Examinando por Autor "Gatsis, Nikolaos"
Mostrando 1 - 2 de 2
- Resultados por página
- Opciones de ordenación
Ítem Power Control for Cooperative Dynamic Spectrum Access Networks with Diverse QoS Constraints(2009-07-29T13:11:04Z) Gatsis, Nikolaos; Garcia Marques, Antonio; Giannakis, Georgios B.Dynamic spectrum access (DSA) is an integral part of cognitive radio technology aiming at efficient management of the available power and bandwidth resources. The present paper deals with cooperative DSA networks, where collaborating terminals adhere to diverse (maximum and minimum) quality-of-service (QoS) constraints in order to not only effect hierarchies between primary and secondary users but also prevent abusive utilization of the available spectrum. Peer-to-peer networks with co-channel interference are considered in both single- and multi-channel settings. Utilities that are functions of the signal-tointerference- plus-noise-ratio (SINR) are employed as QoS metrics. By adjusting their transmit power, users can mitigate the generated interference and also meet the QoS requirements. A novel formulation accounting for heterogeneous QoS requirements is obtained after introducing a suitable relaxation and recasting a constrained sum-utility maximization as a convex optimization problem. The optimality of the relaxation is established under general conditions. Based on this relaxation, an algorithm for optimal power control that is amenable to distributed implementation is developed, and its convergence is established. Numerical tests verify the analytical claims and demonstrate performance gains relative to existing schemes.Ítem Utility-Based Power Control for Peer-to-Peer Cognitive Radio Networks with Heterogeneous QoS Constraints(2008-04-01T11:42:41Z) Gatsis, Nikolaos; Garcia Marques, Antonio; Giannakis, Georgios B.Transmit-power control is a critical task in cognitive radio (CR)networks. In the present contribution, adherence to hierarchies between primary and secondary users in a peer-to-peer CR network is enabled through distributed power control. Hierarchies are effected by imposing minimum and maximum bounds on a quality-of-service(QoS) metric, such as communication rate.These bounds translate to signal-to-interference-plus-noise ratio (SINR) constraints. Furthermore, a utility function captures each user's satisfaction with the received SINR. The novel power control strategy maximizes the total utility while respecting individual SINR constraints - a task recast as a convex optimization problem under a suitable relaxation. Sufficient conditions, realistic for practical CR networks, are provided to obtain the optimal power allocation from the solution of the relaxed problem. Finally, a low-overhead distributed algorithm for optimal power control is developed, and tested against competing alternatives via simulations.