On the retransmission methods in wireless sensor networks

A very limited energy budget represents the most critical aspect of wireless sensor networks. Typical applications need long lifetime networks, but usually replacing batteries is not practical. Therefore, it is necessary to design all network levels and protocols carefully to save energy. The paper investigates the link layer, with the proposition of four information delivery mechanisms, and studies their energy consumptions. Comparisons between the different proposed methods are realized in two situations: by referring to an actual sensor node, μAMPS-1, and by developing a more generic parametric model. With μAMPS-1 data, we can obtain an energy gain ranging from 5% to 15%, by using intermediate nodes as digital repeaters and decoding operations performed only at the destination instead of a hop-to-hop decoding solution. The performance depends on several parameters, e.g., the hardware technology, the source-to-destination distance, the number of hops involved; we emphasize in particular the necessity to distribute packet forwarding among an optimal number of intermediate hops.