Cross-layer scheduling for power efficiency in wireless sensor networks

Wireless sensor networks are considered the sensing technology of the future. Large numbers of untethered sensor nodes can he used for tracking small animals and targets, environmental monitoring, enforcing security perimeters, etc. A major problem for many sensor network applications is determining the most efficient way of conserving the energy of the power source. Some networks use batteries, while others suggest different methods of gathering energy (e.g., solar cells). Regardless of the powering method, energy conservation is of prime importance for sensor networks. The best way to conserve energy is to turn the sensor nodes off; however, since an inactive sensor node is no longer part of the network, the network can become disconnected. This creates a fundamental trade-off. In this paper, we propose a deterministic, schedule-based energy conservation scheme. In the proposed approach, time-synchronized sensors form on-off schedules that enable the sensors to be awake only when necessary. The schedule establishment is fully distributed and thus appropriate for large sensor networks. The performance of the proposed approach is evaluated through the use of simulations.