Miguel Elias M. Campista

A Public Transportation Monitoring System Using IEEE 802.11 Networks

One major challenge today is to deal with the traffic jams related to excessive use of vehicles. It is believed that more people would adopt public transportation if these were more reliable. Thus, this paper proposes WiBus, which is a system to estimate buses times of arrival, based on information from opportunistic contacts in IEEE 802.11 networks. Estimates are provided to users through graphical interfaces of mobile devices. WiBus adjusts bus trajectories with an algorithm for dynamic creation and maintenance. The system was implemented and its performance was analyzed via emulation of a real scenario. Experimental results show that WiBus can meet demands of large cities with accumulated error on the order of a few minutes in the worst case.

Geo-Distributed Data Centers: Distance and Robustness Trade-Offs

Geo-distributed data centers present a better robustness to failures than monolithic ones, since they have less single points of failure. In this work we tackle the trade-off between robustness and latency caused by the distance between DC sites in geo-distributed data centers. This trade-off is addressed through the formulation of an optimization problem. The results show that the distance between DC sites increases significantly the latency only in case of very strong robustness requirements. On the other hand, the latency increase by the distance is negligible for moderate robustness requirements.