Daniel Moss

Practical PACE for embedded systems

In current embedded systems, one of the major concerns is energy conservation. The dynamic voltage-scheduling (DVS) framework, which involves dynamically adjusting the voltage and frequency of the CPU, has become a well studied technique. It has been shown that if a tasks computational requirement is only known probabilistically, there is no constant optimal speed for the task and the expected energy consumption is minimized by gradually increasing speed as the task progresses citelorchsmith. It is possible to find the optimal speed schedule if we assume continuous speed and a well defined power function, which are assumptions that do not hold in practice. In this paper, we study the problem from a practical point of view, that is, we study the case of discrete speeds and make no restriction on the form of the power functions. Furthermore, we take into account processor idle power and speed change overhead, which were ignored in previous similar studies. We present a fully polynomial time approximation scheme (FPTAS), which has performance guarantees and usually obtains solutions very close to the optimal solution in practice. Our evaluation shows that our algorithm performs very well and generally obtains solutions within 0.1.

BLAM: an energy-aware MAC layer enhancement for wireless adhoc networks

In wireless adhoc networks, channel and energy capacities are scarce resources. However, the design of the IEEE 802.11 DCF protocol leads to an inefficient utilization of these resources. We introduce BLAM, a new battery level aware MAC protocol, which is developed from an energy-efficiency point of view to extend the useful lifetime of an adhoc network. We modify the IEEE 802.11 DCF protocol to enable BLAM to tune the random deferring time for fresh and collided data packets dynamically, based on the nodes energy. We show that BLAM can achieve an increase of 15% in network lifetime and an increase of about 35% in the total number of received packets.