1,721,242 research outputs found
Interference in DS-CDMA Systems with Exponentially Vanishing Autocorrelations: Chaos-Based Spreading is Optimal
No full textA novel estimation of the minimum achievable interference in direct sequence-code division multiple access (DS-CDMA) systems is introduced, which holds when spreading sequences with exponentially vanishing autocorrelation are employed. This can be applied to many of the recently proposed improvements to classical maximum-length or Gold sequences, such as chaos-based spreading. Asymptotic, infinite-bandwidth results are also provided, clarifying the maximum attainable gain. Empirical evidence shows that this theoretical maximum is achieved by some chaos-based sequences which are therefore optima
Tensor Function Analysis of Quantized Chaotic Piecewise-Affine Pseudo-Markov Systems - Part I: 2nd Order Correlations and Self-Similarity
No full textA general approach is developed for the statistical
analysis of quantized trajectories produced by a class of chaotic
maps generalizing piecewise-affine Markov systems. The frame-
work is based on a generalization of the Perron–Frobenius oper-
ator and on the mapping of its properties onto properties of tensor
function algebra. The general results are specialized to the compu-
tation of second-order statistical behaviors and exemplified with
the analysis of two nontrivial maps exhibiting self-similar correla-
tion trends
Tensor Function Analysis of Quantized Chaotic Piecewise-Affine Pseudo-Markov Systems - Part II: Higher Order Correlations and Self-Similarity
No full textThe general approach developed in the companion
paper for the statistical analysis of trajectories produced by a
class of chaotic systems generalizing the classical view of piece-
wise-affine Markov maps is here applied to the computation of
higher order correlations. For any given order , a procedure
is given to write a closed form expression in the -transformed
domain for the th dimensional tensor encoding the contribution
of the system dynamics to the correlation functions of that order.
After having defined and discussed a suitable generalization of the
concept of second-order self-similarity, we finally use this general
procedure to show that simple chaotic maps may exhibit higly
nontrivial behaviors also in their higher order statistics
Queue System Analytical Study with Self-Similar Chaos-Based Traffic
No full textRecent measures on LANs have highlighted the self-similar nature of the traffic. A systematic procedure to design a 1D chaotic map, which generates a self-similar process characterised by a polynomial OFF time distribution, is considered and reviewed. This polynomial law allows the performance of a queue system to be investigated by extending the G/M/l theory to the case of discrete arrival and service processes. Analytical results are reported highlighting the impact of the traffic self-similar degree and simulations show the validity of the developed theor
Circuito elettronico riconfigurabile come convertitore analogico/digitale e generatore di sequenze binarie autenticamente casuali
No full textEMI reduction via spread spectrum in DC/DC converters: State of the art, optimization, and tradeoffs
Full text linkSpread spectrum is a technique introduced for mitigating electromagnetic interference (EMI) problems in many class of circuits. In this paper, with particular emphasis on switching DC/DC converters, we consider the most common and most efficient known spreading techniques, looking for spreading parameters that ensure the highest EMI reduction and the lowest performance reduction in the circuit where the spreading is applied. The result is an interesting tradeoff not only between EMI reduction and performance drop, but also on the EMI reduction itself when considering different EMI victim models. The proposed analysis is supported by measurements on two switching DC/DC converters: 1) based on pulsewidth modulation and 2) based on the resonant converter class
Sequence synchronization in chaos-based DS-CDMA systems
No full textThe aim of this contribution is to consider a further step in the study of the impact of chaos-based techniques on classical DS-CDMA systems. The problem addressed here is the sequence phase acquisition and tracking which is needed to synchronize the spreading and despreading sequences of each link. An acquisition mechanism is proposed and analyzed in depth to identify parameters allowing the study of its performance when classical and chaos-based sequences are employed for spreading. Numerical results show that the adoption of chaos-based techniques may lead to improvement in link startup delay and expected service availability
Tensor-based theory for quantized piecewise-affine Markov systems: Analysis of some map families
No full textIn this paper we consider a tensor-based approach to the analytical computation of higher-order expectations of quantized trajectories generated by Piecewise Affine Markov (PWAM) maps. We formally derive closed-form expressions for expectations of trajectories generated by three families of maps, referred to as (n,t)-tailed shifts, (n,t)-broken identities and (n,t,π)-mixing permutations. These families produce expectations with asymptotic exponential decay whose detailed profile is controlled by map design. In the (n,t)-tailed shift case expectations are alternating in sign, in the (n,t)-broken identity case they are constant in sign, and the (n,t,π)-mixing permutation case they follow a dumped periodic trend
A Piecewise Affine Markov Map Producing Binary Symbols With Extremely Slow-Decaying Negative Correlation
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