<p>Wireless Sensor Networks (WSN) differ from traditional wireless communication networks in several characteristics. One of these characteristics is power awarness, due to the fact that the batteries of sensor nodes have a restricted lifetime and are difficult to be replaced. Therefore, all protocols must be designed to minimize energy consumption and preserve the longevity of the network. In this paper, we propose (i) to fairly balance the load among nodes. For this, we generate an unequal clusters size where the cluster heads (CH) election is based on energy availability, (ii) to reduce the energy consumption due to the transmission by using multiple metrics in the CH jointure process and taking into account the link cost, residual energy and number of cluster members to construct the routing tree and (iii) to minimize the number of transmissions by avoiding the unnecessary updates using sensitive data controller. Simulation results show that our Advanced Energy-Efficient Unequal Clustering (AEEUC) mechanism improves the fairness energy consumption among all sensor nodes and achieves an obvious improvement on the network lifetime.</p>
Scheduling transactions in real-time database systems (RTDBSs) is more complex than scheduling tasks in real-time systems. In fact, the RTDBS must guarantee the database logical consistency, on one hand, and it must schedule the transactions in order to meet their deadlines, on the other hand. The main policy used to schedule transactions in RTDBSs is Earliest Deadline First (EDF). However, it is well-known that EDF is not efficient for scheduling transactions in overload conditions. Consequently, different scheduling protocols: AED, AEVD, APP, AEDF-Co, GEDF... were proposed to improve the system performances in firm RTDBSs, i.e. late transactions are considered useless. Generalized Earliest Deadline First (GEDF) is a new scheduling protocol in which transaction priority is assigned according to both deadlines and a parameter, called SPriority, which expresses the importance of transactions. In this paper, an RTDBSs analysis is presented. The accuracy of GEDF scheduling policy and the influence of database workload on the system performances is investigated. This study enabled us to describe the complete behavior of the transaction success ratio. Moreover, based on intensive simulations, we have derived the optimal values of the system parameters which improve the success ratio without modifying GEDF protocol.
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