The Myth of Power Control in Routing

Energy management remains a critical problem in ad hoc networks since battery technology cannot keep up with rising expectations in wireless communications. Current approaches to energy conservation focus on reducing the energy consumption of the wireless interface either for a given communication task or during idling. However, these communication-time and idle-time approaches are not necessarily complementary. Therefore, we explore the interactions between the two approaches and their impact on the design of a complete solution to energy conservation. Essentially, a complete solution requires minimizing the energy spent in communication (i.e., for data and control overhead) and in idling while satisfying communication needs. This problem can be expressed as an energy-efficient network design problem, which is, not surprisingly, NP-hard. Therefore, we study several heuristic approaches. Our study shows that minimizing energy consumed in data transmissions as a primary goal does not save energy. Furthermore, jointly reducing energy consumed for both data and in idling becomes cost-prohibitive when the energy spent in control overhead is considered. Hence, we propose a two-stage approach that prioritizes idling energy consumption over energy spent for data transmissions. Due to its low control overhead, this two-stage approach provides an effective way to meet the challenge of operating the network with low energy cost.