Recently, medical image encryption has attracted many researchers because of security issues in the communication process. The recent COVID-19 has highlighted the fact that medical images are consistently created and disseminated online, leading to a need for protection from unauthorised utilisation. This paper intends to review the various medical image encryption approaches along with their merits and limitations. It includes a survey, a brief introduction, and the most utilised interesting applications of image encryption. Then, the contributions of reviewed approaches are summarised and compared regarding different technical perspectives. Lastly, we highlight the recent challenges along with several directions of potential research that could fill the gaps in these domains for researchers and developers.
Summary
The current work investigates the performance of multi‐slot‐based dynamic clustering in a cognitive radio network. For the spectrum sensing, every secondary user utilizes the multi‐slots of sensing time frame and combines the decisions of every multi‐slot, using the OR logic scheme, to get the sub‐local decision. The channel state information of the connections among the secondary users and access points present on the network's access points has been used to cluster the secondary users. To form the clusters, the secondary users with higher quality reporting channels for a specific access point have been chosen. Therefore, the clusters formed, in each iteration, with their respective access points, are dynamic in nature. Every secondary user in a cluster detects the availability of a primary user, makes a decision, and forwards it to its corresponding access point, via the reporting‐channel. Each access point employs the OR rule to merge the decisions of secondary users in the respective clusters, to make a local decision. Finally, the local decisions of all access points have been directed to fusion center, making the final decision about primary user's accessibility. The performance of multi‐slot‐based dynamic clustering has been studied relative to the different parameters, like detection probability, number of clusters, number of multi‐slots, secondary users, and access points. Further, the performance evaluation and comparisons of a multi‐slot‐based cognitive radio network with a single slot, cluster‐based cognitive radio network with non‐clustered, and multi‐slot‐based dynamic cluster with individual multi‐slots as well as dynamic clustering, have been done.
In photonic integrated circuits (PICs), one of the most crucial building blocks is optical waveguide couplers, which are usually utilized in Mach-Zehnder interferometer-based devices, for instance, power monitors, filters, and N-by-N optical switches.Such devices’ responses are needed to be wavelength insensitively for increment the operating bandwidths, particularly more than the C+L band for real-time applications (the wavelength’s spectral range = 1530 - 1630 nm). Hence, an optical waveguide coupler including a precise and broadband is necessary. In the platform of silicon-on-insulator (SOI), the typical directional couplers have containedtwo parallel waveguides and are broadly utilized in PICs due to their compactness and integrability. To achieve effectiveness in broadband optical waveguide coupler, a new design has been proposed in this work. For optimally designing broadband optical waveguide coupler, Social Spider Optimization algorithm is utilized. The proposed approach is implemented in the platform of MATLAB. And the simulated results have shown that the proposed approach has provided a better Optimal Design of Broadband Optical Waveguide Coupler than the existing approach.
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