Résumé: Design of Wireless Local Area Networks (WLANs) needs to take into consideration the limited bandwidth available in the ISM band along with the noisy characteristics of the wireless environment and hidden terminal effects. In this paper we propose an enhancement for IEEE 802.11 standard that improves the WLAN support for multimedia applications. In the IEEE 802.11 PCF polling based protocol designed for multimedia applications support, the Point Coordinator (PC) polls each station in the Basic Service Area (BSA) individually. In the proposed SuperPoll approach the PC broadcasts at the beginning of the contention free period a SuperPoll, i.e., a message that includes the list of stations that will be polled during the current period. To improve the reliability of the polling based approach in a noisy environment, we propose to use a chaining mechanism in which each packet resends in its turn the SuperPoll message appended to its packet. We provide performance measurements of the proposed method in terms of channel efficiency and channel access time for multimedia applications that use the contention free period of IEEE 802.11 PCF. We notice that for noisy channels, the proposed method provides a dramatic throughput increase and delay decrease when compared with the Single Poll mechanism used in IEEE 802.11 PCF, thus providing better support for multimedia applications.

Langue: Anglais