Análise dos pontos ótimos de comutação em sistemas com modulação adaptativa

Abstract

Due to spectrum scarcity problems in telecommunication networks and the rising de-mand for high transmission rates, several studies are being made in order to increase the network’s performance, so that the quality of service (QoS) can be ensured. A method to improve the network's performance is the usage of adaptive techniques, such as the adap-tive modulation ones, the target of this dissertation. The definition of the optimum switching points between modulations is a key concern in order to use adaptive modulation techniques. In this work, we analyze the influence of the channel model when searching for the optimum switching points in a traditional wire-less communication system, and also for a system which employs the usage of cognitive radios. Three performance criterions were considered: the throughput, the delay, and the power metric. We also analyze the optimum switching points for a system with cognitive radio considering the use of the Slotted Aloha multiple access protocol.