Power management for energy-aware communication systems

Abstract

System-level power management has become a key technique to render modern wireless communication devices economically viable. Despite their relatively large impact on the system energy consumption, power management for radios has been limited to shutdown-based schemes, while processors have benefited from superior techniques based on dynamic voltage scaling (DVS). However, similar scaling approaches that trade-off energy versus performance are also available for radios. To utilize these in radio power management, existing packet scheduling policies have to be thoroughly rethought to make them energy-aware, essentially opening a whole new set of challenges the same way the introduction of DVS did to CPU task scheduling. We use one specific scaling technique, dynamic modulation scaling (DMS), as a vehicle to outline these challenges, and to introduce the intricacies caused by the nonpreemptive nature of packet scheduling and the time-varying wireless channel.

Design exploration of energy-performance trade-offs for wireless sensor networks

“…In particular, detailed energy characterizations are available for hardware circuits, sensors and microcontrollers [8], memory banks [7], and radio circuits [9] [15]. However, these models do not consider any interdependency between the different parts of the system, hence they are not sufficient to describe the behavior of a set of networked nodes.…”

“…From a quantitative perspective, the application can be modeled as a function h that processes the input stream φin and produces a certain amount of results to be transmitted. As a consequence, the output of the node is equal to φout = h(φin, χ node ) and, if an estimation of the transmission errors is available (e.g., [9]), then the average amount of retransmitted data can be added to the original φout;…”

“…Finally, the output stream φout and the control information need to be transmitted to the coordinator by the radio unit during the assigned transmission intervals. The physical radio determines the transmission time in Equation (1) and the dissipation associated to the reception (Erx) and the transmission (Etx) of one bit, the latter being related to the power of the carrier signal [9], which must be chosen to achieve a low packet error rate. Thus, the energy consumption due to the radio can be expressed as:…”

On Energy-Aware Communication and Control Co-design in Wireless Networked Control Systems

“…Switching between these two types of modulation changes the number of bits sent in a period of time (the size of the constellation). Switching is in general performed via a scheduler [Schurgers et al, 2003] that selects the best modulation scheme as a function of the packet rate load. When the demand is low, the scheduler uses low-bit modulation scheme that uses less energy per period.…”

Throughput and value maximization in wireless packet scheduling under energy and time constraints

“…coding or modulation schemes, the energy for transmitting a given amount of data can be reduced substantially by lowering the transmission power and increasing the transmission time [5][6][7].…”