Cognitive radio (CR) is an opportunistic communication technology which is designed to utilize the maximum available licensed bandwidth for unlicensed users. In CR, when the spectrum is not used by primary user, it is accessed by the unlicensed users/secondary users. . In CRN a selfish SU (secondary user) broadcasts faked channel allocation information to other neighboring SUs in order to occup...

In this paper, the performance of cognitive radio (CR) code divisionmultiple access (CDMA) networks is analyzed in the presence of receive beamforming at the base stations (BSs). More precisely, we analyze, through simulations, the performance achievable by a CR user, with and without spectrum sensing, in a three-cell scenario. Uplink communications are considered. Three different schemes for s...

Cognitive Radio (CR) is an emerging technology to solve the spectrum underutilization problems by opens the licensed spectrum bands for opportunistic usage and initiates spectrum trading to improve the spectrum utilization. The path selection problem in multihop cognitive radio networks (CRNs) are investigated below constraints on flow routing, link scheduling and CR source’s budget. Cognitive ...

Cognitive radio as first coined by Mitola [1] in 1999 illustrates a dynamic model that provides human intervention to the underlying radio hardware. Dynamic spectrum access (DSA) is one of the many applications of cognitive radio. The DSA umbrella [2] considers the secondary usage of the spectrum. On these grounds, we meant to design a working prototype for Cognitive Relay (CR), a device that d...

Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrumaware communication paradigm in wireless comm...

Dynamic spectrum access by the unlicensed secondary users (nodes) in the Cognitive Radio Network without harmful (potential) interference to the licensed users is an intelligent and efficient use of the Licensed Spectrum Bands. The nodes in a cognitive radio network(CRN) performs periodic local spectrum sensing & dynamically detects the vacant or unused spectrum around them in the form of free ...

Spectrum sensing is a key enabling functionality in a cognitive radio (CR) network. The fusion problem of cooperative spectrum sensing, for a cognitive radio network equipped with multi-antennas at its base-station, is considered in this paper. The base-station equipped with multi-antennas act as a fusion center which can attain not only the soft information (average power) by its multi-antenna...

This paper analysis performance of energy detection technique for cognitive radio which implies spectrum sensing. Main objective is to reduce interference occur in the cognitive radio systems. Spectrum detection schemes are based on fixed threshold these are sensitive to noise; the energy detection based on dynamic threshold can improve the resistance of noise and get a good performance of dete...

Cognitive radio (CR) is a promising concept for improving the utilization of scarce radio spectrum resources. Orthogonal frequency division multiplexing (OFDM) is regarded as a technology which is well-matched for CR systems. In this paper, it is shown that channel estimation errors can result in a severe performance degradation in a multi-user OFDM CR system. A simple back-off scheme is propos...

One of today’s most important developing wireless technologies is Cognitive Radio (CR). In our current fixed-assignment spectrum management policy, much of the available frequencies go unused. CR aims to make use of this unutilized space to provide wireless broadband services. This paper aims to give a background to CR and describe the key players in standardization and allocation of the unused...