A MAC Layer ARQ Tuning Scheme to Optimize TCP Throughput in IEEE 802.11 Networks

The enhancement of physical layer transmission technology provides lower packet error probability (PER) and consequently higher data rate in the modern IEEE 802.11 WLAN system. On the other hand, the commonly used stop-and-wait (SAW) ARQ mechanism, in which the acknowledgement is transmitted with the control data rate, will bring in significant bandwidth waste under high data rate environment. The "no acknowledgement" (NACK) ARQ in medium access control (MAC) layer is an appropriate candidate to alleviate the bandwidth inefficiency. What\´s more, retransmission in MAC layer is unnecessary because the end-to-end error has been guaranteed by transport control protocol (TCP), which reassures the predominance of NACK. In the paper the TCP layer throughput under the NACK ARQ mechanism is analyzed, based on which we propose a scheme that alternates between two of them according to the variation of wireless environment to achieve maximum end-to-end performance. Simulation results demonstrate that the tuning scheme significantly outperforms SAW in terms of TCP layer throughput.