Opportunistic Access Schemes for Multiuser OFDM Wireless Networks

Bandwidth allocation in next generation broadband wireless networks (4G systems) is a challenging issue. The scheduling shall provide mobile multimedia transmission services with an adequate QoS. These new multimedia services with tight QoS constraints require increased system capacity together with high fairness. The past decades have witnessed intense research efforts on wireless communications. In contrast with wired communications, wireless transmissions are subject to many channel impairments such as path loss, shadowing and multipath fading. These phenomena severely affect the transmission capabilities and in turn the QoS experienced by applications, in terms of data integrity but also in terms of the supplementary delays or packet losses which appear when the effective bit rate at the physical layer is low.