Distributed sleep-scheduling protocols for energy conservation in wireless networks

Wireless ad hoc networks are constrained by their battery power. An important design issue, thus, is to increase the network longevity. In this thesis, we present a distributed sleep scheduling protocol that can be used for implementing synchronous interface sleep for energy conservation in wireless ad hoc networks. The central idea of this protocol is to distribute a common sleep-awake cycle schedule among all nodes within a connected partition so that the nodes can turn their interface off during the sleep section of the agreed upon schedule, and they can communicate during the wake section of the schedule. By turning the interface off, the nodes can avoid idle listening consumption, which is a known reason for non-essential energy drainage in random-access network interfaces such as those running IEEE 802.11. Since the energy saving is achieved by synchronous interface sleeping, which reduces the active communication time, this protocol is suited for low to moderate network loading conditions. This distributed sleep-awake cycle scheduling and its associated long-term (100s of msec) synchronous sleep can be used as a complementary mechanism to those employed for short term (few msec) energy-saving asynchronous sleep for 802.11 MAC. In the latter, a node's interface is forced to sleep when ongoing transmissions, not involving this node, are detected in the neighborhood. While the short-term sleep is less effective at low loads, our mechanism works particularly well for low to moderate loading conditions. We present an ns2 based simulation model of the proposed distributed scheduling and sleep protocols for evaluating and comparing their energy performance with those of plain 802.11 MAC and a centralized scheduling mechanism.