56,985 research outputs found
Modelling Probabilistic Wireless Networks
We propose a process calculus to model high level wireless systems, where the
topology of a network is described by a digraph. The calculus enjoys features
which are proper of wireless networks, namely broadcast communication and
probabilistic behaviour. We first focus on the problem of composing wireless
networks, then we present a compositional theory based on a probabilistic
generalisation of the well known may-testing and must-testing pre- orders.
Also, we define an extensional semantics for our calculus, which will be used
to define both simulation and deadlock simulation preorders for wireless
networks. We prove that our simulation preorder is sound with respect to the
may-testing preorder; similarly, the deadlock simulation pre- order is sound
with respect to the must-testing preorder, for a large class of networks. We
also provide a counterexample showing that completeness of the simulation
preorder, with respect to the may testing one, does not hold. We conclude the
paper with an application of our theory to probabilistic routing protocols
Probabilistic conformance testing of protocols with unobservable transitions
A probabilistic approach to conformance testing of protocols containing unobservable transitions is proposed. It is said that an implementation conforms to its specification if their observable behavior is probabilistically the same, when both are subject to the same random environment simulated by the tester. Under the randomized inputs, faults in unobservable transitions may manifest themselves in certain statistics measurable from the implementation, and hence can be detected by comparing these measurements against the desirable statistics computed from the specification. The sensitivity of the nonconformance criterion to the uncertainty in our knowledge of desirable statistics is also studied. The conventional testing of protocols without unobservable transitions uses mismatch in outputs to detect faults. Here, one relies, in addition, on mismatch in the dynamics of the protocol under input randomization
Probabilistic communication complexity over the reals
Deterministic and probabilistic communication protocols are introduced in
which parties can exchange the values of polynomials (rather than bits in the
usual setting). It is established a sharp lower bound on the communication
complexity of recognizing the -dimensional orthant, on the other hand the
probabilistic communication complexity of its recognizing does not exceed 4. A
polyhedron and a union of hyperplanes are constructed in \RR^{2n} for which a
lower bound on the probabilistic communication complexity of recognizing
each is proved. As a consequence this bound holds also for the EMPTINESS and
the KNAPSACK problems
Formal analysis techniques for gossiping protocols
We give a survey of formal verification techniques that can be used to corroborate existing experimental results for gossiping protocols in a rigorous manner. We present properties of interest for gossiping protocols and discuss how various formal evaluation techniques can be employed to predict them
Ioco theory for probabilistic automata
Model-based testing (MBT) is a well-known technology, which allows for automatic test case generation, execution and evaluation. To test non-functional properties, a number of test MBT frameworks have been developed to test systems with real-time, continuous behaviour, symbolic data and quantitative system aspects. Notably, a lot of these frameworks are based on Tretmans' classical input/output conformance (ioco) framework. However, a model-based test theory handling probabilistic behaviour does not exist yet. Probability plays a role in many different systems: unreliable communication channels, randomized algorithms and communication protocols, service level agreements pinning down up-time percentages, etc. Therefore, a probabilistic test theory is of great practical importance. We present the ingredients for a probabilistic variant of ioco and define the {\pi}oco relation, show that it conservatively extends ioco and define the concepts of test case, execution and evaluation
Making Random Choices Invisible to the Scheduler
When dealing with process calculi and automata which express both
nondeterministic and probabilistic behavior, it is customary to introduce the
notion of scheduler to solve the nondeterminism. It has been observed that for
certain applications, notably those in security, the scheduler needs to be
restricted so not to reveal the outcome of the protocol's random choices, or
otherwise the model of adversary would be too strong even for ``obviously
correct'' protocols. We propose a process-algebraic framework in which the
control on the scheduler can be specified in syntactic terms, and we show how
to apply it to solve the problem mentioned above. We also consider the
definition of (probabilistic) may and must preorders, and we show that they are
precongruences with respect to the restricted schedulers. Furthermore, we show
that all the operators of the language, except replication, distribute over
probabilistic summation, which is a useful property for verification
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