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Abstract-Vehicular Ad Hoc Networks are networks characterized by intermittent connectivity and rapid changes in their topology. This paper addresses car-to-road communications in which vehicles use Access Points (AP) in a Delay Tolerant Network architecture. Results show how the combination of a Delay-Cooperative ARQ mechanism reduces packet losses and in conjunction with a Carry-and-Forward cooperative mechanism improves performance parameters in terms of total file transfer delay and number of AP needed to download files.

In this paper we analyse a multiplexer handling a number of identical and independent Worst Case Traffic (WCT) sources. Each WeT source produces a periodic stream of cells consisting of a constant number of back-to-back cells followed by a silent period of constant duration. The WeT can model the traffic produced by a "malicious" user who sends an ON/OFF traffic where a burst of back-to-back cells whose length is the largest compatible with the tolerance introduced in the control function alternates with an idle period whose length is the smallest compatible with the policed peak cell rate. WeT can also model, for example, the traffic produced by some ATM Adaptation Layer multiplexing schemes in the Terminal Equipment.Exact results are obtained, both for the discrete and the fluid-flow model. The numerical examples show the dramatic impact that WeT can have on the multiplexer buffer requeriments. The model presented can be useful to assess the convenience of using a traffic shaping device at the entry point of the ATM network.

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In this paper we study tree networks of discrete-time queues loaded with periodic traffic sources. By using the so-called Beneš method, exact closed-form expressions are obtained for the queue length distributions. The models developed can be used to study the superposition of periodic sources emitting bursts of cells in ATM networks. The results obtained show the significant effect that this kind of traffic can have on the performance of these systems.

We obtain the queue length distribution in a tree of discrete time queues with constant service time whose input is periodic traffic. In the context of ATM the study could be applied to CBR sources. The tree consists of Mstages. To solve this system, we first solve a 2-stage tree network. Given this configuration, a more complex tree network can be easily solved making use of the properties of the discrete time queues with identical service times. We also give closed formulas for the average waiting time and average number of cells in any queue of the tree network.