Two Simple Modifications for Improving IEEE802.11DCF Throughput Performance

Abstract

IEEE802.11 employs Distributed Coordination Function (DCF) as a media access control method. In order to address the hidden terminal problem, the DCF equips the virtual carrier sensing function in addition to the traditional carrier sensing function, CSMA. The virtual carrier sensing is realized by the RTS/CTS short packets exchange and the NAV. The RTS/CTS exchange can keep terminals other than the sender and the receiver silent for ensuring a data packet transmitted correctly. The NAV is a timer that indicates the amount of time that the medium will be reserved. The first modification is to replace the NAV for RTS of DCF to the one used in the protocol MACA (the idea of RTS/CTS exchange is originally proposed in the MACA). Simulations show that this modification improves the throughput performance. On the other hand, the DCF is designed to use ACK packet for ensuring correct data transmission in the media access control layer, while the ACK did not used in the MACA. We secondly show that the use of the ACK reduces the throughput performance of DCF when the RTS/CTS exchange is in use, concluding that by omitting the ACK from the DCF, the performance can be improved. This paper not only shows that these two simple modifications can improve the performance of the DCF but also points out that the functions being implemented in the DCF do not always work well for realizing higher performance