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Vivek Borkar

Publications and source records attributed to Vivek Borkar.

20 records · Page 2Linked to original sources

Model-based clock synchronization protocol for wireless sensor networks

In a wireless sensor network, nodes communicate time-stamped packets in order to synchronize their clocks, i.e., estimate each other's time display. We introduce and analyze a parametrized stochastic model for clocks and use it to calculate, at any given time, the Maximum-Likelihood (ML) estimate of the relative skew/offset between two communicating nodes. For network synchronization, event-based Kalman-Bucy filtering gives rise to a centralized scheme, and we propose an efficient distributed suboptimal algorithm. We study the performance both analytically and experimentally and provide provable guarantees. We summarize our findings into defining a new distributed model-based clock synchronization protocol (MBCSP), and present a comparative simulation study of its accuracy versus prior art to showcase improvements.

cs.NI↗

Quasi-stationary distributions as centrality measures of reducible graphs

Random walk can be used as a centrality measure of a directed graph. However, if the graph is reducible the random walk will be absorbed in some subset of nodes and will never visit the rest of the graph. In Google PageRank the problem was solved by introduction of uniform random jumps with some probability. Up to the present, there is no clear criterion for the choice this parameter. We propose to use parameter-free centrality measure which is based on the notion of quasi-stationary distribution. Specifically we suggest four quasi-stationary based centrality measures, analyze them and conclude that they produce approximately the same ranking. The new centrality measures can be applied in spam detection to detect ``link farms'' and in image search to find photo albums.

cs.NI↗