On the estimation of the jump activity index in the case of random observation times

Abstract
We propose a nonparametric estimator of the jump activity index of a pure-jump semimartingale driven by a -stable process when the underlying observations are coming from a high-frequency setting at irregular times. The proposed estimator is based on an empirical characteristic function using rescaled increments of , with a limit which depends in a complicated way on and the distribution of the sampling scheme. Utilising an asymptotic expansion we derive a consistent estimator for and prove an associated central limit theorem.
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