Date Added: Sep 2009
Timer-based mechanisms are often used to help a given (sink) node select the best helper node among many available nodes. Specifically, a node transmits a packet when its timer expires, and the timer value is a monotone non-increasing function of its local suitability metric. The best node is selected successfully if no other node's timer expires within a 'Vulnerability' window after its timer expiry, and so long as the sink can hear the available nodes. In this paper, the authors show that the optimal metric-to-timer mapping that maximizes the probability of success or minimizes the average selection time subject to a minimum constraint on the probability of success, maps the metric into a set of discrete timer values.