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

다국어 초록 (Multilingual Abstract)

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.
Power allocation at the selected best relay that exists with multiple eavesdroppers is a nontrivial problem. The best relay selection is also constrained by the maximum transmission power available, so in the selection of best relay and the best subchannel to transmit over, in order to maximize the secrecy rate, the transmission power available has also to be taken into consideration. This paper presents a joint relay‐subchannel selection and power allocation scheme that is able to operate in energy‐constrained CRN.