Research On Secure Information Transmission And Energy Harvesting Technologies In Cognitive SWIPT Network

Due to the broadcast nature of wireless channels,information transmitted directly from transmitter to receiver is likely to be attacked by eavesdropper.In order to defend against eavesdropping attack,traditional encryption technologies are implemented in secure transmission at the expense of computational complexity and transmission delay.Different from traditional encryption technologies,physical layer security(PLS)is regarded as an information encryption technology that guarantees secure communication from the perspective of Shannon information theory.It can fundamentally resolve the eavesdropping problem with the guarantee of secure communication.In cognitive simultaneous wireless information and power transfer(SWIPT)network,cognitive nodes and energy harvesting nodes may become the potential eavesdroppers.Hence,the secure requirements for cognitive SWIPT are higher than traditional cognitive radio network(CRN)and SWIPT network.This dissertation studies the secure information transmission and energy harvesting technologies in cognitive SWIPT network.Several secure communication strategies are proposed in different scenarios.In the proposed strategies,with the introduction of artificial noise(AN)assisted jamming,effects of optimal node selection and beamforming design are joint investigated.The main research aspects are shown as below.Secure communication strategy based on cognitive SWIPT node energy harvesting and destination-assisted jamming in cognitive radio primary network is investigated in Chapter 2.Cognitive user equipped with energy harvesting device implements beamforming technique to assist primary network for secure communication.Cognitive user transmits information in cognitive network via the licensed primary spectrum and the harvested energy.Meanwhile,the AN jamming signal transmitted by primary receiver interferes with the eavesdropper.Simulation results demonstrate that,the proposed strategy allows cognitive users to communicate in the licensed primary spectrum.It enhances primary network secure communication performance dramatically.Furthermore,the communication performance of secondary network can also be guaranteed.Cognitive SWIPT user selection strategy and the corresponding beamforming design method are studied in Chapter 3.The primary network selects a cognitive user to forward the traffic from a primary transmitter to a primary receiver.The selected cognitive user implements beamforming technique to assist primary network for secure communication.The remaining cognitive transmitters harvest energy and transmit information to cognitive receiver through the licensed primary spectrum.Combined with the beamforming design method and destination-assisted jamming signal transmission strategy proposed in Chapter 2,jamming signal transmitted by primary receiver not only confuses eavesdropper,but also is used to power the remaining cognitive users.With the joint design of cognitive user power and beamforming vector,it guarantees physical layer security of primary and secondary network and realize the tradeoff of achievable rates in primary and secondary network.Joint optimization of beamforming and power splitting design scheme in cognitive SWIPT network is proposed in Chapter 4.In cognitive SWIPT decode-and-forward(DF)relay network,relays are supposed to harvest energy from cognitive source via power splitting(PS)protocol and complete cognitive secure information transmission with beamforming.Cognitive destination transmits AN to interfere with eavesdropper,while jamming signal can also provide harvested energy to relays.By the selection of optimal cognitive SWIPT relay,beamforming vector and power splitting ratio can be joint optimized with the objective of secure rate maximization in the proposed scheme.The dissertation solves this non-convex optimization problem via a general two-stage procedure with semi-definite relaxation(SDR)method.Simulation results show that the scheme achieves the maximum secure rate through the appropriate selection of power splitting ratio,which guarantees PLS in cognitive SWIPT networks.This dissertation initially studies secure information transmission and energy harvesting technologies in cognitive SWIPT network.The achievements of research provide significant value for the further related works.