We study the problem of energy-balanced data propagation in wireless sensor networks. The energy balance property guarantees that the average per sensor energy dissipation is the same for all sensors in the network, during the entire execution of the data propagation protocol. This property is important since it prolongs the network's lifetime by avoiding early energy depletion of sensors.We propose a new algorithm that in each step decides whether to propagate data one-hop towards the final destination (the sink), or to send data directly to the sink. This randomized choice balances the (cheap) onehop transimssions with the direct transimissions to the sink, which are more expensive but "bypass" the sensors lying close to the sink. Note that, in most protocols, these close to the sink sensors tend to be overused and die out early.By a detailed analysis we precisely estimate the probabilities for each propagation choice in order to guarantee energy balance. The needed estimation can easily be performed by current sensors using simple to obtain information. Under * some assumptions, we also derive a closed form for these probabilities.The fact (shown by our analysis) that direct (expensive) transmissions to the sink are needed only rarely, shows that our protocol, besides energy-balanced, is also energy efficient.

Abstract. We consider the problem of data propagation in wireless sensor networks and revisit the family of mixed strategy routing schemes. We show that maximizing the lifespan, balancing the energy among individual sensors and maximizing the message flow in the network are equivalent. We propose a distributed and adaptive data propagation algorithm for balancing the energy among sensors in the network. The mixed routing algorithm we propose allows each sensor node to either send a message to one of its immediate neighbors, or to send it directly to the base station, the decision being based on a potential function depending on its remaining energy. By considering a simple model of the network and using a linear programming description of the message flow, we prove the strong result that an energy-balanced mixed strategy beats every other possible routing strategy in terms of lifespan maximization. Moreover, we provide sufficient conditions for ensuring the dynamic stability of the algorithm. The algorithm is inspired by the gradient-based routing scheme but by allowing to send messages directly to the base station we improve considerably the lifespan of the network. As a matter of fact, we show experimentally that our algorithm is close to optimal and that it even beats the best centralized multi-hop routing strategy.

We propose an algorithm which produces a randomized strategy reaching optimal data propagation in wireless sensor networks (WSN). In [6] and [8], an energy balanced solution is sought using an approximation algorithm. Our algorithm improves by (a) when an energy-balanced solution does not exist, it still finds an optimal solution (whereas previous algorithms did not consider this case and provide no useful solution) (b) instead of being an approximation algorithm, it finds the exact solution in one pass. We also provide a rigorous proof of the optimality of our solution.

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