Impact of Primary Interference on Secrecy Performance of Physical Layer Security in Cognitive Radio Networks

Wireless Personal Communications - In cognitive radio networks (CRNs), primary interference is either neglected or considered as an additive white Gaussian random variable (r.v.). Current...     

Exact Outage Probability of Underlay Cognitive Cooperative Networks Over Rayleigh Fading Channels

Our contribution in this paper is the derivation of an exact closed-form outage probability formula for underlay cognitive cooperative networks operated over Rayleigh fading channels. The derivation considers the correlation among received signal-to-noise ratios, two critical constraints (interference power constraint and maximum transmit power constraint), and non identically distributed (i.d.) channels. The derived formula is corroborated by Monte Carlo simulations and is served as an useful and effective tool to evaluate the performance behavior of underlay cognitive cooperative networks without time-consuming simulations under different operation parameters. Numerical results illustrate that underlay cognitive cooperative networks suffer the outage saturation phenomenon for a given maximum interference power level.     

Performance Analysis of Cooperative Underlay Cognitive Networks with Channel Estimation Error

Channel information (CI) plays an important role in system design optimization. It is obtained through channel estimation process and hence, inevitably imperfect at a certain degree. Numerical evaluation of the outage performance of cooperative underlay cognitive networks under the presence of channel estimation error has been left open. This paper heals this literature gap with the proposal of a precise outage probability expression. Various results show the excellent match between analysis and simulation, and the advantage of the derived expression in studying the effect of CI imperfection on system performance.     

Crystallization Mechanisms and Rates of Cyclopentane Hydrates Formation in Brine

Clathrate hydrates most often grow at the interface between liquid water and another fluid phase (hydrocarbon) acting as a provider for the hydrate guest molecules, and some transfer through this shell is required for the hydrate growth to proceed, thus self‐limiting the reaction rate. An optical microscope and a horizontal reaction cell are utilized to capture the shell growth phenomenology and to estimate the hydrate layer growth rates from sequential pictures. Cyclopentane (CP) is chosen as the hydrate‐forming molecule to obtain hydrates at low pressure. Experimental hydrate layer growth rates are provided for the CP+brine system, using various combinations of salts and degrees of subcooling.     

On the performance of cooperative cognitive networks with proactive relay selection

This paper provides a general outage analysis framework for cooperative cognitive networks with proactive relay selection over non-identical Rayleigh fading channels and under both maximum transmit power and interference power constraints. We firstly propose an exact closed-form outage probability expression, which is then exploited for determining the diversity order and coding gain for proactive relay selection scenarios as well as deriving system performance limits at either large maximum transmit power or large maximum interference power. The derived performance metrics bring several insights into system performance behavior without the need of time-consuming Monte-Carlo simulations. Various results confirm the validity of the proposed derivations and show that cooperative cognitive networks with proactive relay selection incur performance saturation and their performance depends considerably on the number of involved relays. In addition, cooperative cognitive networks are significantly better than dual-hop counterparts without any cost of system resources.     

Performance Evaluation of Underlay Cognitive Multi-hop Networks Over Nakagami-m Fading Channels

We derive a closed-form bit error rate (BER) formula for underlay cognitive N-hop networks operated over Nakagami-m fading channels where N is the arbitrary integer. This formula is corroborated by Monte Carlo simulations and useful for evaluating the network performance under different parameters such as modulation level, path-loss, maximum transmit power, tolerable interference power level, fading model, and the number of hops. Numerical results illustrate that underlay cognitive multi-hop networks suffer a high error floor and the BER performance not only depends on the number of hops but also the network topology. For the linear network model, the higher the number of hops, the better the network performance.     

Reliability-Intercept Gap Analysis of Underlay Cognitive Networks Under Artificial Noise and Primary Interference

Wireless Personal Communications - Underlay mode of cognitive radio networks (CRNs) permits secondary users (SUs) to simultaneously operate with primary users (PUs), inducing mutual interference...     

Spectrum Sharing Paradigm Under Primary Interference and Nakagami-m Fading: Security Analysis

Wireless Personal Communications - The spectrum sharing paradigm is a promising countermeasure to the spectrum under-utilization problem. However, it causes both primary interference (inflicted by...     

Adaptive processing in overlay networks for performance improvement

Wireless Networks - This paper proposes an overlay network wherein a pair of licensed source (LS) and licensed destination (LD) is adaptively assisted by a pair of unlicensed source (US) and...     

Energy harvesting cognitive radio networks: security analysis for Nakagami-m fading

Energy harvesting has lately been of particular attention to researchers. In addition, cognitive radio networks (CRNs) are recognized as an attainable measure for the problem of radio spectrum shortage in next generation radio access. A combination of these two technologies, which forms energy harvesting CRNs (EHCRNs), allows wireless communication terminals to prolong their operation time in limited spectrum scenarios. Nonetheless, that CRNs create opportunities for secondary users to access primary users’ spectrum induces vulnerability of message security. So far, security capability analysis of EHCRNs has been limited to Rayleigh fading whilst Nakagami-m fading is more common than Rayleigh fading and better reflects distinct fading severity degrees in practical scenarios. Accordingly, this paper firstly offers the precise security capability analysis of EHCRNs under interference power constraint, Nakagami-m fading, maximum transmit power constraint, and primary interference. Then, the offered analysis is ratified by computer simulations. Ultimately, multiple results reveal that the security capability is considerably improved with smaller primary interference and lower required security threshold. Moreover, the security capability is significantly impacted by channel severity and is optimized with appropriate selection of time percentage.