On the Scalability of Cooperative Time Synchronization in   Pulse-Connected Networks
  The problem of time synchronization in dense wireless networks is considered. Well established synchronization techniques suffer from an inherent scalability problem in that synchronization errors grow with an increasing number of hops across the network. In this work, a model for communication in wireless networks is first developed, and then the model is used to define a new time synchronization mechanism. A salient feature of the proposed method is that, in the regime of asymptotically dense networks, it can average out all random errors and maintain global synchronization in the sense that all nodes in the multi-hop network can see identical timing signals. This is irrespective of the distance separating any two nodes. 
An-swol Hu and Sergio D. Servetto (Cornell University)