An analytical model for IEEE 802.11 WLANs with NAK-based ARQ mechanism

As the physical transmission rate develops rapidly in the modern IEEE 802.11 WLANs, the efficiency of traditional stop-and-wait(SAW) automatic repeat request (ARQ) mechanism degrades dramatically. Negative acknowledgement (NAK)-based ARQ mechanism is a proper candidate to improve the link layer performance. In this paper we propose a discrete-time Markov chain (DTMC) model to analyze the performance of the IEEE 802.11 WLAN system with NAK-based ARQ mechanism. Then the analytical performance is compared with that of SAW ARQ. We find that NAK-based ARQ outperforms SAW ARQ in terms of system throughput while performs poorly in terms of transmission delay. Then a hybrid ARQ scheme is proposed, through which the system can leverage between the two mechanisms to achieve better quality of service(QoS) guarantee. The simulation result validates the correctness of the proposed model and scheme.