Relay node insertion in sparse time-driven wireless sensor networks

Usually wireless sensor network scenarios consist of relatively small areas where nodes are random and densely deployed. However, this is not always the case, as it happens with many time-driven applications, where nodes are either located at strategic positions or arranged according to some regular sampling patterns. In either case, the resulting inter-node distances may not be small. Thus, in order to overcome the significant energy costs of long communication ranges, or simply their unfeasibility, the introduction of additional resources becomes necessary. In this paper, the technique that consists of inserting relay nodes in critical links is analyzed in detail. The analysis considers the most general scenario of heterogeneous sampling rates, and does not only focus on lifetime, but also on performance metrics such as network delay, packet loss rate and reliability.