Performance Analysis of the IEEE 802.11 Distributed Coordination Function: Bianchi Model

Currently, IEEE 802.11 is the de facto standard for WLANs [1]. It specifies both the medium access control and the physical layers for WLANs. The scope of IEEE 802.11 working groups (WGs) is to propose and develop MAC and PHY layer specifications for WLAN to handle mobile and portable stations. In this standard, the MAC layer operates on top of one of several possible physical layers. Medium access is performed using carrier sense multiple access with collision avoidance (CSMA/CA). Concerning the physical layer, four IEEE 802.11 standards are available at the time of this writing: a, b, g, and n. The first IEEE 802.11 compliant products were based on 11b. Since the end of 2001, higher data rate products based on the IEEE 802.11a standard have appeared on the market [2]. The IEEE 802.11 working group has approved the 802.11g standard in June 2003, which extends the data rate of the IEEE 802.11b to 54 Mbps [3]. The 802.11g PHY layer employs all available modulations specified for 802.11a/b. IEEE 802.11n is a recent amendment which improves the data rate (up to to 600 Mbit/s) by adding multiple-input multiple-output (MIMO) and many other newer features. In Section 2 of this document, we briefly describe the operating principles of the IEEE 802.11 MAC layer, which need to be known for a proper understanding of the IEEE 802.11 performance evaluation. There are different analytical models and simulation studies of the 802.11 MAC layer in saturated condition. In Section 3, we present one of the most well-known analytical model, the so-called Bianchi model [4], to analyze the performance of IEEE 802.11 MAC layer. Finally in Section 4, we present the numerical solution of Bianchi model for the 802.11a/b networks.