Cooperative Secure Transmission by Exploiting Social Ties in Random Networks

Social awareness and social ties are becoming increasingly popular with emerging mobile and handheld devices. Social trust degree describing the strength of the social ties has drawn lots of research interests in many fields in wireless communications, such as resource sharing, cooperative communication and so on. In this paper, we propose a hybrid cooperative beamforming and jamming scheme to secure communication based on the social trust degree under a stochastic geometry framework. The friendly nodes are categorized into relays and jammers according to their locations and social trust degrees with the source node. We aim to analyze the involved connection outage probability (COP) and secrecy outage probability (SOP) of the performance in the networks. To achieve this target, we propose a double Gamma ratio (DGR) approach through Gamma approximation. Based on this, the COP and SOP are tractably obtained in closed-form. We further consider the SOP in the presence of Poisson Point Process (PPP) distributed eavesdroppers and derive an upper bound. The simulation results verify our theoretical findings, and validate that the social trust degree has dramatic influences on the security performance in the networks.Comment: 30 pages, 11 figures, to be published in IEEE Transactions on Communication

Mammography screening: views from women and primary care physicians in Crete

Background: Breast cancer is the most commonly diagnosed cancer among women and a leading cause of death from cancer in women in Europe. Although breast cancer incidence is on the rise worldwide, breast cancer mortality over the past 25 years has been stable or decreasing in some countries and a fall in breast cancer mortality rates in most European countries in the 1990s was reported by several studies, in contrast, in Greece have not reported these favourable trends. In Greece, the age-standardised incidence and mortality rate for breast cancer per 100.000 in 2006 was 81,8 and 21,7 and although it is lower than most other countries in Europe, the fall in breast cancer mortality that observed has not been as great as in other European countries. There is no national strategy for screening in this country. This study reports on the use of mammography among middleaged women in rural Crete and investigates barriers to mammography screening encountered by women and their primary care physicians. Methods: Design: Semi-structured individual interviews. Setting and participants: Thirty women between 45–65 years of age, with a mean age of 54,6 years, and standard deviation 6,8 from rural areas of Crete and 28 qualified primary care physicians, with a mean age of 44,7 years and standard deviation 7,0 serving this rural population. Main outcome measure: Qualitative thematic analysis. Results: Most women identified several reasons for not using mammography. These included poor knowledge of the benefits and indications for mammography screening, fear of pain during the procedure, fear of a serious diagnosis, embarrassment, stress while anticipating the results, cost and lack of physician recommendation. Physicians identified difficulties in scheduling an appointment as one reason women did not use mammography and both women and physicians identified distance from the screening site, transportation problems and the absence of symptoms as reasons for non-use. Conclusion: Women are inhibited from participating in mammography screening in rural Crete. The provision of more accessible screening services may improve this. However physician recommendation is important in overcoming women's inhibitions. Primary care physicians serving rural areas need to be aware of barriers preventing women from attending mammography screening and provide women with information and advice in a sensitive way so women can make informed decisions regarding breast caner screening

Cellular Automata Applications in Shortest Path Problem

Cellular Automata (CAs) are computational models that can capture the essential features of systems in which global behavior emerges from the collective effect of simple components, which interact locally. During the last decades, CAs have been extensively used for mimicking several natural processes and systems to find fine solutions in many complex hard to solve computer science and engineering problems. Among them, the shortest path problem is one of the most pronounced and highly studied problems that scientists have been trying to tackle by using a plethora of methodologies and even unconventional approaches. The proposed solutions are mainly justified by their ability to provide a correct solution in a better time complexity than the renowned Dijkstra's algorithm. Although there is a wide variety regarding the algorithmic complexity of the algorithms suggested, spanning from simplistic graph traversal algorithms to complex nature inspired and bio-mimicking algorithms, in this chapter we focus on the successful application of CAs to shortest path problem as found in various diverse disciplines like computer science, swarm robotics, computer networks, decision science and biomimicking of biological organisms' behaviour. In particular, an introduction on the first CA-based algorithm tackling the shortest path problem is provided in detail. After the short presentation of shortest path algorithms arriving from the relaxization of the CAs principles, the application of the CA-based shortest path definition on the coordinated motion of swarm robotics is also introduced. Moreover, the CA based application of shortest path finding in computer networks is presented in brief. Finally, a CA that models exactly the behavior of a biological organism, namely the Physarum's behavior, finding the minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From software to wetware. Springer, 201

Euro+Med-Checklist Notulae, 14

Abstract: This is the fourteenth of a series of miscellaneous contributions, by various authors, where hitherto unpublished data relevant to both the Med-Checklist and the Euro+Med (or Sisyphus) projects are presented. This instalment deals with the families Apocynaceae, Compositae, Crassulaceae, Cyperaceae, Euphorbiaceae, Gramineae, Leguminosae, Nyctaginaceae, Onagraceae, Orobanchaceae, Rubiaceae, Solanaceae and Umbelliferae. It includes new country and area records and taxonomic and distributional considerations for taxa in Acalypha, Bupleurum, Carex, Datura, Epilobium, Eragrostis, Galium, Leontodon, Mirabilis, Nerium, Orobanche, Phelipanche, Rhinanthus, Saccharum, Sedum, Trifolium, Tripleurospermum and Willemetia. Citation For the whole article: Raab-Straube E. von & Raus Th. (ed.) 2021: Euro+Med-Checklist Notulae, 14.-Willdenowia 51: 355-369. For a single contribution (example): Bergmeier E. 2021: Leontodon longirostris (Finch & P. D. Sell) Talavera-Pp. 356-357 in: Raab-Straube E. von & Raus Th. (ed.), Euro+Med-Checklist Notulae, 14.-Willdenowia 51: 355-369. https://doi.org/10.3372/wi.51.51304 Version of record first published online on 30 November 2021 ahead of inclusion in December 2021 issue

