Efficient multicast supporting in multi-rate wireless local area networks

Abstract

Wireless local area networks(LAN) have become popular due to their capability of supporting the high data rates required in ubiquitous computing. These high data rates are possible through the use of new modulation schemes that are optimized for different channel conditions. In particular, IEEE 802.11b supports a variety of different data rates, i.e. 11Mbps, 5.5Mbps, 2Mbps and 1Mbps, depending on the channel conditions between the access point(AP) and the mobile station. All mobile stations share the same wireless channel or frequency, so the bottleneck point of wireless LAN system is the traffic load of the lowest data rate connections. Since wireless LAN supports higher data rates, it is more attractive for ubiquitous multimedia services. Multimedia services generally require high bandwidth and most of them utilize the multicast system. Since most multimedia services are provided by real-time communications, reduced end-to-end packet delay and delay jitter are more important than reliable packet transmission. However the data rate of the multicast communication used in most commercial products is generally set to be low by the administrator, who only considers the coverage of the AP, and its value is generally fixed. In this environment, data rate which is selected for the transmission of multicast packets is a very important factor in determining the system performance of the wireless LAN, since multimedia services require a large bandwidth. Thus, a new algorithm is necessary to dynamically select the data rate of the multicast according to the traffic load of the wireless LAN. In this paper, we present two naive data rate selection algorithms which allow the data rate to be dynamically adjusted, and a more novel data rate selection algorithm based on the two primitive algorithms. We show that our suggested algorithm achieves high performance in wireless LAN and efficiently supports high quality multimedia services, through the use of the NS - 2 simulation in a wireless LAN environment based on IEEE 802.11b. © Springer-Verlag Berlin Heidelberg 2003.