In this paper, we study the secure communication of cognitive energy harvesting relay networks when there exist multiple eavesdroppers who can overhear the message of the second hop, and multiple primary users are present. The data transmission from the secondary source to the secondary destination is assisted by the best decode-and-forward relay, which is selected by means of three relay selection schemes. We study the system security performance by deriving the exact analytical secrecy outage probability. These analytical expressions are then verified by comparison to the results of Monte Carlo simulations. Herein we evaluate and discuss the outage performance of the three schemes under variations in important system parameters: the number and locations of relay nodes, primary user nodes, and eavesdroppers; the transmit power threshold; the energy harvesting efficiency coefficient; the power splitting ratio; and the target secure rate.
Recently, content-centric networking (CCN) has become one of the important technologies for enabling the future networks. Along with its recognized potentialities as a content retrieval and dissemination solution, CCN has been also recently considered as a promising architecture for the Internet of things (IoT), because of 2 main features such as named-based routing and in-network caching.However, IoT is characterized by challenging features: small storage capacity of resource-constrained devices due to cost and limitation of energy and especially transient data that impose stringent requirements on the information freshness.As a consequence, the intrinsic caching mechanisms existing in CCN approach do not well suit IoT domains; hence, providing a specific caching policy at intermediate nodes is a very challenging task. This paper proposes an effective multiattribute in-network caching decision algorithm that performs a caching strategy in CCN-IoT network by considering a set of crucial attributes including the content store size, hop count, particularly key temporal properties like data freshness, and the node energy level. Simulation results proved that our proposed approach outperforms 2 cache management schemes (probabilistic least recently used and AlwaysCache-first in first out in terms of improving total hit rate, reducing data retrieval delay, and enhancing content reusability in IoT environment).
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