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Dynamic Tree Algorithms

Abstract : In this paper, a general tree algorithm processing a random flow of arrivals is analyzed. Capetanakis-Tsybakov-Mikhailov's protocol in the context of communication networks with random access is an example of such an algorithm. In computer science, this corresponds to a trie structure with a dynamic input. Mathematically, it is related to a stopped branching process with exogeneous arrivals (immigration). Under quite general assumptions on the distribution of the number of arrivals and on the branching procedure, it is shown that there exists a {\em positive} constant $\lambda_c$ so that if the arrival rate is smaller than $\lambda_c$, then the algorithm is stable under the flow of requests, i.e. that the total size of an associated tree is integrable. At the same time a gap in the earlier proofs of stability of the literature is fixed. When the arrivals are Poisson, an explicit characterization of $\lambda_c$ is given. Under the stability condition, the asymptotic behavior of the average size of a tree starting with a large number of individuals is analyzed. The results are obtained with the help of a probabilistic rewriting of the functional equations describing the dynamic of the system. The proofs use extensively this stochastic background throughout the paper. In this analysis, two basic limit theorems play a key role: the renewal theorem and the convergence to equilibrium of an auto-regressive process with moving average.
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Contributor : Philippe Robert Connect in order to contact the contributor
Submitted on : Sunday, September 21, 2008 - 11:03:52 AM
Last modification on : Friday, January 21, 2022 - 3:16:14 AM
Long-term archiving on: : Friday, June 4, 2010 - 11:38:49 AM


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  • HAL Id : inria-00323350, version 1
  • ARXIV : 0809.3577



Hanene Mohamed, Philippe Robert. Dynamic Tree Algorithms. 2008. ⟨inria-00323350⟩



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