Optimizing Transmission and Shutdown for Energy-Efficient Real-time Packet Scheduling in Clustered Ad Hoc Networks
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Optimizing Transmission and Shutdown for Energy-Efficient Real-time Packet Scheduling in Clustered Ad Hoc Networks Sofie Pollin,1,2 Bruno Bougard,1,2 Rahul Mangharam,1,3 Francky Catthoor,1,2 Ingrid Moerman,1,4 Ragunathan Rajkumar,3 and Liesbet Van der Perre1 1 Wireless
Research, IMEC, 3001 Leuven, Belgium Emails: [email protected], [email protected], [email protected], [email protected]
2 ESAT/INSYS,
Katholieke Universiteit Leuven, 3001 Leuven, Belgium
3 Real-Time
& Multimedia Systems Laboratory, Carnegie Mellon University, Pittsburgh, PA 15213, USA Emails: [email protected], [email protected]
4 INTEC,
Universiteit Gent, 9000 Gent, Belgium Email: [email protected]
Received 30 June 2004; Revised 22 March 2005 Energy efficiency is imperative to enable the deployment of ad hoc networks. Conventional power management focuses independently on the physical or MAC layer and approaches differ depending on the abstraction level. At the physical layer, the fundamental tradeoff between transmission rate and energy is exploited, which leads to transmit as slow as possible. At MAC level, power reduction techniques aim to transmit as fast as possible to maximize the radios power-off interval. The two approaches seem conflicting and it is not obvious which one is the most appropriate. We propose a transmission strategy that optimally mixes both techniques in a multiuser context. We present a cross-layer solution considering the transceiver power characteristics, the varying system load, and the dynamic channel constraints. Based on this, we derive a low-complexity online scheduling algorithm. Results considering an M-ary quadrature amplitude modulation radio show that for a range of scenarios a large power reduction is achieved, compared to the case where only scaling or shutdown is considered. Keywords and phrases: clustered ad hoc networks, energy efficiency, lazy scheduling, shutdown, schedule-based MAC.
1.
INTRODUCTION
Ad hoc wireless networks consist of a group of autonomous mobile nodes configuring themselves to form a network that is adapted to the environment and the current needs. A broad range of applications is possible, going from low-rate sensor monitoring applications [1] to high-rate multimedia applications [2]. Both monitoring and multimedia applications are delay sensitive and an appropriate QoS architecture is needed to take care of this in dynamic environments. On the other hand, ad hoc networks are severely constrained in terms of energy. Wireless communication allows untethered operation, which implies the need for batteryThis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
powered devices. Due to the slow advances in battery technology compared to the growth in system power requirements [3], the use of ad hoc networks is limited by short battery lifetimes. It has already been shown in several design cases [4, 5] that the most critical energy
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