The Information technology has evolved enormously during these last twenty years. Progress has been achieved in two major axes: wireless systems and Internet. Wireless systems have become popular due to their offer of ubiquitous services to end users. Internet, on the other hand, owes its popularity to the fact that it offers a common interface to higher layer protocols over a wide range of communication links. As a result, it is rational to investigate the implications of combining these two technologies in order to enable users to have access to Internet in wireless environments. Current cellular systems can not meet the QoS demands of multimedia applications due to their low data rates.
In this dissertation, we first examine how we can bring IP traffic in wireless networks. We present a complete description of a wireless IP access network bringing IP applications to mobile terminals. The system provides a short range high data rate wireless access to IP. We focus on three issues namely QoS support, mobility support and multicast support in the access network. We provide a framework as well as a mechanism for the access network to support each of these design objectives.
Wireless links suffer from high error rate and low bandwidth capacity. As a result, the QoS support mechanisms will not work efficiently unless coupled with appropriate error control protocols. We investigate the use of different error control protocols and different coding parameters in order to control QoS at the access network. We present several numerical results in terms of several QoS metrics for different error control mechanims. These numerical results show that the use of FEC can improve the performance of the error control mechanism in most cases but choosing a code that can perform efficiently in all channel conditions and for any number of wireless receivers is a difficult task. Therefore, an efficient error control protocol must be able to change its coding parameters dynamically.
We propose an adaptive QoS-based error control mechanism. The protocol predicts the evolution of the channel conditions of each receiver. Based on this
prediction and the QoS requirements of the receivers, it changes its error control strategy as well as its coding parameters. Simulation results compare
the performance of our proposed adaptive error control protocol with fixed error control protocols. In general, we observe that our adaptive protocol reduces the
bandwidth utilization while respecting the QoS requirements of the receivers.
