Modeling Data Rate Agility in the IEEE 802.11a Wireless Local Area Networking Protocol

摘要

The IEEE 802.11a high-speed wireless local area networking (WLAN) protocol does not specify a mechanism for dynamically altering network data rates based on changing link conditions. This thesis first presents a baseline software model of the 802.11a protocol developed using the OPNET simulation tool. The model includes both the medium access control (MAC) and physical (PHY) layers of the standard. Two data rate agility mechanisms are then proposed and analyzed using the model. An infrastructure WLAN implementation of the baseline model is first simulated under standard network conditions to verify its operational characteristics and the results are presented. The model is then used to simulate two data rate agility mechanisms, one based on the link signal- to-noise ratio (SNR) and the other based on the frame loss rate at the transmitting Station. Each technique is simulated using an infrastructure WLAN consisting of a fixed access point and a mobile workstation operating with standard network traffic loads. The results indicate that the link SNR is a better decision criterion for data rate agility than the frame loss rate. The design and methodology of this analysis provides insight into dynamic rate agility mechanisms and the criteria that may be used in developing in future 802.11 a-compliant hardware imlementations.