This paper proposes an energy-effcientand collision-free medium access control protocol namedTDMA-S (Time division multiple access MAC protocolfor Sensor networks). Nodes in TDMA-S schedule theirtransmissions based on neighborhood information to determine when they can transmit, listen or sleep. TDMA-Scollects the neighborhood information using a distributedalgorithm and avoids that two nodes within the interference range are assigned the same transmitting slot. Theprotocol is shown to be fair and reliable. Simulation results indicate that TDMA-S outperforms contention-basedprotocol (e:g., S-MAC) and schedule-based protocol (e:g.,NAMA) in terms of delay and energy consumption.