Extended RTS/CTS Control Based on Transmission Request Distribution in Wireless Ad-Hoc Networks

In a wireless ad-hoc network where wireless nodes exchange data messages without help of stationary base stations, collisions of control and data messages are reduced and/or avoided by CSMA/CA and RTS/CTS control of wireless LAN protocols. Random backoff timers for avoidance of collisions among RTS control messages provides equally opportunities to transmit data messages to neighbor wireless nodes since the value of the backoff timer monotonically decreases. In usual wireless ad-hoc networks, wireless nodes are not equally distributed and frequency of transmission requests in wireless nodes is also not the same. Thus, especially in a region with high density of transmissions and receipts requests for data messages, it is not always possible to receive a response CTS control message even though a wireless node has an opportunity to transmit an RTS control message. Hence, the equal opportunities to transmit an RTS control message is not enough to realize the equal opportunities to transmit a data message. In order to solve this problem, this paper proposes a novel RTS/CTS control to equally provide opportunities to transmit data messages whose receiver node is hard to transmit a CTS control message on response to an RTS control message. Here, a transmission of a CTS control message precedes a transmission of an RTS control message in cases that transmissions of a CTS control message fail repeatedly.