| Summary: | Energy is a critical resource in the design of wireless networks since wireless devices are
usually powered by batteries. Battery capacity is finite and the progress of battery technology
is very slow, with capacity expected to make little improvement in the near future.
Under these conditions, many techniques for conserving power have been proposed to increase
battery life.
In this dissertation we consider two approaches to conserving the energy consumed
by a wireless network interface. One technique is to use power saving mode, which allows
a node to power off its wireless network interface (or enter a doze state) to reduce energy
consumption. The other is to use a technique that suitably varies transmission power to
reduce energy consumption. These two techniques are closely related to theMAC (Medium
Access Control) layer.
With respect to power saving mode, we study IEEE 802.11 PSM (Power Saving Mechanism)
and propose a scheme that improves its energy efficiency. We also investigate the
interaction between power saving mode and TCP (Transport Control Protocol). As a second
approach to conserving energy, we investigate a simple power control protocol, called
BASIC, which uses the maximum transmission power for RTS-CTS and the minimum
necessary power for DATA-ACK. We identify the deficiency of BASIC, which increases
collisions and degrades network throughput, and propose a power control protocol that addresses
these problems and achieves energy savings. Since energy conservation is not an issue limited to one layer of the protocol stack, we study a cross layer design that combines
power control at the MAC layer and power aware routing at the network layer. One poweraware
routing metric is minimizing the aggregate transmission power on a path from source
to destination. This metric has been used along with BASIC-like power control under the
assumption that it can save energy, which we show to be false. Also, we show that the
power aware routing metric leads to a lower throughput. We show that using the shortest
number of hops in conjunction with BASIC-like power control conserves more energy than
power aware routing with BASIC-like power control.
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