Analysis and Implementation of IEEE 802.11 MAC Protocol for Wireless Sensor Networks

Energy Consumption in Wireless sensor networks is one of the main challenges for researchers. Many researchers have been done for extending the overall network lifetime by minimizing the power consumption of sensor nodes. Most of the work is done over the MAC layer of network in which different kinds of MAC protocol used by sensor networks. Most commonly used standard is 802.11. Sensor networks consist of small, inexpensive, resource constrained devicesthat communicate wirelessly in a multihop network. Each device, called asensor node, collaborates with other devices in the network to perform some operation for the end user, such as environmental monitoring or target tracking.End users typically desire to deploy hundreds to thousands of sensor nodes randomly;each sensor node often has a simple processor and limited memory resources. Producing simple, small, and inexpensive devices also limits the energy resourcesavailable for sensor node operation. Replacing or renewing energy resources afterdeployment becomes infeasible or too costly in most cases, so the protocolsand applications must make judicious use of the finite energy resources. As medium accesscontrol (MAC) has a significant effect on the energy consumption, energy efficiency is one of the fundamentalresearch themes in the design of MAC protocols for WSNs.In this paper, we described an energy efficiency of IEEE 802.11 protocol which is a standard MAC protocol. The paper presents simulation results of IEEE 802.11 performance on a sensor node with different scenarios. NS-2 is used for simulation purpose. Wireless sensor networks have emerged as one of the first real applications of ubiquitous computing. It has become a hot issue in research, and it is regarded as one of the ten influencing technologies in the 21st century (1). A WSN is defined as being composed of a large number of nodes, which are deployed densely in close proximity to the phenomenon to be monitored. WSNs communicate via a radio interface instead of being wired to a control station. Sensors themselves are normally not equipped with a radio interface. Therefore, a simple signal processor and a radio are packaged together with one or more sensors into what is called a wireless sensor node. This is an emerging technology that has a wide range of potential applications including event tracking, environment monitoring, smart spaces, medical systems, agriculture, robotic exploration, traffic surveillance, military surveillance, fire detection, structure and earthquake monitoring, disaster relief, search and rescue, etc. WSNs can be deployed extensively in the physical world and spread throughout our environment. They can be sited far from the actual occurrence and can still be used for data aggregation and collection from a remote location far away from the phenomenon. The WSNs comprise of a large number of application-specific wireless sensor nodes (typically in hundreds of thousands in number) spread over varying topographies. This kind of random placement of the sensor nodes does not follow any fixed pattern and the density of nodes is not dependent on any factor. Once they are deployed in the environment (under scrutiny where sensing needs to take place), these hundreds and thousands of nodes have to organize themselves in the network by listening to one another. They self-organize themselves by creating multi-hop wireless paths through mutual co-operation. The nodes work collectively and collaborate together on common tasks of sensing/data- collection/communications etc. to provide good network-wide performance in terms of network life-time, latency, and uniform density of available nodes for sensing. WSNs offer unique benefits and versatility with respect to low-power and low-cost rapid deployment for many applications that do not need human supervision. Some of these applications include disaster recovery, military surveillance, health administration, environmental & habitat monitoring, target-tracking etc. Due to the large numbers of nodes involved in the WSN deployment new benefits to the afore-mentioned sensing applications including: • Extended range of sensing • Robustness and fault-tolerance • Improved accuracy • Lower cost However to be able to realize all the discussed specifications we need to design protocols that can provide appropriate support and allow the wide-spread use of WSNs.