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The last two decades have seen Cognitive Radio (CR) technology as an efficient mechanism to combat spectrum scarcity. Cooperative spectrum sensing (CSS) further enhances its efficiency. However, primary user emulation attack (PUEA) can affect the key purpose of CSS, by changing its fundamental model. This necessitates optimization of the CSS system facing a PUEA. In this paper, such optimization has been performed with the help of Deep Q- Network (DQN) learning. A smart-PUEA strategy, where the attack is made intelligently during the absence of the primary user (PU) signal, has been considered for investigation. First, the presence of a PUEA is modelled with the Markov chain. Then, the suppression of the damages done by the PUEA on the SU throughput has been performed in two CSS architectures: the decision fusion CSS and the data fusion CSS. In both the CSS architectures, the application of DQN learning is carried out by finding an optimal policy with the help of an action-value function. The optimal policy gives the optimal decision threshold and the optimal sensing time. As the data sets for the considered system are large, a multi-layered network is used for approximating the action-value function estimator. The reward is received in terms of maximized SU throughput. The performance assessment is done with an exhaustive search mechanism and beamforming based CSS. It is shown that the proposed algorithms outperform the existing algorithms in terms of the achievable sum-rate and number of iterations for convergence respectively.

Wireless communication systems primarily depend on the availability of bandwidth. Cognitive radio has been realized as an effective means to maximize the bandwidth for internet and other communication applications. Multiple cognitive radios perform spectrum sensing in cooperation to mitigate the effects of fading. A specific number of cooperating cognitive radio users are responsible to form the decision at the fusion center for spectrum occupancy and is called the global decision threshold. In this letter, we find the global threshold which maximizes the throughput of the cognitive radio users while keeping a constraint on the interference to the licensed primary user. It is observed that for every interference value below the constraint, the throughput of the cognitive radio users maximizes at a particular value of the global decision threshold.

The maximization of Secondary user (SU) throughput has been studied extensively in honest cooperative spectrum sensing (CSS). However, when primary user emulation attacks (PUEAs) are launched, the model of CSS changes. This also necessitates the redesigning of the SU throughput maximisation scheme. In this paper, such redesigning of the SU throughput maximisation scheme under PUEAs has been carried out. Our objective is to suppress the damages caused by the PUEAs on the SU throughput. To serve this purpose, an optimally weighted CSS has been proposed. The optimal weights are obtained by maximising the SU throughput while protecting the primary user (PU) from interference in a network facing the PUEAs. Considering the significance of simplicity and speed in CSS, we apply the Nelder Mead Simplex Algorithm to solve the problem. The experiments carried out endorse the effectiveness of the proposed scheme compared to the existing combination schemes.

Cooperative spectrum sensing is prone to attacks by malicious users. These attacks become more severe when launched in collusion. In this paper, a collision penalty based attack prevention method is proposed to defend individual and collusion attacks in all the possible attack scenarios. We identify the possible attack strategies in each scenario and prevent them with appropriate bounds on the collision penalty. Simulation results verify the effectiveness of the proposed scheme.

Mass media including television, internet, and newspapers influences public views about various issues by means of how it covers an issue. Newspapers have a wider reach and may affect the impact that a news story has on the reader by factors such as placement of the story within the different pages. We did a pilot study to see how two English newspapers from Mumbai, India were covering psychiatry related news stories. The study was done over a period of 3 months. We found a total of 870 psychiatry related news stories in the two newspapers over 3 months with the majority of them being covered in the main body of the newspapers. Sex-related crime stories and/or sexual dysfunction stories received the highest coverage among all the news while treatment and/or recovery related stories received very little coverage. It is crucial that the print media takes more efforts in improving reporting of psychiatry-related stories and help in de-stigmatizing psychiatry as a discipline.

Eddy Current braking technique is a classical example of how effective and efficient braking be obtained from application of magnetic field. Eddy current braking is based on the principle of relative motion between a magnetic source and a metal. In this paper, eddy current braking system is modeled in SIMULINK and effects of various parameters are observed over the overall braking. This would provide a comparative study between the various parameters involved and understand the braking system.

The Dixon's outlier detection scheme has recently been applied to suppress a malicious secondary user (SU) in a centralised fusion-based cognitive radio cooperative spectrum sensing system. This study proposes to apply the Dixon's test on the smaller overlapping groups of SUs' energy data, thereby increasing the detection performance particularly for multiple malicious users (MUs). The test is applied for each sample of the energy data. Simulation results demonstrate that the proposed methods are efficient in suppressing single and multiple MUs.

This paper is a commentary on whether doctors have the right to strike work or not while keeping in mind, psychosocial and ethical implications of the same. Certain guidelines and criteria that may be applicable when examining doctors on strike are elucidated and discussed. DOI: http://dx.doi.org/10.3329/bioethics.v5i3.21534 Bangladesh Journal of Bioethics 2014; 5(3):23-25

Advances in information and communication technology have facilitated the development of online psychotherapy. This form of psychotherapy would provide the developing world with better access to professional mental healthcare services. At the same time, it is prudent to carefully consider the various ethical, legal and regulatory issues involved in online psychotherapy. This paper highlights the major ethical issues involved in the use of online psychotherapy, whether conducted via e-mail, chat rooms or interactive video, and identifies practical solutions for the ethical dilemmas that exist. Many authors and organisations have expressed their opinions on the subject, but no consensus has evolved. The advice offered to psychologists is mostly skewed and the scarcity of literature available to those considering expanding their practice to include online psychotherapy is certainly a source of vexation. While reviewing the existing literature, this paper seeks to describe and discuss the major ethical issues in this area, particularly in India, but many of these issues will be equally applicable to any developing world settings.

Spectrum sensing systems affected by Primary User Emulation Attacks (PUEAs) have recently gained focus in research. These attacks occur when a malicious unlicensed transmitter emulates the primary user (PU) signal to misdirect other secondary users (SUs). PUEAs are harmful to individual as well as cooperative spectrum sensing (CSS) systems. In this paper, a CSS model under PUEAs has been considered. A simple weighted combination scheme has been proposed for signal combination at the fusion center (FC). The calculation of weights is aimed to maximize the throughput of the SUs while keeping a limit on the interference to the PU. Simulation results prove the effectiveness of the proposed schemes.