Abstract
Wireless sensor networks (WSN) that are powered by energy harvested from the environment, also known as rechargeable WSNs, typically experience wide variations of energy availability across the network. Such variations can cause frequent node outages at specific locations where energy availability is low, whereas the remaining nodes may receive sufficient energy for continuous operation. The energy availability also varies over time due to environmental factors, which exacerbates the problem. To minimize the impact of such spatial and temporal variations of energy resources, we propose a joint Power COntrol and Routing scheme (PCOR) that adapts the energy consumption in the sensor nodes according to its available energy resources in order to facilitate uninterrupted operations. The scheme is applied to data collecting WSNs with a MAC that utilizes asynchronous duty-cycling for energy conservation. PCOR achieves its objective by reducing the energy consumption at energy-critical sensor nodes, i.e. nodes that have comparatively lower energy resources, using network-wide cooperative power control and route adaptations. This is accomplished by reducing the overhearing at energy-critical nodes, which is a key cause of energy consumption in such networks. We demonstrate through simulations and experimental results that PCOR reduces overhearing at energy-constrained nodes by up to 75% without significantly affecting the end–to–end packet delivery rates.
Highlights
Energy harvesting from environmental resources is a popular approach for achieving long term sustainability in wireless sensor networks (WSN)
The existing literature on energy management exploits the benefits of power adaptation by dropping the power levels of a transmitter so that the signal strength at the receiver is just above the receiver sensitivity. While this helps in reducing the energy consumption in high power wireless transmitters such as cellular and ad hoc networks, in low-power radios such as those used in WSNs, it does not lead to proportional reduction in power consumption of the transmitter
PREDICTION MODEL FOR POWER CONTROL Since the link quality between a pair of nodes largely depends on the transmit power level of the transmitter, we develop a receiver-based prediction model to correlate the transmit power level at the transmitter and forward link quality at the receiver
Summary
Energy harvesting from environmental resources is a popular approach for achieving long term sustainability in wireless sensor networks (WSN). Several mechanisms have been proposed to reduce the energy wasted from overhearing, which include interruption of unnecessary receptions based on information transmitted in the preamble [13], adaptive duty-cycling [14], [15] and others. We propose a mechanism to achieve controlled reduction of overhearing at severely energy-constrained nodes to reduce their energy consumption by using cooperative transmission power control as well as through network-wide route adaptations. One of its neighbors (marked in blue) applies transmit power control and route adaptation in order to avoid causing overhearing to the red node. PCOR utilizes a routing metric that combines link quality with additional parameters to capture the overhearing effects caused by the transmissions of the candidate routes that pass through the energy-critical nodes.
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