. The problem of finding procedures of high resolution in spectral estimation is faced under the framework of non-linear estimates of the autocorrelation matrix and the low rank approximation to the frequency estimation problem. It is shown the existing relations hip between the proposed estimates and the principal component analysis. The main advantages of the procedure is that the performance of the spectral estimates reported herein is almost equal to SVD techniques, yet preserving a good asymptotic convergence to the actual power spectral density. Also, the procedure could be viewed under variotional concepts revealing its potential under adaptive schemes and data adaptive windowing for spectral estimation. In summary, the work shows how classical constrained Wiener filtering with data adaptive windowing can enhance the performance of SVD met hods with very low complexity.Peer ReviewedPostprint (published version

Negative lateral conductivity of hot electrons in a biased superlattice

Nonequilibrium electron distribution in a superlattice subjected to a homogeneous electric field (biased superlattice with equipopulated levels) is studied within the tight-binding approximation, taking into account the scattering by optical and acoustic phonons and by lateral disorder. It is found that the distribution versus the in-plane kinetic energy depends essentially on the ratio between the Bloch energy and the optical phonon energy. The in-plane conductivity is calculated for low-doped structures at temperatures 4.2 K and 20 K. The negative conductivity is found for bias voltages corresponding to the Bloch-phonon resonance condition.Comment: 12 pages, 7 figure

Total Roman Domination Number of Rooted Product Graphs

[EN] Let G be a graph with no isolated vertex and f:V(G)->{0,1,2} a function. If f satisfies that every vertex in the set {v is an element of V(G):f(v)=0} is adjacent to at least one vertex in the set {v is an element of V(G):f(v)=2}, and if the subgraph induced by the set {v is an element of V(G):f(v)>= 1} has no isolated vertex, then we say that f is a total Roman dominating function on G. The minimum weight omega(f)= n-ary sumation v is an element of V(G)f(v) among all total Roman dominating functions f on G is the total Roman domination number of G. In this article we study this parameter for the rooted product graphs. Specifically, we obtain closed formulas and tight bounds for the total Roman domination number of rooted product graphs in terms of domination invariants of the factor graphs involved in this product.Cabrera Martinez, A.; Cabrera García, S.; Carrión García, A.; Hernandez Mira, FA. (2020). Total Roman Domination Number of Rooted Product Graphs. Mathematics. 8(10):1-13. https://doi.org/10.3390/math8101850S11381