Frame Collision Reduction Method Employing Adaptive Transmission Control for IEEE802.11 Wireless LAN System

Akira KISHIDA  Masashi IWABUCHI  Toshiyuki SHINTAKU  Takeshi ONIZAWA  Tetsu SAKATA  

IEICE TRANSACTIONS on Communications   Vol.E97-B   No.9   pp.1790-1799
Publication Date: 2014/09/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.1790
Type of Manuscript: Special Section PAPER (Special Section on Ambient Intelligence and Sensor Networks)
CSMA/CA,  IEEE802.11,  collision reduction,  dense,  IFS,  

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The IEEE 802.11 distributed coordinated function (DCF) adopts carrier sense multiple access with collision avoidance (CSMA/CA) as its medium access control (MAC) protocol. In a wireless local area network (WLAN) stations (STAs) congested situation, the performance of the WLAN system is significantly degraded due to a collision between the STAs. In this paper, we propose a simple method that decreases the number of frame collisions. After a successful transmission, the proposed method refrains from transmission during certain time which is defined as post-inter-frame space (Post-IFS). This mechanism improves the system performance including the throughput characteristics and access delay by reducing the number of competing STAs. The length of the Post-IFS is a key factor in improving the system performance for the proposed method. If the access point (AP) can estimate the optimal value of the Post-IFS, collision-free operation similar to that in centralized control is performed. Even if the optimal Post-IFS is not estimated, the number of competing STAs and the collision probability are decreased. Computer simulations verify that the proposed method achieves 40% higher system throughput compared to the conventional CSMA/CA for a network with 50 STAs.