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A schedule-based approach, such as time division multiple access, is more efficient than a contention-based approach in terms of energy saving by switching sensors into sleeping mode. However, it does not use the transmission media effectively as each time slot is dedicated to a sensor and therefore cannot be used by others should it be idle. Moreover, a schedule-based approach requires a central node to manage and broadcast the schedule to other members, causing high delay and unscalability. On the other hand, contention-based protocols can be used in a distributed fashion. However, contention-based protocols such as IEEE 802.11 waste a lot of energy in idle listening. In this paper, we propose a hybrid approach between contention- and schedule-based protocols. The preliminary results using simulation and a test bed show that our proposed approach uses transmission media more efficiently, leading to lower delay while preserving energy for wireless sensor networks.