Cognitive Radio Network

In emerging cognitive radio (CR) networks, the first cognitive task preceding any dynamic spectrum management is the sensing and identification of spectrum holes in wireless environments. This paper develops a distributed compressed spectrum sensing approach for (ultra-)wideband CR networks. First, compressive sampling is performed at local CRs to scan the very wide spectrum at practical signal-acquisition complexity. Then, measurements or states from multiple CR detectors are fused to collect spatial diversity gain, which improves the detection quality especially under fading channels. Distributed fusion algorithms are derived to effect collaborative fusion at low communication and computation load scalable to the network size. Multiple performance metrics are identified to evaluate the proposed spectrum sensing techniques, as well as to assess those performance-determining factors in system design. Computer simulations corroborate the effectiveness of the proposed techniques in id...

A scenario is presented in spectrum sensing for Cognitive Radio Networks based on energy detectors. Results are presented for the performance of the energy detector based on Welch periodogram. The effect of the number of signal samples and the time domain window function are demonstrated for low Signal-to-Noise Ratio values. Furthermore, the detector performance is linked to a general probabilistic scheme for sensing algorithms. Important system issues such as receiver feedback and cooperative spectrum sensing are included in this framework. Parametric computations of the probability of correct decision are presented to show the detrimental effect of the hidden node problem in a simple collaborative spectrum sensing scheme.

In this paper, we present an analytical model as well as a practical mechanism to detect denial of service (DoS) attacks on secondary users in dynamic spectrum access (DSA) networks. In particular, we analyze primary user emulation attacks (PUEA) in cognitive radio networks without using any location information and therefore can do away with dedicated sensor networks. We present an analysis using Fenton's approximation and Wald's sequential probability ratio test (WSPRT) to detect PUEA. Simulation results demonstrate that it is possible to keep the probability of success of PUEA low, while still keeping the probability of missing the return of the primary low as well.

Cognitive radio (CR) technology is an innovative radio design philosophy in order to increase the spectrum utilization by exploiting the unused spectrum in dynamically changing environments. Specifically, the CR technology will allow a group of potential users (referred to as secondary users) to access available spectrum resources unused by primary users (PUs) for whom the band has been licensed. The spectrum available for secondary users (SUs) depends on PUs' activity in the licensed spectrum. In this paper, we develop a queuing analytic framework to study important performance measures experienced by SUs in a CR network. We study queuing delay and buffer statistics of SUs' packets by modeling PUs' activity as a two state Markov chain and SUs' channel quality variation as a finite state Markov chain (FSMC). In order to allocate available channels among the SUs, an opportunistic channel allocation scheme is considered. The proposed framework facilitates to design an admission controller for SUs' network in order to maintain a given quality service (QoS) requirement which is specified in the form of statistical delay guarantee.

In this paper, we propose a novel simple heuristic algorithm for scheduling the secondary link activation and provide a dynamic spectrum sharing in cognitive radio networks. This algorithm is presented for spectrum underlay where primary and secondary users transmit simultaneously on the same frequency bands in cognitive radio networks. The proposed algorithm is based on a graph-theoretical model. First, the

The paper examines contemporary issues with cognitive radio networks as it relates to spectrum scarcity and the demand of users. With recent advancement in technology and increase in the need for wireless communication systems, this has given rise to the search for desirable spectrum bands for transmission. Cognitive Radios renders an answer to the trouble by sensing the idle (licensed) bands and allowing (secondary) users to broadcast and transmit in these idle spaces. Spectrum sensing forms the main block of cognition cycle. However, research has shown by previous researchers that radio spectrums are being under-utilized in most cases. This paper attempts to profound a solution to efficient and effective spectrum utilization has identified the current challenges and issues faced by spectrum sensing for cognitive networks. The principal issues with cognitive radios are that it should not interfere with the primary users and should vacate the band when it is required. For this sole reason, energy detector system model was used in this paper and performance evaluation was calculated. The performance evaluation is done for cooperative spectrum sensing schemes under non-fading environment This paper provides a clear understanding of cognitive radio technology and its role in national development. Then several challenges and security issues are discussed.