This chapter gives a summary of the topics that have been discussed in this book. Precisely, it summarizes the contributions that we made in the areas of
-coverage, connectivity, duty-cycling, and geographic forwarding in two-and three-dimensional wireless sensor networks. All the proposed protocols are energy-efficient with a goal to minimize the total energy consumption of the sensors, thus extending their lifetime. Then, it presents our future research work in an attempt to solve some (open) problems more efficiently.