MobiHoc '01 Proceedings of the 2nd ACM international symposium on Mobile ad hoc networking & computing
Wireless sensor networks: a new regime for time synchronization
ACM SIGCOMM Computer Communication Review
Power management for energy-aware communication systems
ACM Transactions on Embedded Computing Systems (TECS)
Versatile low power media access for wireless sensor networks
SenSys '04 Proceedings of the 2nd international conference on Embedded networked sensor systems
Simulating the power consumption of large-scale sensor network applications
SenSys '04 Proceedings of the 2nd international conference on Embedded networked sensor systems
Node-level energy management for sensor networks in the presence of multiple applications
Wireless Networks - Special issue: Pervasive computing and communications
Near-Optimal Radio Use for Wireless Network Synchronization
Algorithmic Aspects of Wireless Sensor Networks
Temporal partition in sensor networks
SSS'07 Proceedings of the 9h international conference on Stabilization, safety, and security of distributed systems
Clock synchronization for wireless networks
OPODIS'04 Proceedings of the 8th international conference on Principles of Distributed Systems
Near-optimal radio use for wireless network synchronization
Theoretical Computer Science
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We consider the problem of clock synchronization in a wireless setting where processors must minimize the number of times their radios are used, in order to save energy. Energy efficiency is a central goal in wireless networks, especially if energy resources are severely limited, as occurs in sensor and ad-hoc networks, and in many other settings. The problem of clock synchronization is fundamental and intensively studied in the field of distributed algorithms. In the current setting, the problem is to synchronize clocks of m processors that wake up in arbitrary time points, such that the maximum difference between wake up times is bounded by a positive integer n. (Time intervals are appropriately discretized to allow communication of all processors that are awake in the same discrete time unit.) Currently, the best-known results for synchronization for single-hop networks of m processors is a randomized algorithm due to Bradonjic, Kohler and Ostrovsky [2] of O(√n/m ċ poly-log(n)) radio-use times per processor, and a lower bound of Ω(√n/m). The main open question left in their work is to close the poly-log gap between the upper and the lower bound and to de-randomize their probabilistic construction and eliminate error probability. This is exactly what we do in this paper. That is, we show a deterministic algorithm with radio use of Θ(√n/m), which exactly matches the lower bound proven in [2], up to a small multiplicative constant. Therefore, our algorithm is optimal in terms of energy efficiency and completely resolves a long sequence of works in this area [2, 11-14]. Moreover, our algorithm is optimal in terms of running time as well. In order to achieve these results we devise a novel adaptive technique that determines the times when devices power their radios on and off. This technique may be of independent interest. In addition, we prove several lower bounds on the energy efficiency of algorithms for multi-hop networks. Specifically, we show that any algorithm for multi-hop networks must have radio use of Ω(√n) per processor. Our lower bounds holds even for specific kinds of networks such as networks modeled by unit disk graphs and highly connected graphs.