Improving physical layer security via cooperative diversity in energy-constrained cognitive radio networks with multiple eavesdroppers

초록

In this paper, a scheme that exploits cooperative diversity of multiple relays to provide physical layer security against an eavesdropping attack is concerned. Relay-based cognitive radio network (CRN) faces issues multiple issues other than the same as faced by conventional wireless communications. If the nodes in a CRN are able to harvest energy and then spend less energy than the total energy available, we can ensure a perpetual lifetime for the network. In this paper, an energy-constrained CRN is considered where relay nodes are able to harvest energy. A cooperative diversity-based relay and subchannel-selection algorithm is proposed, which selects a relay and a subchannel to achieve the maximum secrecy rate while keeping the energy consumed under a certain limit. A transmission power factor is also selected by the algorithm, which ensures long-term operation of the network. The power allocation problem at the selected relay and at the source also satisfies the maximum-interference constraint with the primary user (PU). The proposed scheme is compared with a variant of the proposed scheme where the relays are assumed to have an infinite battery capacity (so maximum transmission power is available in every time slot) and is compared with a scheme that uses jamming for physical layer security. The simulation results show that the infinite battery-capacity scheme outperforms the jamming-based physical layer security scheme, thus validating that cooperative diversity-based schemes are suitable to use when channel conditions are better employed, instead of jamming for physical layer security.

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