Developing high data rate systems to meet the requirements of fifth generation mobile systems has become crucial. Hybrid radio frequency/visible light communication (RF/VLC) has appeared as a promising mechanism for achieving this objective. In hybrid RF/VLC, data rate maximization is subject to constraints on bandwidth, power and the user association. The joint optimization problem of bandwidth, power and user association to maximize the data rate is non-concave and obtaining an optimal solution is difficult with conventional optimization algorithms. The existing solutions are based on a presumption of at least one optimization variable. In this paper, this issue has been overcome by solving the joint optimization problem in hybrid RF/VLC with a deep Q-network (DQN) learning based algorithm, which has been recognized as an efficient learning based mechanism for optimization. Our system model considers one RF and multiple VLC access points (APs). The idle APs are also incorporated in the system model. The application of DQN learning based algorithm is carried out by finding an optimal policy with the help of an action-value function. As the data sets for the considered system are large, a multi-layered network is used for approximating the action-value function estimator. Finally, a transfer learning based algorithm has been proposed for maximizing the total data rate of the system for the case of a newly entering user equipment (UE) that uses the information of the environment before the arrival of the new UE. Through simulations, it is found that our proposed algorithms can lead to an improvement of more than 10% and 54% in the achievable sum-rate and number of iterations for convergence respectively as compared to that obtained with existing conventional optimization algorithms.

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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.

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Cognitive radio based cooperative spectrum sensing (CSS) is severely affected when some secondary users maliciously attack it. Two attacks regarded as key adversaries to the success of CSS are spectrum sensing data falsification (SSDF) and primary user emulation attack (PUEA). Defending SSDF and PUEAs has received significant attention in research in the past decade globally. This paper performs a state-of-the-art comprehensive survey of the researches on defending SSDF and PUEAs. First, the preliminaries like Hypothesis testing for detecting the primary user and different models of CSS are discussed briefly. Then a categorization of the defence mechanisms for defending both the attacks has been proposed as active and passive. Active mechanisms are suitable for an immediate defence in a limited time span, while passive mechanisms are suitable for flexible CSS systems that are ready to detect the attacks over a period of time and suppress them permanently by bringing changes in their underlying operations. An in-depth tutorial on both the defence mechanisms is provided from the perspectives of the secondary users throughput and the interference to the primary user. Finally, a detailed survey on the open research problems in this area and some possible solutions has been performed. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.