Evaluation and improvement of multicast service in 802.11b

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 infrastructure; 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 multicast 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 different connection bit rates and very limited feedback information to the sender. In this paper, we discuss the drawbacks of several protocols 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 implementation 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.3