Power efficient communications in low power ad hoc radio networks

In this thesis we investigate the feasibility of using information overheard by wireless devices to reduce their overall energy consumption for communications. Specifically we investigate the hypothesis “It is more efficient in terms of energy consumption to constrain the transmission power based upon a combination of received signal strength with a minimally extended MAC, than to utilise an unchanged MAC and full power.”. We investigate the hypothesis in the context of an ad hoc wireless network comprising of devices that use low power radio systems. We investigate two different low power radio systems, a standard 802.11 system and a custom low power radio device from Philips Research Labs. We examine in detail the energy consumption of the Philips’ low power radio device in its three modes of operation; transmission, reception and idle. From this, we propose a generic framework for power measurement and illustrate the technique with a case study. Specifically, this technique identifies the three modes in a trace of the energy consumption of the low power radio device, and uses this information to accurately extract the consumption figures for the different modes of operation. Using our measurements and the energy consumption parameters for an 802.11 radio device, we examine in simulation the complex behaviour that emerges from the implementation of an energy-aware system using a simple transmission power control algorithm that exploits overheard MAC-level information to reduce device’s energy consumption. We evaluate this simple algorithm using two radio systems and show that, in spite of the complexity, energy savings can be obtained using a scheme that takes advantage of overheard information. Copyright c © 2011 by Adam Greenhalgh All rights reserved.