On Frugality of Control Packets in Multi-Hop Wireless Networks

Abstract

Carrier sense multiple access (CSMA) is a media access scheme used in multi-hop wireless networks. Because a node is unable to detect a collision while it transmits signals, reducing the collision rate is important to increase the network performance. Since the advent of MACA, it has been believed that RTS/CTS exchange in multi-hop wireless networks prevents collisions caused by hidden terminals in most situations. Recently, several research papers presented cases where the RTS/CTS exchange fails to prevent collisions caused by hidden terminals. In this paper, we show by simulations that RTS/CTS exchange under contemporary physical layer technologies actually has limited effect on fast collision inference and on resolving the hidden terminal problem. We also present a situation where an ACK packet causes a collision and show that this type of collisions has a significant effect on the performance of multi-hop wireless networks. We also present a modified media access scheme that reduces the number of collisions caused by ACK and compare the proposed scheme with basic access mode and RTS/CTS exchange mode of IEEE 802.11.