34,097 research outputs found
Linear Stochastic Fluid Networks: Rare-Event Simulation and Markov Modulation
We consider a linear stochastic fluid network under Markov modulation, with a
focus on the probability that the joint storage level attains a value in a rare
set at a given point in time. The main objective is to develop efficient
importance sampling algorithms with provable performance guarantees. For linear
stochastic fluid networks without modulation, we prove that the number of runs
needed (so as to obtain an estimate with a given precision) increases
polynomially (whereas the probability under consideration decays essentially
exponentially); for networks operating in the slow modulation regime, our
algorithm is asymptotically efficient. Our techniques are in the tradition of
the rare-event simulation procedures that were developed for the sample-mean of
i.i.d. one-dimensional light-tailed random variables, and intensively use the
idea of exponential twisting. In passing, we also point out how to set up a
recursion to evaluate the (transient and stationary) moments of the joint
storage level in Markov-modulated linear stochastic fluid networks
Fractional Poisson Fields and Martingales
We present new properties for the Fractional Poisson process and the
Fractional Poisson field on the plane. A martingale characterization for
Fractional Poisson processes is given. We extend this result to Fractional
Poisson fields, obtaining some other characterizations. The fractional
differential equations are studied. We consider a more general Mixed-Fractional
Poisson process and show that this process is the stochastic solution of a
system of fractional differential-difference equations. Finally, we give some
simulations of the Fractional Poisson field on the plane
Laplace Functional Ordering of Point Processes in Large-scale Wireless Networks
Stochastic orders on point processes are partial orders which capture notions
like being larger or more variable. Laplace functional ordering of point
processes is a useful stochastic order for comparing spatial deployments of
wireless networks. It is shown that the ordering of point processes is
preserved under independent operations such as marking, thinning, clustering,
superposition, and random translation. Laplace functional ordering can be used
to establish comparisons of several performance metrics such as coverage
probability, achievable rate, and resource allocation even when closed form
expressions of such metrics are unavailable. Applications in several network
scenarios are also provided where tradeoffs between coverage and interference
as well as fairness and peakyness are studied. Monte-Carlo simulations are used
to supplement our analytical results.Comment: 30 pages, 5 figures, Submitted to Hindawi Wireless Communications and
Mobile Computin
Conditional Sampling for Max-Stable Processes with a Mixed Moving Maxima Representation
This paper deals with the question of conditional sampling and prediction for
the class of stationary max-stable processes which allow for a mixed moving
maxima representation. We develop an exact procedure for conditional sampling
using the Poisson point process structure of such processes. For explicit
calculations we restrict ourselves to the one-dimensional case and use a finite
number of shape functions satisfying some regularity conditions. For more
general shape functions approximation techniques are presented. Our algorithm
is applied to the Smith process and the Brown-Resnick process. Finally, we
compare our computational results to other approaches. Here, the algorithm for
Gaussian processes with transformed marginals turns out to be surprisingly
competitive.Comment: 35 pages; version accepted for publication in Extremes. The final
publication is available at http://link.springer.co
Information-Based Models for Finance and Insurance
In financial markets, the information that traders have about an asset is reflected in its
price. The arrival of new information then leads to price changes. The ‘information-based
framework’ of Brody, Hughston and Macrina (BHM) isolates the emergence of
information, and examines its role as a driver of price dynamics. This approach has
led to the development of new models that capture a broad range of price behaviour.
This thesis extends the work of BHM by introducing a wider class of processes for the
generation of the market filtration. In the BHM framework, each asset is associated
with a collection of random cash flows. The asset price is the sum of the discounted
expectations of the cash flows. Expectations are taken with respect (i) an appropriate
measure, and (ii) the filtration generated by a set of so-called information processes that
carry noisy or imperfect market information about the cash flows. To model the flow
of information, we introduce a class of processes termed Levy random bridges (LRBs),
generalising the Brownian and gamma information processes of BHM. Conditioned on
its terminal value, an LRB is identical in law to a Levy bridge. We consider in detail
the case where the asset generates a single cash flow XT at a fixed date T. The flow
of information about XT is modelled by an LRB with random terminal value XT.
An explicit expression for the price process is found by working out the discounted
conditional expectation of XT with respect to the natural filtration of the LRB. New
models are constructed using information processes related to the Poisson process, the
Cauchy process, the stable-1/2 subordinator, the variance-gamma process, and the
normal inverse-Gaussian process. These are applied to the valuation of credit-risky
bonds, vanilla and exotic options, and non-life insurance liabilities
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