QoS Management and Congestion Control in Wireless Hotspots

Abstract

A key factor for the success of hotspot deployment is played by the capability of supporting real-time multimedia applications. The IEEE 802.11e standard for providing QoS in 802.11 WLANs (wireless LANs) has been recently completed. It allows differentiated QoS guarantees for different types of traffic, like video, voice and best effort. In this paper we first propose a method for guaranteeing QoS that combines the capabilities of the IEEE 802.11e standard with the control functionalities of a policy server, designed for the control of a multiple access points (APs) hotspot. The method presented in this paper allows providing QoS guarantees not only based on the type of traffic but also on the customer's contract. A further major performance factor in hotspots is the ability to prevent congestion at the AP. In fact, hotspots are dimensioned according to typical working conditions. However, some sporadic events might cause congestion at some AP, raising therefore severe performance issues. The second major contribution of this paper is a novel approach for providing hotspot congestion prevention and relief, which combines the support offered by the IEEE 802.11e standard and the capabilities of a centralized hotspot controller. The method takes into account the different loads generated on the network by some users, e.g. video ones, compared to other users and we introduce therefore the concept of equivalent number of users. We then suggest how to efficiently control user association at one AP and propose a QoS aware scheme to balance the load between APs. The validity of our approach is supported by a set of simulations based on a prototype implementation of the hotspot controller