Understanding the Performance of 802.11 Networks

Abstract—In this paper, we review the most important performance characteristics of the 802.11 DCF wireless networks, point out some false common knowledge, and report on recent improvements. I. 802.11 DCF BASICS The IEEE 802.11 DCF (Distributed Coordination Function) [1] uses the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) access method: a station trying to transmit first checks if the channel is free, waits for the DIFS interval (Distributed Inter Frame Space), and then transmits if the medium is still free. The receiving station sends an ACK frame after the SIFS interval (Short Inter Frame Space) if the frame is correctly received. When the station senses the channel busy, it waits until it is free and after the DIFS interval, it chooses random backoff b, an integer uniformly distributed in the contention window [0, CW] (CWmin = 31 for 802.11b and CWmin = 15 for 802.11g) and counts down for b SLOT intervals before attempting to transmit. If another station transmi...

• Type: Conference
• Year: 2008
• Where: PIMRC
• Authors: Andrzej Duda
• Keywords: 802.11 Dcf, Communications, Ieee 802.11 Dcf, Inter Frame Space, PIMRC 2008