TIME SINK ENERGY MAC MAC
The synchronization algorithm adopted by the above synchronous MAC protocols is based on a fixed, periodic synchronization packet broadcast algorithm (F-Sync) by the sensor nodes in SYNC windows. Later developments of synchronous MAC protocols such as DW-MAC, AS-MAC, SEA-MAC and LO-MAC focus on improving the energy efficiency, throughput and delay performances by implementing changes in the scheduling and transmission of data packets, leaving the synchronization algorithm largely unchanged. During DATA windows, sensor nodes send out data packets from the higher layers based on some contention mechanisms to avoid collisions. During SYNC windows, sensor nodes broadcast synchronization ( sync) packets periodically to synchronize the clocks of the neighboring nodes. The seminal synchronous duty-cycle MAC protocol S-MAC further divides the active periods into SYNC and DATA windows. Once the preamble is detected, the receiver will stay awake to receive the data. When a sensor node has data to send, it has to first transmit a preamble that is longer than the sleep period of the receiver so that the receiver will be able to detect the preamble. On the other hand, the asynchronous or preamble sampling approach does not use a synchronization algorithm, but places the burden of data delivery on the senders. The synchronous approach makes use of a MAC layer synchronization algorithm to synchronize sensor nodes in the same neighborhood so that they can wake up at the same time to exchange sensor data. There are two main categories of duty-cycle MAC protocols.
In addition, energy-efficient solutions in Network, Transport and Application layers are also discussed in.
provide comprehensive reviews of duty-cycle MAC protocols for WSNs. Sensor nodes in duty-cycle networks schedule the transmission and reception of data during active periods, and switch the radios off completely during sleep periods to conserve energy. This is a common approach used in the MAC layer to reduce idling time and consequently reduce energy consumption. This idle listening is the dominant source of energy consumption in WSNs.ĭuty-cycling is a mechanism where sensor nodes alternate between active and sleep periods.
A typical wireless sensor network (WSN) generates very light traffic and sensor nodes spend most of the time listening to the radio channel and idling.
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