Providing Throughput Guarantees in 802.11e WLAN Through a Dynamic Priority Assignment Mechanism

Supporting real-time and interactive traffic in addition to traditional data traffic with a best-effort nature represents a constantly rising need in any kind of telecommunications environment. The IEEE 802.11 based WLAN (Wireless Local Area Network) environment does not represent an exception. This is why at different protocol layers, and primarily at the MAC layer, many efforts are being put by both the research community and the standardization bodies to design effective mechanisms for user QoS (Quality of Service) differentiation. Although early results are coming into sight, such as, for example, the IEEE 802.11e standard release, still a thorough research activity is required. Aim of the present paper is to contribute to the cited research issue by proposing an improvement to the “static” traffic prioritisation mechanism foreseen by the IEEE 802.11e MAC (Medium Access Control) protocol. This latter shows a twofold drawback. First, there is no certainty that QoS requirements relevant to a given application are always fulfilled by the “statically” associated priority. Second, resource requests of the applications are not adapted to the (usually highly) variable traffic conditions of a distributed WLAN environment. The algorithm we propose is specifically tailored to “dynamically” assign 802.11e MAC priorities, depending on both application QoS requirements and observed network congestion conditions. It is carefully designed, implemented into a system simulation tool, and its highly effective behaviour assessed under variable traffic and system conditions. Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL/Politecnico di Milano, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996. From 1994 to 1995 he has been at the Mobile Network Division Research Center, Siemens AG Muenchen, Germany to participate to the CEC Project “RACE II 2084 ATDMA (Advanced TDMA Mobile Access)” under a “Commission of European Communities Fellowship Contract in RACE Mobility Action”. He has been with the University of Reggio Calabria, Italy, from 1997 to 2000 as Assistant Professor, and from 2001 to 2005 as Associate Professor. Currently, he is Full Professor of Telecommunications at the same University. In 1995 and in 1996 he has been the recipient of an IEEE Paper Award for the papers presented at the IEEE International Conference on Universal Personal Communications ICUPC'95, and an IEICE/IEEE Outstanding Paper Award for the paper presented at the IEEE ATM Workshop'99, respectively. He served as member of Technical Program Committees of several International Conferences, and in 2003 he has been co-Guest Editor for the special issue “QoS in Next-generation Wireless Multimedia Communications Systems” in the IEEE Wireless Communications Magazine. His research interests include QoS control and resource management in Personal Communications Systems and Enhanced Wireless and Satellite Systems. Giuseppe Ruggeri received the degree in electronics engineering from the University of Catania, Italy, in 1998. He received the Ph.D. degree in electronics, computer science and telecommunications engineering with a dissertation on “Advanced Methods to Improve the QoS in VoIP Systems Based on VBR Speech Coders”. His interests include the field of adaptive-rate voice transmission for IP Telephony applications, and support of Quality of Service in heterogeneous wireless networks and WLAN-3G interconnection-integration . He is currently Assistant Professor in the Department of Computer Science, Mathematics, Electronic and transportation systems (DIMET) at the University “Mediterranea” of Reggio Calabria. His mail address is ruggeri@ing.unirc.it. Domenico Tripodi received M.S. degree (cum laude) in electronic engeneering from the University ‘Mediterranea' of Reggio Calabria, Italy in 2003. He won a post-degree scholarship from CNIT in 2004, and he is currently at CNIT Research Unit of Reggio Calabria. His reasearch interest are in the area of QoS provisioning in Mobile Ad-Hoc Networks.