Understanding the Impact of Mobility to the Performance of the IEEE 802.11 DCF

IEEE 802.11 series standards have been widely used to specify the MAC mechanism in wireless networks. The 802.11 DCF has not taken into account of the mobility of wireless stations, instead, it is defined based on the assumption that the mobility is not present or is very low. Mobility of wireless stations downgrades the saturation performance of the IEEE 802.11 DCF. This paper made its efforts to anatomize into the relations between the mobility movement and the damaged coordination incurred. Reducing the average backoff duration is a viable approach to improve the average saturation throughput. We suggested an additive increase and multiplicative decrease (AIMD) algorithm to determine the backoff time. Such an AIMD backoff algorithm helps to take mild reactions to non-persistent collisions induced by mobility of wireless stations. Results obtained from simulations under the new AIMD backoff algorithm show that the average saturation throughput is improved in the presence of mobility of stations. The improvement mainly attributes to the shortened average backoff duration under the AIMD backoff algorithm. Jun Liu Computer Science Department University of North Dakota Grand Forks, ND 58202 [email protected]