S. Mohammad Razavizadeh

Learn More
It is anticipated that the mobile data traffic will grow 1,000 times higher from 2010 to 2020 with a rate of roughly a factor of two per year. This increasing demand for data in next-generation mobile broadband networks will lead to many challenges for system engineers and service providers. To address these issues and meet the stringent demands in coming(More)
— In this paper, the Filter-and-Forward strategy is developed for cooperative relays in Cognitive Radio networks with underlay structure and frequency selective fading channels. A cost function is defined to minimize the required transmitting power of the relay networks and the secondary user. This is performed subject to keeping the power of noise and(More)
— A cognitive radio (CR) network is a secondary network operating in the frequency band and geographical area of a primary network to which the spectrum is licensed. In this paper, we consider a primary broadcasting network consisting of a transmitter and a number of primary users (PUs). The secondary users (SUs) make opportunistic unlicensed spectrum(More)
—Most of the beamforming designs that have been proposed in literature for relay networks often assume flat fading channels with perfect channel state information. However, in practice, the channel is likely to be frequency selective. On the other hand, in many cases, having the perfect channel state information is impossible. In this paper, we investigate(More)
—We consider uplink transmission of a massive multiuser multiple-input multiple-output (MU-MIMO) system in the presence of a smart jammer. The jammer aims to degrade the sum spectral efficiency of the legitimate system by attacking both the training and data transmission phases. First, we derive a closed-form expression for the sum spectral efficiency by(More)
Distributed power control by beamforming approach in cognitive radio networks requires a precise analysis of the impacts of the transmission parameters, tolerable interference and guarantees the quality of service of both the primary users and secondary users. In this paper, we propose an improved performance to solve the constrained nonlinear multi-object(More)
The two main problems in cognitive radio networks are power and time slot allocation problems which require a precise analysis and guarantee the quality of service in both the primary and secondary users. In this paper, these two problems are considered and a method is proposed to solve the resulting optimization problem. Our proposed method provides an(More)
In this paper, we develop an approach to allow the cog-nitive radio to operate in the presence of the licensed user using bio-inspired method called particle swarm optimization. This method is invoked to solve the constrained nonlinear optimization problem for the minimum power transmission and minimum bit error rate in order to reach to maximum capacity.(More)