Selecting users in energy-efficient collaborative spectrum sensing

Cognitive radio network is defined as an intelligent wireless communication network that should be able to adaptively reconfigure its communication parameters to meet the demands of the transmission network or the user. In this context one possible way to utilize unused licensed spectrum without interfering with incumbent users is through spectrum sensing. Due to channel uncertainties, single cognitive (opportunistic) user cannot make a decision reliably and hence collaboration among multiple users is often required. Here collaboration among large number of users tends to increase power consumption and introduces large communication overheads. In this paper, the number of collaborating users is optimized in order to maximize the probability of detection for any given power budget in a cognitive radio network, while satisfying constraints on the false alarm probability. We show that for the maximum probability of detection, collaboration of only a subset of available opportunistic users is required. The robustness of our proposed spectrum sensing algorithm is also examined under flat Rayleigh fading and AWGN channel conditions.

Spectrum efficient cooperative relaying based on outage-multiplexing tradeoff analysis.

Spectrum efficient multiple relay selection strategy for two-hop cooperative decode-and-forward relay networks is proposed for the case when the sum power among all relay nodes is limited. Based on the outage-multiplexing tradeoff (OMT), the number of active relay nodes is maximized so that the resulting sum-relay capacity is maximized while each relay outage capacity remains greater than or equal to a certain target level. Using asymptotic analysis, it is shown that for the proposed OMT relaying strategy the associated multiplexing and cooperative system diversity gains improve proportionally with the number of active relay nodes. It is also shown analytically that the proposed OMT relaying outperforms the conventional opportunistic single relaying in terms of the sum-relay capacity.

Mitigating Cross-Network Interference in Cognitive Spectrum Sharing with Opportunistic Relaying

We examine the impact of primary and secondary interference on opportunistic relaying in cognitive spectrum sharing networks. In particular, new closed-form exact and asymptotic expressions for the outage probability of cognitive opportunistic relaying are derived over Rayleigh and Nakagami-m fading channels. Our analysis presents revealing insights into the diversity and array gains, diversity-multiplexing tradeoff, impact of primary transceivers' positions, and the optimal position of relays. We highlight that cognitive opportunistic relaying achieves the full diversity gain which is a product of the number of relays and the minimum Nakagami-m fading parameter in the secondary network. Furthermore, we confirm that the diversity gain reduces to zero when the peak interference constraint in the secondary network is proportional to the interference power from the primary network.

Parents' experiences of applied behaviour analysis (ABA)-based interventions for children diagnosed with autistic spectrum disorder

Applied behaviour analysis (ABA)-based programmes are endorsed as the gold standard for treatment of children with autistic spectrum disorder (ASD) in most of North America. This is not the case in most of Europe, where instead a non-specified 'eclectic' approach is adopted. We explored the social validity of ABA-based interventions with 15 European families who had experience with home-based, mainly self-managed, ABA-based programmes for their own child/ren with ASD. The results of the study highlighted the overwhelmingly positive impact that ABA-based interventions had on their children in areas such as social skills, challenging behaviour, communication, gross and fine motor skills, concentration, interaction, independence, overall quality of life and, most importantly, a feeling of hope for the future. Implications for European policy on ASD are discussed. © 2013 NASEN.

Lost in translation: Public policies, evidence-based practice, and Autism Spectrum Disorder

Prevalence rates of autism spectrum disorder have risen dramatically over the past few decades (now estimated at 1:50 children). The estimated total annual cost to the public purse in the United States is US$137 billion, with an individual lifetime cost in the United Kingdom estimated at between £0.8 million and £1.23 million depending on the level of functioning. The United Nations Convention for the Rights of Persons with Disabilities has enshrined full and equal human rights—for example, for inclusion, education and employment—and there is ample evidence that much can be achieved through adequate support and early intensive behavioural interventions. Not surprisingly, most governments worldwide have devised laws, policies, and strategies to improve services related to autism spectrum disorder, yet intriguingly the approaches differ considerably across the globe. Using Northern Ireland as a case in point, we look at relevant governmental documents and offer international comparisons that illustrate inconsistencies akin to a “postcode lottery” of services.

