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...tted to that node. Idle listening has been found in 802.11 protocols to consume substantial energy [8, 15], and therefore must be avoided in WSNs. Synchronized protocols, such as S-MAC [17] and T-MAC =-=[16]-=-, negotiate a schedule that specifies when nodes are awake and asleep within a frame. Specifying the time when nodes must be awake in order to communicate reduces the time and energy wasted in idle li...

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...nization frequency based on its current data rate and resource budget. In what follows, we describe the design, implementation and performance of Z-MAC in detail. II. RELATED WORK S-MAC [4] and T-MAC =-=[8]-=- are a hybrid of CSMA and TDMA in that they also maintain the synchronized time slots, but unlike TDMA their slots can be much bigger than normal TDMA slots and synchronization failures do not necessa...

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...division multiple access (TDMA) divides the channel into slots that are used by each transmitter to send data. To achieve low duty cycles, nodes sleep when slots are not assigned. S-MAC [11] and TMAC =-=[10]-=- are examples of TDMA schemes optimized for low-duty-cycle sensor network applications. The downside of TDMA is its complexity in multihop environments where it requires time synchronization, organiza...

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...n is required among neighboring nodes. During the listen interval, sensor nodes having traffic to send attempt to reserve the medium and signal to the destination to remain awake for the data transmission using the request-to-send/clear-to-send packet exchange mechanism. With S-MAC, one must select the frame duration (i.e. the total of the listen and sleep intervals), as a trade-off between the average power consumption and the transmission delay. S-MAC exploits the concept of fragmentation to transmit large messages in an energy efficient way. Van Dam et al. have proposed T-MAC (Timeout-MAC) [12]. T-MAC is an improvement of S-MAC. In the T-MAC protocol, the length of the active period is dynamically adapted to the traffic, using a timeout. The active period is ended whenever physical and virtual carrier sensing find the channel idle for the duration of the time-out. A similar idea was also and independently proposed by Ye et al. in [15]. S-MAC and T-MAC can currently be seen as benchmarks in the field of contention MAC protocols for sensor networks. WiseMAC will be compared to them. Rabaey et al. have proposed a hardware based solution to wake-up a destination node [9]. They suggest t...

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...tworks) that lack centralized or cluster-based control, and at very low duty cycles. One important approach is to schedule coordinated transmission and listen periods, as seen in S-MAC [26, 27], TMAC =-=[24]-=-, and TRAMA [19]. The schedule determines when a node should listen and when it should sleep. In SMAC and T-MAC nodes adopt common schedules (possibly with help in [13]), synchronizing with periodic c...

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...networks. CSMA-based sleep-wakeup algorithms [2, 26] elect a dynamic ”backbone” of nodes that forwards traffic for the other power-saving nodes. Other proposals synchronize nodes’ sleep-wakeup cycles =-=[27, 21]-=-. In TDMA-based sensor networks, data sources can sleep in all inactive time slots. For any of the above types of networks, the key challenge is designing and evaluating congestion control algorithms ...

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...sts, requires prior specific permission and/or a fee. SenSys’05, November 2–4, 2005, San Diego, California, USA. Copyright 2005 ACM 1-59593-054-X/05/0011 ...$5.00. based on CSMA ([35, 41, 52]), TDMA (=-=[10, 37, 50, 56]-=-), or both ([15, 38]). Numerous topology formation algorithms ([1, 14, 55]), routing protocols ([34, 53]), aggregation algorithms ([27, 33]), and dissemination protocols ([14, 16, 22, 26]) have been p...

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... contentionbased protocols, although TDMA protocols have been studied [32]. The major focus is energy efficiency, and several lowduty-cycle schemes have been proposed, such as S-MAC [51], [52], T-MAC =-=[45]-=-, WiseMAC [13], and B-MAC [28]. New approaches need to be developed to accommodate large propagation delays. Prior work on low-duty-cycle operation aims to provide the illusion of constant network acc...