One Of The Fastest Growing Technologies Computer Science

Essay add: 14-11-2016, 18:41   /   Views: 14

Wireless communication is one of the fastest-growing technologies. The demand for connecting devices without the use of cables is increasing everywhere. Wireless LANs can be found on college campuses, in office building, and in many public areas. Wireless technology has helped to simplify networking by enabling multiple computer users to simultaneously share resources in a home or business without additional or intrusive wiring. These resources might include a broadband Internet connection, network printers, data files, and even streaming audio and video. This kind of resource sharing has become more prevalent as computer users have changed their habits from using single, stand-alone computers to working on networks with multiple computers, each with potentially different operating systems and varying peripheral hardware.

A Stranded protocol IEEE 802.1 has been used in Wireless Local Area Networks (WLANs). The IEEE 802.1 protocol [4] is the dominant standard for WLANs and employs Distributed Coordination Function (DCF). IEEE 802.1 DCF specifies Medium Access Control (MAC) protocol for WLANs [20]. The performance of a wireless network depends upon the medium access control (MAC) protocol used. Carrier Sense Multiple Access Collision Avoidance (CSMA/CA) protocol is often chosen because of its simplicity and scalability. However, CSMA/CA a node may transmit a packet using one of the following two methods: the basic access method or the RTS/CTS method. In the basic access method, a node transmits a DATA packet if it senses the channel to be idle. The receiver, upon receiving an error-free packet, returns an ACK. If the transmitting node does not get an ACK back, it enters into back-off and retransmits after the back-off period. The basic access method suffers from the well-known hidden node problem [19]. Hidden nodes cause packet collisions and thus considerably affect network performance. In order to address the issue, IEEE 802.1 supports a mechanism known as RTS/CTS handshake.

This report focuses on RTS/CTS mechanism. From a network point of view, one of the primary reasons for using the RTS/CTS mechanism is to avoid network congestion resulting from frequent packet collisions. The RTS/CTS mechanism generally works well in infrastructure-based networks, even though it may lead to unfairness in some situations [9]. However, in the general setting of ad hoc networks, the current way of implementing the RTS/CTS mechanism gives rise to situations where a large number of nodes are unable to transmit any packet. These situations can lead to network-level congestion. Therefore, the RTS/CTS mechanism fails to achieve its goal from a network point of view. Therefore, several modifications have been done in RTS/CTS mechanism.

Motivation

Wireless local area network (WLAN) has been an integral part of life now days. It requires no physical connection. Improving its performance is a much difficult task. Improvement of performance of MAC layer is of more concern. MAC layer have different modules out of which medium access mechanism based on RTS/CTS handshake is focused in this report. In the existing RTS/CTS mechanism, there are some additional problems which degrade network performance. Several solutions were proposed for hidden and exposed terminal problem, to improve the performance and fairness of 802.1 MAC. By default 802.1MAC uses CSMA/CA, which prevents the possibility of parallel communication by two neighbouring nodes that are either at sender or at receiver. Because of the use of 4-way handshaking i.e. RTS/CTS method, the neighbouring node that receives a RTS or CTS packet set their NAV, and are forced to defer their transmission for the whole duration of ongoing transmission. The problems arise when RTS or CTS is not successfully received by the addressed node, which causes the channel waste resulted from unnecessary NAV setting. This is identified as RTS-induced and CTS-induced problem. An efficient modification in RTS/CTS mechanism is essential that would provide the level of fairness by overcoming all these problems without compromising the network performance. With this motivation for developing a new algorithm, the major goal of this dissertation is identified.

Dissertation Goal & Purpose

Based on the features associated to Ad hoc network and the basis of troubles and vulnerabilities in such network, our study on medium access mechanism has focused RTS/CTS mechanism. This issue is main centre of this dissertation. In this dissertation, I figure out the consequences of RTS/CTS mechanism and modifications done in this mechanism and their possible improvement plans. In this documentation simulation experiment, focuses on-

The study center for concentration on study of black RTS/CTS access mechanism in ad hoc network and problems associated with it.

A generic modification of RTS/CTS mechanism and a classification of possible solution to

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