Causal Models of Clinically Significant Behaviors in Angelman, Cornelia de Lange, Prader-Willi and Smith-Magenis Syndromes

The operant learning theory account of behaviors of clinical significance in people with intellectual disability (ID) has dominated the field for nearly 50 years. However, in the last two decades, there has been a substantial increase in published research that describes the behavioral phenotypes of genetic disorders and shows that behaviors such as self-injury and aggression are more common in some syndromes than might be expected given group characteristics. These cross-syndrome differences in prevalence warrant explanation, not least because this observation challenges an exclusively operant learning theory account. To explore this possible conflict between theoretical account and empirical observation, we describe the genetic cause and physical, social, cognitive and behavioral phenotypes of four disorders associated with ID (Angleman, Cornelia de Lange, Prader-Willi and Smith-Magenis syndromes) and focus on the behaviors of clinical significance in each syndrome. For each syndrome we then describe a model of the interactions between physical characteristics, cognitive and motivational endophenotypes and environmental factors (including operant reinforcement) to account for the resultant behavioral phenotype. In each syndrome it is possible to identify pathways from gene to physical phenotype to cognitive or motivational endophenotype to behavior to environment and back to behavior. We identify the implications of these models for responsive and early intervention and the challenges for research in this area. We identify a pressing need for meaningful dialog between different disciplines to construct better informed models that can incorporate all relevant and robust empirical evidence.

Wireless Energy Harvesting and Spectrum Sharing in Cognitive Radio

A wireless energy harvesting protocol is proposed for a decode-and-forward relay- assisted secondary user (SU) network in a cognitive spectrum sharing paradigm. An expression for the outage probability of the relay-assisted cognitive network is derived subject to the following power constraints: 1) the maximum power that the source and the relay in the SU network can transmit from the harvested energy, 2) the peak interference power from the source and the relay in the SU network at the primary user (PU) network, and 3) the interference power of the PU network at the relay-assisted SU network. The results show that as the energy harvesting conversion efficiency improves, the relay- assisted network with the proposed wireless energy harvesting protocol can operate with outage probabilities below 20% for some practical applications.

How to measure the micromaser spectrum in the trapping state regime

We show how our recently proposed scheme for the measurement of the micromaser linewidth, which relates the phase diffusion dynamics of the cavity field to the population statistics of probe atoms, can be applied in the presence of trapping states, where the phase diffusion approximation does not strictly hold. This should allow the observation of the peculiar linewidth oscillations versus atomic pumping which are expected in this regime, and whose origin lies in the quantum nature of the cavity field.

Micromaser spectrum and phase diffusion dynamics

We discuss a scheme to relate the phase diffusion dynamics of the micromaser field to the measured atomic population statistics. This can allow us to measure the linewidth of the micromaser spectrum and to solve a relevant decoherence problem in cavity quantum electrodynamics. The main steps are (i) a suitable preparation of the cavity field state to generate coherences, (ii) the transfer of information on the dynamics of field coherences to probe atoms by the action of an external resonant coherent field and (iii) the derivation of the phase diffusion rate, hence the micromaser linewidth, from the measured population statistics of the probe atoms. The method can be applied even in the presence of trapping states, where peculiar linewidth oscillations are expected for increasing pump rate, due to the quantum nature of the micromaser field.

The effect of choice on motivation for young children on the autism spectrum during discrete trial teaching

Self-determination and decision-making are acknowledged internationally as key rights of persons with disabilities and should play an important role in the development of educational plans and procedures. Not only is the chance for individuals with developmental disabilities to select their own tasks, leisure activities or reinforcers a valuable way of enhancing rights-based education and personal dignity, but choice-making opportunities may also function as a useful clinical or educational tool if they actually improve the efficacy of programmes aimed at the acquisition of socially relevant behaviours and life skills or the reduction of challenging behaviours.

The study reported here assessed whether or not choice affected effectiveness of an educational procedure for three children on the autism spectrum. Following a preference assessment, a number of discrete teaching trials were conducted with each child and, contingent upon targeted responses, either the child or the therapist selected one of three preferred reinforcer items. Reinforcer choice did not affect intervention effectiveness for two of the children; however, performance and motivation improved for the third child. Results re-affirmed the importance of thorough preference assessments prior to intervention and showed that additional stimulus choice contingent on the target response may improve motivation and outcomes for some children.

