Vahid Asghari

Learn More
In this paper, we derive closed-form expressions for the average symbol error probability (SEP) of arbitrary rectangular I X J-ary quadrature amplitude modulation (QAM) in cooperative amplify-and-forward (A&F) relaying systems, when no direct line-of-sight exists between the source and the destination nodes and when the links(More)
Cognitive radio technology offers tremendous potential to improve the utilization of the radio spectrum by efficiently reusing and sharing the licensed spectrum bands, as long as the interference power inflicted on the primary users of the band remains below a predefined threshold level. In this paper, we investigate the outage capacity gains offered by(More)
In this paper, we use a distributed Zero Forcing Beamforming (ZFB) method in cognitive radio relay networks in an effort to enhance the spectrum efficiency and improve the performance of the cognitive (secondary) system. In particular, we consider a spectrum sharing system where a set of decode-and-forward (DF) relays are employed to help a pair of(More)
In this paper, we use a distributed beamforming method in cognitive radio relay networks in an effort to enhance the spectrum efficiency and improve the performance of the cognitive (secondary) system. In particular, we consider a spectrum sharing system where a set of potential relays are employed to help a pair of secondary users in the presence of a(More)
We consider a dual-hop cooperative spectrum-sharing system with multiple relays that are available to opportunistically help the secondary communication system. In this primary/secondary cooperative system, we propose using a reactive relay selection (RRS) technique at the secondary system in which the best relay is chosen based on both the first and second(More)