Evaluation and improvement of multicast service in 802.11b

Abstract

Wireless Technologies have allowed a fast growing of the Internet service in both public and private environments where wireless networks mostly consist of nodes interconnected with a fixed infrastruc- ture; nevertheless, they do not offer a good performance in all the wide variety of services that are required for applications. Although the IEEE 802.11 MAC protocol is the standard for wireless LANs, this protocol shows a very poor performance and reliability compared with the mul- ticast traffic transmitted in wired networks, this represents a significant challenge for existing 802.11 networks because it requires transmission over multiple unreliable channels to heterogeneous receivers with dif- ferent connection bit rates and very limited feedback information to the sender. In this paper, we discuss the drawbacks of several proto- cols proposed in the literature that offer reliable multicast service. In addition, this work evaluates the performance of the wireless networks under multicast traffic and presents a proposal for actual IEEE802.11 networks to improve their efficiency. It uses a reliability control based on a polling service along with controlled retransmissions; this allows servicing nodes applications with a high efficiency without deteriorating fairness in the service. We present details of a prototype implementa- tion and results that suggest that our protocol performs better than other proposed in terms of reliability as well as data throughput in our measurement scenarios