"WISEMACWiseMAC protocol uses nonpersistent CSMA (np-CSMA) with preamble sampling as into decrease idle listening. In the preamble sampling technique, a preamble precedes each datapacket for alerting the receiving node. All nodes in a network sample the medium with acommon period, but their relative schedule offsets are independent. If a node finds the mediumbusy after it wakes up and samples the medium, it continues to listen until it receives a datapacket or the medium becomes idle again. The size of the preamble is initially set to be equal tothe sampling period.Advantages The simulation results show that WiseMAC performs better than one of the S-MACvariants Besides, its dynamic preamble length adjustment results in better performance undertraffic conditions.Disadvantages The main drawback of WiseMAC is that decentralized sleep–listen scheduling results indifferent sleep and wake-up times for each neighbor of a node. 18 CONCLUSIONThe emergence of wireless sensor networks as a concept for research in the early years of the21st century has spawned an explosion of proposals that address and meet the generallyunderstood requirements for efficient WSN operation. As sensor nodes are typically consideredto be small, inexpensive, and low processing power devices, energy-efficiency has beenperceived as the primary metric of concern in WSNs. At the heart of research, medium accesscontrol is an intriguing topic, since it directly controls the radio transceiver operation that isconsidered to be the most energy-consuming operation of a sensor network node. As aconsequence, there have been numerous MAC protocol proposals in the scientific community, aswell as industrial and institutional standards for wireless sensor and personal area networks. Theproposed MAC protocols can be categorised in multiple ways according to their type ofoperation, topology, layers involved, etc. to group the nuances of different proposals andperceive the scope. 19 REFERENCES? D. Klair, K.-W. Chin, R. Raad, and D. Lowe, “A spatially aware RFIDenhanced wirelesssensor networks”, in the sixth IEEE International Conference on Pervasive Computing andCommunications (IEEE PerCom): Google PhD Forum, (Hong Kong, China), IEEE, Mar, 2008.? P. Kinney and D. Sexton. Isa100.11a release 1 - an update on the process automationapplications wireless standard. http://www.isa.org/isasp100/, 2008.? www.purelink.ca/.../RelatedTechnologies.aspx.? G. Zhou, T. He, S. Krishnamurthy, J. Stankovic, Impact of Radio Asymmetry on WirelessSensor Networks, Mobisys, June 2004. 20 "