Performance analysis for VoIP traffic with limited retransmissions in IEEE 802.11-based wireless networks

The IEEE 802.11 standards have been widely used for different wireless networks, such as local area networks in communities, office buildings, and vehicular communications. Supporting real-time traffic is one of the main requirements for such networks. In this paper we study the real-time performance for supporting VoIP traffic in an IEEE 802.11-based wireless network. Voice packets experiencing longer delay than the maximum delay are dropped. Traditionally, real-time traffic, such as VoIP traffic, is not retransmitted. However, a small number of retransmissions may be possible if the delay budget is not violated. We consider a network serving both VoIP and best effort data traffic, and analyze the voice traffic performance and the channel utilization. An analytical model is developed to find the delay and packet loss performance by taking into consideration both the MAC layer protocols and wireless channel impairments. Channel utilization is also derived. Our results indicate that a small number (one or two) of retransmissions can significantly reduce the voice packet drop rate without affecting the channel utilization much.