Creating an Inclusive Society… How Close are We in Relation to Autism Spectrum Disorder? A General Population Survey

BackgroundChildren with autism spectrum disorder are increasingly educated in mainstream classrooms in the United Kingdom (Wilkinson & Twist, Autism and Educational Assessment: UK Policy and Practice. NFER, Slough, 2010), and some employers are now specifically seeking out staff on the autism spectrum. Does that mean that we are living in an inclusive society' [United Nations Department of Economic and Social Affairs (UNDESA), Creating an Inclusive Society: Practical Strategies to Promote Social Integration 2008], in the sense that inequalities are reduced and full economic, social and cultural participation is advanced for individuals with autism?

MethodsA general population survey was conducted to assess how close we, as a society, are to an inclusive society for individuals with autism in Northern Ireland. Public attitudes were examined to (i) visibility and social interaction, (ii) aetiology, needs and interventions, and (iii) rights and resources.

ResultsA stratified, representative sample of 1204 adults took part in the survey; of these, 989 were aware of autism and their attitudes and behavioural projections reflected a mix of acceptance and denunciation. The level of confusion with regard to interventions reflected the general uncertainty within UK policy regarding meeting the needs of individuals on the autism spectrum (International Journal of Disability, Development and Education 61, 134, 2014a).

ConclusionTherefore, it seems that inclusion is working to an extent, but more clarity is needed with regard to adequate education, intervention and support for individuals with autism.

Feleucin-BO1: A Novel Antimicrobial Non-Apeptide Amide from the Skin Secretion of the Toad, Bombina orientalis, and Design of a Potent Broad-Spectrum Synthetic Analogue, Feleucin-K3

Feleucins-BV1 and -BV2 are recently-described prototypes of a novel antimicrobial nonapeptide (AMP) family identified in the skin secretion of the bombinid toad, Bombina variegata. They are encoded on different precursors that also encode a novel bombinin. Here we describe the identification of feleucin-BO1 (FLGLLGSLLamide) which is co-encoded with a different novel bombinin, named feleucin precursor-associated bombinin (FPA-bombinin-BO), from the skin secretion of Bombina orientalis. Synthetic feleucin-BO1 displayed activity against a reference Gram-positive bacterium. Staphylococcus aureus (MIC 34 μM) but was inactive (> 250 μM) against the Gram-negative bacterium, Escherichia coli, and the yeast, Candida albicans. This pattern of activity was similar to that of the prototypes. Design and synthesis of a cationicity-enhanced analogue, feleucin-K3 (F-K3), in which the amino acid residues at positions 3 (G), 6 (G) and 7 (S) of feleucin-BO1 were substituted with Lys (K) residues, resulted in a peptide with significantly-enhanced potency and spectrum of activity. The MICs of F-K3 against the reference microorganisms were 7 μM (S. aureus), 14 μM (E. coli) and 7 μM (C. albicans). These data indicate that the skin secretions of amphibians can continue to provide novel peptide templates for the rational design of analogues with possible therapeutic utility.

Opportunistic spectrum aggregation for cognitive communications under collision constraints

We consider a collision-sensitive secondary system that intends to opportunistically aggregate and utilize spectrum of a primary system to achieve higher data rates. In such opportunistic spectrum access, secondary transmission can collide with primary transmission. When the secondary system aggregates more channels for data transmission, more frequent collisions may occur, limiting the performance obtained by the opportunistic spectrum aggregation. In this context, dynamic spectrum aggregation problem is formulated to maximize the ergodic channel capacity under the constraint of collision tolerable level. To solve the problem, we develop the optimal spectrum aggregation approach, deriving closed-form expressions for the collision probability in terms of primary user traffic load, secondary user transmission interval, and the random number of sub-channels aggregated. Our results show that aggregating only a subset of sub-channels will be a better choice, depending on the ratio of collision sensitivity requirement to the primary user traffic.

Interference Investigation for Cognitive Spectrum Sharing Networks with Reactive DF Relay Selection

Cognitive radio (CR) with spectrum-sharing has been envisioned as emerging technology for the next generation of mobile and wireless networks by allowing the unlicensed customers simultaneously utilize the licensed radio frequency spectrums. However, the CR has faced some practical challenges due to its deduced system performance as compared to non spectrum-sharing counterpart. In this paper, we therefore consider the potential of incorporating the cooperative communications into CR by introducing the concept of reactive multiple decode-and-forward (DF) relays. In particular, we derive new results for exact and asymptotic expressions for the performance of cognitive relay networks with K-th best relay selection. Our novel results have exhibited the significance of using relay networks to enhance the system performance of CR.