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...io turned on, listening for a possible packet to be received even though none has been sent. Many solutions to the problem of idle listening have been proposed utilizing the technique of duty cycling =-=[19, 23]-=-. In this technique, each sensor node turns its radio on only periodically, alternating between active and sleeping states. For example, with a 10% duty cycle, a node has its radio on only 10% of the ...

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...e to convergecast [25] and correlated-event workload traffic [13], where multiple sensors that have detected the same event send their reports to the sink node or to a node that does data aggregation =-=[11]-=-. As traffic in a WSN can be quite dynamic, depending on the events being sensed and the sensing application and protocols being used, an ideal WSN MAC protocol should perform well under a wide range ...

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...io turned on, listening for a possible packet to be received even though none has been sent. Many solutions to the problem of idle listening have been proposed utilizing the technique of duty cycling =-=[19, 23]-=-. In this technique, each sensor node turns its radio on only periodically, alternating between active and sleeping states. For example, with a 10% duty cycle, a node has its radio on only 10% of the ...

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...save energy. Contention-based duty cycle MAC protocols in the literature can be roughly categorized into two categories: synchronous and asynchronous. Synchronous approaches such as S-MAC [23], T-MAC =-=[7]-=-, RMAC [8], and DW-MAC [20] synchronize neighboring nodes in order to align their active or sleeping periods. Neighbor nodes start exchanging packets only within the common active time, enabling a nod...

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...ization introduces extra overhead and complexity, and a node may need to wake up multiple times if its neighbors are on different schedules. Existing asynchronous approaches such as B-MAC [19], X-MAC =-=[3]-=-, and WiseMAC [9], on the other hand, allow nodes to operate independently, with each node on its own duty cycle schedule. Such protocols typically employing low power listening (LPL), in which, prior...

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...er and over again. Synchronized duty cycle MAC protocols, such as S-MAC [23], T-MAC [7], RMAC [8], and DW-MAC [20], also achieve great energy efficiency in WSNs; so too, hybrid approaches such as SCP =-=[24]-=-. The major difference between RI-MAC and these MAC protocols is that RI-MAC does not require any synchronization, thus saving the overhead and complexity of clock synchronization. Even though no node...

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...edium is not occupied, some of them could experience significant delay. This is often the case under bursty or high traffic load such as due to convergecast [25] and correlated-event workload traffic =-=[13]-=-, where multiple sensors that have detected the same event send their reports to the sink node or to a node that does data aggregation [11]. As traffic in a WSN can be quite dynamic, depending on the ...

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... detecting a collision, a receiver calculates the new BW value that will be used in the next beacon, by employing some backoff strategy such as binary exponential backoff (BEB) in IEEE 802.11 or Sift =-=[14,21]-=-, depending on the density of a network. BEB is used in our implementation in TinyOS, as we found it adapts to networks of different densities and resolves collisions efficiently in RI-MAC in our eval...

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... detecting a collision, a receiver calculates the new BW value that will be used in the next beacon, by employing some backoff strategy such as binary exponential backoff (BEB) in IEEE 802.11 or Sift =-=[14,21]-=-, depending on the density of a network. BEB is used in our implementation in TinyOS, as we found it adapts to networks of different densities and resolves collisions efficiently in RI-MAC in our eval...

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...ta. As these nodes have to wait until the medium is not occupied, some of them could experience significant delay. This is often the case under bursty or high traffic load such as due to convergecast =-=[25]-=- and correlated-event workload traffic [13], where multiple sensors that have detected the same event send their reports to the sink node or to a node that does data aggregation [11]. As traffic in a ...

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...or5 5 Special Frame Short Preamble — Beacon Special Frame Size 6B — 6–9B Dwell Time 10.5 ms 100 ms Variable sensing range to the transmission range are also observed in some state-of-art sensor nodes =-=[2]-=-. Table 2 summarizes the MAC protocol parameters we used in our simulations. Backoff strategy and retransmission have not been explicitly discussed in prior work [3, 15], as X-MAC is optimized for lig...

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...ism was designed only for packets being sent from an access point to a sensor node. Another receiver-initiated mechanism, known as Low Power Probing (LPP), was recently introduced in the Koala system =-=[18]-=-. Koala is designed for reliably downloading bulk data from all sensor nodes, for applications with no real-time requirements. All downloads in Koala are initiated by the gateway or gateways, allowing...

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...sed duty cycle MAC protocols in the literature can be roughly categorized into two categories: synchronous and asynchronous. Synchronous approaches such as S-MAC [23], T-MAC [7], RMAC [8], and DW-MAC =-=[20]-=- synchronize neighboring nodes in order to align their active or sleeping periods. Neighbor nodes start exchanging packets only within the common active time, enabling a node to sleep for most of the ...

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...ued packets to be transmitted immediately. We refer to this duration as the dwell time in the rest of this paper. The UPMA (Unified Power Management Architecture for Wireless Sensor Networks) package =-=[15]-=- implemented a variation of X-MAC in TinyOS, in which the DATA frame itself is used as the short preamble, as illustrated in Figure 2. This strategy simplifies implementation and helps a sender to det...

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...sfully transmit a packet to the receiver even if the transmission overlaps with others, especially when senders have different distances to the receiver (and thus different received signal strengths) =-=[16, 17]-=-. 3.5. Collision Detection and Retransmissions By coordinating DATA frame transmissions at receivers, RI-MAC greatly reduces the cost for detecting collisions and recovering lost DATA frames compared ...

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...y. Contention-based duty cycle MAC protocols in the literature can be roughly categorized into two categories: synchronous and asynchronous. Synchronous approaches such as S-MAC [23], T-MAC [7], RMAC =-=[8]-=-, and DW-MAC [20] synchronize neighboring nodes in order to align their active or sleeping periods. Neighbor nodes start exchanging packets only within the common active time, enabling a node to sleep...

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...es which are hard to deploy and experiment with. As a protocol may not perform in the real world exactly as it does in simulation, for example due to the simplified physical layer models used in ns-2 =-=[1]-=-, we also evaluated RI-MAC in a small testbed network of MICAz motes running TinyOS; our experimental results match our results obtained in simulation and further verify RI-MAC’s performance advantage...

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... Figure 8. We implemented RI-MAC for the CC2420 radio, which is a packetizing radio used in popular MICAz and TelosB motes, although the code can be ported to motes with streamingradiossuchastheCC1000=-=[5]-=-aswell. The BeaconManager module in Figure 8 performs most of the functionality of RI-MAC, including beacon generation, radio power control, wakeup/sleep scheduling, and retransmission control. We als...

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...cling in the context of MAC protocols for ad hoc wireless sensor networks, where power efficiency is a major concern. Garcia-Luna-Aceves et al. proposed a receiver-initiated collisionavoidance scheme =-=[12]-=- for general wireless networks, where collision is a major concern but power efficiency is of lesser importance. Receiver-initiation has previously been applied to sensor networks in the PTIP (Periodi...