Asymmetric RTS/CTS in Ad Hoc Wireless LAN Akihisa MATOBA , Masaki HANADA, Hojun MOON, Moo Wan KIM Tokyo University of Information Sciences, Japan mwkim@rsch.tuis.ac.jp Abstract— A wireless network node with the Omni antenna tends to cause problems called “Hidden Node” and “Exposed Node”. RTS/CTS mechanism has been introduced to mitigate Hidden Node and most of existing researches assume that RTS and CTS are sent at the same data rate. In this paper we have intentionally allocate different transmission rate to RTS and CTS in order to mitigate effect of Exposed Node. The simulation result showed that the proposed method achieved higher throughput. Keywords— Exposed Node, Hidden Node, IEEE802.11, Simulation, RTS/CTS I. INTRODUCTION A wireless network node with Omni antenna tends to cause problems called “Hidden Node” and “Exposed Node” [1]. Assuming a sender node and a receiver node, a Hidden Node is located near to the receive node and can hear the transmission from the receiver while it cannot hear the transmission from the sender as it is far enough from the sender. The Hidden Node and the sender can send a frame respectively at the same moment and can cause a collision at the receive node. An Exposed Node is located near the sender and its transmission reaches to the sender but cannot reach to the receiver as it is far enough from the receiver. The Exposed Node doesn’t cause a collision at the receiver when it sends a frame at the same moment when the sender sends a frame. But due to carrier sense mechanism of IEEE802.11, the Exposed Node detects a transmission of the sender and has it suspend the transmission. This may cause unnecessary transmission suspensions and degrade network performance. Even it can cause pseudo dead-lock situation in network [2]. ACK CTS RTS Data Sender Node Receiver Node SIFS SIFS Exposed Node Hidden Node CTS NAV RTS NAV SIFS Figure 1. RTS/CTS Mechanism ISBN 978-89-968650-2-5 575 February 16~19, 2014 ICACT2014