Wireless Local Area Networks (WLANs) are expected to become one of the most widespread solutions for wireless local access to the Internet, both in public environments as well as in the home-network. Many market forecasts show that WLANs could also overcome 3G solutions in the wireless access market, because they provide cheaper and faster access to data networks than cellular wireless systems do. However, a serious limitation to the WLAN success is the fact that they were originally conceived as an extension of the wired-LANs and, therefore, have no differentiation in the offered service. To make WLANs capable of supporting real-time services as well as best-effort data traffic, a large research effort has recently been focused on the optimization of the Quality of Service (QoS)-MAC performance for the upcoming high-data-rate next-generation WLANs. In particular, the IEEE 802.11 Task Group E has been working on a draft proposal for a QoS-aware MAC protocol for the most widespread WLAN technology, namely, IEEE 802.11. This draft considers several service differentiation mechanisms, based on both contention and polling schemes, whose actual effectiveness is still under investigation by the Task Group. In this work we evaluate the performance of the 802.11e MAC by means of computer simulations, in which the specifications given in the draft have been implemented in great detail. To test the QoS capability of the IEEE 802.11e MAC with respect to the actual requirements of the voice, video and high-data-rate applications, real-life scenarios have been defined as test cases, such as home-networking and hot spot environments. Simulation results have been evaluated to define an upper bound of the network capacity in terms of the maximum number of voice and high-data-rate streams that could be fitted in each scenario with the required QoS.
By: Gianluca Vannuccini
Published in: RZ3464 in 2002
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