Improved CSMA/CA Protocol for IEEE 802.11

Abstract

This paper describes a modification of the CSMA/CA protocol used in IEEE 802.11 wireless networks for improving medium reservation actions. The modification promotes bidirectional data transfers between stations that reserve the medium using an RTS/CTS handshake. This approach reduces the amount of RTS/CTS handshakes required when two stations have simultaneously data to send to each other. Consequently, we improve the occupation of the medium with useful data transfers and minimize RTS collisions by reducing the number of RTS/CTS handshakes required to exchange data. Theoretical performance evaluations with several operational parameters and data volumes showed a reduction of 7 to 47% of the elapsed time to complete a bidirectional data exchange. Fairness in the medium access is kept but stations should use extra policies for preventing frames in output queues to take too long to be transmitted; a simple policy based on per-frame counters is sketched.