Energy Efficiency and Routing in Sensor Networks

Wireless sensor networks (WSNs) consist of tiny devices, which have a
battery, a sensor, a microprocessor and a radio transmitter component.
Due to a large range of application area, performance metrics in sensor
network are strictly application-specic. However, 'unattended operation
of the network for long time' or 'long network lifetime' can be determined
as a common performance requirement for the most of the applications.
Energy depletion of the nodes can interrupt communication and, in a worse
case, it could cause network partitioning which leads the interruption of
monitoring. Unlike ad-hoc networks, recharging or replacing of the sen-
sors battery may be inconvenient, or even impossible in some monitoring
environments. Therefore, the key challenge in the design of wireless sen-
sor network protocols is how to maximize the network lifetime, which is
limited by battery energy in sensor nodes, while providing the application
requirement.
In sensor networks, there are two important energy consuming pro-
cesses, the rst is transmission-reception phase and the second is listening
the radio for any possible event. Therefore, there are two strategies for en-
ergy saving. The rst is reducing the networking activities, which means less packet exchanging between the nodes or balanced load allocation.
The second is avoiding the idle waiting time for packet arrivals. The rst
strategy covers routing techniques for resource constraints networks and
the second covers duty-cycling techniques.
In this thesis, rstly mathematical characterization of networking in
sensor network is studied by considering network dynamics and duty cy-
cling of sensor nodes. Then energy eciency techniques in sensor network
are investigated. Secondly, a mathematical tool in which maximum life-
time routing can be investigated for dierent network parameters is de-
veloped by considering a duty-cycling mechanism in the network. Upper
bound on network lifetime is sought by considering idle and sleep mode
energy consumption as well as energy consumption in transmission and
reception for sensor networks. The solution of the developed optimization
problems gives an analytical benchmark for designing of maximum lifetime
routing algorithms by giving the most energy balanced trac allocation
between the possible routes in the network by considering a duty-cycling
mechanism. Lastly, an energy ecient routing protocol is proposed and
evaluated by using the developed mathematical tool.