George E. Chatzarakis

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We investigate the asymptotic behavior of the solutions of a neutral type difference equation of the form Δ x n cx τ n p n x σ n 0, where τ n is a general retarded argument, σ n is a general deviated argument retarded or advanced , c ∈ R, p n n≥0 is a sequence of positive real numbers such that p n ≥ p, p ∈ R , and Δ denotes the forward difference operator(More)
Consider the first-order advanced difference equation of the form ∇x(n)− p(n)x(μ(n)) = 0, n ≥ 1, [∆x(n)− p(n)x(ν(n)) = 0, n ≥ 0], where ∇ denotes the backward difference operator ∇x(n) = x(n) − x(n − 1), ∆ denotes the forward difference operator ∆x(n) = x(n+ 1)− x(n), {p(n)} is a sequence of nonnegative real numbers, and {μ(n)} [{ν(n)}] is a sequence of(More)
A novel model for the outage probability prediction in time diversity satellite communication (SatCom) systems operating above 10GHz is proposed. Due to the migration of operating frequency at Ka band and above, atmospheric phenomena affect the signal. Rain is the dominant fading mechanism. Diversity techniques are the probable solution of the compensation(More)
Iterative learning control (ILC) is used to control systems that operate in a repetitive mode, improving tracking accuracy of the control by transferring data from one repetition of a task, to the next. In this paper an optimal iterative learning algorithm for discrete linear systems is designed and implemented. The design and implementation that have been(More)
Frequency bands well above 10GHz are of primary importance for current and, more importantly, future user oriented satellite communication networks. In this course, well known rain fade mitigation techniques such as site diversity are reviewed and considered for use in a different context. This paper extends previous analytical methodologies to the case of(More)
Consider the delay difference equation with continuous time of the form x(t)− x(t− 1) + m ∑ i=1 Pi(t)x(t− ki(t)) = 0, t ≥ t0, where Pi : [t0, ∞) 7→ R, ki : [t0, ∞) 7→ {2, 3, 4, . . . } and limt→∞(t − ki(t)) = ∞, for i = 1, 2, . . . , m. We introduce the generalized characteristic equation and its importance in oscillation of all solutions of the considered(More)