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WNS_project_report_1a

WNS_project_report_1a - CSE 566 WIRELESS NETWORK SECURITY...

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CSE 566 - WIRELESS NETWORK SECURITY PROJECT 1a BY SARANYA CHUNDI PRAKASH NAIR SANDEEPKRISHNAN POYYALAE
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INTRODUCTION Throughput and Delay are two important metrics for the evaluation of a network. Throughput or network throughput is the average rate of successful message delivery over a communication channel. The throughput is usually measured in bits per second (bit/s or bps), and sometimes in data packets per second or data packets per time slot. The throughput of a communication system is limited by a number of factors. End to End delay is an important design and performance characteristic of a computer network or telecommunications network. The delay of a network specifies how long it takes for a bit of data to travel across the network from one node or endpoint to another. It is typically measured in multiples or fractions of seconds. There are many factors which affect end to end delay in a communication network. In this project we will use NS, the discrete event simulator to evaluate these metrics for the 802.11 MAC protocol in a Multi-Hop environment and will analyze how these affects the performance of the wireless network. Problem Addressed IEEE 802.11 MAC protocol has been the standard for Wireless LAN's and also adopted in many network simulation packages for wireless Multi-Hop ad hoc networks. However it is well known that, as traffic goes up the performance drops dramatically in terms of delay and throughput. The IEEE 802.11 defines two layers. The first layer is the Physical layer (PHY), which specifies the modulation scheme used and signaling characteristics for the transmission through radio frequencies. The second layer is the media access control (MAC). This layer determines how the medium is used. The MAC is a set of rules that determine how to access the medium and data link components. The MAC rides on every transmission of user data into the air. It provides the core framing operations and the interaction with a wired network backbone. The MAC layer supports two modes of operations. The first mode is the point coordination function (PCF) and the second mode is the distributed coordination function (DCF). The PCF is built on top of the DCF, and is used only on infrastructure networks. The DCF mode uses the carrier sense multiple access with collision avoidance (CSMA/CA) protocol. In this protocol, when a user wants to transmit data packets to a receiver, it must sense the wireless medium first. If the me dium is busy, it chooses a random “back - off time” to wait and then tries again. Once the medium is idle, it sends out a control packet called “ready to send” (RTS), which contains the source station address, the destination station address and the duration of the intended packet. If the destination station is ready to accept the transmission upon receiving the RTS, it responds with a response control packet called “clear to send” (CTS) with
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the same information contained in it. Once the source receives the CTS, it transmits the packet.
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