Research On Energy Conservation And Reliability In Wireless Sensor Network

Sensor networks provide applications in many diverse areas. This is for the simplefact that they are reliable, flexible, easily deployable and highly cost-effective.Motivated by their tremendous potentials in civil and military applications, wirelesssensor networks have raised tremendous research interests in recent years.Thefundamental function of wireless sensor networks is the gathering of information from acovered area. To achieve exibility in deployment, sensor nodes are generallybattery-driven. Furthermore,battery replacement is very diffcult, if at all possible, due tothe random deployment nature of wireless sensor networks. Thus, sensor nodes havelimited operational time and the operational time of the sensor networks is alsolimited.Hence, energy efficiency is another fundamental challenge in wireless sensornetworks. To improve the performance of wireless sensor networks, data delivery shouldbe both energy efficient and effective, which is the focus of this thesis.First, we observe the conflict of the two objectives viz, the application performanceand the network lifetime-when optimizing the performance of wireless sensor networks.We find that the tradeoff between them can be studied by investigating the interactionbetween the network lifetime maximization problem and the rate allocation problem.Then, we formulate the tradeoff problem as a constrained convex optimization problemby introducing a tradeoff factor. We first tackle this problem at the transport layer, andthen from a cross layer perspective. Using Lagrange dual decomposition, algorithms areobtained to achieve the best tradeoff. Last,take note that energy conservation techniquesfor wireless sensor networks generally assume that data acquisition and processing haveenergy consumption that is significantly lower than that of communication.Unfortunately, this assumption does not always hold, proposed an adaptive samplingalgorithm that estimates online the optimal sampling frequencies for sensors. Comparedwith traditional method it can perform similar to a fixed-rate scheme where the samplingfrequency is known decreased,hence save the energy.