Plant community attributes affect dry grassland orchid establishment

Several factors have been taken into account to explain the distribution of orchid species. We explored the extent to which plant community attributes affect the abundance and reproductive fitness of three orchid species (Anacamptis morio, Himantoglossum adriaticum and Ophrys sphegodes), native to dry grasslands. Structural attributes of plant community (e.g. cover and height) were assessed in ninety 4 m(2) plots scattered on three hill massifs of the Veneto Region (NE Italy). For the three target orchid species, the height of the flowering stalk, the relative ramet height and the number of flowers and fruits were recorded in 203 tagged ramets. Generalized Linear Model revealed that plant community attributes such as cover and height of the herb layer exert a negative effect on the abundance of orchid populations. Furthermore, regression models indicated that O. sphegodes and H. adriaticum reproductive fitness, determined as fruit/flower ratio, was positively affected by relative ramet height. Our results revealed that local herbaceous vegetation structure influences the cover and fruit set of target orchid species. However, there can be substantial variation in the response of different species and variation in the structural attributes of surrounding vegetation may be associated with differences in the strength of selection. In order to achieve effective results in orchid species conservation, protocols for the in situ conservation must detail the range of vegetation covers and heights at which orchid species are favoured and can produce the most effective inflorescences

Outage probability and ergodic capacity of free-space optical links over strong turbulence

The performance of a free-space optical (FSO) communication system under strong turbulence regime that follows the K distribution is evaluated. Some useful channel statistics are derived in closed form and the outage probability and ergodic capacity for a single-input single-output FSO link are evaluated. Numerical examples are further presented to verify the accuracy of the derived mathematical expressions

Performance of FSO links under exponentiated Weibull turbulence fading with misalignment errors

The exponentiated Weibull (EW) distribution has been recently proposed for the modelling of free-space optical (FSO) links in the presence of finite sized receiver aperture. In this paper, the performance of FSO communication systems over EW is studied. Specifically, the probability density function (PDF) and cumulative distribution function (CDF) of the instantaneous signal-to-noise ratio (SNR), over EW turbulence fading, are studied. The derived statistics of the SNR is utilized to analyse the performance of an FSO communication system over a generalized communication environment with turbulence induced fading, misalignment errors and path loss. New expression for the outage probability is obtained, and exact expressions for the average bit error rate (BER) are derived for various binary modulation schemes. Finally, the obtained analytical results are verified via Monte Carlo simulations

Broadcast Cognitive Radio with Dirty Paper Coding over Nakagami-m Fading Channel

The symbol error rate (SER) performance analysis of a broadcast underlay cognitive radio (CR) network, under Nakagami-m fading channels is studied in this paper. Particularly, the underlay CR network is studied as a closed loop multiple antenna system, presented with dirty paper coding (DPC) approach with the aim to allowing the secondary user (SU) transmission to utilize the spectrum resources efficiently and avoid interference to the primary user (PU) receiver. The proposed approach is capable of achieving the same performance as that of the zero-forcing (ZF) algorithm over Nakagami-m fading channels at the SU receiver. We further show with the simulation results that the SER and bit error rate (BER) performances of the PU under Nakagami-m and Rician fading channels are significantly improved for the proposed study. Finally, we optimize the power allocation of the PU transmitter and approximately achieve 3 dB performance gain over Nakagami-m fading for the SU receiver

Error-rate performance analysis of cooperative OFDMA system with decode-and-forward relaying

Due to copyright restrictions, the access to the full text of this article is only available via subscription.In this paper, we investigate the performance of a cooperative orthogonal frequency-division multiple-access (OFDMA) system with decode-and-forward (DaF) relaying. Specifically, we derive a closed-form approximate symbol-error-rate expression and analyze the achievable diversity orders. Depending on the relay location, a diversity order up to (L-SkD + 1) + Sigma(M)(m=1) min(L-SkRm + 1, L-RmD + 1) is available, where M is the number of relays, and L-SkD + 1, L-SkRm + 1, and L-RmD + 1 are the lengths of channel impulse responses of source-to-destination, source-to-mth relay, and mth relay-to-destination links, respectively. Monte Carlo simulation results are also presented to confirm the analytical findings

Error-rate performance analysis of cooperative OFDMA system with decode-and-forward relaying

Due to copyright restrictions, the access to the full text of this article is only available via subscription.In this paper, we investigate the performance of a cooperative orthogonal frequency-division multiple-access (OFDMA) system with decode-and-forward (DaF) relaying. Specifically, we derive a closed-form approximate symbol-error-rate expression and analyze the achievable diversity orders. Depending on the relay location, a diversity order up to (L-SkD + 1) + Sigma(M)(m=1) min(L-SkRm + 1, L-RmD + 1) is available, where M is the number of relays, and L-SkD + 1, L-SkRm + 1, and L-RmD + 1 are the lengths of channel impulse responses of source-to-destination, source-to-mth relay, and mth relay-to-destination links, respectively. Monte Carlo simulation results are also presented to confirm the analytical findings