Performance Analysis of IEEE 802.11 Modified DistributedCoordination Function for Wireless LANs Based on Data rate
Journal Title: IOSR Journals (IOSR Journal of Computer Engineering) - Year 2014, Vol 16, Issue 6
Abstract
Abstract: IEEE has standardized 802.11 protocol for Wireless Local Area Networks.The 802.11 MAC standardspecifies two access mechanisms, the Distributed Coordination Function (DCF) and Point CoordinationFunction (PCF). DCF is considered as the basic MAC mechanism, based on the carrier sensing multipleaccess with collision avoidance (CSMA-CA) protocol, which is introduced to avoid the collision.The mainproblem with 802.11 MAC layer is the implementation defects of DCF.The Distributed Coordination Function(DCF) in the IEEE 802.11 standard preserves fairness for all clients at the frame level. That is, all clientswould achieve the same throughput (in terms of numbers of frames transmitted or received) in the long runwithout considering their data rates. As a consequence, it will take much longer time for a low data rate clientto transmit / receive a frame than clients with higher data rates.It results in the low throughput of fast clientsand a poor performance of the whole system. This is regarded as a major problem in IEEE DCF interms of theirperformance . DCF allows a uniform packet delivery irrespective of the data rate. In the existing system thethroughput is independent of the data rate. This can be observed from the throughput analysis. But in themodified version of DCF called MDCF gives a far better performance for nodes with high data rate. Thus in theproposed method high data rate node traffic is optimized. This is achieved by making changes to the MAC layerof IEEE 802.11. The frames and packets are dropped only after analyzing the data rate. Packets from nodeswith high data rate are given preference over packets from nodes with low data rate.Performance Analysis isdone based on various parameters and results show that proposed sysytem(MDCF)is better than normal DCF.
Authors and Affiliations
Manjusha Mathew , Mary John
Keywords
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