Tools for the selection of the transmission probability in the cluster formation phase for event-driven wireless sensor networks

In the literature, it is common to find studies on Wireless Sensor Networks (WSNs) that consider the Carrier Sense Multiple Access (CSMA) protocol with a fixed transmission probability for means of the random access strategy. This is especially true for event-driven applications for clusteredbased architectures. However, due to the highly variable environment in these networks in terms of the number of nodes attempting a transmission (at the beginning of the cluster formation all nodes in the network contend for the channel, while at the end only a few nodes attempt a transmission), a fixed transmission probability may not entail an adequate performance. Specifically, the energy consumption may be too high by considering a fixed transmission strategy, because the use of a low transmission probability at the beginning of the cluster formation reduces the collision probability, but at the end entails long idle periods. In view of this, the effects of three different transmission probability strategies for event-driven WSNs are studied. Based on the obtained results, it is shown that a careful selection of the transmission probability is required in order to prolong the network lifetime.