A Palm calculus approach to functional versions of Little's law

Using the generalized Campbell theorem, a functional (distributional) version of Little's law is obtained for general FIFO systems with non-anticipating arrivals. Our approach generalizes existing results and, in particular, points out the intimate relation between the Palm-Khintchine equations and the distributional law of Little. A multidimensional version of the Palm-Khintchine equations and the related version of Little's law for multiclass systems is also given, as well as an ordinal version for distributions.