Traffic Engineering In Broadband Wireless Networks
University of Siena - Dipartimento di Ingegneria dell'Informazione e Scienze Matematiche
20-24 aprile 2009
Abstract. The design of modern networks requires a deep knowledge of e.g., network characteristics, transmission media types, and traffic demand statistics. The wireless medium adds to these aspects a greater variability in channel capacity and the presence of frequent packet errors that have a significant impact on the performance at higher layers. Moreover, wireless network resources are costly and must be efficiently utilized. Therefore, the crucial point for modern broadband wireless networks is the provision of multimedia services, guaranteeing several Quality of Service (QoS) requirements, differentiated depending on the application the user is running (i.e., traffic classes). The course will be organized in four parts as detailed below.
1) Queuing models for telecommunication systems. In particular, queuing systems of the M/G/1 type will be investigated and theoretically solved by means of the imbedded Markov chain approach. Application examples will be provided dealing with link (re)transmissions with ARQ schemes, multiplexing of packet data traffic, and the leaky bucket regulator. Finally some considerations on traffic flow models, traffic burstiness and ITU-T QoS requirements will be provided.
2) MAC protocols. In particular, the interest will be on Aloha, CSMA, Ethernet and Token Ring that will be compared in terms of efficiency. A special attention will be devoted to the description of the CSMA/CA protocol adopted by WiFi. Then, the Bianchi’s CSMA/CA analysis will be presented under saturated conditions and compared with other studies that evaluate the CSMA/CA capacity.
3) A survey of the air interface protocol stack for the most important wireless systems, such as: WiFi (in the different versions IEEE 802.11 b/g), the IEEE 802.11e amendment, WiMAX (IEEE 802.16d and IEEE 802.16e), HSPA, and DVB-S2/-RCS. A particular focus will be given on resource management techniques, QoS support and optimization schemes.
4) Cross-layer design for wireless systems. It is more and more important to study the combination of different techniques at different layers as well as to specify and to exploit the information flow across layers. Examples of cross-layer interactions will be provided and the related performance gains will be highlighted referring to some wireless systems.