K. Singh, A.K. Awasthi, and R. Mishra (Eds.): QSHINE 2013, LNICST 115, pp. 86–103, 2013. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2013 Comparative Analysis of Contention Based Medium Access Control Protocols for Wireless Sensor Networks Chandan Kumar Sonkar 1 , Om Prakash Sangwan 2 , and Arun Mani Tripathi 3 1 Department of Computer Science and Engineering, Dr. K.N. Modi Institute of Engineering and Technology, Modinagar, Ghaziabad, India 2 School of ICT Gautam Buddha University Greater Noida, India 3 Computer Science and Engineering, Integral University Lucknow, India {c.sonkar1986,amttheking}@gmail.com, opsangwan@gbu.ac.in Abstract. Wireless sensor “motes” is small or tiny embedded systems equipped with radios for wireless communication in the networks, which depend on batteries as a power source. The development of Medium Access Control (MAC) protocols which search is for to minimize the energy consumption in the wireless sensor network. Recent contention based MAC protocols reduce energy usage by placing the radio in a low power sleep state when not sending or receiving the message. In this paper the main emphasis is on the analysis of the Contention Based MAC Protocols and energy consumption in the networks. Based on the work done by various researchers conclude that S-MAC is the backbone of all the MAC protocols for wireless sensor networks. Our proposed work investigated the energy usage and compared the performance of IEEE 802.11 MAC protocol with S-MAC protocol on different modes like without periodic sleep and with periodic sleep on different performance metrics like Remaining Energy vs Time, Energy consumption vs global packet id and Average End to End Delay vs Time. The performance of S-MAC protocol improves on the basis of duty-cycle parameter, which determines the length of sleep period in a frame and this parameter is a variable. So changing the duty cycle will change the performance of S-MAC protocol. Finally, we have used the different routing protocol with S-MAC to evaluate the energy consumption. The experimented worked done on Network Simulator Ns2- 2.34. Keywords: Medium Access Protocol, Wireless Sensor Network, Idle listening, Sleep State, S-MAC, Energy Consumption, Duty cycle. 1 Introduction Wireless communications start from the late 1800s, when M.G. Marconi did the pioneer work establishing the first successful radio communication systems have been developing and evolving with a furious pace. In the early stages, wireless communication systems were dominated by military usages and supported accordingly to military needs and requirements. Over the past few years, the world