Minimizing Flag-Collision Probability in Timer-Based Opportunistic Relaying

In opportunistic relaying systems, a single relay among the available relays is used for cooperation between the source and the destination. The best relay is selected and this is revealed using a distributed timerbased method that was proposed few years ago. The main technical challenge in the implementation of the timerbased method is the possibility of flag-packet collision of more than one relay such that the identification of the best relay fails. In this paper, we propose a modification to the original timer-based method that is known in the literature. In particular, we use a discrete timer and we provide a simple algorithm to optimize the timer mapping function based on the channel statistics and the number of relays in the network in order to minimize the flag packets collision probability.We demonstrate by numerical results that our proposed timer can reduce the collision probability by more than an order of magnitude.