Deterministic and Energy-Optimal Wireless Synchronization (original) (raw)

2011, Lecture Notes in Computer Science

We consider the problem of clock synchronization in a wireless setting where processors must powerdown their radios in order to save energy. In this setting, each processor has a radio device that is either on or off. When the radio device of a processor is on, it is able to communicate with other processors in its range. However, turning the radio on results in a significant waste of energy, even when listening. Energy efficiency is a central goal in wireless networks, especially if energy resources are severely limited. This is indeed the case in sensor networks, ad-hoc networks, and many other wireless network settings. Consequently, the main goal of multiple papers in wireless and sensor networks literature aims at achieving clock synchronization in an energy-efficient manner. In other words, the goal is to synchronize all clocks while minimizing the number of times a processor must switch its radio on. The problem of clock synchronization is an important problem 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, where time intervals are appropriately discretized to allow communication of all processors that are awake in the same discrete time unit. (We remark that in this model we do not consider the issue of Broadcast Interference, which is a different problem known as radio broadcast problem.) The current model received a wide attention in sensor network literature. 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 • poly-log(n) awake times per processor and a lower bound of